EUROPEAN RUSSIAN FORESTS: their current state and features of their 9789402411713, 9789402411720, 2017957593, 9402411712

Table of contents :
Preface......Page 6
References......Page 9
Contents......Page 11
Contributors......Page 13
1.1 Topography and Hydrography......Page 15
1.2 Climate......Page 20
1.3 General Description of Forest Vegetation......Page 26
1.3.1 Boreal Forest......Page 30
1.3.2 Hemiboreal Forest......Page 32
1.3.3 Nemoral Forest......Page 35
1.4 General Description of Forest Soils......Page 38
References......Page 43
Chapter 2: Methods of Investigation......Page 47
2.1 Study Areas......Page 48
2.2 Forest Typology Used (Classification of Forest Vegetation)......Page 49
2.3 Mapping and Monitoring of Forest Cover......Page 53
2.4 Field Data Collection......Page 56
2.5 Data Analysis......Page 57
2.5.2 Plant Diversity Assessment......Page 58
2.5.3 Assessment of Forest Vegetation Dynamics According to the Ontogenetic Structure of Tree Populations......Page 59
2.5.4 Assessment of Successional Stages of Forest Ecosystems......Page 63
References......Page 65
Chapter 3: Boreal Forests......Page 72
3.1.1 Section: Lichen Forests......Page 73
3.1.2 Section: Green Moss Forests......Page 78
3.1.3 Section: Large Fern Forests......Page 84
3.1.4 Section: Boreal Tall Herb Forests......Page 85
3.1.5 Section: Boreal Swamp Forests......Page 88
3.1.6 Section: Sphagnum Forests......Page 93
3.1.7 Conclusion......Page 99
3.2 Features of the Historical Land Use in the Boreal Region......Page 100
3.2.1 Slash-and-Burn Agriculture......Page 101
3.2.2 Tillage Agriculture......Page 104
3.2.3 Traditional Cattle and Reindeer Breeding......Page 105
3.2.4 Fires......Page 106
3.2.5 Felling (Cutting)......Page 108
3.2.6 Conclusion......Page 112
3.3 Succession of the Boreal Forest After Fire in the Kostomuksha State Nature Reserve (Karelia)......Page 113
3.3.2 Post-Fire Vegetation Within the Denudation-Tectonic Landscape......Page 114
3.3.3 Succession After Fire in the Lowland Outwash Terrains......Page 121
3.4 Old-Growth Dark Coniferous Forests in the Pechora-­Ilych Nature Reserve......Page 129
3.4.1 General Description of the Pechora-Ilych State Nature Reserve......Page 130
3.4.2 The Study Area (Bolshaya Porozhnaya River Basin)......Page 132
3.4.3 Methods of Investigation......Page 133
3.4.4 General Description of the Studied Forests......Page 137
3.4.5 Composition and Structure of Tree Populations in Different Forest Types......Page 148
3.4.6 Species and Structural Diversity of the Vegetation in Microsites Developed in the Boreal Tall Herb Spruce-­Fir Forests......Page 156
3.4.7 Phytomass of Vascular and Moss Species in Microsites Developed in the Boreal Tall Herb Spruce-Fir Forests......Page 160
3.4.8 Conclusion......Page 162
3.5.1 The Study Areas......Page 164
3.5.3 Vegetation and Soil in the Studied Forest Types......Page 166
3.5.4 Conclusion......Page 196
3.6 Conclusions on the Boreal Forest Region......Page 199
References......Page 203
Chapter 4: Hemiboreal Forests......Page 217
4.1.1 Section: Lichen Forests......Page 218
4.1.2 Section: Green Moss Forests......Page 220
4.1.3 Section: Herb Forests......Page 226
4.1.4 Section: Hemiboreal Swamp Forests......Page 242
4.1.5 Section: Sphagnum Forests......Page 248
4.1.6 Conclusion......Page 253
4.2 Features of the Historical Land-Use in the Hemiboreal Region......Page 254
4.3 Typical Features of the Best Preserved Hemiboreal Forests in European Russia (on Examples of the Visimskiy and Sabarskiy Reserves and the Kilemarskiy Zakaznik)......Page 266
4.3.1 Vascular Plant Diversity in the Tall Herb Dark-­Coniferous – Broad-Leaved Forests......Page 268
4.3.2 Ontogenetic Structure of Tree Populations and Patchy Structure of Tall Herb Dark-Coniferous – Broad-Leaved Forests......Page 272
4.3.3 Microsite Structure and Vegetation Diversity in the Tall Herb Dark-Coniferous – Broad-Leaved Forests......Page 279
4.3.4 Features of the Deadwood Decomposition......Page 285
4.3.5 Conclusion......Page 290
4.4.1 General Description of the Study Area......Page 291
4.4.2 Succession Series......Page 293
4.4.3 Conclusion......Page 301
4.5 Plant Diversity and Successional Stages of Forests After Cutting and Ploughing in the Southern Moscow Region......Page 303
4.5.1 Land-use History of the Region......Page 304
4.5.2 General Description and Species Diversity of the Vegetation Communities......Page 305
4.5.3 Structure of the Tree and Shrub Populations in Different Forest Types......Page 311
4.5.3.1 Querceto-Tilieta Nemorosa......Page 312
4.5.3.2 Betuleta Nemorosa......Page 315
4.5.3.3 Betuleta Prato-Nemoroherbosa......Page 317
4.5.3.4 Pineta Nemorosa......Page 321
4.5.4 Forecasts of the Development of Island Forest Tracts......Page 322
4.5.5 Experience in Restoration of Broad-Leaved Forest with Picea abies......Page 324
4.5.6 Conclusion......Page 326
4.6 Conclusions on the Hemiboreal Forest Region......Page 327
References......Page 329
Chapter 5: Nemoral Forests......Page 345
5.1 Prodromus of the Vegetation and Forest Distribution in the Nemoral Region......Page 346
5.1.2 Section: Green Moss Forests......Page 347
5.1.3 Section: Herb Forests......Page 349
5.1.4 Section: Nemoral Swamp Forests......Page 370
5.1.5 Section: Sphagnum Forests......Page 371
5.2 Features of the Historical Land Use in the Nemoral Region......Page 372
5.2.1 Conclusion......Page 382
5.3.1 History of the Reserve Area......Page 383
5.3.2 Methods of Investigation......Page 388
5.3.3 General Description of the Vegetation......Page 389
5.3.4 Plant Diversity Assessment......Page 410
5.3.5 Forest Recovery on Abandoned Agricultural Lands......Page 414
5.3.6 Conclusion......Page 421
5.4 Eighty Years of Vegetation Dynamics in the Voronezh State Nature Reserve......Page 422
5.4.1 Methods of Investigation......Page 426
5.4.2 General Description of the Vegetation......Page 427
5.4.3 Eighty Years of Vegetation Dynamics......Page 450
5.4.4 Conclusion......Page 456
5.5.1 General Description of the Nerussa-Desna Polesie......Page 457
5.5.2 Study Area and Methods of Investigation......Page 459
5.5.3 Succession in Pinus sylvestris Forests at the Tops of the Ridges......Page 460
5.5.4 Succession in Pinus sylvestris Forests on the Slopes of the Ridges......Page 470
5.5.5 Conclusion......Page 472
5.6 Conclusion on the Nemoral Forest Region......Page 474
References......Page 477
Chapter 6: Floodplains......Page 489
6.1.1.1 Hygrophilous Herb Willow Forests......Page 491
6.1.3.1 Nitrophilous–Boreal Tall Herb Spruce(–Fir) Forests......Page 493
6.1.4.1 Hygrophilous Tall Herb Grey Alder Forests......Page 495
6.1.5 Long Inundated Old Parts of Floodplains in the Boreal Forest Region......Page 496
6.1.5.1 Hygrophilous-Nitrophilous Tall Herb Spruce (-Fir) Forests......Page 497
6.2 Nemoral Floodplains......Page 498
6.2.1.1 Nitrophilous Tall Herb Willow-Poplar Forests......Page 499
6.2.2.1 Hygrophilous Tall Herb Willow–Poplar Forests......Page 500
6.2.3.1 Nemoral Herb Broad-Leaved Forests......Page 501
6.2.3.2 Boreal-Nemoral Herb Broad-Leaved Spruce (-Fir) Forests......Page 502
6.2.4.1 Nemoral-Nitrophilous Herb Broad-Leaved Forests......Page 503
6.2.5.1 Hygrophilous-Nitrophilous Tall Herb Black Alder Forests......Page 505
6.3.1.1 Nitrophilous Tall Herb Willow-Poplar Forests......Page 508
6.3.3.1 Meadow Herb Broad-Leaved Forests......Page 510
6.3.4.2 Nitrophilous Tall Herb Black Alder Forests......Page 513
6.4.1.1 Hygrophilous-Nitrophilous Tall Herb Willow Forests......Page 514
6.5 Conclusion......Page 515
References......Page 516
Chapter 7: Forest Cover Dynamics at the End of the Twentieth and the Beginning of the Twenty-First Centuries......Page 520
References......Page 523
Chapter 8: Development of the European Russian Forests in the Holocene......Page 525
8.1 Conclusion......Page 538
References......Page 541
General Index......Page 547
Index of Plant Communities......Page 554
Index of Plant Names......Page 561

Citation preview

Plant and Vegetation 15

Olga V. Smirnova Maxim V. Bobrovsky Larisa G. Khanina Editors

European Russian Forests

Their Current State and Features of Their History

Plant and Vegetation Volume 15

Series editor M.J.A. Werger, Utrecht, The Netherlands

Plant and Vegetation is a new Springer series comprising a series of books that present current knowledge and new perspectives on world vegetation. Examining the ecology of plants and vegetation at all scales – from plant to landscape – and covering key issues such as globalization, invasive species, climate change and the dynamics of plant biodiversity, this book series draws together a wide range of material of interest to plant ecologists, vegetation scientists, and geographers around the world. The series provides a valuable resource for both graduate students and researchers in environmental and biological sciences, as well as for landscape planners and policy makers involved in land-use and restoration projects at local, regional and international levels. More information about this series at http://www.springer.com/series/7549

Olga V. Smirnova  •  Maxim V. Bobrovsky Larisa G. Khanina Editors

European Russian Forests Their Current State and Features of Their History

Editors Olga V. Smirnova Center for Forest Ecology and Productivity Russian Academy of Sciences Moscow, Russia Larisa G. Khanina Institute of Mathematical Problems of Biology RAS - Branch of the M.V. Keldysh Institute of Applied Mathematics Russian Academy of Sciences Pushchino, Russia

Maxim V. Bobrovsky Institute of Physico-Chemical and Biological Problems in Soil Science Russian Academy of Sciences Pushchino, Russia

ISSN 1875-1318     ISSN 1875-1326 (electronic) Plant and Vegetation ISBN 978-94-024-1171-3    ISBN 978-94-024-1172-0 (eBook) https://doi.org/10.1007/978-94-024-1172-0 Library of Congress Control Number: 2017957593 © Springer Science+Business Media B.V., part of Springer Nature 2017 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer Science+Business Media B.V. The registered company address is: Van Godewijckstraat 30, 3311 GX Dordrecht, The Netherlands

Preface

Forests are fundamental to human well-being and survival. They provide timber, food, fuel and habitats for forest biodiversity, and they have great positive effects on the cycling of carbon, water and nutrients; forests improve soil fertility, optimize hydrological regimes of terrestrial ecosystems, alleviate the consequences of climate changes and where forests cover extensive areas they define the climatic or meteorological features in the region. Forests are actively used by humans across the globe, and many people are economically dependent on forests. Also, in European Russia, human economic activity has been an important factor in the dynamics of forest ecosystems for a long time. Nevertheless, in the Russian Plain and surrounding areas, forests presently occupy more than 1,700,000 km2 (Bartalev et al. 2004) and that is half of the total forested area in Europe (Report... 2015). Besides the fact that they cover a huge area, an important feature of the forests of European Russia is their free development, i.e. the absence of intensive forest management and the absence of tree planting after cutting in most of the area. The forests that were less actively exploited in the past presently form nature reserves and national parks with a total area of about 90,000 km2 in the Russian Plain and adjacent areas (National parks of Russia 2017; Zapovednik 2017). We believe that these peculiarities make the European Russian forests of global importance. Their ecosystems function in more natural and undisturbed ways than ecosystems under more intensive forest management and thus provide unique opportunities for research. Furthermore, the European Russian old-­ growth uneven-aged forests can be considered as rather good reference objects for reconstructions of the East-European forest cover in the late Holocene. Detailed study of these forests could help (i) to make clear how those ecosystems of ancient forests with a complicated structure and composition functioned, (ii) to predict how ecosystems will function nowadays under a changing climate and under forest management scenarios that include natural or anthropogenic catastrophic events and (iii) to formulate a structure of forest cover that might properly perform all ecosystem functions and permanently maintain high levels of forest biodiversity, of soil fertility and of forest productivity.

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Describing the European Russian forests in our book, we tried to highlight the following key points: (1) the history of the forests at regional and local scales, (2) their diversity of plant communities and plant species and (3) the successional status of the forest plant communities and the ontogenetic structures of their tree populations. The latter is based on the concept of a discrete description of the ontogeny of plant species as proposed by Professor T. Rabotnov (1950, 1978) and developed by Professor A.  Uranov and his numerous followers (Uranov 1975; Serebryakova 1976, 1977, 1988; Gatzuk et al. 1980; Smirnova 1987; etc.). We would like to note that on the basis of the concept of a discrete description of the ontogeny of plant species, the concept of the population-ontogenetical organization of plant communities has been further developed and widely used in forest community investigations (Smirnova et  al. 1988, 1989, 1990, 1991, 2000, etc.). Applications of these concepts, together with the gap theory in forest dynamics (Aubréville 1938; Yamamoto 1992), the mosaic-cycle concept (Remmert 1991), the theories of disturbances (White 1979; Pickett and White 1985), key species (Smirnova 1998) and ecosystem engineers (Jones et al. 1994), led us to develop a notion of a potential forest landscape in which regional biota can be sustainably maintained (Smirnova et al. 2001, 2015; Smirnova and Toropova 2008, 2016). We tried to keep in mind the idea to study a forest landscape instead of a forest community during all our investigations. Our results of years of research on the European Russian forests conducted by a large informal team have been summarized in several books published in Russian (Smirnova 1994, 2004; Smirnova and Shaposhnikov 1999; Zaugolnova 2000). The book you hold in your hands is an attempt to summarize in English our knowledge and experience, the results of our research in European Russian forests. This book is based on long-term investigations of the current vegetation and soil, identifying and analysing forest tracts which were least disturbed by man and on studying forest history at local and regional scales. As a result, we have offered successional series of plant communities formed after typical anthropogenic impacts in different climatic regions and have developed a hypothesis about the potential forest landscapes and the main causes of their transformations. Our book is dedicated to our colleague and our friend Professor Ludmila B. Zaugolnova, who organized and actively participated in so many of the investigations which resulted in this book. She was the first among the students of Professor A. Uranov who studied the ontogeny and population structure of tree species (in her case, it was Fraxinus excelsior) (Zaugolnova 1969); she developed the concept of the basic ontogenetic spectrum of a population and some other theoretical ideas, which improved investigations of plant populations and communities (Zaugolnova 1994). Ludmila Zaugolnova was a pioneer in the application of quantitative methods in the analysis of phytosociological data in Russia (Zaugolnova et al. 1995); she proposed the structure and was an administrator of the first Russian database on phytosociology (Zaugolnova and Khanina 1996; Zaugolnova 2014). She initiated and developed with colleagues the system of ecological-coenotic groups of plant species (Zaugolnova 2000; Smirnova et al. 2004), which is widely applied in this book. And Ludmila proposed and developed with colleagues the Coenofond of the

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European Russian Forests (for the boreal and hemiboreal forest regions) on basis of published and original phytosociological data (Zaugolnova and Morozova 2012; Zaugolnova and Martynenko 2014). Thanks to her sociable, benevolent and sympathetic nature, Ludmila always found volunteers for her labor-intensive work. All the colleagues who collaborated with her remember with gratitude this communication and the impact on their work and life that she had.

Professor Ludmila B. Zaugolnova (1936–2014)

We would like to express our sincere gratitude to Professor Marinus Werger, the editor-in-chief of the Plant and Vegetation series of Springer Publishers. It was his idea to write a book about the forests of European Russia, and since 2011 he had led us through all the hurdles of the writing process, encouraging us at every opportunity. Considerate, patient and benevolent, he selflessly sacrificed his time, correcting our manuscripts and making them readable. Let us just say that without his help and support, the book would not have appeared. Thank you very much for your complex and invaluable work, dear Marinus! We would like to thank everybody who helped us to sample data and to study European Russian forests: our colleagues from different institutions; volunteers from our numerous field trips; students from Moscow, Pushchino, Yoshkar-Ola, Penza and other universities and leaders and staff of nature reserves and national parks where our investigations have been carried on. Our work was mainly supported by the Russian Academy of Sciences, numerous grants of the Russian Foundation for Basic Research (Nos. 13-04-01491, 13-04-­ 02181, 14-34-50640, 15-29-02724, 15-34-20967, 16-04-00395, etc.) and the Program of the Presidium of the Russian Academy of Sciences ‘Biodiversity’. Pushchino, Russia Moscow, Russia April 2017

Olga V. Smirnova Maxim V. Bobrovsky Larisa G. Khanina

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References Aubréville A (1938) La forêt coloniale: Les forêts de l'Afrique occidentale française. Ann Acad Sci Colon 9. Paris, 244 pp Bartalev SA, Ershov DV, Isaev AS, Potapov PV, Turubanova SA, Yaroshenko AYu (2004) Russia’s forests: dominating forest types and their canopy density. Scale 1:14,000,000. Space Research Institute of the RAS, Center for Forest Ecology and Productivity of the RAS, Global Forest Watch and Greenpeace Russia, Moscow Gatzuk LE, Smirnova OV, Vorontsova LI, Zaugolnova LB, Zhukova LA (1980) Age state of plants of various growth forms: a review. J Ecol 68:675–696 Jones CG, Lawton JH, Shachak M (1994) Organisms as ecosystem engineers. Oikos 69:373–386 National parks of Russia (2017) URL: https://en.wikipedia.org/wiki/National_parks_of_Russia Pickett STA, White PS (eds) (1985) The ecology of natural disturbance and patch dynamics. Academic Press, Orlando Rabotnov TA (1950) Zhiznennye tsikly mnogoletnikh travyanistykh rasteniy v lugovykh tsenozakh. Trudy Botanicheskogo instituta AN SSSR 3:7–204 – The life cycles of perennial herbaceous plants in meadow communities Rabotnov TA (1978) On coenopopulations of plants reproducing by seeds. In: Freysen AHJ, Woldendorp JW (eds) Structure and functioning of plant population. Amsterdam, pp 1–26 Remmert H (ed) (1991) The mosaic-cycle concept of ecosystems. Ecological studies 85. Springer, 168 pp Report on the mid-term evaluation of the goals for European forests and the European 2020 targets for forests (2015) Published by Ministerial conference on the protection of forests in Europe. Madrid, Spain. URL: http://foresteurope.org/wp-content/uploads/2016/08/MID-TERMEvaluatG2020T-2015.pdf Serebryakova TI (ed) (1976) Cenopopulyatsii rasteniy (osnovnye ponyatiya i struktura). Izd-vo Nauka, Moscow, 216 pp – Coenopopulations of plants: the main terms and structure Serebryakova TI (ed) (1977) Cenopopulyatsii rasteniy. Razvitie i vzaimootnosheniya. Izd-vo Nauka, Moscow, 134 pp – Coenopopulations of plants. Development and relationships Serebryakova TI (ed) (1988) Cenopopulyatsii rasteniy (ocherki populyatsionnoy biologii). Izd-vo Nauka, Moscow, 183 pp – Coenopopulation of plants. Essays on population biology Smirnova OV (ed) (1994) Vostochnoevropeyskie shirokolistvennye lesa. Izd-vo Nauka, Moscow, 363 pp – East-European broad-leaved forests Smirnova OV (1998) Populyatsionnaya organizatsiya biocenoticheskogo pokrova lesnykh landshaftov. Uspekhi sovremennoy biologii 118(2):148–165 – Population organization of ecosystems in forest landscapes Smirnova OV (ed) (2004) Vostochnoevropeyskie lesa: istoriya v golocene i sovremennost. Izd-vo Nauka, Moscow, Vol. 1, 479 pp. Vol. 2, 575 pp – East-European forests: the Holocene history and the current state Smirnova OV, Shaposhnikov ES (eds) (1999) Successionnye processy v zapovednikakh Rossii i problemy sokhraneniya biologicheskogo rasnoobraziya. Russkoe botanicheskoe obshchestvo, SPb, 549 pp – Successions in the Russian Nature reserves and the challenge of biodiversity conservation Smirnova OV, Toropova NA (2008) Suktsessiya i klimaks kak ekosistemnyi process. Uspekhi sovremennoy biologii 128(2):129–144 – Succession and climax as an ecosystem process Smirnova OV, Toropova NA (2016) Potential ecosystem cover – a new approach to conservation biology. Russian journal of ecosystem ecology 1(1). DOI: 10.21685/2500-0578-2016-1-1 Smirnova OV, Popadyuk RV, Chistyakova AA (1988) Populyatsionnye metody opredeleniya minimalnoy ploshchadi lesnogo tsenoza. Botanichesky zhurnal 73(10):1423–1433  – Population methods for determining the minimum area of a forest coenosis Smirnova OV, Chistakova AA, Popadyuk RV (1989) Populyatsionnye mekhanizmy dinamiki lesnykh tsenozov. Biologicheskie nauki 11:48–58  – Population mechanisms of dynamics of forest coenoses

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Smirnova OV, Chistyakova AA, Popadyuk RV, Evstigneev OI, Korotkov VN, Mitrofanova MV, Ponomarenko EV (1990) Populyatsionnaya organizatsiya rastitelnogo pokrova lesnykh territoriy (na primere shirokolistvennykh lesov Evropeyskoy chasti SSSR). Izd-vo ONTI NTsBI, Pushchino, 92 pp – Population organization of the vegetation cover in forested areas (with an example of broad-­leaved forests in the European part of the USSR) Smirnova OV, Voznyak RR, Evstigneev OI, Korotkov VN, Nosach NYa, Popadyuk RV, Samoylenko VK, Toropova NA (1991) Populyatsionnaya diagnostika i prognozy razvitiya zapovednykh lesnykh massivov (na primere Kanevskogo zapovednika). Botanichesky zhurnal 76(6):68–79 – Population diagnostics and forecasts for the development of protected forest areas (with the example of the Kanev State Nature Reserve, Ukraine) Smirnova OV, Zaugolnova LB, Istomina II, Khanina LG (2000) Population mosaic cycles in forest ecosystems. In: Proceedings IAVS symposium. IAVS, Opulus Press, Uppsala, pp 108–112 Smirnova OV, Turubanova SA, Bobrovsky MV, Korotkov VN, Khanina LG (2001) Rekonstruktsiya istorii lesnogo poyasa Vostochnoy Evropy i problema podderzhaniya biologicheskogo raznoobraziya. Uspekhi sovremennoy biologii 2:144–159 – Reconstruction of the history of the forest belt in Eastern Europe and the challenge of maintenance of biological diversity Smirnova OV, Lugovaya DL, Prokazina TS (2013) Model reconstruction of restored taiga forest cover. Biology Bulletin Reviews 3(6):493–504 Uranov AA (1975) Vozrastnoy spektr tsenopopulyatsiy kak funktsiya vremeni i energeticheskikh volnovykh processov. Biologicheskie nauki 2:7–34 – Age spectrum of phytocoenopopulations as a function of time and energy wave processes White PS (1979) Pattern, process, and natural disturbance in vegetation. Bot. Rev. 45(3):229–299 Yamamoto SI (1992) The gap theory in forest dynamics. Bot. Mag. Tokyo 105:375–383 Zapovednik (2017) URL: https://en.wikipedia.org/wiki/Zapovednik Zaugolnova LB (1969) Ontogenez i vozrastnye spektry populyatsiy yasenya obyknovennogo v fitotsenozakh lesnoy i lesostepnoy zony. Dissertation (Candidate of sciences) in biology. Moskovskiy pedagogicheskiy gosudarstvennyi universitet, Moscow – Ontogeny and age spectra of Fraxinus excelsior populations in phytocoenoses of forest and forest-steppe regions Zaugolnova LB (1994) Struktura populyatsiy semennykh rasteniy i problemy ikh monitoringa. Dissertation (Doctor of sciences) in biology. Sankt-Peterburgskiy gosudarstvennyi universitet, SPb, 70 pp – Structure of seed plant populations and their monitoring Zaugolnova LB (ed) (2000) Otsenka i sokhranenie bioraznoobraziya lesnogo pokrova v zapovednikakh Evropeyskoy Rossii. Izd-vo Nauchnyi Mir, Moscow – Assessment and conservation of forest biodiversity in the European Russian reserves Zaugolnova LB, Khanina LG (1996) Opyt razrabotki i ispolzovaniya baz dannykh v lesnoy fitotsenologii. Lesovedenie 1: 76–83 – Experience in the development and application of databases in forest phytocoenology Zaugolnova LB, Martynenko VB (2014) Opredelitel tipov lesa Evropeyskoy Rossii. URL: http:// www.cepl.rssi.ru/bio/forest/index.htm – Guide to the forest types in European Russia Zaugolnova LB, Morozova OV (2012) Coenofond lesov Evropeiskoy Rossii. URL: http://www. cepl.rssi.ru/bio/flora/index.htm – Coenofond of forests in European Russia Zaugolnova LB, Khanina LG, Komarov AS, Smirnova OV, Popadyuk RV, Ostrovsky MA, Zubkova EV, Glukhova EM, Palenova MM, Gubanov VS, Grabarnik PYa (1995) Informatsionnoanaliticheskaya sistema dlya otsenki suktsessionnogo sostoyaniya lesnykh soobshchestv. ONTI PNTs RAN, Pushchino, 51  pp  – Computer information and analytical system for assessing the succession stages in forest communities Zaugolnova LB, Khanina LG, Braslavskaya TYu, Bakun EYu, Glukhova EM, Bobrovsky MV, Shovkun MM, Smirnova OV, Lugovaya DL, Yanitskaya TO (2014) Lesnaya rastitelnost Severnoy Evrazii. Svidetelstvo o gosudarstvennoy registratsii bazy dannykh No 2014620258 v Reestre baz dannykh – Forest vegetation of Northern Eurasia. Certificate of State Registration of the Database No. 2014620258 in the Database Registry

Contents

1 Natural Conditions and General Descriptions of Forest Vegetation and Forest Soils....................................................... 1 O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, I.S. Voskresensky, N.V. Zukert, S.S. Bykhovets, L.B. Zaugolnova, and S.A. Turubanova 2 Methods of Investigation........................................................................... 33 O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, L.B. Zaugolnova, S.A. Turubanova, P.V. Potapov, A.Yu. Yaroshenko, and V.E. Smirnov 3 Boreal Forests............................................................................................. 59 O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, L.B. Zaugolnova, V.N. Korotkov, A.A. Aleynikov, O.I. Evstigneev, V.E. Smirnov, N.S. Smirnov, and M.V. Zaprudina 4 Hemiboreal Forests.................................................................................... 205 O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, L.B. Zaugolnova, A.I. Shirokov, D.L. Lugovaya, V.N. Korotkov, V.A. Spirin, T.Yu. Samokhina, and M.V. Zaprudina 5 Nemoral Forests......................................................................................... 333 O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, T.Yu. Braslavskaya, E.A. Starodubtseva, O.I. Evstigneev, V.N. Korotkov, V.E. Smirnov, and N.V. Ivanova

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6 Floodplains................................................................................................. 477 T.Yu. Braslavskaya 7 Forest Cover Dynamics at the End of the Twentieth and the Beginning of the Twenty-First Centuries................................... 509 P.V. Potapov, S.A. Turubanova, A.Yu. Tyukavina, and A.M. Krylov 8 Development of the European Russian Forests in the Holocene........................................................................................... 515 O.V. Smirnova, V.N. Kalyakin, S.A. Turubanova, M.V. Bobrovsky, and L.G. Khanina General Index................................................................................................... 537 Index of Plant Communities........................................................................... 545 Index of Plant Names....................................................................................... 553

Contributors

A.A.  Aleynikov  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia M.V. Bobrovsky  Institute of Physico-Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences, Pushchino, Moscow region, Russia T.Yu.  Braslavskaya  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia S.S.  Bykhovets  Institute of Physico-Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences, Pushchino, Moscow region, Russia O.I. Evstigneev  Bryanskiy Les (Bryansk Forest) State Nature Biosphere Reserve, Nerussa, Bryansk region, Russia N.V. Ivanova  Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia V.N. Kalyakin  Zoological Museum, M.V. Lomonosov Moscow State University, Moscow, Russia L.G. Khanina  Institute of Mathematical Problems of Biology RAS – Branch of the M.V.  Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia V.N.  Korotkov  Faculty of Biology, M.V.  Lomonosov Moscow State University, Moscow, Russia A.M.  Krylov  Department of Geographical Science, University of Maryland, College Park, MD, USA D.L.  Lugovaya  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia WWF Russia, Moscow, Russia xiii

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Contributors

P.V.  Potapov  Department of Geographical Science, University of Maryland, College Park, MD, USA T.Yu.  Samokhina  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia A.I.  Shirokov  Botanical Garden, N.I.  Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia N.S.  Smirnov  Pechora-Ilych State Nature Biosphere Reserve, Yaksha, Komi Republic, Russia Institute of Global Climate and Ecology of Roshydromet and the Russian Academy of Sciences, Moscow, Russia V.E. Smirnov  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia O.V.  Smirnova  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia V.A. Spirin  Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland Natural History Museum, University of Oslo, Oslo, Norway E.A. Starodubtseva  Voronezh State Nature Biosphere Reserve, Voronezh, Russia A.Yu. Tyukavina  Department of Geographical Science, University of Maryland, College Park, MD, USA S.A. Turubanova  Department of Geographical Science, University of Maryland, College Park, MD, USA I.S.  Voskresensky  Faculty of Geography, M.V.  Lomonosov Moscow State University, Moscow, Russia A.Yu. Yaroshenko  Greenpeace Russia, Moscow, Russia L.B.  Zaugolnova  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia M.V.  Zaprudina  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia N.V. Zukert  Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia

Chapter 1

Natural Conditions and General Descriptions of Forest Vegetation and Forest Soils O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, I.S. Voskresensky, N.V. Zukert, S.S. Bykhovets, L.B. Zaugolnova, and S.A. Turubanova Abstract This chapter contains descriptions of topography and hydrography of the Russian Plain and surrounding areas including Eastern Karelia, the Kola Peninsula and the Northern, the Central and the Southern Russian provinces together with the western slope of the Ural Mountains. The main climatic parameters distributed over the study area and average changes in climate during the last century are also discussed. Forest vegetation and forest soils are surveyed for the boreal, the hemiboreal and the nemoral forest regions.

1.1  Topography and Hydrography The European part of Russia is mainly situated within the bounds of the East European Plain (also known as the Russian Plain): the mountain ridges on the Kola Peninsula, the northern slope of the Great Caucasus range of the Caucasus Mountains

O.V. Smirnova (*) • N.V. Zukert • L.B. Zaugolnova Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia e-mail: [email protected] M.V. Bobrovsky (*) • S.S. Bykhovets (*) Institute of Physico-Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected]; [email protected] L.G. Khanina (*) Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] I.S. Voskresensky (*) Faculty of Geography, M.V. Lomonosov Moscow State University, Moscow, Russia e-mail: [email protected] S.A. Turubanova Department of Geographical Science, University of Maryland, College Park, MD, USA © Springer Science+Business Media B.V., part of Springer Nature 2017 O.V. Smirnova et al. (eds.), European Russian Forests, Plant and Vegetation 15, https://doi.org/10.1007/978-94-024-1172-0_1

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Fig. 1.1  Geographic map of the European part of the Russian Federation (Here and elsewhere in the book the administrative boundaries in the maps are as they were at January 1, 2014)

and the western slope of the Ural Mountains fringe of this Plain (Fig. 1.1). It extends from the Barents Sea (Arctic Ocean) in the north (70°N) for about 3000 km to the Greater Caucasus in the south (42–45°N) (Spiridonov 1978; Voskresensky et  al. 1980). The area of European Russia within these limits comprises roughly 3,960,000  km2 and makes up 40% of Europe (http://en.wikipedia.org/wiki/ European_Russia).

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The area described can be divided into the following geomorphological provinces (Borsuk et al. 2006; Borsuk and Voskresensky 2006): the plains and ridges of East Karelia and the Kola Peninsula; the Northern Russian, the Central Russian and the Southern Russian Provinces; the northern slope of the Great Caucasus; and the western slope of the Ural Mountains. Forests occur in the entire area except the Southern Russian Province. East Karelia and the Kola Peninsula are a part of Fennoscandia situated on the eastern part of the Baltic Crystalline Shield. It is dominated by a relief of denudations and tectonic hills and ridges, including low-mountain areas. The Khibiny Massif, the Lovozero Massif and other hills form the mountain ridges of the Kola Peninsula, which rise up to 500–1100 m above sea level (Khibiny Tundra, 1191 m asl); their relative height is 300–700 m above the surrounding undulating plains. Karelia is a low, ice-scraped plateau with a maximum elevation of 578 m, but most of it lies below 200 m; low ridges and knolls alternate with lakes and marshfilled hollows. Middle-sized and small lakes are widespread over the entire area. Lakes, including the large Ladoga and Onega lakes in the south of the province, characterize the uniqueness of the area. Large hills and lowlands correspond to the tectonic megastructures formed by the very ancient Archean and Proterozoic rocks of the Baltic Shield (Spiridonov 1978). Most of the landforms are glacial. There are exarational (glacial valleys, striations, corries, sheepbacks) and depositional (moraines, eskers, kames, drumlins, outwash fans) landforms. Fragments of the ancient landforms remain in the central part of the Kola Peninsula: there are peneplains with eluvial horizons and buried ancient valleys with alluvia. In the north of the Russian Plain (the Northern Russian Province), lowlands alternate with undulating plains in the basins of the Northern Dvina, Pechora and Mezen rivers (Borsuk and Voskresensky 2006; Borsuk et al. 2006). The Pechora and Mezen river basins are separated by the Timan Ridge, which rises up to 300–471 m asl in a roughly north-south direction. There are minor elevations up to 100  m between river valleys and watersheds. Hills, moraine ridges, eskers, kames, terraces and zanders are common there. They were formed mainly in the Late Pleistocene by glaciers and streams of melted glacier water and in lacustrine-glacial basins. Glacial landforms in the basins of the Northern Dvina, Pechora and Mezen rivers were formed by tongues of ice sheets extended from the centres of glaciation: from South Karelia and the Kola Peninsula to the south-east and from the Ural Mountains to the south-west (Lavrov and Potapenko 2005). In addition a border of the youngest Upper Pleistocene glaciers passed from the Valdai Hills to the Middle Timan Ridge and then to the Nether-Polar Ural. The southern border of the Middle Pleistocene glaciation coincided with the main watershed of the Russian Plain; it extends along the Smolensk-Moscow, the Galich and the Severnye Uvaly uplands, from the source of Dnieper River to the sources of Kama and Pechora rivers. There are karstic ­landforms, such as caves and sinkholes, in the areas with limestone and dolomite, which are located in the Valdai Hills, in the uplands near Ladoga and Onega lakes, and between rivers in the lower Northern Dvina and Mezen river areas. Long uplands and extensive lowlands are situated in the central and southern parts of the Russian Plain (the Central Russian Province) (Voskresensky et al. 1980):

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the Central Russian Upland (293 m asl), the Volga Upland (351 m) and the Bugulma-­ Belebey Upland (479 m) and between these the Oka-Don Plain and the Middle Volga lowlands (60–160 m). The relief of the central part of the Russian Plain was formed by glaciers and rivers (“glacial outwash plain”). The northern part of the area was covered by glaciers during the Middle Pleistocene and the beginning of the Late Pleistocene. The most ancient glaciers in the Early Pleistocene reached 50°N in the basins of the Don and Dnieper rivers (Spiridonov 1978). Lowlands in the basins of the Volga, Kama, Oka and other rivers accumulated aqueous and lacustrine-­glacial deposits, and the “Polesie” relief was formed there. During the postglacial, the glacial landscape was transformed by the formation of river valleys and by other fluvial erosion processes. Fragments of the buried Neogene valleys are preserved under a cover of unconsolidated sediments ranging from a few meters to a few 100  m in thickness. In the south of the province, the area between the Upper Oka and Upper Don rivers was not covered by glaciers, and loess and loess-type rocks were formed there. In the Central Russian Upland, there are karstic caves and sinkholes with disappearing lakes confined to carbonate rock outcrops (Spiridonov 1978). The Southern Russian Province includes the Stavropol Upland with a homoclinal bedding of rocks (830 m asl), a group of isolated mountains (Beshtau, 1401 m, and others), deltaic flats of the Terek and Sulak rivers in the Caspian Depression and the terraced alluvial flats of the lower Kuban River (Borsuk et al. 2006; Borsuk and Voskresensky 2006). The Western Slope of the Ural Mountains comprises a strip of undulating lands and flat hills that extends southwards for 1300 km (Borsuk et al. 2006; Borsuk and Voskresensky 2006). The ranges and ridges rise up to 400–900 m asl and form a stepped plateau with a width of 80–100  km, which is incised by river valleys. Tributaries of the Kama and Pechora rivers form valleys of 200–600 m in depth relative to the plateau. In the north, in the Pechora River basin, “Parm” relief dominates, which consists of mountains with flat tops, over which rise solitary peaks and ridges composed of solid rock. The mountain ranges are separated by depressions elongated in a southerly direction. On the western slope of the Ural Mountains, karstic landforms occur within the areas with Paleozoic carbonate rock (Spiridonov 1978; Borsuk et al. 2006). The hydrographic network of the Russian Plain and surrounding areas is formed by rivers, lakes, marshes and reservoirs (Marchenko et al. 2006). The Rivers of the northern part of the Russian Plain, such as the Northern Dvina (length 1318 km, drainage area 367,000 km2), Pechora (1809 km, 322,000 km2), Mezen and Onega rivers, flow to the Arctic Ocean. In the west of the Russian Plain, the Western Dvina, Neva, Svir, Velikaya and Volkhov rivers flow to the Baltic Sea that drains into the Atlantic Ocean. In the south and south-west, the Dnieper River with its tributaries (Sozh, Desna, Seim rivers), the Don (1870 km, 422,000 km2) and the Kuban (870 km, 58,000 km2) rivers also belong to the Atlantic Ocean’s basin, but via the Black Sea and the Mediterranean. The basin of the Volga River (3531 km, 1,361,000 km2) with its tributaries, such as the Oka and Kama, occupies the largest part of the Central Russian Plain. The Volga and Terek rivers flow into the inland Caspian Sea.

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All rivers within the Russian Plain have a low gradient and a slow flow rate. Most of the rivers, especially in the upper and middle reaches, have meanders and form floodplains of the segmented type. The relief of such floodplains consists of multiple segments, i.e. series of interchanging curve-shaped, linear fluvial levees and hollows. The hollows are usually hardly drained or permanently inundated. As a result, loop-lakes or eutrophic swamps are formed there. In the deltas of the largest rivers (such as the Volga, Don, Northern Dvina and Kuban rivers), flow channels often branch, forming island-like floodplains (this is named “plavny” in Russian). On the western slope of the Ural Mountains rivers have steep gradients and swift currents in their upper reaches but turn into flatland rivers in their lower reaches. The rivers are fed by liquid precipitation, melting snow and underground water; in the Greater Caucasus rivers are also fed by melt water from glaciers. In winter, almost all the rivers in the Russian Plain are covered with ice. As regards the runoff regime, the rivers have their maximum runoff in spring. And as regards their chemistry, the rivers are of the hydrocarbonate type. Most lakes in European Russia occur in the north-west of the Russian Plain and in Fennoscandia, where lakes occupy about 10% of the total area. There we find the largest lakes of Europe, e.g. Lake Ladoga (area 17,700  km2), Lake Onega (area 9700 km2), the Chudskoe and Pskovskoe lakes (total area 3550 km2), Lake Ilmen (area 982 km2) and Lake Imandra (area 876 km2). There are more than 30 man-made large water reservoirs with an area of more than 1000  km2 each in European Russia (Edelshtein 1998). The total area of the reservoirs here is estimated at 43,000 km2. Cascades of reservoirs have been created in the basin of the Volga and Kama rivers since the middle of nineteenth century, though most of the construction activity took place in the middle of the twentieth century. The Kuybyshev and Rybinsk reservoirs are the largest ones in the European part of Russia (6500 km2 and 4550 km2, respectively). There are also lake reservoirs (e.g. the Onega Lake Reservoir) in the north-west of the Russian Plain, in Karelia and the Kola Peninsula. The large rivers and lakes of the Russian Plain are connected by canals into an integrated hydrotechnical system. According to Botch et  al. (1995) and Botch (1999) wetlands occupy 380,000 km2 in European Russia, which comprises 24% of the total area of wetlands in all of Russia. According to Vompersky et  al. (1999), waterlogged areas amount to a total of 588,000 km2 in European Russia, of which 36% are classified as “in-forest” swamps and bogs (with a peat layer of 30 cm or less) and 64% as treeless mires and bogs (with a peat layer of more than 30 cm). Wetlands are most common in the north of European Russia, in the tundra and northern taiga regions. Wetlands occupy 50–70% in the tundra areas, where frost mound bogs dominate (Botch 1999). In the basins of the Onega, Pechora and Northern Dvina rivers, wetlands occupy 25%, 23% and 8.5% of the total areas of the basins, respectively (Marchenko et al. 2006). In Karelia and the Kola Peninsula, wetlands occupy about 30% of the total area. Raised bogs with Sphagnum predominate there; they form about 60% of the total wetland areas. In the basins of the Volga and Don rivers, fens and swamps are more common than bogs; wetlands occupy there 3.8% and 1.9% of the areas of the basins.

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1.2  Climate The climate of the European part of Russia is influenced by several main factors. Openness of the area to Arctic and Atlantic air masses; interaction of the arctic, polar and tropical air masses; and considerable atmospheric motion both in summer and in winter (especially in the northern and the middle latitudes) define the climate patterns and create a highly variable weather (Lydolph 1977; Myachkova 1983). Due to the moderating influence of the Atlantic Ocean, most of the Russian Plain and surrounding areas experiences a temperate continental climate; only its northernmost part (north of 66°N, Tundra zone) has a subarctic climate (Alisov 1969). Within the temperate continental climatic area, we distinguish the following four climatic regions (Alisov 1969; Myachkova 1983): 1. The Atlantic-Arctic climatic region, located to the north of 60°N; it is moderately warm with abundant humidity. 2. The Atlantic-Continental-European climatic region, located between 60°N and about 53°N; it is moderately warm with moderate humidity. 3. The Continental-European climatic region, located south of 53°N except for the area of region (4); it is very warm with deficient humidity. 4. The Continental-East-European climatic region, located along the Lower Volga and the Caspian Sea; it is very warm and dry. Throughout the year the European part of Russia is mainly influenced by the western transfer of air masses. The high frequency of atmospheric fronts causes a relatively high amount of precipitation in the forested areas. The smooth topography and the latitudinal transport of air masses contribute to the latitudinal pattern of distribution of climatic parameters. An essential climatic feature of European Russia is that the Atlantic air coming in from the mid- and high latitudes of the North Atlantic Ocean is, during the cold season, warmer in the western part of the area than in the eastern part, and, during the warm season, it is colder in the western part than in the eastern part. Besides, cold air masses penetrate more often into the eastern regions from the central and the eastern parts of the Arctic and from Siberia. All this causes a decrease in the air temperature from west to east in the cold season and vice versa in the warm season. As a result, the amplitude of the annual temperature increases from west to east, and the east experiences a more continental climate compared to the west. The cold climatic zones located in the north-eastern part of European Russia are the coldest in the season when temperatures are below freezing. The average temperature of January decreases from the south-west to the north-east, from 0°C on the Black Sea coast to −20°C in the east of the Komi Republic and within the forest zone from −8°C near the western border of Russia to −20°C in the northeast. The warmest month over almost the entire area is July, when the average monthly temperature increases from NNW to SSE from 10°C on the Arctic coast to 24°C near the Caspian Sea. Within the forest zone, the average July temperature changes from 14 to 20°C in the same direction (Spravochnik po klimatu SSSR

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1964–1969; Lydolph 1977; Myachkova 1983; Kobysheva et  al. 2001). On the whole, the average annual air temperature in European Russia varies from −6 to −8°C in the extreme north-east to +8 °C in the south (till +14°C at the subtropical Black Sea coast of the Caucasus). Within the forest zone, the temperature also varies from −4°C in the north-east to +6°C in the south-west. We should note that we present climatic parameters according to the Reference Book on Climate of the USSR (Spravochnik po klimatu SSSR 1964–1969), where the average temperatures are calculated for the period from 1881 to 1960 and the average precipitation values are calculated for the period from 1891 to 1960 with all corrections on the measurement procedures (details on precipitation measurement and correction are described by Groisman et al. 1991). A short description of climatic changes after 1960 in European Russia can be found at the end of this section. We show the distribution of some climatic parameters over European Russia in Figs. 1.2, 1.3, 1.4 and 1.5. To design the figures, a database on climatic parameters measured in more than 1000 meteorological stations located in European Russia was used (Rozhkova and Zukert 1996; Zukert 2006). Data from the Reference Book on Climate of the USSR (Spravochnik po klimatu SSSR 1964–1969) were taken. Data include the station’s geographic position (latitude, longitude and elevation above sea level) and the following groups of climatic parameters: solar radiation, air temperature, precipitation, air humidity, soil temperature, data on snow cover, wind speed and others. Figure 1.2 shows the sum of PAR (photosynthetically active radiation) for the growing season when the average daily temperature (t) is more than +5°C. The PAR changes from about 200 MJ/m2 in the north to more than 1800 MJ/m2 in the south. Generally, in midsummer the incoming solar radiation depends only slightly on latitude, and the differences in the sums for the growth period are caused mainly by differences in the duration of this period. The total annual sum of precipitation in mm is presented in Fig. 1.3. The maximal precipitation in the East European Plain (700–800 mm per year) is observed within a belt around 60°N. In the west the belt is wider and the values are more than 800 mm in uplands (see Fig. 1.1). Throughout the year, there is a cyclonic circulation at these latitudes that transfers great amounts of moisture from the Atlantic Ocean. The precipitation increases due to the presence of the dissected and forested uplands (Central Russian, Smolensk-Moscow, Severnye Uvaly uplands and Valdai Hills). The precipitation totals decrease from the centre to the north and the south. In the Arkhangelsk region, in the Komi and Karelia republics, the total annual precipitation is 600–700 mm; it decreases to 500–600 mm at some places on the Arctic shore and increases to 1000 mm and more in the Khibiny Mountains and in the Ural Mountains. South from the central part of the Russian Plain, the annual precipitation decreases from the north-west to the south-east and reduces to 200–400 mm in the Caspian Depression. In the western part of the Northern Caucasus, the annual precipitation ranges from 600 to 800 mm in Ciscaucasia to 1000–1500 mm and more in the Greater Caucasus Mountains and at Black Sea coast. In most of European Russia, about 70% of the annual precipitation falls during a conventional “warm period” from April to October. But the real durations of warm

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Fig. 1.2  Sums of photosynthetically active radiation (PAR) in MJ/m2 for the vegetation period (t > 5°C)

(vegetative) and cold (non-vegetative) periods are quite different within so vast an area. The duration of the vegetative period and the relative part of the annual precipitation within this period decrease from south to north. The duration of snow cover ranges from more than 180 days to 25 days per year; the depth of the snow cover varies from less than 10 to 50 cm (Kobysheva et al. 2001). Figures 1.4 and 1.5 show the distributions of (1) the sum of air temperatures (degree days) during the period of active vegetation growth which is defined as a

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Fig. 1.3  Annual sum of precipitation, mm

period with daily mean temperatures of 10°C or more and (2) Selyaninov’s hydrothermic coefficient (HTC) calculated as the ratio of the total precipitation in mm within this period divided by one tenth of the sum of the average daily air temperatures of 10°C or higher (Selyaninov 1937). Sums of temperatures correlate well with the total net radiation (Budyko 1974), and this makes it possible to use the sums for the estimation of potential evapotranspiration. Thus, HTC is an estimate of the ratio between the precipitation and the potential evapotranspiration and can be considered as an index of humidity. (Selyaninov’s hydrothermic coefficient (HTC) is always calculated on

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Fig. 1.4  Pattern of the sum of air temperatures for the period with mean daily temperatures above 10°C

the basis of 10°C or higher, and this coefficient is very widely used in Russia, particularly in agricultural analyses. However, forest vegetation clearly starts growing at temperatures of 5°C or higher, and therefore we use that limit in Fig. 1.2.) The sum of temperatures above 10°C shows a latitudinal distribution (Fig. 1.4) that reflects the leading role of solar energy and net radiation in the distribution of air temperatures. The spatial distribution of precipitation totals for the period of active growth is similar to the pattern for the annual totals (Fig. 1.3), but the absolute values

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Fig. 1.5  Pattern of Selyaninov’s hydrothermic coefficient (HTC)

in the central and especially in the northern parts of the territory are less because of a decrease in the length of the growth period. In Fig. 1.5 we see “theoretical zones” of forested and non-forested areas calculated on the basis of climatic parameters: areas with a Selyaninov’s HTC of more than 1 can be considered as rather moist, typical forested areas, and areas with a HTC of less than 1 can be considered as a zone of moisture shortage, i.e. “the calculated steppe and/or semi-desert zones”. There are regions with permafrost in the north and north-east of European Russia. The southern boundary of the permafrost zone passes along the Kola Peninsula and

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then from the Mezen River’s mouth to the midstream of the Pechora River and then descends across the western slope of the Ural Mountains to 64°N (Kudryavtsev et al. 1981). In most of this area, the permafrost bedding is discontinuous owing to various meso- and microclimatic features as affected by relief, vegetation, etc. Only in the extreme north-east of European Russia, the distribution of permafrost is continuous. The thickness of the permanently frozen layer reaches 25 m in the downstream area of the Pechora River and 80–130  m around Vorkuta (Kobysheva et  al. 2001). Permafrost also occurs in the Caucasus, as a rule at elevations above 3000 m asl. It is general knowledge that climates are changeable. During the last century (1901–2012), the global average surface air temperature increased by 0.89°C with an average rate of 0.075°C/10 years (IPCC 2013, 2014) and 0.166°C/10 years in 1976–2012 (Roshydromet 2014a). The warming in European Russia is even larger than the global warming: the mean temperature in the region increased by 1.19°C from 1907 to 2006 vs. 0.75°C for the global temperature for the same period and by 1.51°C (vs. 0.57°C) for the period 1976–2006 (IPCC 2007; Roshydromet 2008a, b). From 1976 to 2012, the average rate of air temperature warming in European Russia was 0.52°C/10 years (Roshydromet 2014b). Thus, most of the contemporary warming really took place during the last 40 years. The largest increase in minimum and maximum daily temperature occurred in the cold season, i.e. the number of frosty days decreased. The spatial distribution of air temperature trends is not uniform. The fastest temperature increase is in the centre, west and the north-west of European Russia and the slowest in the east and the south (Roshydromet 2014a, b). Changes in the precipitation are less pronounced, and often they are evaluated with less confidence than changes in the air temperatures. It was found that the average annual precipitation over the whole of European Russia slightly increased during the last decades, but for different subregions, the estimates are rather ambiguous.

1.3  General Description of Forest Vegetation European Russian forests spread almost continuously over the Russian Plain for 2000 km from 66°N to 53°N. Besides, there are large forest areas located in the Caucasus within the Russian Federation: on the Black Sea coast and on the northern slope of the Greater Caucasus. From north to south on the Russian Plain, the composition of the late-successional trees in the forest overstorey clearly changes, and this allows a delineation of three main forest regions in meridional direction (Smirnova 2004): the boreal, the hemiboreal and the nemoral regions (Fig. 1.6). The boreal region is characterized by the natural occurrence of dark-coniferous trees: Picea spp. (spruce), Abies sibirica (Siberian fir) and Pinus sibirica (Siberian cedar). The hemiboreal region typically shows the joint natural occurrence and co-­ domination of dark-coniferous and broad-leaved trees: Tilia cordata (linden), Quercus robur (oak), Acer spp. (maple), Ulmus spp. (elm), Fraxinus excelsior (ash), etc. In the nemoral region, typically broad-leaved trees dominate. Maps of the distribution areas of the main late-successional tree species are presented in Fig. 1.7.

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Fig. 1.6  The boreal (1), the hemiboreal (2) and the nemoral (3) forest regions in European Russia. Borders of the regions are delineated according to Isachenko (2001) and based on the modern boundaries of the forest distribution areas

We accept the borders of these regions according to Isachenko (2001) (Fig. 1.6) where the boreal region includes the north and the middle taiga forest areas as marked in the review “Vegetation of the European part of the USSR” (Gribova et al. 1980). The hemiboreal region corresponds to the south taiga area and an area of mixed coniferous-broad-leaved forests; and the nemoral forest region includes an

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Fig. 1.7  Distribution areas of the main late-successional tree species: (a) Picea spp., (b) Abies sibirica, (c) Quercus robur and (d) Tilia cordata (a, b and c are taken from Sokolov et al. (1977); d is taken from Sokolov and Stratonovich (1958))

area of broad-leaved forests and the forest-steppe area. Delineation of these three forest regions is also in accordance with Walter (1968) and Ahti et al. (1968) though Ahti et  al. (1968) deviate by considering the hemiboreal region to comprise the southern taiga and the northern part of the broad-leaved-coniferous forests whereas its southern part is attributed to the temperate region.

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Fig. 1.8  Dominant tree species and canopy density for European Russia. Fragment from Bartalev et al. (2004) with the boundaries of three forest regions delineated according to Isachenko (2001)

According to a map of the actual forest vegetation (Bartalev et al. 2004), the total forest cover in these three regions comprises an area of approximately 1,700,000 km2 which amounts to about 60% of the total area of the delineated regions, but it ranges from 77% in the boreal region to 19% in the nemoral region (Fig. 1.8) (The derivation of the actual forest map is described below in Sect. 2.3).

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From the forest-steppe southwards till the Caucasus Mountains, there is a vast woodless area of mainly agricultural use (mainly arable lands). Fragments of East European steppe vegetation occur there (Keller 1927, 1931; Lavrenko 1940; Gribova et al. 1980). Here we describe the main features of the forest vegetation in the delineated regions.

1.3.1  Boreal Forest It extends in the European part of Russia from 66°N to 60°N and from the border with Finland in the west to the watershed ridge of the Ural Mountains in the east. The northern boundary between the boreal forest and the treeless tundra is not sharp. The density of the forest gradually decreases towards the north, and sparse trees or groups of trees grow in the tundra. In Russia, the boreal forest is traditionally divided into the northern and the middle taiga (Lavrenko and Sochava 1956; Gribova et  al. 1980). The northern taiga occurs between 66°N and 64°N and stretches from the western boundary of Russia to the Ural Mountains along the north edge of Lake Onega. The ground layer in the northern taiga contains boreal species with an admixture of arctic-alpine species. The middle taiga reaches from 64°N to 60°N from the western Russian boundary in South Karelia to the upper reaches of the Vychegda and Luza rivers in the east. In the south-east, however, in the Kama River basin, the boundary of the middle taiga stretches till 57°N (Lavrenko and Sochava 1956). In the ground layer in the middle taiga, boreal species dominate and arctic-alpine species practically do not occur. Besides the northern and middle taiga, we also distinguished the north-eastern European forests occurring east of the Mezen River till the Ural Mountains (in the Mezen and Pechora rivers basins). They are characterized by a significant participation of Siberian species, with among trees Abies sibirica, Pinus sibirica, Larix sibirica (larch) and Juniperus sibirica (juniper). According to Bartalev et al. (2004), forest covers approximately 900,000 km2 in the boreal forest region. From these, 63% is now occupied by stands dominated by early-successional tree species: two-thirds by Betula spp. (birch) and Populus tremula (aspen) and one-third by Pinus sylvestris (Scots pine). The remainder 37% of forested lands is occupied by stands dominated by Picea spp. or a co-domination of Picea obovata and Abies sibirica (Fig. 1.8). The prevalence of stands formed by early-successional tree species indicates the high level of catastrophic disturbances (such as fire, storm and cutting) in the boreal forest region. We will discuss this in detail in Chap. 3. Without severe disturbances, dark-coniferous trees will dominate: Picea abies in the west and Picea obovata, Abies sibirica and sometimes Pinus sibirica in the east (Lavrenko and Sochava 1956; Gribova et al. 1980). The main dominant is Picea spp. which includes Picea abies, Picea obovata and their hybrid Picea x fennica. The most sizeable tracts of dark-coniferous forest (with basically Picea spp.) are confined to watershed plateaus or plains on loamy moraines. Extensive tracts of for-

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est with Picea obovata, Abies sibirica and Pinus sibirica (in places) are also located on the western slope of the Ural Mountains. The upper limit of dark-coniferous forest in the Ural Mountains increases to the south: it lies at an altitude of 200 m asl in the Nether-Polar Urals, at 550–650 m asl in the Northern Urals and at 800 m asl in the Central (Middle) Urals. Above that limit there is a narrow belt of Larix sibirica and Betula spp. trailing off to mountain tundra (Lavrenko and Sochava 1956). Light-coniferous forests dominated by the light-demanding coniferous trees Pinus sylvestris and Larix sibirica (which only occurs in the east and to a much lesser extent than Pinus sylvestris) occur in the boreal forest region depending on relief, geomorphology and fire history of the area. Pinus sylvestris stands clearly dominate on the Baltic Crystalline Shield and in the Kola Peninsula. They also occur widely on outwash in the large river valleys and fluvioglacial lowlands (Gribova et al. 1980). Betula pendula, Betula pubescens and Populus tremula and much less Alnus incana, Padus avium and some other trees usually occur as admixture in coniferous forests. These species also form pure small-leaved deciduous forests: Betula spp. and Populus tremula typically grow over vast areas after clear cuttings and fires; Betula spp. and Alnus incana often grow on abandoned agricultural lands. In the understorey of boreal forests, moderate trees and shrubs often occur. Among them are Sorbus gorodkovii (in the west), S. aucuparia (in the central and eastern regions), Juniperus communis, Rosa cinnamomea (in the west), R. acicularis (in the east), Lonicera pallassii and more rarely L. xylosteum, Spiraea medium, Frangula alnus, Daphne mezereum and Ribes spp. The ground layer in the boreal forest region on the whole is characterized by a high constancy and dominance of boreal dwarf shrubs, small herbs and small ferns in a field layer together with various combinations of bushy lichens, boreal green and sphagnum mosses in a bottom layer (Smirnova 2004). The most common dwarf shrubs are of the genera Vaccinium, Pyrola, Lycopodium and Empetrum and also Linnaea borealis, Calluna vulgaris, etc.; common small ferns are Gymnocarpium dryopteris and Phegopteris connectilis; and small herbs are Oxalis acetosella, Maianthemum bifolium and Trientalis europaea. In the bottom layer, Pleurozium schreberi and Hylocomium splendens are common and also species of the genera Polytrichum, Dicranum, etc. In areas with stagnant moisture, Sphagnum species and oligotrophic dwarf shrubs, sedges and herbs such as Carex globularis, Equisetum sylvaticum, Empetrum nigrum, Rubus chamaemorus and Vaccinium uliginosum dominate. Bushy lichens from the genera Cladonia, Cetraria, Stereocaulon, etc. are widespread in light-coniferous (Scots pine mainly) forests. In the dark-coniferous forests, epiphytic lichens on the trunks and branches of trees are common. In the boreal forest region, one can also find unique intact old-growth spruce and spruce-fir forests dominated by tall herbs (Aconitum septentrionale, Crepis sibirica, Paeonia anomala, Delphinium elatum, Actaea erythrocarpa, Thalictrum minus, etc.) and/or large (tall) ferns, such as Diplazium sibiricum, Dryopteris dilatata and Athyrium distentifolium, often with an appreciable occurrence of nemoral and meadow-edge species (Lathyrus vernus, Melica nutans, Paris quadrifolia, Stellaria holostea, Viola mirabilis, Vicia sylvatica, etc.). These forests are found not only in

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river valleys but also on the watersheds (see Chap. 3). However, these forests are located in hard-to-access regions and occupy only a small part of the total area of dark-coniferous boreal forests. There are a lot of swamps, bogs, mires and waterlogged forests in the boreal forest region. In the northern taiga, wetlands occupy 30–50% of the area (Vompersky et al. 1999). Aapa mires dominate there. Aapa massifs with plane-concave surfaces and a typical complex of oligo- and mesotrophic hummocks and eutrophic hollows occupy vast areas on the slopes of watersheds and in depressions. The band of aapa mires stretches along the northern limit of the taiga forest region in European Russia and extends further to Yakutia. In the middle taiga, wetlands occupy 10–30% of the area (Vompersky et al. 1999). Convex hummock-ridge bogs dominate there. They form up to 1000 km2 large wetland areas on the moraines. Forest bogs are typical in the taiga forest region; they are mainly mesotrophic pine and spruce bogs on slopes. On boreal mountains (Kola Peninsula, Ural Mountains), blanket bogs have formed at hilltops and slopes; and swamp forests and forest bogs have formed in river valleys and hollows. At high altitudes, frost mound bogs and aapa mires occur (Kirjushkin 1980; Liss and Astakhova 1982; Lopatin 1988). In river valleys with flowing moisture and without large catastrophic disturbances, spruce and spruce-fir forests dominate. Admixture of Betula pubescens (in the north) and Alnus incana and A. glutinosa (southward) is common. In the understorey shrubs such as Ribes nigrum, R. spicatum and Viburnum opulus dominate, and large herbaceous nitrophilous and hygrophilous species such as Filipendula ulmaria, Urtica dioica, Carex vesicaria, etc. form the field layer.

1.3.2  Hemiboreal Forest It stretches in the European part of Russia as a tapering band from Russia’s western border with Estonia, Latvia and Belarus in the west to the watershed ridge of the Ural Mountains in the east (Figs. 1.6 and 1.8). The southern border of the region is located at 53°N in the west and at 56°N in the east. The region is traditionally divided into the areas of the southern taiga and those of the mixed coniferous-broad-­ leaved forest (or subtaiga, “podtaiga” in Russian) which border each other at about 58°N (Lavrenko and Sochava 1956; Gribova et al. 1980). It is commonly understood that in the southern taiga broad-leaved trees keep subordinate positions in comparison with dark-coniferous trees, i.e. they grow only in the forest understorey or are missing completely, whereas in the subtaiga broad-leaved and coniferous trees are equally important and both grow in the overstorey. However, for various reasons coniferous or deciduous tree species may prevail locally. Nowadays, most of the forested area of the hemiboreal region is occupied by pioneer deciduous (first of all, birch and aspen) forests (Fig. 1.8) as a result of severe anthropogenic impacts during the past centuries. However, with a long-time absence of severe catastrophic disturbances, dark-coniferous (Picea spp., Abies sibirica) and broad-leaved (Tilia

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cordata, Acer spp., Ulmus spp., Quercus robur, Fraxinus excelsior, etc.) trees keep equal positions in the forests throughout the entire hemiboreal region (Porfiryev 1950; Bulokhov 1973; Zaugolnova et al. 2001; Smirnova 2004). The number of dark-coniferous and broad-leaved trees and the composition of the forests change in latitudinal and longitudinal directions. In the Kaliningrad region, one can find multispecies forests with Picea abies, Fagus sylvatica, Tilia cordata, Carpinus betulus, Fraxinus excelsior, Acer platanoides, A. ­pseudoplatanus, Ulmus glabra, etc. (Gribova et al. 1980). The same species, except Fagus sylvatica, Carpinus betulus and A. pseudoplatanus, occur in forests in the central part of the Russian Plain. In the Middle Volga area (north of Kostroma and Nizhny Novgorod regions), hybrid forms of Picea abies and P. оbovata (joined often in P. х fennica) and Abies sibirica occur. East of the Volga River till the Ural Mountains, Acer campestre and Fraxinus excelsior are disappearing, and Quercus robur and Acer platanoides are becoming rare. Dark-coniferous-broad-leaved forests are composed here of Picea оbovata, Abies sibirica, Pinus sibirica (in the extreme east), Tilia cordata and Ulmus scabra. Tilia cordata and Abies sibirica dominate in the Ural region. In the upper parts of ridges, mixed coniferous-broad-leaved forests give way to pure dark-coniferous stands of Abies sibirica and Picea оbovata which grow to an altitude of 800–1200 m (Gribova et al. 1980). As mentioned above, mixed dark-coniferous-broad-leaved forests are mainly destroyed as a result of human activities. They survive in very small areas in the Russian Plain and in the Ural Mountains as well (Kolesnikov 1969; Kolesnikov and Shimanyuk 1969; Zubareva 1972, 1975; Popadyuk et  al. 1999). According to Bartalev et al. (2004), all forests occupy 65% of the hemiboreal area, 86% of that as birch and aspen, 11% as light-coniferous trees Pinus sylvestris and Larix sibirica (the latter over a small part and only in the east) and less than 3% and less than 1%, respectively, dominated by dark-coniferous and broad-leaved trees (Fig. 1.8). In the north-west of the region, most of Picea abies forests occur on glacial-­ accumulative relief positions. Forests dominated by Picea spp. and broad-leaved trees occur in uplands (Valdai Hills, Smolensk-Moscow, Severnye Uvaly uplands). Light-coniferous forests prevail as a rule on ancient alluvial plains (Polesie areas) and on river terraces. Broad-leaved-pine forests, mainly oak-pine and much less linden-pine forests, often occur in the south of the region (in the subtaiga area) (Gribova et al. 1980). The hemiboreal forest per se is a transition zone between boreal and nemoral forests, and as consequence the flora of the hemiboreal forests is quite rich. The presence of early- and late-successional coniferous and deciduous trees determines the forming of complicated boreal-nemoral floristic complexes. Richest in species are forests characterized by a high constancy of both boreal and nemoral species. The composition of shrub species is mainly the same as in the boreal region. Corylus avellana additionally appears here and the abundance of Viburnum opulus, Euonymus verrucosa and Lonicera xylosteum increases. Boreal dwarf shrubs, small herbs and ferns are mainly the same as in the boreal region. Among nemoral species, the most constant species are summer-green, such as Aegopodium podagraria,

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Carex pilosa, Mercurialis perennis, etc.; evergreen plants, such as Asarum europaeum, Galeobdolon luteum, etc.; and early spring plants (efemeroids), such as Anemonoides nemorosa, A. ranunculoides, Corydalis solida, Gagea lutea, G. minima and others. In the bottom layer, in addition to the common boreal green mosses, there are hemiboreal mosses, such as Atrichum undulatum, Rhodobryum roseum and species of the genera Mnium, Plagiomnium, Eurhynchium, Brachythecium and others. Boreal species in the understorey are more common under dark-coniferous trees, while nemoral species are more common under broad-leaved trees. In hemiboreal forests which experienced minimal anthropogenic impacts, boreal and nemoral tall herbs and tall ferns dominate. The boreal species are Aconitum septentrionale, Actaea erythrocarpa, Atragene sibirica, Cacalia hastata, Cardamine macrophylla, Crepis sibirica, Delphinium elatum, Cicerbita alpina, Cinna latifolia, Paeonia anomala, Geranium albiflorum, Dryopteris dilatata, etc.; and the nemoral ones are Actaea spicata, Campanula latifolia, C. trachelium, Delphinium cuneatum, Digitalis grandiflora, Festuca gigantea, Lilium martagon, Cypripedium calceolus, Bromopsis benekenii, Lunaria rediviva, Scutellaria altissima, Dryopteris filix-mas, D. cartusiana, etc. In the hemiboreal light-coniferous and small-leaved deciduous forests developed after fires or ploughing, the flora is similar to the flora in the boreal forests developed after similar impacts. Owing to changes in hydrological regimes and impoverishment of soils after impacts, lichens, green and sphagnum mosses often dominate in the ground layer, as in the boreal region. In the hemiboreal region, wetlands occupy up to 30% of the area in the north (in the southern taiga) and about 10% of the area in the south (in the mixed coniferous-­broad-­leaved forests) (Botch 1999). Convex hummock-ridge bogs on the moraine ridges in the uplands (Smolensk-Moscow Upland, Valdai Hills, Galich Upland and Severnye Uvaly; Fig. 1.1) and mesotrophic spruce and pine bogs are more common in the north. Spacious peat-forming fens with dominance of Carex spp. and grasses, wooded swamps with Alnus glutinosa and small species-rich swamps around water sources occur widespread in the south of the region, mainly in lowlands with Polesie relief (Nerussa-Desna Polesie, Meshchera and Upper Volga lowlands). In areas with an abundant flow of moisture, in the valleys of streams and small rivers, Alnus glutinosa flooded forests occur. Broad-leaved trees (Tilia cordata, Ulmus spp.) and dark-coniferous trees (Picea spp., Abies sibirica) with Betula spp. also occur there. The understorey is richer in species in comparison with the understorey in boreal flooded forests. In areas with minimal anthropogenic impacts, nemoral plants (Aegopodium podagraria, Stachys sylvatica, Ajuga reptans, Cardamine impatiens, Convallaria majalis, Mercurialis perennis, Milium effusum, Campanula trachelium, Delphinium cuneatum, etc.) in addition to nitrophilous plants (Aristolochia clematitis, Calystegia sepium, Cirsium oleraceum, Filipendula ulmaria, Lycopus europaeus, Lysimachia vulgaris, Thalictrum aquilegifolium, Urtica dioica, Geum rivale, Poa remota, Solanum dulcamara, etc.) occur in the ground layer.

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1.3.3  Nemoral Forest It extends in the European part of Russia from the border with Ukraine in the west to the Ural Mountains in the east (Fig. 1.6). The southern boundary of the region is located at 50°N in the west and at 53°N in the east. The region comprises an area of broad-leaved deciduous forests and forest-steppe (Lavrenko and Sochava 1956; Gribova et al. 1980). In the north of the region, broad-leaved forests composed of Quercus robur and Tilia cordata. Acer platanoides, Ulmus glabra and Fraxinus excelsior also occur there. To the south, Acer campestre becomes more common. Broad-leaved forests located at the right bank of the Volga River are mainly dominated by Quercus robur and the forests on its left bank by Tilia cordata and Acer platanoides. Forests dominated by Tilia cordata are common close to the Ural Mountains and on the western slope of the Urals where these forests mainly occupy outwash terrains, lower slopes and flat tops of ridges (Gorchakovskiy 1968, 1972). In the Ural Mountains, broad-­ leaved forests occur till an altitude of 800 m asl; oak in the form of elfin wood also grows at higher elevations where tall herb meadows are common. Nowadays, forests occupy only 19% (124,000 km2) of the region’s total area and occur only as separate islands between agricultural and urbanized lands (Figs. 1.8 and 1.9). According to Bartalev et al. (2004), forested lands are mainly dominated by birch and aspen (covering about 60% of the land), broad-leaved trees (29%) and Scots pine (11%). In the Russian Plain, broad-leaved forests are mainly situated on the watersheds. In the western and central parts of the nemoral region, broad-leaved forests (including old-growth forests) are mainly situated in natural reserves (Zapovedniks) and national parks at places where large forest massifs have been preserved since fifteenth to seventeenth centuries as defence lines of the Russian state against nomads (see Chap. 5 for details). In the forest-steppe, broad-leaved forests occur more often in the uplands. In the Central Russian and Middle Volga uplands, broad-leaved forests stretch southward as individual tongues and reach 50°N. On the Oka-Don Plain, the forests occur as separate islands. Further south in the steppe, floodplain oak forests can be found in river valleys and in gullies (“bayrachnyi” oak forest in Russian). Small-leaved deciduous forests dominated by Betula spp. and Populus tremula largely also have an insular distribution in the nemoral forest region. Large massifs dominated by Betula pendula and B. pubescens with participation of Populus tremula and Tilia cordata occur on the western slopes of the Ural Mountains and massifs dominated by small-leaved deciduous trees and Pinus sylvestris along the Tsna River (Fig. 1.9). Forests dominated by Pinus sylvestris are mostly found in small scattered tracts. The largest massifs are located on the eastern slopes of the Middle Volga Upland and in valleys and on terraces of the big rivers Don, Voronezh, Volga and others. On the western slopes of the Ural Mountains, light-coniferous forests composed of Pinus sylvestris and Larix sibirica with participation of Betula pendula occur in upper river valleys of the Belaya, Miass and other rivers. Pine-­

Fig. 1.9  Dominant tree species and canopy density in the nemoral forest region delineated according to Isachenko (2001). Fragment from Bartalev et al. (2004). The legend is the same as in Fig. 1.8

22 O.V. Smirnova et al.

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larch forests typically occur at altitudes of 200–600 m asl; sometimes they reach 800 m asl (Gribova et al. 1980). In the understorey, nemoral species are common. Among shrubs and moderately tall trees, Corylus avellana, Euonymus verrucosa, E. europaea, Lonicera xylosteum, Frangula alnus, Padus avium and Viburnum opulus often dominate and more rarely Daphne mezereum, Rosa canina and R. majalis. In broad-leaved forests with minimal human impact, the diversity of spring-growing and -flowering plants is maximal (Smirnova 1994). In addition to the species occurring in the hemiboreal region, Corydalis cava, C. marschalliana, Allium ursinum, Dentaria bulbifera, D. quinquefolia, Galanthus nivalis, Scilla siberica, S. bifolia and many others prevail here. Apart from the summer-green and evergreen species mentioned above for the hemiboreal region, we find here Brachypodium sylvaticum, Bromus benekenii, Festuca gigantea, Scutellaria altissima and many others. In well-preserved broad-leaved forests, nitrophilous plants such as Filipendula ulmaria, Cirsium oleraceum, Thalictrum aquilegifolium, Urtica dioica, Geum rivale, etc. also occur. Mosses are rare in these forests; they cover less than 5% in the ground layer. The most frequent species are those of the genera Atrichum, Fissidens, Eurhynchium, Plagiomnium and Bryum and also Mnium stellare, Ceratodon purpureus, etc. Boreal mosses such as Pleurozium schreberi, Hylocomium splendens, Dicranum polysetum and Climacium dendroides also can be found in the broad-leaved forests (Abramova and Kurnaev 1977; Ignatov and Ignatova 1992). In Pinus sylvestris forest on dry sandy soils, steppe grasses and herbs such as Calamagrostis epigeios, Thymus pallasianus, Polygonatum odoratum, Veronica officinalis, Pteridium aquilinum, Genista tinctoria, Dianthus arenarius and Koeleria glauca occur in addition to the bushy lichens which are also found in the boreal forests. In pine forests with excessive moistening and a stagnant-percolative regime, oligotrophic dwarf shrubs, sedges and grasses (Empetrum nigrum, Vaccinium uliginosum, Oxycoccus palustris, Comarum palustre, Rubus chamaemorus, Eriophorum vaginatum, Carex chordorrhiza, Molinia caerulea, Carex limosa, etc.) and the same sphagnum mosses as in the boreal and hemiboreal regions occur. In the valleys of streams and small rivers, large nitrophilous herbaceous species (Filipendula ulmaria, Calystegia sepium, Angelica archangelica, Lysimachia vulgaris, Lycopus europaeus, Solanum dulcamara, Aristolochia clematitis, Senecio fluviatilis, Athyrium filix-femina, Matteuсcia struthiopteris, etc.) occur with an admixture of nemoral herbs. Alnus glutinosa with participation of Ulmus laevis, Fraxinus excelsior, Padus avium, Betula pubescens and Populus tremula grow in the well-preserved flooded forests. Wetlands in the nemoral region occupy less than 10% of the region’s area (Botch 1999). They are diverse in their origin and structure, but all wetlands are small in size. Fens and swamps prevail, located along small- and medium-size rivers and dominated by sedges and grasses with Salix spp. and Alnus glutinosa in the overstorey. There are also mesotrophic fens dominated by both sphagnum and sedges and usually they occur under karstic conditions. Betula spp. and Alnus glutinosa can grow in the overstorey. Bogs with Ledum palustre and other typical oligotrophic species can be also found in the region. An area of lowland eutrophic wetlands and

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peatlands coincides with the southern strip of the broad-leaved forests, in forested areas extending into the forest-steppe.

1.4  General Description of Forest Soils Different soil classifications are used in Russia. All of them are based on the “genetic principles” proposed in the late 1880s by the Russian geologist Vasily Dokuchaev who is now regarded as “the father of soil science”. Two classification systems are mainly used in Russia nowadays. The first is the ecological-genetic soil classification system for the USSR soils (Klassifikatsiya and diagnostika pochv SSSR 1977) based on the works by Ivanova and Rozov (Ivanova 1956; Ivanova and Rozov 1956; Rozov and Ivanova 1967). The second is the New Russian factor-based soil classification system (Tonkonogov et al. 1997) based on the Fridland principles (1982). The New Russian system has common features with the International and American systems in methodology and in the attention paid to soil horizons and their features (Lebedeva et al. 2000; Bockheim and Gennadiyev 2000; Shishov et al. 2001). In our book, we mainly use the New Russian soil classification system (Tonkonogov et al. 1997) correlating with the names from the World Reference Base for Soil Resources (2006). A general description of the European Russian forest soils is based on the main review by Gerasimova (2007) and small-scale soil maps of the Russian Federation (Fridland et al. 1988; Glazovskaya 1995). Here we describe the forest soils in the three forest regions delineated in Sect. 1.3. For the description of the soils, we also use soil-geographic regions as marked by Glazovskaya (1973) with Gerasimova’s modifications (2007). These soil-geographic regions are largely consistent with the forest regions and are (1) boreal forest North European (Karelian) region, (2) boreal forest East European region, (3) sub-boreal forest West Kaliningrad region, (4) sub-­ boreal forest East European region and (5) sub-boreal forest-meadow-steppe East European region. The first two soil regions correspond to the boreal forest region, the third and fourth soil regions correspond to the hemiboreal forest region, and the fifth region corresponds to the nemoral forest region. Climatic parameters in the Boreal forest region, such as low temperature and abundant humidity, define the following important ecosystem features: the speed of the biological cycle is relatively low, and the amount of organic matter included in the biological cycle is relatively small in this region. As a result, the speed of soil forming and soil recovering after anthropogenic and natural catastrophic disturbances (such as fires, storms, cuttings, windfalls and others) is also relatively low. In the long run, soils with podzolic or eluvial horizons prevail; and semi-­ hydromorphic and hydromorphic soils are important in the region. In well-drained landscapes on coarse-textured deposits, Al-Fe-humus soils predominate (Podzols in WRB), such as podburs and podzols. On loamy deposits, fine-textured soils (Albeluvisols) are common. Two soil-geographic regions are described within the boreal forest region on the basis of differences in geomorphology, lithology and climatic conditions.

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The Boreal forest North European (Karelian) soil region is located on the Baltic Crystalline Shield. It is an area of young glacial landscapes mainly without ­permafrost and with numerous lakes and shallow gravelly-sandy sediments, together with rock outcrops, and lake clay confined to lake lowlands. Al-Fe-humic podzols (Haplic Podzols) with bog soils (Histosols, Gleysols) prevail here. There are quantitative differences between soils in the northern and the middle taiga: slight podzols (dwarf podzol) with a thickness of no more than 0.5 m prevail in the north; podzol thickness increases to 1 m towards the south. The typical change in soil from the watershed to lower parts (along the catena) is as follows: Haplic Podzols–Rustic Podzols–Histosols. The Boreal forest East European soil region is located in the boreal forest region outside of the Baltic Crystalline Shield. It is an area underlain by a thick layer of sediments; substratums are loams, rarely sands. In the northern taiga, excessive moisture and insular distribution of permafrost define the predomination of gley-­ podzolic soils (Gleyic Albeluvisols) on loams. Thicknesses of the organic horizon (weakly decomposed peaty forest litter) and bleached horizon (Albic) in Gleyic Albeluvisols are small: up to 5  cm and from 2 to 5  cm, respectively. Gleyic Albeluvisols are situated at well-drained sites such as convex slopes and convex tops. Flat interfluvial plains are occupied by marshes and surrounded by peaty and peat-boggy gleyzems (Histic Gleysols), podzolic-gleyic peat and peaty soils (Histic Albeluvisols). In the middle taiga, podzolics (Haplic Albeluvisols) dominate on loams; sod-podzolics (Albic Luvisols) occur to the south. In a typical profile of Albeluvisols, the eluvial horizon reaches 20–30 cm thick, and the depth of the total soil profile is 1.5 m thick or more. Haplic Albeluvisols are common west of the Northern Dvina River and close to the Ural Mountains. East of the Northern Dvina River till the areas close to the Ural Mountains, there are Histic Albeluvisols, peat soils and peatbogs. In the ancient and modern valleys of the Mezen, Pechora, Vychegda rivers and their tributaries, Haplic Podzols occur widespread. Sod-podzolic soils (Albic Luvisols and Haplic Albeluvisols) often occur in the Kargopol district and on the Obozerskoe Plateau (both in the Arkhangelsk region). Brown soils (Cambisols) seldom occur in plain areas. Usually they are confined to carbonate moraines, limestone and loose gypsum. For soils on these substratums, the biogenic structuring and forming of mull-humus has been described (Goryachkin and Makeev 1991). In the Northern Ural Mountains, different gleyzems (Histic Gleysols and Dystric Gleysols) and raw humus podburs (Entic Podzols and Rustic Podzols) are common. In the Middle Ural Mountains, there often occur soils with a homogenous profile attributable to brown soils (Dystric Cambisols). Brown soils forming under taiga forest are usually called “raw humic brown soils” or “acid brown soils”. They are considered as a transition form between podburs and brown soils (Gerasimova 2007). However, in the Northern Ural Mountains, there are brown soils with a mull-­ humus horizon (Humic Umbrisols) (Bobrovsky 2010). Various alluvial soils (Fluvisols) occur in river floodplain forests. Alluvial swamp meadow soils (Histic Fluvisols) and alluvial acid soils (Dystric Fluvisols) dominate in floodplains.

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The Hemiboreal forest region coincides with two sub-boreal forest soil regions. Climatic parameters in the hemiboreal region differ in their higher sum of air t­emperatures during the growing season and in a longer duration of the growing season compared to the boreal forest region. High summer air temperatures cause increased activity of soil processes. As a result, the thickness of the biologically active layer in the soil is also higher compared to the boreal region. Soils with moder-mull humus or mull-humus prevail. The soil macrofauna takes active part in the forming of the humus horizon. Loamy deposits are the main substratum in the hemiboreal region, including “covering loam”, morainic loam, two-term deposits (sands on a top of moraine loams and clays), calcareous loam, lacustrine-alluvial loam and clay. The loamy plains are dominated by fine-textured soils: sod-podzolics (Albic Luvisols and Haplic Albeluvisols) and podzolics (Haplic Albeluvisols). The degree of profile differentiation decreases from north to south (Tonkonogov 1999). Brown soils (Cambisols) also occur frequently in the region. The sub-boreal forest West Kaliningrad soil region is situated in the area of the Atlantic-European climatic region. A very flat topography and abundant moisture, which was much reduced by melioration, define the features of this soil region. There are forest soils on moraines and lacustrine-glacial interfluvial plains such as sod-podzolics (Umbric Albeluvisols) with a thin (4–10 cm) but dark humus horizon. These soils are close to brown soils (Cambisols), “brown soils podzolized”. Sandy and loamy-sandy soils are confined to outlier terraces and to the Kamov hills. Illuvial-ferruginous sod-podzols are situated on the sands; Cambisols are confined to the loamy sands. The sub-boreal forest East European soil region differs in that it has relatively homogeneous soils. The loamy plains are dominated by sod-podzolics (Albic Luvisols, Umbric Albeluvisols). From west to east, one can observe a decrease in total soil profile thickness and an increase in humus content in the humus-­ accumulative horizon. Podzolics (Haplic Albeluvisols) and sod-podzolics (Albeluvisols Umbric) with a second humic horizon occur in the central part and in the east of the Russian Plain. Waterlogging and attendant bleaching of the upper soil horizons as a result of surface gleization have been developed in the compacted soils on gentle slopes and flat watersheds (placors). As a result, extensive tracts of acid soils with periodically stagnant water (Haplic Stagnosols), acid soils with periodically stagnant water and clay-enriched subsoil (Luvic Stagnosols), podzolic-gley peat and peaty soils (Histic Albeluvisols) and gley-podzolics (Gleyic Albeluvisols) have been formed here. In addition, peat bog soils (Fibric Histosols, Sapric Histosols) occupy small areas in depressions. On sandy substratum Al-Fe-humus soils dominate: illuvial-humic ferruginous podzols (Haplic Podzols), illuvial-­ ferruginous and ochric podzols (Rustic Podzols) and podburs (Entic Podzols). In the moraine-outwash landscape, gleyic podzols (Gleyic Podzols) and peaty soils are common. The sub-boreal forest East European soil region is traditionally divided into three soil provinces on the basis of differences in geomorphology. They are the North-­ Western, Middle Russian and Kama-Vyatka Provinces.

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The North-Western Province is situated in the area of Valdai glaciations. Two-­ term (double) moraine deposits, which are associated with sod-pale-podzolic soils with a secondary bleached (gley) horizon (Gleyic Albeluvisols), are common there. On lacustrine-glacial clay, surface-gley soils (Luvic Stagnosols) with various boggy peats (Fibric Histosols and Sapric Histosols) occur. There also are raw humic brown soils (Dystric Cambisols) and various podzols. Calcareous pales (Cambisol Calcic) and residual-calcareous sod-podzolics (Umbric Albeluvisols) occur in the Izhorsk Uplands and near Lake Ilmen on calcareous glacial deposits. The Middle Russian Province is situated in the area of the Moscow and (partly) the Dnieper glaciations. Here are gently sloping moraine plains and low hills (Klinsk-Dmitrovsk and Smolensk-Moscow uplands) as well as outwash and lacustrine-­ alluvial plains (Upper Volga, Meshchera and other lowlands). Sod-­ podzolics (Umbric Albeluvisols) with a contrasting fine-textured profile prevail here. In depressions peaty and peat-boggy gleyzems (Histic Gleysols) as well as peat bogs (Fibric Histosols) are common. In lowlands, large bogs and gleyic podzols (Gleyic Podzols) occur. Illuvial-humic ferruginous podzols (Haplic Podzols) and podburs (Entic Podzols) prevail on homogeneous sands. Protic Arenosols occur in the Meshchera Lowland. North from Vladimir there is an area named Vladimirskoe Opolye where unique grey and dark-grey forest soils with a second humic horizon (Greyic Phaeozems) occur. The Vyatka-Kama Province is situated outside the glaciated area. Parent rocks are mainly surface deposits lying on Permian rocks. Sod-podzolics including sod-­ podzolics with a second humic horizon (Umbric Albeluvisols) prevail. Residual-­ calcareous sod-podzolics (Umbric Albeluvisols) and gleyic sod-podzolic (Gleyic Albeluvisols) also occur. Alluvial plains cover large areas (terraces of the Kama, Vyatka and Vetluga rivers). Illuvial-ferruginous and ochric podzols (Rustic Podzols) and podburs (Entic Podzols) with peat bogs (Fibric Histosols) are common. On the western slopes of the Ural Mountains within the hemiboreal forest region, raw humus brown soils (acid forest non-podzolic soils) (Haplic Cambisols) dominate. Also brown soils with mull-humus (Humic Umbrisols) and mountain forest-­ meadows soils (Haplic Leptosols) sometimes occur. The south has some sod-podzolic soils (Umbric Albeluvisols) on loams. Floodplains have Histic Fluvisols (with a peaty topsoil) and the following variants of Haplic Fluvisols: eutric (non-acid soils), dystric (acid soils) and seldom calcaric (calcareous soils). An important feature of the ecosystems in the Nemoral forest region is the potentially high speed of the biological cycle. It is defined by favourable temperature conditions, a large mass and a rich composition of litter caused by the abundance of broad-leaved trees and nemoral large-leaved herbs and a high activity of the soil macrofauna, first of all earthworms. As a result, in most of the nemoral forest region, a soil with a well-developed mollic A horizon occurs. The nemoral forest region is mainly confined to the sub-boreal forest-meadow-­ steppe East European soil region though the northern boundaries of the nemoral forest region and forest-meadow-steppe soil region do not fully coincide.

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According to the actual vegetation and features of soil structure and composition, the nemoral forest region is traditionally divided into two areas: (1) the broad-­ leaved forests and the northern forest-steppe area where grey soils (Greyic Phaeozems) prevail and (2) the southern forest-steppe area with a prevalence of grey non-podzolized soils (dark-grey soils) (Luvic Phaeozems), podzolized chernozems (Voronic Chernozems) and leached chernozems (Luvic Chernozems). As in the other regions, podzols dominate on fluvioglacial and alluvial plains. In the southern Forest-steppe area, Haplic Arenosols occur on sand substratums. Protic Arenosols are often confined to the homogeneous sands of continental dunes (Gerasimova 2007). There are several soil provinces in the nemoral region. They differ in structure and composition of their soils depending on topography, lithology and geomorphological features of the areas. In the central part of the Central Russian Upland, grey soils and chernozems are typical. In the northern part of the Upland, light-grey (Albic Phaeozems) and grey soils (Greyic Phaeozems) prevail, and also sod-podzolics (Albic Luvisols, Umbric Albeluvisols) and grey non-podzolized soils (dark-grey soils) (Luvic Phaeozems) occur. To the south, between Orel and Kursk, leached chernozems (Luvic Chernozems) and ordinary chernozems (Calcic Chernozems) dominate. In its western part, Chernozems prevail and Luvic Phaeozems occur. The soil cover on the Central Russian Upland is severely damaged by erosion. The Oka-Don Plain has the worst drainage conditions in the sub-boreal forest-­ meadow-­steppe East European soil region. Besides ordinary chernozems (Calcic Chernozems), there are meadow-chernozemics (Haplic Phaeozems) and solonetzic and solonchakous meadow-chernozemics (Sodic Phaeozems). In hollows solids (Albic Planosols) often occur. In the Middle Volga Upland, lithological diversity and rugged relief contribute to the soil diversity. In the northern part of the Upland, grey soils (Greyic Phaeozems) and dark grey soils (Luvic Phaeozems) prevail. To the south leached chernozems (Luvic Chernozems) and ordinary chernozems (Calcic Chernozems) occur on clays; podzolized chernozems (Voronic Chernozems) and dark-grey soils (Luvic Phaeozems) occur sporadically on loess loams. Grey soils (Phaeozems) are often confined to sandy substratum; Chernozems are confined to limestone. In the northern part of the Volga-Kama Plateau, light-grey (Albic Phaeozems) and grey soils (Greyic Phaeozems) prevail at higher elevations; dark-grey soils (Luvic Phaeozems) and Chernozems dominate in depressions. Chernozems (Calcic Chernozems, Voronic Chernozems, Luvic Chernozems) dominate to the south. In the northern part of the South Ural Mountains, grey soils (Greyic Phaeozems) dominate also on the plains; river valleys are occupied by Chernozems and meadow-­ chernozemics (Haplic Phaeozems). To the south, there are podzolized chernozems (Voronic Chernozems) and leached chernozems (Luvic Chernozems). In floodplains Haplic Fluvisols (eutric) and Mollic Fluvisols prevail.

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1.5  Conclusion Relief, hydrology and climate cause natural diversity of vegetation and soil in the forests of the Russian Plain and surrounding areas. At the same time, large areas dominated by pioneer tree species and vast non-forested areas in the forest regions give evidence of strong and extensive human impact on the forest ecosystems in the past and present. Taking the current state of the late-successional tree species into account from north to south, three main forest regions were delineated. These forests of the boreal, the hemiboreal and the nemoral regions will be described below with special attention paid to assessing the successional position of the forests and to effects of natural and anthropogenic factors on the composition and structure of the modern European Russian forests.

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Smirnova OV (ed) (1994) Vostochnoevropeyskie shirokolistvennye lesa. Izd-vo Nauka, Moscow, 363 pp – East-European broad-leaved forests Smirnova OV (ed) (2004) Vostochnoevropeyskie lesa: istoriya v golocene i sovremennost. Izd-vo Nauka, Moscow, vol 1, 479 pp; vol 2, 575 pp – East-European forests: the Holocene history and the current state Sokolov SYa, Stratonovich AI (1958) Tilia. In: Sokolov SYa (ed) Derevya i kustarniki SSSR.  Dikorastuschie, kultiviruemye i perspektivnye dlya introduktsii. Tom 4. Izd-vo AN SSSR, Moscow/Leninrgad, pp 699–702 – Tilia cordata Sokolov SYa, Svyazeva OA, Kubli VA (1977) Arealy derevyev i kustarnikov SSSR. Tom 1. Izd-vo Nauka, Leningrad. 240 pp – Distribution areas of trees and shrubs in the USSR. Vol. 1 Spiridonov AI (1978) Geomorfologiya Evropeyskoi chasti SSSR.  Izd-vo Vysshaya shkola, Moscow, 335 pp – Geomorphology of the European part of the USSR Spravochnik po klimatu SSSR (1964–1969) Iss. 1–34. Parts 1–5. Gidrometeoizdat, SPb.  – Reference book on climate of the USSR Tonkonogov VD (1999) Glinisto-differentsirovannye pochvy Evropeyskoi Rossii. Pochvennyi institut im. V.V. Dokuchaeva, Moscow, 156 pp – Clay-differentiated soils of European Russia Tonkonogov VD, Lebedeva II, Shishov LL (eds) (1997) Klassifikatsiya pochv Rossii. Pochvennyi institut im. V.V. Dokuchaeva, Moscow, 223 pp – Classification of soils of Russia Vompersky SE, Tsyganova OP, Kovalev AG, Glukhova TV, Valyaeva NA (1999) Zabolochennost territorii Rossii kak faktor svyazyvaniya atmosfernogo ugleroda. In: Izbrannye nauchnye trudy po probleme “Globalnaya evolyutsiya biosfery. Anropogennyi vklad.” Nauchnyi Sovet NTP “Globalnye izmeneniya pripodnoy sredy i klimata”, Moscow, pp 124–144 – Waterlogging in Russia as a factor of atmospheric carbon sequestration Voskresensky SS, Leontjev OK, Spiridonov, AI, Lukyanova SA, Ulyanova NS, Ananyev GS, Andreeva TS, Varuschenko SI, Spasskaya II (1980) Geomorfologicheskoe rayonirovanie SSSR i prilegayushchikh morei. Izd-vo Vysshaya shkola, Moscow, 343 pp – Geomorphological zoning of the USSR and adjacent seas Walter H (1968) Die Vegetation der Erde in ökologischer Betrachtung. Bd 2. Die Gemässigten und arktischen Zonen. Gustav Fischer Verlag, Jena World Reference Base for Soil Resources (2006) World Soil Resource Reports No. 103. FAO, Rome Zaugolnova LB, Istomina II, Tikhonova EV (2001) Ekologicheskiy, tsenoticheskiy i floristicheskiy analiz grupp assoctsiatsii khvoinoshirokolistvennykh lesov tsentra Evropeyskoy Rossii. Ecological, coenotic and floristic analysis of the association groups of coniferous  – broadleaved forests in the center of European Russia. Rastitelnost Rossii 2:38–48  – Ecological, coenotic and floristic analysis of the association groups of coniferous – broad-leaved forests in the center of European Russia Zubareva RS (1972) Tipy shirokolistvenno-khvoinykh lesov severnoy chasti Ufimskogo plato. Zapiski Sverdlovskogo otdeleniya Vsesoyuznogo botanicheskogo obshchestva 6:100–110  – Types of coniferous – broad-leaved forests in the middle part of the Ufa Plateau Zubareva RS (1975) Klassifikatsiya smeshannykh lesov predgornogo Preduralya. Trudy Instituta ekologii rasteniy i zhivotnykh Uralskogo filiala SO AN SSSR 93:3–52 – Classification of mixed forests of the Ural Mts foothills Zukert NV (2006) Klimaticheskaya karta i raspredelenie rastitelnykh zon Rossii. Lesovedenie 1:14–22 – Climatic map and distribution of the vegetation regions in Russia

Chapter 2

Methods of Investigation O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, L.B. Zaugolnova, S.A. Turubanova, P.V. Potapov, A.Yu. Yaroshenko, and V.E. Smirnov

Abstract  This chapter includes a list of the study areas and a map of their localities. The dominant ecological-coenotic approach to the forest vegetation classification together with seven ecological-coenotic groups of plant species and their ecological characteristics are described. The methods of mapping and monitoring the forest cover together with a short review of their applications in European Russia are presented. Field data sampling, data analysis, methods of plant diversity assessment, inventory of the ontogenetic structure of tree populations and the assessment of the successional position of the forest ecosystems are discussed.

O.V. Smirnova • L.B. Zaugolnova Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia M.V. Bobrovsky (*) Institute of Physico-Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] L.G. Khanina (*) Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] S.A. Turubanova • P.V. Potapov (*) Department of Geographical Science, University of Maryland, College Park, MD, USA e-mail: [email protected] A.Yu. Yaroshenko Greenpeace Russia, Moscow, Russia V.E. Smirnov Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia © Springer Science+Business Media B.V., part of Springer Nature 2017 O.V. Smirnova et al. (eds.), European Russian Forests, Plant and Vegetation 15, https://doi.org/10.1007/978-94-024-1172-0_2

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2.1  Study Areas The basis of this book is the documented investigations on the forest vegetation, carried out since 1980 by a large team of researchers under Prof. Olga Smirnova’s leadership in the forests of the European part of the ex-USSR including the ­outermost forest regions. European Russian forests from the northern taiga in the north to the forest-steppe in the south and from the western state borders to the Ural Mountains have been investigated with special attention to old-growth, late-­successional forests in every forest region. A list of the study areas and a map of the corresponding localities are presented in Table  2.1 and Fig.  2.1, respectively. In Chaps. 3, 4 and 5, we present the following information on the boreal, hemiboreal and nemoral regions, respectively: (1) a list of forest types in the region concerned, together with a general description of the forest types; (2) a short review of the traditional land-use systems and the current human impacts; and (3) analyses of structure, composition, plant diversity and dynamics of the main forest types with special attention to old-growth late-successional forests.

Table 2.1  List of the study areas in the forests of European Russia No. Administrative region Boreal forest region 1 Murmansk region

2 3 4 5 6 7 8 9 10

Karelia Republic Vologda region Arkhangelsk region Komi Republic

11 12 13 Perm region Hemiboreal forest region 14 Tver region 15 Moscow region 16

Forestry unit/reserve/national park N.A. Avrorin Polar-Alpine Botanical Garden-Institute of the Kola Research Centre of the Russian Academy of Sciences (RAS) Pyaozersk forestry unit Kostomuksha State Nature Reserve Atleka Zakaznik, Andomskiy forestry unit Russky Sever National Park Pinega State Nature Reserve Bereznikovskiy forestry unit Udorskiy forestry unit Mezhdurechensky forestry unit Koigorodskiy forestry unit Letskiy forestry unit Sosnogorskiy forestry unit Ukhtinskiy forestry unit Pechora-Ilych State Nature Reserve Vishera State Nature Reserve Central Forest State Nature Reserve Prioksko-Terrasnyi State Nature Reserve Gorki State Nature and History Reserve (continued)

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Table 2.1 (continued) No. Administrative region 17 Kostroma region 18 19 20 21 22 Nizhny Novgorod region 23 24 Mari El Republic 25 26 Perm region 27 Sverdlovsk region 28 Nemoral forest region 29 Bryansk region 30 Kaluga region 31 32 Tula region 33 Moscow region 34 Voronezh and Lipetsk regions 35 Voronezh region 36 Tambov region 37 38 39 Penza region 40 Chuvash Republic 41 Republic of Tatarstan 42 Samara region 43 Chelyabinsk region

Forestry unit/reserve/national park Kologrivskiy Les State Nature Reserve Mezhevskoy forestry unit Pavinskiy forestry unit Vokhomskiy forestry unit Manturovskiy forestry unit Sharyinskiy forestry unit Klenovnik Zakaznik Kilemarskiy Zakaznik Bolshaya Kokshaga State Nature Reserve Mariy Chodra National Park Basegi State Nature Reserve Visimskiy State Nature Reserve Sabarskiy Zakaznik Bryanskiy Les State Nature Reserve Ugra National Park Kaluzhskie Zaseki State Nature Reserve Krapivenskiy forestry unit Serebryanoprudskiy forestry unit Voronezh State Nature Reserve Tellerman forestry unit Gorelskiy forestry unit Prigorodnyi forestry unit Voroninskiy State Nature Reserve Privolzhskaya Lesostep State Nature Reserve Prisurskiy State Nature Reserve Volzhsko-Kamskiy State Nature Reserve Shentalinskiy forestry unit Ashinskiy forestry unit

2.2  F  orest Typology Used (Classification of Forest Vegetation) The classification of forest vegetation used in this book is based on the traditions of Russian forest phytocoenology improved with aspects of the Braun-Blanquet approach to plant community classification. In Russia, forest typology (in Forest Science) and forest vegetation classification (in Vegetation Science) are traditionally based on a dominant species approach (‘the Sukachev approach’; Sukachev and Dylis 1964), which is close to that of Cajander (1903). According to this approach, a basic unit of the classification is distinguished by lists of the dominant species of the main layers of the forest plant community:

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Fig. 2.1  Localities of the field investigations. Numbers correspond those in Table  2.1. (1) The boreal, (2) the hemiboreal and (3) the nemoral forest regions

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first of all, dominants in the forest overstorey and dominants in the forest understorey. This unit is named an association. Thus, an association in the dominance classification is usually much smaller than an association in the Braun-Blanquet classification, and application of the ‘pure’ dominance approach leads to the distinction of a huge number of classification units, which are difficult to unite in a classificatory system. As a result, a unified ‘dominance-based’ classification system of forest vegetation for European Russia was not developed. However, the forest vegetation in a number of regions (Tsinzerling 1931; Sambuk 1932; Korchagin 1940; Saburov 1972; Kozubov and Taskaev 1999; Lesa Udmurtii 1999; Lesa zemli Vologodskoy 1998, etc.) and the European Russian forest vegetation as a whole or in part (Lavrenko and Sochava 1956; Rysin 1975; Gribova et  al. 1980; Kurnaev 1980; Vasilevich 1998; Rysin and Savelyeva 2002, etc.) were described in this way. The Braun-Blanquet floristic classification method creates a clear hierarchical system of vegetation units and allows descriptions of the phytocoenological, ecological and geographical features of those vegetation units. This approach has begun to spread in Russia since the 1980s. A considerable volume of data on specific vegetation types in Russia (and the former USSR) has been analysed (e.g. for the European part of Russia: Korotkov 1991; Korotkov et al. 1991; Mirkin and Naumova 1998; Bulokhov and Solomeshch 2003; Martynenko et  al. 2008; Ermakov and Morozova 2011). However, far from all types of phytocoenoses have been described, and a full floristic classification system for the European Russian forests has not been built. Moreover, there is a severe restriction in the application of the Braun-­ Blanquet approach to a forest vegetation classification. According to this approach, the tree layer (forest overstorey) is not considered ‘a compulsory distinguishing element’ in the forest phytocoenosis, even though tree species are the ‘ecosystem engineers’ of the forest ecosystem (Jones et al. 1994, 1997) or edificatory species (in the sense of Sukachev 1928), which define the coenotic and ecological features of forest plant communities (Smirnova 1998) and thus have to be taken notice of in order to assess forest vegetation. A ‘synthetic’ dominant ecological-coenotic approach to forest vegetation classification based on the traditional dominance approach improved by aspects of the Braun-Blanquet system has been developed in Russia since the 2000s (Neshataev 2001; Zaugolnova 2008). This approach has been applied in the Coenofond of the European Russian forests (Zaugolnova and Morozova 2006, 2012; Zaugolnova and Martynenko 2014) where the typological classification of forest ecosystems is built on a comparison of dominance and floristic classifications. To simplify the description of forest vegetation in this book, we slightly modified the basic terminology proposed in the Coenofond. In this book ‘forest type’ is used as a basic unit of the forest vegetation at the regional level. Following the Coenofond, a forest type includes several associations according to the dominance classification, and it is distinguished by a combination of species groups dominating in the overstorey and in the understorey: usually it is a combination of tree species dominating in the canopy and a functional species group dominating in the ground layer. In this classification we used ‘ecological-coenotic species groups’ (ECGs) (see below) as variants of functional species groups. ‘Spruce forest with domination of

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boreal dwarf shrubs and green mosses’ (or Piceeta fruticuloso-hylocomiosa) is an example of such a forest type. Forest types which are similar in the composition of their ground layer are united in a ‘section’, and forest types which are similar in tree layer composition are united in a ‘formation’. Because of the great importance of the ECG concept in this book, we give below a definition and interpretation of this concept. Ecological-Coenotic Groups of Plant Species Following the Russian botanist Nitsenko (1969), we define an ‘ecological-­ coenotic species group’ (ECG) as a group of species that are similar in ecological features and in constancy of occurrence in vegetation communities of different types. The ecological-coenotic group concept has been often used in Russia, though variation in group specification commonly occurs (Smirnova et al. 2004). We group vascular plant species following Smirnova and Zaugolnova (Zaugolnova 2000; Smirnova et  al. 2004 and further developed by Smirnov et  al. 2006, 2008). The composition of these ecological-coenotic groups was first defined by experts and then verified by discriminant analysis and decision tree techniques using Ellenberg’s indicator values (Ellenberg et al. 1991) and species ordination scores produced by nonmetric multidimensional scaling (NMS) of several thousands of phytosociological relevés from European Russian forests. As a result of the numerical analyses, the following basic groups of vascular plants inhabiting the European Russian forests were obtained: 1. The boreal group (Br) includes species that grow in the understorey of Picea spp. and Abies sibirica forests on soils that may differ in trophic status, but with a mesic moisture regime. 2. The nemoral group (Nm) includes species that grow on rich soils in the understorey of forests of broad-leaved trees, such as Quercus robur, Tilia cordata, Ulmus spp., Acer spp. and Fraxinus excelsior. 3. The nitrophilous group (Nt) includes species growing on moist to wet sites with rich soils; they are usually species of flooded forests dominated by Alnus glutinosa. 4. The piny group (Pn) includes species growing in the understorey of pure Pinus sylvestris forests on dry and poor soils. 5. The meadow group (Md) includes species growing on wet to dry soils of different trophic statuses in non-wooded areas, such as meadows, forest edges and clear-cut areas. 6. The water-marsh group (Wt) is formed by species of coastal and water-rich habitats and mesotrophic and eutrophic bogs. 7. The oligotrophic group (Olg) is formed by plants of oligotrophic bogs and mires. For this ‘species classification’, we do not engage forests of early-successional tree species, besides Pinus sylvestris, because Betula spp., Populus tremula and Salix spp. do not have ‘characteristically dependent species’ which would not be included into the other ECGs. These tree species occupy an area after a large disturbance, and then the composition of the ground vegetation is defined by the disturbance features and by the composition of the ground vegetation before the

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disturbance event (Smirnova and Shaposhnikov 1999; Smirnova 2004). For example, abandoned agricultural lands are occupied by light-demanding grasses and forbs (plants from the meadow ECG) which remain there with the establishment and growth of Betula spp. and/or Salix spp. Populus tremula forest is often formed after selective cutting; nemoral or boreal plants, which occupied the area before the cutting, then remain in the understorey of Populus tremula forest. We except Pinus sylvestris from the other early-successional tree species because pine occupies the poorest and driest habitats, especially after numerous fires; and plants from the piny ECG mark such specific habitats (Smirnova and Shaposhnikov 1999; Zaugolnova 2000; Smirnova 2004). The numerical analysis (Smirnov et al. 2006) verified this ‘theoretical’ idea, and 1000 vascular plant species inhabiting the European Russian forests were successfully divided into the proposed basic groups. The ecological characteristics of these ECGs are illustrated by boxplots of the Ellenberg’s indicator values for these seven groups (Fig. 2.2). For sure, each group contains internal diversity; each group contains species of different life forms; they contain taller light-demanding and shorter shade-tolerant plants; there are ‘southern’ and ‘northern’ species in the pine group, etc. For the analysis of the forest vegetation in the selected forest regions, we used a set of more detailed systems of the ECGs, assessing various species characteristics. For example, for the boreal region, we distinguished groups of boreal dwarf shrubs, small herbs and ferns and tall herbs and ferns within the boreal ECG; for the nemoral region, we distinguished groups of dry meadow, fresh meadow and steppe species within the meadow ECG.  The detailed ECG systems are described in the corresponding chapters in this book where required. A full list of the ECGs can be found at the Web (Smirnov et al. 2008).

2.3  Mapping and Monitoring of Forest Cover Two main approaches have been historically used to map Russian forests: regional-­ scale vegetation mapping and aggregation of forest inventory data. The first approach was used to map and describe the state of a region’s vegetation (including the types and extent of forests) during the latter half of the twentieth century (Gribova et  al. 1980). Such maps served as a baseline for mapping the potential vegetation within European Russia (Gribova and Neykheysl 1989) and for mapping the European natural vegetation (Bohn et  al. 2000). The best-known forest map, Forest Map of the USSR (Garsia 1990), was created from fine-scale regional forest inventory maps using the second approach. Both types of maps show dominant tree species. Although these maps have been widely used for overviews of forest vegetation on a regional scale, their quality depends on ‘input data’ which may vary. Both types of maps employ regional forest inventory maps based on stepwise data integration from detailed forest stand maps produced by the Russian Forest Service. State forests are subject to a detailed ground survey every 10–12 years. It should be noted, however, that the frequency and quality of forest inventory data within

Fig. 2.2  Boxplots of the Ellenberg’s indicator values for the basic ECGs. The midline is the median, the box sides represent the lower and upper quartiles, the whiskers are the range and the circle denotes the mean. L light, F soil moisture, N soil fertility, R soil reaction, T temperature, K continentality. Br, Md, Nm, Nt, Olg, Pn, Wt – ECGs (see text)

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unmanaged remote areas of Northern European Russia are lower than those of central regions (Nilsson et al. 2000). Another aspect of forest inventory is economy-­ oriented. That means that economically important tree species are listed as dominant if they represent more than 30% of the total timber volume. As a result, forest boundaries and actual tree species compositions are not correctly reflected in parts of the regions. Moreover, none of the regional-scale forest cover maps from before the year 2000 depict recent changes in forest cover. Remotely sensed satellite data provide a practical and comparatively inexpensive solution for mapping and monitoring forest cover at the regional level. Interpretation of satellite data can be done independently by various governmental and scientific groups, focusing on different aspects of forest composition and dynamics. During the past decade, a number of satellite-based products depicting Eurasian forest cover and change have been released. Moderate spatial resolution products (with minimum mapping unit sizes of 250–1000 m) are suitable for the assessment of regional forest cover and tree species composition and may be used to track large-­ scale changes. Such products are based on data collected by moderate-resolution imaging spectroradiometer (MODIS), visible infrared imaging radiometer suite (VIIRS) and medium-resolution imaging spectrometer (MERIS) sensors. The product suite includes global land cover for the year 2000 (Bartalev et al. 2003), annually updated MODIS global land cover (Friedl et al. 2002), vegetation continuous fields (Hansen et  al. 2003) and Russia’s vegetation map based on MODIS data analysis (Bartalev et al. 2011). The combination of some of the moderate-resolution satellite-derived products with national-scale forest cover maps was used to create a country-wide overview of forest cover, type and canopy density (Bartalev et  al. 2004). Information on forest cover extent and tree canopy density was based on the vegetation continuous fields product for the year 2000 (Hansen et al. 2003). Two categories of tree canopy density were mapped separately: open canopy forests (with a tree canopy cover from 10 to 39%) and closed canopy forests (with a canopy cover of 40% and more). Dominant species and species groups are shown on the map The Forests of the USSR (Garsia 1990) except for those places where a comparison with the later land cover map of Northern Eurasia (Bartalev et  al. 2003) indicated that the species composition recently had changed. The forest map provides an overview of the extent of the current forest cover and of the dominant tree species composition over European Russia (Fig. 1.9). However, the low spatial resolution (minimum mapping unit of 1 km) of this map resulted in a considerable generalisation of the actual land cover. The insufficient spatial resolution also does not allow direct mapping of changes in forest cover as much of the disturbance within the region occurs at subpixel scales. Medium spatial resolution data (with minimum mapping units of 10–30 m), e.g. Landsat TM/ETM+/OLI imagery, do allow accurate measurement of forest cover and changes therein. From all available sources of medium-resolution satellite data, Landsat imagery stands out as the only dataset with global coverage, collected by a set of sensors with similar spectral and spatial resolution, over the last three decades. However, the use of Landsat data for regional-scale monitoring has been limited up to 2008 due to high data costs. The first region-wide satellite-based assessment of

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change in forest cover for European Russia was performed by the non-­governmental organisation Greenpeace (Yaroshenko et al. 2008) for the years 1990–2000 using freely available imagery. The same data source was also employed by experts for visual interpretation of degraded and fragmented forest areas and to map forest wildlands (Yaroshenko et  al. 2001; Potapov et  al. 2008) and their changes from 2000 to 2013 (Potapov et al. 2017). The method of intact forest mapping has been developed as a practical tool for the assessment of forest degradation and alteration at the regional-to-global levels. Landsat imagery has been used to identify and map large non-degraded areas called intact forest landscapes (IFL). An IFL was defined as an unbroken expanse of natural forest ecosystems without signs of significant human activity and a size of at least 50,000 hectares. The method produces an IFL map which shows the boundaries between unaltered forest landscapes (where most components, including species and site diversity, dynamics and ecological functions, remain intact) and altered or fragmented forests. The extent of forest alteration, which in this context is understood as a reduction in ecological integrity across a forest landscape, can then be measured at a regional level, based on the distribution and proportion of IFL areas. Boundaries between ‘intact’ and ‘non-intact’ forest landscapes are also used as a baseline for the monitoring of forest degradation. In January 2008, NASA and the US Geological Survey implemented a new Landsat data distribution policy that provides Landsat data free of charge. Recent progress in automatic Landsat data processing and mosaicking to produce cloud-­ free annual or epochal composite images opened the possibility of Landsat-based monitoring over large regions. Lately, an approach for regional-to-global-scale forest monitoring using mass processing of the Landsat archive data has been developed and implemented to estimate forest cover area and change at the global extent (Hansen et  al. 2013). While the Landsat-based forest cover mapping and change detection algorithm allowed to accurately depict present forest extent and quantification of forest change, other forest management effects, like alteration in species composition and long-term ecosystem dynamics processes, were not analysed using these methods. The availability of a four-decade satellite data archive provided the opportunity for a long-term (27 years) forest cover dynamics assessment within European Russia (Potapov et  al. 2015). Despite data limitations, especially the incomplete Landsat archive for the 1990s, the approach for the mapping of gross forest cover loss and gain events was successful and enabled the estimation of net forest cover change. Results can easily be aggregated from 30-m pixels to various national and subnational units to perform regional forest cover and change analyses and are available online (http://glad.geog.umd.edu/europe/) to serve as a baseline for further analyses of forest dynamics and its drivers.

2.4  Field Data Collection Aiming to give a more detailed analysis of the main forest types for each forest region, we describe the structure, composition, plant diversity and dynamics of the main forest types based on field data collected in the study areas. The field data, as

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a rule, included data of vegetation sample plots (phytosociological relevés), tree sample plots (ontogenetic data on tree populations) and soil morphological data. We also used spatial data on National forest inventory including general information about forest stands: stand location, stand area, tree species composition as a percentage by species (‘forest stand formula’), age classes by species, average diameter and height of tree species, stand density, stand volume, forest type and site class. The last is defined by rank values for soil moisture (from 1 to 5) and soil fertility (from A to D) according to the Vorobyev-Pogrebnyak system (Vorobyev 1953). Vegetation data sampling was usually done at temporary square plots of a fixed size (100 m2, as a rule) randomly placed within a forest type. A list of plant species with species abundance was made for each forest layer. The overstorey (or tree canopy layer) was denoted by the Latin letter A. The understorey layer (indicated by the letter B) included tree undergrowth and tall shrubs. Ground vegetation was subdivided into the layers C and D. Layer C (field layer) comprised the herbaceous species (herbs, grasses, sedges) and dwarf shrubs together with low shrubs, tree and shrub seedlings. The height of the field layer was defined by the maximal height of the herbaceous species, ferns and dwarf shrubs; the height varied from several cm to more than 200  cm in the ‘tall-herb’ forest types. Layer D (bottom layer) included cryptogamic species (bryophytes and lichens). Species abundance in each layer was usually assessed using the Braun-Blanquet cover scale (Braun-­ Blanquet 1928). The nomenclature used follows Cherepanov (1995) for vascular plants, Ignatov and Afonina (1992) for mosses and liverworts and Urbanavichjus (2010) for lichens. Additionally, for each sample plot, the following variables were assessed: total vegetation cover ratio of each forest layer, parameters of deadwood (quantity, decay stage, etc.), existence of snags, pit-and-mound topography, etc. (Smirnova et al. 2006). Also the stand’s gap-mosaic structure was registered for the studied forest types. Tree sampling was done at plots of different sizes depending on the number of tree species in a forest type. Plot area varied from 1 to 3 ha in boreal and hemiboreal forests to 3–5 ha and more in nemoral forests. Tree individuals at different ontogenetic stages were analysed (see below), the origin of trees (from seed or vegetatively) and the tree’s vitality were assessed and the age of some trees was estimated from tree cores. Soil morphology was described from soil profiles (to a depth of 2 m) and small soil pits (to a depth of 60–70 cm). Soils were classified according to the World Reference Base for Soil Resources (2006). Types and thickness of soil horizons and the presence and form of coal in the soil were registered.

2.5  Data Analysis Below we describe the main methods of data analysis used in the book. They were applied to the field data described above and collected in all three large forest regions. In each region, we additionally used other methods of data analysis and data collection which are described in the corresponding chapters.

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2.5.1  C  lassification of the Vegetation Samples and Ecological Assessment of the Forest Types Classification of the vegetation sample plot data was the first step in the data analysis. As said, we used an ecological-coenotic classification of forest vegetation where forest types are characterised by dominant tree species in the canopy and by the dominant ecological-coenotic group (ECG) in the layer of ground vegetation. Vegetation plot data were entered in a database (Smirnova et al. 2006) and then processed to define for each sample plot: (1) tree dominant(s) in the canopy layer and (2) the ECG structure of the ground vegetation. To assess the ECG structure, we calculated the number of species of different ECGs in the ground vegetation and/or the share of species of different ECGs in the total abundance (cover) of all species in that plot layer. All sample plots were allocated to groups according to their dominant canopy tree(s). These groups describe the vegetation at the level of forest formations. Then plots of each formation were allocated to forest types according to their ECG structure of the ground vegetation. Ordination diagrams were used to visualise the distances between groups: the plots were ordinated by nonmetric multidimensional scaling (NMS) using the Bray-­ Curtis distance measure (McCune and Mefford 2011). In addition, weighted averages of Ellenberg et al.’s (1991) or Landolt’s (1977; 2010) ecological indicator values for the plots were inserted as vectors on the diagrams to help interpret the axes. We also used Ellenberg’s/Landolt’s ecological indicator values for species to achieve an ecological characterisation of the forest types. Apart from the ecological indicator value, the rank value of plots was calculated as the mean ecological value of its species weighted for species abundance. Ecological estimations of a forest type were derived from ecological estimations of corresponding sample plots. Range and average ecological values for each forest type were calculated. This method of classification was described in detail by Khanina et al. (2002). Statistical analyses were performed with PC-ORD (McCune and Mefford 2011), EcoScale (Grokhlina and Khanina 2006) and SpeDiv (Smirnov 2006).

2.5.2  Plant Diversity Assessment We estimated plant diversity (alpha diversity) for each forest type by calculating total species richness of each forest type and species richness per square unit, i.e. species density sensu Hurlbert (1971). Species density was calculated as the average number of species per sample plot of fixed size within a forest type. Compared to total species richness, species density depends less on number of plots and spatial parameters of the area occupied by the forest community. Therefore we used this characteristic in a comparative analysis of the alpha diversity of forest types. Widely used species diversity indices (Shanon, Simpson, etc.) were also calculated and analysed.

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To estimate beta diversity of the forest types and the study areas, we calculated Whittaker’s indices (1960, 1972) and similarity/dissimilarity coefficients. We also estimated gamma diversity of the vegetation in the study areas by calculating the total number of plant species. The structural diversity of the vegetation was estimated by (1) the number of vegetation layers and the number of plant species per vegetation layer within the forest types, (2) the number of plant species in different life forms within each forest type and within the study areas and (3) the number of species in different ECGs in the ground vegetation.

2.5.3  A  ssessment of Forest Vegetation Dynamics According to the Ontogenetic Structure of Tree Populations To assess the dynamics of the forest vegetation, we used an earlier developed method based on the analysis of the ontogenetic structure of tree populations (Smirnova et al. 1990, 1991). We proceeded from the idea that trees are edificator species (in the sense of Braun-Blanquet and Pavillard 1925; Sukachev 1928) of forest ecosystems; they are the driving force of forest formation, the main agents in establishing and modifying the forest structure. The temporal and spatial parameters of the tree populations define the temporal and spatial parameters of the naturally developing forest vegetation (natural forest, sensu Aird 1994). So, in order to assess forest vegetation dynamics (or to predict the development of a naturally developing forest), we have to assess the composition of the tree populations, in terms of the proportions of old, mature and young individuals of different tree species. Usually, researchers analyse basal area distribution and tree diameter class or age class distribution to estimate the successional stage and/or dynamics of natural forests (e.g. Hytteborn et  al. 1991; Bernadzki et  al. 1998; Kuuluvainen et al. 1998). We propose to analyse the proportional distribution of tree individuals over ontogenetic stages (stages of biological age). The method of assessing the ontogenetic stage of tree individuals is fast and simple, and it does not require special measurements of trees. At the same time, this analysis allows the comparison of the structure of tree populations of different size classes with d­ ifferent life spans. Obtaining coherent scales of biological time for different species with different life spans is the main advantage of applying this approach (which was named ‘the concept of discrete description of the ontogeny of plant species’ and has been developed by Russian botanists since the 1950s (Rabotnov 1950, 1978; Uranov 1975; Gatzuk et al. 1980; Serebryakova 1976, 1977, 1988; White 1985; Smirnova et al. 1999; Komarov et al. 2003, etc.); they described the main principles of the concept; and for different plants they investigated life form and type of propagation, levels of vitality, peculiarities in the ontogenesis of specific species as well as features of temporal and structural diversity in the ontogenetic pathways). According to this concept, for the studied tree populations, we distinguished juvenile (j), immature (im), virginal (v), reproductive or generative (g) and senile (s)

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individuals; within the category ‘reproductive’, we distinguished between young (g1), middle-aged (g2) and old (g3) generative individuals (Figs. 2.3 and 2.4). The ontogenetic stages were defined by biomorphological features (Smirnova 1989) developed earlier according to Serebryakov’s morphological approach (Serebryakov 1962). The ontogenetic stages of tree species are as follows: Seed (se) is characterised by size and biomass, degree of embryo development, duration and type of dormancy and nutrient storage. Seedling (pl) is usually of the partially heterotrophic nutrition type, i.e. using both the substances of the maternal plant stored in the seed and its own assimilates. It usually consists of cotyledons (which may be either aerial or subterranean), primary shoot and primary root. Juvenile plant (j) usually demonstrates structural simplicity. It already lost the cotyledons, but still possesses some other embryonic structures. A juvenile tree has a small unbranched primary shoot bearing juvenile leaves or needles. Its root system consists of a primary root and few lateral ones. Plants in this stage show maximal shade tolerance. Immature plant (im) demonstrates structural peculiarities which are transitional between juvenile and mature plants. A plant begins to ramify in this stage, so its shoot system consists of branches of a low order, though its definite crown shape is not yet formed. The leaves or needles display a mature form and structure; exceptions are the species with compound leaves. The root system includes either an entire primary root or its residuals, lateral roots of second and higher orders and for some species adventitious roots. Virginal plant (v) has predominantly mature features. It is a young tree with a distinct trunk and crown. The trunk is covered only with periderm, and the branch order increases. The root system includes a taproot (or residuals of the primary root), lateral roots of several orders and adventitious roots. The plant does not produce seeds, but it has a maximal annual increment of a leader shoot. Both monopodial and sympodial trees have a crown of elongated shape with a distinct leader axis. This stage is a cardinal point in the ontogeny, because light demand increases sharply. Young reproductive plant (g1) is similar to the adult tree. The reproductive structures appear, and the seeds are located within the upper part of the crown, but the number of seeds is rather small. Tree height growth is fast, but the branching order increases relative to trees in the pre-reproductive period. The upper part of the trunk is covered with periderm, while the lower one bears a thin and smooth bark. Trees from the j to the g1 ontogenetic stages in general show a strengthening of growth processes. Mature reproductive plant (g2) demonstrates a decrease in the rate of vertical growth, while the radial increment becomes maximal. The crown and root system also reach their maximal size and maximal branching order. The bark becomes rougher and this is clearly visible on the trunk. The seeds develop in both the upper and middle parts of the crown; the number of seeds is maximal.

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Fig. 2.3  Ontogeny schemes for two dominant trees of European Russian forests for individuals with normal vitality. (a) Tilia cordata and (b) Betula pendula (Figs. by A. Shirokov)

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Fig. 2.4  Ontogeny schemes for two dominant trees of European Russian forests for individuals with normal vitality. (a) Picea abies (Fig. by A. Romanovsky) and (b) Pinus sylvestris (Fig. by O. Evstigneev)

Trees of the g2 stage show stabilisation of all parameters. A plant in this stage is strongest, but it shows already some traits of ageing: a reduction in annual increment of the lateral branches, ceasing apical growth of a few frame (skeleton) branches, opening of dormant buds, thus appearance of a secondary crown and dying off of some anchor roots. Old reproductive plant (g3) ceases its height growth, and its radial increment is very small. The size of both the crown and root system decreases because many frame branches and anchor roots already die off. The secondary crown may, in some

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cases, replace the primary one. Tree biomass is still large due to the continued increase in trunk diameter. The bark is rough and deeply fissured on both the trunk and frame branches. Seeds appear irregularly and their numbers vary. Senile plant (s) has alive shoots in the secondary crown only, and its leaves may be of the juvenile type. The upper parts of the crown and trunk are lost; the root system is being destroyed. Seeds do not appear at all. Trees of the g3 and s stages show suppressed growth. In this book, descriptions of the ontogenetic spectra of tree species in the studied forest types formed the base of our prognosis on forest vegetation dynamics measured in generations of tree populations. We classified invasive, regressive, normal and fragmentary types of tree populations (White 1985; Serebryakova 1988) and estimated corresponding future changes of tree species composition as well as temporal and structural parameters of forest vegetation dynamics for selected forest types.

2.5.4  Assessment of Successional Stages of Forest Ecosystems It is commonly known that practically the entire boreal and temperate forest area in Europe, including European Russia, has been affected by different exogenous (anthropogenic or catastrophic natural) impacts, such as cutting, ploughing, fire, storm, wind throw, etc. (Rechan et al. 1993; Smirnova 1994, 2004; Isachenko 1998; Kirby and Watkins 1998; Zaugolnova 2000; Smirnova et  al. 2001b; Bobrovsky 2002, 2010; Foster et al. 2003; Honnay et al. 2004; Rouvinen et al. 2005; Dearing et al. 2006; Gimmi et al. 2008; Evstigneev 2009; Ellis et al. 2010; Ellis 2011; Bürgi et al. 2013, 2017; Mcgrath et al. 2015, etc.). Peculiar to the Russian forests is that there are vast extensions of forested lands with large areas that differ in their degree of disturbance. We aim to use this feature to analyse forests that have been developing naturally over different time spans after large disturbances. Thus, we distinguish forest ecosystems at their early-, middle- and late-successional stages. For this purpose we assessed the following characteristics of the forest ecosystems (Smirnova et al. 2001a; Smirnova 2010): 1. The occurrence of early- and late-successional tree species and the ontogenetic structure of their populations 2. The gap-mosaic stand structure 3. The pit-and-mound topography and deadwood variables 4. The ecological-coenotic structure and diversity of the ground vegetation 5. Variables of soil morphology After a large disturbance (crown fire, clear-cutting, ploughing, etc.), the early succession begins with shade-intolerant pioneer tree species (early-successional species) starting to occupy the area (Serebryakov 1962; Halle et al. 1978; Kuusela 1990; Oldeman 1990; Smirnova 1994, 2004; Smirnova and Shaposhnikov 1999;

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Schnitzler and Closset 2003; Nishimura 2006; etc.). In the European part of Russia, this first group of species consists of light-coniferous species (Pinus sylvestris, Larix sibirica) and small-leaved deciduous species (Betula spp., Populus tremula, Alnus incana, Salix spp.). At the middle stage of succession, the first generation of early-successional species is being replaced by the first, and then the second generations of shade-tolerant (late-successional) species. Depending on the climatic zone, this second group consists of dark-coniferous (Picea spp., Abies sibirica) and/or broad-leaved deciduous species (Tilia cordata, Fraxinus excelsior, Ulmus spp., Acer spp., Quercus robur). We consider that the forest ecosystem enters its late-­ successional stage when the ontogenetic structure of the populations of late-­ successional tree species appears stable and the number of late-successional species particular for the region has reached its maximum. As the generations of trees replace each other, a pit-and-mound topography develops together with a gap-mosaic stand structure (Yamamoto 1981, 1992, 2000; Hytteborn et  al. 1987, 1991; Kuuluvainen 1994; Keddy and Drummond 1996; Smirnova 1994, 2004, 2010; Smirnova and Shaposhnikov 1999; Fischer et al. 2013; Král et al. 2014, etc.). Dead and dying trees strongly influence the structural diversity of the stand as a result of snags and fallen logs and the development of a pit-­ and-­mound topography as a result of tree falls with uprooting (Skvortsova et  al. 1983; Dyrenkov 1984; Keddy and Drummond 1996; Ulanova 2000; Muscolo et al. 2014). Gaps in a forest canopy, resulting in lighter patches, are formed when groups of trees, or even single large old trees, are falling (Yamamoto 1981, 1992, 2000; Hibbs 1982; Hytteborn et al. 1991; Smirnova 1994; Kern et al. 2012; Mitchell 2012; Lobo and Dalling 2013, etc.). We consider that a forest ecosystem is in its early-­ successional stage when the structural features listed above are absent or when one finds only solitary snags and fallen logs from the early-successional tree species. A forest ecosystem is considered at its mid-successional stage when there are newly formed gaps in the canopy, as well as ‘young’ snags (that not yet started to decompose), fallen logs and pits and mounds as a result of uprooted trees of both earlyand late-successional species. And, finally, we consider a forest ecosystem close to its late-successional stage when the full set of above-mentioned structural features at different stages of decay and erosion is found, formed by different tree species, including late-successional ones. Deadwood at different stages of decay, pits and mounds resulting from different species of uprooted trees and in different stages of erosion and canopy gaps of different size and age all create microsites with different ecological properties, different sizes and durations. These microsites provide possibilities for the establishment of different species (e.g. Nakashizuka 1989; Spies and Franklin 1989; Kuuluvainen and Juntunen 1998; Ulanova 2000; Wohlgemuth et  al. 2002; Kuuluvainen and Kalmari 2003; Peterson 2004; von Oheimb et al. 2007; Vodde et al. 2011; Smirnova et  al. 2011). We consider that the occurrence of plant species from the different ecological-coenotic groups (see above) and a high level of species diversity, as a result of a strong structural diversity of the forest, show that the forest is in its late-­ successional stage. But we want to point out that in a forest dominated by late-­ successional tree species and with well-developed gaps, tree-fall mosaics and a

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pit-and-mound topography, there appear microsites suitable for the establishment and further development of early-successional tree species (Smirnova 2004; Vodde et  al. 2011, etc.). So, the presence of early-successional tree species in a forest dominated by late-successional tree species can be considered as an additional sign of the late-successional stage of the forest. Input of soil morphological parameters into the diagnosis of the successional stages of the forest ecosystems is dealt with in detail below. Here, we only want to remark that the soil keeps traces of exogenous impacts on the ecosystem as well as traces of tree falls with uprooting for a longer period of time than plants and the structure of the forest ecosystem do. We try to use this feature of the soil to assess the history of the forests (Bobrovsky 2010).

2.6  Conclusion The methods described above are used below to analyse the vegetation in the three major forest regions, the vegetation in the floodplains and the total forest cover dynamics during the last 30 years in the area of European Russia.

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Potapov P, Hansen MC, Laestadius L, Turubanova S, Yaroshenko A, Thies C, Smith W, Zhuravleva I, Komarova A, Minnemeyer S, Esipova E (2017) The last frontiers of wilderness: tracking loss of intact forest landscapes from 2000 to 2013. Sci Adv 3(1):e1600821. doi:10.1126/ sciadv.1600821 Rabotnov TA (1950) Zhiznennye tsikly mnogoletnikh travyanistykh rasteniy v lugovykh tsenozakh. Trudy Botanicheskogo instituta AN SSSR 3:7– 204 – The life cycles of perennial herbaceous plants in meadow communities Rabotnov TA (1978) On coenopopulations of plants reproducing by seeds. In: Freysen AHJ, Woldendorp JW (eds) Structure and functioning of plant population, Amsterdam, pp 1–26 Rechan SP, Malysheva TV, Abaturov AV, Melanholin NP (1993) Lesa Severnogo Podmoskovya. Izd-vo Nauka, Moscow, 316 pp – Forest in the north of the Moscow region Rouvinen S, Rautiainen A, Kouki J (2005) A relation between historical forest use and current dead woody material in a boreal protected old-growth forest in Finland. Silva Fenn 39(1):21–36 Rysin LP (1975) Sosnovye lesa Evropeyskoy chasti SSSR. Izd-vo Nauka, Leningrad, 212 pp – Pinus sylvestris forest in the European part of the USSR Rysin LP, Savelyeva LI (2002) Elovye lesa Rossii. Izd-vo Nauka, Moscow, 225 pp – Picea spp. forests in Russia Saburov DN (1972) Lesa Pinegi. Izd-vo Nauka, Leningrad, 173 pp – Forests in the Pinega River basin Sambuk FV (1932) Pechorskie lesa. Trudy Botanicheskogo muzeya AN SSSR 24:63–250 – Forests in the Pechora River basin Schnitzler A, Closset D (2003) Forest dynamics in unexploited birch (Betula pendula) stands in the Vosges (France): structure, architecture and light patterns. For Ecol Manag 183:205–220 Serebryakov IG (1962) Ekologicheskaya morfologiya rasteniy. Zhiznennye formy pokrytosemennykh i khvoinykh. Izd-vo Vysshaya shkola, Moscow, 378 pp – Ecological morphology of plants. Life forms of angiosperms and conifers Serebryakova TI (ed) (1976) Cenopopulyatsii rasteniy (osnovnye ponyatiya i struktura). Izd-vo Nauka, Moscow, 216 pp – Coenopopulations of plants: the main terms and structure Serebryakova TI (ed) (1977) Cenopopulyatsii rasteniy. Razvitie i vzaimootnosheniya. Izd-vo Nauka, Moscow, 134 pp – Coenopopulations of plants. Development and relationships Serebryakova TI (ed) (1988) Cenopopulyatsii rasteniy (ocherki populyatsionnoy biologii). Izd-vo Nauka, Moscow, 183 pp – Coenopopulation of plants. Essays on population biology Skvortsova EB, Ulanova NG, Basevitch VF (1983) Ekologicheskaya rol vetrovalov. Izd-vo Lesnaya promyshlennost, Moscow, 192 pp – The ecological value of windthrows Smirnov VE (2006) Spediv – programma dlya analiza ranoobraziya rastitelnosti. In: Zhukova LA (ed) Principy i sposoby sokhraneniya bioraznoobraziya. Materialy II Vserossiyskoy nauchnoy konferentsii. Izd-vo MarGU, Joshkar-Ola, pp 142–143 – Spediv, software for plant diversity analysis Smirnov VE, Khanina LG, Bobrovsky MV (2006) Obosnovanie sistemy ekologo-tsenoticheskikh grupp vidov rasteniy lesnoy zony Evropeyskoy Rossii na osnove ekologicheskikh shkal, geobotanicheskikh opisaniy i statisticheskogo analiza. Bull MOIP, otd. Biologicheskiy 111(2): 36–47 – Validation of ecological-coenotic groups of plant species in European Russian forests: statistical analysis of species indicator values and geobotanical relevés Smirnov VE, Khanina LG, Bobrovsky MV (2008) Validation of the ecological-coenotic groups of vascular plants for European Russian forests on the basis of ecological indicator values, vegetation releves and statistical analysis. URL: http://www.impb.ru/index.php?id=div/lce/ ecg&lang=eng Smirnova OV (ed) (1989) Diagnozy i klyuchi vozrastnykh sostoyaniy lesnykh rasteniy. Derevya i kustarniki. Izd-vo Prometey MGPI im. V.I. Lenina, Moscow, 105 pp – Diagnosis and keys of age states of forest plants. Trees and shrubs Smirnova OV (ed) (1994) Vostochnoevropeyskie shirokolistvennye lesa. Izd-vo Nauka, Moscow, 363 pp – East-European broad-leaved forests Smirnova OV (1998) Populyatsionnaya organizatsiya biocenoticheskogo pokrova lesnykh landshaftov. Uspekhi sovremennoy biologii 118(2):148–165 – Population organization of ecosystems in forest landscapes

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Smirnova OV (ed) (2004) Vostochnoevropeyskie lesa: istoriya v golocene i sovremennost. Izd-vo Nauka, Moscow, vol 1, 479 pp; vol 2, 575 pp – East-European forests: the Holocene history and the current state Smirnova OV (2010) Otsenka suktsessionnogo sostoyaniya lesnykh ekosistem. In: Zaugolnova LB, Braslavskaya TYu (eds) Metodicheskie podkhody k ekologicheskoy otsenke lesnogo pokrova v basseyne maloy reki. Izd-vo KMK, Moscow, pp 189–194 – Estimation of the succession stage of forest ecosystems Smirnova OV, Shaposhnikov ES (eds) (1999) Successionnye processy v zapovednikakh Rossii i problemy sokhraneniya biologicheskogo rasnoobraziya. Russkoe botanicheskoe obshchestvo, SPb, 549 pp – Successions in the Russian Nature reserves and the challenge of biodiversity conservation Smirnova OV, Chistyakova AA, Popadyuk RV, Evstigneev OI, Korotkov VN, Mitrofanova MV, Ponomarenko EV (1990) Populyatsionnaya organizatsiya rastitelnogo pokrova lesnykh territoriy (na primere shirokolistvennykh lesov Evropeyskoy chasti SSSR). Izd-vo ONTI PNTs RAN, Pushchino, 92 pp – Population organization of the vegetation cover in forested areas (with an example of broad-leaved forests in the European part of the USSR) Smirnova OV, Voznyak RR, Evstigneev OI, Korotkov VN, Nosach NYa, Popadyuk RV, Samoylenko VK, Toropova NA (1991) Populyatsionnaya diagnostika i prognozy razvitiya zapovednykh lesnykh massivov (na primere Kanevskogo zapovednika). Botanichesky zhurnal 76(6):68–79 – Population diagnostics and forecasts for the development of protected forest areas (with the example of the Kanev State Nature Reserve, Ukraine) Smirnova OV, Chistyakova AA, Zaugolnova LB, Evstigneev OI, Popadiouk RV, Romanovsky AM (1999) Ontogeny of a tree. Botanichesky zhurnal 12:8–20 Smirnova OV, Bobrovsky MV, Khanina LG (2001a) Otsenka i prognoz suktsessionnykh processov v lesnykh tsenozakh na osnove demograficheskikh metodov. Bull. MOIP, otd. Biologicheskiy 106(5):25–33 – Estimation and forecast of succession processes in forest coenoses on the basis of demographic methods Smirnova OV, Turubanova SA, Bobrovsky MV, Korotkov VN, Khanina LG (2001b) Rekonstruktsiya istorii lesnogo poyasa Vostochnoy Evropy i problema podderzhaniya biologicheskogo raznoobraziya. Uspekhi sovremennoy biologii 2:144–159 – Reconstruction of the history of the forest belt in Eastern Europe and the challenge of maintenance of biological diversity Smirnova OV, Khanina LG, Smirnov VE (2004) Ekologo-tsenoticheskie gruppy v rastitelnom pokrove lesnogo poyasa Vostochnoy Evropy. In: Smirnova OV (ed) Vostochnoevropeyskie lesa: istoriya v golocene i sovremennost, vol 1. Izd-vo Nauka, Moscow, pp 165–175 – Ecologicalcoenotic groups in the forest vegetation cover of Eastern Europe Smirnova O, Zaugolnova L, Khanina L, Braslavskaya T, Glukhova E (2006) FORUS – database on geobotanic relevés of European Russian forests. In: Lakhno VD (ed) Mathematical biology and bioinformatics. Izd-vo MAX Press, Moscow, pp 150–151. URL: http://www.impb.ru/pdf/ FORUS_SmirnovaKhanina.pdf Smirnova OV, Aleynikov AA, Semikolennykh AA, Bovkunov AD, Zaprudina MV, Smirnov NS (2011) Prostranstvennaya neodnorodnost pochvenno-rastitelnogo pokrova temnokhvoinykh lesov v Pechoro-Ilychskom zapovednike. Lesovedenie 6:67–78 – Spatial heterogeneity of soil and vegetation in dark coniferous forests in the Pechora-Ilych State Nature Reserve Spies TA, Franklin JF (1989) Gap characteristics and vegetation response in coniferous forests of the Pacific northwest. Ecology 70:543–545 Sukachev VN (1928) Rastitelnye soobshhestva (vvedenie v fitosotsiologiyu). Izd-vo Kniga. Moscow-Leningrad, 232 pp – Vegetation communities. Introduction to phytosociology Sukachev VN, Dylis NV (1964) Fundamentals of forest biogeocoenology. Oliver and Boyd, Edinburgh Tsinzerling YuD (1931) Geografiya rastitelnogo pokrova severo-zapada Evropeyskoy chasti SSSR. Trudy Geomorfologicheskogo instituta AN SSSR 4:7–377 – Geography of the vegetation cover in the north-west of the European part of the USSR Ulanova NG (2000) The effects of windthrow on forest at different spatial scales: a review. For Ecol Manag 135:155–167

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Uranov AA (1975) Vozrastnoy spektr tsenopopulyatsiy kak funktsiya vremeni i energeticheskikh volnovykh processov. Biologicheskie nauki 2:7–34 – Age spectrum of phytocoenopopulations as a function of time and energy wave processes Urbanavichjus GP (ed) (2010) Spisok likhenoflory Rossii. Izd-vo Nauka, SPb, 294 pp – A checklist of the lichen flora of Russia Vasilevich VI (1998) Seroolshatniki Evropeyskoy Rossii. Botanichesky zhurnal 83(8):28–42  – Alnus incana forests in European Russia Vodde F, Jogiste K, Kubota Y, Kuuluvainen T, Koster K, Lukjanova A, Metslaid M, Yoshida T (2011) The influence of storm-induced microsites to tree regeneration patterns in boreal and hemiboreal forest. J For Res 16:155–167 von Oheimb G, Friedel A, Bertsch A, Härdtle W (2007) The effects of windthrow on plant species richness in a central European beech forest. Plant Ecol 191:47–65 Vorobyev DP (1953) Tipy lesov Evropeyskoy chasti SSSR.  Izd-vo AN USSR, Kiev, 452  pp  – Forest types in the European part of the USSR White J (ed) (1985) The population structure of vegetation. Handbook of vegetation science. Part 3. Dr. W. Junk Publishers, Dordrecht/Boston/Lancaster, 369 pp Whittaker RH (1960) Vegetation of the Siskiyou Mountains, Oregon and California. Ecol Monogr 30:279–338 Whittaker RH (1972) Evolution and measurement of species diversity. Taxon 21:213–251 Wohlgemuth T, Kull P, Wüthrich H (2002) Disturbance of microsites and early tree regeneration after windthrow in Swiss mountain forests due to the winter storm Vivian 1990. For Snow Landsc Res 77:17–48 World Reference Base for Soil Resources (2006) World Soil Resource Reports No. 103. FAO, Rome Yamamoto S (1981) Gap phase dynamics in climax forests. Biol Sci (Tokio) 33:8–16 Yamamoto S (1992) Gap characteristics and gap regeneration in primary evergreen broad-leaved forests of western Japan. Bot Mag (Tokyo) 105:29–45 Yamamoto S (2000) Forest gap dynamics and tree regeneration. J For Res 5:223–229 Yaroshenko AY, Potapov PV, Turubanova SA (2001) The last intact forest landscapes of northern European Russia. Greenpeace Russia, Moscow, URL: ­http://www.intactforests.org/pdf.publications/The.Last.IFL.of.European.Russia.2001.pdf Yaroshenko AYu, Dobrynin DA, Egorov AV, Zhuravleva IV, Manisha AE, Potapov PV, Turubanova SA, Khakimulin YeV (2008) Lesa centra i severa Evropeyskoy Rossii. Karta 1:4500000. Greenpeace Russia, Moscow – Forests of the center and the north of European Russia. Map 1:4,500,000 Zaugolnova LB (ed) (2000) Otsenka i sokhranenie bioraznoobraziya lesnogo pokrova v zapovednikakh Evropeyskoy Rossii. Izd-vo Nauchnyi Mir, Moscow – Assessment and conservation of forest biodiversity in the European Russian reserves Zaugolnova LB (2008) Podkhody k otsenke tipologicheskogo raznoobraziya lesnogo pokrova. In: Isaev AS (ed) Monitoring biologicheskogo raznoobraziya lesov Rossii: metodologiya i metody. Izd-vo Nauka, Moscow, pp 36–58 – Approaches to the assessment of typological diversity of forest cover Zaugolnova LB, Martynenko VB (2014) Opredelitel tipov lesa Evropeyskoy Rossii. URL: http:// www.cepl.rssi.ru/bio/forest/index.htm – Guide to the forest types in European Russia Zaugolnova LB, Morozova OV (2006) Tipologiya i klassifikatsiya lesov Evropeyskoy Rossii: metodicheskie podkhody i vozmozhnosti ikh realizatsii. Lesovedenie 1:34–48 – Typology and classification of forests in European Russia: methodological approaches and their feasibility Zaugolnova LB, Morozova OV (2012) Coenofond lesov Evropeiskoy Rossii. URL: http://www. cepl.rssi.ru/bio/flora/index.htm – Coenofond of forests in European Russia

Chapter 3

Boreal Forests O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, L.B. Zaugolnova, V.N. Korotkov, A.A. Aleynikov, O.I. Evstigneev, V.E. Smirnov, N.S. Smirnov, and M.V. Zaprudina

Abstract  Researches of forest vegetation, forest soil, and features of the historical land use in the boreal region showed that most of the boreal forests have developed as a result of repeated forest fires and cuttings during the last millennium. These impacts simplified the structure of boreal forests and led to the wide occurrence of O.V. Smirnova (*) • L.B. Zaugolnova • A.A. Aleynikov (*) • M.V. Zaprudina Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia e-mail: [email protected]; [email protected] M.V. Bobrovsky (*) Institute of Physico-Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] L.G. Khanina (*) Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] V.N. Korotkov (*) Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia e-mail: [email protected] O.I. Evstigneev Bryanskiy Les (Bryansk Forest) State Nature Biosphere Reserve, Nerussa, Bryansk region, Russia V.E. Smirnov Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia N.S. Smirnov Pechora-Ilych State Nature Biosphere Reserve, Yaksha, Komi Republic, Russia Institute of Global Climate and Ecology of Roshydromet and the Russian Academy of Sciences, Moscow, Russia © Springer Science+Business Media B.V., part of Springer Nature 2017 O.V. Smirnova et al. (eds.), European Russian Forests, Plant and Vegetation 15, https://doi.org/10.1007/978-94-024-1172-0_3

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forests dominated by green mosses and dwarf shrubs in the ground layer of the vegetation with a relatively low species diversity and the prevalence of soil with moor and moor-moder humus horizons. At the same time forests dominated by tall herbaceous species in the ground layer and moder-mull humus in the soil have been found in fire refuges which are located in river valleys and on watersheds as well. Tall herb forests dominated by Picea spp. and Abies sibirica (in the east) have developed in areas without fire and clear-cuttings for more than 500 or 600 years, and they are the richest forest type in terms of species and structural diversity of the vegetation, in phytomass values of the ground layer, and in soil fertility. Treefalls with uprooting, pit-and-mound topography, and deadwood at different stages of decay and overgrowing are the main features of these forests. Dark coniferous forests dominated by tall herbs in the ground layer are forests at the latest successional stage that we observed in the boreal forest region of European Russia.

3.1  P  rodromus of the Vegetation and Forest Distribution in the Boreal Region The description of the boreal forests is based on the Coenofond of the European Russian forests (Zaugolnova and Morozova 2006, 2012; Zaugolnova 2008; Zaugolnova and Martynenko 2014). The structure and principles of the Coenofond are described in Sect. 2.2. Forests are classified into sections and subsections according to their vegetation structure and composition of the field layer of the forest ecosystem; forest types are further described within subsections according to the dominance of their tree layer. The distribution of the forest types is also given.

3.1.1  Section: Lichen Forests The diagnostic feature of these forests is the domination of bushy lichens in the ground layer. In the overstorey, lichen forests can be dominated by light coniferous trees, small-leaved deciduous trees, or dark coniferous trees. The distribution of these forests is defined by the geology and relief of the area and, to a great extent, by the fire disturbance regime. Lichen forests with widest occurrences in European Russia are classified into the following associations distinguished by the Braun-Blanquet approach: Flavocetrario nivalis–Pinetum Morozova in Morozova et  al. 2008, Cladonio arbusculae–­ Pinetum boreale (Caj. 1921) K.-Lund 1967, and Empetro–Piceetum obovatae (Sambuk 1932) Morozova comb. nov. 2008. The association C.a.–P.b. includes three subassociations: C.a.–P.b. typicum K.-Lund 1967, C.a.–P.b. vaccinietosum myrtilli Morozova and Korotkov 1999, and C.a.–P.b. pulsatilletosum patentis Saburov 1972 in Morozova et al. 2008. We distinguish two subsections within the lichen forest section: the genuine lichen forests and the lichen – green moss forests.

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Subsection of genuine lichen forests includes plant communities of the association Flavocetrario nivalis–Pinetum Morozova in Morozova et al. 2008 and subassociation C.a.–P.b. typicum K.-Lund 1967. Forests of the Flavocetrario nivalis–Pinetum have been recorded only in the north of the European Russian boreal region both in its western and eastern parts. The subassociation C.a.–P.b. typicum K.-Lund 1967 occurs over the entire boreal region but mostly in the south. Bushy lichens absolutely prevail over green mosses in the bottom layer of these forests; the participation of dwarf shrubs and herbs in the ground layer is insignificant. Pinus sylvestris mainly dominates in the overstorey, Betula pubescens and Picea spp. are much less common, and Larix sibirica and Pinus sibirica occur very rarely and only in the eastern part of the area. Al-Fe-humic podzols, mostly Haplic Podzols on well-drained sites with coarse-textured deposits, are common in the genuine lichen forests. Genuine lichen pine forests (Pineta sylvestris cladinosa) make up the largest part of the lichen forests. These forests occur commonly in the rocky landscapes of Karelia and the Kola Peninsula (Morozova and Korotkov 1999; Neshataev and Neshataeva 2002; Morozova et al. 2008; Kucherov and Zverev 2012); they are also common in the middle part of Finland (Oksanen and Ahti 1982). Other tree species cannot successfully compete with Pinus sylvestris under the rigorous environmental conditions of high insolation and poorness of soil on coarse-textured substrates. Sparse forest stands have a low site productivity quality (in Russian “bonitet”) (site classes 5 and 5a). A shrub layer is typically absent. Lichens (Cladonia alpestris, C. rangiferina, Cetraria islandica) dominate the ground layer; the very sparse field layer is usually formed by Arctostaphylos uva-ursi, Empetrum hermaphroditum or E. nigrum, and Calluna vulgaris (Morozova and Korotkov 1999). Besides on rocky substrate, pine successfully grows in vast areas of well-drained sandy sediments at the tops and slopes of hills, esker ridges, river terraces, lake swells of moraine plains, etc.; Pinus sylvestris dominates in the overstorey with an admixture of Betula pubescens. Here the site productivity quality is usually higher (site classes 3 and 4) than on rocky substrate, and the maximum tree ages and sizes vary greatly depending on the actual ecological conditions and the fire regime. Sometimes one can find uneven-aged stands with 600-year-old pines with fire scars (Smirnova and Korotkov 2001); such stands document the long duration of periods between fires. In the undergrowth, Pinus sylvestris, and rarely Betula pubescens and Salix caprea, can be found in small amounts. In the shrub layer, Sorbus gorodkovii (in the western part of the area), S. aucuparia, Juniperus communis, and Rosa acicularis (in the central and the eastern parts) occur sparsely. In the sparse field layer, Vaccinium vitis-idaea, V. myrtillus, Empetrum hermaphroditum, and E. nigrum dominate. The abundance of Arctostaphylos uva-ursi and Calluna vulgaris increases on sites affected by ground fires where a tree layer is sparse. Avenella flexuosa, Chamaenerion angustifolium, and Melampyrum pratense also occur sporadically. The cover of the lichens reaches 80–90%. The bushy lichens Cladonia stellaris, C. arbuscula, C. rangiferina, and C. uncialis prevail in the bottom layer; Cetraria islandica and Polytrichum piliferum are also constantly present, but moss cover is low (Saburov 1972; Morozova and Korotkov 1999).

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In all localities of the genuine lichen pine forests, the typical soils are Haplic Podzols. The thickness of a slightly decomposed organic horizon is usually small: 1–2 cm while that of a podzolic horizon can vary from a few centimeters (“dwarf podzols”) to 10 cm and more (Morozova 1991; Nikonov 1987). Rustic Podzols and Lithic and Haplic Leptosols also occur. These forest ecosystems are the initial stage of succession after a forest fire. The permanent presence of these communities in the modern forest cover is maintained by recurrent fires which easily start at the dry forest floor owing to human carelessness with fire. Genuine lichen larch forests (Lariceta cladinosa) were described from the foothills of the Northern Urals at the upper forest limit (Korchagin 1940; Martynenko 1999a; Kucherov and Zverev 2011). Larch forests grow on more fine-textured substrates than pine forests. Typical soils are slight podzols (dwarf podzols) on sandy or rocky substrates or podzolic soils (Albeluvisols) on carbonaceous clay loams (Korchagin 1940; Martynenko 1999a). The sparse tree layer consists of Larix sibirica, sometimes with an admixture of Betula pubescens and Picea obovata. The site quality class is low (5 and 5a). The scanty undergrowth consists of the same species that grow in the overstorey. The shrub layer consists of a few individuals of Juniperus communis, Sorbus aucuparia, and Rosa acicularis; the tundra shrub Betula nana occurs only in the northernmost communities. The cover of the field layer is 20–50%. Oligotrophic and piny dwarf shrubs (Empetrum nigrum, Vaccinium uliginosum, and V. vitis-idaea) are the most abundant, and Arctic-Alpine species, such as Arctous alpina, Dryas punctata, and Hierochloe aplina, also occur. Lichen cover is more than 70%; Cladonia stellaris and C. arbuscula dominate, Stereocaulon paschale occurs in the mountains. Polytrichum piliferum prevails among the mosses. Genuine lichen birch forests (Betuleta cladinosa) are found up to a height of 400 m above sea level in the Khibiny Mountains in the west and in the piedmont plain of the Urals in the east (Laschenkova 1954; Sambuk and Zhurbenko 1986; Degteva 1999, 2001; Neshataev and Neshataeva 1993a; Morozova et al. 2008). In the Kola Peninsula, the sparse tree layer consists of Betula pubescens (8–12 m in height) with an admixture of Picea abies in areas where no fires have been recorded since more than 30 (29–60) years (Pushkina 1960). Stand quality is low. Juniperus communis, Salix phylicifolia, and sometimes Betula nana occur in the understorey with different abundances. The cover of the field layer is 20–30%; it is formed by Vaccinium vitis-idaea, Empetrum nigrum, Arctostaphylos uva-ursi, Avenella flexuosa, Festuca ovina, and Antennaria dioica. Lichens cover 90% or more; the bushy lichens Cladonia stellaris, C. arbuscula, and Cetraria islandica dominate (Neshataev and Neshataeva 1993a). Genuine lichen Siberian pine forests (Pineta sibiricae cladinosa) are known from the mountains and foothills of the Urals, on steep rocky slopes near the upper forest limit at elevations of 300–500 m asl (Korchagin 1940; Martynenko 1999b). Pinus sibirica (up to 10–15  m in height and 16–30  cm in diameter) composes 50–80% of the overstorey; Picea obovata and Betula pubescens also occur. Site productivity quality is low (site classes 5 and 5a). The understorey is poorly devel-

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oped and consists of a few individuals of Sorbus aucuparia, Rosa acicularis, and Betula nana. The undergrowth is composed of Picea obovata, Pinus sibirica, Betula pubescens, and sometimes of a dwarf form of Abies sibirica. The field layer covers up to 70% and is dominated by Vaccinium myrtillus with an admixture of V. vitisidaea, Empetrum nigrum, and Ledum palustre. The bushy lichens Cladonia stellaris, C. arbuscula, Cetraria islandica, etc. compose 70–100% of the bottom layer. Among the mosses Pleurozium schreberi more often occurs (Martynenko 1999b). Genuine lichen spruce forests (Piceeta cladinosa) occur quite rarely and only in the north of the boreal region. They are found on tops and slopes of hills and slopes of terraces with a good drainage, on rocky, sandy-gravelly, or sandy substrates (Söderström 1988; Arseneault and Payette 1992; Esseen et al. 1997). Soils are Haplic Podzols and also Haplic Leptosols in the mountains. Picea abies dominates in the sparse overstorey with a permanent admixture of Pinus sylvestris (in the Kola Peninsula). Betula pubescens and B. tortuosa are also frequent. Total crown cover does not exceed 30%. Picea abies, Betula pubescens, and sometimes Pinus sylvestris form the undergrowth. Cover of the shrub layer is 5–10%; it consists of Juniperus communis and rarely of Betula nana. Dominants in the field and bottom layers are the same as in the genuine lichen pine forests described from the far north of the region and which belong to the Flavocerario nivalis–Pinetum association. The origin of the lichen spruce forests is unclear; probably they developed on places of reindeer herding in the Kola Peninsula and in Norway (Holien 1996). Characteristic for the Subsection of lichen—green moss forests is that in these forests, the cover of lichens is not more than 50%, while the cover of green mosses in the bottom layer is correspondingly higher. The abundance of boreal dwarf shrubs and herbs in the field layer is higher; Picea spp. is more frequent in the overstorey in comparison with forests described in the previous subsection. Soils are the same as in the genuine lichen forests: Haplic Podzols are common; Rustic Podzols also occur (Gerasimova 1987). Plant communities of this subsection are classified in the association Empetro–Piceetum obovatae (Sambuk 1932) Morozova comb. nov. 2008 and the subassociation C.a.–P.b. vaccinietosum myrtilli Morozova and Korotkov 1999. Lichen – green moss pine forests (Pineta sylvestris hylocomioso-cladinosa) are widely distributed in the boreal region of European Russia (Neshataev and Neshataeva 1993b, 2002; Korotkov et  al. 1999; Morozova and Korotkov 1999; Gromtsev 2002; Kucherov 2013a); they are also common in mid-Finland (Oksanen and Ahti 1982). The cover of the overstorey varies in the lichen – green moss pine forests. The site quality scores are usually higher than in the pine forests of the previous subsection. The abundance of Vaccinium vitis-idaea and V. myrtillus is higher; evergreen species of Pyrola and Lycopodium as well as deciduous small boreal herbs and ferns (Trientalis europaea, Gymnocarpium dryopteris, and others) occur. Undergrowth of Picea abies (in the west) or Picea obovata (in the center and in the east), Betula pubescens, and Salix caprea is common and usually with the higher density than in the genuine lichen pine forests; Abies sibirica appears rarely in the undergrowth in the east.

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The occurrence of forests with lichens and forests with lichens and green mosses within the same relief position and on the same substrates, as well as observations on the post-fire development of pine forests in Nature Reserves, allows us to conclude that, away from rocky areas, lichen and moss-lichen pine forests represent the initial succession stages of recovery of dark coniferous forests after fire (Kuleshova et al. 1996; Korotkov et al. 1999; Gorshkov and Stavrova 2002; Korotkov 2004) (see Sect. 3.3 for more details). It has also been shown that in the north of European Russia, dominance of Vaccinium vitis-idaea and lichens in the ground layer of pine forests was maintained by periodic fires (every 8–12 years) ignited by local people to rejuvenate cowberries (Vaccinium vitis-idaea) with the purpose to obtain larger crops of berries in a cycle of traditional land use (Korchagin 1940) that has now disappeared. Lichen  – green moss spruce forests (Piceeta hylocomioso-cladinosa) were described from the far north of the boreal region in the Kola Peninsula, from North Karelia (Rysin and Savelyeva 2002), from the White Sea – Kuloy plateau (Leontyev 1935), and from along the tributaries of the Pechora River (Martynenko 1999b). They grow on poor, dry, and well-drained soils. Tree stand density is medium (0.4– 0.6); site productivity quality is low (site classes 5–5a). Betula pubescens, Pinus sylvestris, and Larix sibirica (in the east) are always present in the overstorey as an admixture to the Picea spp. The shrub layer is very sparse and consists of individuals of Juniperus communis, Sorbus aucuparia, and Rosa acicularis. Regeneration of Picea abies in the west and Picea obovata in the east is poor. The composition of the ground layer is similar to the one in the pine forests of this subsection: Cladonia stellaris, C. arbuscula, C. rangiferina, etc. form up to 60% of the bottom layer, and mosses as Pleurozium schreberi and rarely Polytrichum commune make up 40% of the cover. As a result, these plant communities occupy an intermediate position in the classification schemes: they have features of the subassociation C.a.–P.b. vaccinietosum myrtilli (Morozova and Korotkov 1999) and the association Flavocetrario nivalis–Pinetum (Morozova in Morozova et al. 2008). Lichen – green moss larch forests (Lariceta hylocomioso-cladinosa) are floristically similar to the pine forests of this subsection; their diversity in composition and structure of the vegetation is higher than in the lichen – green moss spruce forests. Lichen – green moss larch forests occur on spurs of the Timan Ridge, in the middle reaches of the Pechora River and along its tributaries, in the north of the Arkhangelsk region (along the Pinega River), and in the Nether Polar Ural (Yugyd Va National Park) (Saburov 1972; Martynenko 1999a; Morozova et  al. 2008; Kucherov and Zverev 2011). At the watershed plateau and on the mountain slopes, these forests mainly grow on carbonates. On watersheds they develop after fires in the absence of seed drift of Pinus sylvestris. On steep slopes with moving stones, Larix sibirica is the tree species that seems best able to grow on the bare substrates. Typical soils are Haplic and Rustic Podzols and also Albeluvisols. The overstorey is composed of Larix sibirica with a small admixture of Betula pubescens, Pinus sylvestris, or Populus tremula. Crown cover of the overstorey varies vastly; stands usually score site classes 3 and 4 which is higher than those of the forest stands of the Lariceta cladinosa and Piceeta hylocomioso-cladinosa. Without fires Picea obovata gradually achieves dominance in the undergrowth that can be

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well developed and can form the second tree layer in a forest canopy. Betula pubescens can also occur in the understorey. The shrub layer is composed of sparse individuals of Sorbus aucuparia, Lonicera pallasii, Rosa acicularis, Juniperus communis, or Rubus idaeus; of these only Juniperus communis grows in the Ural Mountains. In the north of the boreal region, a thick understorey with 70% coverage can be formed by Betula nana, Juniperus communis, and Salix spp., while in these forests on slopes, a shrub layer is usually poorly developed. Cover of the field layer is 50–70%; the structure of the layer is irregular. Vaccinium myrtillus, V. vitis-idaea, and Empetrum nigrum can occur as dominants. Avenella flexuosa and Linnaea borealis occur with high constancy. Maianthemum bifolium, Oxalis acetosella, and Trientalis europaea also occur on the Timan Ridge. On the watersheds, dwarf shrubs prevail over boreal small herbs, while on slopes, the abundance of small herbs and tall herbs increases, but dwarf shrubs still stay dominant. Cover of the bottom layer is 50–100%; boreal green mosses such as Hylocomium splendens and Pleurozium schreberi dominate with a small admixture of Polytrichum commune and Dicranum spp. Additionally, there are lichen – green moss larch forests belonging to the subassociation Cladonio arbusculae–Pinetum boreale pulsatilletosum patentis Saburov 1972 in Morozova et al. 2008 in the middle reaches of the Pinega River (Arkhangelsk region). These forests are distinguished by the presence of species typical for southern Pinus sylvestris forests (Festuca ovina, Pulsatilla patens, Thymus serpyllum, etc.) in the field layer; this may be related to the denudation-­karst landscape which prevails there. A detailed description of these forests is lacking.

3.1.2  Section: Green Moss Forests The diagnostic feature of these forests is the dominance of boreal green mosses in the ground layer. The widest distributed green moss forests in European Russia are classified in the following five associations: ass. Vaccinio vitis-idaeae–Pinetum Caj. 1921, ass. Vaccinio myrtilli–Pinetum Kobendza 1930 Br. Bl. et Vlieger 1993, ass. Empetro–Piceetum obovatae (Sambuk 1932) Morozova comb. nov. 2008, ass. Linnaeo borealis–Piceetum abietis (Caj. 1921) K.-Lund 1962 (the former name is Eu–Piceetum abietis), and ass. Melico nutantis–Piceetum abietis (Caj. 1921) K.-Lund 1981. We distinguish two subsections within the green moss forest section: the green moss – dwarf shrub forests, and the green moss – small boreal herb forests. At some places one can find pure green moss forests with an absolute dominance of green mosses and practical absence of dwarf shrubs, herbs, and ferns in the ground layer. These forests have developed under conditions of strong shading of the ground layer by high-density stands. We consider such forests as part of the green moss – dwarf shrub forest subsection. Subsection of green moss - dwarf shrub forests includes plant communities of the first three associations (V.v.-i.–P., V.m.-P., and E.–P.o.) and of the subass.

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L.b.–P.a. myrtilletosum K.-Lund 1981 of the ass. Linnaeo borealis–Piceetum abietis (Caj. 1921) K.-Lund 1962. Characteristic of this subsection is the boreal dwarf shrub Vaccinium myrtillus dominating in the ground layer together with the boreal green mosses Pleurozium schreberi and Hylocomium splendens. Green moss – dwarf shrub forests are common in the north of European Russia (Gribova et  al. 1980). They are less common in Finland and they are rare in the northern part of Scandinavia (Kilelland-Lund 1981). In European Russia, green moss – dwarf shrub forests occur on substrates and soils of high diversity. They are found on sandy, gravelly, and loamy substrates of different origins and compositions; as a rule, soils have a well-differentiated soil profile (Podzols, Albeluvisols) (Zaboeva 1975; Gerasimova 1987; Morozova 1991). Generally, green moss – dwarf shrub forests grow on more favorable sites in terms of fertility and humidity than lichen forests. On well-drained sites, Haplic Podzols dominate on rough substrates; Carbic, Rustic, and Entic Podzols also occur; podzolic soils (Haplic Albeluvisols) dominate on loams. On poorly drained sites, peaty podzols (Histic Podzols), gley-podzolic soils, podzolic-gley peat (Gleyic Albeluvisols), peat gley soils (Histic Gleysols), and various Histosols are found. Green moss  – dwarf shrub pine forests (Pineta fruticuloso-hylocomiosa) are widespread in the north of European Russia (Tsinzerling 1931; Sambuk 1932; Rutkovsky 1933; Saburov 1972; Rysin 1975; Martynenko 1999a; Neshataev and Neshataeva 2002; Rysin and Savelyeva 2008; Kucherov 2014). Studies of pine forests in which the fire history is known showed that in the absence of fires, green moss – dwarf shrub pine forests replace lichen – green moss pine forests (Gorshkov 1993; Kuleshova et al. 1996; Korotkov et al. 1999). There the succession proceeds from the genuine lichen through the lichen – green moss to the green moss – dwarf shrub pine forests during the lifetime of one generation of Pinus sylvestris (Korotkov et al. 1999) (see Sect. 3.3 for more details). In green moss – dwarf shrub pine forests, besides Pinus sylvestris, Picea spp. often occurs in the overstorey; sometimes it co-dominates with the pine. Viable Pinus sylvestris undergrowth is usually absent; pine renewal is observed only after clear-cuttings and fires. There is much more Picea spp. undergrowth in comparison with the lichen pine forests. Its cover reaches 10–40%. The field layer is well developed and dominated by Vaccinium myrtillus and V. vitis-idaea; Linnaea borealis and Avenella flexuosa always occur. Calluna vulgaris’s share is significantly lower than in the green moss  – lichen pine forests. Lycopodium annotinum and Orthilia secunda occasionally occur. A well-developed moss cover of Pleurozium schreberi, Hylocomium splendens, etc. with a negligible participation of lichens (especially Cladonia rangiferina) is typical for these forests. Soils are the same as in the lichen forests: Haplic Podzols are common; Rustic, Leptic, and Entic Podzols occur. Green moss  – dwarf shrub spruce forests (Piceeta fruticuloso-hylocomiosa) occur within the different landscapes on moraine and fluvioglacial plains, on hills and denudation plateaus, on watersheds, and on slopes of river terraces. All soils typical of this subsection can be found in these forests. Haplic Podzols and Haplic Albeluvisols are common in well-drained areas. Histic and Gleyic Podzols and

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Gleyic Albeluvisols dominate in wet areas; Histic Gleysols are also common. Dwarf-podzols are widely distributed in the mountains. The overstorey is formed by Picea abies, P. obovata, P. x fennica, and Abies sibirica (in the east) with an admixture of birch (Betula pendula or B. pubescens), Populus tremula, and Pinus sylvestris. As a rule, these forests are the successive stage of natural forest development after the green moss  – dwarf shrub pine (or birch) forest stages. In case they originate from post-fire pine forests, the average age of the residual single pines is about 200 years with the maximum age of Pinus sylvestris being near 600 years; fire scars aged more than 100–300 years can be found on such pines (Korotkov et al. 1999; Smirnova and Korotkov 2001; Korotkov 2004). Picea undergrowth is usually present here, but its quality and quantity depend on the structural features of the ecosystem as discussed below. The shrub layer is usually semi-closed; Sorbus aucuparia (S. gorodkovii in the west) and Juniperus communis are quite common. The field layer is dominated by the dwarf shrubs Vaccinium myrtillus and V. vitis-idaea. Evergreen creepers such as Linnaea borealis, species of the genus Pyrola, Orthilia secunda, and Lycopodium annotinum are common. Small boreal herbs such as Maianthemum bifolium, Trientalis europaea, Gymnocarpium dryopteris, etc. are rarer. Boreal green mosses (Pleurozium schreberi, Hylocomium splendens, Ptilium crista-castrensis, etc.) dominate in the bottom layer; bushy lichens are practically absent. In Karelia, green moss – dwarf shrub spruce forests occur at different relief positions: from the top to the bottom of ridges within a denudation-tectonic hilly-ridge landscape. On shallow, eroded soils, Picea abies has a low vitality, and trees usually die and fall with windbreak, without uprooting and soil turbations. In this case Vaccinium myrtillus and green mosses dominating in the ground layer quickly “tighten” the fallen trunks. This greatly complicates Picea abies regeneration, because in boreal forests spruce often emerges from seeds that germinated on the trunks of fallen trees (Obnovlensky 1935; Kazimirov 1971). As a result, Picea abies undergrowth is practically absent in such communities; and structural diversity and species diversity are very low. On richer soils, where Picea abies individuals of normal vitality can grow, trees fall with uprooting as well as by windbreaks. It creates a specific pit-and-mound topography on the forest floor. After treefalls Betula spp. and Populus tremula settle on the bare soil patches and Picea abies undergrowth develops on the large fallen trunks at certain stages in the deadwood decay (Korotkov et al. 1999; Yaroshenko 1999; Smirnova and Korotkov 2001). In the Arkhangelsk region, in the plains of the Komi Republic, and on the low mountains of the western slope of the Northern Urals, green moss – dwarf shrub spruce and spruce-fir forests occur mainly on the relatively well-drained areas on flat tops, in the middle parts of slopes, on terraces, and on terraced slopes. In low and medium-high mountains, such forests occur on steep slopes with heavily eroded soils (Nadutkin and Lazarev 1963; Pakhuchiy 1997; Kozubov and Taskaev 1999). As well as in Karelia, there are forests with a low site quality class score and poor species diversity where pit-and-mound topography is practically absent. At the same time, there are floristically rich forests with a good regeneration of Picea spp. and Abies sibirica (in the east), where elements of the pit-and-mound topography

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are present. Together with zoogenically disturbed patches, this creates conditions for the regeneration of dark coniferous and soft small-leaved trees, various shrubs, and herbaceous species. In the main reviews on the boreal forest vegetation of European Russia (Tolmachev 1954; Lavrenko and Sochava 1956; Gribova et  al. 1980, etc.), green moss – dwarf shrub spruce(-fir) forests are considered as a climax forest ecosystem. However, detailed researches of forest vegetation, soil, and local land use history showed that green moss – dwarf shrub spruce and spruce-fir forests on relatively rich soils and with soil turbation by treefalls with uprooting are forest ecosystems at the middle stage of the autogenic post-fire succession series (see Sects. 3.4 and 3.5 for more details). At the same time, these forests on poor soils, especially in the north of the region, with trees of low vitality, often linger for a long time at this middle stage of succession or degrade to the Vaccinium myrtillus–green moss waste areas (Smirnova and Korotkov 2001; Smirnova and Aleynikov 2012). Green moss  – dwarf shrub birch forests (Betuleta fruticuloso-hylocomiosa) developed after fires or after cutting in spruce or spruce-fir forests of the same subsection. They are found on mountain slopes, in river valleys, and on watersheds. Soils are varied; Haplic and Gleyic Albeluvisols are common (Korchagin 1940; Neshataev and Neshataeva 1993a; Degteva 2001). Forest stands with site class scores of 3 and 4 consist of Betula pubescens with a small admixture of Picea spp. and also of Abies sibirica and Pinus sibirica in the Ural Mountains (Korchagin 1940; Neshataev and Neshataeva 1993a). The average age of B. pubescens varies from 75 to 140  years. In the northern Ural Mountains, there is an admixture of Duschekia fruticosa and Larix sibirica. The shrub layer is well developed and covers 20–70%. It predominantly consists of Sorbus aucuparia. Lonicera pallasii, Rosa acicularis, and Spiraea media occur in the east. Picea spp. and Abies sibirica dominate in the undergrowth. Vaccinium myrtillus and V. vitis-idaea dominate in the field layer. In the northern part of the boreal region, Empetrum nigrum and Vaccinium uliginosum also dominate. Linnaea borealis and Lycopodium annotinum often occur. Mosses cover 40–100% of the bottom layer; Hylocomium splendens dominates and is associated with Pleurozium schreberi and Polytrichum commune. Dicranum scoparium and Ptilium crista-castrensis occur occasionally. Green moss – dwarf shrub Siberian pine forests (Pineta sibiricae fruticuloso-­ hylocomiosa) are described from the Urals’ foothills and in the Urals and from both the north and the south of the boreal region (Korchagin 1940; Nepomilueva 1970, 1974; Pakhuchiy 1997; Martynenko 1999b). Stands score site class values of 4 and 5. In the mountains, the overstorey consists exceptionally of Pinus sibirica; in the foothills, Picea obovata, Abies sibirica, and Betula pubescens co-dominate. Uneven-aged populations of Pinus sibirica can be found (Nepomilueva 1974). The shrub layer consists of Sorbus aucuparia, Rosa acicularis, Juniperus communis, and Lonicera pallasii. Picea obovata and Abies sibirica generally dominate in the undergrowth. Cover of the field layer is 60–70%. Vaccinium myrtillus and V. vitis-­ idaea usually dominate and Empetrum nigrum dominates in the north; Equisetum sylvaticum also prevails under moister conditions. Carex globularis, Avenella flexuosa, and Gymnocarpium dryopteris often occur. Cover of the bottom layer is

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70–100%. Pleurozium schreberi and Hylocomium splendens dominate; Polytrichum commune occurs; Sphagnum angustifolium and S. russowii also occur at the wet patches (Sambuk 1932; Morozova et al. 2008). Subsection of green moss – small boreal herb forests includes plant communities classified as the subassociations L.b–P.a. dryopteridetosum K.-Lund 1981 and L.b–P.a. athyrietosum K.-Lund 1981 of the ass. Linnaeo borealis–Piceetum abietis (Caj. 1921) K.-Lund 1962. Plant communities classified as the ass. Melico nutantis–Piceetum abietis (Caj. 1921) K.-Lund 1981 are also included here. Green moss – small boreal herb forests occur over the entire boreal region and at the same sites as the green moss – dwarf shrub forests. They are widely distributed in the central and southern parts of the region. The distinctive feature of these forests is a permanent presence of small boreal herbs and ferns in the field layer. Maianthemum bifolium, Trientalis europaea, Oxalis acetosella, and Gymnocarpium dryopteris are the most typical species of this group. Gymnocarpium dryopteris usually dominates in the northern part of the region; Oxalis acetosella dominates more often in the south owing to its higher demands on temperature and soil fertility. The other characteristic features of the vegetation in this subsection are the high constancy of Vaccinium myrtillus in the field layer and dominance of Pleurozium schreberi and Hylocomium splendens in the bottom layer. This unites forests of this subsection with the forests of the previous subsection and explains the big diversity of the transitional variants. Nemoral species such as Milium effusum, Melica nutans, Paris quadrifolia, Lathyrus vernus, Stellaria holostea, etc. occur in the forests of this subsection in the south of the region. Soils are mainly the same as soils in the green moss – dwarf shrubs forests. Soils on coarse-textured substrates (Entic Podzols) occur more often in green moss  – small boreal herb forests than in forests of the previous subsection. Acid brown soils (Dystric Cambisols) can be found in the south of the region and in the mountains. These soils rarely may have a mull humus horizon (Humic Umbrisols). In the south, sod-podzolic soils (Albic Luvisols) occur on loamy substrates besides various podzolic soils (Bobrovsky 2010). Green moss – small boreal herb pine forests (Pineta parviherboso-hylocomiosa) are rare in different parts of the boreal region (Kucherov 2013b). For example, in Karelia they are found on flat parts and slopes of lake terraces, on slopes of watershed ridges, and on sandy loam or sandy moraine with a thickness of 1–1.5 m, rarely 0.5–1 m (Romanovsky 2002; Zaugolnova and Morozova 2004). These forests also occur along the coasts of the Onega Peninsula, exclusively within a 1–1.5 km wide strip on podzolic soils located over calcareous loams (Sokolova 1935). Tree stand density varies widely from 0.1 to 0.6, and stands have low site class scores (5 and 5a). Pinus sylvestris dominates in the overstorey with an admixture of Picea spp., Betula pendula, B. pubescens, and Alnus incana. The density of the understorey varies. Daphne mezereum, Frangula alnus, Juniperus communis, Lonicera xylosteum, Rosa acicularis, R. majalis, Rubus idaeus, Sorbus aucuparia, and Padus avium can be found there. Picea abies undergrowth with an admixture of Betula spp., Populus tremula, and Alnus incana always occurs. Pinus sylvestris undergrowth is very rare and poorly developed. The field layer is well developed

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and its cover varies from 50 to 95%. The dwarf shrubs Vaccinium myrtillus and V. vitis-idaea dominate together with small boreal herbs, ferns, and grasses such as Avenella flexuosa, Oxalis acetosella, Maianthemum bifolium, and Gymnocarpium dryopteris. In the west of the middle taiga, one can find pine forests with a dominance of Pteridium aquilinum, which indicates a post-fire origin of these communities. In Karelia, in the south of the boreal region, Calamagrostis arundinacea, Dryopteris carthusiana, Fragaria vesca, Geranium sylvaticum, Trientalis europaea, and Rubus saxatilis often occur with nemoral species such as Convallaria majalis, Lathyrus vernus, Melica nutans, etc., Pinus sylvestris forests with Larix sibirica and Picea abies and with a similar relatively rich understorey also occur in the northern taiga, on limestones in the Onega Peninsula (Sokolova 1935). Pleurozium schreberi, Hylocomium splendens, and Dicranum scoparium dominate in the bottom layer which covers 40–70% varying inversely with the cover of the field layer. Green moss – small boreal herb spruce (and spruce-fir) forests (Piceeta (PiceetoAbieta) parviherboso-hylocomiosa). In the west, these forests occur on welldrained slopes within the denudation ridge landscape and on lake terraces on sandy and sandy-­loam substrates (Kucherov et  al. 2010). In the east, these forests also occur on well-­drained sites: they can be found on slopes of moraine hillocks, on flat areas of watersheds, on the gentle slopes of foothills, and on noncalcareous as well as carbonate-­rich moraine loams (Korchagin 1940; Kolesnikov 1985; Romanovsky 2002; Smirnova et al. 2006). The overstorey is usually closed; stand site class varies from 2 to 4. Stands are formed by Picea spp. and Abies sibirica (in the east), rarely with an admixture of Betula spp. and Populus tremula. Picea spp. dominate in the undergrowth together with Abies sibirica in the east; Betula pubescens can also occur in the undergrowth. Similar to the spruce(-fir) forests of the previous subsection, spruce(-fir) forests of this subsection can be differentiated in two extreme variants: forests with and without a well-developed structural diversity of the ecosystem. In the first case, large trees fall with uprooting and create a gap mosaic in the canopy together with a pit-and-mound topography on the ground. Here one can observe a higher structural diversity in the green moss – small boreal herb spruce forests in comparison with the green moss – dwarf shrub spruce forests (Smirnova et al. 2006). It leads to a better stand site class and an increase of species richness and diversity of the ecological-coenotic structure of the understorey. In such forests, species of the genera Sorbus, Rosa, Ribes, Lonicera, etc. are present in the shrub layer; many boreal species such as Gymnocarpium dryopteris, Maianthemum bifolium, Trientalis europaea, Rubus arcticus, Oxalis acetosella, etc. grow in the field layer; Dryopteris dilatata and some other tall boreal herbs and ferns also occur. The cover of mosses decreases in comparison with the dwarf shrub – green moss forests and makes up 40–60% of the ground layer (Smirnova et al. 2006). In the forests where trees often fall without uprooting, pedoturbations are almost absent or extremely rare, and the structure and composition of the green moss – small boreal herb spruce forests differ little from that in the green moss – dwarf shrub forests. The shrub layer is poorly developed and made up by species of the genera Sorbus and Rosa and by Juniperus

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communis. In the ground layer, several boreal small herbs co-dominate with Vaccinium myrtillus; the cover of mosses is higher than in the previous variant. Differentiation in the structural and compositional diversity of the boreal green moss forests results from the diversity of substrates, relief positions, and intensity and size of historical and current human impacts that affect seed flow and speed of ecosystem recovery after impacts from outside. Green moss – small boreal herb birch (and aspen) forests (Betuleta (Populeta) parviherboso-hylocomiosa) develop after logging and burning of the green moss – small herb spruce(-fir) forests located on well-drained sites on watersheds, slopes of moraine hillocks, and river terraces (Degteva 2001). The cover of the overstorey is relatively high: 70–80%. Betula pubescens (and/or Populus tremula), Picea spp., and Abies sibirica (in the east) dominate in the overstorey; and Pinus sylvestris also occurs. There is an undergrowth of Picea spp., Abies sibirica, and Betula pubescens. In the shrub layer, Sorbus aucuparia and Juniperus communis more often occur; Rosa acicularis, Lonicera pallasi, etc. can be also found. The field layer is composed of diverse small boreal herbs and ferns such as Trientalis europaea, Gymnocarpium dryopteris, Oxalis acetosella, Maianthemum bifolium, etc.; occasional individuals of tall boreal herbs of, e.g., Geranium sylvaticum, Crepis paludosa, Cirsium heterophyllum, Aconitum septentrionale, and the large fern Dryopteris dilatata are frequent. The dwarf shrubs Vaccinium myrtillus and V. vitis-idaea are always present but in low abundance. Sometimes Avenella flexuosa dominates. Pleurozium schreberi and Hylocomium splendens dominate the bottom layer.

3.1.3  Section: Large Fern Forests The diagnostic feature of forests in this section is the absolute dominance of the large fern Dryopteris dilatata in the ground layer. This causes a relatively low species diversity and a low cover of flowering plants in the field layer and of mosses and lichens in the bottom layer. Due to the rarity of these communities, they have not yet been described by the Braun-Blanquet approach and neither in the Coenofund (Zaugolnova and Martynenko 2014). However, their unique composition and structure demand to distinguish these forests in a separate section. We do not currently distinguish subsections here and describe only spruce-fir forests as the most widely distributed large fern forests. Large fern spruce-fir forests (Piceeta (P.-Abieta) magnofilicosum) are described from the low mountains of the Urals, where they occupy large areas on well-drained upper slopes with eroded soils, and in the plains of the Komi Republic, where they rarely occur as separate, small patches (Korchagin 1940; Dyrenkov et  al. 1972; Dyrenkov 1984; Martynenko 1999b; Smirnova et  al. 2006, 2011). Al-Fe-humic podzols (Haplic Podzols) with a shallow soil profile prevail; shallow podburs (Entic Podzols) and acid brown soils (Dystric Cambisols) also occur (Smirnova et al. 2006, 2011; Bobrovsky 2010).

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Picea obovata and Abies sibirica dominate in the overstorey where large single trees of Pinus sibirica and Betula pubescens also can occur. Stem density varies from 0.4 to 0.6. The cover of the shrub layer is low (5–10%); it consists of Rosa acicularis, Sorbus aucuparia, Juniperus communis, etc. The field layer covers 80–100% and in it Dryopteris dilatata absolutely dominates. Boreal small herbs, ferns, and dwarf shrubs such as Gymnocarpium dryopteris, Maianthemum bifolium, Oxalis acetosella, Linnaea borealis, and Vaccinium myrtillus occur in low abundance under the large ferns. Under the shading canopy of Dryopteris dilatata, the cover of the boreal green mosses is low and varies from 5 to 40%. We assume that forests of this type develop as a result of repeated fires over large areas, followed by erosion of the soil. Spore plants, including ferns, horsetails, and clubmosses, firstly occupy such areas, and then large ferns hamper the invasion of flowering plants through light, water, and nutrient competition. Further study of these forests is necessary in order to explain their history and to forecast the succession dynamics of these forests (see Sects. 3.4 and 3.5 for more details).

3.1.4  Section: Boreal Tall Herb Forests The diagnostic feature of these forests is the dominance of mesophilous boreal tall herbs in the ground layer. These forests are classified as the association Aconito septentrionalis–Piceetum obovatae Zaugolnova et Morozova 2009, subassociation typicum (Zaugolnova et al. 2009). This section includes the unique plant communities which occur on watersheds from Karelia to the Ural Mountains and which significantly differ in composition and structure from the rare large fern forests and from the widely distributed lichen, green moss, and sphagnum forests (Zaugolnova et al. 2009). Soils are very diverse in the boreal tall herb forests (Smirnova et al. 2006, 2011). Dystric Cambisols occur more often than some other soil types. Haplic and Entic Podzols and Humic Umbrisols occur at well-drained sites. Haplic and Albic Luvisols can be found in the south of the region. Histosols occur on wet sites (Smirnova et al. 2006, 2011; Bobrovsky 2010). Boreal tall herb spruce(-fir) forests (Piceeta (P.-Abieta) magnoherbosa) are found in Karelia and the Komi Republic, in the Arkhangelsk region, in the north of the Vologda region, and in the Ural Mountains (Korchagin 1940; Saburov 1972; Laschenkova and Nepomilueva 1982; Kolesnikov 1985; Nepomilueva and Laschenkova 1993; Martynenko 1999b; Smirnova and Korotkov 2001; Smirnova et al. 2006, 2011; Zaugolnova et al. 2009). Tall herb spruce forests are found in the northern taiga in Karelia on the middle and lower parts of slopes, in places with a relatively low probability of spreading fires. Areas with such sites are usually small, ranging from tenths of a hectare to 1 hectare; they form separate patches within green moss – dwarf shrub spruce forests. More extensive areas of tens of hectares also occur. In the middle taiga, tall herb dark coniferous forests are found on watersheds in the Arkhangelsk region, in the north of the Vologda region, and in plains of the Komi Republic. Tall herb spruce-fir

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forests with Pinus sibirica are found in the middle and lower parts of the Ural Mountains, where they occur on watersheds and more often on the middle and upper parts of slopes. The extension of these forests is usually from one to tens of hectares. In general, the occurrence and areas of the tall herb dark coniferous forests in upland-slope positions significantly increase from the west to the east of the European part of Russia; they reach maximum values in the low and middle mountains of the Middle and Northern Urals. Tree density of the overstorey highly varies from 0.2 to 0.6; stand quality is medium (site classes 2–4). Dark coniferous trees dominate in the overstorey: Picea abies in the west and Picea obovata, Abies sibirica, and often Pinus sibirica in the east. Usually there is a small admixture of Betula pubescens, B. pendula, Populus tremula, and Alnus incana. There is always an undergrowth of Picea spp. and Abies sibirica (in the east). In the Karelian tall herb spruce forests, the density of the shrub layer greatly varies from 0.2 to 0.8. Ribes glabellum, Salix phylicifolia, Sorbus aucuparia, Alnus incana, and Padus avium occur in the understorey. In the tall herb spruce-fir forests in the east, the density of the shrub layer is lower but the composition is richer: Rosa acicularis, various species of Lonicera (L. altaica, L. pallasii, and L. xylosteum) and Ribes (R. hispidulum, R. nigrum, and R. spicatum), Spiraea media, and Daphne mezereum grow there. Cover of the field layer is 70–100%. Of the large herbs and ferns in the Karelian spruce forests, Cicerbita alpina, Actaea erythrocarpa, Cirsium heterophyllum, Geranium sylvaticum, Diplazium sibiricum, and Dryopteris carthusiana may dominate. In the dark coniferous forests located on the plains, Aconitum septentrionale, Cirsium oleraceum, C. heterophyllum, Angelica sylvestris, Diplazium sibiricum, and Chamaenerion angustifolium dominate. In the spruce-fir forests with Pinus sibirica in the Northern and Middle Urals, Aconitum septentrionale, Cacalia hastata, Crepis sibirica, Delphinium elatum, Paeonia anomala, Pleurospermum uralense, Thalictrum minus, Diplazium sibiricum, and Dryopteris dilatata prevail. An important feature of the tall herb dark coniferous forests is their strong structural diversity caused by the existence of deadwood at different stages of decomposition, well-developed pit-and-mound topography, and gap mosaics in the tree canopy. As a result, plant species with different ecological and phytocoenotic properties grow at different patches within one plant community and that lead to the high species richness of this forest type (Smirnova and Korotkov 2001; Smirnova et al. 2006, 2011). Dwarf shrubs such as Vaccinium vitis-idaea and V. myrtillus, boreal mosses, and sometimes bushy lichens grow on the deadwood and at the base of large standing trees; nitrophilous species such as Chrysosplenium alternifolium and Stellaria nemorum and meadow species such as Vicia cracca, Ranunculus polyanthemos, and Lathyrus pratensis grow, respectively, in the pits and on the mounds formed by treefalls. In patches between tree crown projections, tall herbs dominate in the first sublayer of the field layer; nemoral species such as Lathyrus vernus and Milium effusum grow in the second sublayer; and boreal small herbs and ferns such as Oxalis acetosella, Trientalis europaea, and Gymnocarpium dryopteris grow under them. In the bottom layer, hemiboreal mosses dominate: species of the genera Brachythecium, Plagiothecium, Plagiomnium, and also Rhodobryum roseum.

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As a whole, the high diversity of mosses is remarkable in all tall herb dark coniferous forests at watersheds, whereas the cover of the mosses is not so large. For example, in the Karelian forests and in the spruce-fir forests in the Pechora-Ilych and Vishera Nature Reserves in the Ural Mountains, it varies from 5 to 25% (Smirnova et  al. 2006, 2011). Dicranum scoparium, Hylocomium splendens, Pleurozium schreberi, Polytrichum commune, Rhytidiadelphus triquetrus, etc. are common in the bottom layer. In the Karelian forests, Marchantia polymorpha, Ptilium crista-castrensis, and Rhytidiadelphus triquetrus can be also found. In the spruce-fir forests in the Komi Republic and the Perm region, Barbilophozia lycopodioides, Brachythecium reflexum, Rhizomnium magnifolium, Rhodobryum roseum, and Sanionia uncinata often occur. Besides dark coniferous forests, birch, aspen, and larch forests dominated by mesophilic boreal tall herbs in the ground layer also have been described. As a rule, they have developed after logging and rare fires in the tall herb dark coniferous forests. The shrub layer is well developed, and the regeneration of dark coniferous trees is more successful in these forests than in the spruce(-fir) forests. In these forests the field layer contains more nemoral species and less boreal species (Zaugolnova et al. 2009). Boreal tall herb birch forests (Betuleta magnoherbosa) occur on different substrates and different soils (Degteva 1999, 2001). Tree stands usually are closed and well developed. There are often two sublayers in the overstorey: the upper sublayer is dominated by Betula pubescens with a small admixture of Populus tremula and B. pendula, and the lower sublayer is dominated by Picea abies or P. obovata with Abies sibirica and Pinus sibirica in the east. The shrub layer consists of Sorbus aucuparia, Rosa acicularis, Juniperus communis, and Lonicera xylosteum (in the west) or L. pallasii (in the east). The undergrowth consists of Betula spp. and Picea spp., with admixture of Abies sibirica in the east. Cover of the field layer varies from 40 to 90%. Tall boreal herbs such as Geranium sylvaticum, Cirsium heterophyllum, Chamaenerion angustifolium, etc. and sometimes the large ferns Dryopteris dilatata and D. carthusiana play a significant role in the field layer. Gymnocarpium dryopteris, Oxalis acetosella, and rarely Vaccinium myrtillus co-­ dominate there. Trientalis europaea, Maianthemum bifolium, Luzula pilosa, and Linnaea borealis often occur. Nemoral species such as Aegopodium podagraria, Stellaria holostea, Lathyrus vernus, Melica nutans, Asarum europaeum, and Pulmonaria obscura also occur with low abundance. A moss cover is poorly developed: usually covering 5 to 10%, rarely up to 30%; constant species are Hylocomium splendens, Rhytidiadelphus triquetrus, and Pleurozium schreberi. Hemiboreal mosses such as Brachythecium spp., Plagiothecium laetum, Plagiomnium medium, P. cuspidatum, and Rhodobryum roseum occur. Boreal tall herb larch forests (Lariceta magnoherbosa) are described from the eastern part of the boreal region (Dylis 1940; Kolesnikov 1985). Larix sibirica dominates in the first and second sublayers of the overstorey with an admixture of Picea obovata, Betula pendula, Abies sibirica, and sporadic trees of Pinus sylvestris. Larix sibirica reaches large sizes here: up to 40 m in height and 120–140 cm in diameter. Cover of the shrub layer is 20–30% with Rosa acicularis, Sorbus aucu-

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paria, Juniperus communis, and Lonicera xylosteum as dominants; Daphne mezereum and Spiraea media occur with lower abundance. The undergrowth consists of Picea obovata with Abies sibirica; Larix sibirica rarely occurs. Cover of the field layer is 80–100%. Aconitum septentrionale, Cirsium heterophyllum, Geranium sylvaticum, Thalictrum minus, Crepis sibirica, and Chamaenerion angustifolium dominate in the first sublayer with a height of 1–1.5 m and a cover of up to 40%. There are also Paeonia anomala and Saussurea sibirica in the northeastern part (Dylis 1940; Martynenko 1999a). The second sublayer includes boreal small herbs and ferns such as Equisetum pratense, Rubus saxatilis, Oxalis acetosella, Gymnocarpium dryopteris, Maianthemum bifolium, Trientalis europaea, etc. and a small share of the dwarf shrubs Vaccinium vitis-idaea and V. myrtillus. Nemoral species such as Melica nutans, Brachypodium pinnatum, Lathyrus vernus, Stellaria holostea, and Viola mirabilis occur. Atragene sibirica is a typical liana. Cover of the mosses is 10–20%. Hylocomium splendens, Pleurozium schreberi, Dicranum polysetum, and Climacium dendroides are common. The lichens Cladonia cornuta, C. deformis, and C. gracilis occur in the tall herb larch forests in the middle taiga (Kolesnikov 1985).

3.1.5  Section: Boreal Swamp Forests Forests referred to in this section are characterized by continuous or periodic waterlogging and running water to varying degrees. These forests prevail in the valleys of rivers and streams (riparian forests), and they also occur at river terraces and on slopes of watersheds in places with relatively good drainage but where groundwater discharges. In contrast to the watershed forests without excessive moisture, where treefalls with uprooting mainly create mosaics of microsites with different ecological conditions, in boreal swamp forests not only treefalls but also relief positions, type of substrate and characteristics of water movement strongly affect the structure and composition of the communities. Meso-hygrophilous and hygrophilous plants dominate in the ground layer. We distinguish two subsections within the boreal swamp forests: nitrophilous tall herb forests and genuine swamp tall herb forests. Subsection of nitrophilous tall herb forests. The diagnostic feature of this subsection is the dominance of nitrophilous tall herbs in the ground layer, most frequently by Filipendula ulmaria. Plant communities of this subsection belong to the association Aconito septentrionalis–Piceetum obovatae Zaugolnova et Morozova 2009, subassociation filipenduletosum Zaugolnova et al. 2009. Dystric Fluvisols with a moder humus horizon up to 50  cm prevail; Gleyic Fluvisols also occur; Eutric Fluvisols occur in the south of the boreal region. Fluvisols occur in the near vicinity of Fibric Histosols. Shallow Haplic Fluvisols are common in floodplains of streams in middle-high and low mountains. Nitrophilous tall herb spruce and spruce-fir forests (Piceeta (P.-Abieta) nitrophilo-­ magnoherbosa) are usually found in the valleys of rivers and streams, and they also

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occur on terraces and slopes at sites where groundwater discharges. In Karelia, this type is relatively rare, because most of the floodplains have high stony banks with steep slopes as a result of the widespread occurrence of rocky substrates and eroded soils that result from frequent fires. In the Arkhangelsk and Vologda regions and in the plain parts of the Komi Republic, this type is more common, and it is entirely common on the western slopes of the Ural Mountains (Smirnova and Korotkov 2001; Smirnova et al. 2006; Zaugolnova et al. 2009; Kucherov et al. 2010). The composition and structure of the tree layer in the nitrophilous dark coniferous forests are similar to that of the boreal tall herb spruce(-fir) forests, but Alnus incana is frequently present in the overstorey and understorey and Alnus glutinosa also appears in the south of the boreal region. Crown cover highly varies; and stand quality scores site class values of 3 or 4. In the spruce-fir forests in the east, the cover of the shrub layer is 10–30%, but it is rich in species: in addition to the species growing in the understorey of the boreal tall herb spruce-fir forests, Padus avium and Salix fragilis also occur. In Karelian nitrophilous tall herb spruce forests, the shrub layer is poorer; Sorbus gorodkovii, Juniperus communis, and Padus avium dominate there. Typically the nitrophilous tall herb spruce and spruce-fir forests show the highest cover values (80–100%) and species diversity (up to 50 vascular plant species per 100 m2) in the ground layer. Nitrophilous and boreal tall herbs and ferns prevail; nemoral and meadow plants also often occur. In the Karelian forests, the proportion of nemoral species is much smaller and that of oligotrophic plants is higher than in the more eastern forests. The Karelian forests also have more ferns, such as Gymnocarpium dryopteris, Phegopteris connectilis, Diplazium sibiricum, Dryopteris assimilis, and Matteuccia struthiopteris, whereas in the eastern forests, tall herbs such as Filipendula ulmaria, Cirsium oleraceum, Trollius europaeus, Crepis paludosa, Ligularia sibirica, Veratrum lobelianum, Urtica sondenii, Aconitum septentrionale, and Angelica archangelica often occur. The diversity of mosses is also higher in the nitrophilous tall herb forests than in the boreal tall herb forests. No species dominates. Besides the common boreal green mosses, such as Pleurozium schreberi and Hylocomium splendens, one can find Brachythecium spp., Dicranum spp., Hylocomiastrum spp., Plagiothecium spp., Plagiomnium spp., Barbilophozia lycopodioides, Calliergon cordifolium, Bryum weigelii, Sanionia uncinata, etc. Many studies showed that of all boreal forests the nitrophilous tall herb forests have the highest species diversity (Kuchko 1992; Yelina et al. 1994; Gromtsev 2002; Vasilevich 2002; Smirnova et al. 2006; Zaugolnova et al. 2009); these are mainly riparian tall herb forests. This may be explained by the lower incidence of fires at well-moistened sites that would protect many species. Additionally, the dynamic character of even small streams creates a greater variety of microsites than the corresponding conditions at well-drained sites. Moreover, in the absence of fire, uneven-aged dark coniferous forests develop with a gap mosaic in their canopy and pit-and-mound topography in the ground layer. All of this enhances the possibility of coexistence of species with different ecological properties within one and the same plant community.

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Besides the nitrophilous tall herb dark coniferous forests, tall herb aspen, birch, or grey alder forests have been described from river valleys in the boreal forest region. They develop after cutting and fires in the riparian forests. Nitrophilous tall herb aspen forests (Populeta nitrophilo-magnoherbosa) occur over the entire boreal region, more often in the east and especially in the south of the region. They occupy bottoms of slopes under conditions of running moisture. Tree stands consist of Populus tremula with a small admixture of Betula pubescens, Picea spp., and Abies sibirica in the east. Picea spp. dominates in the second sublayer of the overstorey. The density of the shrub layer is 0.3–0.8; it consists of Lonicera pallasii and Sorbus aucuparia. Cover of the field layer is 80–100%; it consists of several sublayers with a maximum height of 1–1.5 m. Aconitum septentrionale, Calamagrostis canescens, Filipendula ulmaria, Geranium sylvaticum, and Equisetum sylvaticum co-dominate. Tall herb species such as Chamaenerion angustifolium and Thalictrum minus are always present. Boreal small herbs and ferns such as Oxalis acetosella, Gymnocarpium dryopteris, and Maianthemum bifolium and nemoral species such as Lathyrus vernus, Stellaria holostea, Pulmonaria obscura, and Melica nutans often occur. The moss cover is not well developed: its cover is 5–7%; but its species diversity is quite high – Brachythecium salebrosum, Hylocomium splendens, Pleurozium schreberi, Plagiomnium cuspidatum, Dicranum scoparium, and others occur (Degteva et al. 2001). Nitrophilous tall herb birch forests (Betuleta nitrophilo-magnoherbosa) are described from the entire boreal forest region (Sambuk 1932; Korchagin 1940; Degteva 2001; Degteva et al. 2001; Zaugolnova et al. 2009). They are found on river floodplains, in ravines and gullies, and in other sites with running water. Tree stands consist of Betula pubescens with a small admixture of Picea spp. and Abies sibirica in the east, rarely Populus tremula and Pinus sibirica. Cover of the overstorey varies from 50 to 100%. Average tree age can be up to 100 years old (Korchagin 1940). Cover of the shrub layer is 20–50%. It often consists of Sorbus aucuparia and Padus avium; Lonicera pallasii, Ribes hispidulum, Ribes nigrum, Spiraea media, and Salix caprea also occur. In the undergrowth, Picea spp., Abies sibirica and rarely Pinus sibirica in the east, and Betula pubescens can be found. Cover of the field layer is 90–100%. It has several sublayers with the maximum height of 1–2 m. Filipendula ulmaria, Geranium sylvaticum, and Equisetum sylvaticum co-dominate with Aconitum septentrionale and Calamagrostis langsdorfii (Sambuk 1930; Korchagin 1940) or C. purpurea (Degteva 1999). Tall herbs such as Cirsium heterophyllum, Thalictrum minus, Veratrum lobelianum, etc. always occur. Species with a Siberian distribution area, such as Paeonia anomala, Stellaria bungeana, Cacalia hastata, Crepis sibirica, Pleurospermum uralense, and the liana Atragene sibirica, occur in the eastern part of the region. The moss cover is weakly developed but quite rich in species: it includes Hylocomium splendens, Pleurozium schreberi, Plagiomnium affine, Barbilophozia lycopodioides, etc. Nitrophilous tall herb grey alder forests (Alneta incanae nitrophilo-­ magnoherbosa) occur widespread over the entire boreal region (Degteva et  al. 2001; Zaugolnova et al. 2009). Their crown cover is quite high: 60–90%, and the height of the tree layer is 10–14 m. Alnus incana prevails; Betula pubescens, Salix

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caprea, and occasionally Picea spp. occur as an admixture. Alnus glutinosa occurs in the south, close to the hemiboreal region. Cover of the shrub layer is 60–80%. There is an undergrowth of Picea spp. and Betula pubescens. The shrubs Lonicera pallasii and Ribes nigrum and Rubus idaeus as well are common in the south of the region; Rosa acicularis is common in the north. The field layer is tall: 1.5–2.5 m; its cover is 75–95%. Filipendula ulmaria dominates. Aconitum septentrionale, Calamagrostis purpurea, and Urtica sondenii co-dominate. Saussurea alpina, Elymus caninus, Lactuca sibirica, and Crepis sibirica often occur in the north. The moss cover is poorly developed: cover usually is not more than 10% but rarely increases up to 20–40%. Climacium dendroides, Calliergon cordifolium, species of the genera Brachythecium, and Plagiomnium often occur; boreal mosses can also be found in the northern taiga (Degteva et al. 2001). Subsection of genuine swamp tall herb forests. There are two diagnostic features of forests referred to this subsection. The first one is the dominance of species of the water-marsh ecological-coenotic group in the ground layer (see Sect. 2.2). There are large hygrophilous sedges such as Carex vesicaria, C. elongata, C. acuta, etc.; grasses such as Phalaroides arundinacea, Phragmites australis, etc.; and herbs such as Veronica longifolia, Naumburgia thyrsiflora, Menyanthes trifoliata, and species of the genus Thalictrum as well. The second feature is the high frequency of nitrophilous tall herbs such as Filipendula ulmaria, Lysimachia vulgaris, and Scirpus sylvaticus. Plant communities of this subsection are classified into the association Pseudobryo cinclidioidis–Piceetum abietis Kutenkov ex Zaugolnova nov. prov. and association Galio physocarpi–Betuletum Degteva ex Zaugolnova nov. prov. Peaty bog soils, such as Fibric Histosols (dystric), Histic Gleysols, and rarer Haplic Gleysols (dystric), prevail in these forests. Umbric Fluvisols occur in floodplains; they are common in alder forests. Genuine swamp tall herb spruce forests (Piceeta uliginoso-magnoherbosa) occur in small fragments over the entire boreal forest region, but they were described only from the southwest: in Karelia and in the Arkhangelsk region (Kutenkov 2005). They are located in thalwegs of streams and flat depressions in poorly drained lowlands; the substrate sometimes is calcareous loam (Pyavchenko 1957). There is a combination of running water and stagnant moisture; the level of the groundwater varies between 0.0 and 0.5 m. Typically there is a microrelief of alternating depressions and elevations. Preliminary analysis of these communities refers them to the association Pseudobryo cinclidioidis–Piceetum abietis Kutenkov ex Zaugolnova nov. prov. (Zaugolnova and Martynenko 2014). Picea abies of 80–140  years old dominates in the stands and tree height is 20–22  m; crown cover is 30–60%; site classes are 3 and 4. Betula pubescens, Populus tremula, Salix spp., Alnus incana, and A. glutinosa occur in the overstorey as an admixture. Cover of the shrub layer is 10–15%. It contains Sorbus aucuparia, Frangula alnus, Ribes nigrum, Rosa acicularis, Salix myrsinifolia, and occasionally Juniperus communis. Picea abies dominates in the undergrowth with an admixture of Betula pubescens and Alnus incana. Cover of the field layer is 45–50%; Calamagrostis canescens, C. purpurea, Filipendula ulmaria, and Geum rivale dominate. Typical of these forests is that water-marsh species (Viola epipsila, Galium

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palustre, Caltha palustris, Carex disperma), boreal herbs (Trientalis europaea, Maianthemum bifolium, Oxalis acetosella, Equisetum sylvaticum), boreal and piny dwarf shrubs (Vaccinium myrtillus, V. vitis-idaea), and oligotrophic species (Carex globularis) all co-occur. Moss cover is 40–60% with dominance of Sphagnum warnstorfii and S. centrale; green mosses (Pleurozium schreberi, Hylocomium splendens, Dicranum scoparium, Rhytidiadelphus triquetrus, and Climacium dendroides) are present with high constancy and little coverage (Kutenkov 2005). Genuine swamp tall herb birch forests (Betuleta uliginoso-magnoherbosa) are divided into a western and an eastern forests; they are preliminarily classified into the association Pseudobryo cinclidioidis–Piceetum abietis Kutenkov ex Zaugolnova nov. prov. and the association Galio physocarpi–Betuletum Degteva ex Zaugolnova nov. prov., respectively (Zaugolnova and Martynenko 2014). Swamp tall herb birch forests in the western part of the boreal region are described from depressions and the rims of marshes (Romanovsky 2002; Kutenkov 2005). Crown cover of these sparse stands is 40%; tree height measures 16–18 m; site class is 5. Betula pubescens dominates with a small admixture of Picea abies, Pinus sylvestris, and Alnus spp. Cover of the shrub layer is small (about 10%); it includes Sorbus aucuparia, Frangula alnus, Salix myrsinifolia, Juniperus communis, etc. There is an undergrowth of Betula pubescens, Alnus spp., Pinus sylvestris, and Padus avium. The field layer covers 60% or more. Calamagrostis spp., Filipendula ulmaria, and Menyanthes trifoliata dominate; Equisetum fluviatile, Carex elongata, and C. cespitosa often occur. The moss cover is poorly developed and averages 15%. The most common species are Sphagnum warnstorfii, Pseudobryum cinclidioides, Calliergon cordifolium, Aulacomnium palustre, Dicranum scoparium, and Hylocomium splendens. Swamp tall herb birch forests described from the eastern part of the boreal region are located in floodplains and in swampy depressions near terraces (Laschenkova 1954; Degteva 1999, 2001). Crown cover is relatively high (60–80%); height of trees is 16–22 m. Betula pubescens and B. pendula dominate; Populus tremula and Picea obovata occur. The undergrowth includes Betula pubescens with an admixture of Picea obovata, Abies sibirica, Alnus incana, Salix caprea, and Sorbus aucuparia. The understorey covers 20–30% (rarely up to 60%); its height is 1–3 m. It contains Padus avium, Frangula alnus, Lonicera pallasii, Rosa acicularis, R. majalis, and Ribes nigrum. The field layer covers 60–90% and is 0.7–1.3  m high. It consists of two or three sublayers. Carex cespitosa, Filipendula ulmaria, Calamagrostis canescens, and C. purpurea dominate in the upper sublayer. Rubus saxatilis dominates at less flooded areas in the floodplain. The moss cover is poorly developed or completely absent; Climacium dendroides and Rhytidiadelphus triquetrus can occur. Genuine swamp tall herb grey alder forests (Alneta incanae uliginoso-­ magnoherbosa) are preliminarily classified into the association Pseudobryo cinclidioidis-­Piceetum abietis Kutenkov ex Zaugolnova nov. prov. (Zaugolnova and Martynenko 2014). They are currently described only from Karelia: in floodplains of small rivers, in thalwegs of streams, and in swampy near-terrace depressions (Kutenkov 2005). A hummocky microrelief is usually well developed in these

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communities. Crown cover varies from 30 to 90%; tree height is 16–22 m; site class is 3–4. Tree stands are dominated by Alnus incana with an admixture of Betula pubescens and Picea abies. The undergrowth consists of the same species. A. glutinosa appears in the south of the region. Cover of the understorey is 10–30%; it contains Padus avium, Sorbus aucuparia, Frangula alnus, Rosa acicularis, and Salix myrsinifolia. The field layer covers 50–60% and is made up of Filipendula ulmaria, Phalaroides arundinacea, Phragmites australis, and Carex vesicaria as dominants but also contains Calamagrostis spp., Calla palustris, Naumburgia thyrsiflora, Menyanthes trifoliata, etc. Just as in the genuine swamp tall herb spruce forests, species of different ecological-coenotic groups co-occur: boreal small herbs and dwarf shrubs and nemoral and oligotrophic plants. Cover of the moss layer is low (15–25%), but species composition is diverse: Pseudobryum cinclidioides, Calliergon cordifolium, Climacium dendroides, Dicranum scoparium, and Pleurozium schreberi always occur; Sphagnum squarrosum, S. warnstorfii, etc. can also be found.

3.1.6  Section: Sphagnum Forests The diagnostic feature of these forests is the dominance of sphagnum mosses in the ground layer. Forests of this section developed in depressions on watersheds, on gentle slopes at poorly drained sites, and at the lower parts of slopes with high groundwater tables. They are characterized by an excess of stagnant moisture and soil gleying. Plant communities discussed in this section are very different in their structure and species composition. The differences result from a complex combination of microsites formed as a result of treefalls, differences in relief positions, and features of waterlogging on various substrates. Sphagnum forests are currently widespread in the boreal forest region. To a great extent, this is a consequence of the wide distribution of crown fires and massive clear-cuttings over large areas. Large-scale deforestation changes the hydrological regime and leads to waterlogging of forest lands and to the development of forest bogs. We distinguish three subsections within the sphagnum forests: polytrichum-­ sphagnum forests, dwarf shrub – sphagnum forests, and herb-sphagnum forests. Subsection of polytrichum-sphagnum forests includes plant communities of the association Rubo chamaemori–Piceetum abietis K.-Lund 1962. Forests of this subsection are characterized by the co-dominance of sphagnum mosses and Polytrichum commune in the ground layer. We distinguish the following variants: (i) a variant where several Sphagnum species can dominate and in addition S. girgensohnii is a constant species, (ii) a variant where Polytrichum commune dominates and sphagnum mosses occur as an admixture, and (iii) a variant in which the bottom layer contains a whole set of species, but Sphagnum girgensohnii, S. angustifolium and others dominate, and Polytrichum commune and other green mosses also occur. In the northern taiga, lichens can also occur in the bottom layer. Boreal

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meso-hygrophilous herbs such as Equisetum sylvaticum and boreal dwarf shrubs such as Vaccinium myrtillus, piny dwarf shrubs (V. vitis-idaea), oligotrophic herbs and sedges (Rubus chamaemorus and Carex globularis), and oligotrophic dwarf shrubs (Vaccinium uliginosum) dominate and/or have a high frequency in the field layer of these forests. Soils are influenced by shallow groundwater and often have peaty topsoils. Histic and Gleyic Podzols dominate on coarse-textured substrates and Histosols dominate in depressions. Histic and Gleyic Albeluvisols together with Histic and Haplic (dystric) Gleysols often occur on the fine-textured substrates. We consider polytrichum-sphagnum forests as plant communities at the initial stage of forest waterlogging which usually happens after clear-cuttings and fires. Korchagin (1940) also wrote that the prevalence of Polytrichum commune can be associated with fire: after the death of the trees as a result of fires, evaporation is sharply reduced; Polytrichum commune begins to grow, and when it develops a continuous cover, this leads to a further deterioration of the hydrological regime. Polytrichum-sphagnum spruce and spruce-fir forests (Piceeta (P.-Abieta) polytrichoso-­sphagnosa) occur widespread over the entire boreal region. They grow in flat depressions between ridges in floodplains, at the sources of small rivers, on the lower parts of gentle slopes, and in the mesorelief depressions on watersheds. Their groundwater level varies from 0.2 to 0.8 m. Picea spp. forms the overstorey; Betula pubescens and Pinus sylvestris occur as an admixture. Abies sibirica and Pinus sibirica occur in the east. Crown cover is 40–60%; site classes score 4–6. Maximum age of Picea spp. is approximately 400 years old (Romanovsky 2002; Volkov 2008). Picea spp. dominates in the undergrowth. Salix caprea, Alnus incana, and Sorbus aucuparia also can be found in the undergrowth. Cover of the field layer is 60–100%; Vaccinium myrtillus, V. vitis-idaea, Rubus chamaemorus, Equisetum sylvaticum, Carex globularis, etc. can occur as dominants. Mosses cover 100%; the proportion of sphagnum and green mosses greatly varies. Sphagnum girgensohnii, S. angustifolium, and S. wulfianum often dominate. Polytrichum commune is a common species among the green mosses; it can form a continuous cover in the bottom layer. Hylocomium splendens and Pleurozium schreberi often occur. Polytrichum-sphagnum pine forests (Pineta polytrichoso-sphagnosa) are mainly described from the northwestern part of the region (Ermakov and Morozova 2011). They grow on poorly drained sites in the plains and on gentle slopes of ridges with peaty and peaty gley soils. In the described forests, groundwater levels vary from 0.2 to 0.7 m. In these sparse tree stands, crown cover varies from 20 to 60%; site quality classes are 3–4 (Romanovsky 2002). Pinus sylvestris dominates, Picea abies often co-dominates, and Betula pubescens often occurs. The undergrowth mainly consists of Picea abies; Betula pubescens also occurs; Pinus sylvestris of low vitality can be also found. The understorey consists of Juniperus communis and Sorbus aucuparia; Salix aurita and S. caprea sometimes occur. The cover of the shrub layer is 10–30%. The field layer covers 40–90%. In the north, Vaccinium myrtillus, Rubus chamaemorus, and Equisetum sylvaticum dominate. V. uliginosum, Ledum palustre, V. vitis-idaea, Linnaea borealis, Empetrum hermaphroditum, etc. often occur together with Avenella flexuosa and Carex globularis. The proportion of

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boreal small herbs and ferns increases toward the south. Moss cover is 80–90%; Polytrichum commune and Sphagnum girgensohnii dominate; Pleurozium schreberi and Hylocomium splendens often occur. Lichens can also be found in the bottom layer. In the middle taiga, moss cover varies from 40 to 90%. When Equisetum spp. and Sphagnum spp. co-dominate, sphagnum forms flat “carpets,” sometimes with hummocks; Sphagnum girgensohnii, S. angustifolium, and S. centrale are the most abundant species. S. warnstorfii, S. russowii, and S. magellanicum often occur; Polytrichum commune is the most common among the green mosses and forms cushions. Hummocks are more developed in pine forests with co-dominance of Sphagnum spp. and Vaccinium myrtillus in the ground layer. Polytrichum-sphagnum birch forests (Betuleta polytrichoso-sphagnosa) are described from flat depressions on watersheds and from flat or very gentle slopes (Sambuk 1932; Korchagin 1940; Degteva et al. 2001). Sites are wet to excessively wet. Crown cover is 40–60%; Betula pendula dominates in the overstorey, often with an admixture of B. pubescens and Picea spp.; Pinus sylvestris and Populus tremula rarely occur. The understorey consists of Sorbus aucuparia, Rosa acicularis, Juniperus communis, Salix aurita, and Lonicera pallasii. The undergrowth is dominated by Picea spp. and rarely by Betula spp. Cover of the field layer varies from 20 to 80%; Equisetum sylvaticum, Vaccinium myrtillus, Carex globularis, and C. nigra dominate at different patches; boreal small herbs and ferns such as Trientalis europaea, Maianthemum bifolium, Oxalis acetosella, and Gymnocarpium dryopteris always occur. Moss cover is 60–90%; sphagnum mosses and Polytrichum commune dominate. Sphagnum girgensohnii is the most constant and abundant one of the sphagnums. Pleurozium schreberi occurs with a high constancy but a low abundance. Subsection of dwarf shrub-sphagnum forests includes plant communities classified as the ass. Oxycocco quadripetali–Pinetum K.-Lund 1981, the ass. Ledo– Pinetum sylvestris R.Tx. 1955 (syn. Chamaedaphno–Ledetum Korot. 1986), and the ass. Sphagno baltici–Pinetum sylvestris Saburov ex Zaugolnova nov. prov. The subsection is characterized by the co-dominance of oligotrophic dwarf shrubs and shrubs such as Vaccinium uliginosum, Ledum palustre, and Andromeda polifolia in the field layer together with a practically continuous sphagnum cover in the bottom layer. The sphagnum cover is very diverse in species composition; Sphagnum magellanicum followed by S. angustifolium are the most abundant ­species. Carex globularis also always occurs and Eriophorum vaginatum often occurs with a low cover. Soils are the same as in the polytrichum-sphagnum forests; the main area is occupied by soils with peaty topsoils such as Histic Gleysols. Gleyic Gleysols often occur in the north of the boreal region; these soils have permafrost within 200 cm of the surface. Dwarf shrub  – sphagnum spruce and spruce-fir forests (Piceeta (P.-Abieta) fruticuloso-­sphagnosa) are currently described from the eastern part of the boreal region, mainly in the north; they are less common in the south. These forests usually occur in the lower parts of slopes on poorly drained sites. Cover of the overstorey is low (30–40%). Picea obovata dominates with an admixture of Betula pubescens and Pinus sylvestris. Sometimes there is a second sublayer containing the same spe-

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cies. Undergrowth of Picea obovata is present. The shrub layer covers 10–15%; it includes Betula nana, Juniperus communis, and willows (Salix myrtilloides, S. lapponum, S. aurita, etc.). The field layer covers 55–60%; Vaccinium uliginosum, Ledum palustre, and Andromeda polifolia dominate singly or in various combinations; Empetrum spp., Carex globularis, Eriophorum vaginatum, and Rubus chamaemorus always occur. Mosses show a nearly continuous cover with absolute dominance of sphagnum mosses. Sphagnum magellanicum and S. angustifolium show the highest and second highest cover scores; here and there, S. balticum is also abundant. Polytrichum commune also always occurs and sometimes dominates in the bottom layer (Saburov 1972; Martynenko 1999b). Dwarf shrub – sphagnum pine forests (Pineta sylvestris fruticuloso-sphagnosa) are usually found at depressions that have no outlet or are poorly drained and are located along the margins of oligotrophic bogs over the entire boreal forest region (Pyavchenko 1957; Romanovsky 2002; Ermakov and Morozova 2011; Kucherov 2012). Hummocky microrelief and a mosaic structure of the ground layers are typical for these forests. The sparse tree stands score low site class values (5–5a). Cover of the overstorey is 10–40% in the northern taiga and 30–70% in the middle taiga. Pinus sylvestris dominates in the overstorey with an admixture of Betula pubescens. Pinus sibirica sporadically occurs in the east. The undergrowth consists of Pinus sylvestris and Picea spp. The shrub layer covers 10–30%; Betula nana is a common species; Salix cinerea and S. caprea also occur in the south. Cover of the field layer varies from 40 to 80%. Ledum palustre, Andromeda polifolia, and Chamaedaphne calyculata dominate that layer. Oligotrophic, boreal, and piny dwarf shrubs such as Vaccinium uliginosum, V. myrtillus, and V. vitis-idaea, respectively, and hygrophilous-­ oligotrophic species such as Carex globularis, Eriophorum vaginatum, and Rubus chamaemorus always occur. All of them can dominate or co-dominate in the field layer. Sphagnum mosses such as S. angustifolium, S. fuscum, S. magellanicum, and more rarely S. capillifolium, S. fallax, and S. girgensohnii dominate in the bottom layer. S. fuscum is the most oligotrophic species and it is a typical species in the north of the region. Lichens of the genera Parmeliopsis, Bryopogon, and Cetraria are common on the trunks of old trees. Lobaria pulmonaria and Cetraria pinastri also occur (Kolesnikov 1985). Dwarf shrub  – sphagnum Siberian pine forests (Pineta sibiricae fruticuloso-­ sphagnosa) are described from the northeastern part of the boreal region (in the Komi Republic) (Korchagin 1940; Nepomilueva 1970, 1974; Martynenko 1999b). They occur at lower parts of slopes and along the margins of bogs, on loamy as well as on sandy substrates. Crown cover is not more than 50%. Pinus sibirica dominates. There is an admixture of Picea obovata (30–40% of the stands) on peaty gley soils; Betula pubescens also can be found. On the whole, Picea obovata co-­ dominates on loamy soils, and Pinus sylvestris with Betula pubescens co-dominate on sandy soils. The height of Pinus sibirica is 14–16 m and its trunk diameter is 12–46  cm (Nepomilueva 1970, 1974). Regeneration of Pinus sibirica and Picea obovata is rare and depressed. The shrub layer is poorly developed; Sorbus aucuparia and Rosa acicularis rarely occur. The field layer covers 30–40%. It can be dominated by Vaccinium myrtillus, V. uliginosum, or Ledum palustre depending on

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the level of the stagnant water table. Rubus chamaemorus, Carex globularis, and Eriophorum spp. also occur in the field layer. Moss cover is high (70–100%); Sphagnum warnstorfii, S. girgensohnii, and S. angustifolium dominate in different proportions (Nepomilueva 1974). Subsection of herb-sphagnum forests includes communities classified into the following three associations: ass. Sphagno baltici–Pinetum sylvestris ass. prov. var., ass. Molinio caeruleae–Betuletum pubescentis Kutenkov ex Martynenko nov. prov., and ass. Junco filiformitis–Pinetum sylvestris Bezdelova ex Martynenko nov. prov. Forests of this subsection have a clear spatial structure of their ground layer: there is an alternation of hummocks and seepage areas. Oligotrophic (Molinia caerulea, Carex globularis, Eriophorum vaginatum, etc.) and meso-oligotrophic hygrophilous (Juncus filiformis, Carex nigra, Menyanthes trifoliata, etc.) herbs and sedges dominate on hummocks and in seepage areas as well; sphagnum mosses together with hygrophilous herbs and sedges fill the seepage areas. Oligotrophic dwarf shrubs and shrubs such as Vaccinium uliginosum, Ledum palustre, and Chamaedaphne calyculata always occur. Soils are the same as in the other sphagnum forests: soils with peaty topsoil such as Histic Gleysols occupy the main area of these forests. Herb-sphagnum spruce and spruce-fir forests (Piceeta (P.-Abieeta) herboso-­ sphagnosa) are described from the Arkhangelsk region and in the southwest and east of the Komi Republic (Smagin 2000). These forests are located at edges of fens and in gullies with stagnant high water tables which are common on frozen soils in the north. The level of the water table is 0.1–0.2 m. Picea spp. dominates in the overstorey with an admixture of Betula pubescens and sometimes Pinus sylvestris. The cover of the overstorey is low (20–40%); and the trees are 5–8 m tall. A shrub layer is usually absent. Cover of the field layer is 50–70%. Hummocky microrelief is well developed; water can stagnate in the depressions. Menyanthes trifoliata dominates in the field layer; Comarum palustre and Equisetum fluviatile occur with less abundance; oligotrophic dwarf shrubs and shrubs such as Chamaedaphne calyculata, Ledum palustre, Oxycoccus palustre, etc. and oligotrophic sedges and grasses such as Carex pauciflora, C. chordorrhiza, C. rostrata, and Calamagrostis canescens always occur. Mosses cover 70–90%; Sphagnum angustifolium, S. ­centrale, and S. warnstorfii dominate in various proportions; Aulacomnium palustre is usually common. Herb-sphagnum birch forests (Betuleta herboso-sphagnosa) are described from Karelia and the south of the Arkhangelsk region (Smagin 2000; Kutenkov 2005; Morozova et al. 2008). There forests usually occupy inter-ridge depressions with excessive, stagnant, or slightly flowing moisture; they also occur in depressions at watersheds. Cover of the overstorey is 40–70%; tree height is 16–20  m; Betula pubescens dominates; Pinus sylvestris and Betula pendula can occur as an admixture. The undergrowth consists of Picea abies, Betula pendula, Pinus silvestris, and Alnus incana. The field layer covers between 40 and 75%. Water-marsh and oligotrophic species dominate. Among the dominants are Molinia caerulea, Carex nigra, C. globularis, Equisetum sylvaticum, Juncus filiformis, Comarum palustre, etc. Boreal and piny dwarf shrubs (Vaccinium myrtillus and V. vitis-idaea) and nitrophi-

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lous and nemoral plants such as Filipendula ulmaria and Dryopteris carthusiana often occur. Mosses cover 40–90%; Sphagnum warnstorfii dominates together with S. angustifolium and S. centrale. Sphagnum mosses usually form continuous carpets. Green mosses such as Pleurozium schreberi, Dicranum scoparium, Aulacomnium palustre, and Polytrichum commune often occur; they form hillocks on stumps and snags (Kutenkov 2005). Herb-sphagnum Siberian pine forests (Pineta sibiricae herboso-sphagnosa) are described from the east of the boreal region where they occupy the low parts of gentle slopes on peaty gley soils (Degteva 1999). Groundwater level is 0.0–0.2 m. Tree crown cover varies from 30 to 60%. Pinus sibirica and Picea obovata co-­ dominate; Pinus sylvestris and Betula spp. can occur. Tree height is 7–17 m. The understorey consists of Sorbus aucuparia, Rosa acicularis, Frangula alnus, and Juniperus communis. Picea obovata undergrowth develops only on hummocks and snags. The microrelief determines the composition of the field layer: oligotrophic, boreal, and piny dwarf shrubs, shrubs, herbs, and sedges (Vaccinium uliginosum, V. myrtillus, V. vitis-idaea, Oxycoccus palustris, Ledum palustre, Rubus chamaemorus, Carex globularis, C. cespitosa, etc.) grow on the elevated parts; oligotrophic and water-marsh herbs (Eriophorum vaginatum, Comarum palustre, Epilobium palustre, Equisetum palustris, E. fluviatile, Menyanthes trifoliata, Calla palustris, Bistorta major, etc.) grow in the depressions. The moss layer covers 100%; it consists of sphagnum mosses such as Sphagnum warnstorfii, S. girgensohnii, etc.; Polytrichum commune occurs as an admixture (Martynenko 1999b). Herb-sphagnum pine forests (Pineta sylvestris herboso-sphagnosa) occur over the entire boreal forest region; they are widest distributed in the Arkhangelsk region (Smagin 2000; Kutenkov 2005; Ermakov and Morozova 2011; Kucherov and Kutenkov 2011). These forests occupy depressions on watersheds; they also occur along narrow streams and margins of mesotrophic and oligotrophic bogs. Tree crown cover varies from 20 to 70%. Pinus sylvestris dominates; Picea abies, Betula pubescens, B. pendula, and Populus tremula occur as an admixture in the overstorey. The height of the pines of about 100 years old varies from 14–16 till 20–24 m depending on the degree of moistening of the site: trees are higher on the better drained sites. Picea abies undergrowth always occurs; undergrowth of Betula ­pubescens and Alnus incana also can be found. The shrub layer is very open; it consists of Sorbus aucuparia, Juniperus communis, Rosa acicularis, Salix aurita, Frangula alnus, etc. The field layer covers 50–70%; a hummocky microrelief is well developed; stagnant water can be found in the depressions. In the depressions Menyanthes trifoliata, Comarum palustre, and Equisetum fluviatile co-dominate; Carex lasiocarpa and C. chordorrhiza always occur and C. rostrata, C. pauciflora, C. appropinquata, and C. cespitosa can be also found. On the hummocks, Chamaedaphne calyculata, Ledum palustre, and Oxycoccus palustre always occur; on the upper parts, Vaccinium myrtillus and boreal small herbs and ferns can be found. Mosses cover 60–90%; sphagnum mosses dominate. Sphagnum angustifolium and S. centrale are the most abundant; S. squarrosum, S. warnstorfii, and S. russowii often occur; green mosses such as Pleurozium schreberi, Hylocomium splendens, and Dicranum scoparium always occur (Kutenkov 2005).

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3.1.7  Conclusion Forest vegetation communities spread over the boreal region of European Russia were described on the basis of the dominant ecological-coenotic approach. Six sections of forests were distinguished according to the dominance in the ground layer. The sections are as follows: lichen, green moss, large fern, boreal tall herb, boreal swamp, and sphagnum sections. The vegetation in most forest sections is subject to stress factors: nutrient-poor and dry or nutrient-poor with stagnant moisture conditions are those which are typical for the vegetation of lichen and green moss or sphagnum sections, respectively. The tree species diversity is rather high, and most coniferous and deciduous trees, such as Pinus sylvestris, P. sibirica, Picea spp., Abies sibirica, Larix sibirica, Betula spp., and Populus tremula, occur in practically each forest section. In forests of the lichen and green moss sections, the abundance and diversity of lichens and bryophytes are rather higher than that of vascular plants which actually rarely dominate in those forests. The dwarf shrubs Vaccinium vitis-idaea and V. myrtillus, evergreen species of the genera Pyrola and Lycopodium, small boreal herbs, and ferns such as Trientalis europaea, Maianthemum bifolium, Gymnocarpium dryopteris, etc. are common among the vascular plants. Practically all these forests show traces of fire and felling in the vegetation or in the soil. Communities of the lichen section, followed by the green moss forest section, usually dominate at the first and subsequent stages of the post-fire succession. In the boreal region, forests slowly recover after severe disturbances, and as a consequence, repeated fires often interrupt the succession during these first stages. As a result, forests of the green moss and lichen sections prevail over the entire area of the boreal European Russian forests. In communities of the sphagnum section, sphagnum mosses dominate the ground layer, whereas the abundance and diversity of vascular plants are low, as observed in the lichen and green moss forests. Subsections in this section differ in species which accompany sphagnum mosses, such as the green moss Polytrichum commune or dwarf shrubs and shrubs such as Vaccinium uliginosum, Ledum palustre, and Andromeda polifolia or herbaceous species such as Molinia caerulea, Carex globularis, Eriophorum vaginatum, and others. Sphagnum forests are common in depressions with stagnant moisture, but these forests have not been well investigated. However logging and fires usually lead to waterlogging, especially in depressions, and that adversely affect the growth and development of many plant species. Large fern forests belong to a new and poorly investigated boreal forest section. In more details these forests are described from the low mountains of the Urals, where they occupy well-drained tops of heavily eroded slopes (see Sects. 3.4 and 3.5). A shallow soil profile, charcoal in the soil, and fire scars on trees, together with a lot of fallen trees with tree uprooting, show that these forests experienced severe fires and windthrows in the past. Probably, in combination these two kinds of severe disturbances led to the development of extensive areas of bare soil that later became occupied by spore plants, of which Dryopteris dilatata ultimately won the competition. The development of small boreal herbs, dwarf shrubs, and a tree undergrowth is greatly suppressed by this large powerful fern.

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The boreal tall herb section includes unique and species-rich forest types which are located on watersheds and are dominated by mesophilous tall herbs and ferns in the ground layer. The syntaxonomical position of these forests was first defined by Zaugolnova et al. (2009), and localities of these forests were recently mapped by Smirnova et  al. (2013). Boreal tall herb Picea obovata-Abies sibirica forests are described in detail from the Pechora-Ilych State Nature Reserve in the Ural Mountains (Smirnova et al. 2011; see Sect. 3.4) and from the plains of the Komi Republic (Smirnova et  al. 2006); tall herb Picea abies forests are also described from Karelia (Smirnova and Korotkov 2001; see Sect. 3.5). All these forests are found in places of fire refuges. There are several sublayers in the ground layer of vegetation dominated by the boreal tall herbs and ferns Cirsium oleraceum, C. heterophyllum, Diplazium sibiricum, Aconitum septentrionale, Cacalia hastata, Paeonia anomala, Thalictrum minus, Dryopteris dilatata, etc. The nemoral species Milium effusum, Lathyrus vernus, Stellaria holostea, etc. occur in the second sublayer, with the small boreal herbs Oxalis acetosella, Maianthemum bifolium, etc. growing below the taller species; dwarf shrubs and green mosses often occur on the deadwood. The spring-growing and -flowering nemoral herbs Corydalis bulbosa, Gagea lutea, G. samoedorum, Anemonoides altaica, and some others are also found in these forests. Structural diversity caused by treefalls with uprooting is well developed in tall herb dark coniferous forests. Boreal swamp forests are mainly located in the valleys of rivers and streams where combinations of running water and periodic waterlogging affect the vegetation. According to these features of the water regime, we distinguish two subsections within the swamp forest section: nitrophilous tall herb and genuine swamp tall herb forests. In addition to microsite mosaics caused by treefalls, water-depending microsites with different ecological conditions determine the highest level of species diversity in these forests. Meso-hygrophilous and hygrophilous species dominate the ground layer; shrubs and herbaceous species of hemiboreal and nemoral forests also occur. The overstorey consists of Picea spp., Abies sibirica (in the east), and deciduous trees, the ensemble of which is richer than in all other forest sections: with Padus avium, species of the genus Salix, Alnus incana, and even A. glutinosa in the south of the region. Thus, besides the common and repeatedly described poor boreal forests of the green moss, lichen, and sphagnum sections, there are boreal forests that are rich in species and dominated by tall herbaceous species which occur not only in the river valleys but on the watersheds as well. In the absence of fire, the tall herb forests preserve high levels of structural diversity, an uneven-aged structure of the tree layer, and a high diversity of microsites and species in the ground layer of the vegetation.

3.2  Features of the Historical Land Use in the Boreal Region A special feature of the historical land use in the boreal region is the relatively late spread of a productive economy there in comparison with the more southern areas. For a long time, the main occupations of the population were hunting and fishing,

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including mammal hunting on the sea coast. For the north of European Russia, there are practically no studies that reconstruct the human impact on nature in the time before the development of a productive economy, whereas it is well known that the area had a rich variety of archeological cultures. The northern “forest Neolithic” (fifth–second millennium BC) is well studied by archeologists (Vlasova 1998, 2001). Original Neolithic cultures with comb ceramics were spread over a wide area between the Ural Mountains and the Baltic Sea: the Karelian, Kargopol, Beloe More (White Sea) archeological cultures. At the turn of the second–first millennium BC, Northeastern Europe became inhabited by Finno-Ugric tribes from the Urals and Western Siberia, which mingled with the local population (Khaidu 1985; Vlasova 2001). The influence of the Old Russian state in the north of European Russia has been expanding since the tenth to eleventh centuries. At that time, Slavic settlements began to emerge there. In the Middle Ages, much of the area was a part of the possessions of the Novgorod Republic, and it became property of the Moscow Principality at the end of the fifteenth century. It is well known that fire is a major driver of boreal forest ecosystem dynamics. Historically forest fires in the north of the forest area, as well as in the south, mainly were burnings of forests in a slash-and-burn agriculture and for the expansion of pastures for cattle and deer raising (Mandych 1989; Smirnova 2004).

3.2.1  Slash-and-Burn Agriculture Slash-and-burn agriculture is historically the most widespread form of agriculture in the boreal area and probably the first one. The use of slash-and-burn agriculture in Northern Europe at 6000 years BP has been proven (Eriksson et al. 2002). Good evidence of the existence of agriculture in the central and eastern parts of Finland and Karelia dates to 1500–1000 years BP (Poutiainen et al. 1995; Taavitsainen et al. 1998). In lake sediments in the Savo region located in the southeast of Finland and in North Finnish Karelia, pollen of cultivated cereals appear in horizons of the beginning to the middle of the first millennium AD; the oldest traces of cultivated plants are recorded in a horizon of the Bronze Age (Taavitsainen et al. 1998); but agriculture is becoming regular here only in the thirteenth century. In the area of Ladoga Karelia, the emergence of agriculture coincides with the beginning of the Iron Age, and it had spread relatively widely by the eighth century AD (Uino 1997). Makarov et al. (2001) suggest that in the early Iron Age, agriculture was familiar to the Belozerye population living in the northwest of the modern Vologda region. Makarov et al. (2001) also noted that in the early Iron Age, there was a trend of converting elevated wooded areas on the edge of upland terraces into agricultural lands because these were well-illuminated and well-drained spots. In the territory of the Komi Republic, slash-and-burn agriculture probably appeared in the fifth to sixth centuries AD (Smirnov 1952). This slash-and-burn agricultural system has existed for a long time: according to evidence from old residents in the north of European Russia, it has continued until the Second World War and in some areas up

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Fig. 3.1 B.  Lindholm’s drawing “Slash-and-burn at Iisalmi” (eastern Finland), nineteenth century

to 1960. This system also played a major role in changing the landscape until the 1920s in Northern Fennoscandia (Lehtonen 1998; Uotila et al. 2002; Fig. 3.1). The slash-and-burn system had certain advantages because of which farmers in wooded regions so long preferred it to other farming systems. These were the following (according to Ofman et al. (1998), with additions): (1) yields were high in the first years, and thus sizes of fields could be much smaller than in other cropping systems; (2) it offered the opportunity to girdle and cut the trees outside the growing season, and so these laborious operations could be done in winter when peasants were less busy; (3) there was no, or just very little, need for tillage; (4) no special instruments and means of production were required; and (5) weeds were few in the early years, as a result of the firing of the topsoil and the relative remoteness of the fields from the seed sources of ruderal herbs. This made it possible to cultivate crops which are extremely sensitive to weed invasions, such as switchgrass (Panicum) and wheat (Triticum). An important motive for the application of slash-and-burn agriculture in the wooded areas of European Russia was the possibility of tax evasion as taxes were charged on permanent arable lands. At some periods of time, slash-and-burn fields were also taxed, but in the northern wooded regions, peasants often had the opportunity to locate their fields at secret places away from the settlements. There are numerous options to remove trees in slash-and-burn agriculture: from the simple burning of the forest stand to girdling, drying out, and logging the trees.

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One man can, without much effort, kill hundreds of trees by ringbarking their trunks. He does not even need an ax, because partial removal of the bark is possible with knives or scrapers. People used stone axes and later metal axes for tree cutting (Semenov 1974). Neither labor nor the sometimes great distances between the fields and places of permanent settlement were limiting factors. In many cases, slash-and-­ burn fields and hayfields were located far away from the settlements, at distances of up to several tens of kilometers. Rivers were the main transport routes. Hayfields were usually located in the floodplains, and slash-and-burn fields were located at an accessible distance away from them. Usually trunks were separated from their twigs and branches and then used for construction or for firewood. The rest of the woody material was evenly spread over the cut area and burned. The optimum depth of the burn-through soil was two–three fingers (about 5 cm). There was no need to pre-scarify the soil, as the grain was sown in warm or cooled ashes. Then the field was harrowed and enclosed to prevent damage by wild or domestic animals. The plot was sown for 1–3 years on sandy soils and up to 5–8 years on loamy soils (Tretyakov 1932; Semenov 1974; Milov 1998). Swamps were also used for slash-and-burn agriculture (Asheim 1978; Larsson 1995). When plots became too weedy and crop capacity strongly diminished, the plots were left to be overgrown by forest, aiming to restore soil fertility. Evidently, people initially took more and more virgin areas into use, but gradually they had to return to the previously used lands. Over time the total duration of the economic cycle has steadily decreased, from more than 100  years to 25  years (Tretyakov 1932; Semenov 1974; Istoriya krestyanstva  v Evrope… 1986; Milov 1998; Danilova and Sokolov 1998). The most important limitation of slash-and-burn agriculture was the need for large areas of vacant land. Calculations show that this agricultural system can sufficiently provide the population with grain when the population density is not higher than two persons per square kilometer (Kulpin and Pantin 1993) to five people per square kilometer (Lehtonen 1998; Pitkänen 1999). The introduction of rye (Secale) in the crop rotation system, especially its winter form, probably caused changes in the technology of slash-and-burn agriculture. Rye entered the forest area of Europe as a weed in other crops. Later farmers were attracted by its high competitiveness on poor soils and in areas with an unfavorable climate. In Central Europe rye has been widely used as a grain crop since the beginning of the Iron Age and or the Roman period (Behre 1992). Later, in the ninth to tenth centuries, it spread to the north and east of Europe. The transition from spring wheat, millet, and barley into winter rye made it necessary to shift the time of the burning of felled trees in slash-and-burn fields from spring to midsummer (Hamilton 1997), which is a season of greater fire danger in the boreal area (Melekhov 1947). As a result, the frequency of forest fires due to “running fires” increased after the introduction of winter rye as a grain crop (Bobrovsky 2010). There is plenty of evidence of frequent unintentional burning of forests in slash-and-burn agriculture (Larsson 1989; Yaroshenko et  al. 2001; Bobrovsky 2010). As a result, the burnt areas were often tens to thousands of times greater than the actual cultivated areas.

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To list all features of the ecosystem and landscape transformation associated with the slash-and-burn system is difficult as it not just concerns agricultural practices. It was a system of environmental management including agriculture, logging, burning, and in many areas also grazing and mowing. The main effects of the slash-­ and-­burn system resulted from insufficient “time for rest” or fallow periods for used lands in order to restore the total ecosystem biomass, soil structure, and soil fertility. This led to a transformation of the upper soil horizon, podzol formation, the loss of nitrogen and other elements, smoothening of the microrelief, impoverishment of the soil fauna (mostly macrofauna), an increase in surface runoff, and soil erosion. Furthermore, removing the possibility of natural tree windfalls with uprootings led to a transition of the accumulation of organic material from inside the soil to accumulation at the soil surface; and it increased the degree of forest fire hazards (Mikhailov 1977; Osipov and Gavrilova 1983; Bobrovsky 2010, etc.). Although the total area of cultivated lands in slash-and-burn agriculture was relatively small and the length of the cycle seems great, this system of farming has deeply transformed vast areas for hundreds of years. With the proliferation of different farming systems and the increase in population density in forest regions, the slash-and-burn system largely lost significance though it remained a tool to develop new agricultural lands from forest until the early to mid-twentieth century in some areas in the north and east of Europe.

3.2.2  Tillage Agriculture The spread of tillage (plough) agriculture in the boreal region of European Russia dates to the end of approximately the first millennium to the first centuries of the second millennium AD.  It is associated with a Slavic colonization. The main ploughing instrument was the sokha, which was a light wooden ard that has been used over the northwest of the Russian Plain since the eighth century (Krasnov 1987; see https://en.wikipedia.org/wiki/Sokha; Fig. 3.2). In the northwest and the north of European Russia, the development of the moraine landscape by tillage agriculture began on the tops of hills and ridges. According to the Scribe’s Books of agrarian inventory, in the fifteenth century, there were small villages with small tracts of permanent arable lands at spots cleared from the forest. By that time, all the watershed forests located in the southern part of Northwest Russia had periodically been involved in slash-and-burn and shifting cultivation (Dolotov 1984). Tillage agriculture was widely spread in the so-called Zaonezhje churchyards: from Ladoga to Lake Onega, around Lake Onega, and from Lake Onega to the southern coast of the White Sea. In the southern and eastern parts (now the northwest of the Vologda region and the west of the Arkhangelsk region), the population was predominantly Russian, while in the north and west of the region (the southeast of Karelia), it was mainly Karelian. In the present territory of the Komi Republic,

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Fig. 3.2  Miniature from the illustrated chronicles of the sixteenth century [Litsevoy Letopisnyi Svod] (From Istoriya krestyanstva v SSSR... 1987)

tillage farming has been expanding since the fifteenth century (Smirnov 1952; Belitser 1958). Toward the middle of the nineteenth century, shortage of land caused by the growth of villages led to the ploughing up of all hillocks in forested land in the northwest of European Russia (Dolotov 1988). Arable lands around the villages consisted of individual tracts separated by meadows in the depressions. In the rest of the boreal region, patchy farming prevailed. With the abolition of serfdom in 1861, remote arable lands started to be abandoned and gradually became overgrown by forest (Dolotov 1988). By the 1930s, farming had been almost completely stopped in the north of European Russia. Presently agricultural lands in the boreal region occupy small areas (from 1.1% in the Komi Republic to 11% in the Arkhangelsk region according to Mandych (1989)), but the proportion of arable land in the Middle Ages was much higher than today. It is important to take this into account when studying the history and dynamics of forests in the boreal region.

3.2.3  Traditional Cattle and Reindeer Breeding There were two main variants of animal breeding in the boreal region: traditional livestock keeping (first of all cattle and sheep) in the more southern regions, while reindeer breeding was typical for the north.

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The question of the origin of reindeer breeding has not yet been resolved. There is evidence that by the end of the first millennium BC in the northeast (with the Khanty, Mansi, and other nations) and around the middle of first millennium AD in the northwest (in the Saami nation), reindeer breeding and sledges already were in use (Shumkin 1991; Fedorova 2000). Clearly, at that time the economic-cultural type of existence was formed that continued to be practiced on the border of the northern taiga and tundra till the seventeenth to eighteenth centuries. It is characterized by the seasonal migration of most of the populations following the migrating herds of wild and later domesticated reindeer: in spring from the forest-tundra to the tundra and back in the fall (Fedorova 2001; Alekseev et al. 2010). Each owner had the required minimum of domesticated reindeer of 15–20 animals. These deer were mainly used as a transport vehicle and as a decoy while hunting. Probably, reindeer breeding with larger herds appeared in the forest-tundra area not earlier than in the fifteenth century. There also were hunter-fishers using reindeer as a transport vehicle in the northern taiga. In the European Russian north, forest grazing by cattle also has been widespread at least up to the 1930s (Shennikov and Bologovskaya 1927). Cattle were grazed in forests including forest bogs, burned areas, clearings, etc. Swamps and floodplains also were widely used for mowing (Ericsson et al. 2000). Thus, historically cattle and reindeer breeding were widespread in the boreal region and affected to a high degree the forest ecosystems. The most remarkable change resulting from the burning the forest for pastures and the large-scale felling of trees for household needs at the border of the forest region was the transition of the northern border of the forested area to the south (Gorodkov 1954; Sirois and Payette 1991; Ericsson et al. 2000; Lindbladha et al. 2003).

3.2.4  Fires Fire long has accompanied man: the ancient hunters used it for driven hunting (battue), people prepared food over a fire and warmed themselves by the fire, and fire cleared space for new settlements. Probably until the fifteenth century, the bulk of fires in the boreal region was associated with agriculture or animal husbandry: clearing lands for grazing and maintaining pastures (Bobrovsky 2010). Forests were also burned to stimulate the production of forest berries (Korchagin 1940). Over time, the ways in which the boreal forest was exploited became more diversified, and the probability of human-initiated fires also increased: since the fifteenth century extraction of tar spread; industrial logging began in the end of the seventeenth century; the first railroads were built at the end of the nineteenth century. In areas with railways, the proportion of fires from sparks from the locomotives was between 50 and 70% (Melekhov 1939; Molchanov and Preobrazhenskiy 1957). Settlements have been a constant source of fires. It was shown that in the Russian European north, up to 60% of all fires arose within a radius of 5 km around a settlement and 93% of all fires within 10 km (Kushnikov 1956; Kurbatsky 1964; Vakurov 1975).

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From ancient times, hunters and fishermen caused fires and later also tourists, travelers, and others; in some areas more than 50% of the fires occurred near rivers and streams, which were the main routes for travel (Yaroshenko et  al. 2001). According to various authors, in the boreal region of European Russia, wildfires from lightning consist of not more than 2–3% of the total number of fires (Guman 1926; Kushnikov 1956; Molchanov and Preobrazhenskiy 1957; Vakurov 1975). Fire history in the north of European Russia is poorly studied. It is clear that fires have covered a large area of the northern forests, but frequency and intensity of fires are not well studied for individual regions. According to Tkachenko (1911), areas of fires comprised 10,000 to 30,000 hectares in historical time. By the end of the twentieth century, the area of a single fire in the boreal region was usually more than 10,000 hectares (Heinselman 1981; Attiwill 1994). In the north of European Russia, in some years, the total area of fires exceeded the size of the annual allowable cut (Guman 1926; Vakurov 1975). The fires in pine forests often occurred in tree stands affected by fires before. The frequency of fires in the boreal region is highly variable. Analyzing the Russian chronicles, Bogolepov (1908) showed that there were only 15 dry years with fires between the end of the eleventh century to the end of the sixteenth century in central and northern Russia: in 1092, 1124, 1161, 1193, 1224, 1298, 1325, 1363, 1368, 1372, 1384, 1430, 1508, 1533, and 1538. Evidently, only the largest fires, when villages were burned along with the forests, were marked in the annals. Based on dendrochronological studies on samples of wood discovered during archeological excavations in Novgorod, Kolchin (1963) concluded that there were no less than 40 years with large fires during that period. According to various authors (Molchanov 1970; Melekhov 1971, etc.), there were about 60 dry years with forest fires from 1614 till 1900 in the European Russian north. The largest fires in the region were in 1614, 1647, 1668, 1688, 1690, 1710, 1756, 1790, 1800, 1825, 1840, 1860, 1877, 1882, 1886, 1888, 1891, and 1899. In historical time, the average interval between fires was around 20 years, and outbreaks of fires in the boreal region were observed in the same years as in the hemiboreal region (Tyurin 1925). Fire frequency depended on forest type, relief, soil moisture, and the presence of natural barriers for fire (streams, rocks, etc.). Dry pine forests burned most frequently and swamps least frequently in the boreal region. Fire history can vary significantly for sites that are only tens of meters apart. A typical feature of surface fires in the northern forests, except for some areas with a flat topography and dry sandy soils, is their widely varying patchy distribution over the affected area (Tkachenko 1911; Vakurov 1975). As a result, in a relatively small area (e.g., within the one forest compartment), one can find groups of even-aged stands of different age classes, and, conversely, large forest tracts regenerated after fire and composed of trees of the same or similar age that can occupy large areas and even entire administrative regions (Vakurov 1975). For the Obozersk forest (Arkhangelsk region) for the past 500 years, Molchanov showed that the average interval between fires in pine forests was about 25 years and in spruce forests between 130 and 200 years (Vakurov 1975). In the upper reaches of the Vychegda River (remote area in the Arkhangelsk region), fire frequency in dry

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pine forests was on average once per 40–44 years and in the more humid pine forests 64–68 years (Melekhov 1971). From 1641 to 1938 in spruce forest in Zaonezhje, the average interval between fires was about 100 years (Vakurov 1975). The occurrence there of large areas of mature spruce forests dominated by Vaccinium myrtillus and green mosses in the ground layer is due to the last large fires which took place at the end of the eighteenth century (in 1781–1800). In the central part of northern Karelia, ground fires recurred about once every 20–40 years in historical time (from the sixteenth century until present), and large fires were recorded one or two times per century (Zyabchenko 1984). For comparison, in Fennoscandia dry Pinus-dominated forests have historically burned at intervals of 20–60 years on average (Zackrisson 1977; Lehtonen and Kolström 2000; Niklasson and Drakenberg 2001), whereas some Picea swamps have escaped fires for thousands of years (Hörnberg et  al. 1995). Many authors have noted the very low frequency of fires in Picea swamps (Hörnberg et al. 1995; Ohlson and Tryterud 1999; Wallenius 2002). For the boreal forests in Europe (Sweden, Finland, mountain parts of Switzerland, etc.), researchers show a correlation of fires with the spread of slash-and-burn agriculture as well as a sharp decrease in the frequency of fires from the end of the nineteenth century (Ericsson et al. 2000; Dahlstrom et al. 2005, etc.). In the boreal forests of northern Sweden, the average fire interval was 34 to 65 years during the late 1600s to late 1800s, but since 1888, no fires had occurred in any of 12 studied stands (Linder et al. 1997). In eastern Finland on dry habitats, charcoal layer records indicate a drastic increase in forest fires about 500  years ago compared with the previous 9500 years (Pitkänen et al. 2002). Marlon et al. (2008) also show that the frequency and area of fires sharply declined after 1870 at a global scale. Reduction in the number of fires coincided with the termination of the massive use of slash-­ and-­burn agriculture (Uotila et al. 2002). Then, from the beginning of the twentieth century, reduction in fire frequency all over the boreal region was also associated with the commercial use of forests for logging and implementation of special programs for the protection of forests from fires together with the legislative prohibition of burning forests for grazing (Ericsson et al. 2000; Dahlstrom et al. 2005). Fires can be considered a major factor in the dynamics of ecosystems in the boreal forest region. In addition, fires were often the cause of waterlogging. It usually happens that a layer of coal underlies the peat deposits in bogs and in waterlogged forests (Segerström et al. 1994, 1996; Segerström 1997; Ohlson and Tryterud 1999). On the whole, modern boreal forests can be seen as a mosaic of patches burned with different frequency and embedding fire refuges, which are the areas escaped from fires for various reasons over the past few centuries.

3.2.5  Felling (Cutting) Active exploitation of the boreal forest by felling has been practiced during the past centuries. Felling was carried out for the purpose of charcoal burning, extraction of tar, timber harvesting, and various homecrafts (Istoriya krestyanstva v Evrope...

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1986). Before the fifteenth century, forests were irregularly exploited; forested areas were most affected by felling near rafting routes and settlements (Wrangell 1841; Guman 1926; Vakurov 1975; Yaroshenko et  al. 2001). The exploitation of the Russian northern forests increased significantly in the fifteenth and sixteenth centuries with the increase of the importance of the salt industry: Russian peasants started to extract salt by evaporation of sea water as from the time of their settling on the seaboard of the White Sea. There were several tens of salterns on the shores of the White Sea in the second half of the sixteenth century. Each saltern consumed about 10,000  m3 of wood per year. In the late seventeenth century, most salterns were closed due to the lack of accessible forests (Yaroshenko 1999). The volume of industrial wood harvesting has been drastically increased since the eighteenth century. It is known that saw mills owned by O. Bazhenov were in operation in Arkhangelsk in 1692 (Alekseev 1948). The first real sawmill plant in the Arkhangelsk region was opened in 1852, and in 1893 there were already about 20 such plants (Molchanov and Shimanyuk 1949). Industrial harvesting of large Pinus sylvestris individuals has been common since the beginning of the nineteenth century; Pinus sylvestris and Picea spp. individuals of different size classes were actively harvested by the end of the nineteenth century (Alekseev 1948). In the eighteenth and nineteenth centuries, until the 1930s, logging focused on harvesting of trees through selective felling, which mainly occurred and scattered over the area (Denisov 1911; Boguslavskiy 1912; Kublitskiy-Piottukh and Nazarov 1912; Faas 1922; etc.). Characteristic of logging activities during those centuries was the absolute dominance of floating as a means of transporting the timber. But cartage was used in some parts of the Arkhangelsk and Vologda provinces for timber delivery from the forest to the port of Arkhangelsk. Even the smallest rivers were often used for floating in which floating the logs was possible only in spring during the flood, and harvest operations (felling) were carried out in winter (Fig. 3.3). Harvested logs were transported to the floatable rivers by horses (Fig. 3.4). Distances up to 15 and sometimes 20 km were considered reasonable distances of transportation, and supplies of logs at distances of 7 to 8 km were considered as quite comfortable. Both drift floating and floating of timber in rafts were used (Yaroshenko et al. 2001). Thus almost the whole basins of the White Sea, the Baltic Sea, and the Volga River were available for cutting and removal of high-quality wood. Presently traces of selective cuttings during this period can be found throughout the region, also in areas far removed from the modern transport infrastructure and modern points of wood consumption. Just a few areas escaped such logging: large isolated areas inside the Pechora River basin and the most waterlogged parts of the major watersheds. Studies have shown that almost all areas of old-growth forests in the north show traces of selective felling, and these usually date from the nineteenth to early twentieth centuries (Yaroshenko et al. 2001; Uotila et al. 2002). In old-growth forests of eastern Finland (North Karelia), the number of old tree stumps equals 130 pieces/ha on average (Rouvinen et al. 2005). Similar data (about 135 pieces/ha) were obtained in a study of Picea abies forest dominated by Vaccinium myrtillus in the ground layer located in the valley of the Vuokiyoki River in central Karelia (Yaroshenko et al. 2001).

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Fig. 3.3  Stacks of wood prepared for spring floating at the Ukhta River, the Komi Republic (The photo was taken in the 1960s by V. Belykh)

Fig. 3.4  Transportation of logs from a cutting area by horses in winter and unloading timber from the sledge in a stack for floating, in the middle of the twentieth century in the Vologda region (From Plekhanov et al. 2003)

The main volumes of cutting came from Pinus sylvestris forests because pine wood and products from pine were in greatest demand on the foreign markets (Yaroshenko et al. 2001). A significant depletion of the available large high-quality pine trees in the White Sea and the Baltic Sea basins has been observed since the beginning of the twentieth century. As a result timber cuttings shifted upward to the origins of floatable rivers and onto the major watersheds, which were least accessible. In addition, the selling diameters of cut trees constantly decreased. That gave timber merchants the possibility to return a second or third time to the forests already exploited by selective felling earlier on (Yaroshenko et al. 2001).

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The low proportion of felled trees, the use of horse-hauling for timber transport to the point where floating started, and the fact that the majority of logging operations were done in winter resulted in a relatively low level of impact of these cutting activities on the structure of the forest ecosystems. The main human impacts dating from those days were fires, usually caused by the inadvertence of loggers. Indeed, in many forests which are farthest from the modern settlements and transportation routes in the Russian north, the majority of forest fire traces date from the late ­nineteenth to early twentieth centuries, while there are no fire traces of a later period or they are extremely rare. Clear-cuttings have been applied in the boreal forest region since the mid-­ nineteenth century (Östlund 1993). The sharpest increase in the intensity of logging occurred from the 1880s till 1913. In 1912–1913, harvesting volumes in the taiga forests in European Russia were comparable to the modern one, amounting to more than 40,000,000 m3 of wood per year (Yaroshenko et al. 2001). The average intensity of forest exploitation for the state-owned forests in European Russia was about 0.5 m3/ha per year, and most of this was located in the boreal region (Godzishevsky 1924); it amounts to about one-third of the increment of forests throughout the north. During that time the extensive forest area in the Pechora River basin was hardly used, while the intensity of forest exploitation in the basins of the Baltic and White Seas was significantly higher than the average. In the 1930s clear-cutting became the main way of logging in the north. At that time concentrated clear-cut logging began to be widely applied (Alekseev and Molchanov 1938; Molchanov and Shimanyuk 1949; Melekhov 1957). Sizes of the clear-cut areas reached several square kilometers there, and clear-cut areas could be adjacent because there were no rules specifying the precise locations of the cuts. Thus, the volume of timber harvesting was not legally limited. Those clear-cuts, and especially concentrated cuts, affected the hydrological regime of the area and strengthened waterlogging (Dmitriev 1953; Dekatov 1957; Shimanyuk 1957). Timber products harvested and manufactured in the European north of Russia became the basis of Russian exports: in the 1930s its share, in monetary terms, accounted for about 30% of the total exports (Yaroshenko et al. 2001). A large proportion of the modern secondary forests is located in the area of concentrated fellings carried out in the middle of the twentieth century. Despite the absolute predominance of clear-cuttings, selective cuttings continued to be applied in areas farthest from the transport routes. Traces of selective cuttings dating from the 1930–1940s can be found in almost the entire area of large forest tracts located on the watersheds of the Northern Dvina, Pinega, Vashka, and Mezen rivers, as well as almost everywhere in the Baltic Sea and Volga River basins (Yaroshenko et al. 2001). Pinus sylvestris remained the main species harvested by selective felling; Larix sibirica was also actively used. Many modern forests dominated by Picea abies were formed as a result of aimed selective logging of pine with preservation of the spruce undergrowth. Such forests are mainly located in the White Sea basin. Often in such forests, pine trees with trunks with various defects can be found which were left in the cutting operation as they had no commercial value (Yaroshenko 1999; Yaroshenko et al. 2001).

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By 1940, the average annual volume of timber harvested in the European Russian taiga was about 2.5–2.7  m3/ha, which is almost twice the current increment (Yaroshenko et al. 2001). As before, the intensity of logging in the south and west of the region was significantly more than the intensity of logging on the poorly accessible northeast, in the Pechora River basin. The volume of timber has dramatically increased since 1946 and reached its peak of 90,000,000  m3 in the late 1960s and early 1970s (Dinamika lesov… 1989; Lesoplzovanie… 1996). At that time the intensity of forest exploitation decreased to 1.25–1.35 m3/ha, but high volumes of cut stems were obtained by increasing the area that was cut. At that, proper work on forest renewal and care of the young stands was very far behind given the amount of logging. The intensive exploitation of forests which were already exhausted by logging has led to a critical depletion of forest resources, and further growth of logging operations became impossible. Despite the fact that the percentage of forested land in the region formally was listed as high, there was a deficiency in economically accessible forest resources for logging in the 1960s–1970s (Mandych 1989). Since the early 1970s, the annual amount of logging in the forests of northern European Russia has declined, and gradually more and more logging companies have closed down. The forest area affected by logging during the last century is estimated at at least two-thirds of the total forest area in Karelia (Gromtsev 2000; Fig. 3.5) and about one-fifth of the forested area in the Komi Republic (Kozubov and Taskaev 1999). Taken together, the proportion of secondary forests formed after heavy human disturbance in the twentieth century is estimated at no less than three quarters of all forested lands in the taiga zone of European Russia (Yaroshenko et al. 2001).

3.2.6  Conclusion The boreal forests in European Russia are substantially transformed mainly as a result of a complex combination of fires and felling. Fire is the most long-standing and most common factor affecting the boreal forest ecosystems. Fires caused by human activities occurred since at least 1.5 thousand years in the boreal region, and they were prevalent almost everywhere. Felling became widespread in the boreal forest region during the past five centuries. It significantly affected forest ecosystems since the middle of the nineteenth century. Because of the slow speed of recovery processes in the north, fires and felling have resulted in a strong transformation of forest ecosystems until the present time. Due to the strong transformation of the vegetation cover, we must include the ecosystems that are least disturbed by man in our investigations: those with the most ancient trees and with minimal signs of human impact on the forests, in order to get a clear picture of the structure, dynamics, and functioning of the boreal forest ecosystems. Below we consider more than 200 years of succession after fire in forests dominated by Pinus sylvestris and located in the west of the European Russian boreal

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Fig. 3.5  Clear-cut area in the Pyaozersk Forestry unit in Karelia (The photo was taken in 2005 by M. Bobrovsky)

region (Kostomuksha Nature Reserve, Sect. 3.3), and then we discuss different types of old-growth forests dominated by Picea obovata and Abies sibirica located in the east of the boreal region (Pechora-Ilych Nature Reserve, Sect. 3.4) and present a comparative analysis of vegetation and soil diversity in different types of old-­ growth spruce and spruce-fir forests located in the west and in the east of the European Russian boreal region (Sect. 3.5).

3.3  S  uccession of the Boreal Forest After Fire in the Kostomuksha State Nature Reserve (Karelia) Kostomuksha Nature Reserve is an expedient object for the study of post-fire succession. Traces of multiple fires, such as fire-scorched trunks and fire damage on pines, an abundance of charred dead standing trees and dead fallen wood, a layer of charcoal under the litter, etc., can be seen everywhere (Kuleshova et  al. 1996; Korotkov et al. 1999). At that, other catastrophic impacts on forest ecosystems, such as storms and clear-cuttings, are absent there, and selective felling was extremely limited in the past and is completely absent since the proclamation of the Reserve in 1983 (Kuleshova et al. 1996). Most fires are located close to roads, rivers, and lakes which attracted local hunters and fishermen.

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3.3.1  Study Area and Methods of the Investigations Kostomuksha State Nature Reserve is situated within the Baltic Crystalline Shield on the eastern slope of the Western Karelian Hills (number 3 in Fig. 2.1). Geographic coordinates of the Reserve are 64°–65°N and 30°–31°E; its total area is 476 km2. Denudation-tectonic relief characterized by the alternation of ridges and depressions dominates in the Reserve (Belousova et al. 1988). Depressions between elevated massifs of crystalline rocks are confined to the ancient faults; these depressions are associated with marshy lowlands, lake basins, and river valleys. Relief of ice and water-ice accumulations also widely occur in the Reserve area, mainly located within the valley of Kamennaya River which is a large ancient valley system of melted glacier water flows and water-ice accumulation. The hydrological network of the Reserve includes a lot of lakes, rivers, streams, and wetlands. The Reserve is located within the Atlantic-Arctic climatic region of the temperate zone (Alisov 1969). Winters are relatively mild; summers are short and cool. The frost-free period varies from 90 to 120 days, the average annual temperature is 0.5°C, and average annual precipitation is about 600 mm (Bychkova 1965, 1968). The forest vegetation is dominated by Pinus sylvestris forests (69.6% of the forested area). Picea abies forests are much less common (10.3% of the forested area); they mainly occur in the valleys of rivers and streams and at the base of slopes. Forests dominated by Betula spp. occupy less than 10% of the forested area. The average site class is 4 or 5; the average stand density is 0.5–0.6 (Belousova et al. 1988). Studies on post-fire successions were carried out in 1992–1993 at permanent plots located near Lake Kalivo within the denudation-tectonic landscape and on lowland outwash terrains near the Kamennaya River within the water-glacial landscape (Fig. 3.6). Eighty individuals of Pinus sylvestris with fire scars, growing at the permanent plots, were used for dating fires that had occurred during the past 400  years. Schemes of fire distribution and frequency were composed for these plots. The vegetation was described according to the Braun-Blanquet method based on 96 square plots of 100 m2 located within the permanent plots. The ontogenetic structure of tree populations was studied in permanent plots located near the Kamennaya River: 20 sample plots of the size from 0.25 to 1 ha were situated on fire sites of different ages.

3.3.2  P  ost-Fire Vegetation Within the Denudation-Tectonic Landscape Forest vegetation within the denudation-tectonic landscape was studied in the permanent plot of 18 ha located near Lake Kalivo (Fig. 3.6). The plot is situated at the most elevated part of the Nature Reserve (Fig. 3.7). There is a large tectonic fault indicated by a chain of lakes connected by rapid streams. The fault divides the area into the ridges with elevations of 240–260 m and bogs in inter-ridge depressions

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Fig. 3.6  Schematic map of the Kostomuksha Nature Reserve and locations of vegetation sample plot areas. 1 lakes, 2 border between Finland and Russia, 3 border of the Reserve, 4 approximate location of four permanent sample plots (of 15, 12, 11.25 and 0.25  ha, respectively) near the Kamennaya River, 5 location of permanent sample plot (18 ha) near Lake Kalivo

(Fig.  3.8). The following differences in landscape within the denudation-tectonic terrains in the Reserve were distinguished (Rusanova 1989): (1) tops and upper slopes of ridges composed of crystalline rocks and covered with a thin sandy moraine; (2) medium parts of the stepped slopes of the ridges with boulders covered with a sandy moraine from 10 to 50 cm; (3) low parts of the slopes, esker ridges composed of coarse-grained glacial deposits; (4) inter-ridge depressions with temporary or permanent streams (so-called logs); and (5) flat or concave inter-ridge depressions with stagnant moisture (bogs). Results of the investigations (Kuleshova et  al. 1996; Korotkov et  al. 1999) showed that the study area includes forest communities with signs of multiple fire disturbances from the seventeenth to twentieth centuries. Within the permanent plot, 8.4, 4.2, and 5.4 ha were burnt by the fires of 1924, 1816, and 1787 years, respectively (Fig. 3.8). These years mark the time of the last fire for each particular site, but several more fires at different, earlier times were recorded at each site. Tops and upper parts of slopes have the highest frequency of fires. Besides the fires of 1924, 1816, and 1787, it was found that there were also fires in 1738, 1694,

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Fig. 3.7 Post-fire Pinus sylvestris forest with an admixture of Picea abies, dominated by dwarf shrubs in the ground layer and located on upper slopes of ridges in the Kostomuksha Reserve (Photo by B. Raevsky)

Fig. 3.8  Scheme of the denudation-tectonic landscape profile in the Kostomuksha Nature Reserve near Lake Kalivo together with the spatial pattern of fires of different years within the permanent sample plot. 1–3 forest sections along the profile: 1 green moss – lichen forests, 2 dwarf shrub – green moss forests, 3 swamp tall herb forests and dwarf shrub – sphagnum forests, 4 Pinus sylvestris, 5 Picea abies. H height above sea level, in m. AB the permanent sample plot

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1667, and 1646. The high frequency of fires led to the forming of pine forests with an age structure that reflects pine regeneration after each of the fires. These forests are classified as the subass. C.a.–P.b. vaccinietosum myrtilli Morozova et V. Korotkov 1999 of the ass. Cladonio arbusculae–Pinetum boreale (Caj. 1921) K.-Lund 1967 according to the Braun-Blanquet approach or as the Pineta sylvestris hylocomioso-cladinosa (lichen  – green moss pine forests) according to the Prodromus of the boreal vegetation described in Sect. 3.1. In 1992 (when this was investigated), Pinus sylvestris trees of 140–176 years old, grown after the fire of 1816, dominated in the overstorey. Fire scars received during a ground fire in 1924 were found on the trunks of the pines. Pinus sylvestris of 380–400 years old with multiple fire scars also occurred in the plot; these old trees testified seven large fires since the beginning of the seventeenth century. An admixture of Betula pendula always occurred in the stand. Pinus sylvestris, Picea abies, and Populus tremula occurred in the undergrowth with small abundance but high-­ frequency values. B. pubescens and Salix caprea also occurred in the undergrowth. Single sprouts of Sorbus gorodkovii and Juniperus communis were found in the shrub layer. Vaccinium vitis-idaea and Calluna vulgaris dominated in the sparse field layer. Vaccinium myrtillus and Empetrum nigrum occurred as an admixture with small abundance. Among the vascular species, boreal species prevailed, but piny and meadow-edge species were also present (Fig. 3.9). Green mosses such as Pleurozium schreberi and Dicranum spp. and lichens of the genus Cladonia dominated in the bottom layer and had an uneven spatial distribution: green mosses prevailed under the serried groups of pine trees and lichens prevailed on glades. Cover and the average species number per 100 m2 (species density) were higher for lichens than for vascular plants. The middle parts of slopes within the permanent plot were burnt in 1737, 1787, and 1816 (Korotkov et al. 1999). This habitat carries Pinus sylvestris forest dominated by green mosses in the ground layer. This forest community belongs to the ass. Vaccinio vitis-idaeae–Pinetum Caj. 1921 according to the Braun-Blanquet approach or to the Pineta fruticuloso-hylocomiosa according to the Prodromus (Sect. 3.1) (Fig. 3.10). The share of Picea abies in the undergrowth was significantly higher than on the upper parts of slopes: its cover ranged from 10 to 40%. Vaccinium myrtillus and V. vitis-idaea dominated in the field layer and the proportion of Calluna vulgaris was much smaller than on the upper part. Cover of herbaceous species such as Lycopodium annotinum, Carex globularis, Orthilia secunda, etc. remained low, but average species density slightly increased (till 15 species per 100  m2) at the expense of the boreal herbs (Fig.  3.9). Pleurozium schreberi, Hylocomium splendens, and Dicranum spp. dominated in the bottom layer. The cover of lichens was significantly lower in comparison with the previous plant community. According to the analysis of fire scars on old pines, the lower parts of slopes, esker ridges, and inter-ridge depressions were burnt last in 1787 (Korotkov et al. 1999). These habitats possess a good or excessive moisture content and are very rarely damaged by fires. The lower parts of slopes (esker ridges) were covered by closed spruce forests dominated by dwarf shrubs and green mosses in the ground

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Fig. 3.9  Ecological-coenotic structure of the field layer and species richness in forests located at different positions within the denudation-tectonic landscape (the permanent plot near Lake Kalivo): 1 flat tops and upper parts of slopes, 2 middle parts of slopes, 3 lower parts of slopes, 4 inter-ridge depressions with temporary or permanent streams, 5 inter-ridge depressions with stagnant moisture. Ecological-coenotic groups: Br boreal, Pn piny, Nm nemoral, Nt nitrophilous, Wt water-marsh, Olg oligotrophic, and Md meadow-edge groups (see Sect. 2.2)

layer and correspond to the forest-type Piceeta fruticuloso-hylocomiosa according to the Prodromus of the boreal forests (Sect. 3.1) or to the ass. Linnaeo borealis– Piceetum abietis (Caj. 1921) K.-Lund 1962 according to the Braun-Blanquet approach (Fig. 3.11). Besides Picea abies, there were Pinus sylvestris, Betula pendula, B. pubescens, and rarely Populus tremula in the overstorey. Pinus sylvestris was represented only by old trees of 300–390 years old which had overgrown fire scars received during the fire in 1787. Picea abies dominated in the overstorey as well as in the understorey. Shrubs such as Sorbus gorodkovii and Juniperus communis often occurred. Vaccinium myrtillus and V. vitis-idaea dominated in the field layer with an admixture of Linnaea borealis. Cover of herbaceous species reached

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Fig. 3.10 Association Vaccinio vitis-idaeae—Pinetum in the Kostomuksha Reserve (Photo by V. Korotkov)

Fig. 3.11 Association Linnaeo borealis—Piceetum abietis in the Kostomuksha Reserve (Photo by V. Korotkov)

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30%; boreal small herbs and ferns, such as Maianthemum bifolium, Trientalis europaea, Gymnocarpium dryopteris, etc., were common. The average species richness of vascular plants (25 species per 100 m2) was highest of all landscape types except for the depressions. Green mosses such as Pleurozium schreberi, Hylocomium splendens, and Ptilium crista-castrensis totally dominated the bottom layer. Generally, as vascular plant species diversity increases, the proportion of boreal species also increases and that of the piny and meadow species decreases from the upper to the low parts of the slopes (Fig.  3.9). However, the ecological-coenotic structure of the plant communities does not differ significantly in these three habitats and that means that there is no principal difference in the ecological conditions for plants along the slopes. Our results show that fire frequency is the most important factor influencing patterns of plant distribution (Kuleshova et al. 1996; Korotkov et al. 1999). And with prolonged absence of fires, a spruce (Picea abies) forest can be developed in all habitats discussed. Inter-ridge depressions with flowing and stagnant moisture were least damaged by fires. Logs with temporary or permanent streams were covered by swamp tall herb spruce forests belonging to the fores type Piceeta uliginoso-magnoherbosa according to the Prodromus of the boreal forests (Sect. 3.1) or to the ass. Pseudobryo cinclidioidis–Piceetum abietis Kutenkov ex Zaugolnova nov. prov. (Zaugolnova and Martynenko 2014) according to the Braun-Blanquet approach. These forests were characterized by the highest floristic diversity within the permanent sample plot: 30 vascular plants per 100 m2. Rubus chamaemorus, Gymnocarpium dryopteris, Calamagrostis canescens, Equisetum sylvaticum, and Carex spp. dominated in the field layer; Chamaepericlymenum suecicum and Dactylorhiza maculata were also found there. Of the vascular plants, besides boreal species, water-marsh species prevailed (Fig. 3.9). Sphagnum girgensohni and S. magellanicum dominated in the moss cover; Hylocomium splendens and Polytrichum commune were co-dominants. The total cover of the bottom layer varied from 60 to 90%. Pine forests dominated by sphagnum mosses and dwarf shrubs in the ground layer (Pineta sylvestris fruticuloso-sphagnosa) grew in the inter-ridge depressions with stagnant moisture. These forests belong to the ass. Oxycocco quadripetali– Pinetum K.-Lund 1981. Pinus sylvestris L. var. nana Pall. grew in the overstorey as well as in the understorey. The dwarf shrubs Betula nana and Andromeda polifolia dominated in the field layer. Carex pauciflora, Eriophorum vaginatum, Eleocharis palustris, Drosera rotundifolia, etc. also occurred there. There were 21 vascular plants per 100  m2 on average; oligotrophic species prevailed. Mosses covered 80–90% of the bottom layer; Polytrichum commune, Sphagnum magellanicum, S. girgensohnii, and S. capillifolium dominated. Analysis of the vegetation along the denudation-tectonic landscape profile showed that the degree of moistening and drainage conditions are the main natural factors differentiating the forest vegetation into the following three groups: vegetation of the (i) tops and slopes of the ridges, (ii) inter-ridge depressions with flowing moisture, and (iii) inter-ridge depressions with stagnant moisture. The forest vegetation that covered the ridges was formed under the influence of fire disturbances which were strongest on tops and upper parts of the slopes. The frequency of the

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fires varied from two to three times per 100 years on upper parts of the slopes to one time per 200–300 years in the inter-ridge depressions. The increase in fire frequency led to the transformation of Picea abies forests into monodominant Pinus sylvestris forests with a very poor herbaceous layer and an increased cover of dwarf shrubs, mosses, and lichens (Kuleshova et al. 1996; Korotkov et al. 1999). The population densities and species diversities of birds and soil invertebrates also decreased in the post-fire pine forests (Potapova 1989; Kuleshova et al. 1996).

3.3.3  Succession After Fire in the Lowland Outwash Terrains Successions in forest communities damaged by fires at different times and in different frequencies were studied at the four permanent sample plots located within the water-glacial landscape on lowland outwash terrains at a distance of 100–900  m from the Kamennaya River (Fig. 3.6). The ontogenetic structures of tree populations were studied at 20 temporal plots, each of them situated within a fire site of a certain age. The initial stage of succession after fire was investigated in permanent plot No. 1 where the latest fire was a crown fire in 1968 that caused fire scars on the bases of the pines (Fig. 3.12). Full 25 years after the fire (in 1993, the year of the investigation), the vegetation was a very sparse Pinus sylvestris forest dominated by lichens and Calluna vulgaris in the ground layer (Fig. 3.13). The plant community belongs to the subass. C.a.–P.b. typicum Morozova et V. Korotkov 1999 of the ass. Cladonio arbusculae–Pinetum boreale (Caj. 1921) K.-Lund 1967 according to the Braun-­ Blanquet approach or to the Pineta sylvestris cladinosa (genuine lichen pine forests) according to the Prodromus described in Sect. 3.1. Fragments of the lichen-heather barrens without trees in the overstorey and with only small individuals of Pinus sylvestris in the understorey were also found there. The stand contained a small number of old but healthy and generatively reproducing pine trees that had recovered after the fire. The trunk diameters of these old pines varied from 12 to 48 cm; their density was 30–40 trees/ha. The oldest trees were 350–390 years old. Traces of six or seven fires that had occurred in the stand since the beginning of the seventeenth century were clearly visible on the old trees. Weak, very weak, and dying old-growth trees with trunk diameters of 32 to 48 cm also occurred in the plot. There were also some dead pine trees as snags or fallen logs with a medium to large diameter (from 16 to 40 cm); they had died in the fire of 1968. Pine trees with trunk diameters of less than 8–16  cm were completely absent; they had been burnt by the fire. Pinus sylvestris vigorously regenerated in the plot after the 1968 fire: the pine undergrowth consisted of 50,000 individuals per hectare (Fig. 3.14). The regeneration of Picea abies, Betula pubescens, and Populus tremula was weak: the ­undergrowth contained 50–150 ind./ha of these species. Calluna vulgaris dominated in the field layer with a small admixture of Vaccinium vitis-idaea. In separate patches V. myrtillus, Empetrum hermaphroditum, and Arctostaphylos uva-ursi sel-

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Fig. 3.12  Pinus sylvestris with multiple fire scars at the site where fire occurred in 1968 in the Kostomuksha Reserve (The photo was taken in 1993 by V. Korotkov)

dom occurred. Herbaceous species were represented by a few individuals of Solidago virgaurea, Antennaria dioica, Chamaenerion angustifolium, Diphasiastrum complanatum, and Avenella flexuosa. As a result of the presence of piny and meadow-­edge species, the average number of vascular plants per 100 m2 was relatively high (Fig.  3.15). High cover and species diversity values (6–8 species per 100  m2) were also observed for lichens. Cladonia phyllophora, C. deformis, C. pleurota, and C. rangiferina were the most common (Korotkov et al. 1999). Mosses (Polytrichum juniperinum, P. piliferum, Pleurozium schreberi, and Dicranum scoparium) also occurred in the bottom layer but with a much lower abundance than lichens. Thus, during the first stage of succession after fire in the often-burned Pinus sylvestris forests on poor sands, species which do not demand a good soil fertility dominated: Pinus sylvestris in the overstorey, Calluna vulgaris in the field layer, and Cladonia ssp. in the bottom layer. The decay of such a pine stand damaged by fire continues for a long time; in the plot an average 40–50 trees per hectare became uprooted (Korotkov et al. 1999). This number is not high, but it leads to the formation of a mosaic of microsites consisting of fallen logs, pits, and mounds where

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Fig. 3.13 Sparse Pinus sylvestris forest dominated by lichens and Calluna vulgaris in the ground layer of the vegetation after the fire of 1968 (The photo was taken in 1993 by V. Korotkov)

species of different ecological properties can grow. In our investigations, 60% of all pits, 29% of all mounds, and 36% of all treefalls without the microrelief disturbances contained pine seedlings. Birch and spruce seedlings appeared only in the pits. Dwarf shrubs with relatively high needs of water supply, such as Vaccinium myrtillus and Empetrum hermaphroditum, grew in wet pits. Species which are not demanding water, such as Arctostaphylos uva-ursi, Calluna vulgaris, and V. vitis-­ idaea, vigorously grew on drier mounds. The second stage of succession after fire was also investigated in permanent plot No. 1 at sites where the last crown fire had occurred in 1920 as evidenced by fire scars on Pinus sylvestris individuals (Korotkov et al. 1999). In the 73 years since the last fire, a green moss – lichen pine forest (Pineta sylvestris hylocomioso-cladinosa according to the Prodromus in Sect. 3.1) had developed belonging to the subass. C.a.–P.b. vaccinietosum myrtilli Morozova et V. Korotkov 1999. The main difference with the previous succession stage lays in the ontogenetic structures of the tree populations. This second stage showed uneven-aged pine forests whose ontogenetic structure was not quite balanced (Fig. 3.14). Virginal and young reproductive individuals of Pinus sylvestris which had established after the fire of 1920 dominated, their number being 6400 ind./ha. Picea abies, Betula pubescens, and B. pendula were admixed. Mature and old reproductive pines that had stayed alive after the fire of 1920 had declined and gradually died. The rather dense undergrowth reduced the light availability in the lower layers of the plant community and that caused the following changes in the ground layer

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Fig. 3.14  Ontogenetic structures of tree species populations in the post-fire communities on lowland outwash terrains near the Kamennaya River. Numbers of stems per hectare are presented on a logarithmic scale

compared with the plant community in the first stage of succession after the fire. Of the dwarf shrubs, the proportion of Vaccinium vitis-idaea, Empetrum hermaphroditum, and V. myrtillus increased and that of Calluna vulgaris noticeably decreased; V. myrtillus and Empetrum hermaphroditum grew not only in depressions and pits but also on lying and decaying tree logs and on mounds formed after treefalls with uprooting. Herbaceous species had almost dropped out of the plant community, and species diversity was strongly reduced (Fig. 3.15). Mosses and lichens had slightly decreased in the bottom layer. The third stage of succession after fire was investigated in permanent plot No. 2 where the last crown fire occurred in 1858 as shown by fire scars on the bases of

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Fig. 3.15  Ecological-coenotic structure of the field layer and species richness in the post-fire communities on lowland outwash terrains near the Kamennaya River. 1 Pineta sylvestris cladinosa, with the last fire in 1968; 2 Pineta sylvestris hylocomioso-cladinosa, with the last fire in 1920; 3 Pineta sylvestris hylocomioso-cladinosa, with the last fire in 1858; 4 Piceeta fruticuloso-­ hylocomiosa, with the last fire in 1822; 5 Piceeta parviherboso-hylocomiosa, with the last fire in 1773. Ecological-coenotic groups: Br boreal, Pn piny, Nm nemoral, Olg oligotrophic, and Md meadow-edge group

pines. The plant community in that plot also belonged to the subass. C.a.–P.b. vaccinietosum myrtilli Morozova et V. Korotkov 1999 according to the Braun-Blanquet approach (Fig.  3.16) or to the Pineta sylvestris hylocomioso-cladinosa (green moss – lichen pine forests) according to the Prodromus described in Sect. 3.1. One hundred thirty five years after the fire, young and mature reproductive individuals of Pinus sylvestris with diameters of 16–24 cm and ages of 130–135 years dominated in the sparse overstorey, numbering 1300 ind./ha (Fig. 3.14). There also was a pine undergrowth, numbering 250 ind./ha. Mapping of this community

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Fig. 3.16 Subassociation Cladonio–Pinetum vaccinietosum myrtilli in the Kostomuksha Reserve (Photo by I. Georgievsky)

showed a spatial aggregation of pines of different age groups (Fig. 3.17a, c) that usually is caused by repeated ground fires (Korchagin 1954; Vakurov 1975; Sannikov 1983; Gorshkov 1998). The almost total absence of spruce in the overstorey and in the understorey was probably caused by the repeated fires in the area and the remoteness of the locality from the river where reproductive Picea abies individuals grow. We found that there were four large fires during the eighteenth century and three fires during the nineteenth century (Kuleshova et al. 1996). The density of Picea abies seedlings in additional sample plots was closely correlated with the distance from the reproductive spruce trees located in the river valley: 4100 individuals of Picea abies seedling per hectare at a distance of 20 meters from the log valley spruce forest and 2500, 1500, 700, and 300 ind./ha at distances of 60, 100, 150, and 200 m, respectively (Korotkov et al. 1999). The composition of the ground layer was generally the same as that in the previous succession stage, but the cover of mosses was higher than the cover of lichens. There were about 12 vascular species per 100 m2 on average (Fig. 3.15). The dwarf shrubs Vaccinium vitis-idaea, V. myrtillus, and Empetrum hermaphroditum together with green mosses dominated at sites with a concentration of trees; the lichens Cladonia rangiferina, C. arbuscula, C. stellaris, C. uncialis, etc. dominated in forest gaps. The absence of rejuvenation of Picea abies and the presence of spatially aggregated age groups of Pinus sylvestris testify that there were some obstacles in the successional recovery of the vegetation. These obstacles may be periodic fires over

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Fig. 3.17  Spatial structure of the post-fire forest communities on lowland outwash terrains near the Kamennaya River. (a, b) Vertical profiles; (c, d) horizontal projections. (a, c) green moss – lichen pine forests formed after the fire of 1858; (b, d) boreal small herb – green moss spruce forests formed after the fire of 1773. (a) 1 undergrowth of Pinus sylvestris, 2 undergrowth of Picea abies; (b) 1 Picea abies, 2 Populus tremula, 3 Betula pubescens; (c) 1 positions of the bases of Pinus sylvestris trunks scaled according to their diameters, 2 Pinus sylvestris seedlings. (d) 1, 2, 3, and 4 positions of the bases of Picea abies, Betula spp., Populus tremula, and Salix caprea trunks, respectively, scaled according to their diameters. Lying logs and projections of pits and mounds formed after treefalls with uprooting are shown by lines

large areas including ground fires which cannot be clearly registered by fire scars. However, the general direction of the succession was also confirmed by the increase of the thickness of the litter layer (soil horizon A0); this was measured as 0.3–0.8 cm, 1.0–1.8 cm, and 4.5–5.0 cm at the forests formed after the fires of 1968, 1920, and 1858, respectively (Kuleshova et al. 1996). The fourth stage of succession after fire was observed in permanent plot No. 3 where the last crown fire was in 1822. Sites with such old fires were found only in near river and stream valleys. One hundred seventy years after the fire, there was a

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middle-aged Picea abies forest classified as the ass. Linnaeo borealis–Piceetum abietis (Caj. 1921) K.-Lund 1962 according to the Braun-Blanquet approach or to the Piceeta fruticuloso-hylocomiosa (green moss  – dwarf shrub spruce forests) according to the Prodromus described in Sect. 3.1. Betula spp. co-dominated with Picea abies in the overstorey; only old Pinus sylvestris individuals occurred in the stand (Fig. 3.14). Renewal of Pinus sylvestris was completely absent due to the competition for light with other species. The total number of reproductive individuals of Picea abies was 500 ind./ha; Picea abies undergrowth numbered 550 ind./ha while the undergrowth of Betula pubescens consisted of 600 ind./ha. The shrub layer consisted of Sorbus gorodkovii and Juniperus communis. The herbaceous species Chamaenerion angustifolium, Goodyera repens, Lerchenfeldia flexuosa, Luzula pilosa, Lycopodium annotinum, Maianthemum bifolium, Melampyrum pratense, Solidago virgaurea, and Orthilia secunda grew in the ground layer. Species diversity of vascular plants was, at 19 vascular species per 100 m2 on average, higher than in the all previous post-fire succession stages; boreal species prevailed (Fig. 3.15). The mosses Pleurozium schreberi, Hylocomium splendens, and Dicranum spp. dominated. Sphagnum mosses also appeared in the bottom layer. The fifth and last stage of succession after fire described in the Reserve was observed on lowland outwash terrains near the Kamennaya River in permanent plot No. 4 where the last crown fire had occurred in 1773. The plant community belonged to the ass. Linnaeo borealis–Piceetum abietis (Caj. 1921) K.-Lund 1962 according to the Braun-Blanquet approach or to the Piceeta parviherboso-hylocomiosa (boreal small herb  – green moss spruce forests) according to the Prodromus (Sect. 3.1). In the overstorey, Picea abies dominated with a number of 600 ind./ha; a small admixture of Betula pubescens, Populus tremula, and Salix caprea was also present (Fig.  3.14). Only old individuals of Pinus sylvestris occurred here, whereas the Picea abies population had the normal type of ontogenetic structure: individuals of all ontogenetic stages were present with a total number of 2000 ind./ha (Fig. 3.14). Sustainable regeneration of Picea abies became possible because of the long absence of fires together with the availability of decaying logs which are suitable sites for the successful establishment of Picea spp. seedlings (Obnovlensky 1935; Kazimirov 1971; Yaroshenko 1999). On average there were more than 50 treefalls with uprooting per 100 m2 (Fig. 3.17). On the whole, the pit-and-mound topography formed by the fall of large trees with uprooting, pits, mounds, and logs of different sizes and varying degrees of wood decomposition and soil erosion formed the conditions that allowed the development of the highest diversity of the community in this stage of succession. We registered 24 vascular plants per 100  m2 on average, mainly boreal species (Fig. 3.15). Plants with relatively high demands on soil fertility had appeared in the community. The mesotrophic tree species Populus tremula and Salix caprea occurred (Fig. 3.14). In the field layer, boreal herbs and ferns, such as Listera cordata, Goodyera repens, Gymnocarpium dryopteris, Luzula pilosa, Oxalis aceto-

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sella, Lycopodium annotinum, etc., were found, while dwarf shrubs had decreased in abundance. Sphagnum species occurred, mainly in wet depressions formed after treefalls. Frequencies of Hylocomium splendens and Polytrichum commune had increased. “New species” such as Aulacomnium palustre, Barbilophozia barbata, Brachythecium reflexum, Calypogeia neesiana, Dicranum congestum, and others appeared in the bottom layer. The cover of lichens had drastically reduced. Surviving lichens were located on decaying wood of fallen trees.

3.3.4  Conclusion The dating of fires based on fire scars on Pinus sylvestris showed that repeated fires had occurred throughout the Kostomuksha Nature Reserve at least since the early seventeenth century. As a result, the current forest cover in the Reserve is a mosaic of successional forest communities at different stages of post-fire recovery. Our investigations confirm that fires maintain Pinus sylvestris forests and also species associated with light coniferous forests (Melekhov 1966; Sannikov 1983; Gromtsev 1993; Kuleshova et al. 1996; Goldammer and Furyaev 1996; Stavrova et al. 2016, etc.). Fires determined the absolute predominance of Pinus sylvestris forests in the Reserve, in the surrounding areas, and in most parts of Karelia. Our research showed that Pinus sylvestris forests can change into Picea abies forests when there were no fires for 200  years or more and when Picea abies seeds are available. Then the ground layer is also changing, from the genuine lichen through the green moss – lichen and from the green moss – dwarf shrub to the boreal small herb – green moss subsections, but all these changes occur during the lifetime of Pinus sylvestris. In the Kostomuksha Nature Reserve, we did not observe the next successional stages that have been identified for the boreal forest in the form of the subsequent changes in Picea abies forests with a corresponding development of the ground layer. This was due to the absence of sites in the Reserve which had not burned for more than 250 years. Delay and regression in the development of these forest ecosystems are possible at each successional stage. In the Kostomuksha Nature Reserve, factors constraining the successional development are repeated crown and ground fires.

3.4  O  ld-Growth Dark Coniferous Forests in the Pechora-­ Ilych Nature Reserve The study of forest history and historical land use in the boreal region of European Russia (see Sect. 3.2) showed that there are very few locations where forest tracts have long existed without human impacts. One of the largest intact landscapes in Europe is located in the Northern Urals. There we find the UNESCO World Heritage Site Virgin Komi Forests consisting of the Pechora-Ilych State Nature Reserve and the National Park “Yugyd Va.”

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3.4.1  G  eneral Description of the Pechora-Ilych State Nature Reserve The Pechora-Ilych Reserve is situated on the western slopes of the Ural Mountains and the adjacent foothills and lowlands (Fig. 3.18). The area is drained by the upper course of the Pechora River and its tributary, the Ilych River. The Reserve consists of two separated sections of different size. A small section (with an area of 158 km2) is located on a plain, on the right bank of the Pechora River in the southwest of the Pechora-Ilych watershed. A large section (with an area of 7055 km2) is located in the eastern, mountainous part of the Pechora-Ilych watershed (number 12 in Fig. 2.1). The forests in the Reserve cover an area of 6246  km2. Forests dominated by Picea obovata, Abies sibirica, and Pinus sibirica occupy 82% of the forested lands; they are mainly located in the mountainous part of the Reserve (Fig. 3.19). Pinus sylvestris forests occupy 5% of the wooded area, and they are mainly located in the plain part of the Reserve. Forests dominated by Betula pubescens (11%) and Populus tremula (1%) are scattered throughout the Reserve and occupy places where fires occurred less than 100 years ago. The smallest proportion of the forested lands (less than 1%) is occupied by Larix sibirica, Salix spp., and Padus avium forests; they are located along the banks of the Pechora River. Analysis of historical records showed that the area located north of the upper course of the Pechora River remained uninhabited until the beginning of the nineteenth century. The first settlements in the upper Pechora River appeared in the

Fig. 3.18  Forests in the Pechora-Ilych State Nature Reserve. View on the Pechora River, the Medvezhiy Kamen Mountain (right) and the Yanypupuner Ridge (left) (Photo by A. Aleynikov)

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Fig. 3.19  Map of the mountainous part of the Pechora-Ilych State Nature Reserve with the location of the Bolshaya Porozhnaya River basin (the study area in the Reserve) and settlements that appeared in the nineteenth and twentieth centuries (1 and 2, respectively) on the banks of the Pechora and Ilych rivers

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1860s; by 1889 there were three settlements with a population of 33 people (a population density of 0.025 people/km2) (Belditskiy 1901; Onchukov 1901). By the end of the nineteenth century, the total area of arable lands within the Pechora River basin that is included into the present Reserve area was only 25 ha, and the area of hayfields was 257 ha (Sbornik… 1889). Only the best individuals of Pinus sibirica and Picea obovata were cut along the Pechora River and its large floatable tributaries. After the reservation was established in 1930, all settlements were abandoned, and economic activities were nearly all stopped. However, hayfields have been maintained and fires have occurred in the region till the present time (Fig. 3.20). Thus, during the last several centuries, anthropogenic impacts did occur in the mountainous part of the present Reserve area, but they were relatively weak. The basin of the right tributary of the Pechora River, the Bolshaya Porozhnaya River basin (Fig. 3.19), remained one of the least disturbed (Fig. 3.20), and therefore it was selected as the study area to investigate old-growth dark coniferous forests and to identify natural and anthropogenic factors determining the composition and structure of the boreal forest ecosystems.

3.4.2  The Study Area (Bolshaya Porozhnaya River Basin) The Bolshaya Porozhnaya River flows from north to south. The geographical coordinates of the study area are 62°N and 58.6°E; the total basin area measures approximately 250 km2 (Figs. 3.19 and 3.21). The western bank of the Bolshaya Porozhnaya River is slightly sloping and formed by moraine loams with inclusions of crystalline schist; the vertical drop is about 25  m/km. The eastern bank is steeper and also formed by moraine loams, water-glacial sandy loams and debris of crystalline rocks (Varsanofyeva 1932); the vertical drop is about 100 m/km. The elevation within the study area varies from 256 to 603 m asl. The climate is temperate continental and is under the influence of western air masses with frequent invasions of cold Arctic air along the ridges (Atlas… 1997). The average annual temperature is minus 0.4°C. The frost-free period is 80–110 days; the vegetation period is 140–150 days; the average January temperature is −15.0 to −17.5°С; the average July temperature is + 15.5–16.5°С. The average annual precipitation is 800 mm. Snow cover is established in late October – early November and lasts about 180–190 days. Old-growth and uneven-aged dark coniferous forests dominated by Picea obovata, Abies sibirica, and Pinus sibirica occupy practically all basin areas except for small patches of bogs and meadows in the floodplain of the Bolshaya Porozhnaya River (Fig. 3.21). Results of radiocarbon dating of the coal found in the soil allowed us to suggest that the last large fires in the study area occurred 500–1000 years ago. There are also data on local fires in the range of 100 to 500 years ago, but these were located mainly along the Pechora River; this matter requires further examination in the study area.

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Fig. 3.20  Maps of the mountainous part of the Pechora-Ilych State Nature Reserve with the locations of historical fires: (a) from 1850 to 1899, (b) from 1900 to 1929, (c) from 1930 to 1951, and (d) from 1959 to 2014. 1 the watershed between the Pechora and Ilych rivers; 2 areas of fires (From Aleynikov et al. (2015) with modifications)

3.4.3  Methods of Investigation Integrated investigations of forest ecosystems have been carried out there since 2005. So far, these investigations include studies of trees and their natural regeneration, the spatial structure of the forests, their ground vegetation, their coarse woody debris and decay fungi, and their soils and soil mesofauna.

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Fig. 3.21  Map of the study area in the lower reaches of the Bolshaya Porozhnaya River: 1 boreal tall herb Picea obovata and Abies sibirica forests, 2 large fern Picea obovata and Abies sibirica forests, 3 green moss Picea obovata and Abies sibirica forests, 4 boreal swamp Picea obovata forests, 5 sphagnum Picea obovata forests, 6 bogs, 7 meadows, 8 rocky mountains, 9 boundary of the Bolshaya Porozhnaya River basin, 10 sample plots at the studied profiles

A regular network of vegetation and soil sample plots was established in the lower reaches of the Bolshaya Porozhnaya River. It consisted of eight profiles of a length of 2.5 km each running from the watershed ridge to the river channel on the right bank of the river and seven similar profiles of 5.5 km each on the left bank of the river (Fig. 3.21). Vegetation was sampled in 2008–2012 according to the method described in Sect. 2.4 in 651 square plots of 100 m2 which were located 100 m apart along the profiles. Soils were described from small soil pits located near the vegetation plots. Vegetation was also sampled in an additional 128 square plots of 100 m2 located out of the regular network of plots to describe boreal swamp forests growing along the streams and tributaries of the Bolshaya Porozhnaya River. The vegetation sample plots were classified into the five forest types based on methods described in Sect. 2.5; plant species richness, species density, and structural diversity of the field layer were calculated for each forest type according to the described techniques. More than 100 vegetation plots were extra sampled to clarify the boundaries of the forest types in the map (Fig. 3.21) which was made based on remotely sensed satellite data of high (Iconos, 2.01 m per pixel) and medium (Landsat, 30 m per pixel) spatial resolution.

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Tree species populations were studied in different forest types in nine tree sample plots ranging in size from 2500 m2 (square plots 50 × 50 m) to 10,000 m2 (50 × 200 m). Within the plots, for each tree with a DBH of more than 2 cm, the following parameters were registered: species, ontogenetic stage according to the method described in Sect. 2.5, absolute age according to its tree core, presence/ absence of stem rot, tree diameter at breast height (DBH), tree height, and crown diameter. More than 800 trees were examined. Electronic and laser measuring devices linked to a GIS (Field-Map®, Monitoring and Mapping Solutions, Ltd.) were used to map the plots and the trees in the study area and to map and measure tree crown projections. Microsite structure and biomass of the ground layer were measured and analyzed for the described forests. We have developed a special typology of microsites to analyze the structure of the ground layer in the old-growth forests (Smirnova et al. 2010, 2011; Lugovaya et al. 2013). The typology was based on the idea that trees are the main agents in establishing and modifying the forest structure (Braun-­Blanquet and Pavillard 1925; Sukachev 1928; Smirnova 1998; Smirnova and Bobrovsky 2001; Smirnova and Toropova 2008). Therefore microsites important for the ecosystem dynamics and functioning of the forest have to be linked with the life and death of tree species. We distinguish 13 types of microsites in old-growth, uneven-aged forests (Smirnova et al. 2010, 2011; Lugovaya et  al. 2013). Ten types are related to the pit-and-mound topography caused by treefalls with uprootings: they are fallen logs, pits, and mounds at different stages of decay and erosion (see below). Another two types of microsites are formed by living large trees: one type is “the area under the tree’s crown” or “below-treecrown area” which has specific environmental properties resulting from shading, redistribution of precipitation, and the prevalence of wood litter over the herbaceous plant growth (Smirnova and Bobrovsky 2001), and the other is “the elevation close to a tree’s trunk.” This is formed when the basal part of the trunk and anchor roots protrudes from the surface of the soil and creates a specific microsite. Some vascular plants, mosses, and lichens use the strongly cracked bark to grow on; together they form a ring or collar at the bottom of such a tree trunk. The 13th type of microsite we distinguished was “the inter-crown area,” consisting of patches outside the tree crown projections and without visible signs of pit-andmound topography. The ten types of microsites related to the pit-and-mound topography are the following: three stages of decay and erosion of the mounds, three stages of overgrowing of the pits, and four stages of overgrowing of fallen logs. For mounds and pits, the stages are defined by the condition of the mounds (Basevich 1981; Skvortsova et al. 1983). The first stage of decay and erosion of a mound (and thus also for the associated pit) lasts from the time of treefall with uprooting till the end of the abscission of soil from the roots of the fallen tree. The second stage lasts till the destruction of the root system: the mound is clearly visible and root residues are mainly located inside the soil clod. In the third stage, there is final humification and mineralization of roots and the mound looks as a locally smoothed heaving of the ground (Fig. 3.22).

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Fig. 3.22  Three stages of decay and erosion of pits and mounds formed after treefalls with uprooting (From Shirokov (1998) with modifications)

The four stages of overgrowing of the fallen logs are indicated by plants growing there (Zaprudina and Smirnov 2010; Zaprudina 2012; Lugovaya et al. 2013). The first stage is finished when a continuous cover of mosses has been formed. The second stage is observed when boreal dwarf shrubs and boreal small herbs co-dominate with the green mosses. The third and fourth stages are distinguished in forests, where midsize and large herbs and ferns occur: at the third stage, these species begin to grow on the fallen logs and in the fourth stage they dominate. Obviously trees also can fall without uprooting. This can result from stem and root rot (e.g., Aleynikov and Bovkunov 2011), and only a broken stump and fallen logs remain in that case. Then there are no microsites related to pits and mounds, and only different stages of overgrowing of fallen logs can be distinguished. The microsite structure has been studied in each forest type in sample plots from 0.25 ha to 1 ha (Zaprudina 2012; Lugovaya et al. 2013). The area of each microsite was measured, and the average total area of the types of microsites was calculated for the forest types. A list of plant species with their abundance was compiled for 850 sample plots of 0.5 × 0.5 m located in microsites of different types in the studied forest types. Above- and belowground phytomass of vascular plants and mosses have been measured in 170 sample plots of 0.5 × 0.5 m in triple replication for each microsite type in the different forest types; phytomass of plants on inter-crown microsites dominated by different species were measured separately. Belowground phytomass was defined in a root layer of 50 cm depth. All plants together with their roots have been taken out of the plot, detached from their soil, and then separated into their above- and belowground parts according to the method described by Rodin et al. (1968). Mosses were also separated in assimilative (green) and non-­ assimilative parts (fulvous or yellowish-brownish in color). For dwarf shrubs, annually deciduous leaves, perennial living leaves, perennial dead leaves, and perennial sprouts were also separated. Annual aboveground litter fall of the field layer was also measured; it consisted of the aboveground parts of herbaceous species and annual leaves and dead perennial leaves of dwarf shrubs. Below we present the following results on our vegetation study: (i) general descriptions of the studied forest types, (ii) composition and structure of the tree populations in the forest types, and (iii) microsite structure and phytomass analysis of the ground layer in the boreal tall herb spruce-fir forest.

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3.4.4  General Description of the Studied Forests Old-growth, uneven-aged dark coniferous forests occupying the study area, mainly with Picea obovata and Abies sibirica, have been classified into the five forest types belonging to the five different sections described in the Prodromus of boreal forests (see Sect. 3.1). Forests of the boreal tall herb, large fern, green moss, sphagnum, and boreal swamp sections are presented here (Smirnova et  al. 2011; Smirnov 2013) (Fig. 3.21). Vast areas of poorly drained slope bottoms with stagnant moisture are occupied by sphagnum spruce forests. Boreal swamp Picea obovata forests grow along streams with running water. The rest of the area with good and moderate drainage is occupied by boreal tall herb, large fern, and green moss spruce-fir forests. Boreal tall herb spruce (Picea obovata) and fir (Abies sibirica) forests with Pinus sibirica (Piceeto-Abieta magnoherbosa) dominated by Abies sibirica and Picea obovata with a significant presence of Pinus sibirica grow in a wide area on the upper part of wooded slopes in the east of the study region; these forests are also located on the middle parts of slopes in the west and north of the region (Fig. 3.21). They adjoin green moss, sphagnum, and large fern forests. The cover of the overstorey varies from 10 to 60%; large gaps occur in the canopy (Figs. 3.23 and 3.24a). Abies sibirica and Picea obovata dominate in the undergrowth, with presence of

Fig. 3.23  A gap in the canopy of Piceeto-Abieta magnoherbosa in the Bolshaya Porozhnaya River basin with Aconitum septentrionale, Rubus idaeus, Geranium sylvaticum, Chamaenerion angustifolium, Dryopteris carthusiana, and young individuals of Picea obovata which all are located in the pit formed by treefall with uprooting (Photo by M. Bobrovsky)

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Fig. 3.24  Tree crown projections in plots located in the Bolshaya Porozhnaya River basin: (a) boreal tall herb spruce-fir forest; (b) large fern spruce-fir forest and (c) green moss spruce-fir forest

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Olg

90%

Wt

80%

Md

70%

Nt

60%

Nm

50%

40%

TFr

30%

TH

20%

Br_m

10%

Br_dw

0%

BrTHerb

LFern

GMoss

Sph

NtTHerb

Pn

Fig. 3.25  Proportion of vascular species of different ecological-coenotic groups in the studied forest types in the Bolshaya Porozhnaya River basin: BrTHerb boreal tall herb spruce-fir forests, LFern large fern spruce-fir forests, GMoss green moss spruce-fir forests, Sph sphagnum spruce forests, NtTHerb nitrophilous tall herb spruce forests. Ecological-coenotic groups: Pn piny group, Br_dw boreal dwarf shrubs, Br_m boreal small herbs and ferns, TH boreal tall herbs, TFr large ferns, Nm nemoral, Nt nitrophilous, Md meadow-edge, Wt water-marsh, and Olg oligotrophic groups (see Sect. 2.2)

Betula pubescens; Pinus sibirica and Sorbus aucuparia also occur. Cover of the understorey layer is 10–30%. Species richness is quite high: Spiraea media and Rosa acicularis locally grow abundantly; Ribes hispidulum, Lonicera pallasii, and Daphne mezereum also occur. Cover of the field layer is 70–90%; it consists of three sublayers formed by species of different ecological-coenotic groups (Fig. 3.25). In the upper sublayer, the tall boreal herbs Aconitum septentrionale, Actaea erythrocarpa, Cacalia hastata, Crepis sibirica, Delphinium elatum, and Paeonia anomala dominate (Fig. 3.26). In the middle sublayer, nemoral plants dominate: they include the early spring plants Corydalis bulbosa, Gagea lutea, and Anemonoides altaica and the summer plants Lathyrus vernus, Milium effusum, Paris quadrifolia, and Stellaria holostea. Nitrophilous (Stellaria nemorum) and meadow-edge plants (Vicia sepium, Ranunculus propinquus, etc.) also occur in the middle sublayer. In the lower field sublayer, small boreal herbs such as Gymnocarpium dryopteris, Maianthemum bifolium, Avenella flexuosa, and Oxalis acetosella dominate. Boreal small herbs with Vaccinium myrtillus also occur on fallen trees of the first to second stages of overgrowing where the boreal green mosses Pleurozium schreberi, Hylocomium splendens, etc. together with bushy lichens (species of the genus Cladonia) dominate. V. vitis-idaea and sometimes bushy lichens grow at the base of the trunks of large coniferous trees. The soil surface in the under- and inter-tree crown microsite areas is covered by hemiboreal mosses (species of the genus Plagiomnium and Rhodobryum roseum). Total cover of the bottom layer is 5–10%. All plant diversity parameters in the boreal tall herb spruce-fir forests were higher compared to plant diversities calculated for the other forest types occupying

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Number of species

250 200 150 100 50 0

BrTHerb LFern

GMoss

Forest types

Sph

NtTHerb

Number of species per 100 m2

Fig. 3.26  Piceeto-Abieta magnoherbosa with Paeonia anomala in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

40 30

V M

20 10 0

BrTHerb LFern GMoss

Sph NtTHerb

Forest types

Fig. 3.27  Plant species diversity in the studied forest types in the Bolshaya Porozhnaya River basin: left species richness, right species density. Abbreviations of forest types are the same as in Fig. 3.25. V vascular plants, M mosses

the good and moderately drained positions on the slopes and the watersheds in the study region (Fig. 3.27). A high level of species and structural diversity is maintained through a complex system of microsites in this forest type which we describe below. Besides the high level of plant diversity, other attributes of the boreal tall herb spruce-fir forests are the following: (i) the phytomass of mosses is minimal compared to the other studied forest types and (ii) the above- and belowground p­ hytomass

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Table 3.1  Phytomass in the ground layer for the main forest types in the Bolshaya Porozhnaya River basin (g/m2, oven-dry weight) Phytomass of vascular plants

Phytomass of mosses Annual litter fall in the total Annual phytomass of vascular plants, Above­- Below­litter Above­- Below­% ground ground Total ground ground Total fall Forest types 235.2 381.8 141.1 36.9 6.0 6.3 12.3 Boreal tall herb 146.6 spruce-fir forests 144.0 543.2 687.2 131.4 19.1 24.8 17.2 42.0 Large fern spruce-fir forests 69.4 132.0 201.4 22.0 10.9 62.4 60.9 123.3 Green moss spruce-fir forests Sphagnum 46.8 113.9 160.7 42.4 26.4 169.3 133.1 302.4 spruce forests

of vascular plants (in which the phytomass of tall herb species dominates) is large (Table 3.1). High values of the annual litter fall from the aboveground parts of vascular plants are also typical for this forest type. The high content of mineral elements in the aboveground parts of tall herbs (Lukina and Nikonov 1998; Bobkova and Galenko 2001; Lukina et al. 2010) together with the high values of annual litter fall in the boreal tall herb spruce-fir forests mainly defines the fertility of the brown soil (Cambisols) formed in this forest type (Bobrovsky 2010). On the whole, brownzems (Cambisols) with a well-structured humus horizon, a high content of organic matter (3.5–5.5%), and a low differentiation of the profile in granulometric composition dominate in the boreal tall herb spruce-fir forests (Fig.  3.28). Brownzems form mainly at medium loamy substrates. Humic and Dystric Cambisols also occur there (Bobrovsky 2010; Semikolennykh et al. 2013). All features of the boreal tall herb spruce-fir forests, including the high level of species and structural diversity and the well-structured rich soils with their high moisture capacity, indicate that these forests have developed for a long time in the absence of fire. We can presume that the boreal tall herb spruce-fir forests are the non-fire refugia in the study area. Large fern spruce (Picea obovata) and fir (Abies sibirica) forests with Pinus sibirica (Piceeto-Abieta magnofilicosum) occupy a sizeable area on the middle part of the slope in the east of the study area; in the west they occur on the watershed ridge and the upper part of the slopes (Fig. 3.21). The overstorey is dominated by Picea obovata and Abies sibirica with Pinus sibirica; Betula pubescens also occurs. Relatively serried sections in the overstorey (50–60% of the cover) alternate with large gaps (Fig.  3.24b). The undergrowth mainly consists of Picea obovata and Abies sibirica, with some Betula pubescens; singular individuals of Pinus sibirica

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Fig. 3.28  Typical soil profile (Cambisol) in the Piceeto-Abieta magnoherbosa in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

can be found. The shrub layer is poorly developed; it consists of Rosa acicularis and Juniperus communis. Total cover is 10–20%. The large fern Dryopteris dilatata dominates in the field layer with a cover of up to 90–100% and frond heights of 100–150 cm (Fig. 3.29). The fern forms a dense network of thick rhizomes and numerous appendicular roots in the soil. We have excavated rhizomes of 0.5 to 1.5 m in length and estimated the age of their living parts through the number of fronds on the rhizome: these were up to 200 years old. However, the presence of dead and decaying parts of these rhizomes in the soil suggests that the oldest individuals of the fern are much older. Under Dryopteris dilatata, small boreal herbs, such as Gymnocarpium dryopteris, Maianthemum bifolium, Oxalis acetosella, and Linnaea borealis, and the dwarf shrub Vaccinium myrtillus and others occur in very low abundances; they form a weakly developed second sublayer in the field layer. Under the shading canopy of Dryopteris dilatata, the bottom layer of boreal green mosses is also poorly developed. Pleurozium schreberi and Hylocomium splendens only dominate on some large fallen trees in the first stage of overgrowing (see above). Though plant diversity in this forest type is minimal, we found that total phytomass of the ground layer of the vegetation was high, due to the huge belowground phytomass of Dryopteris dilatata (Table  3.1). The absolute domination of this fern in the above- and belowground parts of the ground

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Fig. 3.29  Piceeto-Abieta magnofilicosum with Dryopteris dilatata in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

layer determines the low species diversity and the very poor ecological-coenotic structure of the large fern forests in the study area (Figs. 3.25 and 3.27). Tree undergrowth occurs mainly on fallen logs which are quickly covered by fallen-over fern fronds. Immature plants often die, and young virginal trees of low vitality mainly occur on fallen logs located in narrow strips under the edges of tree crowns where shading conditions and dropped needles of the conifers hamper the development of Dryopteris dilatata. Probably, Dryopteris dilatata dominates over quite some large areas as a result of the ancient (500 years or longer ago) exposure of soils on slopes after the large-­ scale and repeated fires that have been described from the Ural Mountains (Korchagin 1940). But presently it is often impossible to find traces of these fires, because the charcoal, together with the soil, has been washed out down the hills. Spore plants (ferns and horsetails in the study area) are the first which recover on the eroded soils after large-scale fires. The restoration of other plants in the ground layer is hampered by the large, vigorous ferns through light, water, and nutrient competition. Al-Fe-humic podzols (Haplic Podzols) with light and medium loam content prevail (Fig. 3.30); podburs (Entic Podzols) also occur. Green moss spruce (Picea obovata) and fir (Abies sibirica) forests (Piceeto-­ Abieta hylocomiosa) (Fig. 3.31) occur widespread in the boreal region, as opposed to forests described above. In the study area, they occupy the middle parts and bottoms of the slopes (Fig. 3.21). Patches of these forests also occur within the sphag-

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Fig. 3.30  Typical soil profile (Haplic Podzol) in the Piceeto-Abieta magnofilicosum in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

Fig. 3.31  Piceeto-Abieta hylocomiosa with Vaccínium myrtíllus, Pleurozium schreberi, and Hylocomium splendens in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

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num forests, but they are not shown on the map owing to their small patch sizes. Locally, the piedmont relief brings a great diversity in vegetation and no extensive communities corresponding to pure subsections of green moss – dwarf shrub forests or green moss – small boreal herb forests occur. Therefore, we describe these forests at the level of the section of green moss forests according to the Prodromus of the boreal vegetation explained in Sect. 3.1. Picea obovata and Abies sibirica prevail in the overstorey; Betula pubescens (often) and Pinus sibirica (sporadically) also occur; total crown cover is 40–60% (Fig. 3.24c). The undergrowth mainly consists of Picea obovata and Abies sibirica; young trees of Betula pubescens occur on old, decayed logs and on mounds formed after treefall with uprooting. The shrub layer is poorly developed; its cover is not more than 15%; Sorbus aucuparia, Juniperus communis, and very rarely Ribes rubrum can be found. Cover of the field layer is 70–90%; sublayers are absent; boreal dwarf shrubs (Vaccinium myrtillus, Linnaea borealis) and boreal small herbs (Gymnocarpium dryopteris, Maianthemum bifolium, Avenella flexuosa, Oxalis acetosella) dominate (Fig. 3.25). The species diversity is higher than in the large fern forests but considerably less than in the boreal tall herb forests (Fig. 3.27) because of the poor development of treefall mosaics (Zaprudina 2012; Lugovaya et  al. 2013). Cover of the bottom layer is 70–90%. Boreal green mosses dominate not only on the fallen logs at the first stage of overgrowing, as we observed in the forests of the previous sections, but they also prevail in the under-crown and inter-crown microsites. Pleurozium schreberi and Hylocomium splendens occur in practically all sample plots and with high abundance. In some plots Ptilium crista-castrensis or Polytrichum commune dominates. The proportion of mosses in the total phytomass of the ground layer is 38% in green moss forests, whereas it is 6% and 3% in the large fern and boreal tall herb forests, respectively (Table 3.1). At the same time, the annual fall of aboveground parts of vascular plants is six or more times lower in the green moss forests than in the boreal tall herb and large fern forests and consists only of the litter of Vaccinium myrtillus and some boreal herbs. This small annual litter fall of vascular plants together with its low content of minerals determines the poor nutrient status of the soils formed under the green moss forests (Lukina and Nikonov 1998; Lukina et al. 2010). Al-Fe-humic podzols (Haplic Podzols) with gleyzems (Gleysols) prevail in the green moss spruce-fir forests. The bleached horizon (Albic) is mostly thin. Peaty podzols (Histic Podzols), gley-podzolic soils (Gleyic Albeluvisols), and Humic Umbrisols and Cambisols (dystric) are also found. Sphagnum spruce (Picea obovata) forests with Betula pubescens and Pinus sibirica (Piceeta sphagnosa) occupy the poorly drained bottoms of slopes with stagnant moisture (Fig. 3.21). Most likely, the vast areas with sphagnum forests in the Bolshaya Porozhnaya River basin, as well as throughout the boreal region, are associated to a great extent with large crown fires which occurred over 500 years ago and resulted in extensive areas of waterlogging. These forests have not been sufficiently studied yet, so we describe them only at the level of the section according to the Prodromus (Sect. 3.1).

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Picea obovata dominates the overstorey with a lower proportion of Betula pubescens and Pinus sibirica; Abies sibirica occurs sporadically; the total crown cover is 30–50%. Stagnant moisture is not good for Abies sibirica and that is why it is rare in these stands, though it is always present in the undergrowth where it often takes on a creeping form. Cover of the shrub layer is 10–40%; Sorbus aucuparia dominates, and Juniperus communis occurs. Cover of the field layer is 20–60% and of the bottom layer 90–95%. Sphagnum forests most significantly differ from other forests because of their pronounced dominance of Sphagnum mosses (Sphagnum fallax, S. magellanicum, S. girgensohnii) in the under-crown and inter-crown microsites together with a presence (or dominance) of boreal green mosses (Pleurozium schreberi first of all) on fallen logs at the first stage of overgrowing. The occurrence of vascular plants, as well as mosses, differs according to the type of microsite. Oligotrophic species, such as Carex globularis, C. loliacea, Comarum palustre, Rubus chamaemorus, etc., are most frequent in the flat areas of the inter-crown and under-crown microsites and in small depressions. Equisetum sylvaticum also often dominates there (Fig. 3.32), owing to its ability to survive on the most acid and poorest soils. Boreal dwarf shrubs and small herbs, such as Vaccinium myrtillus, Orthilia secunda, Rubus arcticus, Trientalis europaea, etc., often occur on the large logs and on the elevations around the trunks of the trees. Species diversity in the ground layer is similar to that in the green moss forests (Fig. 3.27). The slightly greater plant diversity in the sphagnum forests results from

Fig. 3.32  Piceeta sphagnosa with Equisetum sylvaticum in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

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a greater diversity of the environment that allows the growth of ecologically different species. There are microsites with different conditions of both abiotic (connected with water, relief, and rocks) and biotic (tree breakups, tussocks of sedges and grasses, etc.) origins. The ecological-coenotic structure of the sphagnum forests is very similar to that of the green moss forests but with a larger proportion of oligotrophic plants (Fig. 3.25). The proportion of mosses in the total phytomass of the ground layer is more than 65% and that distinguishes the sphagnum forests from all others (Table 3.1). The high abundance of Sphagnum mosses, which produce acidic litter and create a special temperature regime by forming “a cushion” of moss litter that delays the warming of the soil, creates unfavorable conditions for the activities of soil microorganisms and fauna (Bobrovsky 2010). Together with the abundant moisture, which leads to the development of gley processes, this defines the low level of soil fertility in this forest type (Lukina et al. 2010). Peaty gley soils (Histic Gleysols) dominate in the sphagnum spruce forests; peaty podzols (Histic Podzols) also occur. The peaty horizon is from 10 to 12; sometimes more cm thick and heavy loamy substrates prevail. Boreal swamp spruce forests are represented only by the nitrophilous tall herb spruce (Picea obovata) forests (Piceeta nitrophilo-magnoherbosa) (Fig.  3.33) which, in the study area, grow along the streams with running water at localities with predominantly rocky substrates (Fig. 3.21). Picea obovata dominates in the

Fig. 3.33  Piceeta nitrophilo-magnoherbosa with Veratrum lobelianum, Geranium sylvaticum, Aconitum septentrionale, Polemonium caeruleum, and others in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

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overstorey and Betula pubescens often occurs; crown cover is 40–60%. Cover of the understorey is 20–40%. Picea obovata and Abies sibirica dominate in the understorey together with Alnus incana and Salix spp.; Lonicera pallasii, Sorbus aucuparia, and Ribes nigrum also occur. Cover of the field layer is 80–100%; it may consist of two or three sublayers. The upper sublayer is formed by boreal and nitrophilous tall herbs, such as Filipendula ulmaria, Calamagrostis langsdorffii, Cirsium oleraceum, etc. Nitrophilous and water-marsh herbs of middle stature, such as Crepis paludosa, Bistorta major, and Carex spp., grow in the second field sublayer. The third sublayer may be formed by low herbs of the same ecological-coenotic groups, e.g., Chrysosplenium alternifolium, Stellaria nemorum, Adoxa moschatellina, and Cardamine amara. Boreal dwarf shrubs and boreal small herbs, e.g., Vaccinium myrtillus, Gymnocarpium dryopteris, Oxalis acetosella, etc., occur on fallen logs and on the elevations close to tree trunks. Cover of the bottom layer is 20–60%. Green hemiboreal mosses of the genera Mnium, Plagiomnium, Brachythecium, and also Rhodobryum roseum and Aulacomnium palustre occur, together with green boreal mosses, such as Pleurozium schreberi, Hylocomium splendens, and Climacium dendroides. Species diversity in the nitrophilous tall herb forests is highest of all forests in this study area, though boreal tall herb forests follow closely (Fig.  3.27). The ecological-­coenotic structure of the field layer has a large proportion of nitrophilous, water-marsh and meadow plants (Fig. 3.25). Just as the boreal tall herb forest, these boreal swamp forests contain plants of all ecological-coenotic groups in the composition of their field layer, and this indicates the high diversity of ecological conditions in these forests. Weakly developed Fluvisols occur in the nitrophilous tall herb spruce forests that are prevalent in the Bolshaya Porozhnaya River basin. Dystric and Gleyic Fluvisols also occur in this forest type in the Reserve.

3.4.5  C  omposition and Structure of Tree Populations in Different Forest Types Stands of all studied forests consist of four tree species Picea abies, Abies sibirica, Pinus sibirica, and Betula pubescens, but the dimensional proportions of trees, ages, and the ontogenetic structures of the tree populations are different. In the tall herb spruce-fir forests, Abies sibirica dominates by number of stems, but Picea obovata dominates by sum of diameters at breast height (DBH) of trees >2 cm DBH (Table 3.2). Pinus sibirica and Betula pubescens lag noticeably behind those species by number of stems, but the total of DBH values of Pinus sibirica is quite high (4  m2/ha), though that of Abies sibirica and Picea obovata is twice, respectively, four times as high.

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Table 3.2  Stand characteristics of the studied Picea obovata-Abies sibirica forests in the Bolshaya Porozhnaya River basin

Tree species Abies sibirica Picea obovata Pinus sibirica Betula pubescens Total

Tall herb forest Sum of Density DBH (trees/ha) (m2/ha) 337 8.24

Large fern forest Sum of Density DBH (trees/ha) (m2/ha) 542 15.40

Green moss forest Sum of Density DBH (trees/ha) (m2/ha) 320 5.98

Sphagnum forest Sum of Density DBH (trees/ha) (m2/ha) 632 3.29

262

16.38

381

9.51

436

24.67

930

19.37

17

4.02

17

6.24

8

2.58

68

2.61

18

0.28

53

0.41

52

3.79

182

7.12

634

28.92

993

31.56

816

37.02

1812

32.39

Abies sibirica’s DBH ranged from 2.5 cm to 47 cm with a distribution smoothly decreasing toward the larger DBH classes (Fig. 3.34). Stems with largest diameters (38–42  cm) also were tallest (28.0–28.4  m). The largest tree, with a diameter of 47 cm, was 196 years old, but it was sheer luck that it was possible to determine its age as almost all trees of 18 cm or thicker were afflicted by stem rot. We were also lucky to be able to determine the age of a tree with a diameter of 22.9 cm (it was 129 years old) and one with a diameter of 28.2 cm (146 years old). For trees with DBHs from 4 to 18 cm, ages ranged from 15 to 108 years. Increasing ages of the trees with increase of their diameters suggest that the age measured for the largest tree was close to the maximum age of Abies sibirica trees in the sample plots located in this forest type. Picea obovata’s DBH ranged from 2.4 to 76.3  cm and showed a continuous bimodal distribution with peaks at the lower and middle DBH classes (Fig. 3.34). The range of Picea obovata diameters was widest here compared with its DBH ranges in plots located in all other studied forest types. The thickest (till 70 cm) and the tallest (till 33 m) trees of Picea obovata were found in this forest type. For trees with DBHs from 4 to 48 cm, ages ranged from 20 to 224 years. Luckily we could determine the ages of some larger trees not afflicted by stem rot. A tree with a diameter of 52.9 cm was 145 years old and one with a diameter of 62.3 cm was 201 years old. We found no correlation between DBH and age of Picea obovata trees, and thus we can only conclude that the maximum measured age for Picea obovata in our study area was 224 years. Abies sibirica and Picea obovata had normal ontogenetic spectra in the sample plots located in the tall herb spruce-fir forests, and this testifies to the steady state of these tree species populations in this forest type (Fig. 3.35). Pinus sibirica’s DBH ranged from 4 to 78 cm and showed a discontinuous distribution and an asymmetric dominance of trees of the higher size classes (Fig. 3.34).

Number of trees/ha

3  Boreal Forests Picea obovata - Abies sibirica tall herb forest

1000

10 1

Number of trees/ha

20

36

52

68

84

Picea obovata - Abies sibirica large-fern forest

1000 100 10 1 4

20

36

52

68

84

Picea obovata - Abies sibirica green moss forest

1000 100 10 1 4

20

36

52

68

84

Picea obovata sphagnum forest

1000 Number of trees/ha

Abies sibirica Picea obovata Pinus sibirica Betula pubescens

100

4

Number of trees/ha

137

100 10 1 4

20

36

52

68

84

DBH class, cm

Fig. 3.34  Stem distribution of the main tree species per DBH classes in sample plots located in the studied forest types in the Bolshaya Porozhnaya River basin (DBH ≥2 cm; DBH range 4 cm). Numbers of stems per hectare are presented on a logarithmic scale

Number of trees/ha

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1000 100 10 1

1000

v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 Abies sibirica Picea obovata Pinus sibirica Betula pubescens Picea obovata - Abies sibirica large-fern forest

100 10

Number of trees/ha

1

1000

Number of trees/ha

Number of trees/ha

Picea obovata - Abies sibirica tall herb forest

1000

v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 Abies sibirica Picea obovata Pinus sibirica Betula pubescens Picea obovata - Abies sibirica green moss forest

100 10 1

v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 Abies sibirica Picea obovata Pinus sibirica Betula pubescens Picea obovata sphagnum forest

100 10 1

v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 v1 v2 g1 g2 g3 Abies sibirica Picea obovata Pinus sibirica Betula pubescens

Fig. 3.35  Ontogenetic structure of tree populations in the studied forest types in the Bolshaya Porozhnaya River basin: v1, v2 virginal plants of the first and second subgroups; g1, g2, g3 young, mature, and old reproductive plants (an explanation of the ontogenetic stages is given in Sect. 2.5). Numbers of stems per hectare are presented on a logarithmic scale

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25

Number of trees/ha

1

2

3

4

20

15 10 5 0

4

20

36

52

68

84

DBH class, cm Fig. 3.36  Stem distribution of Pinus sibirica per DBH classes in sample plots located in the studied forest types in the Bolshaya Porozhnaya River basin (DBH ≥2 cm; DBH range 4 cm). Numbers of stems per hectare are presented on a metric scale. 1 Tall herb forests, 2 large fern forests, 3 green moss forests, 4 sphagnum forests

Most DBH classes were represented by only one stem (Fig. 3.36). Maximum height of trees was little more than 25 m. We managed to determine the ages of two Pinus sibirica trees of different diameters: a tree with a diameter of 26 cm was 130 years old and one of 47.9 cm was 156 years old. Pinus sibirica had a fragmentary ontogenetic spectrum with a predominance of generative trees and a low number of immature and virginal individuals (Fig. 3.35). There was no sustainable renewal of Pinus sibirica, probably because the strong ground layer prevents the germination of seeds. Currently generative individuals apparently have been able to grow after some large disturbance(s) had resulted in damage of the former field layer. Betula pubescens’ DBH ranged not very widely (from 2.7 to 41.7 cm) and had an asymmetric distribution (Fig. 3.34). Trees thicker than 10 cm occurred sporadically. Height of the largest tree was 19.9  m. Age was not determined. Betula ­pubescens had a fragmentary ontogenetic spectrum with a predominance of virginal trees (Fig. 3.35). In the large fern spruce-fir forest, Abies sibirica dominates both by number of stems and by sum of DBH (Table 3.2). Values for Picea obovata are 1.5 times lower than Abies sibirica but exceed Pinus sibirica and Betula pubescens, though summed DBH values of Pinus sibirica are rather high (6.24 m2/ha) and account to maximally 19.8% of the total DBH sum in the stand. Abies sibirica’s DBH ranged from 2.5 cm to 51.6 cm with a similar, smooth but asymmetric, distribution as in the previous forest type, but the number of stems in each DBH class was higher and the sum of DBH values also was higher; in fact, it had the highest sum of all forest types. The thickest trees (DBH till 46 cm) were

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highest (27.4–28.7 m), but they occurred sporadically. Age was determined for trees from 6 to 34 cm DBH as from 24 to 247 years old. All trees thicker than 34 cm were afflicted by stem rot. Picea obovata’s DBH ranged from 2.0 to 56.1  cm with the same asymmetric concentration in the smaller DBH classes. Despite the prevalence of Abies sibirica in this forest type, the largest Picea obovata individuals were twice as common as the largest Abies sibirica trees. The thickest trees reached a height of 30.0 m. Ages, as measured for trees from 6 to 36 cm, ranged from 23 to 213 years old. All trees thicker than 36 cm were afflicted by stem rot. Abies sibirica and Picea obovata had continuous, normal ontogenetic spectra with prevalence of immature and virginal individuals that indicates the steady state of these tree populations in the large fern spruce-fir forest (Fig. 3.35). Pinus sibirica’s DBH varied from 3.0 to 97.5  cm and thus reached here their highest DBH values of all studied forest types (Fig. 3.35). With increasing ­diameters from 48.0 to 98.0 cm, the height of the trees increased slightly from 21.6 to 24.9 m. It was impossible to precisely determine the ages of large trees because of stem rot. However, according to incomplete cores, we can presume that the oldest Pinus sibirica was 400–500 years old. The ontogenetic spectrum of Pinus sibirica indicates regression with its prevalence of old generative trees (Fig. 3.35), and thus it indicates that the entire population is extremely instable. As in the previous forest type, there is no sustainable rejuvenation of Pinus sibirica. The reason may again be a strong ground layer in this forest type which prevents establishment of Pinus sibirica seedlings. We presume that the currently existing generative individuals have grown up after a strong disturbance of the former field layer, but we have to point out that the environmental conditions needed for a successful growth of Pinus sibirica in the first ontogenetic stages are still poorly understood. Betula pubescens’ DBH ranged from 2.8 to 34.9 cm with an intermittent asymmetric distribution showing an absolute predominance of trees of the lower DBH classes. Trees thicker than 20 cm occurred sporadically. The largest trees reached 13.5 m in height. Ages were not determined. This species had an invasive ontogenetic spectrum with a prevalence of virginal individuals (Fig. 3.35). In the green moss spruce-fir forest, Picea obovata dominated both by sum of DBH and by number of stems (Table 3.2). The small proportion of Abies sibirica in this forest type is most likely explained by local waterlogging and poor soils typical for this forest type as well as by local fires resulting from the activities of fishermen and hunters. The proportion of Pinus sibirica was minimal in this forest type. Betula pubescens was significantly inferior to Abies sibirica and Picea obovata by number of stems but close to Abies sibirica by sum of DBH. Abies sibirica’s DBH ranged narrowly from 2.2 to 33 cm with a predominance in the smaller DBH classes. We suppose that practically all Abies sibirica individuals have grown up since the last ground fire. Large trees of 30–33 cm in DBH and 23–25  m in height occurred sporadically. Trees of 8–22  cm in DBH were 101– 146 years old. Thicker trees were mainly afflicted by stem rot, and the ages of trees

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which we were lucky to be able to measure were not correlated with DBH. Abies sibirica had a normal ontogenetic spectrum with a prevalence of young individuals (Fig. 3.35); the low number of generative individuals is probably due to the small time interval that has elapsed since the last ground fire. Picea obovata’s DBH ranged from 2.8 to 63.5 cm and showed a bimodal distribution (Fig. 3.34). Single, large trees formed the overstorey. Trees of 16–42 cm in DBH were 101–203 years old. There were single trees of more than 30 m high and more than 40 cm in DBH which were younger than most of the others: for example, a tree of 48.6 cm in DBH was 148 years old; another tree of 51.1 cm in DBH was 170 years old. These largest and tallest trees evidently grow in more favorable environments than other trees, for example, in a canopy gap formed after treefall. Picea obovata has a normal ontogenetic spectrum with a small prevalence of generative trees (Fig. 3.35). Only generative individuals of Pinus sibirica of 52.2–74.2  cm in DBH were found in this forest type (Figs. 3.34 and 3.36). The ages of the trees were not determined. The almost complete absence of large trees of Pinus sibirica can be explained by selective cutting in this forest type (Nepomilueva 1978), and the absence of young individuals may be due to the relatively high crown cover which is also indicated by the highest sum of DBH in this forest type (Table 3.2) and shown in crown cover mappings (Fig. 3.24c). Betula pubescens’ DBH ranged from 18.0 to 50.7 cm. Large trees of 20 m high prevailed. Young trees were practically absent due to the small number of treefalls with uprooting in this forest type: birch seeds need bare soil for germination and that habitat usually appears on mounds formed after treefall. The fragmentary ontogenetic spectrum with domination of mature and old generative individuals indicated the unstable state of the Betula pubescens population. In the sphagnum spruce forests, all four tree species occurred, but the proportions of these species in the stands were very different from all other forest types. Picea obovata absolutely prevailed by number of stems and by sum of DBH (Table 3.2). Despite the high number of Abies sibirica stems, its DBH sum was only 10.2% from the total DBH sum, as there was a prevalence of young, small trees of Abies sibirica (Fig. 3.34). The proportion of Pinus sibirica stems was highest in this forest type and accounted for 3.8%. Betula pubescens was strongest represented in this forest type compared to the other types, most likely due to its resistance to stagnant moisture. Abies sibirica grew mainly in the form of dwarf trees on peaty gley soils with a high moisture content. DBH varied over a very narrow range from 4 to 20 cm with a strong concentration in the smaller DBH classes. Large trees of 18–20 cm in DBH and 14 m in height occurred sporadically. Ages varied from 24 to 181 years old. The species showed an invasive ontogenetic spectrum without mature and old generative individuals (Fig. 3.35). Picea obovata’s DBH also varied over a narrower range as compared with the other forest types: from 2.9 to 43.3 cm and with an asymmetric distribution concen-

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trating at the smaller DBH classes (Fig. 3.34). Largest trees of 40–44 cm in DBH were the tallest and reached 24–25  m. Ages varied from 70 to 237  years old. Probably the environmental conditions in the sphagnum forest are not good for the dimensional development of Picea obovata, although all population parameters indicated a steady population state and a normal ontogenetic spectrum with prevalence of young individuals. Pinus sibirica’s DBH ranged from 3.2 to 49.7 cm falling mainly in the smaller classes. Probably this is the first generation of Pinus sibirica trees after a strong disturbance. Maximal height of the trees was 21.6 m. Young trees of 4–12 cm in DBH were 42–89 years old. Larger trees were afflicted by stem rot. The ontogenetic spectrum of this species differed from all other forest types (Fig. 3.35). It was normal with generative individuals of all stages and a prevalence of immature and virginal individuals, indicating a steady state of the Pinus sibirica population in this forest type. Betula pubescens’ DBH ranged from 4.1 to 37.3 cm with a continuous, unimodal distribution and a prevalence of middle-sized individuals. Practically all trees of DBH > 20 cm were more than 20 m high and formed the overstorey. Ages of trees were not measured. The normal ontogenetic spectrum with a dominance of ­generative individuals indicated that the Betula pubescens population is in a steady state, but the population size will decrease in this forest type. The high proportion of generative trees of Betula pubescens may result from large crown fires or disturbances by windfall that occurred long ago. Summarizing, there are uneven-aged multi-species stands in all studied forest types. Abies sibirica and Picea obovata prevailed in all forest types by their number of stems. According to DBH sums, Picea obovata dominates in all communities except for the large fern spruce-fir forests where Abies sibirica dominates. There are normal ontogenetic spectra and normal DBH distributions of Abies sibirica and Picea obovata in all studied forest types, indicating that these tree species have stable population states. The regressive or fragmentary ontogenetic spectra of Pinus sibirica in all communities with exception of the sphagnum forest type, together with its DBH ­distribution, indicate the possibility that this species may disappear from the stands. The normal ontogenetic spectrum and DBH distribution of Pinus sibirica in the sphagnum forest indicate a stable state of Pinus sibirica there. The regressive ontogenetic spectrum of Betula pubescens in the green moss spruce-fir forest suggests that this tree species may be lost from the stand, but its invasive ontogenetic spectrum in the large fern spruce-fir forests and its fragmentary spectrum with prevalence of young individuals in the tall herb spruce-fir forests indicate that Betula pubescens may survive in these forest types. The normal ontogenetic spectrum of Betula pubescens with a predominance of generative individuals in the sphagnum spruce forest testifies the relatively stable state of this population there with a possible future decrease of its population size.

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3.4.6  S  pecies and Structural Diversity of the Vegetation in Microsites Developed in the Boreal Tall Herb Spruce-­ Fir Forests The high level of species diversity in the boreal tall herb spruce-fir forests is continuously maintained by the microsites formed by the life and death of tree species (Fig. 3.37). Of the 13 types of microsites described above, we observed the highest values for richness of vascular plant species in inter-crown areas (Fig. 3.26) as well as in pits (Fig. 3.23) and under-crown sites. The lowest number of vascular plants was found on fallen logs at the first and second stages of overgrowth (Fig. 3.38). Vascular plant a

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Fig. 3.37  Species richness (a) and ecological-coenotic structure (b) of vascular plants growing in the studied microsites in the boreal tall herb spruce-fir forests in the Bolshaya Porozhnaya River basin. Microsites: IC inter-crown area, UC under-crown area; El elevations close to tree trunk; Pit1-Pit3 pits from the first to the third stages of decay; Mnd1-Mnd3 mounds from the first to the third stages of decay; Log1–Log4 fallen logs from the first to the fourth stages of overgrowth. Ecological-coenotic groups: Pn piny species, Br_dw boreal dwarf shrubs, Br_m boreal small herbs, TH boreal tall herbs, TFr tall (large) ferns, Nm nemoral, Nt nitrophilous, Md meadow-edge, and Wt water-marsh species

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Fig. 3.38  Fallen log at the second stage of overgrowth with Oxalis acetosella, Dryopteris carthusiana, Pleurozium schreberi, and the immature individuals of Picea obovata in the Piceeto-Abieta magnoherbosa in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

diversity on microsites related to pit-and-mound topography changes over time (Figs. 3.39 and 3.40): the number of plant species growing on the mounds and in the pits increases from the first to the second stage of decay and then slightly decreases to the third stage; the number occurring on fallen logs gradually increases from the first to the fourth stages of overgrowth. We also analyzed the occurrence of vascular plants with high frequencies. The species Linnaea borealis, Oxalis acetosella, Maianthemum bifolium, Trientalis europaea, Calamagrostis arundinacea, and Rubus saxatilis, belonging to the boreal dwarf shrub group and small herbs, were met with more than 60% frequency in all microsites except pits and mounds at the first stages of decay. This highlights the boreal character of the tall herb forests in general, because these plants are typical for spruce-fir communities. The nitrophilous species Stellaria nemorum and Chrysosplenium alternifolium frequently occurred in pits at the first and second stages of decay, probably because these microsites are the moistest and most fertile. The nemoral species Stellaria holostea, Milium effusum, and Adoxa moschatellina were frequent in the inter-crown area and in pits. The tall herbs Aconitum septentrionale, Geranium sylvaticum, Atragene sibirica, and Rubus idaeus were frequent in practically all microsites except pits of the first stage, fallen logs of all stages except the fourth stage of overgrowth, and on the elevations close to tree trunks. The piny dwarf shrub Vaccinium vitis-idaea was found in 92% of the plots in elevations close to tree trunks, but it occurred at lower frequencies in practically all microsites.

3  Boreal Forests Fig. 3.39  Pit with Paeonia anomala, Diplazium sibiricum, Geranium albiflorum, G. pretense, Milium effusum, and Stellaria nemorum and mound with Dryopteris dilatata at the first stage of decay in the Piceeto-­ Abieta magnoherbosa in the Bolshaya Porozhnaya River basin (Photo by A. Aleynikov)

Fig. 3.40  Pit with Aconitum septentrionale, Geranium sylvaticum, and Rubus idaeus and mound with Calamagrostis arundinacea at the second stage of decay in the Piceeto-Abieta magnoherbosa in the Bolshaya Porozhnaya River basin (Photo by M. Bobrovsky)

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Fig. 3.41  Species richness (a) and total phytomass (b) of vascular species and mosses in microsites studied in the boreal tall herb spruce-fir forests in the Bolshaya Porozhnaya River basin. Microsites are the same as in Fig. 3.37. V vascular species, M mosses

Comparison of the ecological-coenotic structure of the field layer shows that species of nearly all groups grow everywhere (Fig. 3.37b). Exceptions are fallen logs at the first stage of overgrowth where green mosses dominate, and further only boreal dwarf shrubs and small herbs occur. And water-marsh plants are overall poorly represented; they occur in just three types of microsites. The large ferns Dryopteris dilatata and Diplazium sibiricum do not occur under tree crowns, on the elevations close to tree trunks and on fallen logs of the first stages, while the proportion of meadow species is high on mounds at their first stage of decay. Mosses had their highest diversity in pits (37, 34, and 31 species in pits of the first, second, and third stages of decay, respectively) and on mounds (33 and 35 species on mounds of the first and second stages of decay); a similarly high species richness was also observed in the inter-crown areas (32 species) though the cover of the mosses was minimal there (5–15%) compared to other microsites (Fig. 3.41a).

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The maximal cover of the mosses of 70–100% occurred on fallen logs of the first and second stages of overgrowth. Rhodobryum roseum, Sciurohypnum reflexum, and species of the genus Brachythecium often occur in the inter-crown and under-­ crown areas. Hylocomium splendens and Pleurozium schreberi dominate on fallen logs, on pits, and on mounds. Additionally, Ptilium crista-castrensis, Rhytidiadelphus triquetrus, and species of the genus Dicranum were common on fallen logs; Polytrichum strictum and P. commune occur on mounds and species of the genera Mnium and Plagiomnium in pits. A total of 70 vascular plant species were found during the microsite study: 51 in such common forest microsites as inter- and under-crown areas and elevations close to tree trunks and 57 in microsites related to treefalls with uprooting (pits, mounds, and fallen logs). Of the 80 moss species encountered, 76 occurred in treefall-related microsites. This confirms the importance of treefalls with uprootings for the maintenance of a high level of plant diversity in the boreal tall herb forests.

3.4.7  P  hytomass of Vascular and Moss Species in Microsites Developed in the Boreal Tall Herb Spruce-Fir Forests The highest total values of above- and belowground phytomass were observed in the inter-crown areas, very largely due to the phytomass contribution of vascular plants (Fig.  3.41b). Total phytomass values of various vascular species differed threefold (Fig. 3.42). Highest values were shown by Dryopteris dilatata and Paeonia anomala and lowest by Aconitum septentrionale and Delphinium elatum. Phytomass

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Fig. 3.42  Total phytomass of vascular plants in the inter-crown microsites dominated by different tall herbs and large ferns in the boreal tall herb spruce-fir forests in the Bolshaya Porozhnaya River basin: A.s. Aconitum septentrionale, P.a. Paeonia anomala, C.s. Crepis sibirica, C.a. Chamaenerion angustifolium, D.e. Delphinium elatum, D.s. Diplazium sibiricum, and D.d. Dryopteris dilatata

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Fig. 3.43  Proportion of species of different ecological-coenotic groups in the total phytomass of vascular species in the microsites studied in the boreal tall herb spruce-fir forests in the Bolshaya Porozhnaya River basin. Microsites and ecological-coenotic groups are the same as in Fig. 3.37

of mosses in all inter-crown areas was very low despite the rather high diversity of their composition there (Fig. 3.41). Pits of the first two stages of overgrowth had lowest total phytomass values but also highest species diversity (Fig. 3.41). Fresh pits are newly formed microhabitats in which only seeds and vegetative parts such as sprouts and fragments of stolons or rhizomes with dormant buds can establish a plant, and these are small to start with. In a few years’ time, they gain larger biomass, and in addition some vegetative runners, such as those of Chamaenerion angustifolium or Crepis sibirica, can invade. At the second and third stages of pit overgrowth, total phytomass increased, and at the third stage, this was accompanied by a certain decrease in species diversity. Total phytomass values in other microsites were rather similar (Fig. 3.41). On mounds of the first stage of decay, Rubus idaeus dominated, but this pioneer species then declined and was replaced by other species which together scored lower phytomass values. Phytomass of mosses constantly increased from the first to the third stage of mound overgrowth. Total phytomass on fallen logs hardly varied from the first to the last stages, but the ratio of vascular plants to mosses gradually but strongly changed from dominance of green mosses at the beginning of log overgrowth to that of vascular plants. Analysis of the ecological-coenotic structure revealed that tall herbs formed more than half of the total phytomass of vascular plants on microsites in most of the 13 types: exceptions were fallen logs in the first three stages of overgrowth, elevations close to tree trunks, and pits of the first stage of decay (Fig. 3.43). The large ferns Dryopteris dilatata and Diplazium sibiricum also contributed strongly (31.7%) to the total phytomass of vascular plants in the inter-crown areas, while these two species make up just 4% of the total number of species in that type of microsite

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(Fig. 3.37). Large ferns also made up a large proportion of the vascular plant phytomass in pits of the last stage of decay. The main part of the phytomass of vascular plants growing on fallen logs of the first three stages of overgrowth and on elevations close to tree trunks is formed by boreal and piny dwarf shrubs, boreal evergreen plants, and small- and middle-sized boreal herbs (the Br_dw and Br_m groups in Fig. 3.43). More than half of the total phytomass of plants growing on fallen logs of the fourth stage of decomposition and overgrowth is formed by tall herbs, and they also account for the main part of the phytomass in practically all other microsites. Thus, in the tall herb spruce-fir forests, the ecological-coenotic structure of the field layer is constantly changing over time owing to the microsuccession driven by treefalls with uprooting and that leads to corresponding changes in the phytomass ratios of plants of different groups. Analysis of the species diversity and structure of the phytomass revealed fundamental differences between tall herb spruce-fir forests and the other forest types studied. The characteristics of the boreal tall herb spruce-fir forests are mainly determined by the occurrence of different types of microsites which are permanently generated by treefalls with uprooting. The mosaic of different types of microsites maintains a high level of biological diversity of vascular and moss plants and a diverse ecological-coenotic structure of the field layer. Boreal tall herbs with high ash values prevail in the phytomass in this forest type and determine the forming of litter with high ash and calcium contents. The latter leads to a rapid mineralization and then to the formation of an accumulative humus horizon in the soil (Bobrovsky 2010; Smirnova et al. 2011; Semikolennykh et al. 2013).

3.4.8  Conclusion Only old-growth, uneven-aged forests dominated by Picea obovata and Abies sibirica are situated within the Bolshaya Porozhnaya River basin in the Pechora-­ Ilych Nature Reserve. Picea obovata and Abies sibirica regenerate quite successfully in all these forests, but the structural characteristics of the forest ecosystems and the composition and structure of their ground layers, including phytomass values and soil characteristics, differ markedly. The abiotic factors stagnant moisture and running water are the most important determinants of the features of the Piceeta sphagnosa and Piceeta nitrophilo-magnoherbosa, respectively. Three other forest types, the Piceeto-Abieta magnoherbosa, Piceeto-Abieta magnofilicosum, and Piceeto-Abieta hylocomiosa, occupy practically similar locations with good and moderate drainage, and differences between these are mainly caused by the different effects of old and more recent catastrophic impacts, especially fires. The Piceeto-Abieta magnoherbosa apparently least experienced the impacts of fires and other catastrophic events. This is the richest forest type of the three as regards species and structural diversity of the vegetation and phytomass values of the ground layer and soil fertility. The gap-mosaic stand structure, pit-and-mound topography, and deadwood values are well developed. All tree species populations

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show a relatively stable state although the renewal of Pinus sibirica is somewhat weak. The Piceeto-Abieta magnofilicosum most probably are formed after severe fires on slopes which led to strong soil erosion. Probably, the large fern forests are formed in two different ways on those eroded soils: (1) spore plants first manage to recover on these soils and these large ferns have time to develop into a sufficiently powerful field layer to prevent a substantial growth of other species because of their strong competition for light, water, and nutrients, and (2) only large ferns do survive after fires due to their strong rhizomes and thus receive such an advantage at the start that they successfully outcompete other species. The main “negative features” of the Piceeto-Abieta magnofilicosum forests are their low species diversity of the ground layer (lowest of all forest types) and weakly developed soils. Tree undergrowth is quite good in these forests, except for the regeneration of Pinus sibirica. The gap-­ mosaic stand structure and pit-and-mound topography are quite well developed, but changes in the forest ecosystem toward an increase in species diversity and soil forming occur very slowly. Further research should clarify the reasons for this and should also reveal why there are such huge reserves of weakly decayed fern rhizomes in the soil. The Piceeto-Abieta hylocomiosa in the study area include the Piceeto-Abieta fruticuloso-hylocomiosa and P.-A. parviherboso-hylocomiosa forest types. These forests are typical for the boreal region. Even local but recurring fires lead to the forming of these forest types. Fires destroy both adult trees and tree undergrowth. This leads to a fragmentation of the tree species populations and results in stands with poorly developed gap mosaics and a weak development of pit-and-mound topography. In turn, this leads to a degeneration of the structural and species ­diversity of the ground layer, a decrease in phytomass values, and the formation of weak Podzols. Soil properties are mainly defined by the moisture regimes in these forest types. These forests can develop into three different ways. At locations near sphagnum forests and with an increase of stagnant moisture, the Piceeto-Abieta hylocomiosa can be transformed into Piceeta sphagnosa. If the number and quality of treefalls with uprooting are sufficient, various microsites for the establishment of herbaceous species will be formed, and the Piceeto-Abieta hylocomiosa can change into Piceeto-Abieta magnoherbosa if there also is enough seed drift of different plants including tall herbs. However, in the current state of these forests, treefalls with uprooting hardly lead to community transformations: green mosses and boreal dwarf shrubs continue to prevail in the ground layer, and the forests can remain in this quasistable state for a long time. Tree species with long life spans generally determine the structure of forest communities, the existence of microsites of different types, and the level of plant diversity associated with the microsite diversity. In the study area, in spite of a similar tree species composition, there are different types of old-growth dark coniferous forests with different structures of gap and microsite mosaics. These differences are determined by abiotic factors (especially soil moisture) as well as anthropogenic factors (especially the history of fires).

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3.5  P  lant Diversity and Soil Features in Old-Growth Spruce and Spruce-Fir Forests in the Boreal Region of European Russia 3.5.1  The Study Areas At the turn of the twentieth to twenty-first centuries, environmental nongovernmental organizations together with scholars from different countries began large-scale mapping projects of the intact forest landscapes remaining on Earth (Aksenov et al. 1999; Yaroshenko et al. 2001; Potapov et al. 2008). For European Russia, intact forest landscapes (IFL) were defined as areas essentially undisturbed by human development with an area of at least 500 km2 (Yaroshenko et al. 2001, 2008). An area was considered to be in an intact natural state if showing no signs of permanent settlements or communications, of industrial forest harvesting during the last 60 years, or mining, land clearing, and other essential human impacts. Besides forested areas, woodless bogs and highlands were also included into the IFL.  The technique of high-resolution satellite imagery (for the description of the method, see Sect. 2.3) and results of field expeditions in areas, where it was difficult to assess the actual level of disturbance, were used for the mapping. The results showed that the vast majority of IFL are located in the most remote areas of the far north; they all are located in the boreal region with the exception of a few large peat bogs (Fig. 3.44). In the rest of European Russia, and very likely in Europe as a whole, large intact natural forest landscapes no longer exist. IFL are mainly concentrated in the Murmansk region, in the west of Karelia (close to the Russia-Finland border), in the northern parts of the Arkhangelsk region and the Komi Republic, in the watershed between the Northern Dvina and Pinega rivers (Arkhangelsk region), in the east of the Komi Republic, and in the northeast of the Perm region. Study areas which have been investigated in the boreal forest region were mainly located inside the IFL (Fig. 3.44). Old-growth dark coniferous forests dominated by Picea spp. and Abies sibirica (in the east) occurred in all study areas. However, in this section we discuss the results of a comparative analysis of plant and soil diversity, not for all studied areas but for those where the maximal diversities of dark coniferous forests on the largest areas were found. All these areas are hard to access and very remote from roads and settlements. In the west, we analyzed study areas located in the northern part of the Pyaozersk forestry unit (near Mount Sieppitunturi, 250–350 m asl) and in the Kostomuksha State Nature Reserve, 200–250 m asl (numbers 2 and 3 in Fig. 3.44, respectively) (Smirnova and Korotkov 2001). Both areas are situated in Karelia, in the northern taiga. Other study areas are situated in the region of the northeastern European forests (see Sect. 1.3) and will be called “the eastern areas” in this section. They comprise four study areas in the western and central parts of the Komi Republic (numbers from 8 to 11 in Fig. 3.44) and two study areas on the western macro-slope of the Ural Mountains (numbers 12 and 13) (Smirnova et al. 2006). In the western and central parts of the Komi Republic, all studied forests are situated on elevated and/or some-

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Fig. 3.44  Map of intact forest landscapes in the boreal European Russian region (from Yaroshenko et al. (2001) with modifications) with localities of the field investigations. Numbers correspond to those in Table 2.1

what hilly plains, 180–250  m asl. Two study areas are attributed to the northern taiga: number 8 in the watershed between the Mezen and Vashka rivers and number 11 on the Middle Timan Ridge, in the basin of the Ukhta River. Two other areas are attributed to the middle taiga: number 9 in the upper reaches of the Vashka River and number 10 in the upper reaches of the Sedka and Suran rivers. On the western slope of the Ural Mountains, the study areas are attributed to the middle taiga and located in the Pechora-Ilych State Nature Reserve (number 12 in Fig. 3.44, Komi Republic) and the Vishera State Nature Reserve (number 13, Perm region). In the PechoraIlych Reserve, investigated areas include basins of right tributaries of the Pechora River: the Bolshaya Porozhnaya (see Sect. 3.4), Lugovaya, Yakov Rassokha, and Bolshoy, Shezhym rivers, all joining the mid-Pechora River in the stretch where it flows from the east to west; elevation of the areas varies from 250 to 600  m asl (Fig. 3.19). Investigated forests in the Vishera Reserve are located at elevations from 300 to 600 m asl in basins of the left (west) tributaries of the Vishera River. Thus, areas located in the Pechora-Ilych and Vishera reserves can be called “mountain study areas” as opposed to all others which can be called “plain study areas.” The main features of climate and macro-relief of the areas are described in Chapter 1. Some additional characteristics can be found in Sects. 3.3 and 3.4 where

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the vegetation of the Kostomuksha and Pechora-Ilych State Nature Reserves is presented. All described dark coniferous forests are located on watersheds or slopes with good and moderate drainage or in valleys of small rivers and streams, with the exception of wetlands and bogs.

3.5.2  Methods of Investigation Vegetation and soil data in old-growth forests dominated by Picea spp. (and Abies sibirica in the east) were sampled in 1996–2005 (Smirnova and Korotkov 2001; Smirnova et al. 2006). Phytosociological relevés at temporary square plots of 100 m2, ontogenetic data on Picea spp. populations, and soil morphological data were collected by the methods described in Sect. 2.4. More than 700 phytosociological relevés (203 plots in the west and 506 plots in the east) have been used to classify the vegetation and to assess structural and species diversity of plant communities by methods described in Sect. 2.5. Diversity of vascular species was estimated. To compare species richness between recognized forest community types in which we had sampled different numbers of relevés, we constructed species accumulation curves by the method of Colwell et al. (2012) and then calculated interpolation (rarefaction) estimates of species richness for the forest types. The Estimates program (Colwell 2013) and the R environment (R Development 2012) were used for the calculations. Soil morphology was described from about 50 soil pits in the western study areas and from about 100 soil profiles in the eastern study areas. Types and thickness of soil horizons and morphological features outside the horizons as well as presence, form, and locations of charcoal in the soil profile were analyzed.

3.5.3  Vegetation and Soil in the Studied Forest Types Old-growth dark coniferous forests dominated by Picea abies in the west and Picea obovata often with Abies sibirica in the east occupy all study areas. Betula pubescens also permanently occurs in the stands. Pinus sibirica occurs in the eastern areas in most forest types. Trees in the overstorey were 100–180 years old in the east and 120–240 years old in the west, but the maximal age of Picea spp. was equal in both regions and it was 380 years old. Phytosociological relevés were classified into 13 forest types belonging to four different sections described in the Prodromus of boreal forests (see Sect. 3.1, Table 3.3). Forests of the green moss, large fern, boreal tall herb, and boreal swamp sections were found in the selected study areas (Smirnova et al. 2006, 2007). In the western areas, pure green moss, green moss  – dwarf shrub, green moss  – small boreal herb, boreal tall herb, and nitrophilous tall herb spruce forests were found. In the eastern study areas, besides similar forest types, three additional forest types were found: (i) nemoral-boreal spruce-fir forests belonging to the green moss sec-

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Table 3.3  Picea abies and Picea obovata-Abies sibirica forests in the study areas Western study areasa Eastern study areasb Picea abies forests Picea obovata-Abies sibirica forests Section: Green moss forests Subsection of green moss – dwarf shrub forests, DwGM Pure green moss forests, GM Subsection of green moss – small boreal herb forests, BrGM Nemoral-boreal forests, NmBr Section: Large fern forests, LF Section: Boreal tall herb forests Plain boreal tall herb forests, BrTH Mountain boreal tall herb forests, mBrTH Section: Boreal swamp forests Subsection of nitrophilous tall herb forests, NtTH Numbers 2 and 3 in Fig. 3.44 Numbers from 8 to 13 in Fig. 3.44

a

b

tion but with a higher share of nemoral plants in the field layer, (ii) large fern spruce-­ fir forests, and (iii) mountain boreal tall herb spruce-fir forests (Table 3.3). According to results of numerical analyses (Figs. 3.45 and 3.46b), the mountain boreal tall herb spruce-fir forests differ from the other boreal tall herb forests (from now on called “plain”). Note, that in the east, plots belonging to all forest sections have been found both in plain and mountain areas, but only plots belonging to the boreal tall herb section differed between plain and mountain areas: they were located in different parts of ordination diagrams and differed in cluster analyses, so we classified them into the different forest types. Vegetation sample plots from the western and eastern study areas are compactly located with partial overlap in the ordination diagram (Fig.  3.45). The western sample plots are located in a more acid and more infertile part of the diagram. The poorest western communities do not overlap with the eastern plots, whereas plots belonging to similar types in the west and in the east are located close to each other. Separate ordinations of 203 vegetation plots located in Karelia and 506 vegetation plots located in the plain parts of the Komi Republic and in the mountain parts of the Komi Republic and Perm region show a good separation of plots into the distinct forest types which vary along ecological gradients of their own (Fig. 3.46). For the Karelian study areas (Fig.  3.46a), the main ecological gradients are soil reaction, nutrients, moisture, and light: correlations with the first axis amount to −0.9, −0.86, −0.53, and 0.48, respectively; and correlation with the second axis is 0.61 for soil moisture. For the eastern study areas (Fig. 3.46b), the main ecological gradients are the same, besides soil moisture, which is not well correlated with the ordination axes, and that can be explained by more evened average values of soil moisture in the eastern vegetation plots as compared to the western areas. Correlations of ecological values with the first axis amount to −0.95, −0.76, and −0.36 for soil reaction, nutrients, and light and with the second axis to −0.62 and

Fig. 3.45  DCA ordination of 709 vegetation plots sampled in old-growth Picea spp. (and Abies sibirica) forests located in the western (Karelia) and in the eastern (the Komi Republic and Perm region) study areas. Radiating lines show the direction and strength of the linear correlations of Ellenberg’s ecological values with the plot scores: N nutrients, R reaction, F moisture, and L light (Ellenberg et al. 1991). (a) Triangles are plots from the western and circles are plots from the eastern study areas. (b) Centroids of plots referred to the different forest types; “e” and “w” in the labels mean eastern and western forest types, respectively: e-NtTH nitrophilous tall herb Picea obovata-Abies sibirica (P.o.-A.s.) forests, e-BrTH boreal tall herb P.o.-A.s. forests located in plains, e-mBrTH boreal tall herb P.o.-A.s. forests located in mountains, e-LF large fern P.o.-A.s. forests, e-NmBr nemoral-boreal P.o.-A.s. forests, e-BrGM green moss – small boreal herb P.o.-A.s. forests, e-DwGM green moss  – dwarf shrub P.o. forests, e-GM pure green moss P.o. forests, w-NtTH nitrophilous tall herb Picea abies (P.a.) forests, w-BrTH boreal tall herb P.a. forests, w-BrGM green moss  – small boreal herb P.a. forests, w-DwGM green moss  – dwarf shrub P.a. forests, w-GM pure green moss P.a. forests

Fig. 3.46  DCA ordination of vegetation plots sampled in old-growth dark coniferous forests located in the western (a) and eastern (b) study areas. Radiating lines show the direction and strength of the linear correlations of Ellenberg’s ecological values with the plot scores (see Fig. 3.45). NtTH nitrophilous tall herb, BrTH plain boreal tall herb, mBrTH mountain boreal tall herb, LF large fern, NmBr nemoral-boreal, BrGM green moss – small boreal herb, DwGM green moss – dwarf shrub, and GM pure green moss forests

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0.48 for nutrients and light. In “the western diagram” (Fig. 3.46a), vegetation varies along the first ordination axis from the forest types on the richest soils dominated by boreal and nitrophilous tall herbs in the field layer to the green moss – dwarf shrubs and pure green moss forests on the poorest soils. The moistest soil is marked by nitrophilous tall herb forests and partly by pure green moss forests. For “the eastern plots” (Fig. 3.46b), vegetation generally varies along the first axis in a similar way from communities on the richest to those on the poorest soils, but the nutrient vector shifted compared to the reaction vector: plots on the richest soil are mostly in the mountain boreal tall herb forests. The second axis is correlated with light: on average, pure green moss and nitrophilous tall herb forests are the lightest. Below we consider each forest type more closely, starting with the richest communities, which are not widely distributed in the boreal forest region. Nitrophilous tall herb spruce and spruce-fir forests (Piceeta (P.-Abieta) nitrophilo-­magnoherbosa), section of boreal swamp forests. These forests are most commonly found in valleys of rivers and streams and can be called “riparian forests.” These forests have been found in all study areas. They occur either inside the dark coniferous forest massifs or within the other forests, usually inside Pinus sylvestris forests located on river terraces or adjacent slopes. In Karelia, this type is relatively rare. Most of the floodplains have high stony banks with steep slopes, and so the width of riparian Picea abies forests ranges from a few meters to a few tens of meters (Fig. 3.47). Very often there is a sharp boundary with neighboring forest communities which are usually green moss or lichen forests. In the eastern study areas (both on plains and mountains), riverine floodplains with linear fluvial levees and hollows are common, and nitrophilous tall herb spruce-fir forests often occupy well-drained areas (Fig. 3.48). These forests adjoin genuine swamp tall herb forests or sphagnum forests which occupy hardly drained areas. The width of riparian Picea obovata-­Abies sibirica forests is usually tens of meters but can reach hundreds of meters. On the western macro-slope of the Ural Mountains, nitrophilous tall herb spruce-fir forests occupy not only valleys of rivers and streams, but they also are found along narrow gullies with permanent or temporary water and in places where groundwater discharges. Piceeta (P.-Abieta) nitrophilo-magnoherbosa often occurs in plain parts of the Komi Republic, and it is entirely common on the western slopes of the Ural Mountains. In the studied riparian spruce and spruce-fir forests, crown cover varies, but usually light conditions are good especially owing to side lighting from the river. Betula pubescens co-dominates with Picea spp. in the overstorey; Abies sibirica occurs in half of the plots in the riparian forests located in the eastern areas. Alnus incana often occurs in the understorey, where Picea spp. dominates and Sorbus aucuparia, Salix caprea, Padus avium, and Abies sibirica (in the east) also occur. The shrub layer is poor in the west: only Salix phylicifolia and very rarely Juniperus communis were found there. In the east, the shrub layer is not dense, but relatively rich in species: not only boreal shrubs, such as Rosa acicularis, Lonicera altaica, and L. ­pallasii, but also nitrophilous species, such as Ribes nigrum, R. hispidulum, R. rubrum, and nemoral Spiraea media and Daphne mezereum, often occur.

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Fig. 3.47  Piceeta nitrophilo-magnoherbosa with Dryopteris cristata, Dryopteris filix-mas, Chamaenerion angustifolium, Rubus idaeus, Cirsium heterophyllum, Crepis paludosa, etc. in the Pyaozersk forestry unit, Karelia (Photo by M. Bobrovsky)

Fig. 3.48  Piceeto-Abieta nitrophilo-magnoherbosa with Angelica archangelica, Aconitum septentrionale, Stellaria nemorum, Veronica longifolia, Valeriana rossica, Calamagrostis langsdorffii, etc. in the mountain part of the Pechora-Ilych Reserve (Photo by M. Bobrovsky)

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The field layer is rich and the cover is high (80–100%). Dominant Filipendula ulmaria often defines the aspect of these forests. In the eastern study areas, nitrophilous and boreal tall herbs, such as Cacalia hastata, Urtica dioica, Senecio nemorensis, and Angelica archangelica, frequently occur. Common tall herbs, such as Aconitum septentrionale, Delphinium elatum, Cirsium oleraceum, Veratrum lobelianum, Chamaenerion angustifolium, and Geranium sylvaticum, are also abundant. In the western study areas, we found fewer species of tall herbs with less abundance in comparison with the eastern areas. Besides Filipendula ulmaria, Chamaenerion angustifolium and Geranium sylvaticum often occur; Cirsium heterophyllum occurs less frequently. However, the oligotrophic species Carex cinerea, C. globularis, C. loliacea, Comarum palustre, Rubus chamaemorus, Viola epipsila, etc. occur more often than in the eastern areas. In both areas, the small boreal herbs and ferns Trientalis europaea, Maianthemum bifolium, Gymnocarpium dryopteris, Phegopteris connectilis, and Oxalis acetosella (only in the east) occur very frequently with a high abundance. In the east, nemoral species, such as Aegopodium podagraria, Pulmonaria obscura, Milium effusum, Paris quadrifolia, Stellaria holostea, etc., and meadow species, such as Vicia sepium, V. cracca, Fragaria vesca, Alchemilla acutiloba, Lathyrus pratensis, Artemisia vulgaris, Poa pratensis, etc., were found in river valleys. In the Karelian plots, cover of the bottom layer is 70–90%; Pleurozium schreberi, Hylocomium splendens, and Polytrichum commune are common. In the eastern plots, cover of the bottom layer is less (40–60%), but the number of species is higher: Pleurozium schreberi, Sanionia uncinata, Rhytidiadelphus triquetrus, Hylocomium splendens, Rhodobryum roseum, and Plagiomnium ellipticum dominate. According to direct calculations, the nitrophilous tall herb forests have the highest vascular species richness (total number of species) of all forest types within the study regions (Fig. 3.49a, b). There are 9 tree, 5 shrub, and 81 herbaceous species in 34 plots located in the western riparian forests and 14 tree, 13 shrub, and 210 herbaceous species in 90 plots located in the eastern riparian forests. However, based on interpolation, there are no significant differences in vascular species richnesses calculated for the nitrophilous and for the plain boreal tall herb forests located in the western as well as in the eastern study areas: the unconditional confidence (95%) intervals for points on the species accumulation curves overlap for both pairs: e-NtTH and e-BrTH and w-NtTH and w-BrTH in Fig. 3.50. Thus, the highest vascular species richness in the studied regions is observed in the nitrophilous and in the plain boreal tall herb Picea spp. (Abies sibirica) forests as well. The interpolation estimates also show that vascular species richness of practically each forest type in the east is significantly higher than species richness of the corresponding forest type located in the west, and this is so for the nitrophilous and for the boreal tall herb forests. In number of vascular species per plot, the riparian forests fall behind the boreal tall herb forests in Karelia (Fig. 3.51a), and they are practically equal to the plain boreal tall herb forests in the eastern study areas (Fig. 3.51b). However, in the field layer, the gap between numbers of species per plot increases for the eastern riparian

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Fig. 3.49  Number of vascular species of different ecological-coenotic groups in the studied forest types in the western (a, c) and eastern (b, d) study areas. Forest types are the same as in Fig. 3.46. Ecological-coenotic groups: Pn piny species, Br small and medium boreal species, TH tall boreal herbs and ferns, Nm nemoral, Nt nitrophilous, Md meadow-edge, Wt water-marsh, and Olg oligotrophic plant species (see Sect. 2.2)

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Fig. 3.50  Interpolation estimates of species richness of the Picea spp.-Abies sibirica forest types in the study areas. Species accumulation curves and unconditional confidence (95%) intervals for the forest types are constructed according to Colwell et  al. (2012); no overlap of the intervals is a rough and conservative criterion of statistical differences in species richness for sample groups. Intervals correspond to a reference sample of 25 relevés (w-GM type). Forest types are the same as in Fig. 3.45. (*This is an extrapolation estimate, because only 16 relevés belong to the e-GM type)

forests: the average number of vascular species per plot in the field layer in the riparian forest (37.3) is less than this number calculated for the plain boreal tall herb forests (39.8) (Fig. 3.49d). It means that the tree and shrub layers are rather rich in the eastern riparian forests. The average number of vascular species per plot totals 30.2 (28.6 in the field layer) in the riparian Picea abies forests in Karelia and 41.5 in the riparian Picea obovata-Abies sibirica forests in the Komi Republic and Perm region. Tall boreal and nitrophilous herbs prevail in the cover of the field layer, whereas small and medium boreal herbs, ferns, and dwarf shrubs together form the largest species group (Fig. 3.49c, d). Proportion of the oligotrophic species is also quite high, especially in the western plots. On the whole, high species diversity in the riparian forests is mainly defined by rivers and streams which not only protect sites from fires but create a large variety of specific habitats, providing opportunities for the growth of many species. Linear

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Fig. 3.51  Boxplots of the numbers of vascular species per plot for the studied forest types in the western (a) and eastern (b) study areas. The midline is the median, the top and bottom of the box are the upper and lower quartiles, the whiskers are extended to the largest/smallest observation within 1.5 interquartile ranges of the top/bottom, and the circles denote observations beyond these limits. Forest types are the same as in Fig. 3.46

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fluvial levees are good moistened and well drained, often rich in nutrients, and as a result tall herbs and ferns dominate there and small boreal, nemoral, and nitrophilous plants also successfully grow. In the east, numerous meadow-edge species also grow in good light conditions on light soils in floodplains. Fluvial hollows, including oxbow lakes formed at different times, are the habitats for water-marsh and oligotrophic species. The high diversity of microsites created by rivers and streams, together with the pit-and-mound topography that developed in the absence of fire and cutting, owing to treefalls with uprooting, creates good possibilities for the coexistence of species with different ecological properties within the riparian dark coniferous forest. As a result, species of practically all ecological-coenotic groups are well presented in the community: the proportions of boreal, nemoral, nitrophilous, meadow, water-marsh, and oligotrophic species are very similar in the riparian Picea obovata-Abies sibirica forests located in the Komi Republic and in the Perm region (Fig. 3.49b, d). In the riparian Picea abies forests in Karelia, the proportions of nemoral and meadow species are clearly smaller compared to the eastern forests (Fig. 3.49a, c). It is worthwhile to note that the mosaic of microsites created by water is well developed in the riparian dark coniferous forests, whereas the mosaic caused by treefalls is far less so (examples of such mosaics are described in detail in Sect. 3.4). In the Karelian riparian forests, treefalls with uprooting are extremely rare. In the eastern areas, gap mosaics in the canopy and pit-and-mound topography often occur, but gaps and deadwood are often formed at about the same time and that may result from a removal of previous tree generations by cutting or fires. We observed a lot of deadwood at different stages of decay and erosion in the upper reaches of the Vashka River (No. 9 in Fig. 3.44), but the amount of “uneven-aged” deadwood was significantly less in the other riparian forests located in all other study areas. This can be explained by the high incidence of selective cutting along rivers and streams during the nineteenth and beginning of the twentieth centuries (see Sect. 3.2). Traces of old selective cuttings are widely distributed in the riparian dark coniferous forests, whereas traces of old fires in the vegetation (such as charred stumps, fire scars on the stems of Pinus sylvestris) are very rare or absent both in the western and the eastern study areas. The high water content in the dominant species, the absence of flammable litter, the good hydration throughout the season, and the presence of watercourses impede the emergence and spread of fires in riparian tall herb forests. Fluvisols with short soil profiles prevail in the riparian dark coniferous forests located in Karelia and in mountain areas of the Komi Republic and Perm region. In the riparian spruce-fir forests located on the plain part of the Komi Republic, Dystric Fluvisols with a great thickness of the soil profile prevail; different Histosols also often occur. Soil diversity is maximal there as compared with all other forest types. Sometimes pieces of charcoal can be found in the soil; they occur here and there or in clusters in mineral soil horizons in the material which has been raised on a root clump of a fallen tree and then fell into the pit formed after treefall with uprooting (Bobrovsky and Loyko 2016). In well-developed alluvial soils on plains in the Komi Republic, we met, in single profiles, up to four layers with charcoal inclusions in old pits formed by windfalls of different ages (Fig.  3.52). In floodplains of small

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Fig. 3.52  Soil profile (Dystric Fluvisol) with several layers of charcoal which have been transported with soil organic matter into pits formed by treefalls at different times in the Piceeto-Abieta nitrophilo-magnoherbosa located in the plain part of the Komi Republic (The photo was taken in a floodplain of the Vashka River tributary by M. Bobrovsky)

streams, single pieces of charcoal or coal layers are common at the boundary of organic (litter or peat) and mineral soil horizons. We think that the charcoal in soils in the riparian tall herb forests is mainly the result of rare crown fires which came from the adjacent slopes. We would like to emphasize that one of the main features of the soil in tall herb forests is the presence of earthworms; this is very remarkable for areas located in the northern taiga, as they are usually devoid of earthworms. In Karelia, in riparian forests dominated by Picea abies and located near Kostomuksha, 36–50 individuals of earthworms per square meter were found (Rybalov 2006). In the riparian Picea obovata-Abies sibirica forests in the Pechora-Ilych Nature Reserve, the average number of earthworms was 25 ind./m2 (Shashkov and Bobrovsky 2008). Boreal tall herb spruce and spruce-fir forests (Piceeta (P.-Abieta) magnoherbosa), section of boreal tall herb forests. We have said above that the forests of this section located in the study areas were classified into the three forest types: (i) boreal tall herb Picea abies forests in the western study areas, (ii) boreal tall herb Picea obovata-­Abies sibirica forests located in the plain parts of the Komi Republic, and (iii) mountain boreal tall herb Picea obovata-Abies sibirica forests located on the western macro-slope of the Ural Mountains and studied in the Komi Republic and in the Perm region (w-BrTH, e-BrTH, e-mBrTH in Fig. 3.45b, respectively). All these

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Fig. 3.53  A gap in the canopy of Piceeta magnoherbosa with Chamaenerion angustifolium, Phegopteris connectilis, Geum rivale, Equisetum sylvaticum, Linnaea borealis, Lerchenfeldia flexuosa, Maianthemum bifolium, Vaccinium myrtillus, and others in the pit and mound formed by treefall with uprooting in the Pyaozersk forestry unit, Karelia (Photo by M. Bobrovsky)

forests are located on watersheds or slopes, and they differ from forests of the other sections in the dominance of mesophilous boreal tall herbs in the ground layer. Of all study areas, they are most common in the Pechora-Ilych State Nature Reserve. In Karelia, boreal tall herb Picea abies forests occur in the northern taiga, in the western part of the Pyaozersk forestry unit to the north of Lake Paanayarvi (No. 2 in Fig. 3.44). The area where these forests occur is surrounded by a large number of lakes, marshes, and streams. It adjoins the boundary with Finland, and for much of the twentieth century, these sites were included into “the border zone” and local people were not permitted to enter them. Boreal tall herb Picea abies forests are mainly found in small patches ranging from tenths of a hectare to one hectare. Only a few larger areas have been found. These forests basically occupy the middle and lower parts of the slopes, sometimes drained runoff hollows and rocky slopes. There are no traces of fires and selective cutting in these forests; there is a lot of deadwood at different stages of decay, and there are canopy gaps formed by treefalls of different ages (Fig. 3.53). These forests are surrounded by Picea abies or Pinus sylvestris forests belonging to the green moss section. Often forests of the boreal tall herb and green moss sections (green moss – dwarf shrub, green moss – small boreal herb subsections) occupy different slopes of the same ravines or even different parts of one single slope separated by

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Fig. 3.54  Piceeta magnoherbosa with Geranium sylvaticum, Phegopteris connectilis, Maianthemum bifolium, Vaccinium myrtillus, Luzula pilosa, Pulmonaria obscura, and immature individuals of Sorbus aucuparia in the Pyaozersk forestry unit, Karelia (Photo by M. Bobrovsky)

hollows or rarely rocks, and these forests differ, first of all, by the absence or presence of fire traces. The stands are sparse in the boreal tall herb Picea abies forests; crown cover is 20–40%. Picea abies dominates; Betula pubescens usually occurs. These tree species prevail in the undergrowth where Sorbus aucuparia, Alnus incana, and Salix caprea often occur. Cover of the understorey widely varies: from 20 to 80%. The shrubs Ribes spicatum, R. glabellum, and Salix phylicifolia also often occur in the understorey. Cover of the field layer is 70–100%. The tall mesophilous herbs Cicerbita alpina and Geranium sylvaticum, together with the small boreal ferns Gymnocarpium dryopteris and Phegopteris connectilis, often dominate in the Karelian boreal tall herb Picea abies forests (Fig.  3.54). Boreal and nitrophilous tall herbs and ferns (Chamaenerion angustifolium, Geum rivale, Filipendula ulmaria, and Athyrium filix-femina), small boreal herbs, and dwarf shrubs (Maianthemum bifolium, Trientalis europaea, Orthilia secunda, Linnaea borealis, Solidago virgaurea, Equisetum sylvaticum, Rubus saxatilis, Lycopodium annotinum, Vaccinium myrtillus, and V. vitis-idaea) together with nemoral and boreal grasses (Milium effusum, Melica nutans, and Avenella flexuosa) occupy more than 75% of the plots. The tall herbs Cirsium heterophyllum, Crepis paludosa, Rubus idaeus, Calamagrostis phragmitoides, Angelica sylvestris, Actaea erythrocarpa, Trollius europaeus, Geranium albiflorum, Crepis praemorsa, and the tall fern Diplazium sibiricum were

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found with less frequency. Nemoral herbs such as Paris quadrifolia, Actaea spicata, Vicia sylvatica, etc. and the nemoral fern Dryopteris carthusiana also occur in the northern Karelian tall herb Picea abies forests. Among the nemoral plants, there is a high proportion of grasses: besides the already mentioned Milium effusum and Melica nutans, Poa nemoralis and Elymus caninus often occur. Conspicuously, nemoral species occur frequently in plots of this forest type, whereas only single specimens of nemoral species can be found in other types of Picea abies forests in Karelia. There is a high diversity of mosses in all boreal tall herb dark coniferous forests. In the Karelian tall herb forests, the moss cover averages 41%; Hylocomium splendens, Pleurozium schreberi, Rhytidiadelphus triquetrus, R. subpinnatus, Polytrichum commune, Ptilium crista-castrensis, and Mnium spp. are common. As mentioned above, vascular species richness is similar in the boreal and nitrophilous tall herb Picea abies forests (Figs. 3.49a and 3.50), whereas the number of vascular species per plot in the boreal tall herb forests is higher than in the riparian dark coniferous forests in Karelia (Figs. 3.49c and 3.51a). This may be a consequence of a very high similarity in species composition in different plots in the boreal tall herb Picea abies forests which leads to a large number of species with a high frequency and does not increase the total species diversity (species richness). In the Karelian boreal tall herb forests, the proportions of boreal, nemoral, and nitrophilous species are higher and the oligotrophic and water-marsh species lower as compared to the riparian Karelian forests (Fig. 3.49a, c). Plain boreal tall herb Picea obovata-Abies sibirica forests are found on different relief positions in all study areas located in the plain part of the Komi Republic. In the watershed between the Mezen and Vashka rivers, in the upper reaches of the Vashka River, and on the Middle Timan Ridge (Nos. 8, 9, and 11  in Fig.  3.44, respectively), boreal tall herb spruce-fir forests have been found in drained hollows often located in the lower parts and sometimes in the middle parts of quite steep slopes. These forests often adjoin forests of the green moss or sphagnum sections. In the upper reaches of the Sedka and Suran rivers (No. 10 in Fig. 3.44), the boreal tall herb spruce-fir forests are found on gentle slopes and watersheds. They are usually surrounded by forests of the green moss – dwarf shrub and green moss – small boreal herb subsections; sometimes they border on the riparian tall herb spruce-fir forests. Areas covered by the boreal tall herb Picea obovata-Abies sibirica forests located in the plain part of the Komi Republic greatly vary: from hundredths of a hectare to tens of hectares. The stands are usually sparse; gap mosaics in the canopy are well developed. Picea obovata dominates in the overstorey; Betula pubescens also often occurs. Abies sibirica occurs less frequently than in the other tall herb forests. Pinus sibirica occurs sporadically. Undergrowth of Picea obovata dominates. Betula pubescens, Alnus incana, Abies sibirica, Salix caprea, and Sorbus aucuparia often occur in the understorey. Cover of the shrub layer is 10–30%, but the diversity of shrubs is high. Rosa acicularis dominates, Juniperus communis, Spiraea media, and species of the genus Lonicera (L. altaica, L. pallasii, and L. xylosteum) often occur. Species of the

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Fig. 3.55  Piceeto-Abieta magnoherbosa with Athyrium filix-femina, Calamagrostis arundinacea, Chamaenerion angustifolium, Filipendula ulmaria, Rubus idaeus, etc. in the plain part of the Komi Republic (Photo by N. Alatyrtseva)

genus Ribes (R. hispidulum, R. rubrum, and R. nigrum), Daphne mezereum, Salix phylicifolia, etc. were also found. The composition of the field layer in the boreal tall herb spruce-fir forests located in a plain part of the Komi Republic is similar to that in the nitrophilous tall herb and nemoral-boreal Picea obovata-Abies sibirica forests located in the eastern study areas (Fig.  3.55), whereas dominants are rather similar to the dominants in the boreal tall herb Picea abies forests located in the west. There are a small number of dominants with a high frequency in the plain boreal tall herb forests, including Aconitum septentrionale, Filipendula ulmaria, Gymnocarpium dryopteris, Rubus saxatilis, and Trientalis europaea. Many species which are not encountered in other tall herb forests occur sporadically in this forest type. The tall herbs Chamaenerion angustifolium, Geranium sylvaticum, Geum rivale, Calamagrostis canescens, etc. and the boreal small herbs and dwarf shrubs Vaccinium myrtillus, V. vitis-idaea, Linnaea borealis, Equisetum sylvaticum, Oxalis acetosella, Maianthemum bifolium, Luzula pilosa, Orthilia secunda, etc. were found in most of the plots. In the total list of species, the proportion of meadow-edge plants, such as Vicia sepium, Fragaria vesca, Geranium pratense, Lathyrus pratensis, etc., and water-swamp species, such as Calamagrostis canescens, Equisetum palustre, Bistorta major, Caltha palustris, Veronica longifolia, Carex cespitosa, Equisetum scirpoides, Parnassia palustris, etc., is quite high, and it is similar to the proportion of these species in the riparian forests located in the eastern study areas (Fig. 3.49b). The number of oligo-

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trophic species is even higher than that in the riparian forests, including Viola epipsila, Carex globularis, C. loliacea, C. disperma, Rubus chamaemorus, Comarum palustre, and Epilobium palustre. However in general, meadow-edge, water-marsh, and oligotrophic species are rare in the plain boreal tall herb spruce-fir forests. Mountain boreal tall herb Picea obovata-Abies sibirica forests located on the western macro-slope of the Ural Mountains were described from the Pechora-Ilych State Nature Reserve and the Vishera State Nature Reserve (Nos. 12 and 13  in Fig. 3.44, respectively). In the Vishera Reserve, these forests are most often found on the upper slopes. They often occur on steep slopes and at the upper limit of dark coniferous forests, near the border with crooked birch forest or mountain tundra. As in Karelia, sites on the slopes occupied by the tall herb spruce-fir forests are often bounded by streams or rocky areas. The extent of such sites is usually from hundredths to several hectares. In the Pechora-Ilych Reserve, boreal tall herb spruce-fir forests are common on lower, drained parts of slopes adjacent to river valleys, mainly valleys of the Pechora River and its right tributary, the Bolshoy Shezhym River (Figs.  3.23 and 3.26). Sometimes, these forests can be found on local elevations and on upper and middle parts of slopes in places of drained, stony hollows. In the higher parts of the Ural Mountains, these forests often occupy upper and middle parts of slopes. As in the Vishera Reserve, these forests are found at the upper limit of dark coniferous forests, bordering on subalpine meadows, crooked birch forests, or mountain tundra. On the whole, the boreal tall herb Picea obovata-Abies sibirica forests are common in the Pechora-Ilych Reserve, and their areas vary from tenths to hundreds of hectares. Cover of the overstorey in the mountain boreal tall herb dark coniferous forests is usually low. Picea obovata and Abies sibirica prevail in equal proportion; Betula pubescens is common. Abies sibirica reaches its highest frequency of all tall herb forests here. Pinus sibirica often occurs in the overstorey which is typical of the mountain spruce-fir forests. In the undergrowth Picea obovata and Abies sibirica dominate, but Pinus sibirica, Betula pubescens, and Sorbus aucuparia also often occur. The shrub layer is rich in species: Rosa acicularis is common; Spiraea media, Lonicera altaica, L. pallasii, Ribes hispidulum, R. rubrum, Daphne mezereum, Padus avium, etc. occur. As in the boreal tall herb Picea abies forests in Karelia, there are many dominants with a high frequency in the field layer. There are mesophilous tall herbs, small boreal herbs, and ferns and nemoral herbs among the frequent dominants. Besides Aconitum septentrionale, there are the tall herbs Cirsium heterophyllum, Calamagrostis langsdorffii, and Geranium albiflorum which do not dominate in the other tall herb forests. Also unlike the other tall herb forests, the tall fern Dryopteris dilatata often co-dominates the field layer in the mountain boreal tall herb forests. The tall herbs Delphinium elatum, Paeonia anomala, Cacalia hastata, and Crepis praemorsa together with the tall fern Diplazium sibiricum are common and are a peculiarity of the mountain forests. The tall herbs Veratrum lobelianum, Chamaenerion angustifolium, Rubus idaeus, Geranium sylvaticum, Valeriana officinalis, Crepis sibirica, C. paludosa, Cirsium oleraceum, Thalictrum minus,

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T. aquilegifolium, Angelica sylvestris, Trollius europaeus, etc. often occur with low abundance and are typical for all other tall herb forests. The tall fern Athyrium distentifolium is common only in the mountain tall herb forests; sometimes this species dominates the field layer in the upper part of the forest belt, near the border with mountain tundra. Among small boreal ferns and herbs, Gymnocarpium dryopteris, Phegopteris connectilis, Equisetum sylvaticum, and Oxalis acetosella often occur with high abundance; Trientalis europaea and Linnaea borealis also often occur. The number of nemoral plants is less in the mountain tall herb forests compared to the nitrophilous tall herb Picea obovata-Abies sibirica forests, but unlike the other types of tall herb forests, nemoral herbs such as Milium effusum and Stellaria holostea often occur with high abundance. In this, the mountain tall herb forests are similar to the nemoral-boreal spruce-fir forests (Fig. 3.45b). The nemoral species Paris quadrifolia is common; Lathyrus vernus and Melica nutans often occur. In contrast with the other tall herb forests in the east, the number and abundance of meadow, water-swamp, and oligotrophic species are much smaller. As mentioned above, a high diversity of mosses occurs in all boreal tall herb dark coniferous forests. In the plain spruce-fir forests, the cover of mosses averages 73%; Pleurozium schreberi, Hylocomium splendens, Rhytidiadelphus triquetrus, and Sphagnum warnstorfii dominate. In the mountain tall herb forests, the cover of mosses averages 45% and has the highest number of species with a high frequency. Pleurozium schreberi and Brachythecium reflexum dominate; Hylocomium splendens, Barbilophozia lycopodioides, Dicranum fuscescens, D. scoparium, Rhytidiadelphus subpinnatus, Brachythecium oedipodium, Mnium spinosum, Sanionia uncinata, and Rhodobryum roseum are common. Eight tree, 6 shrub, and 83 herbaceous species occurred in 35 sample plots located in the boreal tall herb Picea abies forests in Karelia. Thirty-two sample plots located in the plain boreal tall herb Picea obovata-Abies sibirica forests have 11 tree, 15 shrub, and 146 herbaceous species, being less than in the eastern ­nitrophilous tall herb forests but more than in the Karelian tall herb forests. Species richness in the mountain boreal tall herb forests is markedly lower than in the plain boreal tall herb forests: in 118 plots we recorded 9 tree, 12 shrub, and 134 herbaceous species. The interpolation estimates that (1) species richness in the east is higher than in the west, (2) within each region species richness in the nitrophilous and plain boreal tall herb forests differs little, and (3) species richness of the mountain forests in the east is lower than that in the eastern plain boreal tall herb forests but higher than in the tall herb forests located in the west (Fig. 3.50). The number of vascular species per plot averages 35.0 in the Karelian boreal tall herb forests, 42.8 in the eastern plain, and 34.6 in the eastern mountain boreal tall herb forests (Fig. 3.51); in the field layer, the average number of species per plot in the Karelian forests is even higher than in the eastern mountain forests: 33.4 against 30.4 species (Fig. 3.49c, d). Thus, vascular species diversity calculated per plot in the western boreal tall herb Picea abies forests is high and practically equal to that in the eastern boreal tall herb Picea obovata-Abies sibirica forests. We consider this a very important finding. It demonstrates the potential of boreal forest ecosystems to maintain a high level of species diversity in the absence of fires and cutting

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(Smirnova et al. 2006). The long-term development of the forests on watersheds and slopes leads to the formation of various microsites, some of which are ecologically equivalent to those in the riparian forests (e.g., deep waterlogged depressions and pits formed after treefalls with uprooting). A significant number of the microsites are also associated with deadwood: wood at various stages of decomposition provides a wide variety of substrates for plants (Aleynikov and Bovkunov 2011; Lugovaya et al. 2013). We conclude that the investigated boreal tall herb dark coniferous forests have been developed for a long time without fires and cutting because there are no traces of these events in the vegetation: there are no Pinus spp. in the stands in Karelia and in the plain part of the Komi Republic; Pinus sibirica often occurs in the mountain tall herb forests, but there are no fire scars on the trees. Charcoal has not been found in the soils in the Karelian boreal tall herb Picea abies forests, although it occurs abundantly in the soils in the adjacent forests of the green moss section. We have occasionally found charcoal in the soils in the eastern boreal tall herb spruce-fir forests, but it was very rare compared to the charcoal finds in all other forest types. On the whole, the soils in the boreal tall herb spruce(-fir) forests are distinguished by their well-expressed mosaic structure which is formed as a result of numerous treefalls with uprooting. Entic Podzols (“podbur” in Russian) prevail in the boreal tall herb Picea abies forest situated in the Pyaozersk forestry unit in Karelia (Fig.  3.56a); their structure closely resembles the Dystric Cambisols (raw-humic brown soils) (Lukina et  al. 2008; Bobrovsky 2010). The Bhs horizon (spodic) is brown, well structured, and drained, mainly 20 to 60 cm thick. Gravelly sandy sediments occur deeper. Histosols with a H horizon (histic) of up to 50 cm thick prevail in wet depressions.

Fig. 3.56  Soil profiles in the Piceeta (P.-Abieta) magnoherbosa. (a) Entic Podzol in the Pyaozersk forestry unit (Karelia) and (b) Dystric Cambisol in the mountain part of the Pechora-Ilych Reserve (Photos by M. Bobrovsky)

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Different soils occur in the boreal tall herb spruce-fir forests situated in the plain part of the Komi Republic. Combinations of Haplic and Entic Podzols prevail in the upper reaches of the Vashka River and on the Timan Ridge; Histosols and Gleysols occur in depressions. The thickness of the litter layer in Podzols is 5–10 cm; the E horizon is about 10 cm thick; the Ah or H horizons in peaty soils reach up to 50 cm thick. Haplic Albeluvisols prevail in the south of the Komi Republic; soils with buried moder or mull humus horizons often occur. The Albic horizon is 15–25 cm thick. Dystric Cambisols and Histosols also occur. Dystric Cambisols occupy a considerable area in the mountain boreal tall herb spruce-fir forests (Fig.  3.56b); Eutric Cambisols often occur; Cambic Umbrisols occur on the acid rocks. The Ah and A horizons average 28 cm in thickness, with a maximum of 40 cm; the Bw horizon is on average 25 cm thick. Cambisols adjoin with areas of Haplic and Entic Podzols; the E horizon reaches up to 5 cm thick and the Bhs horizon up to 20–25 cm. Histosols and Gleysols often occur in depressions and pits formed after treefalls with uprooting; the Ah or H horizons are on average 30 cm thick. In the plain and mountain parts of the Komi Republic, large accumulations or layers of charcoal rarely occur in the litter or in the histic horizon in Cambisols, Umbrisols, and Histosols in the tall herb spruce-fir forests located on the lower parts of slopes, where there is a thick layer of loamy deposits. We think that the charcoal has been carried here by surface flow after fires on upslope sites. Generally, the occurrence of charcoal in Cambisols is extremely rare. In all other cases, as in some Cambisols and Podzols, Albeluvisols, etc., charcoal pieces have been found inside the soil profile, in A or B horizons, where they were deposited with soil material as a result of treefalls with uprooting. This testifies that it occurred in more distant times and that fires were rare, as otherwise the charcoal would have been found in the litter or on the border of litter and the mineral soil. As mentioned above, one of the remarkable features of the soils in tall herb forests is the presence of earthworms. In Picea abies forests located in the Paanajarvi National Park (Karelia) 20 ind./m2 have been found (Rybalov 2006). The number of earthworms in soils in the boreal tall herb spruce-fir forests located in the Komi Republic varies from 15 to 80 ind./m2, and worms occur to a considerable depth (Shashkov and Bobrovsky 2008; Shashkov and Kamaev 2010). Rich litter and earthworm activity determine the development of Eutric Cambisols with a mull humus horizon in these forests. Fires hinder this process. Large fern spruce-fir forests (Piceeto-Abieta magnofilicosum) (Fig. 3.29), section of large fern forests, were described only from the eastern study areas. In the plain part of the Komi Republic, these forests are usually small in size, and it is difficult to determine the patterns of their distribution there. These forests occupy small areas on slopes of varying steepness; they are surrounded by Picea obovata-­ Abies sibirica forests of the green moss section and green moss – dwarf shrub and green moss – small boreal herb subsections. They were found in the upper reaches of the Sedka and Suran rivers and on the Timan Ridge (numbers 10 and 11  in Fig. 3.44, respectively). On the western macro-slope of the Ural Mountains, these forests occupy considerable areas, from a hectare to hundreds of hectares. In foot-

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hills situated in the Pechora-Ilych Reserve, large fern spruce-fir forests occupy areas with a good drainage; they are common on upper slopes and on watersheds. These forests cover long-stretched areas of several kilometers as in the area between the Bolshoy Shezhym and Bolshaya Porozhnaya rivers (see Fig. 3.21 as an example). These forests are also common on the slopes of the Ural Mountains: they were found on the western slopes of mounts Medvezhya and Yanypupuner, where the length of large fern forests is hundreds of meters. Tree stand density is usually medium (0.5–0.6). Picea obovata and Abies sibirica dominate in equal proportion. Betula pubescens and Pinus sibirica usually occur. There are fire scars on stems of Pinus sibirica; individuals with scars are up to 400 years old. Pit-and-mound topography and gap mosaics in the canopy are usually well developed. Large gaps in the canopy are common. They often look like fern wastelands in the absence of undergrowth and shrubs. Cover of the understorey is generally low; the shrub layer is poor; Sorbus aucuparia, Rosa acicularis, and Lonicera pallasii can occur. The large fern Dryopteris dilatata dominates in the field layer with a cover of up to 80–100%. The small boreal herbs and ferns Gymnocarpium dryopteris, Phegopteris connectilis, Oxalis acetosella, Maianthemum bifolium, and Trientalis europaea often co-dominate. The boreal dwarf shrub Vaccinium myrtillus and the evergreen creeper Linnaea borealis often occur with low abundance; these species grow on slightly decayed deadwood as well as on soil, under the large ferns. The tall herbs Rubus idaeus, Chamaenerion angustifolium, Veratrum lobelianum, and rarer Diplazium sibiricum, Aconitum septentrionale, Geranium sylvaticum, and Cinna latifolia also occur. Nemoral species are very rare: only Milium effusum, Stellaria holostea, and Paris quadrifolia were sporadically found. Nitrophilous species such as Calamagrostis langsdorffii may occur occasionally. Meadow-edge, water-marsh, and oligotrophic species are practically absent. Cover of the bottom layer averages 30–40%. Pleurozium schreberi dominates; Dicranum fuscescens, D. scoparium, Brachythecium reflexum, Hylocomium ­splendens, Plagiothecium denticulatum, and Polytrichum commune often occur. The mosses do not cover much of the soil but mainly occupy deadwood at different stages of decay. In their floristic composition, these forests generally closely resemble the mountain tall herb spruce-fir forests (Figs. 3.45 and 3.46b), but species diversity is almost two times lower in the large fern forests than in the tall herb forests (Figs. 3.49 and 3.51). We recorded 9 tree, 5 shrub, and 79 herbaceous species in 75 sample plots. According to the interpolation, vascular species richness in these forests is significantly lower than in the eastern and western tall herb forests, and there is no significant difference with forests of the green moss section (Fig. 3.50). The number of vascular species per plot averages 22.8 in total and 18.6 in the field layer. Albeluvisols with an E horizon of 10–20 cm thick prevail in the large fern spruce-­ fir forests situated in the plain part of the Komi Republic. Al-Fe-humus Podzols and other Al-Fe-humus soils resembling dwarf Entic Podzols, all with a short soil profile, prevail in the large fern spruce-fir forests located in the mountains. On the

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Fig. 3.57  Rounded and large lamellar pieces of charcoal at the surface of the mineral soil (under the litter) in the Piceeto-Abieta magnofilicosum (Photo by M. Bobrovsky)

whole, strongly eroded soils on drained sites are common in the large fern Picea obovata-Abies sibirica forests. Charcoal in the soil is common, as are fire scars on stems of Pinus sibirica, and testifies to fires in the past. Charcoal pieces are lamellar, mainly small, as well as rounded with diameters of less than 2 mm; they occur singly or in clusters usually on the border of litter and the mineral soil or in the upper part of the mineral soil (Fig. 3.57). The shape and location of the charcoal allow us to determine the time since and the frequency of fires in the past (Bobrovsky 2010). The presence of charcoal under the litter or in the upper part of the mineral soil means that the coal formed during the fire was covered by the organic litter only and that it was not transported to the deeper layers of the soil as happens during treefalls with uprooting. Lamellar coal usually is formed during the fire. Over time, charcoal pieces gradually decrease in size and become rounded as a result of their long sojourn on the surface, where they are broken or grinded by the mineral particles of the soil during rainfall. The accumulation of rounded pieces of coal is usually confined to micro-depressions as a result of the transfer of the coal pieces by surface flow. All this testifies to intense fires in the past and a slow recovery of vegetation after the fires in the areas where the large fern spruce-fir forests presently are situated. Nemoral-boreal spruce-fir forests (Piceeto-Abieta nemoralo-borealiherbosa), section of green moss forests. These forests were described only from the eastern study areas and only from the south of the plain part of the Komi Republic (No. 10 in Fig. 3.44). Picea obovata-Abies sibirica forests co-dominated by nemoral and small boreal herbs in the ground layer occur at different relief positions, mainly on the lower part of gentle slopes. Tree stands are sparse; crown cover is 30–40%. There are large gaps in the canopy caused by recent treefalls: we noticed that practically all fallen large trees were

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Fig. 3.58 Gap with young individuals of Tilia cordata in the Piceeto-Abieta nemoralo-­ borealiherbosa in the south of the plain part of the Komi Republic (Photo by M. Bobrovsky)

in their initial stage of decay, and there was no old deadwood at late stages of decay in these forests. Trees fall mainly with uprooting and in groups rather than singly. In the overstorey, Picea obovata dominates more frequently than Abies sibirica; in the undergrowth both these species dominate. Betula pubescens and B. pendula are common in the overstorey. Populus tremula often occurs, a fact that we did not observe in the other types of dark coniferous forests. Tilia cordata occurs sporadically in the overstorey and in the undergrowth as well (Fig. 3.58). Pinus sibirica and P. sylvestris rarely occur in the stands; we did not find fire scars on their stems. The cover of the understorey varies; frequently it is 30–40%. The understorey is rich in species: Sorbus aucuparia and Rosa acicularis dominate; Lonicera altaica, L. xylosteum, Padus avium, and Ribes hispidulum are common; R. rubrum, R. nigrum, and Daphne mezereum occur. Cover of the field layer is 80–100%. Boreal and nemoral plants of middle and small size dominate in the ground layer and define the aspect of these forests (Fig. 3.59). Tall herbs also occur in small patches, but they do not form a separate layer. Aegopodium podagraria, Ranunculus cassubicus, Gymnocarpium dryopteris, Equisetum sylvaticum, Calamagrostis arundinacea, Pulmonaria obscura, Aconitum septentrionale, Dryopteris dilatata, etc. often occur with high abundance. The nemoral herbs and grasses Stellaria holostea, Paris quadrifolia, Milium effusum, and Melica nutans also often occur with less abundance. Cover of the bottom layer is no more than 10–20%. Pleurozium schreberi, Hylocomium splendens, and Rhytidiadelphus triquetrus dominate. Sanionia unci-

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Fig. 3.59  Piceeto-Abieta nemoralo-borealiherbosa with Ranunculus cassubicus, Pulmonaria obscura, Trollius europaeus, Geranium sylvaticum, Milium effusum, etc. in the south of the plain part of the Komi Republic (Photo by M. Bobrovsky)

nata and Dicranum scoparium are common. Plagiomnium medium, Dicranum polysetum, Ptilium crista-castrensis, Brachythecium starkei, etc. occur. In floristic composition, the investigated nemoral-boreal Picea obovata-Abies sibirica forests generally closely resemble all variants of the eastern tall herb spruce-­ fir forests, including the nitrophilous and boreal plain and mountain variants (Figs. 3.45b and 3.46b). These forests also are similar to the eastern tall herb forests as regards their vascular species diversity. We recorded 11 tree species, 12 shrub species, and 115 herbaceous species in 55 sample plots which is somewhat less than in the eastern tall herb forest types (Fig. 3.49b), but based on the interpolation, there is no significant difference in species richness between nemoral-boreal and mountain boreal tall herb forests (Fig. 3.50); but species richness was significantly higher in these forests than in all other forests of the green moss section and in all western forest types. The number of vascular species per plot is also high in the nemoral-­ boreal spruce-fir forests: it averages 39.4 in total and 33.8 in the field layer which is similar to that in the eastern tall herb forests and almost twice as high than in other forests of the green moss section (Figs. 3.49b and 3.51). Albeluvisols with an E horizon of 7–15 cm thick are common. Albeluvisols with a second humic horizon have been found in the south of the Komi Republic. Ordinary lamellar or rounded charcoal pieces are common in the soil; they mainly occur in the mineral soil. Earthworms also often occur in the nemoral-boreal Picea obovata-Abies sibirica forests.

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Green moss  – small boreal herb spruce(-fir) forests (Piceeta (P.-Abieta) parviherboso-­hylocomiosa), section of green moss forests, are widely distributed in the boreal region. They occur on the middle and lower parts of slopes and river ­terraces. In the studied areas located within the intact forest landscapes, these forests occur much more widely in Karelia than in the Komi Republic and Perm region. Cover of the overstorey is 30–40%. In the Karelian green moss – small boreal herb dark coniferous forests, Picea abies dominates; Betula pubescens and B. pendula are relatively frequent. Pinus sylvestris and Salix caprea occur. The undergrowth consists of Picea abies and Betula spp.; Salix caprea, Sorbus aucuparia, Alnus incana, and Populus tremula also often occur. In the Komi Republic, Picea obovata and Abies sibirica co-dominate; Pinus sibirica and Betula pubescens are common; the undergrowth consists of Picea obovata, Abies sibirica, and Pinus sibirica. Fire scars on stems of Pinus spp. sometimes occur in the western as well as in the eastern forests. For some trees in the east, we could determine the ages of fire scars: trees were inflicted 150–340 years ago. The cover of the understorey is not high, 20–30%. In the Karelian forests, the shrub layer is richest in species of all investigated forest types and consists of Juniperus communis, Ribes glabellum, R. spicatum, etc. In the Komi Republic, Sorbus aucuparia, Rosa acicularis, and Lonicera pallasii often occur in the understorey. Cover of the field layer is 70–90%. Small and medium boreal herbaceous species absolutely dominate in the field layer, and vascular species of all other ecological-­ coenotic groups are present in equal proportions (Fig. 3.49). The studied green moss – small boreal herb dark coniferous forests located in the west are very similar to those in the east: the same species dominate or are frequent, and values of species diversity are similar as well (Figs.  3.60 and 3.61). The small boreal herbs and ferns Gymnocarpium dryopteris, Maianthemum bifolium, and Oxalis acetosella (only in the east) dominate together with the boreal dwarf shrub Vaccinium myrtillus. Trientalis europaea, Linnaea borealis, Lycopodium annotinum, and Luzula pilosa often occur with less abundance. The tall herbs Geranium sylvaticum and Chamaenerion angustifolium and the large fern Dryopteris dilatata (only in the east) also occur. Cover of the bottom layer is 70–90%; Pleurozium schreberi and Hylocomium splendens dominate. Dicranum scoparium and Polytrichum commune are common in Karelia; Polytrichum commune, Ptilium crista-castrensis, Dicranum fuscescens, D. spadiceum, and Barbilophozia lycopodioides often occur in the Komi Republic and Perm region. We recorded 8 tree, 9 shrub, and 56 herbaceous species in 39 sample plots situated in the Karelian green moss – small boreal herb Picea abies forests. In 45 sample plots situated in the eastern green moss – small boreal herb Picea obovata-Abies sibirica forests, we recorded 6 tree, 4 shrub, and 72 herbaceous species. Based on the interpolation, these forests in the east and in the west, as well as the investigated large fern spruce-fir forests, do not significantly differ in species richness (Fig. 3.50). In number of vascular species per plot, the Karelian green moss – small boreal herb Picea abies forests even surpass the similar eastern forests, with a total of 24.8 in the western as against 23.8 in the eastern study areas and 22.6 and 19.2 in the field

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Fig. 3.60  Piceeta parviherboso-hylocomiosa with Gymnocarpium dryopteris, Solidago virgaurea, Maianthemum bifolium, Trientalis europaea, and Vaccinium myrtillus in Karelia (Photo by M. Bobrovsky)

Fig. 3.61  Piceeto-Abieta parviherboso-hylocomiosa with Gymnocarpium dryopteris, Rubus idaeus, Vaccinium myrtillus, and others in the mountain part of the Komi Republic (Photo by M. Bobrovsky)

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layer, respectively (Figs. 3.49c, d and 3.51); all these values are considerably lower than those calculated for the tall herb and nemoral-boreal spruce(-fir) forests. Podzols are common soils of these forests in the west as well as the east. Haplic Podzols with an E horizon of 20 cm thick prevail. Charcoal usually occurs on the border of litter and the mineral soil and in the E horizon as well; it means that there were no substantial perturbations of the soil, such as soil throw by treefall with uprooting, after the last fires. It is important to note that there are variants of the green moss – small boreal herb Picea obovata-Abies sibirica forests in which the tall herbs Aconitum septentrionale, Cirsium heterophyllum, Rubus idaeus, etc. occur with low abundance. In the absence of fire and cutting and in the presence of gaps in the forest canopy providing sufficient light, the tall herbs gain an advantage and start to dominate, and a transition from the boreal small herb to the boreal tall herb forests can be observed. In Karelia, only Geranium sylvaticum and Chamaenerion angustifolium occur; further enrichment of the community by tall herbs is difficult owing to the small and discontinuous areas tall herb forests occupy in the west. The same situation is observed in most of the boreal forest regions. However, in the studied areas located within the intact forest landscapes, tall herb forests relatively often occur, for example, in the Pechora-Ilych State Nature Reserve, they occupy large areas. Consequently, there are fewer obstacles in the eastern areas to change from the green moss – small boreal herb spruce(-fir) forests to the forests dominated by tall herbs in the field layer (see Sect. 3.4). Green moss – dwarf shrub spruce(-fir) forests (Piceeta (P.-Abieta) fruticuloso-­ hylocomiosa), section of green moss forests, prevail in between Picea abies forests in Karelia, where they occupy different relief positions (Fig. 3.62). Green moss – dwarf shrub Picea obovata-Abies sibirica forests are also widely distributed in the east (Fig. 3.31), where they mainly occupy relatively well-drained flat tops, terraces, and terraced slopes; these forests have been found in all eastern study areas. Crown cover is 30–50% in the Karelian green moss – dwarf shrub Picea abies forests and varies from 20 to 80% in the eastern Picea obovata-Abies sibirica forests, where Picea obovata occurs more frequently. Picea spp. and Abies sibirica (in the east) dominate in the undergrowth. Betula pubescens, B. pendula, and Populus tremula often occur in the overstorey and understorey as well. Pinus sylvestris occurs in the overstorey and sometimes in the understorey in Karelia, whereas in the eastern study areas, P. sibirica more often occurs in the overstorey and in the undergrowth. Fire scars often occur on stems of Pinus spp.; scorched and broken stems of Pinus spp. can also be found. All these features, and the presence of charcoal in the soil, indicate that fires happened in the recent past. The cover of the understorey is 20–30%; Sorbus aucuparia, Juniperus communis, and Rosa acicularis (only in the east) often occur. Vaccinium myrtillus dominates in the field layer. Only Empetrum hermaphroditum also co-dominates in the Karelian forests. In the east, small boreal herbaceous species, such as Oxalis acetosella, Maianthemum bifolium, Gymnocarpium dryopteris, and Equisetum sylvaticum, mainly co-dominate. These species together with Trientalis europaea and Linnaea borealis are found in more than 75% of the sample plots. Generally, there are more dominants and species with a high fre-

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Fig. 3.62  Piceeta fruticuloso-hylocomiosa with Vaccinium myrtillus and V. vitis-idaea in Karelia (Photo by M. Bobrovsky)

quency in the eastern plots than in the west. However, in both regions, the field layer has a simpler structure in comparison with the forest types described above; there are far less nemoral species and tall herbs, whereas the number of oligotrophic species, such as Carex globularis, Rubus chamaemorus, Vaccinium uliginosum, and Empetrum hermaphroditum, and piny species such as V. vitis-idaea and Diphasiastrum complanatum is relatively high. Cover of the bottom layer is 80–90%. Pleurozium schreberi and Hylocomium splendens widely dominate; Polytrichum commune and Ptilium crista-castrensis often co-dominate. Dicranum scoparium is common in the west and D. polysetum and D. fuscescens in the east. Sphagnum spp. are not important. There is a relatively high diversity of lichens in the Karelian forests: Cladonia rangiferina, C. alpestris, C. mitis, C. stellaris, etc. occur. We recorded 9 tree, 5 shrub, and 43 herbaceous species in 70 plots in the Karelian green moss – dwarf shrub Picea abies forests, as against 11 tree, 11 shrub, and 95 herbaceous species in 75 plots in the eastern green moss  – dwarf shrub Picea obovata-­Abies sibirica forests. Based on the interpolation, species richness in the western green moss – dwarf shrub Picea abies forests is significantly lower than in the other forest types described above in the west; as regards species richness, the eastern green moss – dwarf shrub spruce-fir forests fall in the same group as the eastern green moss – small boreal herb and large fern forests (Fig. 3.24). The number of vascular species per plot varies widely (Fig. 3.25) and averages in total 16.1 in

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the Karelian forests and 21.9 in the eastern plots and 13.2 and 17.3, respectively, in the field layer. Much of the variation in species diversity is determined by the different structures of these forests, mainly connected with treefall mosaics. There are variants of green moss – dwarf shrub dark coniferous forests in which Picea spp. of low vitality dominate and old trees break and fall without uprooting. Vaccinium myrtillus, which dominates in the ground layer, covers the fallen trunks rather quickly and that greatly complicates the regrowth of Picea spp. (which usually occurs on deadwood); additional microsites with different ecological properties, as happens when trees fall with uprooting, are not formed. This is more typical for the Karelian green moss – dwarf shrub Picea abies forests, where Picea abies individuals with low vitality prevail. When trees of normal vitality dominate, they more often fall with uprooting and create additional microsites so that species with different ecological properties can settle and grow in such forests. The tall herbs Chamaenerion angustifolium and Geranium sylvaticum grow in the western, and the eastern green moss – dwarf shrub spruce(-fir) forests where the pit-and-mound topography are well developed; the tall herbs Rubus idaeus and Cirsium heterophyllum, the large fern Dryopteris dilatata, etc. occur in such forests in the east. Similar to the green moss – small boreal herb dark coniferous forests, green moss – dwarf shrub spruce(-fir) forests can directly develop into boreal tall herb forests in the absence of fires and the presence of treefalls with uprooting and the occurrence of seed flow of various plants from the tall herb forests. We have observed such situations in the plain part of the Komi Republic, but details of such forest transitions require further study. Podzols, mainly Haplic Podzols, are common in the green moss – dwarf shrub spruce(-fir) forests (Fig. 3.63). Albeluvisols also occur in such forests in the plain part of the Komi Republic. The E horizon is 10–15 cm thick in the Karelian forests

Fig. 3.63  Soil profiles (Haplic Podzol) in the Piceeta (P.-Abieta) fruticuloso-hylocomiosa: (a) Karelia and (b) the mountain part of the Pechora-Ilych Reserve (Photos by M. Bobrovsky)

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Fig. 3.64  Piceeta hylocomiosa with Hylocomium splendens, Pleurozium schreberi, Trientalis europaea, Maianthemum bifolium, Luzula pilosa, Vaccinium myrtillus, and V. vitis-idaea in Karelia (Photo by M. Bobrovsky)

and 10–25 cm in the eastern forests in the Komi Republic. Slight podzols (dwarf podzols) often occur in the forests of the western macro-slope of the Ural Mountains. Charcoal was found in all soil profiles. Lamellar charcoal usually occurs as a layer of several centimeters thick at the boundary of litter and the mineral horizon; this points to a large fire and the absence of subsequent treefalls with uprooting. In the Karelian green moss – dwarf shrub Picea abies forests, several (up to seven) layers of charcoal have been found under the litter; they were separated by unburned organic matter, mainly residues of rhizomes of Vaccinium myrtillus. This results from repeated fires and the absence of subsequent soil perturbation. Small lamellar and rounded charcoal also occurs in the E horizon and in sites of soil dumping due to windfall. Pure green moss spruce forests (Piceeta hylocomiosa), subsection of green moss – dwarf shrub forests, section of green moss forests. In Karelia, these forests are widespread on the middle and lower parts of slopes (Fig.  3.64), whereas the upper parts of those slopes are often occupied by Pinus sylvestris forests of the green moss or lichen sections. In the Komi Republic, such forests have been found only in the plain part, where they occupy flat areas including tops of plateaus and shallow terraces. Crown cover is usually 20–40% in the west and 30–50% in the east. Only Picea spp. dominate the stands, both in the west and in the east; Abies sibirica rarely occurs in the eastern plots. Betula spp. often occur. Pinus sylvestris is common in

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the Karelian forests and often occurs in the eastern green moss forests. Pinus sibirica is absent. Most Picea spp. individuals have a low vitality. Gaps in the canopy are single; the sparse woody canopy that is common in these forests is not due to gaps but to the low vitality of Picea spp. A small amount of deadwood in the first and second stages of decomposition occurs. Windbreak often prevails over treefalls with uprooting. Fire scars are common on the Pinus sylvestris stems. In Karelia, the average age of Pinus sylvestris is about 230 years and the maximum age is about 590 years; fire scars were mainly inflicted 170–330 years ago. Cover of the understorey is 20–30%; the shrub layer is sparse and poor in species. Juniperus communis, Sorbus aucuparia, and an undergrowth of Picea spp. and Betula spp. occur. Cover of the field layer is 30–50%. Only the dwarf shrubs Vaccinium myrtillus and V. vitis-idaea occur with high frequency. Species of the boreal group (Equisetum sylvaticum, Avenella flexuosa, Luzula pilosa, Linnaea borealis, and Lycopodium annotinum) and the oligotrophic group (Carex globularis, Rubus chamaemorus, Vaccinium uliginosum, and Empetrum nigrum) occur both in the western and e­ astern plots. Species of the nemoral, nitrophilous, and meadow groups are practically absent (Fig. 3.49). Cover of the bottom layer is 90–100%; the green mosses Hylocomium splendens, Pleurozium schreberi, and Dicranum scoparium dominate. While the cover values are high, the diversity of mosses is much lower than in the other dark coniferous forests. Soil lichens with small coverage and diversity occur. We recorded 7 tree, 2 shrub, and 22 herbaceous species in 25 sample plots situated in the Karelian pure green moss Picea abies forests and 8, 2, and 26 tree, shrub, and herbaceous species, respectively, in 16 plots in the eastern pure green moss Picea obovata forests. Thus, species richness is low compared to all other investigated dark coniferous forests (Fig. 3.50). Numbers of vascular species per plot are also low in these forests in comparison with all other forest types (Fig.  3.51); it averages in total 11 in the western and 11.9 in the eastern plots and 8.4 and 9.1, respectively, in the field layer. Haplic and Histic Podzols prevail. The thickness of the E horizon is similar to that in the green moss – dwarf shrub spruce(-fir) forests: 10–15  cm thick in the Karelian forests and 10–25 cm thick in the eastern forests. Charcoal is common in the soil, and its distribution in the profile is the same as in the green moss – dwarf shrub forests. In soil dumpings due to windfall, charcoal can be found down to 80 cm in the soil.

3.5.4  Conclusion We have identified several forest types among the old-growth forests dominated by Picea abies and located in Karelia and old-growth forests dominated by Picea obovata with Abies sibirica and located in the Komi Republic and Perm region. There are similar forest types in the western and eastern study areas: nitrophilous tall herb,

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boreal tall herb, green moss – small boreal herb, green moss – dwarf shrub, and pure green moss dark coniferous forests. Additionally, there are mountain boreal tall herb, large fern, and nemoral-boreal Picea obovata-Abies sibirica forests only in the eastern study areas. Comparative analysis of the forest types showed that vegetation diversity changes in a similar way in both regions: from the richest nitrophilous and boreal tall herb forests to the poorest green moss forests (Fig. 3.50). Forests in the east are generally richer in species than forests in the west. However, numbers of vascular species per plot are often similar in similar forest types in the western and in the eastern study areas (Fig. 3.51). There are similarities in the ecologicalcoenotic structure of the forest types as well as similarities in species diversity in the forests (Fig. 3.49). The ecological-coenotic diversity decreases from the tall herb to the green moss forest types: the structures are simplified by a reduction and finally a complete loss of the nitrophilous species, followed by nemoral species, tall herbs, and meadow plants; this is especially so for the Karelian Picea abies forests (Fig. 3.49). Only small and medium boreal species prevail in the poorest forest types, and oligotrophic and piny species occur with less abundance there. Similar values of species diversity are defined by similar structural features in the investigated forest types; in this respect gap mosaics and treefall mosaics are the most important features. The development of such mosaics largely depends on the fire regime and the occurrence of cutting in the study regions. Gap mosaics in the canopy and pit-and-mound topography are usually well developed in the tall herb dark coniferous forests: there are gaps of different ages and deadwood at different stages of decay and erosion. In the large fern, nemoral-­ boreal, and partly green moss – small boreal herb forests, gap mosaics in the canopy and pit-and-mound topography are also common, but here gaps and treefalls are of the same age and deadwood is all in the same stage of decay. In pure green moss, green moss – dwarf shrub, and partly green moss – small boreal herb forests, gap mosaics are poorly developed, trees often fall without uprooting, and various microsites such as pits and mounds are not formed. Traces of selective cutting are most clearly visible in the riparian forests. Generally, the occurrence and abundance of cutting traces (large cut stumps) are not directly related to the forest type; it is mostly related to the remoteness of the area from a river or a settlement that allows the possibility of industrial logging campaigns or local people to cut the forest. Traces of fire in the past are minimal in the nitrophilous and boreal tall herb spruce(-fir) forests: there are no fire scars on tree stems; charcoal in soil is absent or very rarely occurs. In the large fern spruce-fir forests, there are fire scars on Pinus sibirica stems and charcoal in all soil profiles. Accumulations of rounded pieces of coal under the 400-year-old Pinus sibirica individuals allow us to conclude that the last large fires there occurred about 400 years ago. To reveal traces of the more ancient fires in the large fern spruce-fir forests is mainly impossible due to the predominance of eroded soils in which buried coal is absent.

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In the nemoral-boreal spruce-fir forests, fire scars are absent on stems, but lamellar or rounded charcoal pieces are common in the soil. This means that fires were there but quite long ago, and treefalls with uprooting have happened after the fires. In the green moss – small boreal herb spruce(-fir) forests, fire scars occur on Pinus spp. stems, and charcoal usually occurs on the border of the litter and the mineral soil and in the E horizon. This means that there were no substantial perturbations of the soil, large trees did not fall with uprooting after the last fire, and the first generations (after the fire) of the populations of Picea spp. (and Abies sibirica in the east) now are growing in the overstorey. In the green moss – dwarf shrub and pure green moss spruce(-fir) forests, fire scars often occur on Pinus spp. stems, and lamellar charcoal usually occurs in one or several layers. This points to the long absence of treefalls with uprooting after the fires. This is possible if windbreak predominated over treefalls with uprooting or if intense cutting of Pinus spp. happened after the fires. Charcoal occurs under the litter and in the mineral soil as well. All this testifies that these forests formed after repeated or multiple fires. The current generations of Picea spp. in these forests are the first or rarely second generations of Picea spp. populations after the fires. Why is it important to know “the fire history” of the boreal forests? Fires impoverish populations of soil invertebrates: the main destructors of plant litter disappear (Kuleshova et al. 1996) and the biological activity of soils is reduced. Together with the changes in the ground layer of the vegetation, this changes the humus accumulation and leads to the formation of raw (moor) humus, which is typical for the soil in the forests of the green moss section (Podzols and Albeluvisols prevail there). High fire risk and a possibility of rapid fire spread over the ground surface remain during the accumulation of raw humus. Conversely, in the absence of fires, during the after-­ fire succession, the type of humus accumulation changes in the direction of moder-­ mull formation. This happens as a result of a concerted recovery of the different components of the ecosystem: the formation of a herbaceous cover with a predominance of mesophilic and mesohydrophilic herbs and the restoration of the soil fauna complex (Bobrovsky 2010). The composition and thickness of the humus horizon gradually change from moor to moder and moder-mull humus with the increasing proportion of herbaceous litter and the increasing intensity of soil turnover. Analysis of the characteristics of forest ecosystems allowed us to distinguish the early-, middle-, and late-successional stages of the ecosystems (see Sect. 2.5) and to conclude that tall herb dark coniferous forests can be considered as nearest to the late-successional stage. They can be formed as the outcome of recovering succession or may persist in areas without large external disturbances. To distinguish between these two options is very difficult, because traces of disturbances could have vanished in the vegetation and in the soil after several (many) generations of tree species populations. Soil features are very important in the analysis of forest ecosystem history as the soil traces of many events are conserved much longer than in the vegetation (Ponomarenko 1999; Bobrovsky 2010). But there are still many questions to be solved. Boreal tall herb spruce(-fir) forests differ from the other forest types by their well-developed mosaics of patches in the overstorey and in the understorey: gap

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mosaics in the canopy and pit-and-mound topography caused by treefalls with uprooting. Mesophilous tall herbs dominate in the ground layer, and all species of the regional flora, besides soil lichens, can grow there as a result of high microsite diversity, but species dominating at the early stages of after-fire succession are subordinate here. Combisols (brown soils) are the common soil type in the boreal tall herb dark coniferous forests; Histosols prevail under wetter conditions. Thus, comparative analysis of fire traces in vegetation, the presence of charcoal pieces, and their distribution in the soil in different forest types has allowed us to make the following main conclusion. Long-term fire history is the main factor determining the existence of different forest types under similar or different environmental conditions. Effects of fires are various. The main consequences of fires are the simplification of species composition and changes in humus type. Recovery after fires may be slow (many hundreds of years) or not too slow (decades). The speed of the recovery depends on the environmental conditions (the properties of the ecotope and changes therein as a result of fires), the occurrence of treefalls with uprooting (substrate availability), and the availability of seed flow from the regional species pool.

3.6  Conclusions on the Boreal Forest Region The boreal forest region of European Russia supports more forest than all other regions (Fig. 1.9): forests occupy 77% of the area (Bartalev et al. 2004). At that, the northern taiga is less disturbed by man than the Middle and the Southern Taiga: there is relatively less logging and there are fewer fires in the northern forests on loam compared to the more southern forests, while forests on light sands and rubbly soil are almost equally disturbed throughout the entire boreal forest region. Thirty-seven percent of the forested area in the region consists of dark coniferous forests: stands dominated by Picea spp. sometimes with an admixture of Abies sibirica (in the east) or with a small admixture of Betula spp. or Populus tremula. The rest of the forested area is occupied by stands formed by early-successional tree species which are developing after catastrophic disturbances. Stands dominated by Pinus sylvestris are typically formed after fires; stands dominated by Betula spp. with Populus tremula often with an admixture of coniferous species are developing at places of clear-cutting and fires; stands of Betula pendula and/or B. pubescens as well as of Alnus incana grow on abandoned agricultural lands (Smirnova 2004; Yaroshenko et al. 2008). It is important to note that the area of planted forests is relatively small throughout the boreal region, and the care for tree plantings is minimal. So, despite numerous human impacts, the vast majority of forests in the boreal forest region can be called natural forests which mainly developed after various disturbances. On the whole, the variety of boreal forests that developed after disturbances is large and is determined by the type of anthropogenic impacts and the successional stage of forest development after disturbances. Features of the forests at their initial stages of succession are the following: (i) prevalence or a high proportion of pioneer tree species such as Pinus sylvestris, Betula spp., Populus tremula,

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and Alnus incana, (ii) a high tree density in the stands and the absence of a gap mosaic formed by the spatial distribution of groups of trees at different ontogenetic stages, and often (iii) a small amount of deadwood and a smooth topography. In the absence of fire and other catastrophic disturbances, forests dominated by early-successional trees are gradually replaced by forests dominated by late-­ successional species such as Picea abies in the west of the region and P. obovata and Abies sibirica in the east. However, the first and often second generations of late-successional trees do not always change the structure and composition of the forests. A high density of even-aged stands, poorly developed understorey, dominance of dwarf shrubs and boreal mosses in the ground layer, and prevalence of soil with moor and moor-moder humus horizons are typical features of the dark coniferous forests that are widespread in European Russia (Gribova et al. 1980; Yaroshenko et al. 2001; Smirnova 2004; Shorohova et al. 2009) and over the entire boreal forest region in Europe as well (Kuuluvainen et  al. 1998; Angelstam and Kuuluvainen 2004; Hedwall et  al. 2013). Numerous studies (Uotila et  al. 2002; Lankia et  al. 2012; Storaunet et  al. 2013, etc.), including investigations in northeastern Fennoscandia, confirmed that in the majority of the modern dark coniferous forests, fires occurred relatively recently: for example, Uotila et  al. (2002) showed that, according to historical records, 89% of 79 boreal forest sites dominated by Picea abies and Vaccinium myrtillus experienced fires in the nineteenth or twentieth century. It is well-known that the long-term dynamics of most modern boreal forest ecosystems are associated with fire: forest communities at different stages of pyrogenic succession are extremely widespread and well studied in European Russia (Sambuk 1932; Korchagin 1954; Rysin 1975; Vakurov 1975; Sannikov 1992; Gromtsev 1993, 2000, 2002; Kuleshova et al. 1996; Yaroshenko et al. 2001; Yarmishko et al. 2009; Stavrova et  al. 2016) and in other countries as well (Johnson 1996; Tinner et  al. 1999; Angelstam and Kuuluvainen 2004, etc.) However, we are of the opinion that fire is not an obligatory element of boreal forest dynamics (Syrjänen et al. 1994; Smirnova and Korotkov 2001; Smirnova et  al. 2006, 2011). It is possible to find boreal forest ecosystems in European Russia which have developed without fire for more than 500 or 600 years; and their properties are very different from those of pyrogenic ecosystems. During long-term absence of fire, boreal forests become rich in species and in soil nutrients; and they score the highest values for ground layer phytomass of all boreal forests. Such dark coniferous forests dominated by nitrophilous tall herbs occur along the streams and small rivers practically over the entire boreal forest region. Dark coniferous forests dominated by boreal tall herbs and located on watersheds or slopes occur rarely. We found them in the Murmansk region, in the Karelia and Komi republics, and in the Arkhangelsk, Vologda, and Perm regions (numbers 1, 2, 4–6, 8–13 in Fig. 3.44). In all these study areas, boreal tall herb spruce(-fir) forests have been found in places with a relatively low probability of spreading fires. Variants of “safe havens” from fires can be divided into three groups: (1) fire refuges in wind shadows under the protection of rocks, between gorges, screes, etc.; these more often occur in mountain areas including low and middle mountains in the Murmansk region, in the northwestern Karelia, and in the

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Ural Mountains (the Komi Republic and the Perm region); (2) fire refuges in floodplains surrounded by wet depressions, oxbow lakes, between closely spaced streams, wet gullies, etc.; they are typical in the aforementioned mountain areas as well as in flat areas over the entire boreal region; and (3) fire refuges in upland and slope areas experiencing continuously or periodically high moisture conditions due to high groundwater levels or inflow of moisture from upstream watershed areas, etc.; we have seen such places in the Karelia and Komi republics and the Vologda region. At some places we find a mix of these types of fire havens. Thus, in the boreal forest region, dark coniferous forests dominated by tall herbs in the ground layer can be considered as forests at the final successional stage. Natural succession necessarily leads to the development of such forest, but there are a lot of obstacles in the way. First of all, due to the slow speed of all processes in the north, a very long time is required to change the composition and functioning of an ecosystem. The age of Pinus sylvestris individuals in green moss – dwarf shrub pine forests in the northern taiga exceeds 600 years; more than 500-year-old Picea spp. occur regularly in green moss – dwarf shrub spruce forests (Smirnova and Korotkov 2001; Smirnova 2004). In the east of European Russia, more than 400-year-old Pinus sibirica trees are common in green moss – dwarf shrub spruce(-fir) forests (Smirnova et  al. 2011). The long persistence of these plant communities and the long dominance of boreal dwarf shrubs and green mosses (Pleurozium schreberi, Hylocomium splendens, etc.) lead to the accumulation of a thick litter layer, where concentrations of phenols and tannins reach high values and, as a result, the solubility of organic matter and their availability for most plants decrease (Preston and Schmidt 2006; Lukina et al. 2008). Furthermore, a thick litter layer serves as a filter for heat and moisture. As a result, soil temperature decreases and soil moisture increases in the root layer and that impairs tree development and creates conditions for the accumulation of moor humus or peat. In extremely poor environments, such communities can turn into Vaccinium myrtillus  – green moss heaths, and there a degradation of the forest ecosystems is observed (Nevrli 1912; Nat 1915; Siren 1955; Voropanov 1950; Dyrenkov 1984; Smirnova and Korotkov 2001). Under less severe conditions, such forests are delayed in their transition to the next successional stages by hundreds of years. The two main reasons for this are the following: (i) there is a lack of biogenic disturbances in the ground layer when impaired trees fall without uprooting and open microsites for the settlement of new species are not formed, and (ii) there is a lack of seed flow of other regional plants such as medium and tall herbaceous plants as a result of the widespread occurrence of forests of the green moss section over the entire boreal forest region. We should stress that the nutrient status of the soils is probably not a major limiting factor for the successional change from green mosses and dwarf shrubs to herbs and ferns: experiments show that nitrogen application does not accelerate the succession in this case (Manninen et al. 2009). The possibility for the establishment of new species is not so much determined by a change in soil nutrient status but (i) by the appearance of “free” microsites suitable for the colonization by other species and (ii) by the existence of seed flow of these species.

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There are two basic types of microsites that arise from treefalls with uprooting that break the continuous cover of dwarf shrubs and mosses: (1) pits and mounds which offer spots of bare soil with a variety of environmental regimes and (2) fallen trunks which decompose over time and provide a substrate for colonization by different plant species. However, there may be situations where fungi, the important agents of wood decay, are absent from the forest as a result of numerous fires (Spirin and Shirokov 2002). In such situations only mechanical erosion and mummification of the wood can be observed, and there is no colonization of the wood by vascular plants. In fact, the presence of deadwood at different stages of decay may indicate an old-growth forest, but only when it is overgrown by vascular plants of various ecological-coenotic groups, it does indicate a late-successional forest; the presence of “coarse woody debris,” which is often emphasized as desirable in literature on nature conservation, is a necessary but not a sufficient condition for attributing a forest to either a mid- or a late-successional stage. Thus, whether or not the deadwood is overgrown is a more important indicator. As said above, changes in the soil nutrient regime are probably not a main driver of succession, but succession is the result of mutually balanced changes over time in the ground vegetation and soil biological complex. The type of humus that accumulates also changes during succession, from moor to moder and moder-mull, due to the increasing proportion of herbaceous litter and to the increasing soil fauna activities as well. Lukina (2008) and Lukina et al. (2008) observed the following changes in the soil nutrient regime during succession in the boreal coniferous forests: (1) the acidity of the organic horizons in the soil decreases; (2) there is an accumulation of carbon and nutrients such as N, K, P, Ca, Mg, S, Mn, etc. in the soil; (3) there is an accumulation of humus; (4) the abundance and biomass of microorganisms in the soil increase; and (5) the C/N ratio in the organic soil horizons decreases. The C/N ratio varies in different coniferous forests in European Russia as follows. In forests in the Murmansk region, the C/N ratio decreases over time from 49 to 41 in Pinus sylvestris forests co-dominated by lichens and green mosses – Vaccinium myrtillus in the ground layer and from 35 to 25 in Picea abies forests co-dominated by green mosses and V. myrtillus – small boreal herbs (Lukina et al. 2008). In old-growth Picea abies forests in Northern Karelia, the C/N ratio varies from 25 to 41 in forests of the green moss – dwarf shrub subsection, from 25 to 33 in forests of the green moss – small boreal herb subsection, and from 16 to 26 in forests of the boreal tall herb section (Lukina et al. 2008). In old-growth Picea obovata-Abies sibirica forests in the Pechora-Ilych State Nature Reserve, it varies from 22 to 25 in forests of the green moss – small boreal herb subsection, from 18 to 20 in the large fern forests, and from 16 to 18 in the boreal tall herb forests (Bobrovsky 2010). According to Högberg et al. (2006), average C/N values in organic soil horizons in Picea abies forests of similar types located in Sweden are very close to the values observed in Russia: 46.5 in green moss – dwarf shrub forests, 27.2 in green moss – small boreal herb forests, and 16.6  in boreal tall herb forests. On the whole, the C/N ratio decreases toward the later stages of succession; and nitrogen stops being a limiting

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factor in plant nutrition in climax boreal forests (Högberg et al., 2006; Lukina 2008; Lukina et al. 2008). However, so far we only made a beginning with quantitative investigations on functional relationships in the intact forest landscapes in the boreal forest region. The relatively low intensity of human disturbance of the boreal forests in European Russia and the existence of the unique tall herb forests on watersheds provide us with reference points for studying the boreal forest ecosystems. Thereby future researches have to explore functional relationships between ecosystem components (such as vegetation, soil, soil macrofauna, fungi, microorganisms, etc.) in areas with minimal intensity of catastrophic disturbances (fires, cutting, storms) and in the most common disturbed areas as well but taking into account the type and regime and the time of the disturbances which formed these ecosystems.

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Tsinzerling YuD (1931) Geografiya rastitelnogo pokrova severo-zapada Evropeyskoy chasti SSSR. Trudy Geomorfologicheskogo instituta AN SSSR 4:7–377 – Geography of the vegetation cover in the north-west of the European part of the USSR Tyurin AV (1925) Osnovy khozyaistva v sosnovykh lesakh. Izd-vo Novaya derevnya, Moscow – The basis of forest management in the Pinus sylvestris forests Uino P (1997) Ancient Karelia. Archeological studies 104. Muinaismuistoyhdistys, Helsinki, p 426 Uotila A, Kouki J, Kontkanen H, Pulkkinen P (2002) Assessing the naturallness of boreal forests in eastern Fennoscandia. For Ecol Manag 161:257–277 Vakurov AD (1975) Lesnye pozhary na Severe. Izd-vo Nauka, Moscow, 100 pp – Forest fires in the North Varsanofyeva VA (1932) Geomorfologicheskie nablyudeniya na Severmom Urale. Izvestiya Geograficheskogo obshchestva 64 (2–3) – Geomorphological observations in the Northern Ural Mts Vasilevich VI (2002) Travyanye elniki Evropeyskoy Rossii. Botanichesky zhurnal 87(1):13–27 – Herb spruce forests in European Russia Vlasova IV (1998) Traditsionnyi opyt prirodopolzovaniya na Russkom Severe. In: Danilova LV, Sokolov AK (eds) Traditsionnyi opyt prirodopolzovaniya v Rossii. Izd-vo Nauka, Moscow, pp 119–138 – Traditional experience of land-use in the Russian north Vlasova IV (2001) Russkiy Sever: etnicheskaya istoriya i narodnaya kultura 12-20 vv. Izd-vo Nauka, Moscow. 848 pp – The Russian north: the ethnic history and folk culture Volkov AD (2008) Tipy lesa Karelii. Karelskiy nauchniy centr, Petrozavodsk, 180  pp – Forest types of Karelia Voropanov PV (1950) Elniki Severa. Goslesbumizdat, Moscow-­Leningrad, 180 pp – Spruce forests in the north Wallenius T (2002) Forest age distribution and traces of past fires in a natural boreal landscape dominated by Picea abies. Silva Fenn 36(1):201–211 Wrangell V (1841) Istoriya lesnogo zakonodatelstva Rossiyskoi imperii. S prisoedineniem ocherka istorii korabelnykh lesov Rossii. Tipografiya Fishera, SPb, 153 pp – History of forest legislation in the Russian Empire with the addition of an essay on the history of ship forests in Russia Yarmishko YT, Bakkal IYu, Borisova OV, Gorshkov VV, Katyutin PN, Lyanguzova IV, Maznaya EA, Stavrova NI, Yarmishko MA (2009) Dinamika lesnykh soobshchestv severo-zapada Rossii. Izd-vo VVM, SPb, 276 pp – Dynamics of forest communities in the north-west of Russia Yaroshenko AYu (1999) Evropeyskaya taiga na grani tysyacheletiy. Greenpeace of Russia, Moscow, 66 pp – European taiga on the verge of millennia Yaroshenko AY, Potapov PV, Turubanova SA (2001) The last intact forest landscapes of northern European Russia. Greenpeace Russia, Moscow, 73 pp Yaroshenko AYu, Dobrynin DA, Egorov AV, Zhuravleva IV, Manisha AE, Potapov PV, Turubanova SA, Khakimulin YeV (2008) Lesa centra i severa Evropeyskoy Rossii. Karta 1:4 500 000. Greenpeace Russia, Moscow – Forests of the center and the north of European Russia. Map 1:4,500,000 Yelina GA, Kuznetsov OL, Devyatova EI, Lebedeva RM, Maksimov AI, Stoykina NV (1994) Sovremennaya i golocenovaya rastitelnost natsionalnogo parka Paanayarvi (severo-zapadnaya Karelia). Botanichesky zhurnal 79(4):13–31 – The current and Holocene vegetation of the National Pak Paanayarvi, in north-western Karelia Zaboeva IV (1975) Pochvy i zemelnye resursy Komi ASSR. Komi knizhnoe izd-vo, Syktyvkar, 324 pp – Soil and land resources in the Komi Republic Zackrisson O (1977) Influence of forest fires on the north Swedish boreal forest. Oikos 29:22–32 Zaprudina MV (2012) Mikromozaichnaya organizatsiya travyano-kustarnichkovogo i mokhovogo pokrova srednetayezhnykh temnokhvoinykh lesov Urala. Dissertation (Candidate of sciences) in biology. Moskovskiy pedagogicheskiy gosudarstvennyi universitet, Moscow, 204 pp – Micromosaic structure of the ground layer in the middle taiga dark-coniferous forests in the Ural Mts

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Zaprudina MV, Smirnov VE (2010) Mikromozaichnaya organizatsiya travyano-­kustarnichkovogo i mokhovogo pokrova vysokotravnykh pikhto-elnikov s kedrom nizhney chasti basseina reki Bolshaya Porozhnaya (pritok reki Pechora). Trudy Pechoro-­Ilychskogo zapovednika. Komi nauchnyi tsentr UrO RAN, Syktyvkar 16:60–68 – Micromosaic structure of the ground layer in the tall-herb Picea obovata and Abies sibirica with Pinus sibirica forests in the lower part of the Bolshaya Porozhnaya River basin (a tributary of the Pechora River) Zaugolnova LB (2008) Podkhody k otsenke tipologicheskogo raznoobraziya lesnogo pokrova. In: Isaev AS (ed) Monitoring biologicheskogo raznoobraziya lesov Rossii:metodologiya i metody. Izd-vo Nauka, Moscow, pp 36–58 – Approaches to the assessment of typological diversity of forest cover Zaugolnova LB, Martynenko VB (2014) Opredelitel tipov lesa Evropeyskoy Rossii. URL http:// www.cepl.rssi.ru/bio/forest/index.htm – Guide to the forest types in European Russia Zaugolnova LB, Morozova OV (2004) Rasprostranenie i klassifikatsiya borealnykh lesov. In: Smirnova OV (ed) Vostochnoevropeyskie lesa (istoriya v golocene i sovremennost), vol 2. Izd-vo Nauka, Moscow, pp 295–330 – Distribution and classification of the boreal forests in European Russia Zaugolnova LB, Morozova OV (2006) Tipologiya i klassifikatsiya lesov Evropeyskoy Rossii: metodicheskie podkhody i vozmozhnosti ikh realizatsii. Lesovedenie 1:34–48 – Typology and classification of forests in European Russia: methodological approaches and their feasibility Zaugolnova LB, Morozova OV (2012) Coenofond lesov Evropeiskoy Rossii. URL http://www. cepl.rssi.ru/bio/flora/index.htm – Coenofond of forests in European Russia Zaugolnova LB, Smirnova OV, Braslavskaya TYu, Degteva SV, Prokazina TS, Lugovaya DL (2009) Vysokotravnye tayezhnye lesa vostochnoy chasti Evropeyskoy Rossii. Rastitelnost Rossii 15:3–26 – Tall herb boreal forests in the eastern part of European Russia Zyabchenko SS (1984) Sosnovye lesa Evropeyskogo Severa. Izd-vo Nauka, Leningrad, 248 pp – Pinus sylvestris forests in the European north

Chapter 4

Hemiboreal Forests O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, L.B. Zaugolnova, A.I. Shirokov, D.L. Lugovaya, V.N. Korotkov, V.A. Spirin, T.Yu. Samokhina, and M.V. Zaprudina

Abstract  Long-term studies of forest vegetation, soil and features of the historical land-use in the hemiboreal region showed that during the last 300 years practically all hemiboreal forests in European Russia have experienced anthropogenic impacts, such as logging, fires, tree planting or agriculture. Various land-use practices have been wider spread in the hemiboreal region, as compared to the boreal one, and that O.V. Smirnova (*) • L.B. Zaugolnova • T.Yu. Samokhina • M.V. Zaprudina Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia e-mail: [email protected] M.V. Bobrovsky (*) Institute of Physico-Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] L.G. Khanina (*) Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] A.I. Shirokov (*) Botanical Garden, N.I. Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia e-mail: [email protected] D.L. Lugovaya (*) Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia WWF Russia, Moscow, Russia e-mail: [email protected] V.N. Korotkov (*) Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia e-mail: [email protected] V.A. Spirin Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland Natural History Museum, University of Oslo, Oslo, Norway © Springer Science+Business Media B.V., part of Springer Nature 2017 O.V. Smirnova et al. (eds.), European Russian Forests, Plant and Vegetation 15, https://doi.org/10.1007/978-94-024-1172-0_4

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has led to the higher degree of destruction of the hemiboreal forests. Absolute ­domination of the pioneer trees Betula spp., Populus tremula or Pinus sylvestris in the region and the structural simplification of late-successional dark-coniferous and/or broad-leaved forests are the main results of this destruction. Species-rich hemiboreal forests dominated by Picea abies or P. obovata with Abies sibirica and Tilia cordata in the overstorey and boreal and nemoral tall herbs and ferns in the understorey, with a patchy organization of their forest canopy and a diversity in microsites caused by treefalls are preserved only in the sparsely populated areas that are the most difficult for economic exploitation. However, due to the overlap in the distribution areas of most of the boreal and nemoral plant species in the region and the strong variation of intensity of human impacts over the region, in general a relatively high level of biodiversity is maintained in the hemiboreal forests.

4.1  P  rodromus of the Vegetation and Forest Distribution in the Hemiboreal Region The description of the hemiboreal forests as well as the boreal ones is based on the Coenofond of the European Russian forests (Zaugolnova and Morozova 2004, 2006, 2012; Zaugolnova 2008; Zaugolnova and Martynenko 2014). Explanations of the structure and principles of the Coenofond are given in Sect. 2.2. The classification of the hemiboreal forests has many similarities with the boreal forest classification. The differences are in the following: (1) the section of large fern forests is absent here because forests dominated by large ferns in the field layer do not form pure, extended tracts here as they do in the boreal region and so these communities are not well investigated here, and (2) the equivalent of the section of boreal tall herb forests is, in the hemiboreal region, included in an expanded section of herb forests due to a high diversity of forests dominated by herbaceous species in the field layer. Similarities and differences with forest communities described from the boreal forest region are specified below.

4.1.1  Section: Lichen Forests The main diagnostic feature of forests in this section is the same as in the boreal forest region: there is a domination of bushy lichens in the ground layer. As in the boreal region, the lichen forests grow on sandy substrates and are often susceptible to fire. However, in the hemiboreal region, only Pinus sylvestris occurs as a dominant tree species in these forests, whereas in the boreal region, Larix sibirica and Pinus sibirica (in the east), Betula pubescens and Picea spp. in the north throughout the region, also dominate. Probably due to the milder climatic conditions in the hemiboreal region, lichens in the ground layer more readily alternate with mosses,

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dwarf shrubs and herbs as soon as other trees, not pine, appear (this may also be because of higher values of bioavailable soil nutrients under the canopy of Picea spp. compared with Pinus sylvestris canopies in old-growth forests located in the same relief position, bedrock and climate; see Lukina 2008; Lukina et  al. 2008; Orlova et al. 2013). The syntaxonomic diversity of the lichen forests is also lower in comparison with that in the boreal forest region: all plant communities of this section belong to one association Cladonio arbusculae–Pinetum sylvestris (Caj. 1921) K.-Lund 1967, while we distinguish two subsections within the lichen forest section – the genuine lichen forests and the lichen – green moss forests. As in the boreal region, Al-Fe-humic podzols, mostly Haplic Podzols, are common in the lichen forests located in the hemiboreal region. Subsection of genuine lichen forests includes plant communities of the following subassociations: C.a.–P.s. cladonietosum cornutae Solomeshch 1994 ex Martynenko nov. prov. var. Picea obovata; C.a.–P.s. sedetosum hybridae Martynenko nov. prov. and C.a.–P.s. koelerietosum glaucae Bulokhov et Solomeshch 2003 (Solomeshch 1994; Bulokhov and Solomeshch 2003; Martynenko 2009). Genuine lichen pine forests (Pineta sylvestris cladinosa) occur on outwash plains, sandy river terraces, on gravelly substrate in mountains of medium-elevation and on ridge-and-hollow plains located on crystalline rocks. They are described from over the entire hemiboreal region (Smirnova 1928; Nitsenko 1960b; Bulokhov and Solomeshch 2003; Fedorchuk et al. 2005; Martynenko 2009). Pinus sylvestris dominates in the overstorey with a crown cover 40–60%. The site productivity quality is usually higher than in the boreal forest region (site classes 3 and 4). Betula pubescens, B. pendula, Populus tremula, Quercus robur (in the southern part of the hemiboreal region) and Larix sibirica (in the central and eastern parts) can occasionally be found as an admixture in the overstorey. In the sparse shrub layer Juniperus communis dominates; Chamaecytisus ruthenicus, Frangula alnus, Salix caprea and Sorbus aucuparia sparsely occur. Regrowth of Pinus sylvestris, Picea abies and Betula pendula is found in some communities. Cover of the ground layer is more than 20%; it is generally higher than in such forests in the boreal region; it rarely comes up to 50%. Unlike the boreal forests, not only dwarf shrubs (Calluna vulgaris, Arctostaphylos uva-ursi, Vaccinium myrtillus, V. vitis-­idaea, etc.), but also northern piny herbs, such as Antennaria dioica, Carex ericetorum and Festuca ovina, the southern piny herb Pulsatilla patens and the small boreal herb Melampyrum pratense occur regularly. The bottom layer includes mainly lichens with patches of green mosses. Cover of the bottom layer reaches 80–90% although it may be very much less here and there, likely due to a ground fire. Lichens of the genus Cladonia prevail; Cetraria islandica is common. Dicranum polysetum, D. scoparium, Pleurozium schreberi, Polytrichum piliferum and P. juniperinum are most common among the green mosses. Subsection of lichen – green moss forests includes plant communities of two subassociations C.a.–P.s. cladonietosum cornutae Solomeshch 1994 ex Martynenko nov. prov. var. Cladonia mitis and C.a.–P.s. cladonietosum amaurocraeae Fedorchuk

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et al. ex Zaugolnova et Martynenko nov. prov. (Fedorchuk et al. 2005; Zaugolnova and Martynenko 2014). Lichen – green moss pine forests (Pineta sylvestris hylocomioso-cladinosa) are found on sandy ridges of river terraces and on tops of hills and ridges over the entire hemiboreal region. Cover of the overstorey is 40%. It consists of Pinus sylvestris of 20–23 m high and with trunk diameters of 36–44 cm and ages of 100–200 years (Smirnova 1928; Fedorchuk et al. 2005). The sparse shrub layer consists of a few individuals of Sorbus aucuparia, Juniperus communis, Chamaecytisus ruthenicus; Juniperus communis individuals sometimes reach up to 3 m in height. In relatively young forests, the undergrowth is absent. In old forests, depressed individuals of Pinus sylvestris with a singular admixture of Betula pendula and Picea spp. can be found in the undergrowth. The field layer covers 30–40%, sometimes up to 80%; Vaccinium vitis-idaea, Antennaria dioica, Calamagrostis arundinacea and Convallaria majalis are the most abundant species but they do not dominate. Cover of the bottom layer is 60–100%; lichens such as Cladonia rangiferina, C. arbuscula and Cetraria islandica together with green mosses codominate. Pleurozium schreberi prevails; Polytrichum juniperinum and Dicranum polysetum often occur (Smirnova 1928; Shilov 1971; Romanovsky 2002; Fedorchuk et al. 2005).

4.1.2  Section: Green Moss Forests The diagnostic feature of these forests is the dominance of boreal green mosses in the ground layer. These forests are widely distributed in the hemiboreal region of European Russia. They are classified in the following two unions of the class Vaccinio–Piceetea Br.-Bl. in Br.-Bl., Sissingh et Vlieger 1939: union Dicrano–­ Pinion (Libbert 1933) Matuszkiewicz 1962 (= Phyllodocco–Vaccinion Nord. 1936) and union Piceion excelsae Pawłowski, Sokołowski et Wallisch 1928 (= Vaccinio–­ Piceion Br.-Bl., Sissingh et Vlieger 1939). Within the two unions green moss forests are classified into eight associations divided over the following three subsections of green moss forests: green moss – dwarf shrub, green moss – small boreal herb, and green moss – piny herb forests. The syntaxonomic diversity of the green moss forests is significantly higher than that of those in the boreal region (Bulokhov and Solomeshch 2003). Soils in the green moss forests are also diverse and that is primarily due to differences in soil-forming rocks and the history of anthropogenic impacts. Subsection of green moss – dwarf shrub forests includes plant communities of the following four associations of the union Dicrano–Pinion: (1) ass. Vaccinio vitis-idaeae–Pinetum Sokołowski 1980 (= Vaccinio–Pinetum boreale Caj. 1921, Dicrano–Pinetum sylvestris Preising et Knapp ex Oberdorfer 1957, Monotropo–Pinetum Korotkov 1986), (2) ass. Vaccinio myrtilli–Pinetum (Kobendza 1930) Br. Bl. et Vlieger 1993, (3) ass. Platanthero bifoliae–Pinetum sylvestris Bulokhov et Solomeshch 2003, and (4) ass. Molinio caeruleae–Pinetum sylvestris (E. Schmid. 1936) em. Mat. (1973) 1981, and the following two associations of the union Piceion excelsae: (1) ass. Linnaeo borealis–Piceetum abietis (Caj. 1921) K.-Lund 1962, and (2) ass. Junipero communis–Piceetum abietis Korchagin et Senjaninova-Korchagina 1957 prov. ex. Martynenko nov. prov.

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As a whole, this subsection unites communities of dark and light coniferous forests (and secondary small-leaved deciduous and mixed forests as well) of the class Vaccinio–Piceetea Br.-Bl. in Br.-Bl., Sissingh et Vlieger 1939. Picea abies, P. obovata, Abies sibirica, Pinus sylvestris and rarely Larix sibirica dominate in the overstorey, with a constant admixture of Betula pubescens, B. pendula, Populus tremula and often Alnus incana. In the south of the hemiboreal region one can find a small admixture of Tilia cordata and rarely Quercus robur. The understorey consists of undergrowth of Picea spp. and Abies sibirica as well as Sorbus aucuparia, Juniperus communis, Rosa acicularis, Lonicera xylosteum, L. pallasii, Frangula alnus and Daphne mezereum. Boreal dwarf shrubs dominate and small boreal herbs are constant in the field layer. Calamagrostis arundinacea has a high constancy, especially in forests dominated by Pinus sylvestris. Rubus idaeus often occurs. From the group of nemoral herbs, species which are least demanding as regards soil fertility, such as Convallaria majalis and Stellaria holostea, can rarely be found in low abundance. The moss cover is well developed; boreal green mosses prevail and hemiboreal green mosses occur. Green moss  – dwarf shrub pine forests (Pineta fruticuloso-hylocomiosa) are located on sandy, clayey and mixed sediments at flat dune tops and other flat dune areas, or at flat and slightly elevated parts of terraces over the entire hemiboreal region (Sokolov 1931; Chernov 1940; Rysin 1975; Bulokhov and Solomeshch 2003; Fedorchuk et al. 2005; Popov 2008; Rysin and Savelieva 2008). The following Al-Fe-humus soils dominate: illuvial-humic ferrugenous podzols (Haplic Podzols) and illuvial-ferrugenous and ochric podzols (Rustic Podzols). Pinus sylvestris dominates in the overstorey with an admixture of Betula pubescens, B. pendula, Populus tremula and Larix sibirica in the east. Crown cover is 60–80%. The understorey is poorly developed and consists of single individuals of Juniperus communis, Frangula alnus and Sorbus aucuparia. In the undergrowth Picea spp. prevail, Tilia cordata and Acer platanoides appear in the south. Depending on the successional stage of recovery after fire or logging, the undergrowth of Picea spp. can form the second tree layer in the forest canopy (Sukachev 1908; Maslov 2000). Undergrowth of Pinus sylvestris appears after ground fires. Such a Pinus sylvestris undergrowth (up to 1 m in height) counts up to 1000 individuals per h­ ectare in Pinus sylvestris forests dominated by Calluna vulgaris (Konovalov and Povarnitsyn 1931). Cover of the field layer varies from 20 to 80%. Vaccinium myrtillus and V. vitis-idaea dominate; Convallaria majalis and Calamagrostis arundinacea often occur. The admixture of small boreal herbs varies: they are more common in forests dominated by V. myrtillus than in forests dominated by V. vitis-­idaea. In the latter, the species of the piny ecological-coenotic group, such as Calluna vulgaris, Antennaria dioica, etc., often occur and they are practically absent in forests dominated by V. myrtillus. Calluna vulgaris dominates in the young, post-fire Pinus sylvestris forests. Cover of the bottom layer is 70–100%. Pleurozium schreberi dominates; Polytrichum commune, Ptilium crista-castrensis, Rhytidiadelphus triquetrus and Dicranum scoparium often occur. Species of the genus Cladonia can be found in forests dominated by V. vitis-idaea. Coverage of the bottom layer decreases to 10% or less as a result of ground fires. Epiphytic lichens can be found on trunks of Pinus sylvestris (Korotkov 1991).

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Green moss  – dwarf shrub spruce forests (Piceeta fruticuloso-hylocomiosa) mainly occupy watersheds and slopes of river terraces and occur over the entire hemiboreal region. In the south, these forests mainly grow in depressions and they are often surrounded by oligotrophic bogs (Smirnova 1928, 1951, 1954; Korchagin and Senjaninova-Korchagina 1957; Nitsenko 1960a). Green moss  – dwarf shrub spruce forests occur on various soils: podzolics (Haplic Albeluvisols) and sod-­ podzolics (Albic Luvisols, Umbric Albeluvisols) dominate on loamy plains; podzols (Haplic and Rustic Podzols) dominate on sandy substrate. Crown cover varies from 40 to 80%. Picea abies in the west and P. obovata in the east dominate in the overstorey. In the east some Abies sibirica can be admixed. Usually Betula pubescens and B. pendula, and rarely Pinus sylvestris, Populus tremula, Alnus incana and Padus avium, occur in the stands. Cover of the understorey depends on the tree canopy coverage; it varies between 8 and 20%. Sorbus aucuparia is often common in this layer with a small admixture of Daphne mezereum, Lonicera xylosteum and Frangula alnus. A relatively high coverage of the understorey is often created by tree undergrowth: Picea spp. dominate there, and sometimes Abies sibirica occurs, Quercus robur and Tilia cordata can be occasionally found. Cover of the field layer is 30–80%. Vaccinium myrtillus, V. vitis-idaea and Oxalis acetosella often codominate. Small boreal herbs, such as Maianthemum bifolium, Linnaea borealis, Luzula pilosa, Rubus saxatilis and Trientalis europaea, often occur with low abundances. Cover of the bottom layer is 50–100%. Pleurozium schreberi, Hylocomium splendens, Dicranum scoparium and Rhytidiadelphus triquetrus codominate; patches with a high occurrence of Polytrichum commune can be found; Sphagnum girgensohnii and S. russowii grow in the wetter habitats (Rysin 1960; Vasilevich 1983, 2004a; Savelyeva 2000; Romanovsky 2002; Maslov 2004). Green moss  – dwarf shrub birch and aspen forests (Betuleta (Populeta) fruticuloso-­hylocomiosa) usually develop after felling of green moss – dwarf shrub spruce(−fir) forests and soils are usually the same as soils in those forests. Crown cover is 60–70%. Betula pubescens and Populus tremula dominate with a small admixture of Picea spp. or rarely Pinus sylvestris. Quercus robur can be found in the overstorey dominated by Populus tremula. Cover of the understorey is 30–40%: Sorbus aucuparia and Frangula alnus often occur together with an undergrowth of Picea spp.; Juniperus communis and an undergrowth of Quercus robur, Populus tremula and Betula pubescens are less common. Corylus avellana and Acer platanoides also occur in the understorey of these forests dominated by Populus tremula. Cover of the field layer is 40–60%: Vaccinium myrtillus dominates; Melampyrum pratense, Trientalis europaea, Avenella flexuosa, Vaccinium vitis-­ idaea and Molinia caerulea are constant. The field layer of forests dominated by Populus tremula is richer compared to those dominated by Betula pubescens: Dryopteris carthusiana, Solidago virgaurea and Calamagrostis arundinacea occur there (Gavrilov and Karpov 1962; Liksakova 2004). Cover of the bottom layer is 90% and more: Pleurozium schreberi dominates; Dicranum polysetum and Polytrichum commune often occur; the abundance of Sphagnum girgensohnii is sometimes considerable. Initial signs of waterlogging are often conspicuous in green moss – dwarf shrub birch forests.

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Subsection of green moss – small boreal herb forests includes the following four associations of the union Piceion excelsae: (1) ass. Melico nutantis– Piceetum abietis K.-Lund 1981, (2) ass. Maianthemo bifolii–Piceetum abietis Korotkov 1991, (3) ass. Asaro europaei–Piceetum obovatae Martynenko 2009 nov. prov., and (4) ass. Equiseto scirpoidis–Piceetum obovatae Martynenko et Zhigunova 2004 (Martynenko 2009). The subsection brings together communities of dark and light coniferous forests, decidious small-leaved and mixed coniferous-small-leaved forests. Small boreal herbs and ferns, such as Maianthemum bifolium, Gymnocarpium dryopteris, Oxalis acetosella, etc., prevail in the field layer while Vaccinium myrtillus can co-dominate sometimes; however, the coverage of small herbs is always higher than the coverage of dwarf shrubs. The nemoral species Melica nutans, Aegopodium podagraria, Asarum europaeum and others occur in low abundance. The bottom layer is well developed, but cover is not more than 40–50%; it mainly consists of boreal species, such as Pleurozium schreberi and Hylocomium splendens; Rhytidiadelphus triquetrus occurs rarer or with a lower abundance. Green moss  – small boreal herb spruce(−fir) forests (Piceeta (Piceeto-Abieta) parviherboso-­hylocomiosa) are distributed over the entire hemiboreal region. They occur mainly on slopes and flat areas on watersheds, and on slopes of different exposure and steepness in lowlands and foothill areas (Sokolov 1928; Vasilevich 1983, 2004a, b; Romanovsky 2002; Martynenko et al. 2007, 2008b). Soils are similar to the soils in green moss – dwarf shrub spruce forests (podzolics, sod-podzolics and podzols on sandy substrate), but Dystric Cambisols and Dystric Arenosols can be also found. Crown cover varies from 40 to 80%. Picea abies or P. obovata dominate in the west and in the east, respectively. Abies sibirica occurs in minor admixture in the east. Betula pubescens and B. pendula, rarely Pinus sylvestris and Populus tremula, occur in the stands; Quercus robur can be found in the south; Alnus incana and Padus avium very rarely occur. Picea spp. often form the second and third tree layers in the forest canopy. Cover of the understorey is 10–30%; Sorbus aucuparia is common; Daphne mezereum, Lonicera xylosteum and Frangula alnus can be found in low abundances. Undergrowth of Picea spp. prevails; undergrowth of Quercus robur, Tilia cordata and Acer platanoides sometimes occurs in the south of the region. Cover of the field layer is 30–80%. The small boreal herbs and fern Oxalis acetosella, Maianthemum bifolium and Gymnocarpium dryopteris often co-­ dominate; Equisetum sylvaticum and Calamagrostis arundinacea dominate more rarely and Linnaea borealis sometimes dominates. Vaccinium myrtillus can form a dense cover in some patches. Boreal small herbaceous plants, such as Luzula pilosa, Rubus saxatilis and Trientalis europaea, often occur with low abundances. The nemoral species Convallaria majalis, Stellaria holostea, Aegopodium podagraria and Asarum europaeum occasionally occur, also in low abundances. In the east of the hemiboreal region, in the lowlands and foothills of the Urals, Calamagrostis arundinacea can dominate in equal proportion with the boreal small herbs. Moreover, nemoral species, such as Asarum europaeum, Actaea spicata, Adenophora lilifolia, Aegopodium podagraria, Carex digitata, C. rhizina, C. macroura, Pulmonaria obscura, Poa nemoralis, Viola mirabilis, and V. collina, and meadow species, such as Cerastium pauciflorum and Hieracium umbellatum, more

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often occur in the east than in the west. Asplenium trichomanes, Cystopteris fragilis, Tephroseris integrifolia and Campanula rotundifolia are common on rocky outcrops (Zhigunova 2007). Characteristic of the eastern green-moss  – small boreal herb spruce(−fir) forests is the high constancy of Equisetum scirpoides, Atragene speciosa (sibirica) and Carex alba. The bottom layer covers 45–90%; the boreal green mosses Pleurozium schreberi, Hylocomium splendens, Dicranum scoparium, Rhytidiadelphus triquetrus and Ptilium crista-castrensis codominate. The hemiboreal green moss Rhodobryum roseum is common in the south. Green moss – small boreal herb pine forests (Pineta parviherboso-hylocomiosa) within the west and centre of the hemiboreal region are described from well-drained habitats such as river terraces of moraine plains, gently undulating surfaces and gentle slopes of watersheds consisting of fluvioglacial sands with underlain moraine loams at a depth of less than 2 m (Kolomyts et al. 1993). Illuvial-humic ferrugenous podzols (Haplic Podzols) and podburs (Entic Podzols) prevail; Dystric and Albic Arenosols can be found. In the east of the region these forests are located at middle parts of steep slopes with a northern, north-western or north-eastern exposition and poor, stony soils. Crown cover is 50–80%. Pinus sylvestris dominates with an admixture of Picea abies or P. obovata, Betula pendula, B. pubescens, sometimes Populus tremula and Larix sibirica in the east (Sokolov 1931). Cover of the understorey is 5–15%: Frangula alnus, Juniperus communis, Lonicera xylosteum, Rosa majalis, Viburnum opulus and Sorbus aucuparia occur throughout the entire region, whereas Chamaecytisus ruthenicus, Caragana frutex and Atragene sibirica occur in the east. Undergrowth of Picea spp. and rarely Tilia cordata occur in the west and centre of the region (Sokolov 1931); undergrowth of Abies sibirica, Quercus robur, Padus avium and Tilia cordata is quite common in the east, while Acer platanoides and Corylus avellana occasionally occur there. Cover of the field layer varies from 20 to 90%. Small boreal herbs, such as Oxalis acetosella, Maianthemum bifolium and Rubus saxatilis, codominate with Vaccinium myrtillus. Calamagrostis epigeios sometimes dominates; it is a good indicator of ground fire; Calamagrostis arundinacea often occurs. On the whole, boreal small herbs are very abundant whereas nemoral species, such as Melica nutans, Aegopodium podagraria, Asarum europaeum and Stellaria holostea, occur in low abundances and the tall nemoral herbs Adenophora lilifolia, Lupinaster pentophyllus, Adonis sibirica and Pleurospermum uralense can be found in Pinus sylvestris forests due to the good light conditions. Cover of the bottom layer is 50–80%; Pleurozium schreberi dominates with an admixture of Rhytidiadelphus triquetrus, Hylocomium splendens and Dicranum scoparium (Martynenko et al. 2007, 2008a, b; Martynenko 2009). Green moss  – small boreal herb larch forests (Lariceta parviherboso-­ hylocomiosa) are described from limestones in the low mountains and foothills of the Ural Mts. Crown cover is 40–60%; Larix sibirica dominates with an admixture of Picea obovata, Pinus sylvestris and Betula pubescens. Cover of the understorey is 10–30%; it consists of Abies sibirica, Betula pubescens, Picea obovata, Tilia cordata and Sorbus aucuparia together with some shrubs as Lonicera pallasii,­

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L. xylosteum and the liana Atragene sibirica. Cover of the field layer is 25–35%; Maianthemum bifolium, Gymnocarpium dryopteris and Rubus saxatilis occur with high abundances; several nemoral species, such as Paris quadrifolia, Carex digitata, etc., often occur. Cover of the bottom layer is 75–95%, and Pleurozium schreberi and Hylocomium splendens are the main dominants (Degteva et al. 2001). Green moss  – small boreal herb aspen forests (Populeta parviherbosa-­ hylocomiosa) are described from the plain parts of the Komi Republic. Cover of the overstorey is 60–70%. Populus tremula dominates in the upper layer with an admixture of Picea obovata, Pinus sylvestris and Betula pubescens. Picea obovata forms the second tree layer in the forest canopy. Cover of the understorey is 10–30%: Picea obovata dominates and Populus tremula rarely occurs; Lonicera pallasii, Sorbus sibirica and Rosa acicularis often occur. The field layer covers 40–95%. Small boreal herbaceous species such as Gymnocarpium dryopteris and Oxalis acetosella dominate; Vaccinium myrtillus, Luzula pilosa and Melampyrum pratense often occur with the nemoral species Stellaria holostea, Melica nutans, Millium effusum, Geranium sylvaticum, etc. Cover of the bottom layer varies from 40–60% up to 90–95%. Pleurozium schreberi and Hylocomium splendens dominate; Polytrichum commune, P. juniperinum and Rhytidiadelphus triquetrus occur (Degteva et al. 2001). Subsection of green moss – piny herb forests includes plant communities of the following two associations of the union Dicrano–Pinion: (1) ass. Vaccinio vitis-idaeae–Pinetum Sokołowski 1980, subass. V. v.-i.–P. s. quercetosum roboris Bulokhov and Solomeshch 2003 and (2) ass. Zigadeno sibirici–Pinetum sylvestris Martynenko et Zhigunova 2004. The subsection unites forests dominated in the ground layer by green mosses and herbaceous species of dry and semi-dry habitats. Only forests dominated by Pinus sylvestris are described in this subsection. The following two groups of Pinus sylvestris forests are distinguished here: the group located in the Russian Plain and the group located on piedmont plains of the Ural Mts. The forests of the first group belong to the V. v.-i.–P. s. quercetosum roboris. These forests mostly occur on sandy soils located on flat parts of watersheds and gentle slopes of hills within the Russian Plain (Chernov 1940; Gavrilov and Karpov 1962; Bulokhov and Solomeshch 2003). These forests are floristically poorer than the forests of the second group. Crown cover varies from 20 to 80%. Pinus sylvestris dominates in the stands; Quercus robur, Picea abies and Betula pendula are admixted. Cover of the understorey is 10–15%; it consists of the boreal species Frangula alnus, Sorbus aucuparia and Juniperus communis; Chamaecytisus ruthenicus, which is a typical species of the southern forests dominated by Pinus sylvestris, also often occurs. The piny shrub Genista tinctoria and the mountain shrub Ribes alpinum rarely occur. A sparse undergrowth of Quercus robur, Salix caprea and Alnus incana can be found. Cover of the field layer varies strongly (from 25 to 90%). The northern piny dwarf shrubs and herbs Vaccinium vitis-idaea, Calluna vulgaris, Antennaria dioica, Festuca ovina and Calamagrostis epigeios dominate; Hieracium pilosella and Carex ericetorum occur; the tall boreal herbs Calamagrostis arundinacea and Rubus idaeus also occur together with the nemoral herb Convallaria majalis and spe-

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cies of the southern Pinus sylvestris forests, such as Steris viscaria, Pulsatilla patens, Veronica spicata, Koeleria grandis, Dianthus arenarius and Thymus serpyllum. Cover of the bottom layer is usually high (up to 90%), although in some parts it is not more than 40–60%. The boreal mosses Pleurozium schreberi, Dicranum polysetum and Polytrichum juniperinum dominate; the lichens Cladonia rangiferina, C. gracilis and C. arbuscula occasionally occur. The Pinus sylvestris forests of the second group in this subsection include plant communities of the Zigadeno sibirici–Pinetum sylvestris association; they are mainly described from slopes with a southern, western, and more rarely eastern exposition on the Ufa Plateau where they occupy large areas on sunny, steep, forest-­carrying carbonate slopes along the Ufa River that are protected in order to conserve the river’s water resources (Martynenko et al. 2007, 2008a, b; Rysin and Savelyeva 2008; Martynenko 2009). These forests are floristically rich: they consist of species of dry, semi-dry and medium-moist habitats. Crown cover is 50–70%. There are several tree layers in the forest canopy: Pinus sylvestris dominates in the upper layer with an admixture of Betula spp. and sometimes with participation of Picea obovata; the second layer consists of Pinus sylvestris and Picea obovata and the third layer is formed by the coniferous trees Pinus sylvestris, Picea obovata and Abies sibirica as well as by the broad-leaved trees Quercus robur, Tilia cordata, Acer platanoides and Ulmus glabra. Cover of the understorey is 5–25%; its species composition is diverse: the typical boreal and nemoral species Sorbus aucuparia, Frangula alnus, Lonicera xylosteum and Euonymus verrucosa grow together with the meadow-steppe shrubs Cotoneaster melanocarpus, Chamaecytisus ruthenicus, Caragana frutex and Cerasus fruticosa. The liana Atragene sibirica also occurs in the understorey. Cover of the field layer is 20–50%. A typical feature of these forests is that the species composition of the field layer is very diverse. Rubus saxatilis, Gymnocarpium robertianum, more rarely Calamagrostis arundinacea and Equisetum scirpoides, dominate. Besides small boreal herbs such as Maianthemum bifolium and Orthilia secunda, nemoral herbs such as Aegopodium podagraria, Lathyrus vernus, Melica nutans, Viola collina, Adenophora lilifolia, etc. together with meadow and steppe species such as Campanula rotundifolia, Galium tinctorium, Vincetoxicum albowianum, Seseli krylovii, Lupinaster pentaphyllus and others, often occur. These forests have the highest richness of vascular species in the class Vaccinio–Piceetea Br.-Bl. in Br.-Bl., Sissingh et Vlieger 1939 (Martynenko et  al. 2008a, b; Martynenko 2009). Cover of the bottom layer varies from 50 to 90% (75–80% on average); the boreal mosses Pleurozium schreberi, Hylocomium splendens and Dicranum spp. are the most prominent.

4.1.3  Section: Herb Forests The diagnostic feature of this section is the codomination of boreal and nemoral vascular plants in the ground layer with a minor participation of green mosses. The proportion of boreal species is larger than that of the nemoral ones in the

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forests located in the northern part of the hemiboreal region and vice versa in the southern part. Boreal and nemoral tall herbaceous species also occur in forests of this section and these species dominate in the best preserved coniferous-broadleaved forests. The forests of this section are located on drained areas on watersheds. Generally, these forests have been less disturbed by man than the forests of other sections located in similar relief positions. The section unites forests dominated by the typical species of the class Vaccinio–­ Piceetea Br.-Bl. in Br.-Bl., Sissingh et Vlieger 1939 and the class Querco–Fagetea Br.-Bl. et Vlieger in Vlieger 1937 as well. Different subsections comprise plant communities of different associations and subassociations. The syntaxonomic diversity of these forests is much greater than the diversity of the herb forests located in the boreal region. Subsection of piny-boreal herb forests includes the following two associations of the union Dicrano–Pinion: (1) ass. Antennario dioicae–Pinetum sylvestris Solomeshch et  al. 1992 and (2) ass. Vaccinio vitis-idaeae–Pinetum sylvestris Sokołowski 1980. This subsection unites forests codominated by boreal and piny herbaceous species in the ground layer; the proportion of the nemoral species becomes significant only in the east of the region, in piedmont plains of the Ural Mts (Solomeshch et al. 2002; Martynenko 2009). The moss cover is weakly developed. Only forests dominated by Pinus sylvestris are described in this subsection. Piny-boreal herb pine forests (Pineta pine-boreoherbosa) grow on poor sandy soils located on flat tops of dunes and on slightly elevated flat areas or gentle slopes of outwash plains (Sokolov 1931; Fedorchuk et al. 2005). In the Russian Plain, these forests often change into Pineta sylvestris cladinosa and Pineta sylvestris hylocomioso-cladinosa forests which grow after a fire. Illuvial-humic ferrugenous Podzols (Haplic Podzols) prevail, Dystric and Albic Arenosols also occur. Crown cover is 50–70%. Pinus sylvestris dominates in the overstorey with an admixture of Betula spp. In the east a second tree layer is often developed and it mainly consists of Picea obovata; Pinus sylvestris often occurs with a low abundance; Tilia cordata and Quercus robur also rarely occur there and sporadically also Abies sibirica. Cover of the understorey is 10–20%. It includes undergrowth of Pinus sylvestris in small numbers and Sorbus aucuparia; an undergrowth of Tilia cordata, Quercus robur, Acer platanoides, Picea obovata and Larix sibirica occurs in the east. The shrub layer includes the typical shrubs of coniferous forests, such as Frangula alnus, Sambucus sibirica, Juniperus communis and Chamaecytisus ruthenicus as well as shrubs which are common in broad-leaved forests (Euonymus verrucosa, Lonicera xylosteum, Viburnum opulus, Rosa glabrifolia, rarely Corylus avellana, Daphne mezereum and Rosa majalis). Cover of the field layer is 40–90%. Calamagrostis arundinacea dominates or it co-dominates with Calamagrostis epigeios, Rubus idaeus, R. saxatilis and Convallaria majalis. Piny ferns, dwarf shrubs and herbs, such as Pteridium aquilinum, Chimaphila umbellata, Vaccinium vitis-­

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idaea, Antennaria dioica, etc., and the boreal dwarf shrubs Orthilia secunda and V. myrtillus often occur with low abundances. The nemoral herbs Aegopodium podagraria, Asarum europaeum, Lathyrus vernus, Melica nutans, Poa nemoralis, Pulmonaria obscura, Viola mirabilis and others reach a fair amount of cover in some communities in the east of the region. Cover of the bottom layer is 10–20%; Pleurozium schreberi, Dicranum polysetum, D. scoparium and Polytrichum juniperinum are constantly found with various abundances. Subsection of small boreal herb forests includes plant conmmunities of the ass. Melico nutantis–Piceetum abietis K.-Lund 1981 and ass. Lysimachio vulgaris–­Betuletum pubescentis Bulokhov et Solomeshch 2003 of the union Piceion excelsae (Sokolov 1931; Korchagin and Senjaninova-Korchagina 1957; Nitsenko 1972; Shaposhnikov et  al. 1988; Bibikova 1998; Degteva et  al. 2001; Bulokhov and Solomeshch 2003; Liksakova 2004; Vasilevich and Bibikova 2004; Fedorchuk et al. 2005). This subsection unites forests with relatively poorly developed moss covers (on average between 5 and 30%) and with a predominance of small boreal herbs over the nemoral ones; Oxalis acetosella is abundant in the field layer (Shaposhnikov et al. 1988; Korotkov 1991; Bulokhov and Solomeshch 2003; Zaugolnova and Morozova 2004). The subsection unites dark and light coniferous forests as well as decidious small-leaved forests. The proportion of broad-leaved trees in the overstorey and nemoral herbs in the field layer increases to the south of the hemiboreal region. Small boreal herb spruce forests (Piceeta parviboreoherbosa) are found over the entire hemiboreal region on slightly undulating areas on watersheds and on slopes of river terraces. Sod-pale-podzolic and sod-podzolic soils (Gleyic and Umbric Albeluvisols) prevail, although these forests are found on a variety of soils including illuvial-humic ferrugenous podzols (Haplic Podzols) and podburs (Entic Podzols). Crown cover is 50–80%. Picea spp. dominate in the overstorey, sometimes with an admixture of Pinus sylvestris. Single individuals of Betula pubescens, Quercus robur, Tilia cordata and Populus tremula occur in the stands. Height and age of the trees in the overstorey vary greatly (Korchagin and Senjaninova-Korchagina 1957; Shaposhnikov et  al. 1988; Rechan et  al. 1993; Bulokhov and Solomeshch 2003; Vasilevich and Bibikova 2004), whereas only initial signs of a gap mosaic can be found in the tree canopy (Rechan et al. 1993; Rysin and Savelyeva 2002). Cover of the understorey is 30–70%; Sorbus aucuparia, Corylus avellana, Viburnum opulus, Euonymus verrucosa, Daphne mezereum and Ribes nigrum are common. An undergrowth of Picea spp. occurs most frequently, but an undergrowth of Tilia cordata, Acer platanoides and rarer Quercus robur also occurs; Padus avium and Populus tremula can be also rarely found in the understorey. It has been suggested that the presence or absence of Tilia cordata in the overstorey and in the understory is an indicator of the intensity and the kind of historical anthropogenic impacts in the forested area: complete absence of Tilia cordata indicates a large area of ploughing or fires in the past, because Tilia cordata very poorly regenerates from seed, but it may persist for a long time during logging in the form of vegetative shoots (Smirnova 1994).

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Cover of the field layer is 60–80%; it often appears as a mosaic of separate patches formed by different species or groups of species. Oxalis acetosella usually dominates and the small boreal herbaceous species Rubus saxatilis or Maianthemum bifolium often codominate; the nemoral herb Aegopodium podagraria occasionally codominates. Other small boreal herbaceous species, such as Trientalis europaea, Gymnocarpium dryopteris, etc., the dwarf shrubs Vaccinium myrtillus and V. vitis-­idaea, and nemoral herbs, such as Galeobdolon luteum, Stellaria holostea and Melica nutans, often occur in low abundances. In some areas, the large ferns Dryopteris filix-mas, D. dilatata and D. carthusiana often occur; they usually reach a high abundance under canopy gaps. The spring-flowering perennial herbs Hepatica nobilis and Anemonoides nemorosa occur in the small boreal herb spruce forests only in the west of the region. Cover of the bottom layer is small (5–30%), but sometimes reaches up to 70–90%. The boreal green mosses Pleurozium schreberi and Rhytidiadelphus triquetrus prevail in the patches dominated by the boreal plants, whereas nemoral-boreal and nemoral mosses such as Mnium affine and Brachythecium starkei often occur between nemoral herbs. Small boreal herb pine forests (Pineta parviboreoherbosa) are mainly found on sandy terraces and outwash landscapes. Podzols (Haplic and Umbric Podzols) and podburs (Entic Podzols) prevail; Dystric and Albic Arenosols also occur. Crown cover is 50–70%. Pinus sylvestris prevails in the overstorey with an admixture of Betula pubescens, B. pendula and Picea spp.; single individuals of Tilia cordata, Quercus robur and Populus tremula can also be found. Cover of the understorey is 50–70%. Frangula alnus, Sorbus aucuparia and Juniperus communis always occur in these forests; Corylus avellana and Euonymus verrucosa always occur in the south of the region. The undergrowth of Picea spp., Betula spp., Tilia cordata and Acer platanoides is well developed. The field layer covers 40–80% and boreal species, such as Vaccinium myrtillus, Maianthemum bifolium, Luzula pilosa, Rubus saxatilis and rarely Oxalis acetosella, dominate, while Calamagrostis arundinacea constantly occurs. The nemoral species Convallaria majalis and Stellaria holostea are common, Carex pilosa occurs sometimes. Cover of the bottom layer is 5–20%; the boreal mosses Pleurozium schreberi, Hylocomium splendens and Rhytidiadelphus triquetrus occur (Rysin and Savelyeva 2002; Fedorchuk et  al. 2005). Small boreal herb aspen forests (Populeta parviboreoherbosa) usually develop over the entire hemiboreal region after felling of small boreal herb spruce forests. Just as those forests, small boreal herb aspen forests are located on slightly undulating areas on watersheds and slopes of river terraces, often on moraine loams or mixed moraine sediments with soils of different texture (Nitsenko 1972; Bibikova 1998; Degteva et al. 2001; Liksakova 2004). Crown cover is 70–80%. Populus tremula dominates in the overstorey with an admixture of Betula pubescens, B. pendula and Picea spp.; Quercus robur frequently occurs, Tilia cordata can be found. Cover of the understorey is 15–30%; it consists of Sorbus aucuparia and Padus avium; Viburnum opulus and Rosa majalis

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also rarely occur; Lonicera pallasii occurs in the east (Degteva et  al. 2001). Undergrowth of Picea spp., Betula spp. and Quercus robur is common; Acer platanoides can be found. Cover of the field layer is 60–80%; small boreal herbs, such as Oxalis acetosella, Rubus saxatilis, Maianthemum bifolium, Luzula pilosa, etc., dominate and Vaccinium myrtillus occurs with a low abundance. The proportion of nemoral herbs is larger compared to that in the coniferous forests: Pulmonaria obscura, Convallaria majalis and Aegopodium podagraria often occur. The large ferns Dryopteris dilatata and Athyrium filix-femina occur with high abundances and the tall herb Aconitum septentrionale can be found in the small boreal herb aspen forests dominated by Oxalis acetosella in the ground layer (Bibikova 1998). The bottom layer covers 5–15%; Plagiomnium cuspidatum often occurs, the boreal mosses Pleurozium schreberi, Dicranum scoparium, Climacium dendroides, etc. rarely occur. Small boreal herb birch forests (Betuleta parviboreoherbosa) are formed after felling of small boreal herb spruce and pine forests on moraine and moraine-­outwash plains, sometimes on slightly gleyed soils (Nitsenko 1972; Degteva 2001). Crown cover is 60–70%. Betula pubescens dominates, Picea spp. is often common and sometimes co-dominates; occasionally there is an admixture of Populus tremula and Pinus sylvestris. Cover of the understorey is 10–30%: Sorbus aucuparia and Padus avium are prominent; Viburnum opulus, Corylus avellana, Rosa majalis and Lonicera pallasii (in the east) can be found. Picea spp. are common in the undergrowth; Abies sibirica occurs in the east; Quercus robur, Acer platanoides, Ulmus glabra and sporadically Alnus incana and Salix cinerea also can be found in the understorey. Cover of the field layer is 60–80%; small boreal herbs dominate with an admixture of nemoral species: Oxalis acetosella usually dominates; Rubus saxatilis, Calamagrostis arundinacea and Convallaria majalis sometimes dominate; the meadow herb Fragaria vesca, the boreal herbs Maianthemum bifolium, Trientalis europaea, and the climber Atragene sibirica as well as the nemoral herbs Melica nutans, Stellaria holostea, Galeobdolon luteum and Asarum europaeum often occur. Vaccinium myrtillus can be found with varying abundance. Cover of the bottom layer is 10–20%, Pleurozium schreberi, Dicranum scoparium and Plagiomnium cuspidatum occur. Small boreal herb grey alder forests (Alneta incanae parviboreoherbosa) are described from the east of the hemiboreal region. Just as small boreal herb aspen forests, forests dominated by Alnus incana in the overstorey are formed after felling of the boreal small herb spruce forests and they are gradually replaced by spruce forests after the prolonged termination of logging (Nitsenko 1972; Degteva 2001). Nowadays, Populus tremula forests are more widespread than the Alnus incana forests, which occupy wetter relief positions. However both species potentially can grow over the entire area under average moisture conditions (Shimanyuk 1957; Smirnova 2004). Crown cover is 80–90%; Alnus incana dominates with a small admixture of Picea obovata and Abies sibirica; Salix caprea and S. pentandra sometimes occur with a low abundance. Cover of the understorey is 10–40%: Juniperus communis, Lonicera pallasii, Rosa majalis, Padus avium, Sorbus aucuparia and others often

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occur; in the undergrowth Picea obovata is plentiful and Alnus incana is rare. Cover of the field layer varies from 15 to 65%. Oxalis acetosella dominates; Dryopteris carthusiana or Rubus idaeus sometimes co-dominate. The small boreal plants Gymnocarpium dryopteris, Maianthemum bifolium, Linnaea borealis, Trientalis europaea, etc. often occur with different abundances. Cover of the bottom layer is 5–30%. Pleurozium schreberi, Climacium dendroides and Plagiomnium medium are common on the soil; species of the genera Brachythecium, Drepanocladus and Plagiothecium are present on decaying wood. Subsection of boreal-nemoral herb forests includes plant communities of the following three associations of the union Querco roboris–Tilion cordatae Bulokhov et Solomeshch 2003: (1) ass. Trollio europaei–Quercetum roboris Korotkov 1991, (2) ass. Corylo avellanae–Pinetum sylvestris Bulokhov et Solomeshch 2003, and (3) ass. Rhodobryo rosei–Piceetum abietis Korotkov 1986 and the following three associations of the union Aconito septentrionalis–Piceion obovatae Solomeshch et al. 1993 ex Martynenko et al. 2008b: (1) ass. Chrysosplenio alternifolii–Piceetum obovatae Martynenko et Zhigunova 2007, (2) ass. Carici rhizinae–Piceetum obovatae Solomeshch et  al. 1993, and (3) ass. Frangulo alni– Piceetum obovatae Solomeshch et  al. 1993 (Korotkov and Morozova 1986; Korotkov 1991; Bulokhov and Solomeshch 2003; Martynenko et al. 2007, 2008a, b). All these associations belong to the Querco–Fagetea class, but to two different orders: Fagetalia sylvaticae Pawłowski, Sokołowski et Wallish. 1928 and Abietetalia sibiricae (Ermakov in Ermakov et al. 2000) Ermakov 2006. The subsection includes forests characterized by a complex composition of the field layer in which nemoral as well as boreal species occur with high abundances: Aegopodium podagraria, Carex pilosa, Galeobdolon luteum, Mercurialis perennis, Oxalis acetosella, Rubus saxatilis, Maianthemum bifolium, etc. often co-dominate, Vaccinium myrtillus often occurs. The overstorey, as a rule, also consists of several species of coniferous and broad-leaved decidious trees. The moss cover is weakly developed and comprises a mixture of the boreal mosses Pleurozium schreberi, Hylocomium splendens, etc. and hemiboreal mosses such as Rhodobryum roseum, Brachythecium oedipodium, Plagiomnium cuspidatum, etc. (Zaugolnova et  al. 2001; Vasilevich 2004b; Zaugolnova and Morozova 2004). An important feature of these forests is the presence of perennial herbaceous plants with pre-summer-green leaves (“ephemeroids” in scientific Russian); these species form leaves at the end of winter or early in spring. In spring, the leaves are green and the plants flower. After that, the plants go dormant. Anemonoides nemorosa, A. ranunculoides, Corydalis solida, etc. occur in the boreal-nemoral herb forests in spring (Zaugolnova et al. 2001). It has to be pointed out that ephemeroids are not fully taking into account in phytosociological reviews, because most of relevés are made in mid-summer, when these plants already went dormant and their aboveground parts disappeared. Boreal-nemoral herb spruce(-fir)  – broad-leaved forests (Piceeta / Abieto-­ Piceeta / Tilieto-Piceeta / Abieto-Tilieto-Piceeta/Querceto-Piceeta boreo-­ nemoroherbosa) were described from moderately moist and well-drained habitats located on watersheds and slopes of river terraces on loamy and sandy-loamy soils

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(Solomeshch et al. 1993; Zaugolnova and Morozova 2004). Sod-podzolics (Albic Luvisols, Umbric Albeluvisols) prevail; podzolics (Haplic Albeluvisols) and brown soils (dystric and eutric Haplic Cambisols) occur more rarely. Crown cover varies form 30 to 80%. Picea abies predominates in the western and in the central parts of the hemiboreal region and Picea obovata with Abies sibirica co-dominate in the east. Betula pubescens, B. pendula, Populus tremula and Alnus incana as well as the broad-leaved trees Tilia cordata, Ulmus laevis and Acer platanoides together with Quercus robur in the south are common in the overstorey. Often several tree layers can be distinguished in the forest canopy; the proportion of coniferous and broad-leaved trees in these layers widely varies: from the domination of dark coniferous trees to the equal participation of dark coniferous and broad-­ leaved trees. Cover of the understorey varies from 30 to 60%. It includes Corylus avellana, Sorbus aucuparia, Frangula alnus, Lonicera xylosteum, Rosa majalis, Viburnum opulus and Daphne mezereum. The undergrowth mainly consists of Picea spp.; an abundant undergrowth of Tilia cordata and Acer platanoides sometimes occurs in the south of the region; Betula spp., Padus avium, Alnus incana and rarely Quercus robur can be also found in the understorey. An undergrowth of Picea spp. and broad-leaved trees occurs in canopy gaps or in tree groups formed by Betula spp. and Populus tremula (Sokolov 1931; Khomutova 1941; Yarutkin 1981; Shaposhnikov et al. 1988). Cover of the field layer is 80–90%. High patchiness is a feature of the field layer in these forests: nemoral and boreal herbs and large ferns create patches of different species and different abundances; spatial mosaics defined by the specific impacts of crowns of coniferous and broad-leaved trees are also observed (Popadyuk et  al. 1999; Shirokov 2004; Grozovskaya et  al. 2015). The nemoral plants Aegopodium podagraria, Carex pilosa, Galeobdolon luteum, etc. and the boreal species Oxalis acetosella, Maianthemum bifolium, more rarely Rubus saxatilis and Vaccinium myrtillus, co-dominate. Calamagrostis arundinacea co-­ dominates on sandy soils. Spring-growing and -flowering perennial herbs, such as Anemonoides ranunculoides, A. nemorosa, etc. can be found in spring. The large ferns Athyrium filix-femina, Dryopteris filix-mas, D. expansa and D. carthusiana mightily grow in canopy gaps and in patches of treefalls with uprooting or on small clearings as well. Cover of the bottom layer is 5–10%. The composition of the moss vegetation is diverse: the boreal species Pleurozium schreberi, Dicranum scoparium, Hylocomium splendens, etc. and hemiboreal species such as Rhodobryum roseum, Brachythecium oedipodium, B. salebrosum and Plagiomnium cuspidatum often occur with low abundances (Rechan et al. 1993; Rysin and Savelyeva 2002). Boreal-nemoral herb pine forests with linden and oak (Querceto/Tilieto-Pineta boreo-nemoroherbosa) occupy sandy terraces of rivers. Dystric Arenosols and Entic Podzols are common; Haplic Podzols also occur. Crown cover is 60–80%. Pinus sylvestris dominates in the overstorey with an admixture of Tilia cordata and Quercus robur in the western and central parts of the region and with an admixture of Picea obovata and Abies sibirica in the east. Tilia cordata occurs in the second tree layer of the forest canopy. Cover of the understory is 60–70%: Corylus avellana, Sorbus aucuparia, Lonicera xylosteum, Euonymus verrucosa, Daphne mezereum, Frangula alnus, Viburnum opulus and Amelanchier spicata co-dominate.

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Undergrowth of Tilia cordata is abundant. Cover of the field layer is 40–60%: Oxalis acetosella often dominates. Carex pilosa, C. digitata and Convallaria majalis dominate here and there. The nemoral species Aegopodium podagraria, Stellaria holostea, Paris quadrifolia, Melica nutans, Lathyrus vernus, Carex rhizina, Geum urbanum and Asarum europaeum as well as the boreal species Luzula pilosa, Trientalis europaea, Maianthemum bifolium, Orthilia secunda and Rubus saxatilis often occur. The large fern Dryopteris carthusiana is common. The piny species Pteridium aquilinum and Polygonatum odoratum also often occur. Cover of the bottom layer is 1–5%: the moss cover is low; hemiboreal species, such as Brachythecium oedipodium, Hypnum pallescens, Plagiomnium cuspidatum, Sanionia uncinata and Lophocolea heterophylla, mainly occur on dead, fallen wood and on the bases of tree trunks (Rysin 1969; Rysin and Savelyeva 2008). Boreal-nemoral herb aspen forests (Populeta boreo-nemoroherbosa) are described from the north-west of the hemiboreal region (Korotkov 1991; Bibikova 1998). They occupy various relief positions in watershed areas, from the tops of the hillocks to their bottoms. They occur adjacent to the moist Alnus incana forests located at the very bottoms of this hilly habitat, although, as we mentioned above, probably, human impacts forced Alnus incana down on the wetter relief positions. Soils in the boreal-nemoral herb aspen forests vary in texture (sandy, sandy loam and loam), in moisture and richness: from weakly podzolic to brown forest soils (Korotkov 1991). Crown cover is 60–80%, but the forests are relatively light due to the dominance of small-leaved Populus tremula trees which reach up to 35 m in height and are about 80 years old. Betula pubescens, Pinus sylvestris and Picea abies also occur in the overstorey as an admixture. Sometimes the broad-leaved trees Quercus robur, Tilia cordata and Acer platanoides can be found (Bibikova 1998). Cover of the understorey varies from 10 to 60%. Sorbus aucuparia, Frangula alnus, Lonicera xylosteum, Rosa majalis, Padus avium, rarely Corylus avellana (Bibikova 1998) as well as the nemoral species Lonicera xylosteum and Daphne mezereum occur (Korotkov 1991). Undergrowth of Picea abies, Alnus incana and Populus tremula is common. Undergrowth of broad-leaved trees is weak or absent. Cover of the field layer is usually low, but sometimes reaches 75–85%. The boreal species Rubus ­saxatilis, Calamagrostis arundinacea and Oxalis acetosella dominate. The nemoral species Aegopodium podagraria, Galeobdolon luteum, Convallaria majalis and Stellaria holostea occur with varying constancy and abundance. The nemoral herbs Anemonoides nemorosa and Hepatica nobilis were also observed in the Valdai Hills (Korotkov 1991). Boreal species such as Maianthemum bifolium, Trientalis europaea, Gymnocarpium dryopteris and Vaccinium myrtillus often occur. Pteridium aquilinum sometimes dominates (Bibikova 1998) and that indirectly testifies to the post-fire origin of those boreal-nemoral herb aspen forests. Cover of the bottom layer is 5–10%: mosses occur on the ground in separated patches; they mainly grow on dead, fallen wood and on the bases of tree trunks. Pleurozium schreberi, Rhytidiadelphus triquetrus and Plagiomnium cuspidatum are most common. These forests are also quite rich in epiphytic mosses and lichens (Korotkov 1991).

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Subsection of nemoral herb forests unites forests dominated by species that are characteristic of the class Querco–Fagetea Br.-Bl. et Vlieger in Vlieger 1937. This subsection includes plant communities of the following five associations: (1) ass. Mercurialo perennis–Quercetum roboris Bulokhov et Solomeshch 2003 (= Querco roboris–Tilietum cordatae Laivinsh 1986 ex Laivinsh in Solomeshch et al. 1993); (2) ass. Trollio europaei–Quercetum roboris Korotkov 1991; (3) ass. Tilio cordatae–Pinetum sylvestris Martynenko et  al. 2008 prov.; (4) ass. Euonymo verrucosae–­Pinetum sylvestris Martynenko et al. 2007, and (5) ass. Alnetum incanae Lüdi 1921 (= Alno incanae–Padetum avii K.-Lund 1971) (Bulokhov and Solomeshch 2003; Martynenko et  al. 2007, 2008a, b). The first two associations belong to the union Querco roboris–Tilion cordatae Bulokhov et Solomeshch 2003; the next two belong to the union Aconito septentrionalis–Tilion cordatae Solomeshch et al. 1993 and the last association belongs to the union Alnion incanae Pawłowski, Sokołowski et Wallish. 1928. Communities of the first association, the Mercurialo perennis–Quercetum roboris, are widely distributed and occur over the entire hemiboreal region up to the Ural Mts. The second association, the Trollio europaei–Quercetum roboris, occurs only in the southern taiga in the western part of the hemiboreal region (Zaugolnova and Braslavskaya 2003; Zaugolnova and Morozova 2004). Communities of the third and forth associations, the Tilio cordatae–Pinetum sylvestris and Euonymo verrucosae–Pinetum sylvestris, mainly occur on the western macroslope of the Ural Mts. And the forests of the fifth association, the Alnetum incanae, are located on steep slopes of ravines and in river valleys in different parts of the region. Several nemoral species always dominate in the understoreys of the forests of this subsection. The proportion of boreal plants does not exceed 10–15% in the ground layer; the moss layer is very weakly developed. Sping-growing and -flowering perennial herbs, such as Anemonoides spp., Corydalis spp., Gagea spp., etc., often occur with high abundances in the spring in forests dominated by broadleaved trees or (sometimes) by Betula spp. in the overstorey. In general, the forests of this subsection that are little affected by human impacts are dominated by the broad-­leaved trees Quercus robur, Tilia cordata, Fraxinus excelsior, Ulmus glabra and Acer platanoides with constant participation of Picea spp. in the overstorey (Samokhina 1997; Shirokov 2004). Forests formed after anthropogenic disturbances such as logging or agricultural usage of the area (ploughing, livestock grazing, etc.) usually have one dominant species in the overstorey and a reduced number of nemoral species in the ground layer (in case of a limited influx of seeds of broad-­ leaved trees and nemoral herbaceous plants) (Lugovaya 2008). Populations of spring-growing and -flowering perennial herbs are especially affected by ploughing due to their very slow recovery after total destruction (Korotkov 2000). Nemoral herb spruce forests with oak and linden (Piceeta nemorosa) are described from the Russian Plain where they occupy slightly undulate areas on watersheds with a deep groundwater table (Kiseleva 1971; Iljinskaja et  al. 1982; Savelyeva 2000). Sod-podzolics (Albic and Haplic Luvisols, Umbric Albeluvisols) prevail on moraine loams and mixed moraine deposits, brown soils (dystric and

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eutric Haplic Cambisols) also occur. Dystric Arenosols prevail on sandy substrates, Podzols (Entic and Umbric) also occur there. Crown cover is 70–80%; Picea abies prevails in the overstorey with an admixture of Quercus robur, Tilia cordata, Betula pubescens, B. pendula and Populus tremula. Stands are usually even-aged; trees are from 70 to 100–120 years old in different communities (Kiseleva 1971). Tree species composition in different stands varies greatly depending on the history of human impacts in the specific areas. For example, it was shown that in the hemiboreal region, nemoral herb spruce forests often develop from birch forests which had established after the felling of nemoral herb broad-leaved or mixed forests and which were subsequently invaded by spruce (Geltman 1982; Rysin and Savelyeva 2002). Furthermore, modern nemoral herb spruce forests with oak are often old plantations; they are widespread in the south of the hemiboreal region (Iljinskaja et al. 1982, 1985; Korotkov 2000). Cover of the understorey varies from 10 to 30 and more percent depending on tree density. Corylus avellana, Lonicera xylosteum, Sorbus aucuparia, Sambucus racemosa and Frangula alnus often occur. An undergrowth of Picea abies, Quercus robur, Acer platanoides, Tilia cordata and Populus tremula occurs and grows well in canopy gaps. A suppressed undergrowth of Quercus robur can survive not more than 20  years under a tree canopy and it shows a growth spurt when the light increases due to large canopy gaps (Kiseleva 1971; Rechan et al. 1993). The field layer covers 80–90%. The small boreal plants Oxalis acetosella, Rubus saxatilis, Equisetum sylvaticum and Gymnocarpium dryopteris dominate under the dense cover of young individuals of Picea abies. The boreal species are replaced by the nemoral species Galeobdolon luteum, Carex pilosa, Aegopodium podagraria, Mercurialis perennis and others during the development of the tree stands owing to the withering away of spruce individuals and the thinning of the canopy (Kiseleva 1965, 1971; Savelyeva 2000). The large ferns Athyrium filix-femina, Dryopteris filix-mas and D. carthusiana occur in the canopy gaps; meadow species occur under groups of Betula spp. and Populus tremula individuals. Generally, nemoral herbs dominate in the ground layer forming the following patch mosaics: Carex pilosa dominates on dry, poor and eroded soils; Aegopodium podagraria dominates on wetter and richer soils and Mercurialis perennis prevails on the richest well-­ moistened and well-drained soils (Savelyeva 2000). Cover of the bottom layer is low and varies from a complete absence to 3–5% coverage. The boreal mosses Pleurozium schreberi, Dicranum scoparium and Hylocomium splendens mainly occur; hemiboreal species of the genera Brachythecium and Plagiomnium occasionally occur. Nemoral herb broad-leaved forests with spruce (Querceto-Piceeta, Tilieto-­ Piceeta nemorosa) are described from the Russian Plain; they occur on elevated and flat areas of watersheds, on slopes of river terraces and ravines (Korchagin and Senjaninova-Korchagina 1957; Kurnaev 1968; Iljinskaja et  al. 1985; Korotkov 1991; Rechan et al. 1993; Vasilevich 2001; Bulokhov and Solomeshch 2003). Soils are the same as in the nemoral herb spruce forests: sod-podzolics prevail on moraine loams and mixed moraine deposits, brown soils also occur there; Dystric Arenosols and Podzols occur on sandy substrate.

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Crown cover is 70–80%; there are two or three tree layers in the forest canopy. Tilia cordata, Quercus robur, Acer platanoides and sometimes Fraxinus excelsior co-dominate; Picea abies (Picea obovata in the east) always occurs. Ulmus glabra and Padus avium are found in wetter habitats. Betula pendula, B. pubescens and Populus tremula are common as an admixture. Such mixed stands with broad-leaved and small-leaved deciduous trees, and dominated by nemoral herbs in the ground layer, are usually formed after logging; Picea spp. also appears there, especially under more moist soil conditions (Iljinskaja et al. 1985). Cover of the understory is 30–50% and varies in composition. Corylus avellana often dominates; Sorbus aucuparia, Frangula alnus, Lonicera xylosteum and Euonymus verrucosa often occur. Undergrowth of Tilia cordata, Acer platanoides and Ulmus glabra is often found; Picea spp. also occur; undergrowth of Quercus robur rarely occurs in glades and canopy gaps. Cover of the field layer varies significantly (from 30 to 95%) in dependence of the cover of the understorey. Aegopodium podagraria, Carex pilosa, Galeobdolon luteum, Mercurialis perennis and Athyrium filix-femina often dominate; Calamagrostis arundinacea prevails on sandy soils. Some boreal herbaceous species, such as Oxalis acetosella, Maianthemum bifolium, Luzula pilosa, Trientalis europaea, Equisetum sylvaticum, etc., can be found in low abundances. The spring-­ growing and -flowering perennial herbs Anemonoides ranunculoides, sometimes A. nemorosa, Corydalis intermedia, C. solida, rarely C. cava, Gagea lutea and Ficaria verna, are often found in spring. Mosses cover up to 10% of the bottom layer. Atrichum undulatum, Eurhynchium hians, Cirriphyllum piliferum and Plagiomnium cuspidatum often occur on the ground; species of the genera Brachythecium, Plagiomnium and Rhizomnium occur on dead, fallen wood. Epiphytic mosses are mainly located on trunks of Tilia cordata and Populus tremula. In the southern taiga there are also epiphytic lichens in these forests (Korotkov 1991; Zaugolnova and Braslavskaya 2003). Piny-nemoral herb pine forests (Pineta xeromesophyto-nemorosa) are described from the lower and middle parts of the slopes of southern, south-eastern and south-­ western exposures (Sokolov 1931; Solomeshch et al. 1992; Martynenko et al. 2007; Martynenko 2009). The slopes generally range from 5° to 15°, but can reach a steepness of 35° – 45°. Soils are relatively rich, moderately moist and well-lit by the sun and sometimes have outcropping stones; soils are incompletely developed, but have a relatively high fertility and moisture content due to the rich carbonate rocks. Crown cover of the overstorey varies from 40 to 90%. Pinus sylvestris dominates in the overstorey with a small admixture of Betula pendula. Trees with well-­ developed crowns reach 22–30 m in height; their trunk diameter varies from 28 to 64 cm (Martynenko 2009). Tilia cordata with a small participation of Betula spp. usually form the second and third tree layers in the forest canopy. Undergrowth of Tilia cordata, Acer platanoides, Quercus robur and Betula pendula is common; single individuals of Ulmus glabra also occur. Abies sibirica and Picea obovata often occur in the understorey in the east of the region; sometimes they reach the second and rarely the first tree layer in the forest canopy. Cover of the shrub layer is small (0–5%), but sometimes reaches 15–25%. It consists of the mesophilous shrubs Euonymus verrucosa, Viburnum opulus, Lonicera xylosteum, Rosa majalis and

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Frangula alnus as well as the more xerophilous shrubs Caragana frutex, Chamaecytisus ruthenicus and Cerasus fruticosa. Cover of the field layer varies from 30 to 80%. Usually several species of different ecological-coenotic groups dominate in the field layer. The xeromesophilous grasses Calamagrostis arundinacea and C. epigeios may dominate. The nemoral species Aegopodium podagraria, Carex pilosa, Carex rhizina, Brachypodium pinnatum and Stellaria holostea often dominate and Asarum europaeum, Pulmonaria obscura, Lathyrus vernus, Viola collina, V. mirabilis and Pulmonaria mollis often occur. Beside spring- and summer-growing and -flowering perennial herbs of medium size, nemoral tall herbs, such as Adenophora lilifolia, Digitalis grandiflora, Stachys officinalis and Lathyrus pisiformis grow in these forests. The boreal species Carex macroura, Rubus saxatilis and Pleurospermum uralense often occur with low abundances and Maianthemum bifolium, Luzula pilosa, Cerastium pauciflorum and Orthilia secunda can be rarely found. Cover of the bottom layer is low: it sometimes reaches 3–5%, but its species composition is rather rich. The boreal mosses Pleurozium schreberi, Dicranum scoparium and Hylocomium splendens as well as the nemoral and hemiboreal mosses Sciuro-hypnum (Brachythecium) reflexum, Brachythecium salebrosum, Callicladium haldanianum, etc. are found. Various epiphytic lichens occur: Hypogymnia physodes, Vulpicidia pinastri and Parmelia sulcata are the most common species (Zaugolnova and Morozova 2004; Martynenko et al. 2007). Nemoral herb broad-leaved forests with pine (Pineto-Querceta nemorosa) are described from sandy river terraces located on the Russian Plain (Zaugolnova and Morozova 2004). Arenosols (Dystric and Eutric) and Podzols (Entic and Umbric) prevail. Crowns cover 60–80% in the overstorey; Tilia cordata dominates with an admixture of Quercus robur, Pinus sylvestris, Betula pubescens and B. pendula; Picea abies also occurs. Cover of the understorey is 5–10%: Viburnum opulus and Sambucus racemosa sporadically occur. Undergrowth of Tilia cordata and Picea abies prevails, but undergrowth of Betula spp. and Populus tremula occasionally occurs. Cover of the field layer is 40–60%. The nemoral species Mercurialis perennis, Carex pilosa, Galeobdolon luteum and Asarum europaeum predominate. The boreal species Calamagrostis arundinacea, Rubus idaeus, Oxalis acetosella, Maianthemum bifolium and Trientalis europaea often occur with low abundances. Small individuals of Quercus robur can be found in the field layer. The bottom layer is practically absent. Nemoral herb broad-leaved forests (Querceta, Tilieta, Querceto-Tilieta nemorosa) are described from terraces and river floodplains on elevated areas with a good drainage; sometimes they occupy elevated parts of watersheds. In the south of the hemiboreal region these forests are common on watersheds and on slopes of river terraces, but they are preserved in small areas only; most of these forests have long been ploughed. These forests rarely occur in the north of the region. Soils vary: sod-podzolics (Albic and Haplic Luvisols, Umbric Albeluvisols), brown soils (eutric Haplic Cambisols), grey forest soils (Greyic Phaeozems, rarely Haplic Phaeozems) occur; soils with a second humic horizon can also be found.

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Crown cover is 70–80% there are two or three tree layers in the forest canopy. Tilia cordata, Quercus robur, Acer platanoides and sometimes Fraxinus excelsior dominate or co-dominate in various proportions. An admixture of the small-leaved trees Betula pendula, B. pubescens and Populus tremula is common. Ulmus glabra and Padus avium occur in wetter habitats. Malus sylvestris can be rarely found (Zaugolnova and Braslavskaya 2003). Cover of the understorey is 30–50%; it is rich in species. Corylus avellana often dominates; Sorbus aucuparia, Frangula alnus, Lonicera xylosteum and Euonymus verrucosa are the most common. Undergrowth of Tilia cordata, Acer platanoides and Ulmus glabra often occurs; undergrowth of Quercus robur can be found in glades and canopy gaps. Cover of the field layer varies significantly from 30 to 95% and depends on the development of the shrub layer. The nemoral species Aegopodium podagraria, Carex pilosa, Galeobdolon luteum, Mercurialis perennis and sometimes Galium odoratum dominate. The nitrophilous fern Athyrium filix-femina can also dominate under wet conditions; the boreal tall herb Calamagrostis arundinacea dominates on sandy soils. The small boreal herbs Oxalis acetosella, Maianthemum bifolium, Luzula pilosa, Trientalis europaea, Equisetum sylvaticum, etc. occur with low abundances. The spring-growing and -flowering perennial herbs Anemonoides nemorosa, A. ranunculoides, Corydalis intermedia, C. cava, C. solida, Gagea lutea and Ficaria verna often occur in spring (Kurnaev 1968; Iljinskaja et al. 1985; Vasilevich 2001). Cover of the bottom layer is low (1–5%); Atrichum undulatum, Eurhynchium hians, Cirriphyllum piliferum and Plagiomnium cuspidatum are most common on the ground; species of genera Brachythecium, Plagiomnium and Rhizomnium are found on dead, fallen wood (Zaugolnova and Morozova 2004; Kulagin 2007). Nemoral herb birch forests (Betuleta nemorosa) are found on watersheds and slopes of river terraces where they replace nemoral herb broad-leaved forests after logging. Crown cover varies from 40 to 80%. Betula pendula and B. pubescens dominate in the overstorey with a small admixture of Populus tremula and the broad-leaved trees Tilia cordata, Quercus robur and Acer platanoides. Picea abies in the west and P. obovata together with Abies sibirica in the east occur with different abundances. Cover of the understorey is 50–80%, sometimes up to 100%. The understorey is very diverse in species composition. Corylus avellana often dominates; Sorbus aucuparia, Frangula alnus, Lonicera xylosteum and Euonymus verrucosa often occur. Undergrowth of Quercus robur, Tilia cordata, Acer platanoides, Ulmus glabra and Picea abies often occurs in the western and central parts of the region and undergrowth of only Tilia cordata can be found in the east. Cover of the field layer greatly varies, from 30 to 95%, depending on the development of the understorey. Aegopodium podagraria dominates everywhere; Carex pilosa, Galeobdolon luteum and Mercurialis perennis prevail in the western and central parts of the region; Mercurialis perennis often dominates in the richest and moist habitats. The total number of nemoral species is practically the same as in the nemoral herb broad-leaved forests. The small boreal herbs Oxalis acetosella, Maianthemum bifolium, Luzula pilosa, Trientalis europaea and Equisetum sylvaticum are present. Calamagrostis arundinacea more often occurs on sandy soils. The large ferns Athyrium filix-femina and Dryopteris carthusiana are found; Dryopteris

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filix-mas occurs more rarely. Patches dominated by large ferns occur in canopy gaps. Sometimes the spring-growing perennial herbs Anemonoides ranunculoides, Ficaria verna and others can be found in spring. Moss cover is small (3–5%). Atrichum undulatum, Eurhynchium hians, Cirriphyllum piliferum and Plagiomnium cuspidatum are common on the ground. Species of genera Brachythecium, Plagiomnium and Rhizomnium occur on dead, fallen wood. The boreal mosses Pleurozium schreberi, Hylocomium splendens, Rhytidiadelphus triquetrus, etc. occur in the east. Epiphytic mosses and lichens mainly occur on stems of Tilia cordata and Populus tremula (Nitsenko 1972; Degteva 2001; Degteva et  al. 2001; Liksakova 2004). It should be noted that forests dominated by Betula spp. in the overstorey and herbaceous meadow and nemoral species in the ground layer (Betuleta prato-­ nemoroherbosa) develop on abandoned arable lands during the vegetation recovery. Nemoral herb aspen forests (Populeta nemorosa) have a similar distribution as the nemoral herb broad-leaved forests: they occur on watersheds and slopes of river terraces. These forests mainly develop after logging of the nemoral herb broad-­ leaved or mixed forests. Soils vary as in the nemoral herb broad-leaved forests: sod-podzolics, brown soils and grey forest soils occur including soils with a second humic horizon. Crown cover varies from 50 to 80%. Populus tremula dominates with an admixture of Betula pendula, B. pubescens and the broad-leaved trees Tilia cordata, Quercus robur and Acer platanoides. Ulmus glabra and Padus avium are found in wetter habitats. Picea spp. and Abies sibirica (in the east) occur with different abundances. When the proportion of Betula spp. increases in stands of the nemoral herb aspen forests they develop into a so-called nemoral herb birch-aspen forest (Bibikova 1998). Composition and features of the understorey and ground layer are very similar to those in the nemoral birch forests described above. However, in the nemoral aspen forests, undergrowth of Quercus robur, Tilia cordata, Acer platanoides, Ulmus glabra and Picea spp. is common not only in the western and central parts of the region, but also in the east. Lonicera pallasii also often occurs in the east. Nemoral herb grey alder forests (Alneta incanae nemorosa) are described from steep slopes of river valleys and ravines (Vasilevich 1985, 1998). Crown cover is 60–90%. Alnus incana dominates; Picea spp., Betula spp. and Populus tremula ­sporadically occur in the overstorey. Cover of the understorey is 20%. Lonicera xylosteum and Padus avium are common. Undergrowth of Alnus incana covers 5–10%. Sometimes undergrowth of Picea spp. also occurs. Cover of the field layer is 40–70%. Aegopodium podagraria usually dominates, but in some cases nemoral, nitrophilous or boreal tall herbs, such as Campanula latifolia, Chelidonium majus, Chaerophyllum aromaticum, Geranium sylvaticum or Aconitum septentrionale, dominate in the field layer. The nemoral species Geum urbanum, Asarum europaeum, Galeobdolon luteum, Pulmonaria obscura, Ranunculus cassubicus, Ajuga reptans and the tall nemoral herb Stachys sylvatica often occur. Cover of the bottom layer is 3–5%; Plagiomnium cuspidatum, Brachythecium salebrosum, Atrichum

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undulatum, Eurhynchium hians and Rhytidiadelphus triquetrus are most common on the ground (Vasilevich 1985). Subsection of tall herb forests includes forest communities dominated by mesophilous tall herbs in the ground layer; the forests belong to the following two associations of the union Piceion excelsae of the class Vaccinio–Piceetea: (1) ass. Pulmonario obscurae–Piceetum abietis Zaugolnova et  al. 2009 occurring in the east of the hemiboreal region, and (2) ass. Melico nutantis–Piceetum abietis K.-Lund 1981 mainly occurring in the west of the region. Unlike the mesophilous tall herb forests in the boreal region, these forests in the hemiboreal region are dominated not only by boreal tall herbs, but also by nemoral tall herbs, such as Campanula trachelium, C. latifolia, Digitalis grandiflora, Lilium martagon, Salvia glutinosa and others. Boreal tall herbs and ferns are more common in the west. In the east, where forests and broad-leaved trees are better preserved, nemoral tall herbs may co-dominate with boreal ones. However, the proportion of forests with a notable participation of nemoral tall herbs is very small owing to a strong human exploitation of the region. Haplic Cambisols (eutric and dystric) occur more often than other soil types in these forests; Haplic and Albic Luvisols are also common. Haplic and Entic Podzols and Humic Umbrisols occur on sandy sediments. Boreal tall herb spruce and spruce-fir forests (Piceeta (P.-Abieta) boreo-­ magnoherbosa) belong to the subass. typicum of the ass. Pulmonario obscurae– Piceetum abietis Zaugolnova et  al. 2009 in the east and to the ass. Melico nutantis–Piceetum abietis in the west of the region (Smirnova 1954; Abaturov et al. 1988; Vasilevich and Bibikova 2004; Zaugolnova et  al. 2009). As in the boreal region, small areas of these forests are preserved on well-drained relief positions on watersheds in the hemiboreal region. Gap-mosaics in the canopy and treefalls with uprooting often occur in these forests. Crown cover is 60–70%; Picea abies (in the west) and Picea obovata with Abies sibirica (in the east) dominate with an admixture of Betula pendula, B. pubescens, Populus tremula and rarely Alnus incana, Pinus sylvestris or Tilia cordata. Cover of the understorey is 25–40%. Sorbus aucuparia, Lonicera xylosteum, Ribes nigrum and Rosa acicularis constantly occur; Swida alba, Viburnum opulus and Padus avium occur rarely. Picea spp. and Abies sibirica (in the east) are common in the undergrowth; Tilia cordata and Ulmus glabra sporadically occur. Cover of the field layer is 60–90%; there are several co-dominating species in the field layer and several sublayers are formed by herbaceous species. The tall boreal herbs Aconitum septentrionale, Cacalia hastata, Valeriana officinalis, Crepis sibirica and the liana Atragene sibirica as well as the large ferns Diplazium sibiricum and Dryopteris dilatata are common in the first sublayer. The nitrophilous tall herbs and ferns Cirsium oleraceum, Filipendula ulmaria, Athyrium filix-femina, etc. also often occur. The nemoral herbs Aegopodium podagraria, Asarum europaeum, Pulmonaria obscura, Stellaria holostea, etc. as well as the boreal species Oxalis acetosella, Maianthemum bifolium, Gymnocarpium dryopteris, Luzula pilosa and others dominate in the second and third herbaceous sublayers. In general, boreal species slightly prevail over the nemoral ones. Cover of the bottom layer is not high (20–25%); the boreal green mosses Pleurozium schreberi, Hylocomium splendens, Rhytidiadelphus

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triquetrus and Dicranum scoparium are the main species; the hemiboreal mosses Rhodobryum roseum and species of the genera Plagiomnium and Brachythecium rarely occur. Boreal tall herb birch and aspen forests (Betuleta, Populeta boreo-­magnoherbosa) are described from moderately moist areas located on watersheds in the central and eastern parts of the hemiboreal region (Degteva 2001; Zaugolnova et  al. 2009). These forests usually develop after felling of tall herb spruce(−fir) forests. Crown cover varies from 30 to 80%. Betula spp. and/or Populus tremula dominate with a constant admixture of Picea spp. and Abies sibirica (in the east). Cover of the understorey is 20–30%. Sorbus aucuparia is common; Lonicera xylosteum, L. pallasii, Rosa majalis and Padus avium occur. Picea spp. prevail in the undergrowth; Betula spp., Alnus incana and Populus tremula often occur; the broad-­ leaved trees Tilia cordata, Ulmus glabra, Acer platanoides and Fraxinus excelsior as well as Abies sibirica in the east also sporadically occur in the understorey. Cover of the field layer is 60–80%. Aconitum septentrionale dominates in the upper herbaceous layer; Aegopodium podagraria and Oxalis acetosella dominate in the second and the third herbaceous layers, respectively. Calamagrostis arundinacea co-­ dominates on sandy soils. Cacalia hastata, Cirsium heterophyllum, Trollius europaeus, Diplazium sibiricum, Atragene sibirica and Milium effusum are constant. The large ferns Dryopteris carthusiana and D. dilatata and the nitrophylous species Filipendula ulmaria and Geum rivale dominate in canopy gaps and on places of treefall with uprooting. In these forests, the number of boreal species is significantly less than the number of nemoral ones. Mosses cover 5–10% in the bottom layer; sometimes the coverage can reach 30%. The boreal green mosses Pleurozium schreberi, Hylocomium splendens, Dicranum scoparium and Climacium dendroides are common; the hemiboreal species Rhodobryum roseum, Plagiomnium cuspidatum and others also occur. Boreal-nemoral tall herb dark-coniferous – broad-leaved forests (Abieto-Piceeto-­ Tilieta boreo-nemoro-magnoherbosa) are described from tops and slopes of watersheds in the centre and east of the hemiboreal region (Zubareva 1967; Zubareva and Terinov 1967; Samokhina 1997; Shirokov et al. 2006; Zaugolnova et al. 2009). Gap-­ mosaics in the canopy and pit-and-mound topography formed by treefalls with uprooting at different stages of erosion and decay are typical features of these forests. Crown cover is 50–70%; tree stands are dominated by Picea spp., Abies sibirica and Tilia cordata; Ulmus glabra occurs with a low abundance and a high constancy; Acer platanoides, Betula pendula, Populus tremula and Padus avium rarely occur. Cover of the understorey is 20–40%; Sorbus aucuparia, Padus avium and Lonicera xylosteum prevail; Sambucus racemosa, Ribes hispidulum, R. nigrum, Rosa canina, R. majalis and Daphne mezereum occur with high constancy values. Undergrowth of Tilia cordata and Abies sibirica dominates; Picea spp. also occur in the understorey; Ulmus glabra and Acer platanoides occur sporadically. Cover of the field layer is 70–90%. The field layer is very rich in species; it consists of several sublayers dominated by various species. The upper herbaceous sublayer is dominated by the  boreal tall herbs and ferns Aconitum septentrionale, Cacalia hastata,

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Crepis sibirica, Cinna latifolia, Cirsium heterophyllum, Delphinium elatum, Pleurospermum uralense, Trollius europaeus, Diplazium sibiricum, Dryopteris dilatata, etc. together with the nemoral tall herbs Stachys officinalis, S. sylvatica, Bupleurum aureum, Campanula latifolia, C. trachelium, Chaerophyllum aromaticum, Cicerbita uralensis, Digitalis grandiflora, Lathyrus gmelinii, Lilium martagon, etc. in different proportions. The second herbaceous sublayer includes medium and small nemoral herbs, such as Anemonoides altaica, Aegopodium podagraria, Ajuga reptans, Melica nutans, Milium effusum, Polygonatum multiflorum and Viola mirabilis. The third sublayer consists of small boreal herbs, such as Oxalis acetosella, Maianthemum bifolium, Luzula pilosa, Trientalis europaea and others with low abundances. The nitrophilous species Athyrium filix-femina, Stellaria nemorum, Chrysosplenium alternifolium, etc. occur in treefall pits; seedlings of the light-demanding trees Betula pubescens, Salix caprea and others grow on treefall mounds. Cover of the bottom layer is 3–5%, sometimes it reaches up to 10%. The boreal green mosses Pleurozium schreberi, Hylocomium splendens, Dicranum scoparium and Climacium dendroides occur on fallen trees; the hemiboreal species Rhodobryum roseum, Plagiomnium cuspidatum and others occur on the soil surface.

4.1.4  Section: Hemiboreal Swamp Forests As in the boreal forest region, forests referred to in this section are characterized by continuous or periodic waterlogging and running water to varying degrees. These forests occur in the valleys of rivers and streams and they also are found in places where groundwater discharges. Hemiboreal swamp forests differ from those in the boreal region by their plant species composition in the overstorey and understorey, but they are similar to them in their ecological-coenotic structure of the vegetation. Meso-hygrophilous and hygrophilous plants dominate in the ground layer whereas broad-leaved trees and nemoral herbs are more common and the diversity of nitrophilous species is higher compared to the boreal swamp forests. As in the boreal region, we distinguish two subsections within the hemiboreal swamp forests: nitrophilous tall herb forests and genuine swamp tall herb forests. Subsection of nitrophilous tall herb forests in the hemiboreal region differ from such forests in the boreal region by their higher syntaxonomic diversity. This subsection includes plant communities belonging to five associations of the union Alnion incanae Pawłowski, Sokołowski et Wallish. 1928: (1) ass. Alnetum incanae Lüdi 1921 (= Alno incanae–Padetum avii K.-Lund 1971), (2) ass. Urtico–­ Alnetum glutinosae Bulokhov et Solomeshch 2003, (3) ass. Carici remotae–­ Fraxinetum excelsioris Koch ex Faber 1926, (4) ass. Filipendulo ulmariae–Quercetum roboris Polozov et Solomeshch 1999, and (5) ass. Urtico–­ Alnetum incanae Korotkov 1986 as well as plant communities of two associations of the union Calamagrostio canescentis–Piceion abietis Solomeshch in Solomeshch et Grigorjev 1992: (1) ass. Climacio dendroidis–Piceetum abietis

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Korotkov 1991 and (2) ass. Phalaroido arundinaceae–Alnetum glutinosae Zaugolnova 1997 ex Martynenko nov. prov. The diagnostic features of this subsection are the following: (1) there are several herbaceous layers and these contain many species; (2) the first herbaceous layer is dominated by tall nitrophilous herbs while water-marsh, boreal tall herbs and large ferns constantly occur; (3) boreal, nemoral, nitrophilous and water-marsh medium and small herbaceous species constantly occur in different proportions in the second and third herbaceous layers, and (4) there is a lack of boreal green mosses together with a weak development of the moss cover in general. These forests differ from forests of the same subsection in the boreal region by a significant participation of nemoral herbs, including the nemoral tall herbs Lilium martagon, Chaerophyllum aromaticum, Campanula trachelium, etc. Dystric and Eutric Fluvisols prevail; Gleyic Fluvisols also occur. Fluvisols occur close to various Histosols (Fibric, Dystric and others). Nitrophilous tall herb spruce and spruce-fir forests (Piceeta (P.-Abieta) nitrophilo-­magnoherbosa) grow over the entire hemiboreal region along streams and small rivers as well as in depressions in watersheds with flowing water (Kurnaev 1968; Rysin and Savelyeva 2002). Crown cover is 30–40%; Picea spp. dominate in the first, upper tree layer with an admixture of Alnus glutinosa and Tilia cordata; Padus avium, Tilia cordata, Fraxinus excelsior and Ulmus laevis occur in the second tree layer. Cover of the understorey is 30–50%; it consists of Lonicera xylosteum, Sorbus aucuparia, Ribes nigrum and R. spicatum. The sparse undergrowth of Picea spp., Alnus glutinosa, Padus avium, Tilia cordata, Fraxinus excelsior, Ulmus laevis and others mainly occurs on local elevations. Cover of the field layer is 60–80%. Filipendula ulmaria dominates and Geum rivale co-dominates in the upper herbaceous layer; Equisetum palustre and Cirsium oleraceum often occur; Oxalis acetosella can be found with a high abundance in the lower herbaceous layer. The nemoral herbs Aegopodium podagraria, Mercurialis perennis, Pulmonaria obscura, etc. occur on local elevations but with low abundances; small boreal herbs such as Trientalis europaea and Maianthemum bifolium also can be found. Cover of the bottom layer is 5–15%; Mnium affine and Climacium dendroides occur. Nitrophilous tall herb oak and linden forests (Querceto-Tilieta nitrophilo-­ magnoherbosa) are described from the entire region; they occur in lower parts of watersheds, where spring water stagnates during a long time. Crown cover is 70–90%. Quercus robur, Tilia cordata and Alnus incana co-dominate with an admixture of Populus tremula, Betula pubescens and Alnus glutinosa. Trees in the overstorey are 100–120 years old (Iljinskaja et al. 1985). Cover of the understorey is 40–60%; it consists of Corylus avellana, Padus avium, Salix cinerea, Ribes nigrum and Frangula alnus. Undergrowth of Alnus incana and Populus tremula occurs; undergrowth of Quercus robur can be found in light areas located on the edges of depressions. Cover of the field layer is high and reaches up to 80–90%. Nitrophilous tall herbaceous species grow in depressions: Filipendula ulmaria and Urtica dioica dominate; Deschampsia cespitosa, Carex cespitosa and Myosoton aquaticum sometimes occur. The nemoral herbs Aegopodium podagraria, Mercurialis perennis, Galeobdolon luteum, Convallaria majalis, etc. with boreal

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herbs such as Rubus saxatilis often occur on local elevations and Chaerophyllum aromaticum often dominates. The water-marsh species Calamagrostis canescens, Caltha palustris and Carex remota dominate in wetter depressions in floodplains (Korchagin and Senjaninova-Korchagina 1957; Bulokhov and Solomeshch 2003). In the south-east of the hemiboreal region, Brachypodium pinnatum often dominates; the nemoral tall herbs Adenophora lilifolia, Lilium martagon and Agrimonia asiatica and meadow species such as Euphorbia semivillosa can be found with low abundances (Polozov and Solomeshch 1999). Cover of the bottom layer is 3–5%; Atrichum undulatum, Rhodobryum roseum and Climacium dendroides sometimes occur on the soil surface (Iljinskaya et al. 1985). Nitrophilous tall herb aspen forests (Populeta nitrophilo-magnoherbosa) are found in floodplains and in depressions in watersheds over the entire hemiboreal region; these forests occur on sites with rich and moist soils (Iljinskaja et al. 1985; Bibikova 1998; Liksakova 2004). Crown cover is 70–80%; Populus tremula dominates with an admixture of Quercus robur, Acer platanoides, Alnus incana and Betula pubescens. Picea spp. occur in the overstorey in the north of the region. Cover of the understorey is 20–40%; Corylus avellana, Sorbus aucuparia, Lonicera xylosteum, Ribes nigrum, Rosa majalis, Frangula alnus and Viburnum opulus occur in different proportions. An undergrowth of Betula pubescens, Populus tremula, Picea spp. prevails; Alnus incana, Ulmus laevis, rarely Acer platanoides and Quercus robur also occur in the understorey. Cover of the field layer is 60–80%; the nitrophilous tall herbs Filipendula ulmaria, Urtica dioica, Crepis paludosa, Geum rivale, Chaerophyllum aromaticum and Carex cespitosa often dominate; the nitrophilous herb of medium size Impatiens noli-tangere often occurs; the nemoral species Aegopodium podagraria, Stellaria holostea, Galeobdolon luteum and Milium effusum also occur. Calamagrostis canescens is found in waterlogged areas. In the north-west of the hemiboreal region Vaccinium myrtillus and V. vitis-idaea occur with low abundances (Bibikova 1998). Cover of the bottom layer is 3–5%; Climacium dendroides and Plagiomnium cuspidatum sporadically occur. Nitrophilous tall herb birch forests (Betuleta nitrophilo-magnoherbosa) occur over the entire region; they are described from floodplains and depressions on watersheds; they are often found as large patches inside broad-leaved forests (Kurnaev 1968; Liksakova 2004). Crown cover is 30–70%; Betula pubescens dominates, sometimes with an admixture of Quercus robur and Tilia cordata. Cover of the understorey varies from 10 to 50%; Corylus avellana, Ribes nigrum, Padus avium, Sorbus aucuparia, Frangula alnus, Lonicera xylosteum and Viburnum opulus occur in different proportions. Betula pubescens and Picea spp. dominate in the undergrowth in the north of the region; Alnus incana and Salix caprea occur; Quercus robur and Acer platanoides can be also found in the south of the region. Cover of the field layer is 85–95%; Filipendula ulmaria is the most common dominant; Urtica dioica, Geum rivale, Athyrium filix-femina, Angelica sylvestris, Chaerophyllum aromaticum and Ranunculus repens often co-dominate. The number of nemoral species is high: Aegopodium podagraria, Ajuga reptans, Mercurialis perennis, Pulmonaria obscura,

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Asarum europaeum, Ranunculus cassubicus, Stellaria holostea and others constantly occur. The boreal herbs Maianthemum bifolium and Trientalis europaea can often be found. Cover of the bottom layer is 5%; Climacium dendroides and Plagiomnium cuspidatum occur. Nitrophilous tall herb grey alder forests (Alneta incanae nitrophilo-­ magnoherbosa) are described from hollows, floodplains, slopes of terraces and small depressions on watersheds (Rabotnov 1939; Iljinskaja et al. 1985; Korotkov 1991; Vasilevich 1998; Polozov and Solomeshch 1999; Degteva et  al. 2001; Bulokhov and Solomeshch 2003; Liksakova 2004). Crown cover is 70–90%; Alnus incana dominates with a small admixture of Betula pubescens, B. pendula and Picea spp.; Quercus robur and Alnus glutinosa sometimes also occur in the overstorey; individuals of Abies sibirica also can be found in the east. Cover of the understorey is 40–60%; it consists of Sorbus aucuparia, Frangula alnus, Lonicera xylosteum, Ribes nigrum and R. spicatum. Lonicera pallasii occurs in the east. Undergrowth of Picea spp. often occurs and undergrowth of Tilia cordata can be rarely found. Cover of the field layer is 60–80%; the nitrophilous tall herbs Filipendula ulmaria and Urtica dioica dominate; sometimes Chaerophyllum aromaticum, Chelidonium majus, Impatiens noli-tangere or Deschampsia cespitosa also dominate. Aegopodium podagraria can dominate in the lower herbaceous layer. The nemoral herbs Mercurialis perennis, Pulmonaria obscura, Asarum europaeum, Ranunculus cassubicus and others often occur. The small boreal herbs Oxalis acetosella, Equisetum pratense and E. sylvaticum may sometimes dominate in the lowest herbaceous layer. In general, the presence of boreal herbs increases towards the north of the region: Maianthemum bifolium, Luzula pilosa, Trientalis europaea and others occur. Cover of the bottom layer is usually low (5–15%) but sometimes reaches up to 30%; species of the genus Brachythecium prevail. Nitrophilous tall herb black alder forests (Alneta glutinosae nitrophilo-­ magnoherbosa) are described from the lower parts of slopes and along banks of small rivers and streams (Vasilevich and Shchukina 2001; Bulokhov and Solomeshch 2003). Crown cover varies from 40 to 70%: Alnus glutinosa dominates with a small admixture of Padus avium. Quercus robur, Acer platanoides, Picea spp., Betula pubescens, Populus tremula and Alnus incana also rarely occur in the overstorey. Cover of the understorey is 30–60%: Sorbus aucuparia, Frangula alnus and Padus avium often occur; Corylus avellana, Euonymus verrucosa, Sambucus racemosa, Crataegus sanguinea, Rhamnus cathartica and Ribes nigrum also can be found. Undergrowth of Alnus glutinosa, A. incana, Picea spp., Tilia cordata, Ulmus laevis, Quercus robur and rarely Fraxinus excelsior, Acer platanoides and Salix cinerea occurs. Cover of the field layer is 90–100%. The nitrophilous tall herbs Urtica dioica, Filipendula ulmaria and Cirsium oleraceum dominate; large ferns, such as the nitrophilous Athyrium filix-femina and Matteuccia struthiopteris as well as the nemoral Dryopteris filix-mas and Dryopteris carthusiana, prevail. The nitrophilous herbs Angelica archangelica, Lycopus europaeus, Solanum dulcamara and Geum rivale often occur as well as the nemoral herbs Aegopodium podagraria, Scrophularia nodosa, Asarum europaeum, Mercurialis perennis, Galeobdolon luteum, Bromopsis inermis, Stellaria holostea and Convallaria majalis. Festuca gigantea, Impatiens

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noli-tangere and Stellaria nemorum occur with lower abundances; the herbaceous liana Humulus lupulus also occurs. The boreal herb Oxalis acetosella often occurs and sometimes dominates; other small boreal herbs, such as Maianthemum bifolium, Trientalis europaea, etc., can also be found. In some places, the boreal species Vaccinium myrtillus and Luzula pilosa occur with a high constancy (Vasilevich and Shchukina 2001). Cover of the bottom layer is 5–15% with species of the genera Brachythecium, Plagiomnium and Mnium. Subsection of genuine swamp tall herb forests. There are three diagnostic features of the forests in this susbsection. Two features are the same as those that we distinguished for such forests in the boreal region: (1) the dominance of species of the water-marsh ecological-coenotic group in the ground layer, such as the large hygrophilous sedges Carex vesicaria, C. elongata, C. acuta, etc., the grasses Calamagrostis canescens, Phalaroides arundinacea, Phragmites australis, etc. and the herbs Veronica longifolia, Naumburgia thyrsiflora, Thalictrum lucidum, Menyanthes trifoliata, Iris pseudacorus, etc. and (2) the high frequency and in some cases the dominance of nitrophilous tall herbs, such as Filipendula ulmaria, Cirsium oleraceum, Lysimachia vulgaris, Scirpus sylvaticus, etc. The third feature of the forests of this subsection in the hemiboreal region is the presence of nemoral and boreal herbs usually growing at elevations around tree bases, as well as the presence of boreal green mosses and sphagnum mosses in the ground layer. The plant communities of this subsection are classified into the following three associations belonging to two unions: (1) ass. Lysimachio vulgaris–Alnetum glutinosae K.-Lund 1981 and (2) ass. Climacio dendroidis–Piceetum abietis Korotkov 1991 both of the union Alnion glutinosae (Malcuit 1929) Müller et Görs 1958, and (3) ass. Sphagno girgensohnii–Betuletum pubescentis Liksakova 2004 ex Martynenko nov. prov. of the union Piceion excelsae Pawłowski, Sokołowski et Wallisch 1928. The subsection includes swamp forests dominated by Picea spp., Betula spp., Populus tremula or Alnus glutinosa. Fibric and Dystric Histosols, Histic and Dystric Gleysols prevail in these forests. Various Fluvisols (Histic, Dystric, etc.) occur in floodplains. Genuine swamp tall herb spruce forests (Piceeta uliginoso-magnoherbosa) are described from lower elevation areas with a shallow flow of groundwater (Sokolov 1931; Korotkov 1991; Vasylevych 2002; Fedorchuk et al. 2005). The composition of the ground layer of these forests is close to that in the nitrophilous tall herb spruce forests, but the proportion of the water-marsh species is higher. Crown cover is 50–60%: Picea spp. dominate, Betula pubescens always occurs, Populus tremula and Alnus glutinosa often occur; Abies sibirica also occurs in the overstorey in the east. Pinus sylvestris and Alnus incana can be sporadically found. Sometimes, there is second tree layer in the forest canopy formed by Picea spp., Betula pubescens and Alnus incana. Cover of the understorey is 10–20%: Sorbus aucuparia and Frangula alnus are the most common; Juniperus communis, Ribes nigrum and Daphne mezereum rarely occur. Sometimes Lonicera xylosteum is frequent. Undergrowth of Picea spp. prevails; undergrowth of Tilia cordata, Ulmus glabra, Acer platanoides and Padus avium occasionally occurs. Cover of the field

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layer is 60–80%: the water-marsh species Calamagrostis canescens, Carex cespitosa, C. rostrata and others together with the nitrophilous tall herbs Filipendula ulmaria, Cirsium oleraceum and the large fern Athyrium filix-femina co-dominate. Sometimes Oxalis acetosella dominates in the lowest herbaceous layer. Geum rivale, Aconitum septentrionale, Phegopteris connectilis and Viola epipsila often occur. The nemoral species Aegopodium podagraria, Asarum europaeum, Paris quadrifolia and others, and the small boreal herbs Maianthemum bifolium, Luzula pilosa, Trientalis europaea, etc. grow on elevations around tree trunks. Cover of the bottom layer is 30–50%; Pleurozium schreberi, Hylocomium splendens and Rhytidiadelphus triquetrus often occur; Climacium dendroides often occurs with a high abundance; sphagnum mosses rarely occur with a low abundance. Genuine swamp tall herb birch and aspen forests (Betuleto-Populeta uliginoso-­ magnoherbosa) are described from depressions between ridges in floodplains, banks of streams, and rims of marshes with flowing water (Sokolov 1931; Korotkov 1991; Vasilevich 1997; Degteva 2001; Liksakova 2004; Fedorchuk et al. 2005). Crown cover is 40–70%: Betula pubescens and/or Populus tremula dominate; Picea spp. and to a lesser extent also Alnus glutinosa occur in the tree layer; Pinus sylvestris also rarely occurs in the overstorey. Cover of the understorey is 15–30%: it always includes Sorbus aucuparia, Frangula alnus, Ribes nigrum and Salix cinerea. Undergrowth of Picea spp. prevails; Betula pubescens and Alnus glutinosa often occur in the understorey while undergrowth of Tilia cordata, Quercus robur, Alnus incana and Salix cinerea occurs rarely. Cover of the field layer is 50–70%. Filipendula ulmaria, Athyrium filix-femina, Calamagrostis canescens and Carex cespitosa dominate; Iris pseudacorus, Thelypteris palustris, Galium palustre, Ranunculus repens, Geum rivale, Crepis paludosa, Cardamine amara and others are common. Dwarf shrubs and small boreal herbs, such as Vaccinium myrtillus, V. vitis-idaea, Maianthemum bifolium, Oxalis acetosella, Trientalis europaea, etc., often occur. Water-marsh species, such as Galium palustre, Viola epipsila, V. palustris and Comarum palustre, also occur. The large ferns Dryopteris dilatata and Matteuccia struthiopteris sometimes locally occur with high abundances. In the east, tall boreal herbs, such as Aconitum septentrionale, Chamaerion angustifolium and Trollius europaeus, can be found as well as the nitrophilous and water-marsh tall herbs. Cover of the bottom layer is 20–30%; Climacium dendroides is the typical species; Pleurozium schreberi and Hylocomium splendens often occur. Dicranum scoparium occurs in the west. Sphagnum girgensohnii prevails in the most humid habitats; S. angustifolium and S. magellanicum rarely occur there. S. squarrosum and S. centrale are found in forests dominated by Betula pubescens in the overstorey and Caltha palustris in the field layer. Genuine swamp tall herb black alder forests (Alneta glutinosae uliginoso-­ magnoherbosa) are found along rivers, streams and lakes. Crown cover is 40–80%: Alnus glutinosa prevails with an admixture of Betula pubescens and Padus avium. Cover of the understorey is 30–60%: Ribes nigrum, Sorbus aucuparia, Salix cinerea and Frangula alnus are the most common. An undergrowth of Picea spp., with a low abundance, constantly occurs, Alnus glutinosa rarely occurs in the understorey. Cover of the field layer is 35–60%. Phragmites australis, Filipendula ulmaria and

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Athyrium filix-femina dominate; sometimes Geum rivale and Viola epipsila dominate. Equisetum sylvaticum, E. fluviatile, Calla palustris, Comarum palustre, Thelypteris palustris and Thyselium palustre occur with high abundances (Vasylevich and Shchukina 2001). Cover of the bottom layer is 20–30%: Climacium dendroides is the most common; Sphagnum angustifolium, S. centrale and S. squarrosum can be found (Botch 1993; Prieditis 1997; Vasylevich and Shchukina 2001).

4.1.5  Section: Sphagnum Forests The diagnostic feature of these forests is the dominance of sphagnum mosses in the ground layer developed under conditions of an excess of stagnant moisture and soil gleying. As in the boreal region, forests of this section grow in depressions on watersheds, on the gentle slopes of poorly drained sites, and at the lower parts of slopes with high ground water tables. The plant communities are very different in their structure and species composition as a result of differences in relief positions and features of waterlogging on various substrates. In the hemiboreal region, sphagnum forests are distributed less widely than in the boreal forest region (Gribova et al. 1980; Kutenkov and Kuznetsov 2013), but the composition and structure of these communities are very similar to those in the boreal region. This is probably due to the great similarity in habitat and soil conditions. As in the boreal region, we distinguish three subsections within the sphagnum forests in the hemiboreal region: polytrichum-sphagnum, dwarf shrub – sphagnum and herb-sphagnum forests. Subsection of polytric-sphagnum forests includes plant communities of the following two associations: (1) ass. Sphagno girgensohnii–Piceetum abietis Polak. 1962 belonging to the union Piceion excelsae Pawłowski, Sokołowski et Wallisch 1928, and (2) ass. Molinio caeruleae–Pinetum sylvestris (E.  Schmid. 1936) em. Mat. (1973) 1981 of the union Dicrano–Pinion (Libbert 1933) Matuszkiewicz 1962. A feature of this subsection is that sphagnum mosses (mainly Sphagnum girgensohnii) and green mosses (mainly Polytrichum commune and sometimes Pleurozium schreberi) co-dominate in different proportions in the ground layer, reflecting the different degrees of waterlogging of these forests. Small boreal herbs, such as Trientalis europaea, Maianthemum bifolium, Luzula pilosa, Oxalis acetosella, Equisetum sylvaticum and Linnaea borealis as well as the dwarf shrubs Vaccinium myrtillus and V. vitis-idaea, are prominent in the field layer. The joint presence of Sphagnum girgensohnii and boreal herbaceous species gives evidence of the process of waterlogging in the green moss – dwarf shrub and/or green moss – small boreal herb forests. Histic and Gleyic Podzols dominate on coarse-textured substrates and Histic Gleysols dominate in depressions. Histic and Gleyic Albeluvisols together with Fibric and Dystric Histosols often occur. Polytrichum-sphagnum spruce forests (Piceeta polytrichoso-sphagnosa) are described from different parts of the hemiboreal region; they are found in  local depressions on terraces and watersheds or near sources of rivers and also on gentle

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slopes around these habitats (Smirnova 1928, 1954; Korchagin 1929; Sokolov 1931; Korchagin and Senjaninova-Korchagina 1957; Vasilevich and Bibikova 2004). Microrelief varies from flat to hummocky; the height of mounds is up to 40 cm; the peat layer can reach 20 cm in thickness (Smirnova 1928). Crown cover varies from 40 to 80%: Picea spp. dominate with an admixture of Betula pendula, B. pubescens, Pinus sylvestris, Populus tremula and Alnus incana. The height of Picea spp. varies from 12–15 to 17–19 m; the site classes are 4 and 5 (Smirnova 1936; Korchagin and Senjaninova-Korchagina 1957). Cover of the understorey is 20–35%: Sorbus aucuparia, Juniperus communis, Frangula alnus, Salix aurita, S. cinerea and S. pentandra often occur. The undergrowth of Picea spp., Betula spp., Populus tremula, Alnus incana is abundant; Quercus robur and Alnus glutinosa also rarely occur in the understorey. Cover of the field layer is 25–45%. Vaccinium myrtillus, V. vitis-idaea, Equisetum sylvaticum and Carex globularis co-dominate. Rubus chamaemorus occurs sometimes in the north of the region. Cover of the bottom layer is 90–100%: Sphagnum girgensohnii prevails; Polytrichum commune and Pleurozium schreberi constantly occur; Sphagnum angustifolium, S. magellanicum, S. wulfianum, S. centrale, S. russowii and S. squarrosum also can be found. Some of these sphagnums can be found with high abundances (Gavrilov and Karpov 1962). Polytrichum-sphagnum pine forests (Pineta polytrichoso-sphagnosa) occur over the entire hemiboreal region under conditions of excessive moisture in small, poorly drained depressions, as well as on better-drained sites after ground fires (Sokolov 1931; Rysin 1975; Savelyeva 2000; Rysin and Savelyeva 2008). Crown cover is 40–70%; Pinus sylvestris dominates. The average height of trees is 20–21 m at the age of 80 years; the site class is 2 (Sokolov 1931). Picea spp. often co-dominate in the overstorey; Betula pubescens and B. pendula sometimes occur as an admixture; Larix sibirica can be found in the east. Cover of the understorey is 5–10%: it consists of single individuals of Salix cinerea, Juniperus communis, Frangula alnus and Sorbus aucuparia; Chamaecytisus ruthenicus and Rosa majalis also rarely occur. The undergrowth of Pinus sylvestris, Picea spp. and Betula pubescens is abundant. An undergrowth of Larix sibirica is found in the east. Cover of the field layer is 30–80%: Molinia caerulea, Rubus chamaemorus and Vaccinium myrtillus co-­dominate; V. vitis-idaea, V. uliginosum, Melampyrum pratense, Calamagrostis arundinacea and Dactylorhiza maculata often occur. Species of the oligotrophic ecological-coenotic group, such as Carex globularis, Ledum palustre, Chamaedaphne calyculata, Eriophorum vaginatum, etc., grow in excessively wet microsites. Cover of the bottom layer varies significantly depending on dominants in the field layer: mosses cover close to 100% under domination of Vaccinium myrtillus; moss cover decreases to 40% when Molinia caerulea dominates. Sphagnum girgensohnii is the most common species of the sphagnums; the green moss Pleurozium schreberi often occurs; Polytrichum commune always occurs and sometimes absolutely dominates. It should be noted that Molinia caerulea usually marks a past fire (Smirnova 1998; Jacquemyn et al. 2005) and polytrichum-sphagnum pine forests dominated by Molinia caerulea also show various signs of past fires (Zaugolnova and Martynenko 2014).

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Polytrichum-sphagnum birch forests (Betuleta polytrichoso-sphagnosa) occur over the entire region; they occupy small patches in depressions and on rims of sphagnum bogs (Degteva et al. 2001; Liksakova 2004). Crown cover is 60–70%: Betula pubescens or Populus tremula dominate. Picea spp. always occur in the second layer of the overstorey or in the understorey, sometimes with a high abundance. Pinus sylvestris rarely occurs. Cover of the understorey is 5–15%: Sorbus aucuparia and Frangula alnus are the most common. Cover of the field layer is 20–50%. Vaccinium myrtillus, V. vitis-idaea, Equisetum sylvaticum and sometimes Molinia caerulea co-dominate; Trientalis europaea and Maianthemum bifolium often occur. Cover of the bottom layer reaches 70%: there are large areas with a continuous moss cover and there are also patches of mosses in depressions. Pleurozium schreberi and Sphagnum girgensohnii occur with high constancies. Sometimes the species composition of the sphagnum vegetation is quite diverse: Sphagnum wulfianum, S. angustifolium, S. centrale, S. magellanicum, etc. can be found and indicate a long history of waterlogging in the area. Subsection of dwarf shrub – sphagnum forests includes plant communities classified as the ass. Ledo–Pinetum sylvestris R.Tx. 1955. (= Vaccinio uliginosi– Pinetum sylvestris Kleit 1929 em. Mat. 1962) of the union Ledo–Pinion Tx. 1955. The forests contain a significant number of species of oligotrophic bogs of the class Oxycocco–Sphagnetea Br.-Bl.et Tx. 1943 and a small number of diagnostic species of the boreal forest class Vaccinio–Piceetea Br.-Bl. in Br.-Bl., Siss. et Vlieger 1939. Soils are the same as in the polytrichum-sphagnum forests: there are Histic and Gleyic Podzols, Histic Gleysols, Histic and Gleyic Albeluvisols together with Fibric and Dystric Histosols. From the hemiboreal region only forests dominated by Pinus sylvestris are described in this subsection. Dwarf shrub – sphagnum forests dominated by Picea spp. also occur in the region (O.V. Smirnova’s observations), but they are very rare due to the high intensity of anthropogenic impacts there (compared with the boreal region), so these forests have not yet been studied. Dwarf shrub – sphagnum pine forests (Pineta sylvestris fruticuloso-sphagnosa) occur over the entire hemiboreal region. They are described from depressions between dunes and from rims of bogs (Sokolov 1931; Gavrilov and Karpov 1962; Korotkov 1991; Bulokhov and Solomeshch 2003; Fedorchuk et al. 2005). The forest stands consist of Pinus sylvestris; crowns cover 30–60% of the overstorey. The height of the Pinus sylvestris individuals is 15–17 m and their trunk diameters vary from 16 to 27 cm at ages from 80–90 to 130 years old (Sokolov 1931; Korotkov 1991). Picea spp. also sporadically occur in the overstorey. Betula pubescens often occurs in the south of the region where mixed stands dominated by Pinus sylvestris and Betula pubescens are found. Cover of the understorey is 10–15%; Salix cinerea, S. aurita and S. myrsinifolia occur. Undergrowth of Pinus sylvestris prevails. Betula pubescens of low vitality can be also found in the understorey (Sokolov 1931). Northern species in the understorey, such as Betula nana and B. humilis, occur far to the south within these forests. Cover of the field layer is 50–70%. Hummocky microrelief and a mosaic structure of the field layer are typical. The oligotrophic species Chamaedaphne calyculata, Andromeda polifolia, Ledum palustre,

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Vaccinium uliginosum and Oxycoccus palustris dominate. Sometimes V. myrtillus and V. vitis-idaea create a separate layer which defines the physiognomy of the communities. Eriophorum vaginatum locally dominates. Rubus chamaemorus and Empetrum nigrum occur in the north of the region. Cover of the bottom layer is 90–100%: Sphagnum angustifolium, S. russowii, S. magellanicum and S. acutifolium dominate. Among the green mosses, Polytrichum commune dominates. Pleurozium schreberi often occurs with a low abundance. Subsection of herb-sphagnum forests comprises bog forests of low density but with a well-developed moss cover of sphagnum and boreal green mosses and with hygrophilous, mesotrophic or oligotrophic, herbaceous species in the field layer. Within this subsection, we distinguish the following two variants of plant communities: (1) a variant of mesotrophic communities with diagnostic species of the classes Vaccinio–Piceetea and Alnetea glutinosae, and (2) a variant of oligotrophic communities with diagnostic species of the classes Vaccinio–Piceetea, Vaccinietea uliginosi and Oxycocco–Sphagnetea. The first variant includes forest communites of the following associations: (1) Climacio dendroidis–Piceetum abietis Korotkov 1991, (2) Sphagno girgensohnii–Piceetum abietis Polak. 1962, (3) Carici cinereae–Betuletum pubescentis Korotkov 1986 (=Carici canescentis–­ Betuletum pubescentis Korotkov 1986) and (4) Alnetum glutinosae sphagnetosum Schwickerath 1944. The second variant inludes plant communities of the ass. Pino sylvestris–Eriophoretum vaginati Lapshina 2010. In both variants, soils are the same as in the other sphagnum forests: soils with a peaty topsoil such as Histic Gleysols prevail. Mesotrophic herb-sphagnum spruce forests (Piceeta mesotrophoherboso-­ sphagnosa) are described from rims of bogs, depressions and edges of streams located in the western and central parts of the region (Korotkov 1991; Rysin and Sevelyeva 2002; Fedorchuk et al. 2005). Crown cover varies from 40 to 80%: Picea abies predominates, Betula pubescens always occurs; Padus avium and Pinus sylvestris rarely occur. Cover of the understorey varies from 10 to 50%: Frangula alnus and Alnus incana are the most common; Ribes nigrum, Salix aurita and Sorbus aucuparia occasionally occur. Undergrowth of Picea abies and Betula pubescens often occurs. Cover of the field layer is 50–60%, but no species dominate the field layer. The nitrophilous plants Filipendula ulmaria, Athyrium filix-femina, Viola epipsila and Galium palustre, the water-marsh species Calamagrostis canescens, Carex cespitosa and Equisetum fluviatile as well as the oligotrophic species Comarum palustre and Menyanthes trifoliata often occur. Sometimes Equisetum sylvaticum, Vaccinium myrtillus, V. vitis-idaea, Maianthemum bifolium and Rubus saxatilis are frequent. Cover of the bottom layer varies from 50 to 95%: Sphagnum girgensohnii, S. magellanicum or S. squarrosum dominate; other sphagnum species are rare; Climacium dendroides and Pseudobryum cinclidioides often occur. Mesotrophic herb-sphagnum birch forests (Betuleta mesotrophoherboso-­ sphagnosa) occur in local depressions, and on rims of lakes and bogs with weakly flowing water. These forests are described from the west and center of the region where they do not occupy large, continuous areas (Smirnova 1928; Korotkov 1991). Crown cover is 30–60%. Forest stands are dominated by Betula pubescens with a

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high participation of Alnus glutinosa and a low frequency of Picea spp. Cover of the understorey is 10–30%: Salix aurita and Frangula alnus are most common; Salix cinerea rarely occurs; undergrowth of Betula pubescens and Picea spp. often occurs. Cover of the field layer varies from usually 10–30% to, far more rarely, 60–70%. Sedges from the water-marsh and oligotrophic ecological-coenotic groups, such as Carex cinerea, C. lasiocarpa, C. elongata and C. rostrata, dominate; the nitrophilous tall herbs Galium palustre, Thyselium palustre, Filipendula ulmaria and the fern Athyrium filix-femina occur with varying abundances. At the same time, the boreal dwarf shrub Vaccinium myrtillus and the small boreal herb Trientalis europaea also often occur. Cover of the bottom layer is high (60–90%): Sphagnum riparium, S. squarrosum, S. subbicolor, S. girgensohnii, S. angustifolium, S. centrale and S. magellanicum occur with high abundances. A high diversity of epiphytic lichens and mosses is also observed. Mesotrophic herb-sphagnum black alder forests (Alneta glutinosae mesotrophoherboso-­sphagnosa) occur on margins of bogs and were described from the west of the region (Smirnova 1928; Botch 1993). Crown cover varies from 40 to 80%: Alnus glutinosa predominates with an admixture of Betula pubescens and rarely Picea abies. Cover of the understorey is 20–30%: Frangula alnus, Salix aurita and Ribes nigrum are most common. Cover of the field layer is 40–70%: Athyrium filix-femina, Viola epipsila and Galium palustre dominate; Iris pseudacorus occurs with a high abundance. Cover of the bottom layer is 50–70%; sphagnum mosses prevail; Sphagnum squarrosum and S. girgensohnii are the most abundant. S. subbicolor and Pseudobryum cinclidioides often occur. Oligotrophic herb-sphagnum pine forests (Pineta oligotropho-herboso-­ sphagnosa) are described from depressions with running water and edges of transitional bogs in the west of the region (Fedorchuk et  al. 2005). Crown cover is 50–60%: Pinus sylvestris and Betula pubescens co-dominate with an admixture of Picea abies; Alnus incana and Populus tremula sporadically occur. Cover of the understorey is 5–10%: Salix cinerea, S. aurita and S. myrsinifolia rarely occur; Chamaedaphne calyculata also can occur. An undergrowth of Pinus sylvestris and Betula pubescens with an admixture of Picea abies is common. Cover of the field layer is 25–50%. Eriophorum vaginatum often occurs and sometimes dominates. Menyanthes trifoliata, Carex lasiocarpa and Phragmites australis sometimes codominate. Cover of the bottom layer is 85–95%: Sphagnum magellanicum, S. angustifolium, S. fallax and sometimes S. girgensohnii dominate. The boreal green mosses Pleurozium schreberi, Polytrichum strictum, Dicranum scoparium and Hylocomium splendens also occur. Oligotrophic herb-sphagnum birch forests (Betuleta oligotropho-herboso-­ sphagnosa) are similar to the Pineta oligotropho-herboso-sphagnosa. They are also described from depression with running water and edges of transitional bogs (Vasilevish 1997; Fedorchuk et al. 2005). Crown cover is 40–50%: Betula pubescens and Pinus sylvestris co-dominate with an admixture of Picea abies; Alnus incana and Populus tremula can be also found. Cover of the understorey is 35–50%: Salix cinerea is the most common; S. myrsinifolia, S. myrtilloides and S. rosmarinifolia occur; an undergrowth of Picea abies, Betula pubescens and Pinus sylvestris

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often occurs. Cover of the field layer is 40–50%: Menyanthes trifoliata, Comarum palustre and Naumburgia thyrsiflora co-dominate; Eriophorum vaginatum, Calamagrostis canescens, Vaccinium uliginosum, Chamaedaphne calyculata and Oxycoccus palustris often occur. Cover of the bottom layer is 60–75%: Sphagnum magellanicum and S. girgensohnii dominate. S. flexuosum is found only in the south of the region. The boreal green mosses Pleurozium schreberi, Polytrichum strictum, Dicranum scoparium and Hylocomium splendens also occur.

4.1.6  Conclusion Based on the dominant ecological-coenotic approach, we described forest vegetation communities spread in the hemiboreal region of European Russia. According to the dominance in the field layer, we distinguished the following five sections of forests in the hemiboreal region: lichen, green moss, herb, swamp, and sphagnum forests. Lichen and sphagnum forests are formed under conditions of severe ecological stress. Lichen forests are formed on well-drained sites on watersheds under conditions of repeated fire, i.e. repeated pyrogenic destruction of litter, the ground layer of the vegetation and the tree undergrowth. Sphagnum forests are formed on poorly drained depressions on watersheds where waterlogging is developed often due to fire and clear-cuttings. These forests of the hemiboreal region are comparable to similar forests located in the boreal region. The hemiboreal forests are poorer in syntaxonomic diversity than the boreal lichen and sphagnum forests. Probably, milder climatic conditions accelerate the successional transfer of communities of poor sites into communities of richer sites and, as a result, the diversity of communities of the poorest environmental conditions is higher in a more severe climate while the diversity of communities of richer sites is higher in a milder climate zone. The green moss hemiboreal forests are more diverse compared to the green moss boreal forests. We distinguish three subsections within the green moss forests. Two of them (dwarf shrub – green moss and small boreal herb – green moss forests) are very similar in species composition and vegetation structure to the corresponding forests in the boreal region. The difference is found in the presence of broad-leaved trees, such as Tilia cordata, Acer platanoides, Quercus robur, Ulmus glabra, etc., and the nemoral shrubs Corylus avellana, Euonymus verrucosa, Lonicera xylosteum and others in the understorey of the hemiboreal communities. The third subsection in the green moss section is present only in the hemiboreal region: these are the piny herb – green moss forests. They contain species from the northern Pinus sylvestris forests, together with species from the southern Pinus sylvestris forests, such as the shrubs Caragana frutex, Chamaecytisus ruthenicus, Cerasus fruticosa, etc., and the herbs Campanula rotundifolia, Galium tinctorium, Vincetoxicum albowianum, Seseli krylovii, Lupinaster pentaphyllus, etc. These species also often occur in the northern steppe region on sandy substrates (Nitsenko 1965). Simultaneous presence of species of the northern and southern Pinus sylvestris forests is a typical feature of the hemiboreal pine forests. Broad-leaved trees, such as

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Tilia cordata, Quercus robur, Acer platanoides, etc., together with Larix sibirica occur in the understorey of these forests. The most important difference between the boreal and the hemiboreal forests appears in the existence of diverse herb forests in the hemiboreal region. In such forests, boreal green mosses and boreal dwarf shrubs do not play important roles in the ground layer: they do not dominate and even rarely occur, whereas boreal and nemoral herbaceous species of different sizes form the core of the vegetation. The herb section comprises the highest number of subsections in the hemiboreal region, namely five. The proportions of the boreal and nemoral species vary irregularly in the transition zone from boreal to hemiboreal forests. For example, small and tall boreal herbs and ferns occur with various abundances in both the boreal as well as in the hemiboreal forests. Spring-growing and -flowering nemoral herbs occur more often in the hemiboreal forests. In canopy gaps on the richest soils, nemoral tall herbs appear and a mixed group of tall boreal-nemoral and nitrophilous herbs and ferns do occur. Most species of this mixed group belong to the boreal or nitrophilous tall herbs, but in the least disturbed forests, located in the south-eastern part of the region, a considerable proportion of tall herbs is nemoral. The best preserved hemiboreal forests are the boreal-nemoral tall herb dark-­ coniferous  – broad-leaved forests (Abieto-Piceeto-Tilieta boreo-nemoro-­ magnoherbosa). They maintained the most complete species pool of trees, shrubs and herbaceous plants. Consequently, these forests are treated as an object closest to the reference for reconstructions of the forest cover of Eastern Europe in the late Holocene (Smirnova 2004).

4.2  F  eatures of the Historical Land-Use in the Hemiboreal Region The hemiboreal region differs from other forest regions in the almost constant presence of both dark-coniferous and broad-leaved trees throughout most of the Holocene (Khotinsky 1977; Kremenetsky et al. 2000). On sandy deposits, including woodlands on ancient alluvial plains (Polesie) in the south of the hemiboreal region, forests dominated by Pinus sylvestris widely occurred throughout the Holocene; the proportion of broad-leaved trees has significantly increased there since 7000 years BP (Bolikhovskaya 1988; Novenko et al. 2015). Most probably, the constant presence of Pinus sylvestris on the sandy deposits was caused by frequent fires. Reconstruction of fire frequency in south-eastern Meshchora (Ryazan region) from carbonaceous layers in columns of peat deposits showed a high frequency of severe fires since 9000 years BP: for different sites in the period of 9000–2000 years BP the mean interval between fires ranged from 70 to 200 years (Novenko et al. 2015). Increase in fire frequency was registered for the period of 5000–4000 years BP. After 2000 BP the average frequency of severe fires all over the place fell to 500 years;

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that may be associated with the development of plough farming in the region and later the increasing concern for forest preservation. On the whole, the major known transformations of nature in the hemiboreal forest region were related to the economic development, first and foremost the development of agriculture. Agriculture was introduced here not later than 4000–4500 years ago. During the Bronze Age agriculture spread among the tribes of the Fatyan, Middle Dnieper and other cultures. Slash-and-burn clearing dominated and, perhaps, it was the only practice for a long time. The main evidence for this is the presence of large numbers of wood-cutting axes at every camp (Krasnov 1971; Kraynov 1972). Settlements were mainly localized in river valleys and on lake shores. However, many archeological sites are located far from the river valleys. This indicates that in the Bronze Age, slash-and-burn agriculture may have been practiced in a significant part of central European Russia. In pollen diagrams from this area an increase in Betula pollen and a noticeable drop in the proportion of Picea and Alnus pollen were found at about 4000 years BP (Novenko et al. 2014) and that indirectly testifies to agrarian change in the area. As in the boreal region, slash-and-burn clearing often caused forest fires; areas with sandy soils typically had the most frequent fires. Apart from the traces of slash-and-burn agriculture, all the relic camps located within the modern forest region have cattle remains (Tsalkin 1966). It seems that in the forest region cattle were pastured everywhere: in the forest, on abandoned fields, and on clearings created and maintained by wild ungulates. It is very difficult to estimate the impact of bronze-age agriculture on the formation of the structure and composition of the forest cover and to separate this impact from the later transformations. Probably, bronze-age agriculture gradually decreased the buffer capacity of the ecosystems: as a result of clearing and pasturing, microrelief was being leveled, soil cover (first of all on sandy soils) was transformed, and the natural mosaic of forests was getting disturbed. In the early Iron Age, settlements became more conservative, and the distances between them shortened (in the river valleys sometimes down to 1 km). During this period the first cases of arable farming were registered in the region (Istoriya krestyanstva v SSSR... 1987a; Ershova et al. 2014). Gradually, a system of arable farming lands was being formed. On watersheds spontaneous slash-and-burn clearing seemed to prevail as before, but near the settlements “classical” slash-and-burn agriculture with a regular period of fallow were developing as well as arable farming. With the spread of ploughing tools, mixed forms of agriculture, combining the methods of slash-and-burn clearing with the methods of arable farming, seem to emerge. Slashing and burning became a way to clear a plot for ploughing; after soil depletion, the plot was abandoned. As shown by soil-morphological studies, a large part of watershed territories in the south and center of the region (including areas with heavy loamy soils) was for the first time subjected to such impacts 2500–1500 years ago (i.e. not later than by the middle of the 1st millenium AD) (Bobrovsky 2010). From that time onward, pollen of cultivated cereals is constantly found in pollen diagrams, and the proportion of herb pollen also increased (Nosova et  al. 2014;

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Novenko et al. 2014). At almost all sites in the hemiboreal region, maximum participation of broad-leaved trees in the pollen diagram is registered for the period of 7000–2000  years BP and then their participation decreases (Khotinsky 1977; Khotinsky et al. 1991; Novenko 2011, 2016; Nosova et al. 2014). In the area of present-day Moscow, centers of arable farming were related to the settlements of the Dyakovian culture which occupied the territory from the beginning of the 1st millenium BC to the middle of the 1st millenium AD. First indications of arable farming by Dyakovian tribes date from the middle of the 1st millenium BC (Aleksandrovsky and Aleksandrovskaya 2005). In lengthy segments of river valleys a regular chain of ancient town and village settlements is revealed. Those settlements have been there for a very long time. For example, the Dyakovian town settlement (present-day Moscow) has existed for about 1500 years. The people settled not only on the floodplains and low terraces (where haymaking probably prevailed) but also on high terraces and watersheds (Aleksandrovsky and Aleksandrovskaya 2005). According to palaeobotanical and archaeological data, vast open local areas of a few square kilometers each of meadows and fields with stable borders were formed around the settlements. There is evidence of deforestation not only in floodplains, but also in valleys of small rivers, quite far away from the Moscow River (Ershova et al. 2014, 2016). In general, the borders of agricultural lands were relatively conservative. Even in the early period of farming (more than 2000 years ago), a significant part of the interfluvial plains passed through the stage of agricultural use. An example is offered in most of the soils in the Gorki Nature and History Reserve (Moscow region) that passed through the cycles of “forest-tillage-forest” or “forest-tillage-­ meadow-forest” during that period (Korotkov 2000; Onishchenko 2000). Near the Gorki closer to Podolsk, a buried arable horizon with a thickness of 7–8 cm was found under the mound of a Dyakovian town settlement (sixth century BC). Similar horizons were revealed under the mounds of town settlements of the same culture dating from the second to first centuries BC (Aleksandrovsky and Krenke 1993). Before the Slavic colonization, however, agriculture must have been irregular, being mainly practiced near the settlements close to rivers and lakes. On the whole the forest landscape was maintained. The spread of arable farming in the area of hemiboreal forests was associated with the Slavic colonization which took place in different parts of the region from the sixth to eighth centuries AD (Istoria krestyanstva v SSSR… 1987a, b; Krasnov 1987). In different parts of Central European Russia, arable farming spread much more widely on watersheds during the internal colonization of the Slavs from eighth to eleventh centuries. Zheligovsky (Artsikhovsky 1934, cited by Komarov 1951) showed a rapid growth of iron axe usage in the ninth to eleventh centuries. Most popular were special wood-cutting axes, the efficiency of which was even higher than that of modern axes. The clearing of forests for permanent arable lands fundamentally changed the appearance of the landscape. According to archaeological and palaeoecological data, in the Middle Ages the boundaries in the landscapes that were modified by man because of agricultural usage became much more mobile and covered a much larger area compared to the Iron Age (Ershova et al. 2014). Large

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areas of dark-coniferous  – broad-leaved forests had been cut for meadows and fields. After abandonment of these agricultural lands, forests dominated by Betula spp. and Pinus sylvestris developed on those lands. The appearance of a new variant of fallow agriculture, the three-field system, is related to the land colonization in the eleventh to thirteenth centuries (Agrikultura.. 1936; Istoriya krestyanstva v SSSR… 1987b). At the same labor input, the system was 50% more efficient than the two-field system (Istoriya krestyanstva v Evrope… 1986; Milov 1998). The three-field farming put the crop yield into a direct dependence on the quality of cultivation and fertilization of the land. The soils commonly found under settlement and burial mounds in central European Russia are old arable soils dated from the tenth to twelfth centuries. This is related to both the wide spread of arable farming during that period and the conditions of conservation of those soils (Nizovtsev and Onishchenko 2000). In the eleventh to twelfth centuries, watersheds in the central and northwestern regions were almost all reclaimed. The thickness of the arable horizon of soils lying under the burial mounds of the twelfth to thirteenth centuries is usually less than 10 cm. Quite often, these soils are eroded, which indicates their long period of exploitation (Aleksandrovsky and Krenke 1993). In a significant part of the hemiboreal region, arable farming and its related soil erosion became widest spread between the eleventh to fourteenth centuries (Aleksandrovsky and Krenke 1993; Sycheva and Gribov 2003; Aleksandrovsky and Aleksandrovskaya 2005). In the tenth to thirteenth centuries, for every 5–10 fortified village and town settlements located in the area of the present-day Moscow region, there were 150–300 (and sometimes up to 500) “open” village settlements. Kolchin and Kuza (1985) showed that a single open village settlement occupied a territory of about 10 km2. A similar value is calculated from the number of the known burial mound groups, corresponding to the settlements of the Slavs (Krivichi and Vyatichi) dated at before the thirteenth to fourteenth centuries (Abaturov et al. 1997). The same settlement area (about 10 km2) is indicated for villages of the fourteenth to fifteenth centuries which were southern possessions of the Land of Novgorod: those villages stood 1–2 km apart from each other in a checkerboard pattern (Burov 1994) and usually included 1–2 households. Analyzing the arrangement of villages in the basin of the Oka River, Fekhner (1967) also noted a high population density in the area at the beginning of the second millennium; she estimated the distance between villages at 3–5 km. In the fourteenth to fifteenth centuries the population periodically decreased and farmed lands became abandoned. Yet, on the whole the tendency of a growing population, including immigration from the south-western areas, continued. The settlement system developed in the fifteenth century lasted over time. In the fifteenth century only 0.1% of the population of the Rus lived in large settlements containing 50 or more households (Kulpin and Pantin 1993). 70% of the population lived in one/two-household villages and 19% in three/four-household villages. In the first half of the sixteenth century, the average size of villages in most parts of the Rus increased to 5–10 households (Rozhkov 1899). By the beginning of the sixteenth century the area of arable lands in the center of the Russian Plain was highest

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Fig. 4.1  Miniature from the Illustrated Chronicles of the sixteenth century [Litsevoy Letopisnyi Svod], showing the main agricultural techniques, such as ploughing by twin-jag sokha, sowing, reaping of grain by sickles and stock farming

(Fig. 4.1) and the boundaries of those lands became relatively stable (Kulpin and Pantin 1993). Even the poorest lands were reclaimed (Agrarnaya istoriya… 1974). From the fifteenth to the beginning of the sixteenth century Russian peasants constantly “struggled for land” (Gorsky 1973). At that time, the total area of arable lands considerably exceeded the capacity to fertilize (manure) these. The growth in area of arable lands, without the capacity to fertilize these, led to depletion and degradation of soils. As a result, peasants had to abandon their farms after using them for some time. With the absence of proper fertilizing techniques in the fifteenth and sixteenth centuries, a compromise measure, which helped to maintain soil fertility, was the short-term field-forest shifting system. The system became widespread at that time among the households in the forest region (Shapiro 1987; Danilova 1998, etc.). In the short-term field-forest shifting system, a piece of land was used for cultivation until the soil lost its fertility (in about 10–20, rarely 30 years), and then the land was abandoned to get the soil properties restored during the free development of the vegetation, similarly as in slash-and-burn agriculture. However, the duration of “rest” of the land was not long and amounted to 10–15, rarely 20 years. During the “rest period” the land became overgrown by forest which was subsequently cleared (the forest was cut) and burned. Often the fallow was used for some time as a pasture. Among others, the field-forest shifting system was a means of weed and sod control; and it provided firewood. As forests were cleared for farms the intensive cutting resulted in a significant reduction of the forested area in most of the central regions of Russia. According to Rozhkov (1899), in the sixteenth century, the relative area occupied by forests did not exceed 10% in most of the provinces (uezds) in the central parts of Russia; and it shrank to 6% in some provinces. In the middle of the seventeenth century the deforestation in the central provinces was linked to the bestowal of state lands to new officials and the binding of peasants to land plots. Where areas of land ploughed

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Fig. 4.2  A. Mayerberg’s drawings: (a) Gorodnia, (b) Bell tower; both are in the Tver region, 1661 (From the Mayerberg Album, 1903)

by landlords agglomerated, large areas became practically devoid of forest (Fig. 4.2), and remained so until the middle of the twentieth century (Ponomarenko et  al. 1996). Probably especially in the Middle Ages the most significant changes in composition and structure of the vegetation of the hemiboreal region occurred. Because of the large disturbances in forest cover due to ploughing, burning and other activities, the distribution areas of many plant species decreased and subsequently did not recover. Due to differences in farming styles, areas with a primary proliferation of certain types of tree species or tree species assemblages were formed. Within the hemiboreal region more “taiga” and more “broad-leaved” forest areas were created and, in general, forests dominated by Betula spp. and Pinus sylvestris began to occupy a significant proportion of the area. The strong transformations of forest cover resulted in a change in climatic conditions (Brovkin et al. 1999; Govindasamy et al. 2001; Matthews et al. 2003). Taking into account the influence of forest vegetation on climate, one cannot rule out that the temperature declines of the end of the thirteenth to the beginning of the fourteenth and again at the end of the fifteenth to the beginning of the seventeenth centuries (“the Little Ice Age”) were linked to the maximal deforestation of the territory. The social consequence of the “great Russian ploughing up” was the economic crisis at the end of the sixteenth to the beginning of the seventeenth centuries (Kulpin and Pantin 1993), which essentially drew a line beneath the medieval era in central Russia. The aftermath of the crisis had the strongest impact on the development of the northwestern region, where the population significantly decreased and vast areas of arable lands were abandoned. Since then the same total number of village settlements in that region has not been reached again (Burov 1994). The dynamics of arable farming is reflected in the structure of deluvial deposits. For example, in the region of Old Radonezh (present-day Moscow region) gullies were intensively filled with agrogenic deluvium in the fourteenth and fifteenth centuries. In the sixteenth to seventeenth centuries, the intensity of erosion decreased due to the decline in the number of settlements and the area of arable lands in the region (Chernov 1987). In the sixteenth to seventeenth centuries the area of arable lands became reduced in the central and north-western provinces of Russia; as the

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people moved from west to east and north-east within the hemiboreal region, new arable lands were created there. Changing the structure of the soil during ploughing, especially its compaction, led to waterlogging on flat and low-inclined areas with loamy soils. Throughout the center and north-west of the Russian Plain there is an increase in intensity of peat accumulation processes during the last 500  years (Klimanov and Sirin 1997). Analyses of pollen diagrams show that during the last 200 years the rate of eutrophication has no analogues throughout the Holocene (Novenko 2011). Simultaneously there was a decrease in broad-leaved trees and an increase in the proportion of Betula spp. The highest rates of change in landuse activities within the same area (land rotation) were registered in the central regions, where the population density and the diversity of anthropogenic impacts were highest (Ofman et al. 1998). The agricultural problems that gave rise to the crisis at the turn of the sixteenth to seventeenth centuries were partially solved at the expense of an agrarian colonization of new territories (in the Volga River basin, southern steppes, Siberia and the Far East). Yet, in the sixteenth to twentieth centuries, soil degradation and depletion had become a major problem for the peasants of the central and north-western provinces of Russia. A complex landuse system was developed in the fifteenth to sixteenth centuries and persisted without substantial changes till the end of the nineteenth or beginning of the twentieth century. The system combined three-field farming with the short-­ term field-forest shifting system and even slash-and-burn in remote areas (Milov 1998). The farming lands gradually became specialized, and relatively strict relationships between the type of the land and its position in the landscape were established (these relationships can be traced up to the present time). Watershed areas were mainly occupied by arable fields (three-field plots, fallows), whereas hayfields were located in floodplains and at ravine and gully bottoms. The contours of these traditionally cultivated lands became quite conservative (Ofman et al. 1998). In the nineteenth and beginning of the twentieth century, the area of arable lands increased as areas with the short-term field-forest shifting system were transferred into permanent arable lands, and because of forest felling (Fig. 4.3). Areas covered by forest decreased by about half in the central provinces of European Russia during nineteenth century (from 50 to 25%) (Tsvetkov 1957). By the middle of the twentieth century the forest coverage of the central regions had decreased by half compared to that of the end of the eighteenth century. Despite the social cataclysms, the rural population increased up to the Second World War. During that war there was a sharp decrease in rural population, especially in the west and northwest of the hemiboreal region; large areas of arable lands became abandoned or forest plantations of Picea abies and Pinus sylvestris were set up there after the war. In the second half of twentieth century, boundaries of forests, arable lands, haymaking fields and meadows remained almost unchanged up to the social and economic crisis of the late 1980s and early 1990s. During that time forest grazing was stopped, and large areas of arable land and meadows were abandoned (Vuichard et  al. 2008; Lyuri et al. 2010). In the west, the proportion of abandoned lands was much higher than in the center or in the east of the hemiboreal region: for example, in the decade

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Fig. 4.3  S. Prokudin-Gorskii’s photo “Monks at Work”, 1910. Monks plant potatoes in a field at the Gethsemane Hermitage of Nil’s Monastery in the Tver region. There is a clear-cut area for ploughing in the background (From Prints and Photographs Division, Library of Congress, LC-DIG-ppmsc-04443 (37.1))

f­ ollowing 1989 46% of the total of agricultural lands was abandoned in the Smolensk region, 28% in Ryazan, and 27% in the Vladimir region (Prishchepov et al. 2013). As a result, in central European Russia the proportion of lands covered by forests at the end of twentieth century was similar to that observed in the end of the eighteenth century (Bobrovsky 2010). Other anthropogenic effects that had a very significant impact on forest cover were the cutting and planting of forests during the last centuries. In the Middle Ages and more recently, practically throughout Europe, the cycle of forest cutting varied from 10 to 30 years, averaging at 18 years (Rozas 2003). The same duration of the cycle is given for the peasant forests in Central European Russia (Statisticheskoe opisanie… 1898). In the central and southern provinces of Russia, firewood coppices occupied the major part of the forest-covered area, with the area of timber forests rarely exceeding 10%. Where firewood deficiency quickly

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increased, the exploitation of coppices helped to avoid the complete elimination of forests (see Arnold 1891). Up to the middle of the twentieth century firewood made up 70–90% of the total wood utilization in the rural areas. Many settlements in European Russia started to experience severe shortages of firewood not later than at the beginning of the nineteenth century. In 1839, for example, the government established a committee to tackle the problem of rocketing firewood prices in Moscow. Already at that time, most of the firewood supplied to Moscow was shipped not by water, as before, but by cartage (Nesterov 1952). At the end of the nineteenth century, the firewood carts going to Moscow traveled long distances (more than 50 km), which indicates the extreme deforestation of Moscow’s outskirts (Tursky 1884). To satisfy the needs of St. Petersburg firewood was shipped from Finland (Myllyntaus and Mattila 2002). Firewood consumption started to decrease gradually from the middle of the nineteenth century, when peat, coal and other fuel were put to use (i.e., Moscow began to use peat and coal since 1841 and 1854, respectively; Nesterov 1952). Throughout Europe, peaks in firewood consumption were registered during the First and Second World Wars (Myllyntaus and Mattila 2002). In the rural areas of European Russia, firewood consumption substantially decreased only in the 1970s, when settlements started to receive natural gas. The exploitation of forests for timber was extremely uneven. For a long time, the main purpose of timber use was for building, with most of the cutting associated with the restoration of villages and towns after fires. Those fires were common and frequent events. In Moscow, for example, chronicles describe 20 devastating fires between 1331 and 1734 (Nesterov 1952). After every fire, timber was needed for restoration and therefore, fires were followed by massive cutting over large areas. Such cutting events occurred up to 10 times per century. The cutting often turned forests into wastelands, pastures and farmlands (Nesterov 1952). There were times when Moscow mainly was supplied by timber from the upper reaches of the Moscow River. Not later than in the sixteenth or seventeenth century, timber started to be shipped from the lower reaches of the Moscow River, from the Oka River basin (Tula, Kaluga, Ryazan and other regions). As indicated by various sources, a practice, which started not later than in the seventeenth century and which was common also in the rural areas of many central provinces in European Russia, was to export timber for building constructions from other provinces and regions. It is believed that massive logging began in Europe in the second half of the seventeenth century. In various regions of Europe, the volumes of logging significantly increased in the 1840–1880s because of the explosive growth of industry (Linder and Ostlund 1998; Ericsson et al. 2000). In Russia, logging increased significantly in the first half of the nineteenth century. The main consumers of timber were factories, plants, steamship companies and later, railroads. High quality timber was used by the navy (ship timber), as well as the artillery (thick-log timber). This period of forest history in central European Russia is described in the literature in great detail (see Arnold 1895; Turchanovich 1950; Tsvetkov 1957, etc.). After the liberation of the serfs in 1861, forest eradication in European Russia increased, first of all, in the domains of landlords (Tsvetkov 1957). Industrialists

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bought huge forest areas from landlords and cut the forests down to the roots, without a second thought about reforestation. As a result, in 20–30 years most of the mature forests of Central Russia were cut. Degradation of arable lands and fast deforestation caused a massive ecological crisis in European Russia with grave consequences (Ponomarenko et al. 1996). The total cutting of forests on sandy soils led to the denudation of the sands: the fields of a few provinces became literally buried under shifting sands (Arnold 1895; Tsvetkov 1957). The forests alongside large rivers, which were suitable for rafting, were cut down everywhere in the central and western provinces. With the forests their water- and climate-regulating functions were eliminated and droughts in the central regions of Russia became more frequent and severe. A horrible drought-caused famine of 1891 shocked the empire and led to the death of millions of people (Ponomarenko et al. 1996). The devastation of forests was slowed down owing to the forest-protection law of 1888. The law of 1899, which imposed a tax upon timber merchants, became the basis for regular forestation of logged sites and areas devastated earlier. By 1914, most of state forests of the central provinces consisted of forest plantings of diverse age. In general, in the center of European Russia, the most extensive cutting of forests occurred in the eighteenth to nineteenth centuries, as well as during the world wars. In the twentieth century, the history of forest exploitation in the northern part of the hemiboreal region is similar to that in the boreal forest region. The most intensive logging was in the 1930s, and again in the 1950s–1970s; many areas have been logged twice. Logging in remote locations led to a great loss of wood partly due to the construction of temporary wooden roads which were built only for timber transport (Fig.  4.4). Timber losses were also great during the drift floating of logs (Fig. 4.5). Timber drift floating was reduced at the end of the 1960s and was totally prohibited in Russia in 1995 according to the Water Law of the Russian Federation (1995, 2006). Since the 1960s summer clear-cuts with heavy machines, leading to severe disturbances in the soil and the ground layer of the vegetation, have been widespread in the region (Figs. 4.6 and 4.7). The absence of a tree undergrowth after such felling, together with the large areas of the clear-cuts and the short time interval between felling rounds on the same area, led to the domination of birch and aspen-birch forests in the greater part of the area (Yaroshenko et al. 2001; Fig. 1.8). Forest fires have also played and continue to play a significant role in the transformation of the structure and composition of the hemiboreal forests just as in the boreal region. Causes of fires and their distribution in different forest types are similar to those in the boreal region. Charcoal in soils and carbon layers in bogs are common throughout the entire region, but there are practically no data (including dendrochronological ones) on the reconstruction of the fire history of concrete areas. Taken together, the proportion of secondary forests, formed after severe anthropogenic disturbances during the last century in the hemiboreal region of European Russia, is estimated at not less than 4/5 of the total forested lands there (Smirnova 2004). With that, forests dominated by dark-coniferous and broad-leaved trees, as

Fig. 4.4 Temporary wooden road for timber transportation. The photo was taken in the Kostroma region in the middle of the twentieth century (From Dudin 2000)

Fig. 4.5  An obstruction in the drift floating of timber in the Unzha River in the Kostroma region. The photo was taken in the middle of the twentieth century (From Dudin 2000)

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Fig. 4.6  A clear-cut area replacing a mature Picea abies forest in the Kostroma region. So far only spruce has been cut, since Populus tremula, being a low-value timber, is disregarded in this area (The photo was taken in 2003 by M. Bobrovsky)

Fig. 4.7  Damage to the soil and the ground layer of the forest vegetation after a clear-cut (The photo was taken in 2003 in the Kostroma region by M. Bobrovsky)

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said earlier (see Sect. 1.3), occupy only 4% of the forested area of this region. Forests have been transformed as a result of a complex combination of clearings and ploughing, different types and intensities of harvesting, fires, grazing, burning operations, etc. A significant role in the transformation of forest ecosystems played the selective cutting of trees for household purposes, the collection of forest litter, the storage of twig fodder, etc. Ways and intensity of forest transformation varied widely over the region and led to a lot of different successional variants of forest ecosystems nowadays.

4.2.1  Conclusion The hemiboreal region in European Russia is an area of ancient landuse practices. The region differs from other forest regions in its highest diversity of landuse practices and their intensity. Agriculture and forestry have been developed here earlier and over larger areas than in the boreal region. Agriculture played a significant role in the transformation of the forest cover. Time and extent of deforestation and agrarian activities varied significantly in different parts of the region.

4.3  T  ypical Features of the Best Preserved Hemiboreal Forests in European Russia (on Examples of the Visimskiy and Sabarskiy Reserves and the Kilemarskiy Zakaznik) In the European part of Russia, hemiboreal forests are more strongly affected by man than forests in the boreal region. In the hemiboreal region, fragments of forests with characteristics of late-successional stages (which were described in Sect. 2.5) occur more often in the eastern part of the region: on the Russian Plain from the Vetluga River basin eastward, and in the piedmont plains of the Ural and in the Ural Mts (Gribova et al. 1980). In this section, we describe the typical features of the best preserved Abieto-­ Piceeto-­Tilieta boreo-nemoro-magnoherbosa forests from three study areas located in the Nizhny Novgorod and Sverdlovsk regions. They comprise the Kilemarskiy Zakaznik located in the east of the central part of the Russian Plain (number 23  in Fig. 2.1), the Visimskiy State Nature Reserve and the Sabarskiy Zakaznik, the latter two study areas lying both on the western macroslope of the Middle Ural Mts (numbers 27 and 28 in Fig. 2.1, respectively). The Kilemarskiy Zakaznik, 100–145  m asl, is situated in the Vetluga River basin. The area is dominated by small, smooth ridges covered by a thin layer (up

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to 2 m) of periglacial and moraine loams (Shirokov 1998). Our study area in the Visimskiy Reserve is located in the western part of the Reserve, in a low-mountainous terrain (550–650 m asl), along the upper reaches of the right-hand tributaries of the Chusovaya River (the Kama River basin) (Turkov and Kolesnikov 1977). The Sabarskiy Zakaznik is situated in the south-west of the Sverdlovsk region (in Arti province), within the Ufa River basin; its elevation is 250–450 m asl (Samokhina 1997); it predominantly has a hilly-ridge relief with rounded tops (elevation of the ridges is 50–100  m) and gentle slopes (Popadyuk et  al. 1999). The main features of the climate and macro-relief of the areas are described in Chap. 1. The history of anthropogenic impacts in the study areas is as follows. The Sabarskiy Zakaznik and Visimskiy Reserve are located in the Middle Ural Mts, where mining and metal productions have been developed since the eighteenth century. Charcoal was used as the primary fuel for smelting iron and copper, so all forests located in regions of metallurgical plants were under their special management (RGIA according to Popadyuk et al. 1999): areas of the Visimskiy Reserve and Sabarskiy Zakaznik were under control of the Nizhny Tagil (established in 1725) and the Arti (est. in 1787) metallurgical plants, respectively. That means that uncontrolled cutting as well as uncontrolled clearing and ploughing of forest lands were absent during the eighteenth and nineteenth centuries; but on the whole, volumes and areas of felling were huge and clear cuttings were absent only at the areas furthest away from the metallurgical plants (Terinov 1970; Panova and Makovsky 1979; Turkov 1979). The Kilemarskiy Zakaznik is located in the north-east of the Nizhny Novgorod region. Arable farming, stall cattle breeding with permanent pastures and haymaking meadows had already been developed in the region in the eighteenth century (Milov 1998), even though there was a considerable depopulation in that region from the beginning of the thirteenth to the middle of eighteenth centuries in response to nomadic raids (Ofman et  al. 1998). Logging was widespread in the region during eighteenth and nineteenth centuries (Krzhivoblotsky 1861). Logging was ended in the study area only after the proclamation of the Zakaznik in 1987. The best preserved forests in all three protected areas are old-growth forests dominated by Picea abies (in the Kilemarskiy Zakanik) or Picea obovata (in the two other study areas), Abies sibirica and Tilia cordata in the overstorey and boreal and nemoral tall herbs and ferns in the understorey (Zubareva 1967; Zubareva and Terinov 1967; Turkov and Kolesnikov 1977; Turkov 1979, 1980, 1985; Turkov and Turkova 1985; Samokhina 1997; Shirokov 1998; Popadyuk et al. 1999; Belyaeva 2001, 2007; Sibgatullin 2001, 2006; Marin 2006). Such forests presently cover about 100 km2 in the Kilemarskiy Zakaznik and 10–15 km2 each in the Visimskiy Reserve and Sabarskiy Zakaznik. All studied tall herb dark-coniferous  – broad-­ leaved forests are located on watersheds or slopes with good drainage. Clayey and loamy soils, sometimes with crushed stones, are typical for the foothill areas.

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Luvisols dominate in the study forests in the Kilemarskiy Zakaznik (Shirokov 1998) and brown soils (Cambisols) prevail in the described forests in the Visimskiy Reserve and Sabarskiy Zakaznik (Zubareva 1967). The vegetation was sampled in 1989–1994 in the Sabarskiy Zakaznik, in 1995– 1998 in the Kilemarskiy Zakaznik and in 2005–2006 in the Visimskiy Reserve. In each of the three study areas 35–70 phytosociological relevés were sampled in square plots of 100 m2. Vascular plant diversity was assessed according to the methods described in Sect. 2.5. Tree species populations were studied in tree sample plots ranging in size from 10,000 m2 to 20,000 m2 (with 2–4 plots in each study area). Within the plots, species name, ontogenetic stage, vitality, tree diameter at breast height and tree height were registered for tree individuals beginning from their virginal stage; for selected ­individuals, absolute age based on tree cores was determined. Juvenile and immature tree individuals were counted in 500 small plots of 1x1 m. Trees at ontogenetic stages from virginal to old-reproductive were mapped. Clusters of undergrowth and gaps in the tree canopies (with a coverage of less than 10%) were also mapped. The microsite structure of the ground layer linked with the life and death of tree species was analysed in the Visimskiy Reserve. Stages of wood decay after tree fall, with analysis of plant and fungi species dominating at each stage of deadwood decay and overgrowing, were described from the Kilemarskiy Zakaznik.

4.3.1  V  ascular Plant Diversity in the Tall Herb Dark-­Coniferous – Broad-Leaved Forests The dark-coniferous trees Picea abies (in the Kilemarskiy Zakaznik), Picea obovata (in the eastern study areas) and Abies sibirica (in the three study areas) dominate in the overstorey together with broad-leaved trees from which only Tilia cordata occurs and co-dominates with the coniferous trees everywhere. The other broad-leaved trees Ulmus laevis, Acer platanoides and Quercus robur occur only in the Sabarskiy Zakaznik, where Ulmus laevis often participates in the overstorey; Acer platanoides mainly occurs in the undergrowth and Quercus robur sometimes occurs in the glades. Pinus sylvestris and P. sibirica (in the east) can be rarely found as single trees in the overstorey. The small-leaved deciduous trees Betula pendula, B. pubescens, Populus tremula, Alnus incana, Sorbus aucuparia and Padus avium also occur in the stands in all three study areas. Besides the boreal shrubs Daphne mezereum and Lonicera pallasii, the nemoral shrubs Euonymus verrucosa, Lonicera xylosteum, Viburnum opulus, Rosa canina, R. majalis, etc. often occur in the understorey. In the field layer, in addition to nemoral and boreal small and medium herbaceous plants, boreal and nemoral tall herbs and ferns often occur as well as nitrophilous plants (Fig.  4.8); spring-growing and –flowering herbs are also

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Fig. 4.8  The tall herbs Aconitum septentrionale, Crepis sibirica and Filipendula ulmaria in the Abieto-Piceeto-Tilieta boreo-nemoro-magnoherbosa in the Sabarskiy Zakaznik (Photo by M. Barinova and O. Barinov)

Fig. 4.9  The spring-growing and -flowering herbs Corydalis solida (left) and Anemone uralensis (right) in the Sabarskiy Zakaznik (Photo by M. Barinova and O. Barinov)

common (Fig. 4.9). A high plant species richness is a typical feature of these forests, but species of the water-marsh, oligotrophic and piny ecological-coenotic groups are practically absent (Table 4.1; Fig. 4.10). The total species richness of vascular plants is highest in the Sabarskiy Zakaznik: it comprises 153 species against 86

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Table 4.1  List of constant species of herbaceous plants occurring in more than 60% of the vegetation sample plots in Abieto-Piceeto-Tilieta boreo-nemoro-magnoherbosa forests in the Sabarskiy and Kilemarskiy Zakazniks and in the Visimskiy Reserve Group Br_m Br_m Br_m Br_m Br_m Br_m Br_m Br_m Br_m Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nm Nt Nt TH_Br TH_Br TH_Br TH_Br TH_Br TH_Br

Species Anemonoides reflexa Circaea alpina Equisetum sylvaticum Gallium boreale Gymnocarpium dryopteris Maianthemum bifolium Oxalis acetosella Solidago virgaurea Trientalis europaea Adoxa moschatellina Aegopodium podagraria Anemonoides altaica Asarum europaeum Brachypodium pinnatum Corydalis solida Dryopteris carthusiana Gagea lutea Galium odoratum Lathyrus vernus Melica nutans Milium effusum Paris quadrifolia Polygonatum multiflorum Pulmonaria obscura Stellaria holostea Viola mirabilis Chrysosplenium alternifolium Stellaria nemorum Aconitum septentrionale Atragene sibirica Cacalia hastata Chamaenerion angustifolium Cinna latifolia Crepis sibirica

Sabarskiy Zakaznik х х х х х

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х

x х

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х х х х х х

х х х х х

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(continued)

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Table 4.1 (continued) Group TH_Br TH_Br TH_Br TH_Br TH_Br TH_Br TH_Br TH_Nm TH_Nm TH_Nm TH_Nm TH_Nm TH_Nm TH_Nm TH_Nm TH_Nm TH_Nm TH_Nt TH_Nt TH_Nt

Species Delphinium elatum Diplazium sibiricum Dryopteris dilatata Geranium sylvaticum Paeonia anomala Senecio nemorensis Thalictrum minus Bupleurum aureum Campanula latifolia Campanula trachelium Cicerbita uralensis Dryopteris filix-mas Festuca gigantea Lathyrus gmelinii Lilium martagon Scrophularia nodosa Stachys sylvatica Urtica dioica Valeriana wolgensis Veronica longifolia Number of species

Sabarskiy Zakaznik х х х х х х х х х х х х х х х х х х х х 54

Visimskiy Reserve х х х х

Kilemarskiy Zakaznik х х

х х х х

х х

х

х х х

х х х х х х 45

х х х х 38

Note: Br_m, Nm and Nt boreal, nemoral and nitrophilous small herbs and ferns, TH_Br, TH_Nm boreal and nemoral tall herbs and ferns, TH_Nt nitrophilous tall herbs

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Fig. 4.10  Number of vascular species of different ecological-coenotic groups in the field layer in the tall herb dark-coniferous – broad-leaved forests in the study areas. Ecological-coenotic groups: Br_dw boreal dwarf shrubs, Br_m boreal small herbs and ferns, TH_Br boreal tall herbs and ferns, TH_Nt nitrophilous tall herbs, TH_Nm nemoral tall herbs and ferns, Nm nemoral, Nt nitrophilous, Md meadow-edge groups

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species in the Visimskiy Reserve and 78 species in the Kilemarskiy Zakaznik. The average number of species in the field layer decreases in the same sequence from 46.8 in the Sabarskiy Zakaznik, via 39.3 in the Visimskiy Reserve, to 33.4 in the Kilemarskiy Zakaznik. The lower species diversity in forests of the Kilemarskiy Zakaznik probably is due to the stronger past anthropogenic impacts there: the vegetation of the ground layer recovers faster in (selectively) logged areas than on the formerly ploughed lands which are more common in the Kilemarskiy Zakaznik; the past anthropogenic impacts also correlate with richer Cambisols (burozems) in the first two areas and poorer Luvisols in the Kilemarskiy Zakaznik study area.

4.3.2  O  ntogenetic Structure of Tree Populations and Patchy Structure of Tall Herb Dark-Coniferous – Broad-Leaved Forests Structural peculiarities of the tree communities in the best preserved fragments of the hemiboreal forests are the following: (1) dark-coniferous and broad-leaved trees dominate in all vegetation layers; (2) the individuals of the tree species are proportionally represented in all ontogenetic stages and thus guarantee a steady flow of the tree species generations, and (3) a patchy pattern in the spatial structure of the tree community (parcel structure of a tree community), caused by gaps in the canopy formed as a result of tree falls, is clearly visible. The spatial structure of the forest community, that developed during a long time without external impacts, is determined by the spatial-temporal parameters of population mosaics of the late-successional tree species (Kurnaev 1968; Smirnova 1994, 2004; Smirnova and Bobrovsky 2001); in the hemiboreal forests such species are dark-coniferous and broad-leaved trees. Diversity in heights of different tree species at different ontogenetic stages, diversity of life durations of dominant species (Table 4.2), together with diversity of treefall mosaics cause the spatial heterogeneity of old-growth hemiboreal forests and that determines a high diversity in ecological conditions and a high species richness in the subordinate layers: a diversity in shrubs, herbaceous and cryptogamic species.

Table 4.2  Duration of ontogenetic stages of tree species dominating in the Kilemarskiy Zakaznik (Shirokov 2005) Species Picea abies Abies sibirica Tilia cordata

Duration of ontogenetic stages (years) j im1 im2 v1 v2 g1 1–5 5–15 10–20 10–20 10–20 20–30 1–5 5–10 10 10–15 10–15 20–30 1–5 5–10 5–15 10–15 10–15 15–20

g2 40–60 40–50 30–40

g3 70–80 70–80 30–50

s 2–5 2–3 2–3

Total (years) 170–260 170–220 110–180

Note: j juvenile; im1–im2 immature first and second, v1–v2 virginal first and second, g1–g3 reproductive first, second and third, s senile ontogenetic stages as described in Sect. 2.5

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There are several sublayers in the tree layer of the tall herb dark-coniferous – broad-leaved forests. In these forest in the Sabarskiy Zakaznik four layers were distinguished (Samokhina 1997). The height of the first layer was about 30 m in the tree sample plots. Picea obovata was the highest and reached 36  m. Heights of Abies sibirica and Tilia cordata in the first layer were about 25 m. Height of the second layer was about 20  m; Picea obovata and Abies sibirica also dominated there; height of Tilia cordata ranged from 15 to 18 m. In the third layer, all trees were about 10  m tall and their heights were limited by the poor light conditions under the higher tree crowns. The fourth tree layer (5–7  m height) consisted of undergrowth of all species and some reproductive individuals of deciduous species with low vitality. In populations of the main dominant trees (Picea spp., Abies sibirica and Tilia cordata), individuals at all ontogenetic stages, with the highest numbers of young specimens, occurred in all study areas (Samokhina 1997; Shirokov 1998; Shirokov et al. 2006) (Fig. 4.11); this seems to guarantee a steady flow of the generations of these species. An example of the ontogenetic structures of populations of eight tree species in the sample plots located in the Sabarskiy Zakaznik (Fig. 4.12) shows that species with smaller numbers (Ulmus laevis, Alnus incana, Sorbus aucuparia, Acer plat-

Fig. 4.11  Uneven-aged forest dominated by Picea abies, Abies sibirica with Tilia cordata in the Kilemarskiy Zakaznik (Photo by A. Shirokov)

O.V. Smirnova et al.

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Fig. 4.12  Ontogenetic structures and vitality (normal and low) of the main tree species populations in the tall herb dark-coniferous – broad-leaved forest in the Sabarskiy Zakaznik (according to Samokhina 1997). Numbers of stems per hectare are presented on a logarithmic scale

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anoides and Padus avium) have structurally similar ontogenetic spectra as the dominants. Very low numbers and absence of individuals at different ontogenetic stages (discontinuous spectra) were found for Betula spp., Pinus sylvestris, P. sibirica, Quercus robur, Salix caprea and Populus tremula. This can be explained by the ­pioneer character of these species or by their wide use in industrial applications (especially Pinus sylvestris and Quercus robur), as in everyday life by local people. For example, Populus tremula was widely used in nineteenth and twentieth centuries in the Sabarskiy region for making things ranging from gouged boats to dishes and for other household needs (oral reports from local residents). Nested plots of increasing size were sampled in order to calculate for the main tree species the minimum areas on which individuals of those species at all ontogenetic stages do occur. In the forests in the Sabarskiy and Kilemarskiy zakazniks, this area ranged from 2 to 3 ha for Picea spp. and from 1 to 2 ha for Abies sibirica as well as Tilia cordata (Samokhina 1997; Shirokov 1998). Considering the sizes of areas required for properly functioning populations of the other tree species, we assume that 4–6 ha is the minimum area on which the diversity in composition and structure of the plant communities in the hemiboreal forests can properly persist (Smirnova et al. 2000). Patchy patterns in tall herb dark-coniferous – broad-leaved forests were studied by mapping the trees and counting the individuals of different tree species at different ontogenetic stages in patches located in the sample plots (Samokhnia 1997; Shirokov 1998, 2004, 2005; Shirokov et al. 2006; Shirokov and Syrova 2010). The ontogenetic spectra of tree species in patches dominated by different trees in the sample plots of the Sabarskiy Zakaznik (Fig. 4.13) show a high diversity in tree species and trends of dynamic changes in the composition of the overstorey: for example, a patch dominated by Picea obovata (Fig. 4.13a and b) will probably change into the domination of Tilia cordata, but we do not expect big changes in patches dominated by other tree species (Fig.  4.13c-f), though Tilia cordata and Ulmus laevis may increase their participation in the overstorey in those patches. The proportions of closed patches and gaps in the canopy vary greatly in the plant communities studied and the sizes of gaps also vary (Table  4.3). Therefore trees with different light demands can regrow in gaps of different sizes. Several stages of vegetation development after the formation of a gap in the forest canopy were described (Samokhina 1997; Shirokov 1998; Shirokov et al. 2006) and the stages were very similar in the three study areas: as a tree has fallen down and a gap in the canopy has been formed, crowns of trees surrounding the gap begin to grow laterally; undergrowth of shade-tolerant trees preserved under the closed canopy begins to increase in height and some new plants establish and start to develop. Vascular plants dominate and often occur at corresponding stages of overgrowing of gaps in practically the same way in all three study areas. The main stages in the overgrowing of gaps, described from the Sabarskiy Zakaznik (Samokhina 1997), are the following:

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Fig. 4.13  Number of tree individuals at different ontogenetic stages (% and numbers per hectare presented on a logarithmic scale) in patches dominated by Picea obovata (a and b), Abies sibirica (c and d) and Picea obovata, Abies sibirica and Tilia cordata (e and f) in the sample plots located in tall herb dark-coniferous – broad-leaved forests in the Sabarskiy Zakaznik

1. ‘A new gap’ is formed by treefall. Then the reactive species Urtica dioica and Rubus idaeus start dominating. Cover of the field layer is about 100%. Such new gaps occupy about 4% of the tall herb dark-coniferous  – broad-leaved forests. 2. ‘A young gap’: large nitrophilous, boreal and nemoral herbs and ferns together with the nemoral forest species Aegopodium podagraria begin to dominate

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Table 4.3  Proportions of gaps and closed canopies in tall herb dark-coniferous – broad-leaved forests in the hemiboreal region (According to Samokhnia 1997; Shirokov 1998, 2005; Shirokov et al. 2006; Shirokov and Syrova 2010) Study areas Kilemarskiy Zakaznik Sabarskiy Zakaznik Visimskiy reserve

Closed canopy (%) 95–60 95–65 90–55

Gaps in the canopy (%) 5–40 5–35 10–45

Size of gaps (m2) smallest average 75 210 110 310 20 85

largest 670 910 240

Fig. 4.14  Young gap with Angelica archangelica, Filipendula ulmaria, Rubus idaeus and others in the Abieto-Piceeto-Tilieta boreo-nemoro-magnoherbosa in the Sabarskiy Zakaznik (Photo by M. Barinova and O. Barinov)

(Fig.  4.14). Cover of the field layer is practically 100%. Such ‘young gaps’ occupy about 5% of the community area. 3 . The stage of tree undergrowth development. The overgrowing of the gap depends on what kind of undergrowth, deciduous or coniferous trees, prevails in the patch. a. Undergrowth of broad-leaved trees (mainly Tilia cordata; often Ulmus laevis and Acer platanoides; rarely Padus avium and Sorbus aucuparia) begins to shade tall herbs and shrubs. Cover of the field layer is 80% of the area; nemoral and boreal herbs dominate. b. Undergrowth of the coniferous trees Picea obovata and Abies sibirica shade and oppress the herbaceous species; the field layer covers 30–40% of the patch area.

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Patches at the stage of ‘tree undergrowth development’ occupy about 15% of the community area. 4. The stage of forming the stand. Trees form a closed canopy at the height of the third and fourth sublayers of the overstorey. The field layer is dominated by small boreal herbs, such as Oxalis acetosella, Viola selkirkii, Cinna latifolia, etc. The large boreal fern Dryopteris dilatata and nemoral herbs, such as Aegopodium podagraria, Pulmonaria obscura, Stellaria holostea, etc., often occur with small abundance. Green mosses are common. Patches at this stage occupy about 20% of the community area. 5. The last stage of tree stand development. Trees reach the upper overstorey layer and the canopy is closed. This stage, as the previous one, is sufficiently rich in tree species diversity (Fig. 4.3), but both these stages are poorer in diversity of the field layer compared with the other stages. Small boreal herbaceous species prevail in the field layer; nemoral herbs, tall herbs and ferns from other ecological-­ coenotic groups also occur with small abundance. Patches at this stage occupy about 55% of the community area. At the next stage, new trees fall and gaps are formed in the canopy and the cycle is repeated, usually with other boundaries. In all three study areas, cycles of patch development with and without changing in tree dominance were described. In the hemiboreal forests, most typically patches develop in a cycle with a change in dominants. It happens as follows: 1. reproductive individuals of Picea spp. and Abies sibirica dominate in the overstorey; an undergrowth of Tilia cordata of vegetative origin and a heavily oppressed undergrowth of coniferous species dominate in the understorey; 2. coniferous trees fall and that triggers the rapid growth of young Tilia cordata individuals with the suppression of the undergrowth of coniferous trees; 3. reproductive individuals of Tilia cordata dominate in the overstorey and the undergrowth of coniferous trees dominates in the understorey, and 4. Tilia cordata individuals fall from the overstorey which triggers the rapid growth of young coniferous trees. And the cycle is repeated. This cyclic development is possible due to several causes. The first one is the ability of Tilia cordata to reproduce vegetatively and to transfer to elfin and shrub forms. It allows her to accumulate biomass while there is a lack of light under the canopy of coniferous trees and ‘to wait’ for improved light conditions for rapid height growth. The second cause is the same ability of Abies sibirica to reproduce vegetatively under adverse light conditions and to accumulate biomass in the elfin form (Fig. 4.15). A third cause is the ability of Picea spp., under low light conditions, to minimize its growth processes and remain at an immature stage with a low vitality for periods of up to 160–170 years and then, at improved light conditions, to get out into the overstorey (Abaturov et al. 1988; Abaturov and Antyukhina 2000; Smirnova 1989; Samokhina 1997; Shirokov 1998; Smirnova et al. 1999; Shirokov et al. 2006; Shirokov and Syrova 2010). Patches without changes in dominants can be found in the stream valleys where the main dominants of watershed communities, Picea spp., Abies sibirica and Tilia

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Fig. 4.15  Abies sibirica in the elfin form in the Kilemarskiy Zakaznik (Photo by A. Shirokov)

cordata, do not always survive to their adult stage and undergrowth of these species constantly emerges from seed originating from neighboring territories (Samokhina 1997). Thus, the patchy structure of old-growth tall herb dark-coniferous – broad-leaved forests, which is a consequence of the gap-mosaic caused by tree falls, is one of the main features of these forests explaining their internal heterogeneity and providing a mechanism of sustainable renewal of these forests under natural conditions (Smirnova 2004; Smirnova and Toropova 2008). Another feature of such forests is the pit-and-mound topography originating from tree fall with uprooting.

4.3.3  M  icrosite Structure and Vegetation Diversity in the Tall Herb Dark-Coniferous – Broad-Leaved Forests Relief heterogeneity caused by tree falls with uprooting facilitates the high diversity of ecological niches for various species groups. In the hemiboreal region, the microsite structure in the ground layer was studied in the Visimskiy Reserve (Zaprudina 2012a, b). Types of microsites caused by treefalls and methods of their analysis are described in detail in Sect. 3.4. Unlike the microsite research in the Pechora-Ilych

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Nature Reserve, areas located between projections of tree crowns and under the crowns were not separately considered in the Visimskiy Reserve; they were studied as a “background area”. The other microsite types studied were the same: elevations close to tree trunks; fallen logs from the first to the fourth stages of overgrowth and decay, and pits and mounds (separately) arising after treefall with uprooting; pits and mounds were also distinguished from the first to the third stages of decay. 10 plots of 10 × 10 m were mapped to calculate the relative importance of microsites of different types in the tall herb dark-coniferous – broad-leaved forest. 10 mounds and pits at all stages of decay were also measured. A list of vascular plants with their abundance was compiled for 100 sample plots of 0.5 × 0.5 m located in the background area and for 30 sample plots per microsite type. Measurements showed that, on average, background areas occupied 43.5% of the community area; microsites caused by treefalls occupied 39.6%, and from this 31% was occupied by fallen logs, 3.4% by mounds and 2.5% by pits. The remaining part of the ground (16.9%) was occupied by the bases of trunks. Mean height of mounds formed by roots of Picea obovata after their fall was 155 cm (Table 4.4); the highest one was 176 cm, the lowest 45 cm and the most frequent 130 cm. The area with vertical relief around a base of a fallen tree was 2.5 m2 on average. At the second stage of decay, the height of mounds had decreased by a factor 3 due to crumbling of soil from the root ball and then, at the third stage of final humification and mineralization of the roots, the height was reduced to only one seventh of its initial size. The depth of pits formed after treefall with uprooting (at the first stage of decay) varied from 10 to 60 cm and averaged at about 25 cm. Pit areas averaged at 2 m2. The depth of pits was reduced by a factor 4 during the transition from the first stage of decay to the third and averaged at about 6 cm at the last stage. At the final stage of decay pits and mounds looked like microelevations and microdepressions on the soil surface. There is another peculiarity of pits formed after treefall in the Visimskiy Reserve: with tree falls stones with diameters of up to 50 cm crop out, because the Reserve is situated in the low-mountainous terrain of the Ural Mts. Stones covered on average 33.5% of the pits and about 12% of the mounds at the first stage of decay (Table 4.4). However, at the second stage (which occurs 25–30 years after treefall) bare stones

Table 4.4  Means and standard deviations of pit and mound sizes caused by fall of Picea obovata in the tall herb dark-coniferous – broad-leaved forest in the Visimskiy State Nature Reserve Type of microsite Mounds

Pits

Stages of decay 1 2 3 1 2 3

Height/depth, cm 154.70 ± 7.33 45.33 ± 3.45 22.23 ± 1.50 24.63 ± 2.29 10.57 ± 0.50 5.97 ± 0.58

Cover by stones, % 11.77 ± 1.76 4.00 ± 1.08 0 33.50 ± 3.48 5.03 ± 1.21 0.67 ± 0.39

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Percent of cover

80 60 V

40

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20 0

Background Elevations area close to tree trunks

Pits

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Fallen logs

Fig. 4.16  Average coverage of vascular plants (V) and bryophytes (M) on the studied microsites in the tall herb dark-coniferous – broad-leaved forests in the Visimskiy Reserve

covered on average only 5% of the pits due to stone coverage by crumbling soil, and only 4% of the mounds because they had slid down into the pit and surrounding areas. Vascular plants covered on average about 48% of the fallen logs and 71% of the background area, while bryophyte species covered on average 62% of the fallen logs and 12% of the background areas (Fig. 4.16). In general, vascular plants and bryophytes in the tall herb hemiboreal forests covered microsites of different types in very similar proportions to those observed in the tall herb boreal forests (see Sect. 3.4): (1) coverage of mosses was lower than coverage of vascular plants in all microsites except on fallen logs where coverage of mosses was highest, and (2) mosses covered minimal areas in the background areas while vascular plant coverage was the highest there. Pits were the richest microsite in number of vascular plants, followed, in descending order, by background areas, mounds and fallen logs (Fig. 4.17 top). Elevations close to tree trunks counted the lowest number of vascular species after logs at the first stage of decay. The largest number of bryophytes occurred on fallen logs, the smallest number on elevations close to tree trunks (Zaprudina 2012a). Mean number of vascular species per plot (species density) was highest in background areas (Fig. 4.18): 11.7 species per 0.25 m2. The same species density was observed in pits at the first stage of decay even though stones covered on average 33.5% of the pit surface (Table 4.4). At later stages, vascular species density slightly decreased in pits (on average 10.4 and 9.5 species per plot at the 2nd and 3rd stages), but the total species richness remained highest there and that indicates the wider variety in ­ecological conditions in pits compared with background areas. On mounds, vascular species density slightly increased from the 1st to 3rd stages (on average 5.6, 6.6 and 8.6 vascular species per plot) and it also increased on fallen logs (2.4, 5.3, 7.6 and 8.1). Shifts in species richness between stages of decay (Fig. 4.17 top) were similar to shifts in species density. At about 6 species per 0.25 m2 vascular species density on elevations close to tree trunks as well as on fallen logs and on mounds (in

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70

Br

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60 50 40 30 20 10 0 Total IC-UC

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Log

Pit1

Pit2

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Mnd1 Mnd2 Mnd3 Log1

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Log3

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100% 80% 60% 40% 20% 0% Microsites

Fig. 4.17  Species richness (top) and ecological-coenotic structure (bottom) of vascular plants growing in the microsites studied in the tall herb dark-coniferous  – broad-leaved forest in the Visimskiy Reserve. Microsites: Total all the microsites; IC-UC background areas; El elevations close to tree trunks; Pits total for all pits; Mnd total for all mounds; Log total for all logs; Pit1-Pit3 pits from the first to the third stages of decay; Mnd1-Mnd3 mounds from the first to the third stages of decay; Log1-Log4 fallen logs from the first to the fourth stages of overgrowth. Ecological-­ coenotic groups: Br small boreal herbs, ferns and dwarf shrubs, TH boreal tall herbs and ferns, Nm nemoral, Nt nitrophilous and Md meadow-edge plants

total values for the latter two microsites), it was similar, though species richness was significantly lower on the elevations. This also indicates a wider variety in ecological conditions on mounds and fallen logs compared to tree trunk elevations. The ecological-coenotic structure of vascular plants calculated for background areas, and total values for pits, mounds and logs was similar (Fig.  4.17 bottom) though some peculiarities should be noted. Boreal species prevailed in all types besides background areas where the proportion of nemoral species was the highest. Overall, fallen logs had the most boreal species, background areas the most nemoral species, pits the most nitrophilous species and boreal tall herbs and mounds the most meadow species (Zaprudina 2012a). Peculiarities in the floristic composition of microsites caused by treefalls with uprooting in the tall herb dark-coniferous – broad-leaved forests were the following: Most of the herbaceous species occurred in all different types of microsites, but there were several species that occurred only at specific microsites (usually with low abundance values). Diplazium sibiricum, Dryopteris carthusiana and Geum rivale were found only in pits; Actaea spicata and Cicerbita uralensis occurred only on

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Fig. 4.18  Abieto-Piceeto-Tilieta boreo-nemoro-magnoherbosa in the Visimskiy Reserve: (a) Lilium martagon in the background area surrounded by Abies sibirica; (b) patch dominated by Tilia cordata; (c) gap dominated by Aconitum septentrionale with Chamaenerion angustifolium and (d) Campanula latifolia among the other tall herbs in the background area (Photos a, b and d were taken by E. Bakun and photo c was taken by T. Prokazina)

sites between tree crown projections. Ferns occurred more often with higher abundance in pits than in other microsites and some ferns, such as Phegopteris connectilis, Dryopteris carthusiana, Diplazium sibiricum and Cystopteris sudetica, did not occur on patches without treefalls (under groups of adult trees) whereas they often occurred in pits. We did not register any vascular plant species to occur only on fallen logs or on elevations close to tree trunks. Many mosses occurred on different types of the microsites, but some bryophyte species have their preferences. For example, Plagiomnium medium, Pohlia nutans and Rhytidiadelphus subpinnatus occurred on all types of microsites. Ceratodon purpureus, Plagiomnium confer-

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tidens and Polytrichum juniperinum were found only on mounds; Lophocolea heterophylla, Plagiothecium laetum, Polytrichastrum longisetum, Rhodobryum roseum and Tetraphis pellucida exclusively occurred on fallen logs. Seedling, juvenile and immature individuals of most trees and shrubs (Abies sibirica, Betula pubescens, Picea obovata, Salix caprea, Sambucus sibirica, Sorbus sibirica and Tilia cordata) occurred on microsites of all types. However, young individuals of Abies sibirica were more frequent on elevations close to tree trunks; Picea obovata often occurred on fallen logs (Fig.  4.19), Betula pubescens and Sambucus sibirica on mounds, Salix caprea in pits, Sorbus sibirica on sites located between and under tree crown projections. Undergrowth of Pinus sibirica occurred sporadically only on mounds and young individuals of Lonicera xylosteum rarely occurred only on sites between projections of tree crowns. On the whole, a total of 66 vascular plant species were found during the microsite study: 57 in the background area and on elevations close to tree trunks and 63 in microsites related to tree fall with uprooting (pits, mounds and fallen logs). These results are similar to results obtained in the microsite study carried out in the boreal tall herb spruce-fir forests located in the Pechora-Ilych State Nature Reserve (Sect. 3.4): more species occur at microsites caused by tree falls. These results confirm the importance of tree falls with uprootings for the maintenance of a high level of plant diversity in the hemiboreal tall herb forests. The total number of species registered in the microsite study in the boreal region was slightly higher than the species num-

Fig. 4.19  Young individuals of Picea obovata on a fallen log and the spring-growing and – flowering herbs Corydalis solida and Anemone altaica on the ground in the Abieto-Piceeto-Tilieta boreo-nemoro-magnoherbosa in the Sabarskiy Zakaznik (Photo by M. Barinova and O. Barinov)

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ber found in the microsite study in the hemiboreal region (70 to 66 species of vascular plants). The main reason is the larger number of vegetation plots sampled in the Pechoro-Ilych Reserve: 850 plots of 0.5 × 0.5 m against to 340 plots of the same size in the Visimskiy Reserve. However, the total area occupied by boreal tall herb dark coniferous forest in the Pechoro-Ilych Resserve is much larger than the area of tall herb dark coniferous  – broad-leaved forests in the Visimskiy Reserve due to stronger anthropogenic impacts in more southern localities.

4.3.4  Features of the Deadwood Decomposition According to the literature (Renvall and Niemelä 1994; Niemelä et  al. 1995; Palviainen et  al. 2010; Olajuyigbe et  al. 2011; Crockatt and Bebber 2015; Shorohova and Kapitsa 2014, etc.), rates of deadwood decomposition vary widely. Shorohova and Kapitsa (2014) ascertained deadwood decomposition rates as a function of climatic factors, site conditions, tree species, stem position and mode of tree mortality in European boreal forests and estimated the maximal decomposition time of Picea abies at 230 years and its mean time at 150 years. Storozhenko (2001) considering deadwood decomposition in communities of different regions estimated the average time at 60–70  years and noted that the time shortens by 10–15  years in the south; fastest decomposition occurs in broad-leaved forests, while in the forest-steppe region it increases again by 10–15 years. According to our long-term studies (Spirin and Shirokov 2002), complete decomposition of spruce deadwood in tall herb dark coniferous  – broad-leaved forests in the Kilemarskiy Zakaznik occurs in 25–40 years. In the Kilemarskiy Zakaznik, the butt of standing old individuals of Picea abies was often afflicted by Heterobasidion parviporum Niemelӓ et Korhonen. On bases of trunks of old Picea abies and Abies sibirica individuals, the hygrophilous species of the xylotrophic macromycetes Postia guttulata (Peck) Julich and Vesiculomyces citrinus (Pers.) Hagstrӧm prevailed. Fruit bodies of mesophilous species developed on the upper part of trunks of Picea abies (Climacocystis borealis (Fr.) Kotl. et Pouzar, Onnia leporina (Fr.) H. Jahn and Porodaedalea chrysoloma (Fr.) Murill) and trunks of Abies sibirica (Phellinus hartigii (All. et Schnabl) Bondartsev and Hymenochaete cruenta (Pers.) Donk) (Spirin and Shirokov 2002) (Fig. 4.20). In the Kilemarskiy Zakaznik, trees often fall after the beginning of the humification of their trunks which leads to breaking of the trunks and treefall without uprooting. This happens more often on well-drained soils whereas trees fall with uprooting at sufficiently moist habitats. Probably, in the Kilemarskiy Zakaznik, areas that are currently more moist were less disturbed by man in the past; they are more heterogeneous and trees are less afflicted by root and stem rot. The following six stages of deadwood decomposition and overgrowing (Fig. 4.21) were described taking fallen logs of Picea abies in tall herb dark-coniferous  – broad-leaved forests in the Kilemarskiy Zakaznik as an example (Spirin and Shirokov 2002):

Fig. 4.20  Wood-decomposing basidiomycetes in the Kilemarskiy Zakaznik (Photo by V. Spirin)

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Fig. 4.21  Stages (0) to (5) of deadwood humification and the overgrowing of fallen logs of Picea abies in the Abieto-Piceeto-Tilieta boreo-nemoro-magnoherbosa in the Kilemarskiy Zakaznik (Photo by A. Shirokov)

(0) The initial stage of a recently fallen tree; this stage lasts up to 2 years. There are bark and branches on the trunk. The physical properties of the wood have not yet changed. There are no vascular plants on the fallen trunk (Picea abies seedlings may occur, but they quickly die). Fruit bodies of the pathogenic fungi Fomitopsis pinicola (Sw.: Fr.) P. Karst., Heterobasidion parviporum, Phellinus

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sulphurascens Pilát, etc. occur. One can find only the epiphytic mosses Orthodicranum montanum, Dicranum scoparium, Ptilidium pulcherrimum and species of the genera Eurhynchium and Plagiothecium which also grew in the butt zone before the treefall. (1) The stage of the beginning of the deadwood decomposition; this lasts from 2 to 10 years after treefall. The bark partly peels off; branches on which the trunk rests disintegrate. The mechanical properties of wood at the underside of the trunk change; it becomes more friable due to the pioneer xylotrophic fungus Phellinus ferrugineo-fuscus (P.  Karst.) Bourd. et Galz. Vascular plants are absent (seedlings can appear and die). The pathogenic fungi Fomitopsis ­pinicola, Heterobasidion parviporum, etc. continue to grow. Towards the end of this stage, pioneer fungi species, such as Amylocystis lapponica (Romell) Bondartsev et Singer and Fomitopsis rosea (Alb.et Schw.: Fr.) P. Karst, appear on the lateral surface of the trunk. Bryophytes, mainly the liverworts Lophocolea heterophylla and Brachythecium salebrosum, appear in bark cracks and forks of branches. Mosses cover 5–7% of the deadwood and up to 10% in sites with high moisture. (2) The stage of intense destruction of the deadwood; it lasts from 10 to 15 years after treefall. The bark is partially retained; the trunk lies completely on the ground. The wood looses its former mechanical properties: it becomes friable, easily stratified. Humification begins at the upper side of the log. Pioneer polypores species are replaced by the others: Fomitopsis pinicola is replaced by Pycnoporellus fulgens (Fr.) Donk., Skeletocutis odora (Sacc.) Ginns and Phlebia centrifuga P. Karst.; Heterobasidium parviporum by Junghuhnia collabens (Fr.) Ryv. and Dichostereum boreale Pouz. Bryophytes reach their maximum development: they cover 50–60% of the log; Pleurozium schreberi, Plagiomnium cuspidatum, Brachythecium salebrosum and Calliergonella cuspidate dominate; Sanionia uncinata, Brachythecium oedipodium, B. starkei, Campylium sommerfeltii, and Hylocomium splendens often occur. Vascular plants begin to develop: Picea abies seedlings cover up to 10% of the log; the small boreal herbs Oxalis acetosella, Viola selkirkii, etc. rarely occur. (3) The stage of complete destruction of the deadwood; it lasts from 15 to 20 years after treefall. The wood crumbles easily and colours reddish-brown. This stage has the highest diversity of life forms of xylotrophic macromycetes. Fungi with ephemeral fruit bodies and mildly destructive properties, such as Antrodiella citrinella Niemelӓ et Ryvarden, Physisporinus sanguinolentus (Alb. et Schw.: Fr.) Pil., Rigidoporus crocatus (Pat.) Ryv. and Asterodon ferruginosus Pat., dominate. The cover of mosses is greatly reduced due to competition with small boreal herbs. The same bryophytes as at the second stage dominate, but participation of epigenous species increases: Polytrichum commune, Rhodobryum roseum, Climacium dendroides, etc. settle on the log; Tetraphis pellucida and Plagiochila porelloides often occur; Plagiothecium cavifolium is found only at this stage of deadwood humification. Small boreal

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herbs cover 25–30% on the log: Oxalis acetosella dominates, Viola selkirkii and Gymnocarpium dryopteris occur sporadically. Juveniles of Dryopteris dilatata and D. carthusiana occur. Young individuals of Picea abies develop and cover 10–15% of the log; seedlings of Abies sibirica, Sorbus aucuparia and Ulmus glabra appear. (4) The stage of the end of humification; it occurs 20–25 years after treefall. The lower part of the decayed log is only slightly distinguishable from the humus horizon; only the top layer (10–15  cm thick) has the structure of litter. Xylotrophic macromycetes are absent. The moss cover continues to decline and covers 15–20% of the log. Plagiomnium cuspidatum, P. medium and Mnium stellare dominate; Plagiothecium laetum occurs on the lateral surface of the log; epiphytic species are completely absent. Immature individuals of Picea abies cover up to 25% of the log, but only some single individuals of these survive and become later virginal ones. Young individuals of Abies sibirica, Sorbus aucuparia and Ulmus glabra occur. Small boreal herbs are replaced by large ferns: Oxalis acetosella covers less than 10%, whereas Dryopteris dilatata and D. carthusiana cover from 10 to 15% of the log. Carex rhizina and Rubus idaeus occur. The herbaceous species cover up to 40% of the log. (5) The stage of a roll on the ground; it occurs 25–30 years after treefall. The composition of herbaceous species on the roll is the same as that around the (former) log. Large ferns, nemoral and boreal herbs cover up to 70% of the site where the log was lying. Nemoral species, such as Aegopodium podagraria, Dryopteris carthusiana, Pulmonaria obscura, etc., or the boreal ones Oxalis acetosella, Viola selkirkii and Gymnocarpium dryopteris dominate depending on light conditions. Mosses cover less than 3% of the roll; species of the genus Plagiomnium and Eurhynchium as well as Brachythecium plumosum occur. Cirriphyllum piliferum and species of the genus Fissidens were observed only at this stage. (6) The stage of smoothening the roll on the ground. These data on deadwood decay and humification were obtained from single treefalls of large Picea abies individuals which formed single gaps in the canopy of up to 200 m2 in surface area. In a case of larger gaps (up to 600 m2) in the Kilemarskiy Zakaznik, we observed an increase in soil moisture and therefore an increase in deadwood moisture and air humidity due to a decrease in water transpiration caused by trees. Increased moisture conditions led to the occurrence of more hygrophilous species of fungi, such as Rigidoporus crocatus, Perenniporia subacida (Peck) Donk and Steccherinum tenuispinum Spirin et  al., and vascular plants, such as Chrysosplenium alternifolium, Thelypteris phegopteris and Circaea alpina. In general, when 3 or 4 large trees simultaneously fell, moss coverage and its diversity increased on the fallen logs compared to a single treefall (Spirin and Shirokov 2002).

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Table 4.5  Duration of deadwood humification for different tree species in tall herb dark-­ coniferous – broad-leaved forests in the Kilemarskiy Zakaznik (According to Spirin and Shirokov 2002). Tree species Picea abies Abies sibirica Tilia cordata

Duration of deadwood humification in stages, years Initial stage First stage stages 2–6 2–3 5–8 5–6 2–5 8–10 5–6 1–2 5–8 5–6

Total, years 30–35 35–40 30–35

Long-term research in the Kilemaskiy Zakaznik allowed us to estimate the durations of different stages of deadwood humification for Picea abies, Abies sibirica and Tilia cordata (Table 4.5). In general, rates of deadwood decomposition depended on climatic conditions (high humidity and warm summers promote fast deadwood humification) and on specifics of the biotic community as well. Different types of fungi (including pathogens, xylotrophic species and species of the ground litter) and microorganisms must be present in the community to enable an active destruction and humification of deadwood. Anthropogenic impacts, especially periodic (even very rare) ground fires, can significantly suppress the fungal complex due to sterilization of the soil and bases of tree trunks. The process of deadwood decay and humification can be delayed for an indefinite time in that case.

4.3.5  Conclusion Just like the forests of the boreal region, the floristically richest uneven-aged hemiboreal forests are preserved in sparsely populated areas which are least accessible for economic development. However, because of the greater development of the region compared with the boreal one, hemiboreal forests without logging and fires for more than 300 years so far have not been found. This determines the uncertainty in constructing a theory of successional development of these forests at the final stages of recovery. According to the indications for a late-successional forest which we considered above (in Sect. 2.5), the most important features of hemiboreal forests developing over a long period of time (more than double the lifetime of late-successional trees) without human and catastrophic disturbances, are the following: (i) it has the highest species and structural diversity of all forest layers; (ii) it has a complex, patchy organization of the forest canopy (caused by tree falls) with different combinations of coniferous, small-leaved and broad-leaved trees in the patches, and (iii) it contains microsites caused by treefalls with uprooting at different stages of their decay and overgrowing. These signs, to varying degrees, are present in the tall herb dark-­ coniferous  – broad-leaved forests that we have discussed in this section. More disturbed and wider distributed hemiboreal forests are discussed in the next two sections.

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4.4  P  ost Fire and Post Cutting Successions in the East of the Kostroma Region 4.4.1  General Description of the Study Area The Kostroma region belongs to the Upper Volga River geographical region; it is a hilly plain dissected by numerous river valleys (Milkov 1953; Masalev 1973). The climate is temperate continental with a strong seasonal cycle. The summers are relatively warm and winters have moderate to severe frosts and a moderate snow cover. The average annual temperature is 1.9°C.  The vegetation period is about 160  days; the average January temperature is −12°C; the average July ­temperature  +18°С. The average annual precipitation is 730  mm (Agafonova 1964, 1968). Dark-coniferous and mixed forests occupy the eastern part of the Kostroma region; there forest ecosystems at their early, middle, and late successional stages after logging and fires occur and have been investigated. The study areas included (1) the State Nature Reserve “Kologrivskiy Les”, and the following forestry units: (2) Mezhevskoy, (3) Pavinskiy, (4) Vokhomskiy, (5) Sharyinskiy, (6) Manturovskiy and (7) Molomskiy (numbers 17–21  in Fig. 2.1) (the last-named study area is located in the Kirov region close to the border with the Kostroma region and close to number 20 in Fig. 2.1). The geographical coordinates of the study areas range from 58.1 to 59.4°N and from 43.8 to 47.3°E. The more northern study areas (1, 2, 3, northern part of 4 and 7) are located in the south-west of the Severnye Uvaly Upland, on an undulating moraine plain (200– 225 m asl) mainly formed by loams and sandy loams with inclusions of boulders and rubble of crystalline rocks and covered by medium loams. The more southern study areas (southern part of 4, 5 and 6) are located in lower relief positions within the undulating fluvio-glacial plain mainly formed by medium and fine sands with rare inclusions of crystalline rocks, at elevations from 170 to 200 m asl (Gvozdetsky and Zhuchkova 1963; Isachenko 1991). Analysis of the archival documents of the middle of the eighteenth century (Rossiyskiy gosudarstvennyi arkhiv drevnikh aktov [Russian State Archive of Ancient Acts] funds 1354, 1355 and 1356) and the historical literature of later times (Krzhivoblotsky 1861; Dyubyuk 1912; Matreninsky 1917, etc.) showed that forests in the east of the Kostroma region were not intensively cut till the twentieth century as this part of the region has always been sparsely populated and there were ­state-­owned forests where logging was severely restricted and could be carried out only by state authorities (Dudin 2000; Lugovaya 2008). Despite the fact that timber forests were strongly affected by fires and storms (Krzhivoblotsky 1861), in the beginning of the twentieth century about 80% of the area was occupied by darkconiferous forests (Dyubyuk 1912); 70% of the forests were exploited by selective logging with the interval between felling rounds lasting from 130 to 160 and even up to 180 years (Dyubyuk 1920). Such a gentle cutting mode with a long interval preserved the structure and composition of the forests. At that time, for example, in

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the area of the Kologrivsky district, old-growth forests dominated by Picea abies with Abies sibirica and Tilia cordata in the overstorey were common; Tilia cordata, Acer platanoides and Ulmus glabra occurred in the second layer of the canopy. Stands with Larix sibirica and Quercus robur also occurred (Materialy… 1908). Massive clear cuttings started in the region in 1950s (Dudin 2000). Nowadays secondary forest communities formed after logging, fires, and rarely also forest plantations (mainly of Picea abies) occupy most of the region. Pyrogenic forests dominated by Pinus sylvestris are common in the south-east where, on sandy soils, slash-andburn agriculture was widely spread. In remote areas in the extreme north-east of the region discrete forest tracts (of up to 100 hectares) of old-growth (elder than 200 years old) dark-coniferous and dark-coniferous – broad-leaved forests can be found which are obviously the remains of those old state forests (Sokolov 1986; Korennye temnohvoynye lesa… 1988). It is important to point out that the northern limits of the distribution areas of Quercus robur, Acer platanoides and Fraxinus excelsior and the western limits of the distribution areas of Larix sibirica and Abies sibirica pass through the study region (Sokolov et al. 1977). At that, changes in distribution areas of tree species within the region have been documented for the last centuries. In the nineteenth and the beginning of twentieth century Abies sibirica made up to 40% of the stands in the east of the Kostroma region; it was common in Picea abies and mixed forests (Kvetsinsky 1917), but felling and fires later decreased the distribution area of Abies sibirica (Zhadovsky 1920; Lugovaya 2008). In the nineteenth and the beginning of the twentieth century the northern limit of Quercus robur’s distribution passed through the Kologriv district, though in the eighteenth century there were large tracts of oak forests for ship timber throughout the region (Charnetsky 1899, 1914). But at the beginning of the twentieth century Quercus robur was almost totally eradicated due to cutting and ploughing of the fertile soil on which the oak forests grew (Lugovaya 2008). Now Quercus robur occurs sporadically only in floodplains (Dudin 2000; Lugovaya 2008). Forests dominated by Tilia cordata were also widespread over the entire Kostroma region (Arnold 1891), but the area covered by these forests was gradually reduced due to fires and the increase in population density and the wide use of Tilia cordata for different things in everyday life (Matreninsky 1917). Here, as elsewhere throughout the European part of Russia, local people made bast from the bark and branches, wove mats and ropes from the bast, made marine tacklers, bast shoes and other small things that were widely used. As young individuals of Tilia cordata could be used for those needs, many young trees before their reproductive stage were cut and thereby lime populations have been significantly undermined by the lack of seed trees. As a result, at the beginning of the twentieth century Tilia cordata was preserved only in the forests farthest away from settlements, where it occurred in the understorey as well as in the second layer of the overstorey (Charnetsky 1899; Kvetsinsky 1917). The broad-leaved trees Acer platanoides, Ulmus glabra and Fraxinus excelsior were also common in the region (Materialy… 1908; Matreninsky 1917) but presently these species became extremely

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rare owing to fires and ploughing. Nowadays, forests dominated by Picea abies and P. abies with Abies sibirica and participation of Tilia cordata in the overstorey and with an undergrowth of T. cordata, Acer platanoides and Ulmus glabra can be found only in small areas spread between large post-fire and post-cutting tracts.

4.4.2  Succession Series We studied the succession series of forest recovery after fire on sandy soils, and also after cutting and fire as well as after selective cutting on loam and sandy loam soils (Lugovaya 2008). The succession stages were distinguished according to stand development which comprised an assessment of the proportion of pioneer and late-­successional tree species and the development of their populations. The same five stages were defined for each of the three successional series as follows: At the first stage immature and virginal individuals of pioneer (early-­successional) trees form the vegetation (but after selective logging the structure of the vegetation is more complicated). At the second stage virginal and young reproductive individuals of early-successional trees form the canopy; late-successional trees appear in the understorey. At the third stage, reproductive individuals of early-successional trees compose the stand; some of these trees begin to die off but remain as standing dead stems (snags), others fall (with and without uprooting); a pit-and-mound topography begins to form; an undergrowth of late-successional trees is developing. At the fourth stage late-successional trees often dominate in the overstorey; early-­ successional trees also occur; the next generation of late-successional trees is developing in the understorey. At last, at the fifth stage, individuals from the first and following generations of late-successional trees fall, forming a gap-mosaic in the canopy and a pit-and-mound topography at the ground surface; as a result an uneven-aged dark-coniferous – broad-leaved forest with a complicated vertical and horizontal structure of vegetation is formed. Forest communities at each stage for each successional series were distinguished in the study region. The vegetation was sampled in 2003 and 2004 at 320 plots of 10 × 10 m, and in 5–95 plots per stage per series. Only forests on sites with a good or moderate drainage were included into the research. Series 1 unites forest communities developed after fire and dominated by Pinus sylvestris (and Picea abies at the later stages) on sandy and sandy loam deposits. Communities attributed to the series were found in study areas number 1, 2, 6, and in the south of study area 4. Podzols and Albeluvisols were common soils. Traces of fire occurred in all communities: there were charred snags and deadwood; fire scars on Pinus sylvestris individuals; layers of charcoal or accumulations of large charcoal pieces at the border of the litter and mineral soil horizon, and charcoal in old pits formed after treefalls.

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Fig. 4.22  Succession series 1 of forest recovery after fire on sandy soils in the Kostroma region: (a) the 1st stage with regeneration of Pinus sylvestris on the bare substrate and (b) the 3rd stage with Pinus sylvestris of 40–70 years old in the overstorey (Photos by D. Lugovaya)

At the initial stage of series 1 (1.1) Pinus sylvestris regenerated on the bare substrate (Fig.  4.22a); immature and virginal individuals of Betula pubescens and Populus tremula also occurred. All trees were not more than 20 years old. Lichens, sometimes with gramineous plants, dominated in the ground layer that defined the forest type as Pineta sylvestris cladinosa (here and below according to the Prodromus of the hemiboreal forests, Sect. 4.1). Species of the piny, meadow and boreal ecological-coenotic groups occurred in the field layer (Fig. 4.23). The number of vascular species per plot (species density) averaged 12.9. At the second stage (1.2) young individuals (from 20 to 40 years old) of Pinus sylvestris, sometimes with Betula pubescens and Populus tremula, formed a low forest canopy; immature individuals of Picea abies dominated in the understorey. Green mosses with lichens co-dominated in the ground layer and the forest community belonged to the Pineta sylvestris hylocomioso-cladinosa. The dwarf shrubs Vaccinium vitis-idaea and V. myrtillus also occurred in the field layer. The number of boreal species increased, but grasses disappeared, which led to a decrease in species density in the field layer to 10.0 (Fig. 4.23). At the third stage (1.3) Pinus sylvestris of 40–70  years old dominated in the overstorey (Fig.  4.22b). Picea abies formed the understorey and sometimes it occurred in the second sublayer of the canopy. Some Pinus sylvestris individuals had fallen, some of them with uprooting that caused the forming of the microsites of pits, mounds and fallen trees. Species density in the field layer increased slightly (to 11.0 species per 100 m2) because of the increase in boreal species. Vaccinium vitis-idaea and V. myrtillus were common; green mosses dominated in the bottom layer and the community belonged to the forest type Pineta sylvestris fruticuloso-hylocomiosa. At the fourth stage (1.4) the forest type, species density and ecological-coenotic structure of the field layer were the same as at the previous stage. However, virginal

Average number of species per 100 m2

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40.0 35.0 30.0

Olg Wt Md Nt Nm Br Pn

25.0 20.0 15.0 10.0 5.0 0.0

1.1

1.2

1.3

1.4 1.5 2.1 2.2 2.3 2.4 2.5 3.1 3.2 Successional stages 1-5 in the series 1-3

3.3

3.4

3.5

Fig. 4.23  Ecological-coenotic structure of the field layer in forests at different successional stages after fire and felling in the east of the Kostroma region. The successional stages 1–5 of the successional series 1–3 are arranged along the horizontal axis. Ecological-coenotic groups: Pn piny, Br boreal, Nm nemoral, Nt nitrophilous, Md meadow-edge, Wt water-marsh, and Olg oligotrophic groups

and young reproductive individuals of Picea abies formed the second sublayer of the canopy and co-dominated with Pinus sylvestris in the overstorey; Pinus sylvestris was from 70 to 100 years old. At the fifth stage of the post-fire series (1.5) Piceeta parviherboso-hylocomiosa had developed. These communities were found in the Manturovsky and Mezhevskoy forestry units and in the Kologrivskiy Les Reserve (study areas 6, 2 and 1) usually occupying small areas within large forest massifs formed after numerous fires. Cover of the overstorey varied from 40 to 90%; Picea abies with an age of about 100 years dominated; single individuals of Pinus sylvestris occurred and reached up to 150–170 years in age. Larix sibirica, of which the age of the oldest individuals was 230 years old, was also found in the overstorey and understorey in study area 2. Cover of the understorey was 10–20%; Picea abies dominated; Sorbus aucuparia was common; Lonicera xylosteum, Juniperus communis and Rosa spp. rarely occurred. Cover of the ground layer varied from 5 to 80%. The dwarf shrubs Vaccinium myrtillus and V. vitis-idaea co-dominated with small boreal herbs, such as Oxalis acetosella, Maianthemum bifolium, Linnaea borealis, Trientalis europaea, etc.; Calamagrostis arundinacea occurred sometimes with high abundance; the meadow species Fragaria vesca and Vicia sepium and the nemoral herbs Stellaria holostea and Melica nutans occurred here and there. In the Reserve Dryopteris carthusiana, D. dilatata, Gymnocarpium dryopteris and Equisetum sylvaticum often occurred with low abundance values. Cover of the bottom layer was high (up to 95%); the green mosses Pleurozium schreberi and Dicranum majus dominated; D. undulatum, Hylocomium splendens, Climacium dendroides, etc.

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occurred; lichens of the genus Cladonia also occurred. Species density in the field layer was the lowest (Fig. 4.23) probably due to the absence of large gaps in the canopy that might have improved light conditions in the field layer as well as the absence of a well-developed microsite structure that is created by tree fall with uprooting. We did not find forests developed after fire with clear signs of ancient fires but with Picea abies individuals older than 100 years old or with fallen adult trees of Picea abies. That means that we only could describe forests that were at their initial phase of the final stage of the post-fire series in the study region. Later phases were described in the framework of the two other successional series. Series 2 and 3 unite forests developed after logging. As said above, massive clear cuttings started in the region only in 1950s and 1960s. At that time heavy equipment came to be used in forestry and clear-cut in summer with severe damage to the ­vegetation in the understorey became widespread in the region. Before the middle of the twentieth century cuttings on watersheds and in floodplains of small rivers took place usually in winter: timber was taken out of the forest by horses and sleds (Fig. 3.4), because the load capacity and pass ability of snow sleds was much higher than that of carts (Bobrovsky 2002). The ground layer vegetation and the small undergrowth were not disturbed under the snow cover during such felling and removing activities and the forest ecosystem could relatively quickly recover even after large-­ scale winter cuttings. However repeated fires in addition to felling did significantly change the composition, structure and functioning of the forest ecosystems (Bobrovsky 2010). First of all, tree species that are more fire-sensitive (Abies sibirica and broad-leaved trees in the study region) got eliminated from the forests. Accordingly, presence or absence of Abies sibirica and Tilia cordata (which is the most common among all broad-leaved trees in the region) can be considered a sign of absence or presence of severe damage to the forest ecosystems in the past. Therefore we distinguished successional series after cuttings into those which were accompanied by fire and led to severe damage of forest vegetation and those without fire and where the undergrowth was left and only mild damage to the ground layer of the vegetation was recorded. Series 2 unites forests developed after complex impacts of cuttings and fires and dominated by Betula pubescens, Populus tremula and Picea abies at their later stages. They are mainly located on loam and sandy loam deposits. Usually traces of fire were found in the soil as charcoal occurred under the litter. Abies sibirica and Tilia cordata were absent in these forests. On the whole, the forest communities attributed to this series are the most widespread in the region; they were found in all study areas, except area 6 and the south of area 4. These forests were mainly located on flat watersheds and gentle slopes, but they were also described from floodplains of small rivers on sandy loam and silty sands (from shortly inundated old parts of floodplains, see Chap. 6). At the two initial stages Betuleta (Populeta) fruticuloso-hylocomiosa developed after clear-cut. At the first stage (2.1) immature and virginal individuals of Betula pubescens and Populus tremula formed the young tree layer (Fig. 4.24a). Sometimes young individuals of Pinus sylvestris which could be self-sowed or planted after

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Fig. 4.24  Succession series 2 of forest recovery after complex impacts of cuttings and fires on loam and sandy loam soils in the Kostroma region: (a) the 1st stage with immature and virginal individuals of Populus tremula and Betula pubescens; (b) the 3rd stage with Betula pubescens and Populus tremula of 40–70 years in the overstorey and Picea abies in the second layer of the canopy; (c) the 4th stage with Picea abies in the overstorey and (d) Piceeta parviboreoherbosa at the 5th successional stage (Photos by D. Lugovaya)

felling without follow-up care also occurred. Dwarf shrubs, Calamagrostis epigeios and green mosses dominated in the ground layer, whereas species from different ecological-coenotic groups also constantly occurred in the field layer (Fig. 4.23) on sites with various ecological properties which are usually formed after clear-cut. Species density in the field layer was highest among the communities of this series; it averaged 29.2 species per 100 m2. At the second stage (2.2) young individuals (from 20 to 40 years old) of Betula pubescens and Populus tremula, sometimes with rare Pinus sylvestris, formed a low forest canopy. Immature and virginal individuals of Picea abies (partly depressed) dominated in the understorey. Species density in the field layer decreased slightly because of a decrease in the number of water-marsh and meadow-edge species (Fig. 4.23), whereas the number of oligotrophic and nitrophilous species increased. At the third stage (2.3) Betula pubescens and Populus tremula of 40–70 years old formed the overstorey; Picea abies dominated in the second layer of the canopy and in the understorey where Pinus sylvestris also did occur (Fig. 4.24b). Single gaps in

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the canopy and pit-and-mound topography formed by falls of Betula pubescens or Populus tremula were observed. Cover of green mosses decreased, and dwarf shrubs and small boreal herbs dominated in the ground layer; the community belonged to the forest type Betuleta (Populeta) parviherboso-hylocomiosa. Water-marsh and oligotrophic species disappeared and the species density in the field layer decreased and averaged 23.2 species per 100 m2 (Fig. 4.23). At the fourth stage (2.4), from 70 to 150 years after cutting, Picea abies dominated in the overstorey; Betula pubescens, Populus tremula, and sometimes Pinus syvestris occurred (Fig.  4.24c). The community belonged to the Piceeta parviherboso-­hylocomiosa forest type: boreal herbaceous species and green mosses dominated in the ground layer. The crown cover formed by reproductive individuals of Picea abies increased and that reduced the species density in the field layer; it averaged 22.0 species per 100 m2. Forests at the fifth stage of the post clear-cut series (2.5) were mainly described from sites inconvenient for felling and located within or on the edges of the felling areas. The forest communities belonged to the Piceeta parviboreoherbosa or Piceeta boreo-nemoroherbosa forest types depending on the proportion of nemoral species in the understorey (Fig. 4.24d). These forests were found on relatively rich soils, Albeluvisols and Luvisols. In forests located in floodplains Fluvisols dominated on light loam and silty sands; Podzols dominated on fluvioglacial sands on the first terraces above the floodplains. Picea abies older than 150 years dominated in the overstorey; Betula pubescens and Populus tremula always occurred; Abies sibirica sporadically occurred, mostly in the Reserve study area. Crown cover varied from 40 to 80%. Large gaps in the canopy (up to 150 m2) and deadwood at different stages of decay were registered in some communities. Cover of the understorey was 8–20% (up to 70% in the Reserve). An undergrowth of Picea abies dominated; Populus tremula often occurred; Abies sibirica and Alnus incana rarely occurred. Sorbus aucuparia was common; Daphne mezereum, Lonicera xylosteum, Frangula alnus and Padus avium often occurred. Cover of the field layer was 60–80%. Small boreal herbs, most often Oxalis acetosella, dominated in the ground layer; nemoral herbs and ferns, such as Aegopodium podagraria, Stellaria holostea, Dryopteris carthusiana, often occur. Oligotrophic species, such as Carex globularis and Viola epipsila, occurred in depressions. The hygrophilous tall-herbs Filipendula ulmaria, Geum rivale, etc. often occurred in forests located in floodplains. The cover of green mosses varied significantly from 20 to 90%. On some patches, a dense undergrowth of Picea abies occurred in large gaps caused by treefalls. The diversity in the field layer decreased there; but the tall herbaceous species Rubus idaeus, Athyrium felix-femina, Aconitum septentrionale, Calamagrostis arundinacea, etc. were recorded from such patches instead of young individuals of Picea abies. Mean number of species per 100 m2 in the field layer of these communities was 24.2 (Fig. 4.23). Series 3 unites forests developed after selective logging or cutting at which the undergrowth remains and only mild damage to the ground layer of the vegetation occurred. Forests of this series were mainly located on loam and sandy loam deposits. They were dominated by Picea abies, Betula pubescens and Populus tremula

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with participation of Abies sibirica and broad-leaved trees in the overstorey and understorey. Among the broad-leaved trees Tilia cordata was most common, Acer platanoides and Ulmus glabra rarely occurred. The forests were found in the study areas 1, 2, 4, 6 and 7 on diverse relief positions: tops and slopes of flat moraine hills, gentle slopes of valleys and floodplains of small rivers. On the whole, these communities were rare in the study region due to widespread fires and heavy clear-cuts. Communities at the first three stages of this series belonged to the Populeta (Betuleta) boreo-nemoroherbosa forest type. Differences in vegetation between these stages mainly consisted of differences in the structure of their tree populations. At the first stage (3.1), that lasts to 20 years after cutting, immature and virginal individuals of Betula pubescens and Populus tremula developed between single adult individuals of Tilia cordata and Abies sibirica and groups of young individuals of Picea abies. In the field layer boreal and nemoral species co-dominated and species of all other ecological-coenotic groups also occurred owing to the presence of sites with diverse ecological conditions after cutting (Fig. 4.23). At the second stage (3.2) young individuals of Betula pubescens and Populus tremula of 20–40 years old dominated in the overstorey, where reproductive individuals of Tilia cordata and Abies sibirica occurred. Some mature individuals of Abies sibirica fell, forming gaps in the canopy. An undergrowth of Picea abies, Abies sibirica and Tilia cordata dominated in the dense understorey; the two latter species occurred in the elfin form. In the field layer the number of meadow species increased whereas water-marsh and oligotrophic species disappeared and the number of nitrophilous species decreased (Fig. 4.23) owing to moisture reduction connected with the increase in water transpiration by actively developing trees. At the third stage (3.3) reproductive individuals of Betula pubescens and Populus tremula (of 40–70 years old) dominated in the upper layer of the overstorey; young generations of Picea abies, Abies sibirica and Tilia cordata dominated in the second layer of the overstorey and in the understorey, where Sorbus aucuparia was common; Padus avium rarely occurred; Salix caprea and Alnus incana could be found. A patchy organization of the forest canopy was forming owing to treefalls. Cover of the field layer was 50–90%. Boreal and nemoral species co-dominated and species density was the highest among the communities studied (Fig. 4.23). Oxalis acetosella and Calamagrostis arundinacea often predominated; the boreal species Maianthemum bifolium, Rubus saxatilis, Solidago virgaurea, Luzula pilosa, Trientalis europaea and Equisetum sylvaticum were common. The nemoral herbs Aegopodium podagraria, Stellaria holostea, Melica nutans, Milium effusum, etc. often occurred. The dwarf shrubs Vaccinium vitis-idaea and V. myrtillus sometimes occurred with high abundance. The large ferns Dryopteris carthusiana and Athyrium filix-femina were found in gaps. The cover of mosses was low: from 5 to 30%. At the fourth stage (3.4) a Tilieto-Abieto-Piceeta boreo-nemoroherbosa with tree individuals from 70 to 150 years old had developed (Fig. 4.25). Picea abies, Abies sibirica and Tilia cordata co-dominated in different proportions in the overstorey; Betula pubescens and Populus tremula occurred. Two sublayers in the can-

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Fig. 4.25  Tilieto-Piceeta boreo-nemoroherbosa at the 4th stage of forest recovery after selective cuttings on loam and sandy loam soils in the Kostroma region (The left photo was taken by N. Ivanova and the right photo by D. Lugovaya)

opy, one with a height of more than 20 m and one of about 15 m, with Tilia cordata in both of them, could often be distinguished (Fig. 4.25 right). Gaps in the canopy and deadwood at different decay stages occurred. The undergrowth of Picea abies, Abies sibirica and Tilia cordata was well developed. An undergrowth of Acer platanoides and Ulmus glabra rarely occurred. Frangula alnus, Lonicera xylosteum, Padus avium and Sorbus aucuparia often occurred in the understorey. Cover of the field layer was high (80–90%). Oxalis acetosella co-dominated with the nemoral herbs Aegopodium podagraria, Pulmonaria obscura, Mercurialis perennis and Asarum europaeum. The large ferns Dryopteris carthusiana, D. dilatata and Athyrium filix-femina rarely occurred in the gaps, with high abundance. Calamagrostis arundinacea and Vaccinium myrtillus sometimes dominated and Filipendula ulmaria could be found on moistened sites. Cover of green mosses was low (not more than 20%). Albeluvisols and Luvisols were common. At the fifth stage (3.5) dark coniferous  – broad-leaved forests dominated by boreal and nemoral tall herbs in the ground layer (Tilieto-Abieto-Piceeta boreo-­ nemoro-­magnoherbosa) had developed. These forests were characterized by large gaps in the canopy caused by falls of late-successional trees and by tall herbs and ferns developing in the gaps. These communities were very rare in the region; they were found only in floodplains of small rivers; Fluvisols with a well-developed molic horizon (more than 20 cm) were common. The similarity in composition and structure of these forests with those described from watersheds (see Sect. 4.3) allows us to assume that the reason of their confined distribution most probably is an anthropogenic one. There was not any trace of fire, cutting and other exogenous impacts in these forests whereas such traces were clearly visible in communities on watersheds. Picea abies with Abies sibirica and Tilia cordata co-dominated in the overstorey; Betula pubescens also occurred. The site productivity quality was high (site classes 1 and 2). Crown cover varied from 30 to 80% owing to the complex patchy organization of the forest canopy. An undergrowth of Picea abies, Abies sibirica, Tilia cordata and Betula pubescens dominated; Alnus incana and Populus tremula

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often occurred; Ulmus glabra and Acer platanoides occurred sporadically. Sorbus aucuparia and Padus avium often occurred in the understorey where a high diversity of boreal, nemoral and nitrophilous shrubs, such as Lonicera pallasii, L. xylosteum, Daphne mezereum, Viburnum opulus, Ribes nigrum, R. hispidulum, Rosa majalis, etc. was registered. Cover of the field layer was high (70–80%). The nemoral herbs Aegopodium podagraria, Lathyrus vernus, Pulmonaria obscura, Paris quadrifolia, etc. and the small boreal herbs and ferns Gymnocarpium dryopteris, Phegopteris connectilis, Solidago virgaurea, Oxalis acetosella, and Maianthemum bifolium co-dominated together with the tall herbs and ferns Aconitum septentrionale, Athyrium filix-femina, Dryopteris carthusiana, Matteuccia struthiopteris, Crepis paludosa, Anthriscus sylvestris, Angelica sylvestris, Cacalia hastata, Cirsium heterophyllum, Milium effusum and Valeriana officinalis which occurred in the gaps. The hydrophilous species Filipendula ulmaria, Geum rivale and Viola epipsila often occurred in the lower, moist areas. The occurrence of the Siberian species Cacalia hastata, Atragene sibirica, Crepis sibirica and others was an additional feature of these communities. Cover of the bottom layer was low (up to 40%). The communities of series 3 were richest in species number compared with all other communities described here. The species density in the field layer at different successional stages varied from 29.0 to 36.0 species per 100 m2 and this provides further evidence of the careful mode of selective logging and cutting leaving the undergrowth and ground vegetation without severe disturbances.

4.4.3  Conclusion Fires and logging are the main external impacts affecting the forest vegetation in the east of the Kostroma region. Pinus sylvestris forests occupy large areas after repeated fires, particularly on sandy soils. Soil fertility usually decreases after fires (Bobrovsky 2010). A low soil fertility, together with the often large-scale disturbances hamper the seed flow from the undisturbed forests and result in a small number of vascular plant species in the post-fire communities. The composition and structure of the vegetation of the post-fire series depend on the combined effects of fires, environmental parameters, distances from seed sources and mosaics of gaps in the canopy and microsites caused by treefalls. Logging accompanied by fires leads to the loss of Abies sibirica and broad-­ leaved trees, such as Tilia cordata, Ulmus glabra and Acer platanoides, and a decrease in the number of nemoral species in the ground layer compared with forests after logging without fires. Forests dominated by the deciduous small-leaved trees Betula pubescens and Populus tremula in the overstorey and dwarf shrubs, small boreal herbs and green mosses with participation of nemoral herbs in the ground layer, occupy vast areas in the region after the clear-cuttings of the last 50 years (with the use of heavy equipment) and earlier logging that was accompanied by fires. Such impacts over large areas (one clear-cut area reached up to 100 ha

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in the region) slowed down the recovery of the vegetation due to the large distance from seed sources and the severe disturbances to vegetation and soil. Under a prolonged absence of fires, the recovery of tree populations and of the diversity of vascular plants go more quickly. In areas with obvious traces of fire in the soil (where fires in the past were frequent and intense) the number and proportion of nemoral herbs and ferns are less and mosses cover the greater part of the ground compared to areas with faint traces of fire. Selective logging without heavy equipment preserves the undergrowth and provides conditions for the rapid regrowth of shade-tolerant, dark-coniferous and broad-leaved trees (Yaroshenko 1999; Yaroshenko et al. 2001). Successional recovery in such forests is much faster; there Picea abies, Abies sibirica and Tilia cordata participate in the understorey and in the overstorey. Tall herb boreal-nemoral dark-­ coniferous  – broad-leaved forests (Tilieto-Abieto-Piceeta magnoherbosa) can develop during the lifespan of two first generations of late-successional trees provided that there is a stable seed influx from regional plants. Such forests are mainly described from floodplains of small rivers and from sites close to floodplains, because floodplains restrain fires and maintain seed sources for the resettlement of species (Kurnaev 1968; Mirin 2003; Zaugolnova et al. 2009). Selective logging is partly similar to natural treefall, and was observed to begin at the third stage of the described successional series when early-successional trees begin to fall and form gaps in the canopy. Improved light conditions then leads to undergrowth development and to the establishment of light-demanding trees and herbaceous species from the meadow-edge, water-marsh and boreal tall herb ecological-­coenotic groups (Braslavskaya and Tikhonova 2006). Provided that seed flow of regional species (primarily seeds of Abies sibirica, Tilia cordata and nemoral and boreal tall herbs) is available, communities at the last stages of the 1st and 2nd series can successionally developed into communities at the last stage of the 3rd series, i.e. to the floristically rich Tilieto-Abieto-Piceeta boreo-nemoroherbosa and T.-A.-P. boreo-nemoro-magnoherbosa. These forests were described from small patches in almost all study areas; that indicates the potential of a widespread development of these communities on different soils in different relief position provided that a proper seed flow of all regional species is available. It was shown that the successional recovery of forests after fires and logging develops in a similar way: the number and proportion of nemoral and tall herbaceous species increases and the communities are enriched by species of other ecological-­coenotic groups. The recovery of the species diversity was more rapidly realized on loams and sandy loams and also in floodplains and areas adjacent to them than in the other areas. At the initial stages of the recovery, soils and relief position are important factors, but they do not prevent the development of boreal-­ nemoral herb dark-coniferous  – broad-leaved forests. Main factors hindering ­indefinitely the successional recovery of the communities are their remoteness from seed sources and the high extent of transformation of the territory by preceding anthropogenic impacts including fires.

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4.5  P  lant Diversity and Successional Stages of Forests After Cutting and Ploughing in the Southern Moscow Region The State Nature and History Reserve “Gorki” is located 10 km south of Moscow on slightly hilly to flat terrain (140–180 m asl) between the Pakhra and Moscow rivers (number 16 in Fig. 2.1) on the moraine-erosion plain formed by loams on clays and limestones (Rysin 1985; Nizovtsev 1995). Luvisols dominate in the region. The average annual temperature is 3.5°C; the average annual precipitation is 700 mm (Shekhtman 1964, 1967). The geographical coordinates of the Reserve are 55.3°N and 37.5°E; its total area measures 24 km2. We have investigated three island forest tracts surrounded by agricultural lands and settlements (Fig. 4.26). They belong to the following forestry units within the Reserve: Syanovskiy (609 ha), Korobovskiy (662 ha) and Bogdanovskiy (856 ha) (Korotkov 1992, 1999, 2000). It is believed that the area of the Reserve has been affected by man since the 1st millenium BC (Krenke 1995). The composition and structure of these forests are typical for the center of European Russia and, as a result of centuries of economic development, they are simplified compared with the late-successional hemiboreal forests: the studied forests mainly consist of even-­ aged stands which are floristically poor and there is neither a patchy organization of the forest canopy nor a complex microsite structure in the ground layer. Identical soil types and relief positions in the Reserve carry different forest types that differ in their management histories. These histories have been recorded since the end of

Fig. 4.26  Satellite image of part of the Gorki Nature and History Reserve in 2003. 1 Korobovskiy, 2 Syanovskiy and 3 Bogdanovskiy forestry units. These island forest tracts are surrounded by agricultural lands and settlements

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the eighteenth century and that allowed us to study the influence of different variants of land-use and forestry on plant diversity and successional dynamics of the forest ecosystems. A forest inventory GIS (on data of 1991; at a scale of 1:10,000) was developed (Korotkov et al. 2000) to assess the presence of tree species in the overstorey and understorey of the forest tracts. To detailedly assess the tree species populations, 31 permanent plots ranging in size from 2500 to 10,000 m2 and 79 temporary square plots of 400 m2 have been established in the period 1988 to 1993. Within the plots, species name and ontogenetic stage were recorded for all tree and shrub individuals; 215 phytosociological relevés were also sampled in square plots of 100  m2. Tsyganov’s ecological Tables (1983) for plant species were used to assess soil parameters (moisture, fertility and reaction) and light availability in the vegetation plots; vascular plant diversity was assessed according to the methods described in Sect. 2.5.

4.5.1  Land-use History of the Region Settlement of present-day southern Moscow suburbs began in the early Iron Age. In the fifth century BC, the valleys of the Pakhra River and its tributaries were well cultivated as evidenced by numerous settlements of the Dyakovian culture (Krenke 1995). Those were permanent settlements surrounded by lands used for various purposes (including arable lands) (Gonyanyi and Krenke 1988; Krenke 1995). Active economic development of the area has been continued by the Slavs since the ninth and tenth centuries. Their burial mounds of the eleventh to thirteenth centuries are frequent in the Reserve area. The Old Russian population was engaged in agriculture, animal husbandry, hunting, fishing, apiculture and handicrafts (Nizovtsev et al. 1995). Slash-and-burn agriculture was wide spread in the region till the fourteenth and fifteenth centuries (Pushkova 1968; Nizovtsev et al. 1995) and almost all watershed areas passed through the stage of agricultural use, perhaps more than once (Rysin 1985). In the fifteenth and sixteenth centuries, the forested area in the Moscow region became strongly reduced due to an increasing population and the transfer into the three-field farming system (Rozhkov 1899), whereas at the end of the sixteenth to the beginning of the seventeenth centuries a significant part of the arable lands became overgrown by forests owing to the economic crisis (Nizovtsev et al. 1995). Thereafter agricultural lands again encroached upon the forests: in the second half of the eighteenth century forests covered about 20% of the land in the Nikitskiy uezd (the province where the present-day Gorki Reserve is located), arable lands occupied 64% and hayfields 11% of the total province area of 1519.3 km2 (Rossiyskiy gosudarstvennyi arkhiv drevnikh aktov [Russian State Archive of Ancient Acts] fund 1355, file 1, unit 778). The forests of the province were mainly coppice stands dominated by Betula spp., Populus tremula, Quercus robur and Tilia cordata; timber stands dominated by Pinus sylvestris and Picea abies rarely occurred. In the nineteenth century after the Patriotic War of 1812, the proportion of

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Fig. 4.27  Changes in forested areas in the present-day Gorki Reserve during the eighteenth to twentieth centuries. Contours of forest tracts were plotted according to the following sources: 1784 Russian State Archive of Ancient Acts, fund 1356, file 1, unit 2366; 1852 Central State Military and Historical Archive, fund VUA, unit 21,380; 1992 forest inventory data. 1–3 are the following forestry units: 1 Korobovskiy and Kazanskiy, 2 Syanovskiy and 3 Bogdanovskiy. 4 the Pakhra River

forested land increased in the region, as can be concluded from military topographic maps (Fig. 4.27). In the period 1920–1945, the forests in the area were mainly clear-cut. Stands which had not attained the age of maturity dominated in the area after the Second World War. Forest grazing was forbidden in forests close to Moscow at the turn of 1950s to 1960s and that led to mass regrowth of deciduous trees and shrubs in the understorey (Kurnaev 1980; Korotkov 1992). Only sanitary felling and thinning were carried out in the Reserve from 1974 to 1999 and all forestry activities were ceased in recent years. In 1991 stands dominated by Betula pendula and B. pubescens prevailed in the Gorki Reserve; they covered 62% of the forested area. Stands dominated by Quercus robur and Tilia cordata covered only 14% of the area; 11% and about 1% of the area were covered by stands where Pinus sylvestris and Picea abies dominated, respectively (Fig. 4.28). According to the history of these forested lands, we have distinguished the following two groups of communities located on watersheds: (i) stands developed after frequent and repeated cutting (the cutting cycle lasted from 50 to 70 years) on lands which were not ploughed for at least the last 200 or 300 years, and (ii) communities developed on arable lands that were abandoned at different times.

4.5.2  G  eneral Description and Species Diversity of the Vegetation Communities Among the group of forests that developed on lands that became afforested since about a hundred years ago following repeated earlier clear-cuts, we distinguished (1) nemoral herb broad-leaved forests dominated by Tilia cordata and/or Quercus

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Fig. 4.28  Forest tracts in the Gorki Reserve dominated by (1) the deciduous small-leaved trees Betula spp., Populus tremula and Alnus spp., (2) the broad-leaved trees Tilia cordata, Quercus robur, Acer platanoides and Ulmus glabra, (3) Pinus sylvestris and (4) Picea abies according to forest inventory data of 1991. I, II and III are the Korobovskiy, Syanovskiy and Bogdanovskiy forestry units, respectively

robur, Querceto-Tilieta nemorosa (here and below according to the Prodromus of the hemiboreal forests, Sect. 4.1) and (2) nemoral herb birch forests, Betuleta nemorosa. Querceto-Tilieta nemorosa is the least disturbed forest type in the Reserve although it differs greatly from the well-preserved hemiboreal forests especially in its structure, the absence of Picea abies and by the limited number of broad-leaved trees. Quercus robur and/or Tilia cordata dominate in the overstorey. Acer platanoides rarely occurs; other broad-leaved trees, such as Fraxinus excelsior, Ulmus glabra and U. laevis are absent from the stands with a few exceptions (see below). The proportion of the pioneer trees Betula pendula, B. pubescens and Populus tremula does not exceed 30% in the stands. Fallen broad-leaved trees are practically absent and a gap-mosaic in the canopy did not develop. Tilia cordata or Corylus avellana and Lonicera xylosteum often dominate in the understorey. The typical nemoral species Aegopodium podagraria, Carex pilosa, Mercurialis perennis, Pulmonaria obscura, Galeobdolon luteum, Dryopteris filix-mas, Ranunculus cassubicus and others dominate in different proportions in the field layer. Except for the plantations of Tilia cordata that occupy a small area in the Reserve, the nemoral herb broad-­ leaved forests developed through natural regeneration of forests after felling and other forest harvesting activities accompanied by intense forest grazing. Betuleta nemorosa occupies 16% of the forested Reserve area. These forests developed after felling of nemoral herb broad-leaved forests and subsequent forest grazing which suppresses the undergrowth of broad-leaved trees. Even-aged stands consist of Betula pendula and B. pubescens of 60–80 years old with participation of Populus tremula. Suppressed individuals of Tilia cordata and Quercus robur rarely occur in the overstorey. Corylus avellana, Lonicera xylosteum and sometimes undergrowth of Tilia cordata dominate in the understorey. Typical nemoral species,

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such as Carex pilosa, Galeobdolon luteum, Ranunculus cassubicus, Aegopodium podagraria, Asarum europaeum, Stellaria holostea, Mercurialis perennis, Paris quadrifolia, Pulmonaria obscura, Convallaria majalis, etc. dominate in the field layer. Among the communities located on abandoned arable lands we distinguished (1) meadow and nemoral herb birch forests (Betuleta prato-nemoroherbosa), (2) nemoral herb pine forests (Pineta nemorosa); (3) nemoral herb spruce forests (Piceeta nemorosa) and (4) mesophytous meadows and forest glades. Betuleta prato-nemoroherbosa occupies 46% of the forested Reserve area; it developed through spontaneous overgrowing of arable lands accompanied by grazing. Betula pendula and B. pubescens with an admixture of Populus tremula dominate in the overstorey. Broad-leaved trees are practically absent in the community; the diversity of shrub species is high. Lonicera xylosteum and Frangula alnus dominate in the understorey and shrubs of different ecological-coenotic groups, including the light-demanding species Crataegus sanguinea and Rosa majalis, also occur. Number and proportion of nemoral herbs is lower than in Betuleta nemorosa and depend on distance from the nearest broad-leaved forests. Species of different ecological-­coenotic groups occur in different proportions  in the field layer. The nemoral herbs Ajuga reptans, Galeobdolon luteum, Geum urbanum, Stellaria holostea, Aegopodium podagraria, Carex pilosa, Asarum europaeum, Convallaria majalis and Ranunculus cassubicus often dominate together with the meadow herb Fragaria moschata and the nitrophilous species Geum rivale and Deschampsia caespitosa. The meadow species Angelica sylvestris, Stachys officinalis, Succisa pratensis, Dactylis glomerata, Prunella vulgaris and others often occur. Atrichum undulatum, Cirriphyllum piliferum, Rhytidiadelphus triquetrus and Eurhynchium hians are common in the bottom layer. Pineta nemorosa is represented by small areas of Pinus sylvestris plantations of various ages (from 10 to 100, though mainly from 40 to 60 years old) located on sandy loams after clear-cutting and arable land abandonment. Besides Pinus sylvestris, Betula spp. and Populus tremula rarely occur in the stands; Picea abies and Ulmus laevis can be occasionally found. Improved light availability together with a stable seed influx of nemoral species from the surrounding areas (Fig. 4.28) lead to a high diversity in the understorey. In the undergrowth Betula spp., Salix caprea, Padus avium, Tilia cordata, Quercus robur and Sorbus aucuparia often occur. Lonicera xylosteum, Corylus avellana and Frangula alnus dominate among the shrubs; Sambucus racemosa often occurs. Nemoral and nitrophilous herbs and ferns, such as Impatiens parviflora, Ajuga reptans, Athyrium filix-femina, Dryopteris carthusiana, Pulmonaria obscura and Galeobdolon luteum dominate in the field layer; the boreal herb Oxalis acetosella also often occurs. Piceeta nemorosa occupies very small areas in the Reserve (Fig.  4.28). It is formed by plantations of Picea abies of various ages (from 10 to 80  years old). Betula spp., Populus tremula and Pinus sylvestris can be found in the overstorey, as well as Picea abies. The crown cover is dense (0.8–0.9) and that leads to a low diversity in shrubs and tree undergrowth. The shrubs Lonicera xylosteum, Euonymus verrucosa and Sambucus racemosa often occur, but in the field layer. The nemoral

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species Ajuga reptans, Galeobdolon luteum, Dryopteris carthusiana and Geum urbanum dominate in the field layer together with the nitrophilous species Athyrium filix-femina, Geum rivale and Impatiens parviflora. Rarely the boreal herb Oxalis acetosella dominates. In the bottom layer Cirriphyllum piliferum, Rhytidiadelphus triquetrus, etc. are common. Mesophytous meadows occupy about 4% of the Reserve area and include abandoned haymaking meadows, pastures and arable lands, which may also have been affected by forest grazing. The communities belong to the order Arrhenatheretalia Pawlowski et al. 1928. Meadow species, such as Alchemilla vulgaris, Stachys officinalis, Dactylis glomerata, Deschampsia cespitosa, Succisa pratensis, Hypericum maculatum, Veronica chamaedrys, etc. often dominate. Besides meadow species, nemoral species often occur; Ajuga reptans is common. Also nitrophilous species, such as Angelica sylvestris, Filipendula ulmaria, Geum rivale and Lysimachia nummularia often occur as well as the piny gramineous Calamagrostis epigeios. Adjacent to the plant communities on watersheds, there are nitrophilous tall herb forests dominated by Alnus incana and A. glutinosa (Alneta incanae nitrophilo-­ magnoherbosa and Alneta glutinosae nitrophilo-magnoherbosa); they are located in floodplains of small rivers and streams and occupy about 2% of the forested area. In the Reserve, these communities are heavily degraded due to forest grazing and other anthropogenic impacts. Padus avium and undergrowth of A. incana often occur in the understorey; the herbaceous climbing plant Humulus lupulus also often occurs. Nitrophilous species dominate in the ground layer; among them Athyrium filix-femina, Cardamine amara, Chrysosplenium alternifolium, Cirsium oleraceum, Filipendula ulmaria, Geum rivale, Stellaria nemorum and Urtica dioica often occur. The nemoral herbs and ferns Aegopodium podagraria, Dryopteris carthusiana and Galeobdolon luteum can be found. A direct ordination of vegetation plots sampled in the communities studied (Fig. 4.29) shows that the differences in ecological characteristics of the forest communities on watersheds are not large: the ecological ranges of these communities largely overlap. Meadows are clearly different from other communities: obviously they are the best illuminated communities and also cover the widest range of soil parameters. Soils in floodplain forests dominated by Alnus spp. are wettest and richest in nitrogen, as can be expected. Noteworthy is that the soil reaction and fertility are slightly higher in forests located on long-term forest lands (Querceto-Tilieta nemorosa and Betuleta nemorosa) as compared with those located on abandoned arable lands. This can be explained by depletion of the soil during the period of ploughing (Bobrovsky 2010). The similarity in ecological conditions and the common diagnostic species of the forest communities on watersheds allowed us to refer them to a single association: Mercurialo perrenis–Quercetum roboris Bulokhov et Solomeshch 2003 (= Querco roboris–Tilietum cordatae Laivinsh 1986 ex Laivinsh in Solomeshch et al. 1993) of the class Querco–Fagetea Br.-Bl. et Vlieger in Vlieger 1937 (Zaugolnova and Morozova 2004) according to the Braun-Blanquet approach. Forests located on floodplains belong to the alliance Alnion incanae Pawłowski, Sokołowski et Wallish. 1928 of the class Querco–Fagetea.

4  Hemiboreal Forests

a

297

8

Rc

7.5

7

6.5

6

12

12.5

13

13.5

14

14.5

15

15.5

Hd

b 6 5.5

Q BN

Lc

5

BM

4.5

PnN PcN

4

A

3.5 3 4.5

Md 5

5.5

6

6.5

7

Nt

Fig. 4.29  Two-dimensional ordination diagrams of 215 vegetation plots sampled in the Gorki Reserve and ordinated along gradients calculated by Tsyganov’s (1983) plant ecological tables. Q Querceto-Tilieta nemorosa (54 relevés), BN Betuleta nemorosa (43), BM Betuleta prato-­ nemoroherbosa (61), PnN Pineta nemorosa (24), PcN Piceeta nemorosa (10), A Alneta nitrophilo-magnoherbosa (7) and Md mesophytous meadows (16). Rc soil reaction, Hd soil moisture and Nt soil fertility: rank values are directly dependent on values of soil parameters. Lc light availability: rank values range from high light availability to more shady habitats

The forest communities on watersheds are the successional variants of the ass. Mercurialo perrenis–Quercetum roboris and the floristic similarity between the variants is not very high (Table 4.6): it varies from 0.5 to 0.7. The highest similarity is calculated between the pairs Querceto-Tilieta nemorosa /Betuleta nemorosa and Pineta nemorosa/Piceeta nemorosa. Mesophytous meadows are closest to Betuleta prato-nemoroherbosa and this confirms that the latter are formed during the

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Table 4.6  Jaccard similarity coefficients between the community types of the Gorki Reserve (from Korotkov 2000) Community types Q BN BM PnN PcN Md

BN 0.70

BM 0.57 0.63

PnN 0.58 0.62 0.60

PcN 0.51 0.59 0.52 0.69

Md 0.40 0.41 0.52 0.41 0.37

A 0.29 0.30 0.24 0.30 0.26 0.17

Note: community types are the same as in Fig. 4.29

o­ vergrowing of the meadows. Forest dominated by Alnus incana and A. glutinosa significantly differ in species composition, both from the other forest types as well as from the meadows. A total of 233 vascular plant species were recorded in the 215 vegetation plots: 7.3% of these were trees, 8.2 and 84.5%, respectively, were shrubs and herbs. Among trees and shrubs nemoral species prevailed. Among the herbaceous species the most numerous was a group of meadow species (39.6% of all herbaceous species), followed by species of the nemoral (24.9%), nitrophilous (14.2%), boreal (9.7%) and piny (3.5%) groups. The importance of water-marsh species (8.1%) was apparently underestimated due to the fact that we have not studied water and bank habitats on which there was no forest. The highest values for species density (average number of species per 100 m2) and species richness were calculated for mesophytous meadows and Betuleta prato-­ nemoroherbosa which were both the best illuminated communities (Fig.  4.29b). They also contained the highest number of meadow-edge species, but the number of species of other ecological-coenotic groups was also high in these communities (Fig.  4.30, top). Betuleta prato-nemoroherbosa also had the highest number of shrub and tree species among all communities (Fig. 4.30, bottom). Querceto-Tilieta nemorosa and Betuleta nemorosa had the lowest values for species density among the watershed communities due to the poor light availability under the dense tree canopy without gaps. Only nemoral species were well represented there, whereas the number of species from other ecological-coentoic groups was lowest. Pineta nemorosa and Piceeta nemorosa had medium values for vascular species density owing to an increased number of boreal species while the number of nemoral species were rather high (Fig. 4.30, top), whereas the species richness in forests dominated by Picea abies was lowest among the watershed communities (Fig.  4.30, bottom), probably, due to the small area occupied by this forest type (and the small number of relevés). The lowest values for species diversity were calculated for floodplain forests dominated by Alnus incana and A. glutinosa due to their severe degradation as a result of logging and forest grazing. Beta-diversity calculated by Whittaker’s index varied from 1.8 in Piceeta nemorosa to 3.3 in Querceto-Tilieta nemorosa but the total Whittaker’s index for the area was 6.7. This testifies that on the whole, the vegetation in the Gorki Reserve is fairly heterogeneous, but stands of the same communities are rather homogeneous in species composition.

Average number of species per 100 m2

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50 40

Wt

30

Md Pn

20

Nt Br

10

Nm

0 Q

BN

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PnN

PcN

Md

A

180

Species richness

150 120

Moss Herbs

90

Shrubs Trees

60 30 0 Q

BN

BM

PnN

PcN

Md

A

Fig. 4.30  Average ecological-coenotic structure of the species composition in the plots and species richness in the communities of the Gorki Reserve. Community types are the same as in Fig.  4.29. Ecological-coenotic groups: Nm nemoral, Br boreal, Nt nitrophilous, Pn piny, Md meadow-edge and Wt water-marsh groups (see Sect. 2.2)

4.5.3  S  tructure of the Tree and Shrub Populations in Different Forest Types On the whole, of the late-successional trees in the Gorki Reserve, Tilia cordata and Quercus robur commonly participate in the overstorey and understorey, while the participation of Picea abies is not large (Fig. 4.31). Tree undergrowth is absent in large parts of the area, i.e. in part of Korobovskiy and in almost all Bogdanovskiy forestry units (Fig. 4.31b). Most likely this is due to intensive forest grazing in the

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Fig. 4.31  Participation of late-successional tree species in the canopy (a) and in the understory (b) in the Gorki Reserve: 1 the broad-leaved trees Tilia cordata and Quercus robur  only; 2 Picea abies only; 3 Tilia cordata, Quercus robur and Picea abies together; 4 without Picea abies, Tilia cordata or Quercus robur (according to forest inventory data of 1991)

recent past which impeded the rejuvenation of tree species. After the grazing stopped, a dense shrub layer developed. Tree rejuvenation is also hampered by the high density of the tree canopy together with the absence of a stable seed flow of shade-tolerant trees, such as Fraxinus excelsior, Acer platanoides and Ulmus spp. 4.5.3.1  Querceto-Tilieta Nemorosa Only one small area with a fairly complete set of broad-leaved trees was found in the Gorki Reserve, in the Korobovskiy forestry unit. Although this area has experienced multiple clear-cuts and selective logging, the presence of a pit-and-mound topography originating from tree fall with uprooting testified the absence of clearing and ploughing of the area during the last 300 years. Besides Tilia cordata and Quercus robur, Fraxinus excelsior, Ulmus laevis and U. glabra occurred in the overstorey; the participation of Acer platanoides in the overstorey was slightly higher than in the other broad-leaved forests in the Reserve. Old and mature reproductive individuals of Quercus robur, Fraxinus excelsior and Ulmus spp. with trunk diameters of 60–70 cm and 28–32 m in height were found. Corylus avellana dominated in the understorey with an admixture of Euonymus verrucosa and Lonicera xylosteum. A high number of young individuals of Fraxinus excelsior occurred in the understorey, especially at a distance of 100–150  m from the reproductive trees. Undergrowth of Acer platanoides and Tilia cordata also often occurred; young vegetative individuals of Ulmus glabra and U. laevis rarely occurred. In addition to typical nemoral species, this forest contained species that are relatively rare in the Reserve, such as Galium odoratum, Campanula latifolia, Bromopsis benekenii,

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Polygonatum multiflorum, Carex digitata, Scrophularia nodosa, Stachys sylvatica and Millium effusum. The nitrophilous species Filipendula ulmaria, Athyrium filixfemina and Geum rivale occurred in the pits caused by treefalls. The spring-­growing and -flowering perennial species Anemonoides ranunculoides and Ficaria verna dominated in the field layer in spring. Unlike the described area, greatly disturbed broad-leaved forests characterized by a depleted composition of tree species occur more widespread in the Gorki Reserve (Fig. 4.32). Analysis of the ontogenetic structure of the tree and shrub populations in such forests, which are dominated by Quercus robur in the overstorey, shows their strong disturbance by often repeated felling in the past. Individuals of only a few tree and shrub species were proportionally represented in all ontogenetic stages in such a way that it guarantees a steady development from generation to generation (Fig.  4.33). Tilia cordata and Corylus avellana were among these species. It implies their permanent presence now and in future in the community. Quercus robur showed an invasive-regressive spectrum with peaks for the middle-aged reproductive coppiced individuals and for immature individuals with very low vitality. In the future we expect a decrease in number (up to a complete disappearance) of Quercus robur in the overstorey due to natural mortality of

Fig. 4.32  Nemoral herb broad-leaved forests dominated by Tilia cordata and Quercus robur in the overstorey and by Tilia cordata and Acer platanoides in the understorey, while Galeobdolon luteum dominates in the field layer, in the Korobovskiy forestry unit in the Gorki Reserve. Trees in the overstorey are 120 years old (Photo by V. Korotkov)

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1000 100 10

im v g1 g2 Corylus avellana Lonicera xylosteum Euonymus verrucosa

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Populus tremula

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Viburnum opulus

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Frangula alnus

Fig. 4.33  Ontogenetic structures of tree and shrub species populations in Querceto-Tilieta nemorosa dominated by Quercus robur in the Gorki Reserve

old individuals and the lack of opportunities for young individuals to grow due to the low light supply under the dense forest canopy. A similar prognosis can be made for Populus tremula with a similar type of ontogenetic spectrum. However, Populus tremula as well as Betula pendula and B. pubescens can survive in the canopy gaps caused by treefalls (Smirnova 2004). Therefore, in the future they will be represented by small numbers of individuals in the community. Acer platanoides had an invasive ontogenetic spectrum with a maximum for immature individuals with a normal vitality. In the future we may expect an increase in the number of this shade-­ tolerant species in the forests. Individuals of Corylus avellana, Euonymus verrucosa and Lonicera xylosteum were represented in all ontogenetic stages indicating their stable presence in the community. In forests dominated by Tilia cordata in the overstorey (Fig. 4.34) and with a low light supply under the canopy, only individuals of Tilia cordata and Corylus avellana occurred in practically all ontogenetic stages (Fig. 4.35). There were invasions of the shade-tolerant trees Acer platanoides and sometimes Fraxinus excelsior in the community owing to the permanent influx of seeds from single reproductive individuals of these species occurring in the stands. Other tree species had regressive ontogenetic spectra and, thus, we may expect their future disappearance from the community, especially of Quercus robur which cannot rejuvenate in gaps caused by treefalls. Shrub populations were poorly presented in the community due to light

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Fig. 4.34  Broad-leaved forest dominated by Tilia cordata in the overstorey and by the nemoral species Carex pilosa, Mercurialis perennis and Galeobdolon luteum in the field layer, in the Syanovskiy forestry unit in the Gorki Reserve. Tilia cordata in the overstorey is 90  years old (Photo by V. Korotkov)

scarcity: adult individuals occurred only in populations of Corylus avellana and Lonicera xylosteum. 4.5.3.2  Betuleta Nemorosa Old reproductive individuals prevailed in populations of the pioneer tree species Betula pendula and B. pubescens (Fig.  4.36) which dominated in this forest (Fig. 4.37). The single tree species for which individuals at all ontogenetic stages occurred was Quercus robur, but its population density was low; it amounted to 300–400 individuals per ha, but many individuals had a low vitality. In the near future old individuals of Betula spp. are expected to begin to fall; then light conditions will be improved due to gaps in the canopy and Quercus robur individuals can survive and grow up. Improving light conditions can be also realized by thinning. The Tilia cordata population showed an active development: it was invasive with a maximum for immature individuals with a normal vitality. The invasion of Acer platanoides was weak due to the low seed flow of this species from remote areas where Acer platanoides occurred in the canopy; Fraxinus excelsior was practically

O.V. Smirnova et al.

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Tilia cordata

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1000 100 10 im

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Viburnum opulus

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Number of stems per ha

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Fig. 4.35  Ontogenetic structures of tree and shrub species populations in Querceto-Tilieta nemorosa dominated by Tilia cordata in the Gorki Reserve

1000 100 10

1 j Tilia cordata

im

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g1 g2 g3 Quercus robur

Number of stems per ha

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100 10

1 v

g1 g2 g3 Betula pubescens

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j im Betula pendula

Acer platanoides

j im Corylus avellana

10000

v

g1 g2 g3 Lonicera xylosteum

10000 1000 100 10 1 j im Sorbus aucuparia Frangula alnus

Fig. 4.36  Ontogenetic structures of tree and shrub species populations in Betuleta nemorosa in the Gorki Reserve

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Fig. 4.37  Betuleta nemorosa dominated by Corylus avellana in the understorey and Carex pilosa in the field layer, in the Bogdanovsiy forestry unit in the Gorki Reserve. Betula spp. are 90 years old (Photo by V. Korotkov)

absent. Corylus avellana completely dominated in the understorey with a high number of individuals at different ontogenetic stages (Fig.  4.36). Lonicera xylosteum had a similar structure of its population spectrum but with a smaller number of individuals. The numbers of individuals of other shrub species were small but higher than those calculated for broad-leaved forests. On the whole, shrub populations were better represented than in Querceto-Tilieta nemorosa due to improved light conditions under the canopy of Betula spp. forest.

4.5.3.3  Betuleta Prato-Nemoroherbosa In this forest type there were no tree populations with individuals at all ontogenetic stages (Figs. 4.38 and 4.39). Betula pendula dominated in the overstorey and was absent in the understorey; only mature and old reproductive individuals occurred in the forest. Betula pubescens occurred in the overstorey and in the understorey, but there were only individuals renewed from coppicing which had grown up in small numbers after the regular thinning in the past. Populus tremula had an invasive-­ regressive spectrum with peaks for young and old reproductive individuals; the first, with low vitality, resulted from steady vegetative reproduction by root sprouts after

O.V. Smirnova et al.

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306

1000 100 10 1

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Betula pubescens Salix caprea

10000 1000 100 10 1

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Sorbus aucuparia Viburnum opulus

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Fig. 4.38  Ontogenetic structures of tree and shrub species populations in Betuleta prato-­ nemoroherbosa located in the Korobovskiy and Syanovskiy forestry units in the Gorki Reserve

cuttings. On the whole, improved light conditions under the Betula spp. canopy leads to an active renewal of trees and shrubs. The proportion of nemoral shrubs and the quantity of broad-leaved trees in the undergrowth depends on the distance from the seed sources of these species (Korotkov 1992, 1999; Moskalenko and Bobrovsky 2012, 2014; Evstigneev et al. 2013). In the Korobovskiy and Syanovskiy forestry units, Betuleta prato-­nemoroherbosa were located close to forests dominated by broad-leaved trees in the overstorey (Fig.  4.28). Therefore the undergrowth of Tilia cordata and Quercus robur was common there (Figs. 4.31 and 4.38). Young individuals of the light-demanding trees Salix caprea, Malus sylvestris, etc. also occurred. Among the shrub populations, Frangula alnus, Corylus avellana, Lonicera xylosteum and Viburnum opulus had complete ontogenetic spectra; the populations of other shrub species were invasive (Fig. 4.38). In Betula spp. forests dominated by meadow and nemoral herbs in the ground layer and located in the Korobovskiy forestry unit, we studied the renewal of nemoral tree and shrub species at different distances from broad-leaved forests in stages that had developed during 60–80  years after abandonment of arable lands (Korotkov 1992, 1999, 2000). Virginal individuals of Tilia cordata dominated with numbers of more than 5000 ind./ha inside a strip with a width of 50 m from the edge of broad-leaved forest and they suppressed the undergrowth of other species within

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that strip. At a distance of 50 to 100 m, the Tilia cordata undergrowth co-dominated with reproductive individuals of Corylus avellana and that agrees well with the published data on the range of dissemination of Tilia cordata (Udra 1988). Lonicera xylosteum often occurred at a distance of 80 to 170 m from the broad-leaved forest. At a distance of 120 to 250 m, the abundance of Tilia cordata and Corylus avellana decreased in the understorey and the participation of viable undergrowth of Quercus robur increased. At a distance of more than 150 m from the broad-leaved forest, the participation of all nemoral species significantly decreased and the share of plants distributed by birds (such as Sorbus aucuparia, Padus avium, Frangula alnus, etc.; Vladyshevsky 1980; Udra 1988) rose sharply. These species, in different proportions, began to dominate in the understorey of Betuleta prato-nemoroherbosa and Frangula alnus often dominated at the edges of these forests. At a distance of 700 m from the broad-leaved forest, the participation of Tilia cordata was small (it amounted to 200 ind./ha) and Corylus avellana was absent. In the Bogdanovskiy forestry unit, forests belonging to Betuleta prato-­ nemoroherbosa were located far from forests dominated by late-successional trees in their overstorey (Figs. 4.28 and 4.31): the nearest single reproductive individuals of Tilia cordata were located at a distance of not less than 400–500 m from the communities and reproductive individuals of Picea abies at a distance of 700–800 m. Only depressed coppice individuals of Quercus robur rather often occurred in stands

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of this forestry unit. As a result, the number of individuals making up the Quercus robur population was higher than that in populations of Tilia cordata and Picea abies, but it was, nevertheless, very small: only 30 ind./ha (Fig. 4.39). Picea abies and Tilia cordata had 6 and 7 ind./ha. Single young individuals of Ulmus glabra were also found. It should be noted that the vitality of young individuals of all tree species was high, with exception of Quercus robur. Thus, repeated forest felling and clearing of large areas accompanied by forest grazing led to a significant delay in tree renewal in the Bogdanovskiy forestry unit. Populations of shrub species were also worse developed there compared to those in the Korobovskiy and Syanovskiy forestry units (Figs. 4.38 and 4.39). Only Corylus avellana and Frangula alnus had complete ontogenetic spectra, but with less individuals than in the forests described above. In Betuleta prato-nemoroherbosa the participation of nemoral herbaceous species in the field layer decreased with the increasing distance from the edge of a broad-leaved forest. We studied the herbaceous species composition in the Korobovskiy and Syanovskiy forestry units at different distances from the ­broad-­leaved forests aiming to estimate the migration speed of nemoral species into abandoned arable lands (Korotkov 1992). We distinguished four groups of nemoral species according to their frequencies. The first group was formed by species which were not found in forests developed on abandoned arable lands whereas they occurred in the Reserve’s broad-leaved forests. Corydalis solida, Gagea lutea, Galium odoratum and Campanula latifolia belonged to this group. We can explain this by the limited possibilities for seed dispersal these species have without an animal agent of dissemination (which were probably lost in the forests studied). The second group was formed by species established only at a short distance from broad-leaved forests. Anemonoides ranunculoides, Mercurialis perennis, Lathyrus vernus and Viola mirabilis belonged to this group. Anemonoides ranunculoides was found only on sites located no more than 3 m from the edge of forests in the area that was since long afforested. Small groups of this species were rarely found at a distance of 10–15 m from the forest edge. Mercurialis perennis rarely occurred at a distance of up to 30 m; Lathyrus vernus of up to 50 m and Viola mirabilis of up to 80 m from the broad-leaved forest. The third group was formed by Stellaria holostea, Galeobdolon luteum, Asarum europaeum, Carex pilosa, Bromopsis benekenii, Melica nutans and Milium effusum. The limits of their mass distribution (up to 100–120 m from the broad-leaved forest) coincided with the area dominated by Corylus avellana and Tilia cordata in the understorey. Carex pilosa and Asarum europaeum dominated up to 80 m from the forest edge and sporadically occurred at a distance of 200 and 300 m, respectively. Galeobdolon luteum dominated up to 100 m whereas local occurrences were found at a distance of 300 m. Stellaria holostea was common up to 120 m and occasionally occurred at a distance of 200 m. Bromopsis benekenii often occurred up to 60 m after which its occurrence sharply decreased, but it was found up to a distance of 100 m from the broad-leaved forest.

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The fourth group consisted of the nemoral species Ranunculus cassubicus, Ajuga reptans, Convallaria majalis, Geum urbanum, etc., which often occurred in Betula spp. forests developed on abandoned arable lands regardless of the distance from the seed sources. At a distance of over 150 m, meadow species, such as Deschampsia caespitosa, Veronica chamaedrys, Stachys officinalis, Fragaria vesca, F. moschata, Luzula pilosa, Geranium sylvaticum, Impatiens parviflora, Elymus caninus, Carex sylvatica and others, began to dominate. 4.5.3.4  Pineta Nemorosa Middle-aged plantations of Pinus sylvestris (Fig. 4.40) mainly surrounded by broad-­ leaved forests (Fig. 4.28) and located on sandy loams are a good place for the natural renewal of late-successional tree species. Young individuals of Tilia cordata and Quercus robur showed good possibilities to replace Pinus sylvestris in the future (Fig. 4.41). The populations of shrub species also developed well under the light canopy. The highest number of shrub populations with complete or steady ontogenetic spectra was registered in this community: individuals of Lonicera xylosteum,

Fig. 4.40  Pineta nemorosa with Tilia cordata and Corylus avellana in the understorey dominated by Ajuga reptans and Galeobdolon luteum in the field layer, in the Bogdanovskiy forestry unit in the Gorki Reserve. Pinus sylvestris is 60 years old (Photo by V. Korotkov)

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Sambucus racemosa, Frangula alnus, Viburnum opulus and Corylus avellana at all ontogenetic stages (without senile individuals for some species) were represented there.

4.5.4  Forecasts of the Development of Island Forest Tracts Analysis of the ontogenetic spectra of tree and shrub populations allowed us to forecast the direction of the spontaneous development of the forest studied. Variants of successional dynamics depend on the history of the forest (economic use of the area in the past) and on features of seed dispersal and species settlement at current time. In the Korobovskiy and Syanovskiy forestry units we expect a development of forests dominated by Tilia cordata in the near future when old individuals of Betula spp. begin to fall (Fig. 4.42). In the Bogdanovskiy forestry unit, the restoration of Tilia cordata stands will be delayed due to the lack of seed and the presence of a dense shrub layer in the understorey. Acorns usually arrive in the area, but the light-­ demanding young individuals of Quercus robur cannot compete with shrubs and the

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Fig. 4.42  Formation of young Tilia cordata stands after treefalls of old individuals of Betula pendula in Betuleta nemorosa dominated by Carex pilosa in the field layer, in the Syanovskiy forestry unit in the Gorki Reserve (Photo by V. Korotkov)

Tilia cordata undergrowth and die. Probably, the participation of Quercus robur can increase after treefalls in the Bogdanovskiy forestry unit and at the edges of the Korobovskiy and Syanovskiy forestry units. We have ascertained the following features of the spontaneous development of vegetation in the study area at the termination of any economic activity in the forests regenerated after felling and ploughing accompanied by the stopping of forest grazing: (1) forests dominated by the shade-tolerant species Tilia cordata and Acer platanoides in the overstorey and Corylus avellana in the understorey are formed; (2) Populus tremula, Quercus robur and Betula spp. diminish in the overstorey; (3) the density of the understorey increases and many light-demanding trees and shrubs, such as Quercus robur, Salix caprea, Frangula alnus, Viburnum opulus, etc., decrease in importance and only Tilia cordata and/or Corylus avellana begin to dominate; (4) species diversity in the field layer decreases due to loss of numerous light-demanding meadow species, but the proportion of nemoral species enhances considerably. On the whole, forest communities in the Gorki Reserve are extremely simplified as a result of centuries of human activities in the area. They are forests with a relatively low species diversity, often an even-aged structure of the forest stands and a simplified spatial structure without a patchy organization of the forest

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canopy and without microsites caused by treefalls with uprooting. The greatest changes in species composition were found in forests on former arable lands: pure birch stands with a depleted set of forest species occur there. After logging, trees and shrubs that are able to coppice remain in the forests and also the majority of the herbaceous forest species are able to persist in the ground layer. These results are similar to those described in detail for the Moscow region by other researchers (Abaturov and Melankholin 2004). As the availability of seeds of late-successional trees and the probabilities of seedling survival are the most important factors of forest renewal, we came to the conclusion that when aiming at restoring forest ecosystems, it is necessary to apply forestry methods in communities that are severely disturbed by previous anthropogenic impacts. The most important forestry activities are tree planting and thinning in young stands as well as thinning of undergrowth and shrubs in mature stands aiming to save valuable trees, such as broad-leaved trees and Picea abies. A promising approach is the restoration of uneven-aged multi-species coniferous – broad-­ leaved forests through special logging combined with planting of missing tree species.

4.5.5  E  xperience in Restoration of Broad-Leaved Forest with Picea abies Experiments on the restoration of broad-leaved forests with Picea abies were established in post-arable forests dominated by Betula spp. in the Bogdanovskiy forestry unit (Korotkov 1999, 2005). The forestry unit has been chosen due to the poor state of forest ecosystems there: natural aging of the even-aged coppice birch forest accompanied by falls of old Betula spp. trees in the absence of a reliable natural regeneration of late-successional trees. First experiments were started in 1988. Gaps in the canopy were formed by selective cutting of several trees standing nearby in plots of 0.16–0.25 ha (Fig. 4.43). In 1989 acorns and saplings of Quercus robur were separately planted in the plots in dense groups of various sizes (“biogroups”); from 2 to 11 biogroups per plot (Korotkov 1999). By the end of the first growing season the density of Quercus robur individuals in the biogroups reached 0.8–4.9 ind./m2. In the sixth year after planting, the crowns of neighboring trees in most biogroups reached a closed canopy. At the seventh year after planting, the average heights of the oak saplings in the biogroups were between 180 and 210 cm with maximum values of 220–260 cm; the annual increase of saplings was 60–80 cm. Also at the seventh year after planting, seedlings from acorns reached average heights of 1.7–2.7 m with maximum values of 1.8–3.2 m; the annual height increase of seedlings was 50–90 cm. Seedlings and saplings did not significantly differ in growth parameters though the highest values were observed in seedlings.

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Fig. 4.43  Layout of the experimental plots in the 25th and 26th compartments of the Bogdanovskiy forestry unit. 1 borders of sub-compartments; 2 roads; 3 borders of the compartments; 4 plots with planted acorns or saplings of Quercus robur in 1989; 5 plots with planted Quercus robur, Picea abies, Fraxinus excelsior, Acer platanoides, Tilia cordata and Ulmus glabra in 1994 and 1995; 6 plots with planted saplings of Quercus robur in 1996 and 1997

In 1994 and 1995 special cuttings and planting were performed at nine additional plots of 0.15–0.16 ha (Fig. 4.43). Aiming to restore the diversity of late-successional tree species we have proposed schemes of biogroup locations for the following species: Quercus robur, Picea abies, Tilia cordata, Acer platanoides and Fraxinus excelsior. Sizes of plots and their locations were selected to provide optimal light availability for the development of a Quercus robur undergrowth and to promote the formation of a mosaic structure of the forest ecosystem. Acorns of Quercus robur, seeds of Fraxinus excelsior and saplings of other species were used to plant in densities of 4000–9000 ind./ha. The undergrowth with all species was well developed in the third or fourth year after the planting. In 1996 acorns of Quercus robur were planted at six new plots (Fig. 4.43), but almost all the seedlings were destroyed by wild boars. In 1997 saplings of Quercus robur were planted in the same place under a scheme of one seedling per site of 2 × 1 m. There were no thinning operations since 1999 in the Reserve. Re-sampling of the planted plots in 2009 showed that the individuals of Quercus robur in the plantations of 1989 were suppressed by young individuals of Corylus avellana and Salix caprea; the average heights of Quercus robur and Salix caprea were 5.8 and 9.8 m, respectively; during the last 5 years the average annual height increases of Quercus robur and Salix caprea were 40–50 and 70–80 cm, respectively. In 2009, the height of young individuals of Quercus robur in the plantations of 1997 was on average 6.7 m, but the mean heights of Salix caprea and Populus tremula was 9.5 m and 14.8  m, respectively. The mean heights of young individuals of Picea abies and Fraxinus excelsior in the plantations of 1995 were 9.9 and 8.6  m, respectively.

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Cover of the understorey in all planted plots was very high and that led to a decrease in species diversity in the ground layer and an increase in abundance of shade-­ tolerant herbaceous species. Our experience in the restoration of broad-leaved forests with Picea abies showed that young individuals of Quercus robur cannot successfully compete for light with shrubs and undergrowth of pioneer trees without thinning, whereas undergrowth of Tilia cordata, Acer platanoides, Fraxinus excelsior and Picea abies is more vigorous than undergrowth of Quercus robur, but for the successful development of late-successional trees after planting the felling of pioneer trees which overtake late-successional species in growth rate is also needed.

4.5.6  Conclusion Forest history together with the availability of seeds of late-successional trees and probabilities of seedling survival define the current successional status of forests and the direction of their spontaneous development in the future. The late-­ successional trees Picea abies, Acer platanoides, Fraxinus excelsior, Ulmus glabra and U. laevis occur in greatly reduced numbers in the forest stands of the Gorki Reserve owing to severe anthropogenic impacts in the area during centuries. The natural regeneration of hemiboreal forests with a complex spatial structure and a high species diversity is impossible in island forest tracts in the coming centuries due to the scarcity of late-successional species. Our experience in the restoration of degraded forest ecosystems allowed us to offer the following main directions of forest management aiming to conserve biodiversity and to restore forest ecosystems: 1. Restore the patchy organization of the forest canopy by felling of groups of neighbouring trees to imitate gaps in the canopy caused by treefalls. The sizes of gaps and their spatial allocation have to be calculated in dependence on the light demands of the tree species and the distance of tree seed dispersal. We consider the optimal size of gaps in the canopy in the range of 0.1–0.3 ha (Smirnova 1994; Korotkov 2005). 2. Restoration of species diversity should be based on the natural regeneration of species combined with the planting of missing indigenous tree species. Thinning should provide the desired structure of the stands. Restoration of herbaceous species with a short radius of reproductive activity has to be carried out by special reintroduction methods (Tikhonova et al. 1995). 3. It is necessary to restore the genetic diversity of trees and to use heterogeneous seed sources from local populations of tree species.

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4.6  Conclusions on the Hemiboreal Forest Region The hemiboreal forests in European Russia present the maximum level of potential forest biodiversity of the entire forest region due to the fact that in this region the distribution areas of most boreal and nemoral plant species overlap. On the other hand, this region has a more favourable climate for the development of agriculture and other land-use practices, as compared to the boreal region, and that has led to a poor preservation and a high degree of destruction of the hemiboreal forests. The floristically richest, uneven-aged forests are preserved only in the sparsely populated areas which are the most difficult for economic development. Hemiboreal forests that are less disturbed by man are dominated by Picea abies or P. obovata with Abies sibirica and Tilia cordata in the overstorey and boreal and nemoral tall herbs and ferns in the understorey. These forests more often occur on foothills and mountains on the western macroslope of the Ural Mts (Popadyuk et al. 1999; Yaroshenko et al. 1999; Gorichev et al. 2006; Shirokov et al. 2006, etc.). They are characterized by the highest species and structural diversity in all vegetation layers and by a complex, patchy organization of their forest canopy and variation in microsites caused by treefalls, including treefalls with uprooting. At that, the widespread hemiboreal forests are the result of a complex combination of forest management efforts, including different types and intensities of logging and tree planting, forest fires, periods of free forest development as well as periods of forest clearing, ploughing and forest grazing. By far most of the hemiboreal forests consist of first-generation trees after cessation of exposure. This is evidenced by the analysis of remote sensing data: 97% of the hemiboreal forests are dominated by the pioneer trees Betula spp., Populus tremula or Pinus sylvestris and Larix sibirica and only 3% of the forests are dominated by late-successional dark-coniferous or broad-leaved trees (Bartalev et al. 2004; Fig. 1.9). Composition and structure of the forests vary significantly depending on type and frequency of impacts, availability of seeds of regional plant species and also on type of substratum/bedrock. On sandy soils lichen and green moss Pinus sylvestris forests form after fire and ploughing; these forests are similar to ones occurring in the boreal region. However, in the hemiboreal region, especially in its southern part, the large areas of Pinus sylvestris forests are forest plantations. Further development of these forests depends on the presence of seeds of broad-leaved trees and/or Picea spp. and Abies sibirica and that determines whether ultimately coniferous-broad-leaved, broad-leaved or dark-coniferous forests are formed. Boreal and nemoral species co-dominate in the ground layer of such forests (Smirnova and Shaposhnikov 1999; Zaugolnova 2000; Smirnova 2004). Such forests are described from the east of the Kostroma region (see Sect. 4.4) and from the Prioksko-Terrasnyi State Nature Reserve and Mariy Chodra National Park (numbers 15 and 25 in Fig. 2.1, respectively). In the Prioksko-­ Terrasnyi Reserve (Moscow region) analysis of forest inventory and vegetation data over a period of 50 years after the proclamation of the Reserve in 1945 showed that

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renewal of Pinus sylvestris completely stopped with fire protection of Pinus sylvestris forest on sandy soils. There the undergrowth and second layer of the canopy in the Reserve are dominated by Picea abies and/or Tilia cordata, Quercus robur and Acer platanoides; boreal and nemoral plants dominate in the ground layer (Chap. 5 in Smirnova and Shaposhnikov 1999; Chap. 4 in Zaugolnova 2000; Khanina and Bobrovsky 2004). In the Mariy-Chodra National Park (the Mari-El Republic) Pinus sylvestris, Populus tremula and Betula spp. forests dominate after fire and felling on sandy loams, but less disturbed forests dominated by Tilia cordata and Picea abies in the overstorey and by Aegopodium podagraria with Oxalis acetosella and Maianthemum bifolium in the ground layer also occur over small areas (Zhukova 2003; Zaugolnova and Bekmansurov 2004). On loams and sandy-loams plantations of Picea abies and Quercus robur can be found. However, overall pioneer deciduous forests dominated by Betula pendula, B. pubescens, Populus tremula and Alnus incana (in the west of the region) are wider spread; they usually form after felling and abandonment of ploughed lands. Further development of these forests, as well as forests on sandy soils, mainly depends on their distance from seed sources. Since seeds of spruce spread over longer distances than the seeds of broad-leaved trees (Smirnova et al. 2001), the small-leaved pioneer trees are often replaced by Picea spp. and as a result Picea spp. forests dominated by boreal and nemoral plants in the ground layer often develop. For example, such forests occur in the Central Forest State Nature Reserve which is located in the south-west of the Valday Upland (number 14 in Fig. 2.1). Picea abies forests occupy 47% of the Reserve area; small-leaved forests dominated by Betula pubescens, Populus tremula and rarely Alnus incana occupy 42% of the area; the rest of the area is occupied by bogs, swamps, and Alnus glutinosa forests along streams and small rivers. Broad-leaved trees only sporadically occur in the understorey though nemoral plants in the ground layer often occur (chapter 6 in Smirnova and Shaposhnikov 1999). Since the second half of the 1980s Picea abies forests in the Reserve are affected by mass windfalls, as also observed in the other Picea spp. forests in the hemiboreal region (Ulanova 2000; Sibgatullin 2006; Petukhov and Nemchinova 2015). Broad-leaved trees rarely establish after the windfalls probably due to the large distance of these areas from mass seed sources of broad-leaved trees. At the late stage of succession, tall herb Picea spp. (with Abies sibirica) forests form at places where broad-leaved trees are absent. These forests differ from similar forests in the boreal region by their large share of nemoral and nitrophilous herbs and ferns in the ground layer. Tall herb Picea obovata – Abies sibirica forests in the Basegi State Nature Reserve located on the western macroslope of the Middle Ural Mts (number 26 in Fig. 2.1) are examples of such forests. Tilia cordata and other broad-leaved trees are absent in the Reserve, but floristically rich, old-growth dark-­ coniferous forests are dominated by nemoral, boreal and nitrophilous tall herbs and ferns (Yaroshenko et al. 1999). It is noteworthy that, despite the structural changes in the past leading to a lack of Tilia cordata and other broad-leaved trees in the stands, a single cutting in the 1970s did not change the composition of the ground layer: forests have remained floristically rich and tall herbs and ferns dominate (Yaroshenko et al. 1999).

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In areas where Picea spp. and Abies sibirica are absent, but broad-leaved trees survived, pioneer deciduous trees are replaced by broad-leaved trees, such as Tilia cordata, Quercus robur, etc. (see Sect. 4.5; Korotkov 2000). Boreal species together with nemoral ones occur in the ground layer of the vegetation. In areas where seeds of both dark-coniferous and broad-leaved trees are available, less disturbed forests that are stable in their composition and structure can develop at the late successional stage after forest felling and clearing. However, in present-day hemiboreal forests this happens very rarely because of the huge gaps in distribution areas of broad-leaved trees and nemoral herbaceous species. Sometimes dark-coniferous – broad-leaved forests with boreal, nemoral and nitrophilous herbaceous species in the ground layer can be found in floodplains of small rivers and streams. For example, in the Bolshaya Kokshaga State Nature Reserve (number 24  in Fig. 2.1) dark-coniferous  – broad-leaved forests are preserved only in the central part of the Bolshaya Kokshaga River’s floodplain; they occupy 5% of all the Reserve’s area. Tilia cordata, Ulmus laevis and Picea abies dominate, Quercus robur, Abies sibirica and Acer platanoides occur in the overstorey of these forests; Filipendula ulmaria and other nitrophilous herbs often co-dominate with nemoral and boreal species in the ground layer. Such forests are absent on the watersheds in the Reserve (Braslavskaya 2014). The typical features of present-day hemiboreal forests, as they occur widespread in European Russia, are the following (Smirnova 2004): (1) pioneer deciduous or light-coniferous (Pinus sylvestris) forests dominate in the region; (2) among late-­ successional tree species either the dark-coniferous trees Picea abies, P. obovata and Abies sibirica or only broad-leaved trees, such as Tilia cordata, Acer platanoides, Ulmus glabra, U. laevis, Quercus robur, etc., dominate in the stands; (3) even-­ aged forests occur over vast areas, and (4) the structure of the vegetation in the ground layer is simplified as shown in the domination of species of one or two ecological-coenotic groups in that layer. In spite of these features, hemiboreal forests should not be regarded as the most disturbed forest ecosystems in European Russia due to several reasons. The most significant reasons are: (i) the forests occupy a relatively high percentage of the hemiboreal region (65% according to Bartalev et al. 2004), and (ii) in the area boreal and nemoral plant species, including tree species, are not threatened and that assures a comparatively high recovery potential in many forest ecosystems.

References Abaturov AV, Antyukhina VV (2000) Dinamika elnikov na territorii lesoparkovogo zashchitnogo poyasa Moskvy. In: Dinamika khvoynykh lesov Podmoskovya. Izd-vo Nauka, Moscow: 86–110 – Dynamics of spruce forests in the forest-park protective belt of Moscow Abaturov AV, Melankholin PN (2004) Estestvennaya dinamika lesa na postoyannykh probnykh ploshchadyakh v Podmoskovye. Izd-vo Grif i K, Tula. 336 pp – Natural dynamics of the forest on the permanent plots in the Moscow region

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sokhraneniya biologicheskogo raznoobraziya. Izd-vo Russkogo Botanicheskogo Obshchestva, SPb.: 469–497 – The Basegi State Nature Reserve Yaroshenko AY, Potapov PV, Turubanova SA (2001) The last intact forest landscapes of northern European Russia. Greenpeace Russia, Moscow. 73 pp Yarutkin IA (1981) Tipy elovykh i smeshannykh lesov Pravoberezhya Sredney Volgi. In: Biologiya rasteniy Srednego Povolzhya. Izd-vo MarGU, Yoshkar-Ola: 83–123  – Types of spruce and mixed forests on the right bank of the Middle Volga River Zaprudina MV (2012a) Mikromozaichnaya struktura travyano-kustarnichkovogo pokrova vysokotravno-­ paporotnikovykh pikhto-elnikov s lipoy Visimskogo zapovednika. Vestnik Tverskogo gosudarstvennogo universiteta. Ser. Biologiya i ekologiya 25(3): 112–119  – Micromosaic structure of the field layer in the tall-herb and large-fern Picea obovata and Abies sibirica with Tilia cordata forests in the Visimskiy State Nature Reserve Zaprudina MV (2012b) Mikromozaichnaya organizatsiya travyano-kustarnichkovogo i mokhovogo pokrova srednetayezhnykh temnokhvoinykh lesov Urala. Dissertation (Candidate of sciences) in biology. Moskovskiy pedagogicheskiy gosudarstvennyi universitet, Moscow. 204 pp – Micromosaic structure of the ground layer in the middle taiga dark-coniferous forests in the Ural Mts Zaugolnova LB (ed) (2000) Otsenka i sokhranenie bioraznoobraziya lesnogo pokrova v zapovednikakh Evropeyskoy Rossii. Izd-vo Nauchnyi Mir, Moscow – Assessment and conservation of forest biodiversity in the European Russian reserves Zaugolnova LB (2008) Podkhody k otsenke tipologicheskogo raznoobraziya lesnogo pokrova. In: Isaev AS (ed) Monitoring biologicheskogo raznoobraziya lesov Rossii: metodologiya i metody. Izd-vo Nauka, Moscow: 36–58 – Approaches to the assessment of typological diversity of forest cover Zaugolnova LB, Bekmansurov MB (2004) Suktsessionnye processy v rastitelnom pokrove nemoralno-borealnykh lesov na peschanykh substratakh i prognozy ikh razvitiya (na primere natsionalnogo parka “Mariy Chodra”). In: Smirnova OV (ed) Vostochnoevropeyskie lesa (istoriya v golocene i sovremennost), vol. 2. Izd-vo Nauka, Moscow, pp 125–131 – Successions in the nemoral-boreal forests on sandy soils and forecasts of their development with an example of the Mariy Chodra National Park Zaugolnova LB, Braslavskaya TYu (2003) Analiz associatsiy mezofitnykh shirokolistvennykh lesov v tsentre Evropeyskoy Rossii. Rastitelnost Rossii 4: 3–28 – The analysis of vegetation associations of mesophytic broad-leaved forests in the center of European Russia Zaugolnova LB, Martynenko VB (2014) Opredelitel tipov lesa Evropeyskoy Rossii. URL http:// www.cepl.rssi.ru/bio/forest/index.htm – Guide to the forest types in European Russia Zaugolnova LB, Morozova OV (2004) Rasprostranenie i klassifikatsiya nemoralno-borealnykh lesov. In: Smirnova OV (ed) Vostochnoevropeyskie lesa (istoriya v golocene i sovremennost), vol 2. Izd-vo Nauka, Moscow, pp 13–62 – Distribution and classification of the hemiboreal forests in European Russia Zaugolnova LB, Morozova OV (2006) Tipologiya i klassifikatsiya lesov Evropeyskoy Rossii: metodicheskie podkhody i vozmozhnosti ikh realizatsii. Lesovedenie 1: 34–48  – Typology and classification of forests in European Russia: methodological approaches and their feasibility Zaugolnova LB, Morozova OV (2012) Coenofond lesov Evropeiskoy Rossii. URL http://www. cepl.rssi.ru/bio/flora/index.htm – Coenofond of forests in European Russia Zaugolnova LB, Istomina II, Tikhonova EV (2001) Ekologicheskiy, tsenoticheskiy i floristicheskiy analiz grupp assoctsiatsii khvoino-shirokolistvennykh lesov tsentra Evropeyskoy Rossii. Rastitelnost Rossii 2: 38–48  – Ecological, coenotic and floristic analysis of the association groups of coniferous – broad-leaved forests in the center of European Russia Zaugolnova LB, Smirnova OV, Braslavskaya TYu, Degteva SV, Prokazina TS, Lugovaya DL (2009) Vysokotravnye tayezhnye lesa vostochnoy chasti Evropeyskoy Rossii. Rastitelnost Rossii 15: 3–26 – Tall herb boreal forests in the eastern part of European Russia

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Chapter 5

Nemoral Forests O.V. Smirnova, M.V. Bobrovsky, L.G. Khanina, T.Yu. Braslavskaya, E.A. Starodubtseva, O.I. Evstigneev, V.N. Korotkov, V.E. Smirnov, and N.V. Ivanova

Abstract  Nemoral forests occupy only 19% of the area, which is the lowest proportion of forested lands of all forest regions in European Russia. Most of these forests comprise Quercus robur and Pinus sylvestris plantations of different age along with a prominent part of Betula spp. forests that developed on abandoned agricultural lands and after severe clear-cuttings. The main feature of the nemoral region in European Russia is the existence of rather large tracts of old-growth forests dominated by Quercus robur and shade-tolerant broad-leaved trees, such as Fraxinus excelsior, Tilia cordata, Ulmus glabra, etc., which occur in areas that belonged to the defensive belts of Moscow State in the sixteenth and seventeenth centuries. These forests have experienced diverse anthropogenic impacts, and as a O.V. Smirnova (*) • T.Yu. Braslavskaya (*) Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia e-mail: [email protected]; [email protected] M.V. Bobrovsky (*) Institute of Physico-Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] L.G. Khanina (*) • N.V. Ivanova Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia e-mail: [email protected] E.A. Starodubtseva (*) Voronezh State Nature Biosphere Reserve, Voronezh, Russia e-mail: [email protected] O.I. Evstigneev Bryanskiy Les (Bryansk Forest) State Nature Biosphere Reserve, Nerussa, Bryansk region, Russia V.N. Korotkov (*) Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia e-mail: [email protected] V.E. Smirnov Center for Forest Ecology and Productivity of the Russian Academy of Sciences, Moscow, Russia Institute of Mathematical Problems of Biology RAS – Branch of the M.V. Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Pushchino, Moscow region, Russia © Springer Science+Business Media B.V., part of Springer Nature 2017 O.V. Smirnova et al. (eds.), European Russian Forests, Plant and Vegetation 15, https://doi.org/10.1007/978-94-024-1172-0_5

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consequence, the structure and composition of their vegetation are different. Forests with a rich composition of shade-tolerant trees, shrubs, and herbaceous species can be found on soils with a thick mull humus horizon. While successional changes in the vegetation lead to the development of nemoral herb forests dominated by ­shade-­tolerant broad-leaved trees, the highest plant diversity demands the sustainable existence of meadows and water-rich habitats. That is possible with the presence of herbivores which physically alter the habitats, such as Bison bonasus and Castor fiber, within the broad-leaved forest landscape. On the whole, due to a favorable climate and the diversity of human impacts, a relatively high level of forest biodiversity is still maintained in the nemoral region in spite of the obvious degradation of the forested lands.

5.1  P  rodromus of the Vegetation and Forest Distribution in the Nemoral Region The diversity of forest types is the highest in the nemoral forest region throughout the East European Plain and the western macroslope of the Ural Mts. This is so due to a combined effect of several factors, the main of which are (1) a high diversity of geomorphological features such as a combination of uplands, lowlands, “Polesie” relief, loess and carbonate rocks, etc., (2) a long history of intensive economic development of the region, and (3) climatic (temperature) conditions favorable for a large number of plant species. Nowadays, forests occupy 19% of the region’s total area (Bartalev et al. 2004). The proportion of land covered by forests is higher in the northern part of the region, and it decreases in the south to 8–11% (Bugaev et al. 2013). The region is divided into an area of broad-leaved deciduous forests in the north and a forest-steppe area in the south (Gribova et al. 1980). This differentiation was traditionally regarded as a consequence of the climatic gradient (Isachenko and Lavrenko 1980), but based on documented evidence (Popov 1937; Skryabin 1959; Bobrovsky 2002, 2007; Bugaev et al. 2013), it is recently acknowledged that land-use practices have significantly contributed to a strong deforestation of the region from ancient times up to now (see Sect. 5.2). The other peculiarity of the nemoral region is the presence of an almost continuous strip of ancient fluvial–glacial sandy lowlands (“zander”) on the border of the hemiboreal region (Polesie relief). These lands are traditionally considered part of the nemoral region though they are mainly covered by mixed deciduous–coniferous forests (Kuznetsov 1960; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Evstigneev 2010). Picea abies and Pinus sylvestris were mainly planted on sandy and sandy loam soils in zander landscapes (Skryabin 1959; Bobrovsky 2002, 2007; Evstigneev 2009), but because of an influx of boreal species, the broad-leaved forests on zander harbor a relatively higher species diversity (Bulokhov and ­ Semenishchenkov 2008). Additionally, dark coniferous – broad-leaved forests occur

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in the Southern Ural Mts, in the easternmost part of the nemoral region; it is believed that these forests are natural centers of occurrence of boreal species in the region (Martynenko et al. 2005, 2007, 2008).

5.1.1  Section: Lichen Forests In the nemoral region, only Pinus sylvestris forests co-dominated by lichens and green mosses in the ground layer belong to this section (Kuznetsov 1960; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Sultanova 2006; Martynenko et al. 2008; Evstigneev 2010). The lichen – green moss pine forests (Pineta sylvestris hylocomioso-cladinosa) belong to the association Cladonio arbusculae–Pinetum sylvestris (Caj. 1921) K.-Lund 1967 according to the Braun-Blanquet approach, and they are similar in structure and species composition to the corresponding hemiboreal forest communities. These forests can be found over the entire nemoral region in areas covered by weakly developed sandy soils. They are mainly located on river terraces and in fluvial–glacial landscapes. All trees in the overstorey are often middle aged and that indicates that they grew up after disturbances (fire). The pioneer successional character of these forests is also confirmed by long-term observations; for example, 30 years of observations in lichen – green moss pine forests located in zander landscapes showed a gradual transformation of these forests into green moss pine forests (Utekhin 1971).

5.1.2  Section: Green Moss Forests These forests dominated by green mosses in the ground layer are often dominated by coniferous trees in the overstorey and occur on sands and sandy loams mainly on Podzols; they are similar to corresponding forests located in the hemiboreal region and mainly belong to the class Vaccinio–Piceetea Br.-Bl. in Br.-Bl., Sissingh et Vlieger 1939. Although these forests are not so common in the nemoral region, they are diverse: we distinguish four subsections within the green moss forest section. They are the subsections of green moss – dwarf shrub, green moss – xerophilous herb, green moss – boreal small herb, and green moss – boreal tall herb forests. Below, we describe the most widespread forest types belonging to these subsections. Green moss – dwarf shrub pine forests (Pineta fruticuloso-hylocomiosa) are dominated by Pinus sylvestris and occur on sandy or sandy loam soils under mesophytic environmental conditions. These forests occur relatively widespread throughout the nemoral region (Remezova 1959; Kuznetsov 1960; Morozova 1999; Bobrovsky and Khanina 2000; Bulokhov and Solomeshch 2003; Blagoveshchensky

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2005; Sultanova 2006; Martynenko et al. 2007, 2008; Starodubtseva and Khanina 2009; Evstigneev 2010) and belong to the union Dicrano–Pinion (Libbert 1933) Matuszkiewicz 1962. In the west of the region, they belong to the ass. Dicrano ­polyseti–Pinetum sylvestris Preising et Knapp ex Oberdorfer 1957 or to the ass. Molinio caeruleae–Pinetum sylvestris (E.  Schmid. 1936) em. Mat. (1973) 1981 (Morozova 1999; Bulokhov and Solomeshch 2003). In the Southern Ural Mts, these forests belong to the ass. Antennario dioicae–Pinetum sylvestris Solomeshch et al. 1992 (Shirokikh et al. 2013). Sometimes these forests include adult trees or saplings of Picea spp.; they were described from moraine and zander landscapes on the Russian Plain in the north of the region (Kuznetsov 1960; Bulokhov and Solomeshch 2003; Evstigneev 2010). Such forests are referred to the subass. piceetosum abietis of the ass. Dicrano–Pinetum Bulokhov et Solomeshch 2003. Pinus sylvestris and Picea abies were mainly planted in these forests as is well documented in many areas (Skryabin 1959; Bobrovsky 2002, 2007; Evstigneev 2009, etc.). Green moss – dwarf shrub pine and oak forests (Querceto-Pineta fruticuloso-­ hylocomiosa) often develop at the first stage of succession from the green moss – dwarf shrub pine forests. Various broad-leaved trees can co-dominate with Pinus sylvestris in the overstorey, and Quercus robur is common. These forests are described from many areas throughout the region (Remezova 1959; Skryabin 1959; Kuznetsov 1960; Morozova 1999; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Martynenko et  al. 2003, 2005, 2007, 2008; Neshataev and Ukhachova 2006; Starodubtseva and Khanina 2009; Evstigneev 2010). In the west of the nemoral region, these forests are referred to the subass. quercetosum roboris of the ass. Dicrano–Pinetum Bulokhov and Solomeshch 2003. In the Southern Ural Mts, these mixed forests belong to the ass. Zigadeno sibirici–Pinetum sylvestris Martynenko et Zhigunova 2004 (Martynenko et al. 2007) in the north and to the ass. Pleurospermo uralensis–Pinetum sylvestris Martynenko et al. 2003 (Martynenko et al. 2003) or to the ass. Seseli krylovii–Pinetum sylvestris Martynenko et al. 2008 (Martynenko et al. 2008) in the south. All three associations belong to the subunion Brachypodio pinnatae–Pinenion sylvestris Martynenko 2009 of the union Dicrano–Pinion. Green moss – dwarf shrub birch and aspen forests (Betuleta (Populeta) fruticuloso-hylocomiosa), sometimes with Pinus sylvestris, develop usually after felling of Pineta fruticuloso-hylocomiosa. Green moss – dwarf shrub spruce (fir) forests (Piceeta (Piceeto-Abieta) fruticuloso-hylocomiosa) occur in the northern part of the Southern Ural Mts (Martynenko et al. 2008); these forests are referred to the ass. Linnaeo borealis– Piceetum abietis (Caj. 1921) K.-Lund 1962 (union Piceion excelsae Pawłowski, Sokołowski et Wallisch 1928). Green moss forests growing under dry environmental conditions often contain a large set of xerophilous herbs and grasses which replace dwarf shrubs in the ground layer. Green moss – xerophilous herb pine forests or green moss – xerophilous herb forests dominated by Pinus sylvestris with broad-leaved trees (mainly Quercus robur) or dominated by Betula spp. and Populus tremula in the overstorey can be found (Kuznetsov 1960; Morozova 1999; Bulokhov and Solomeshch 2003; Martynenko et al. 2003, 2005, 2008; Blagoveshchensky 2005). These forests belong to the ass. Peucedano–Pinetum Mat. (1962) 1973 of the union Dicrano–Pinion

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(Morozova 1999; Bulokhov and Solomeshch 2003) or to the ass. Veronico ­incanae–Pinetum Bulokhov et Solomeshch 2003 of the union Cytiso ruthenici– Pinion Krausch 1962 of the class Pulsatillo–Pinetea Oberd. 1992 (Bulokhov and Solomeshch 2003). In the Southern Ural Mts, communities of similar structure are referred to the ass. Zigadeno sibirici–Pinetum var. typica and to the ass. Pleurospermo uralensis–Pinetum sylvestris Martynenko et al. 2003 of the subunion Brachypodio pinnatae–Pinenion sylvestris in the union Dicrano–Pinion (Shirokikh et al. 2013). Small boreal herbs begin to co-dominate with green mosses in the ground layer when Picea spp. begin to replace Pinus sylvestris on sands and sandy loams. Green moss – small boreal herb spruce forests described from the west of the Russian Plain belong to the ass. Melico nutantis–Piceetum abietis of the union Melico– Piceion (Bulokhov and Solomeshch 2003). In the Southern Ural Mts, such forests are referred to the ass. Frangulo alni–Piceetum obovatae Martynenko et Zhigunova 2007 (in the north of the nemoral region) and to the ass. Violo collinae –Piceetum obovatae Martynenko et Zhigunov in Martynenko et al. 2005 (in the south of the region). Both latter associations belong to the union Aconito–Piceion (the subunion Tilio–Piceenion obovatae) of the order Abietetalia sibiricae (Ermakov in Ermakov et al. 2000) Ermakov 2006 in the class Querco–Fagetea (Martynenko et al. 2008). In the Southern Ural Mts, green moss – boreal tall herb spruce or dark c­ oniferous – broad-leaved forests occur (Martynenko et al. 2007, 2008). These forests belong to the associations Equiseto scirpoidis–Piceetum obovatae Martynenko et Zhigunova 2004, Chrysosplenio alternifolii–Piceetum obovatae Martynenko et Zhigunova 2007, and Cerastio pauciflori–Piceetum obovatae Solomeshch et  al. 1993 ex Martynenko et al. 2008 of the union Aconito–Piceion (Martynenko et al. 2007, 2008).

5.1.3  Section: Herb Forests Forests of this section are widest spread in the nemoral region. We distinguish the following subsections within the section of herb forests: nemoral herb, nemoral and nitrophilous tall herb, boreal and nemoral herb, xerophilous and nemoral (boreal) herb, meadow herb, and nitrophilous herb forests. Subsection of nemoral herb forests unites forests dominated by nemoral herbaceous species in the ground layer (characteristic species of the class Querco– Fagetea). They occur over the entire region. In the overstorey, they are dominated by the broad-leaved trees Quercus robur, Tilia cordata, Acer platanoides, Ulmus glabra, Fraxinus excelsior, and Acer campestre (the two latter species do not occur in the east of the region) or the pioneer deciduous trees Betula spp. and Populus tremula, or Picea abies (in the west)/P. obovata (in the east), or Pinus sylvestris together with broad-leaved trees. Nemoral herb broad-leaved forests (Querceta, Tilieta, Querceto-Tilieta nemorosa) are the typical mesophytic forests in the nemoral region (Isachenko 1980; Kurnaev 1980), while they are rather diverse in floristic composition. Nemoral

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herb broad-leaved forests usually occur on loams or sandy loams, on Luvisols, or rarely on Albeluvisols or Phaeozems; they often belong to various associations of the union Aceri campestris–Quercion roboris Bulokhov et Solomeshch 2003 (Bulokhov and Solomeshch 2003; Zaugolnova and Braslavskaya 2003). Features of forests of this union are the absence of coniferous trees and boreal herbaceous species (with exception of Maianthemum bifolium in a low abundance in some cases) and the presence of Acer campestre and Euonymus europaea which are characteristic woody species of this union in central and southeastern Europe. However, forest communities with these traits are not widespread throughout the nemoral region in European Russia. They can be mainly found on watersheds in the north of the Central Russian Upland (Zozulin 1955; Isachenko 1980; Kurnaev 1980; Bobrovsky and Khanina 2000; Ryzhkov 2001; Ukhachova and Lomova 2001; Alekseev et  al. 2002; Zaugolnova and Braslavskaya 2003; Poluyanov 2013). Some nemoral herb broad-­ leaved forests located within or close to the Central Russian Upland can include an admixture of Picea abies in the overstorey and boreal herbs with low abundance in the field layer. We also refer such forests to the union A.c.–Q.r. (Zaugolnova and Braslavskaya 2003). These communities occur on sandy loam soils on watersheds or in river valleys within ancient postglacial (moraine) or fluvial–glacial (zander) landscapes (Bobrovsky and Khanina 2000; Evstigneev 2010; Bulokhov and Solomeshch 2003; Zaugolnova et al. 2004; Starodubtseva and Khanina 2009). In the south of the Central Russian Upland, within the forest–steppe area, the nemoral broad-leaved forests on chernozems on loessial loamy soils are referred to the union Scillo sibiricae–Quercion roboris Onyshchenko 2009 (Poluyanov 2013). Nemoral herb broad-leaved forests located outside the Central Russian Upland have the following features: (1) the absence of Acer campestre and Euonymus europaea, (2) the presence of low-abundant boreal herbs in the field layer, and (3) an admixture of Picea spp. in the overstorey (within the distribution areas of these species). Such forests are quite similar to the ones in the hemiboreal region and belong to the union Querco roboris–Tilion cordatae Solomeshch et Laiviņs ex Bulokhov et Solomeshch 2003, most often to the ass. Mercurialo perennis–Quercetum ­roboris Bulokhov et Solomeshch 2003 (Bulokhov and Solomeshch 2003). Nemoral herb broad-leaved forests located to the west of the Central Russian Upland include Carpinus betulus and a small admixture of Picea abies in the overstorey (Bulokhov and Solomeshch 2003) like forests of the ass. Tilio–Carpinetum Tracz. 1962 described from the east of Central Europe (Matuszkiewicz 1981). These communities occurring on moraine covered by sandy loam soils are referred to the subass. M.p.–Q.r. carpinetosum betuli Bulokhov et Solomeshch 2003. In the east of the Russian Plain on the Middle Volga Upland, consisting of sandstone, nemoral herb broad-leaved forests are found on Luvisols and Phaeozems in watershed and in river valleys, and they are referred to the subass. M.p.–Q.r. caricetosum pilosae Zaugolnova et al. 2002 (Kuznetsov 1960; Zaugolnova et al. 2004; Blagoveshchensky 2005; Sultanova 2006). Further east, over the Volga River and up to the Southern Ural Mts, there are lowland and low-mountain broad-leaved forests in which the field layer is dominated by nemoral herbs and simultaneously includes low-abundant boreal tall herbs, whereas boreal small herbs are often absent; Fraxinus excel-

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sior and Corylus ­avellana are also absent in broad-leaved forests located over the Volga River (Gorchakovsky 1972; Isachenko 1980; Kurnaev 1980; Martynenko et al. 2005). These eastern broad-leaved forests are referred to the union Aconito septentrionalis–Tilion cordatae Solomeshch et al. 1993 (Martynenko et al. 2005). The presently still best preserved old-growth broad-leaved forests are dominated by several broad-leaved trees, such as Tilia cordata, Quercus robur, Fraxinus excelsior, Acer platanoides, and Ulmus glabra (Kuznetsov 1960; Kurnaev 1980; Chistyakova 1994; Bobrovsky and Khanina 2000; Ukhachova and Lomova 2001; Zaugolnova and Braslavskaya 2003; Blagoveshchensky 2005; Semenishchenkov 2009; Poluyanov 2013). In many communities, an admixture of pioneer deciduous trees (Betula spp. and Populus tremula) occurs and sometimes also an admixture of Pinus sylvestris and Picea spp. (Kuznetsov 1960; Bobrovsky and Khanina 2000; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Martynenko et al. 2005; Sultanova 2006; Starodubtseva and Khanina 2009). Trees in the overstorey reach more than 30 m in height; Quercus robur is often the largest among trees. Mature trees are often 100–150 years old, and they are the first generation of broad-leaved trees after planting or felling or agricultural land abandonment. Crowns usually cover more than 70%. This determines that an undergrowth of Quercus robur rarely occurs (Chistyakova and Popadyuk 1994) unlike an undergrowth of other broad-­ leaved trees which are more shade tolerant (Evstigneev 1994). Corylus avellana often dominates the shrub layer in most communities of the western and central parts of the region. Lonicera xylosteum, Euonymus verrucosa, Padus avium, Viburnum opulus, and Rosa majalis often occur with low abundance. Euonymus europaea and Swida sanguinea also often occur in the western and central areas of the nemoral region, whereas Frangula alnus and Sorbus aucuparia often occur in the east and in the Southern Ural Mts. Density of the shrub layer varies depending on both the tree crown coverage (Ryzhkov 2001; Blagoveshchensky 2005) and grazing impacts of livestock or wild ungulates (Gusev 1988; Vlasov 1997). Cover of the field layer varies from 50 to 80%. Spring-growing and -­flowering perennial herbs are very abundant. Of these, Allium ursinum and Dentaria spp. (most often D. bulbifera) occur only in the nemoral region; other spring-growing and -flowering species, such as Corydalis spp., Anemonoides spp., Gagea spp., Ficaria verna, and Lathraea squamaria, occur widespread in forests dominated by broad-leaved trees, in the nemoral as well as in the hemiboreal region. Shadetolerant summer-flowering nemoral herbs begin to dominate the field layer from mid-May. Aegopodium podagraria, Mercurialis perennis, or Carex pilosa are common and abundant. The nemoral herbs Convallaria majalis, Stellaria holostea, Asarum europaeum, Galium odoratum, and Galeobdolon luteum often occur with rather high abundance. Lathyrus vernus, Pulmonaria spp., Scrophularia nodosa, Geranium robertianum, Glechoma hederacea, Lamium maculatum, Stachys sylvatica, Dryopteris filix-mas, Polygonatum multiflorum, Viola mirabilis, Festuca gigantea, Milium effusum, Melica nutans, Elymus caninus, and Brachypodium spp. often occur with low abundance. Lunaria rediviva occurs in the west of the region in communities belonging to the union A.c.–Q.r. The boreal herbs Maianthemum

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­bifolium and Oxalis acetosella often occur with rather high abundance in communities belonging to the union Q.r.–T.c. in the west and the north of the nemoral region. Aconitum septentrionale, Crepis sibirica, Cacalia hastata, Cicerbita uralensis, and Festuca altissima often occur in the east of the region in forest communities belonging to the union A.s.–T.c. (Remezova 1959; Kuznetsov 1960; Kurnaev 1980; Smirnova 1987; Ukhachova and Lomova 2001; Alekseev et al. 2002; Bulokhov and Solomeshch 2003; Zaugolnova and Braslavskaya 2003; Zaugolnova et  al. 2004; Blagoveshchensky 2005; Sultanova 2006; Semenishchenkov 2009; Starodubtseva and Khanina 2009; Poluyanov 2013). Mosses usually cover about 1% of the bottom layer in nemoral broad-leaved forests due to a strong lack of deadwood and other microsites suitable for mosses. Natural treefall very rarely occurs in these forests nowadays owing to past and present felling (Popov 1937; Bobrovsky 2002, 2007; Evstigneev 2009). It should be noted that there are a lot of nemoral herb broad-leaved forests that developed after cutting and that are poor in their variety of herbaceous species although these forests are relatively rich in woody species. They occur throughout the region, on different soils. Poorest forests are mainly the old forest plantations on abandoned arable lands. Quercus robur and Acer platanoides of 60–70 years old often dominate the overstorey. Fraxinus excelsior and Tilia cordata often occur in the stands; Populus tremula, Betula pendula, and Ulmus glabra are rarer. One can find Acer campestre in the shrub layer. All mentioned tree species occur in all vegetation layers. Padus avium, Sorbus aucuparia, Corylus avellana, and Frangula alnus also often occur; Lonicera xylosteum and Euonymus verrucosa can be found. Of the herbaceous species, only those disseminated by animals occur. Mercurialis perennis usually dominates; Polygonatum multiflorum, Lathyrus vernus, Convallaria majalis, and Ranunculus cassubicus rarely occur. The moss layer is absent. Nemoral herb birch and aspen forests (Betuleta, Populeta nemorosa) dominated by the pioneer deciduous trees Populus tremula and Betula spp. (mostly B. pendula) develop under mesophytic environmental conditions after logging of forests dominated by nemoral herbs in the ground layer. These forests are most common in the northern part of the nemoral region; in the south, light-demanding mesophilous or xerophilous herbaceous species often increase in the ground layer after logging. Populus tremula and Betula pendula have rather similar environmental demands, but Betula pendula can be more successful under dry conditions than Populus tremula (Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Shirokikh et al. 2012). Among the broad-leaved trees, only stump sprouts of Tilia cordata can grow at a rate comparable to the rate of pioneer deciduous trees during natural reforestation after logging. As a result, Tilia cordata can occur as an admixture in the overstorey of these nemoral herb birch and aspen forests. When Betula spp. and Populus tremula are between 80 and 100 years old (this is about the maximum age for these species), shade-tolerant trees, such as Fraxinus excelsior, Acer platanoides, rarely Picea spp., and others, manage to reach the forest canopy. Thus, nemoral herb birch and aspen forests, even those in the Central Russian Upland, can be often referred to the ass. Mercurialo perennis–Quercetum roboris (Remezova

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1959; Kuznetsov 1960; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Semenishchenkov 2009). In nemoral herb birch and aspen forests of 60–80 years, the crown cover is usually high with 80% or more. The shade-tolerant Tilia cordata and Acer spp. often dominate the undergrowth. Diversity and abundance of shrubs vary depending on felling features (whether it took place in winter or summer, whether with stumps grubbing up or not, etc.) and on grazing by wild ungulates or domestic cattle (the latter was common in forests till the 1980s). Presently, cover of the shrub layer is usually about 20–40%. Corylus avellana is common. Lonicera xylosteum, Viburnum opulus, Padus avium, Rosa majalis, Euonymus spp., and Swida spp. occur; E. verrucosa occurs throughout the region, E. europaea and S. sanguinea in the west, and S. alba mainly in the east. Cover of the field layer varies from 25 to 95%; it is often dominated by Carex pilosa or Stellaria holostea, especially in Betula pendula forests (Kuznetsov 1960; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Sultanova 2006; Semenishchenkov 2009; Starodubtseva and Khanina 2009). Meadow species, such as Deschampsia cespitosa, Anthriscus sylvestris, Poa pratensis, Phleum pratense, etc., persisting from the well-illuminated post-logging conditions, often occur in low abundance; the hygrophilous herbs Filipendula ulmaria, Lysimachia vulgaris, etc. can also be found (Bulokhov and Solomeshch 2003; Semenishchenkov 2009). Mesophilous nemoral herbs, such as Aegopodium podagraria (more often in Populus tremula forests) or Galeobdolon luteum (only in the west) often co-dominate the field layer (Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Sultanova 2006; Starodubtseva and Khanina 2009). The abundance of spring-growing and -flowering species, such as Anemonoides spp., Gagea spp., and Corydalis spp., is often high. Within the forest-steppe area, a small admixture of xeromesophilous light-demanding species, such as Pyrethrum corymbosum, Stachys officinalis, and Clinopodium vulgare, occurs (Blagoveshchensky 2005; Starodubtseva and Khanina 2009). Boreal herbs can often occur after cutting and persist in low abundance (Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Semenishchenkov 2009). The moss layer is usually absent. Nemoral herb spruce forests with broad-leaved trees (Piceeta nemorosa) are described from the northwest of the nemoral region, where they occur on Luvisols and various variants of Podzols and Arenosols (Bobrovsky and Khanina 2000; Bulokhov and Solomeshch 2003). These forests belong to the var. Anemonoides nemorosa of the ass. Rhodobryo rosei–Piceetum abietis (Bulokhov and Solomeshch 2003). They mainly develop as a result of planting of Picea abies or Picea abies with Quercus robur after felling of nemoral forests. Cover of the overstorey is 60–70% and it is dominated by Picea abies and can include an admixture of Quercus robur and Betula pendula. Undergrowth of Acer platanoides and Tilia cordata often occurs. Cover of the shrub layer strongly varies from 1 to 80%. Corylus avellana is common and often dominates; Frangula alnus and Sorbus aucuparia also often occur; Euonymus verrucosa rarely occurs. Cover of the field layer varies from 30 to 65%. Galeobdolon luteum usually dominates the layer in summer, whereas Anemonoides nemorosa dominates in spring. The last is found as a single spring-growing and -flowering herbaceous species in these forests.

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The other nemoral herbaceous plants Asarum europaeum, Aegopodium podagraria, Carex pilosa, C. digitata, Stellaria holostea, Convallaria majalis, Lathyrus vernus, Pulmonaria obscura, Polygonatum multiflorum, Milium effusum, etc. often occur in low abundance. Fragaria vesca and the boreal species Oxalis acetosella, Maianthemum bifolium, Calamagrostis arundinacea, and Rubus saxatilis can also be found as well as single individuals of the dwarf shrubs Vaccinium myrtillus and V. vitis-idaea. The moss layer is absent. Nemoral herb broad-leaved forests with pine (Pineto-Querceta nemorosa) are described from the Central Russian Upland and adjacent areas (Bobrovsky and Khanina 2000; Bulokhov and Solomeshch 2003; Starodubtseva and Khanina 2009) and from the Middle Volga Upland (Blagoveshchensky 2005). These forests also occur in the Southern Ural Mts (Martynenko et al. 2005) in uplands situated amidst the forest-steppe area. In the west of European Russia, these forests occur on variants of Podzols and Arenosols (Bulokhov and Solomeshch 2003). In the Middle Volga Upland and in the Southern Ural Mts, these forests occur on sandy loam or gravelly soils covering slopes of different inclination. All these forests belong to the order Fagetalia sylvaticae. Forests located in the west and center of the region are referred to the union Querco–Tilion (preliminary to the ass. Corylo avellanae– Pinetum sylvestris Bulokhov and Solomeshch 2003). Forests in the Southern Ural Mts belong to the ass. Galio odorati–Pinetum sylvestris Martynenko et Zhigunov in Martynenko et al. 2005 of the subunion Tilio–Pinenion Martynenko et Shirokikh 2009 of the union Aconito–Tilion. These forests mainly developed as a result of cutting and subsequent planting of Pinus sylvestris. At the beginning of the development of these forests, light-demanding xerophilous and mesoxerophilous herbaceous species are abundant in the ground layer, and later, they are replaced by shade-tolerant nemoral herbs together with an increase in the participation of broadleaved trees in the stands. Sparse Pinus sylvestris individuals reach 20–25 m in height. Tilia cordata, Acer platanoides, Quercus robur, sometimes Ulmus glabra, Betula pendula, Sorbus aucuparia, Padus avium, etc. form the second sublayer of the canopy; some of them penetrate as an admixture in the first canopy sublayer. Total cover of the overstorey is 70–80%. Undergrowth of Acer platanoides and Tilia cordata often occurs; undergrowth of other broad-leaved trees can be found. The shrub layer is mainly formed by Corylus avellana in the western communities and total cover of this layer varies from 20 to 60%, but sometimes it is absent. In the eastern communities, the shrub layer is rare; its cover does not exceed 5–10%. In the west, Euonymus verrucosa often occurs in low abundance; in the east Rosa majalis and Lonicera xylosteum are common, and Daphne mezereum can be found. Total cover of the field layer varies from 20 to 90%. Carex pilosa and Stellaria holostea often occur and dominate; Aegopodium podagraria sometimes co-dominates (Bulokhov and Solomeshch 2003; Blagoveshchensky 2005). In the Southern Ural Mts, Aegopodium podagraria also dominates the field layer together with Galium odoratum (Martynenko et al. 2005). The nemoral herbs Convallaria majalis, Asarum europaeum, Viola mirabilis, Lathyrus vernus, Pulmonaria obscura, Milium effusum, and Melica nutans and the spring-growing and -flowering herb Anemonoides ranunculoides often occur. In the

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east, an admixture of xerophilous light-demanding species, such as Brachypodium pinnatum, Stachys officinalis, Dracocephalum ruyschiana, Pteridium aquilinum, and Adenophora liliifolia, is common together with the meadow species Fragaria vesca, Galium boreale, and Veronica chamaedrys; some boreal species, such as Rubus saxatilis, Calamagrostis arundinacea, Geranium sylvaticum, Vicia sylvatica, and Solidago virgaurea also often occur and always with low abundance. In the Southern Ural Mts, the tall herbs Aconitum septentrionale, Crepis sibirica, Bupleurum longifolium, and Cacalia hastata as well as the nitrophilous herbs Geum urbanum, Urtica dioica, Campanula trachelium, and Impatiens noli-tangere usually occur in low abundance. The moss layer rarely develops, but some mosses, such as Brachythecium spp. (especially B. reflexum and B. salebrosum), Leskeela nervosa, Hypnum pallescens, and Orthodicranum montanum, often occur in low abundance. Subsection of nemoral–nitrophilous tall herb forests unites forest communities dominated by mesophilous tall herbs in the ground layer. They mainly occur in the Southern Ural Mts and include forests dominated by broad-leaved trees or broad-­leaved trees with Picea obovata and Abies sibirica or forests dominated by Populus tremula. Forests dominated by tall herbs with a smaller participation of nitrophilous tall herbaceous species also occur in the northern part of the region; they are old-­growth broad-leaved forests (Bobrovsky and Khanina 2000). Nemoral and nitrophilous tall herb broad-leaved – dark coniferous forests (Abieto-Piceeto-Tilieta nemoro-magnoherbosa) occur throughout the Southern Ural Mts, at latitudes corresponding to both the broad-leaved forest and the foreststeppe areas (Gorchakovsky 1972; Martynenko et al. 2005, 2007, 2008). The forests belong to the subunion Tilio–Piceenion obovatae of the union Aconito septentrionalis–Piceion obovatae Solomeshch et al. 1993 ex Martynenko et al. 2008 in the order Abietetalia sibiricae (Ermakov in Ermakov et al. 2000) Ermakov 2006 of the class Querco–Fagetea. More mesophytic communities are referred to the ass. Brachypodio sylvatici–Abietetum sibiricae Martynenko et Zhigunova 2007 and more hygromesophytic communities are referred to the ass. Chrysosplenio ­alternifolii–Piceetum obovatae Martynenko et Zhigunova 2007. These forests are floristically very diverse, even though traces of selective cutting often occur. The forests occur on Phaeozems, Luvisols, and Retisols. Cover of the overstorey is 65–90%; the layer is formed by Tilia cordata together with Abies sibirica and Picea obovata and often includes an admixture of Ulmus glabra, Acer platanoides, Betula pendula or B. pubescens, and sometimes Populus tremula. Tree height in the overstorey varies from 18 to 25–30 m. Single individuals of Padus avium and Sorbus aucuparia of less height often occur; sometimes low individuals of Quercus robur can also be found. In mesophytic forests, Tilia cordata and Ulmus glabra always occur with high abundance in the undergrowth, and Acer platanoides often too; recruitment of Picea obovata and Abies sibirica is rarer. In hygromesophytic forests, undergrowth of Ulmus glabra with high abundance and Acer platanoides is common, and Abies sibirica can be found. The shrub layer is very sparse: its total cover never is more than 5%. Lonicera ­xylosteum, Viburnum opulus, and Euonymus verrucosa are common and Daphne mezereum is rarer. Cover

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of the field layer varies from 30 to 95% and species diversity is high. The tall herbs Cicerbita uralensis, Aconitum septentrionale, and Crepis sibirica are usually highly abundant and co-dominated by the nemoral species Aegopodium podagraria or Carex pilosa. In hygromesophytic communities, the tall ferns Matteuccia struthiopteris and Dryopteris filix-mas always occur in high abundance. The nemoral species Galium odoratum, Asarum europaeum, Viola mirabilis, Lathyrus vernus, Stellaria holostea, S. bungeana, Pulmonaria obscura, Campanula latifolia, Glechoma hederacea, Stachys sylvatica, Bromopsis bennekenii, and Melica nutans and different tall herbs and grasses, such as Actaea spicata, Cacalia hastata, Senecio nemorensis, Festuca altissima, Brachypodium sylvaticum, Lilium martagon, Knautia tatarica, etc., often occur; the piny fern Pteridium aquilinum and the boreal herb Lamium album also often occur; the typical boreal herbs Oxalis acetosella and Maianthemum bifolium can be rarely found in low abundance. The spring-­growing and -flowering herb Anemonoides ranunculoides sometimes occurs. The moss layer is sparse or absent, but sometimes cover of the moss layer can reach 10–25%, and then Brachythecium spp. (especially B. reflexum and B. salebrosum), Plagiomnium cuspidatum, Leskeela nervosa, Hypnum pallescens, and Callicladium haldanianum are common. Nemoral and nitrophilous tall herb broad-leaved forests (Tilieta nemoromagnoherbosa) are described from uplands in the southern part of the Southern Ural Mts, within the forest-steppe area where dark coniferous trees occur only along small rivers and streams (Gorchakovsky 1972; Martynenko et al. 2005). These forests occur on Phaeozems, Cambisols, and Chernozems on tops of plateaus and on slopes (often steep ones) of low mountains. Plant diversity is high there, may be due to light land-use activities on steep slopes. These forests belong to the ass. Stachyo sylvaticae–Tilietum cordatae Martynenko et Zhigunov in Martynenko et al. 2005 of the union Aconito–Tilion in the order Fagetalia sylvaticae. It is noteworthy that Quercus robur is absent, although it occurs in similar landscapes in broad-­leaved forests dominated by boreal and nemoral herbs in the ground layer (see below). The overstorey is usually dense: total cover is 65–90%. Tree height in the overstorey varies from 15 to 32 m. Tall individuals of Tilia cordata, Acer platanoides, and Ulmus glabra dominate. A small admixture of other deciduous trees, such as Populus tremula, Betula pendula, Sorbus aucuparia, and Padus avium, is usual (individuals of the latter two species are lower than those of others). Undergrowth of Ulmus glabra and Acer platanoides in high abundance is common, whereas undergrowth of Tilia cordata, Picea obovata, and Abies sibirica is relatively rare. The shrub layer is not developed, and total cover of the shrub species does not exceed 2%; Lonicera xylosteum, Viburnum opulus, Euonymus verrucosa, and Daphne mezereum rarely occur. Cover of the field layer often reaches 60–80%. The tall herbaceous species Cicerbita uralensis, Aconitum septentrionale, Crepis sibirica, Dryopteris filix-mas, Urtica dioica, and Brachypodium sylvaticum dominate in high abundance together with the common nemoral herbs Aegopodium podagraria, Stellaria holostea, and Galium odoratum. Other nemoral and nitrophilous species, such as Asarum europaeum, Viola mirabilis, Lathyrus vernus, Stellaria bungeana, Pulmonaria obscura, Campanula latifolia, Glechoma hederacea,

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Stachys sylvatica, Polygonatum multiflorum, Melica nutans, Cacalia hastata, Senecio nemorensis, Festuca altissima, Lathyrus gmelinii, Lamium album, Impatiens noli-tangere, Geum urbanum, Paris quadrifolia, etc., also often occur. Among the boreal species, Calamagrostis arundinacea and Rubus idaeus often occur. The moss layer is absent. Nemoral and nitrophilous tall herb aspen forests (Populeta nemoromagnoherbosa) are described from the Southern Ural Mts, from the boundary between broad-leaved forest and forest-steppe areas and within the last one (Shirokikh et al. 2012). These communities develop after logging of forests dominated by nemoral and nitrophilous tall herbs in the ground layer. In low mountains located in the northern part of the Southern Ural Mts, such forests belong to the subass. populetosum tremulae Shirokikh et al. 2012 of the ass. Stachyo sylvatici– Tilietum cordatae Martynenko et Zhigunov in Martynenko et al. 2005 of the union Aconito–Tilion in the order Fagetalia sylvaticae. In mountains located in the ­southern part of the region, these forests are referred to the subass. populetosum tremulae Shirokikh et al. 2012 of the ass. Cerastio pauciflori–Piceetum obovatae Solomeshch et al. 1993 ex Martynenko et al. 2008 of the union Aconito–Piceion of the order Abietetalia sibiricae (both of the class Querco–Fagetea). Note that lessdisturbed forests belonging to the ass. C.p.–P.o. are referred to the green moss – tall herb dark coniferous forests (see above), but the moss layer is degraded in the Populeta nemoro-magnoherbosa owing to the absence of dark coniferous trees due to these having been cut. In forests referred to the ass. Stachyo sylvatici–Tilietum cordatae, the overstorey is dense (cover is 70–90%), Populus tremula dominates, and an admixture of Betula pendula, Tilia cordata, Acer platanoides, and Ulmus glabra is abundant. Cover of the shrub layer does not exceed 10%, but undergrowth of the broad-leaved trees listed above often occurs; Sorbus spp., Padus avium, undergrowth of Quercus robur, and Lonicera xylosteum can also be found in the layer. In forests referred to the ass. Cerastio pauciflori–Piceetum obovatae, cover of the overstorey varies from 40 to 70%, and only single individuals of Betula pendula and Abies sibirica occur besides Populus tremula. Cover of the shrub layer varies from 1 to 20%; Daphne mezereum, Lonicera pallasii, Sorbus spp., and Ribes spp. often occur in low abundance together with undergrowth of Picea obovata and Abies sibirica. Cover of the field layer usually exceeds 60%. The tall herbs Aconitum septentrionale, Cicerbita uralensis, Crepis sibirica, and Rubus idaeus dominate the layer. In the ass. C.p.–P.o. Campanula latifolia, Pteridium aquilinum, Aconogonon alpinum, and Calamagrostis arundinacea also co-dominate the field layer. The xeromesophilous tall herbs and grasses Bupleurum longifolium, Pulmonaria mollis, Calamagrostis arundinacea, and Festuca altissima are common together with the nemoral herbs Stachys sylvatica, Polygonatum multiflorum, Campanula latifolia, Brachypodium sylvaticum, Aegopodium podagraria, Asarum europaeum, Galium odoratum, Lathyrus vernus, and Stellaria holostea; the boreal species Rubus saxatilis, Oxalis acetosella, and Geranium sylvaticum; the nitrophilous herbs Urtica dioica, Geum urbanum, and Impatiens noli-tangere; and the mesophilous meadow species Vicia sepium, Dactylis glomerata, and Veronica chamaedrys. At wetter sites, Filipendula ulmaria and

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Geum rivale can occur in low abundance. In the C.p.–P.o., cover of the moss layer varies from 1 to 15%; Plagiomnium cuspidatum and Sanionia uncinata occur sometimes with high abundance. Subsection of boreal-nemoral herb forests includes forests dominated by both nemoral and boreal herbaceous species in the ground layer. The overstorey can be dominated by the broad-leaved trees Quercus robur and Tilia cordata, sometimes mixed with Picea spp., or sometimes consisting of Picea spp. only, or of the broad-­ leaved trees with Pinus sylvestris and Larix sibirica (in the east), or the pioneer deciduous trees Populus tremula and Betula spp. Such forests occur throughout the nemoral region, mainly in its northern part. Boreal-nemoral herb broad-leaved forests (Tilieto-Querceta boreonemoroherbosa) are described from the northwest of the region (Bulokhov and Solomeshch 2003; Zaugolnova and Braslavskaya 2003; Semenishchenkov 2009) and from the central and eastern parts of the forest-steppe area (Blagoveshchensky 2005; Starodubtseva and Khanina 2009). The northwestern communities belong to the union Querco–Tilion. Most studied forests belong to the subass. carpinetosum betuli Bulokhov et Solomeshch 2003 of the ass. Mercurialo perennis–Quercetum roboris. These forests are located within moraine or fluvio-glacial landscapes in the west of the Central Russian Upland and mainly occur on Podzols and less often on Luvisols and Arenosols (Bulokhov and Solomeshch 2003; Zaugolnova and Braslavskaya 2003; Semenishchenkov 2009). Cover of the overstorey always exceeds 80%. This layer is dominated by Quercus robur of 22–24 m in height and Carpinus betulus of 16–18 m in height. Tall individuals of Picea abies, Populus tremula, and Betula pendula usually occur as an admixture; single lower individuals of Acer platanoides, Ulmus glabra, or Tilia cordata sometimes occur. Undergrowth of Tilia cordata and Acer platanoides is common. Cover of the shrub layer is often 1–2% or the layer is absent, but sometimes it covers up to 25%. Corylus avellana is common and is rather abundant; Euonymus verrucosa and Sorbus aucuparia rarely occur. Cover of the field layer is 40–60%. The nemoral herbs Galeobdolon luteum and Galium odoratum dominate in summer together with the small boreal herbs Maianthemum bifolium and Oxalis acetosella; the spring-growing and -flowering herbs Anemonoides ranunculoides and Corydalis spp. dominate in spring. The nemoral herbs Aegopodium podagraria, Carex pilosa, Stellaria holostea, Asarum europaeum, etc. often occur with low abundance. The moss layer is absent (Bulokhov and Solomeshch 2003). In the east of the region, these forests belong to the ass. Brachypodio pinnati– Tilietum cordatae Grigorjev ex Martynenko et Zhigunov in Martynenko et al. 2005 of the union Aconito–Tilion. The forests occur on dry gentle slopes of south and southwest expositions in the southern uplands of the Southern Ural Mts, mainly on Arenosols. Cover of the overstorey is usually 70–90%; the layer is formed by Tilia cordata and Quercus robur with an admixture of Betula pendula, Populus tremula, Sorbus aucuparia, and Pinus sylvestris. Undergrowth of Tilia cordata and Ulmus glabra is common, but not abundant. The shrub layer is usually absent or its cover does not exceed 1–3%; Rosa majalis, Lonicera xylosteum, Viburnum opulus, Daphne mezereum, and Euonymus verrucosa rarely occur. Cover of the field layer

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varies from 25 to 85%. The nemoral species Aegopodium podagraria, Stellaria holostea, Galium odoratum, and sometimes Carex pilosa dominate together with the boreal species Calamagrostis arundinacea and Rubus saxatilis and light-­ demanding species, such as Pteridium aquilinum, Carex rhizina, C. macroura, and Brachypodium pinnatum. Tall herbs and grasses, such as Crepis sibirica, Lathyrus gmelinii, Festuca altissima, Aconitum septentrionale, Cicerbita uralensis, Campanula trachelium, Digitalis grandiflora, and Bupleurum longifolium, sometimes occur with low abundance. The nemoral species Pulmonaria obscura, Asarum europaeum, Viola mirabilis, Lathyrus vernus, Melica nutans, Milium effusum, etc. and the boreal herbs Solidago virgaurea and Geranium sylvaticum also occur together with the light-demanding species Viola collina and Dactylis glomerata. The spring-growing and -flowering herb Anemonoides ranunculoides also sometimes occurs. The moss layer is usually absent, but Pleurozium schreberi or Abietinella abietina sometimes occur; Brachythecium reflexum, B. salebrosum, Leskeela nervosa, and Hypnum pallescens can also be found with low abundance (Martynenko et al. 2005). Boreal-nemoral herb broad-leaved forests are also described from the Middle Volga Upland (Blagoveshchensky 2005) and from the east of the Central Russian Upland (Starodubtseva and Khanina 2009). These forests belong to the union Querco–Tilion, and the overstorey includes an admixture of Pinus sylvestris. The boreal species Calamagrostis arundinacea, Rubus saxatilis, Orthilia secunda, and Maianthemum bifolium occur together with nemoral ones, such as Carex pilosa, Aegopodium podagraria, etc. It is believed that these forests are an intermediate successional stage from boreal and boreal-nemoral herb Pinus sylvestris forests to nemoral herb broad-leaved forests (Starodubtseva and Khanina 2009). Boreal-nemoral herb spruce – broad-leaved forests (Piceeto-Querceta boreonemoroherbosa) are described from the northwest and the center of the nemoral region where they occur on Luvisols, Arenosols, and rarer on Podzols (Kuznetsov 1960; Bulokhov and Solomeshch 2003; Sultanova 2006). The usual closed canopy and high abundance of Picea abies and Quercus robur in the overstorey, as well as the absence of these species in the understorey, indicate their planting after felling or abandonment of agricultural lands and the later natural renewal of the other broad-leaved trees. These communities are referred to the ass. Mercurialo ­perennis– Quercetum roboris of the union Querco–Tilion (Bulokhov and Solomeshch 2003; Zaugolnova et  al. 2004). In the Southern Ural Mts, almost all dark coniferous  – broad-leaved forests dominated by small and medium herbs in the field layer have a well-developed moss layer; therefore, they mainly belong to the section of green moss forests and are not discussed here. An example of boreal-nemoral herb spruce – broad-leaved forests is described from the Bryansk region (Bulokhov and Solomeshch 2003); it is referred to the subass. carpinetosum betuli of the ass. Mercurialo–Quercetum. Cover of the overstorey is high; it varies from 70 to 90%. Quercus robur and Picea abies of 26–28 m in height dominate in the overstorey; single individuals of Betula pendula, Populus tremula, or Pinus sylvestris also occur. There is a second sublayer in the canopy of 16–18 m in height, which is formed by Carpinus betulus and Tilia cordata with an

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admixture of Acer platanoides and Ulmus glabra. The shrub layer is very sparse: its cover is not more than 1–3%. Corylus avellana is common; Euonymus verrucosa and Sorbus aucuparia also rarely occur. Cover of the field layer is not high: it varies from 20 to 50%. The nemoral species Carex pilosa, Aegopodium podagraria, and Galeobdolon luteum co-dominate with the boreal species Maianthemum bifolium and Oxalis acetosella. The nemoral species Mercurialis perennis, Pulmonaria obscura, Galium odoratum, Stellaria holostea, Polygonatum multiflorum, Asarum europaeum, and Dryopteris filix-mas often occur in low abundance as well as the boreal species Solidago virgaurea, Rubus saxatilis, and Gymnocarpium dryopteris. The moss layer is absent. In the nemoral forest region, boreal-nemoral herb spruce forests (Piceeta boreonemoroherbosa) are always formed by planting of Picea abies. These forests are described from the west of the region, on Podzols and on rarely Arenosols (Bulokhov and Solomeshch 2003). They are referred to the subass. caricetosum pilosae of the ass. Rhodobryo rosei–Piceetum abietis. Cover of the overstorey is 60–80%; height of the overstorey is 28–30 m. Picea abies dominates the layer; Quercus robur occurs together with a small admixture of Betula pendula, Populus tremula, or Pinus sylvestris. Lower individuals of Acer platanoides of 18–21 m in height can be abundant, but usually, they are rare as well as individuals of Tilia cordata. Cover of the shrub layer mainly varies from 40 to 75%, though 5–20% also occurs. The layer is mainly formed by Corylus avellana and undergrowth of Acer platanoides; Euonymus verrucosa and Lonicera xylosteum often occur with low abundance; one can also find Daphne mezereum and undergrowth of Quercus robur, Tilia cordata, and Ulmus glabra. Cover of the field layer is about 40–50%. The boreal herbs Maianthemum bifolium and Oxalis acetosella dominate together with the nemoral Galeobdolon luteum. Some other nemoral species, such as Carex pilosa, Asarum europaeum, Dryopteris filix-mas, Aegopodium podagraria, Stellaria holostea, Melica nutans, and Carex digitata, often occur. The small boreal herbaceous species Gymnocarpium dryopteris, Luzula pilosa, Orthilia secunda, Trientalis europaea, Rubus saxatilis, and Solidago virgaurea always occur with low abundance. The tall boreal grass Calamagrostis arundinacea and the dwarf shrub Vaccinium myrtillus often occur with low abundance as well as some meadow herbs, such as Veronica chamaedrys, Agrostis tenuis, and Galium mollugo. The moss layer is not developed though Rhodobryum roseum and Pleurozium schreberi can often be found. Boreal-nemoral herb birch and aspen forests (Betuleta, Populeta boreo-nemoroherbosa) are forests at an intermediate stage of spontaneous development following different types of human impact, such as forest cutting, abandonment of agricultural lands, and others. They occur mainly on Arenosols. Tree ages usually vary from 30 to 80 years old (Evstigneev 2010; Shirokikh et al. 2012). The forests are referred to various associations, subassociations, or variants mainly of the classification units to which the previous communities belong. For example, mesophytic birch and aspen forests on sandy loam soil are referred to the subass. carpinetosum betuli or typicum, or caricetosum pilosae of the ass. Mercurialo–Quercetum in the union Querco–Tilion (Remezova 1959; Kuznetsov 1960; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Semenishchenkov 2009; Starodubtseva and Khanina

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2009; Evstigneev 2010). Xeromesophytic birch and aspen forests with Pinus sylvestris occurring on sandy soils are referred to the ass. Querco roboris–Pinetum sylvestris J. Mat. 1981 in the union Dicrano–Pinion (Libbert 1933) Matuszkiewicz 1962 (Morozova 1999; Evstigneev 2010). In the Southern Ural Mts, xeromesophytic boreal-nemoral herb birch and aspen forests are referred to the subass. ­betuletosum pendulae of the ass. Brachypodio pinnati–Tilietum in the union Aconito–Tilion (Shirokikh et al. 2012). Within the Russian Plain, the overstorey of mesophytic Betula spp. and Populus tremula forests is usually dense; cover is 70–90%, whereas under xeromesophytic conditions, cover of the overstorey does not exceed 30–50%. Besides Betula pendula and Populus tremula, an admixture of broad-leaved and coniferous trees often occurs. The shrub layer may be sparse (covering 1–5%) to quite dense (20–60%). In the last case, it is dominated by Corylus avellana. Euonymus verrucosa, Sorbus aucuparia, and Frangula alnus occur together with the undergrowth of broad-­ leaved or coniferous trees. Cover of the field layer is not high; it varies from 30 to 60%. In mesophytic forests, the layer is dominated by the nemoral herbs Galeobdolon luteum and Aegopodium podagraria together with the small boreal herbs Maianthemum bifolium and Oxalis acetosella; Gymnocarpium dryopteris and various nemoral herbs often occur in low abundance. In xeromesophytic forests, the nemoral sedge Carex pilosa often co-dominates with the xeromesophilous boreal species Rubus saxatilis. Convallaria majalis or Calamagrostis arundinacea can also co-dominate. Low-abundant boreal species, such as Orthilia secunda, Pyrola rotundifolia, Trientalis europaea, Luzula pilosa, etc., and dwarf shrubs Vaccinium myrtillus and V. vitis-idaea as well as Pteridium aquilinum and Molinia coerulea are common together with the nemoral species Stellaria holostea and Carex digitata. Light-­demanding meadow-edge species also often occur in low abundance. The mesophilous species Angelica sylvestris, Carex pallescens, Galium mollugo, Veronica chamaedrys, and Vicia sepium together with the hygrophilous species Lysimachia vulgaris occur in mesophytic communities; the xeromesophilous species Calamagrostis epigeios, Fragaria vesca, Clinopodium vulgare, and Hypericum perforatum occur in xeromesophytic forests. The moss layer is usually absent, but one can find some species, such as Pleurozium schreberi and Dicranum spp. (Remezova 1959; Kuznetsov 1960; Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Semenishchenkov 2009; Starodubtseva and Khanina 2009; Evstigneev 2010). In the Southern Ural Mts, boreal-nemoral herb birch and aspen forests occur under xeromesophytic conditions on loamy and marl-gravelly soils (Shirokikh et al. 2012). Cover of the overstorey varies from 35 to 90%. Besides Betula pendula and Populus tremula, the layer includes the broad-leaved trees Quercus robur, Acer platanoides, Tilia cordata, and Ulmus glabra and sometimes an admixture of Pinus sylvestris. The shrub layer is practically absent, but Rosa majalis often occurs and one can find Lonicera xylosteum, Viburnum opulus, or Frangula alnus; sparse undergrowth of all broad-leaved trees is common. Cover of the field layer varies from 15 to 90% depending on the density of the higher layers. Xeromesophilous nemoral species, such as Carex pilosa, Stellaria holostea, Galium odoratum, and

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Pulmonaria obscura, often dominate together with the mesophilous Aegopodium podagraria, Asarum europaeum, Milium effusum, and Viola mirabilis. Various xeromesophilous boreal species, such as Calamagrostis arundinacea and Rubus ­saxatilis, together with the piny fern Pteridium aquilinum and the steppe grass Brachypodium pinnatum often occur, sometimes with high abundance. Various xeromesophilous species, such as Pulmonaria mollis, Viola collina, Stachys officinalis, and Bupleurum longifolium; the light-demanding mesophilous species, Angelica sylvestris, Anthriscus sylvestris, Fragaria vesca, Heracleum sibiricum, Lamium album, Dactylis glomerata, and Galium boreale; and the tall herbs, Cacalia hastata, Aconitum septentrionale, and Trollius europaea, often occur in low abundance. The moss layer is absent. Boreal-nemoral herb broad-leaved forests with pine (Pineto-Querceta boreonemoroherbosa) occur on Arenosols and Podzols and are described from the entire nemoral region: from fluvio-glacial (zander) lowlands in the Bryansk Polesie (Morozova 1999; Evstigneev 2010), from north of the Central Russian Upland (Bobrovsky and Khanina 2000), from areas in the Oka-Don Plain (Remezova 1959; Starodubtseva and Khanina 2009), from the Middle Volga Upland, and from large alluvial lowlands close to the Volga River (Kuznetsov 1960; Blagoveshchensky 2005; Sultanova 2006). In the Southern Ural Mts, these forests also occur on Cambisols (Martynenko et al. 2005, 2007, 2008). These forests are mainly at the transitive stage of successional development of nemoral herb broad-leaved forests after planting of Pinus sylvestris. Plantings of Pinus sylvestris often with Quercus robur were widely practised on sands in the nemoral region in the late nineteenth and in the twentieth centuries (Skryabin 1959; Bobrovsky 2002, 2007; Evstigneev 2009, 2010). Planted pure Pinus sylvestris stands were gradually transformed into mixed forests with participation of broad-leaved trees (Utekhin 1971; Starodubtseva et al. 2004; Neshataev and Ukhachova 2006). This successional development can be interrupted by cuts or fires, but because broad-leaved forests can develop on sandy soils (Blagoveshchensky 2005), the process is always resumed again (Evstigneev 2010). General features of these forests are (1) the joint dominance of the light-­ coniferous trees Pinus sylvestris and Larix sibirica (in the east) and the broad-leaved trees Quercus robur, Tilia cordata, and others in the overstorey and (2) the absence of a well-developed moss layer. These forests are very diverse in their species composition and in the abundance of the common species, so that they are referred to different classes distinguished by the Braun-Blanquet approach. Within the Russian Plain, typical and widespread boreal-nemoral herb broad-leaved forests with pine belong to various associations of the union Dicrano–Pinion (Libbert 1933) Matuszkiewicz 1962  in the order Pinetalia sylvestris Oberd. 1957 of the class Vaccinio –Piceetea Br.-Bl. in Br.-Bl., Sissingh et Vlieger 1939 (Morozova 1999; Bulokhov and Solomeshch 2003) due to the dominance of Pinus sylvestris in the overstorey. Forests more dominated by Quercus robur in the overstorey (Remezova 1959; Kuznetsov 1960; Blagoveshchensky 2005; Starodubtseva and Khanina 2009) are referred to different associations of the union Quercion roboris Tx. 1931 in the order Quercetalia pubescenti-petraeae Klika 1931 of the class Querco–Fagetea

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(Morozova 1999; Bulokhov and Solomeshch 2003; Bulokhov and Semenishchenkov 2008; Evstigneev 2010). In the Southern Ural Mts, these forests are referred to several associations of the subunion Tilio cordatae–Pinenion sylvestris Martynenko et Schirokikh 2008 within the union Aconito–Tilion in the order Fagetalia sylvaticae of the class Querco-Fagetea (Martynenko et  al. 2003, 2005, 2007, 2008). Additionally, some boreal–nemoral herb broad-leaved forests with pine located in the Southern Urals are referred to the union Trollio europaea–Pinion sylvestris Fedorov ex Ermakov et  al. 2000  in the order Chamaecytiso ruthenici–Pinetalia sylvestris Solomeshch et Ermakov in Ermakov et  al. 2000 of the South Siberian class Brachypodio pinnati–Betuletea pendulae Ermakov, Koroljuk et Latchinsky 1991 (Martynenko et al. 2003, 2005, 2007, 2008). Pinus sylvestris usually forms the highest layer in the overstorey where tree heights vary from 20 to 28 m or even exceed 30 m in some cases. In forests located in the west of the region and referred to the order Quercetalia pubescentis-petraeae, Quercus robur individuals reach up to 20–25  m in height; then Pinus sylvestris forms the second sublayer in the canopy (Morozova 1999; Bulokhov and Solomeshch 2003; Evstigneev 2010). In the Southern Ural Mts, Larix sibirica can co-dominate in these forests (Martynenko et al. 2003). An admixture of Betula spp. is common in the canopy in the South Uralian communities, whereas in the Russian Plain forests, Betula spp. individuals rarely occur and they are smaller. An admixture of Populus tremula can also be found. Single individuals of Picea spp. sometimes occur (Kuznetsov 1960; Morozova 1999; Blagoveshchensky 2005; Sultanova 2006; Evstigneev 2010), and Abies sibirica also occurs in the Southern Ural Mts (Martynenko et al. 2007, 2008). In most communities dominated by Pinus sylvestris, the broad-leaved trees Tilia cordata (can be abundant in the South Uralian forests), Quercus robur, Acer platanoides, and Ulmus glabra form the second sublayer in the canopy of 10–18 m in height. Sorbus aucuparia and Padus avium can also be found. Cover of the overstorey varies from 30 to 80%. Cover of the shrub layer is usually less than 5%, but it increases to 15–25% when the undergrowth of broad-leaved trees, such as Tilia cordata and Acer platanoides, is abundant. Euonymus verrucosa may dominate the shrub layer (Martynenko et  al. 2007). Sorbus aucuparia, Frangula alnus, Rosa majalis, Lonicera xylosteum, and Daphne mezereum often occur in low abundance. Undergrowth of Picea spp. also often occurs in lowlands and the mountains of eastern areas as well as undergrowth of Abies sibirica in the Southern Ural Mts. Cover of the field layer is usually not more than 15–30% but reaches up to 50–70% in forests dominated by dwarf shrubs and located in the Southern Ural Mts; Calamagrostis arundinacea, Rubus saxatilis, sometimes Aegopodium podagraria, Galium odoratum, Carex rhizina or C. macroura, and Brachypodium pinnatum can also dominate there. In boreal–nemoral herb forests located in the Russian Plain, the first four species also often occur, but with low abundance as do the other herbaceous species; Molinia coerulea, Convallaria majalis, and Pteridium aquilinum are most common there. Small boreal herbs, such as Orthilia secunda, Maianthemum bifolium, Luzula pilosa, Pyrola rotundifolia, Geranium sylvaticum, Solidago ­virgaurea, and Trientalis europaea; various nemoral species, such as Stellaria

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­holostea, Carex digitata, Melica nutans, Lathyrus vernus, etc.; and the meadowedge species Fragaria vesca, Stachys officinalis, Viola collina, Galium boreale, Sanguisorba officinalis, Vicia sepium, and Veronica chamaedrys often occur in low abundance at different localities. Tall herbs, such as Bupleurum ­longifolium and Pleurospermum uralense, can also be found in the South Uralian forests. In some forests described from the west and center of the Russian Plain, Vaccinium myrtillus or V. vitis-idaea may occur in high abundance in the field layer (Bulokhov and Solomeshch 2003; Blagoveshchensky 2005; Bulokhov and Semenishchenkov 2008). The moss layer is usually absent, although one can find Pleurozium schreberi, Dicranum spp., and Sanionia uncinata with coverage of less than 10%. Subsection of xerophilous and nemoral (boreal) herb forests. Xerophilous and nemoral (boreal) herb forests are mainly dominated by Quercus robur, Pinus sylvestris, and Betula pendula. They occur throughout the nemoral region, mainly in its southern parts. These communities have a similar sparse structure of their tree layer and a similar structure of the field layer which differs from the other herb forests in the absence of dominating species and in a high diversity of xerophilous and mesoxerophilous herbaceous species. However, forests dominated by Pinus sylvestris with Betula pendula also contain a substantial number of boreal herbs, dwarf shrubs, and green mosses in the ground layer, and that makes them resemble the forests of the boreal-nemoral subsection and even green moss section. Though locally differing in details, the general spontaneous dynamics of all these forests leads to the development of nemoral herb broad-leaved forests. Xerophilous and nemoral herb broad-leaved forests (Querceta xerophyto-­ nemorosa) occur throughout the nemoral forest region, mainly in its central and southern parts, and also even further south than the southern boundary of the region, where they occupy restricted areas on watersheds amid dry steppe-meadow communities or agricultural lands. Quercus robur dominates the overstorey, which is usually not dense, as well as the shrub layer. Due to the semi-open spatial structure of the canopy, many light-demanding and xerophilous herbaceous species grow in these forests together with typical mesophilous nemoral herbs. Boreal species are practically absent in the field layer. Some researchers suggested that the structure and composition of these forests are due to climatic conditions (Kurnaev 1980). But selective cutting of Quercus robur and also livestock grazing certainly are also of significance in maintaining these communities (Zozulin 1955; Ryzhkov 2001; Blagoveshchensky 2005; Semenishchenkov and Poluyanov 2014). Within the Central Russian Upland, these communities occur between 50.5 and 53.3°N on Chernozems or Arenosols, often in ravines, on slopes of various inclinations (Zozulin 1955; Ryzhkov 2001; Poluyanov 2013; Semenishchenkov and Poluyanov 2014). In the Southern Ural Mts, these forests occur at the same latitudes on Phaeozems and Arenosols on flat tops and various slopes of low mountains (Solomeshch et al. 1992, 1993; Martynenko et al. 2005, 2008). Within the Middle Volga Upland, these communities are found on Arenosols over the rather wide latitudinal range from 50.3 to 54.3°N (Blagoveshchensky 2005). These forests also occur in the Oka-Don Plain on Phaeozems and Chernozems (Kamyshev and Khmelev 1976; Starodubtseva and Khanina 2009).

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In the west of the region, xerophilous and nemoral herb broad-leaved forests belong to the order Quercetalia pubescentis-petraeae Klika 1933, and they have been recently referred to the new subunion Crataego curvisepalae–Querceenion roboris Semenishchenkov et Poluyanov 2014 of the union Aceri tatarici–Quercion Zólyomi 1957 (Semenishchenkov and Poluyanov 2014). In the Southern Ural Mts, these forests lack some European species, such as Acer tataricum, Pyrus pyraster, Crataegus spp., Carex montana, and Potentilla alba, which are the diagnostic ones for the union A.t.–Q. and the order Q. p.-p., so they are referred to the union Lathyro–Quercion roboris Solomeshch et al. 1989 within the order Fagetalia sylvaticae (Solomeshch et al. 1992, 1993). The forests located in the east of the Russian Plain probably belong to the same union Lathyro–Quercion roboris due to their high similarity with the South Uralian communities. The forests are mainly coppice stands dominated by Quercus robur. Cover of the overstorey is usually about 50%; coppiced individuals are not very tall, so the overstorey is usually 12–18  m in height. A small admixture of Betula pendula often occurs in the overstorey; single trees of Populus tremula, Pinus sylvestris, Tilia cordata, Acer platanoides, Ulmus glabra, and Fraxinus excelsior (the last only in the west and center of the region) can be found. Cover of the shrub layer varies from 1 to 35% depending on canopy coverage and grazing intensity. Undergrowth of various trees, including Quercus robur, occurs; undergrowth of Acer campestre and Pyrus pyraster is locally abundant in the west. Euonymus verrucosa dominates; Cerasus fruticosa, Frangula alnus, and Sorbus aucuparia often occur in the shrub layer. Within the Central Russian Upland, Rhamnus cathartica, Acer tataricum, and Crataegus curvisepala are the most characteristic species of these communities, whereas to the east from the upland, the two first species occur more rarely and the third one is absent. In the east of the Russian Plain and in the Southern Ural Mts, Rosa spp. dominate the shrub layer, and Lonicera tatarica also occurs. The steppe dwarf shrub Caragana frutex is a typical species in the South Uralian forests. Chamaecytisus ruthenicus often occurs on sandy loam soil. Cover of the field layer varies from 30 to 70% depending on illumination under the canopy. None of the herbaceous species often dominates the layer, but the diversity of low-abundant xerophilous and mesoxerophilous herbaceous species is high. Among these Brachypodium pinnatum, Pyrethrum corymbosum, Phlomoides tuberosa, Digitalis grandiflora, Filipendula vulgaris, Vincetoxicum spp., Lathyrus spp. (V. hirundinaria and L. pisiformis everywhere; V. albowianum and L. litvinovii mainly in the South Uralian communities), Calamagrostis epigeios, Stachys officinalis, Clinopodium vulgare, Origanum vulgare, Fragaria viridis, F. vesca, Galium verum, G. tinctorium, Viola collina, V. hirta, and Serratula tinctoria are common; Peucedanum oreoselinum and Hieracium umbellatum are also common on sandy loam soil. The total abundance of xerophilous and mesoxerophilous herbaceous species is highest in this layer, though mesophilous meadow species, such as Dactylis glomerata, Galium boreale, Heracleum sibiricum, Veronica chamaedrys, Vicia sepium, Anthriscus sylvestris, Carex pallescens, C. muricata, and Elytrigia repens as well as the nitrophilous herbs Geum urbanum and Urtica dioica, also often occur.

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Nemoral species, such as Lathyrus vernus, L. niger, Melica nutans, Carex digitata, C. rhizina, Pulmonaria obscura, Galium odoratum, Aegopodium podagraria, Asarum europaeum, Glechoma hederacea, Stellaria holostea, Viola mirabilis, Polygonatum multiflorum, Geranium robertianum, or Melampyrum nemorosum, always occur in low abundance. The boreal species Calamagrostis arundinacea and Rubus saxatilis can be found. There are regional floristic specialists in the Querceta xerophyto-nemorosa. Carex montana, Convallaria majalis, Potentilla alba, and Geranium sanguineum occur only in the west of the region. The boreal herb Maianthemum bifolium and the piny fern Pteridium aquilinum can be found with rather high abundance in these forests located in the northwest of the region, in the Polesie relief. Geranium pseudosibiricum, Stellaria bungeana, Bupleurum longifolium, Serratula gmelinii, and the mesophilous tall herbs Aconitum septentrionale, Crepis sibirica, Senecio nemorensis, Aconogonon alpinum, and Lathyrus gmelinii occur only in the South Uralian communities. The steppe grass Stipa pennata can be found in these communities located in the east of the Russian Plain. The moss layer is not developed, but some low-­abundant mosses, such as Brachythecium salebrosum, Leskeella nervosa, and Pylaisiella polyantha, are common. It should be noted that the successional dynamics of these communities have been studied in some nature reserves. For example, Querceta xerophyto-nemorosa was described from the Central Black Earth State Nature Reserve in the 1920s–1930s as coppiced Quercus robur forests (Zozulin 1955). Massive oak withering happened in the 1940s–1950s, and as a result, many gaps in the canopy appeared that led to an increase of meadow herbs in the field layer, just as usually happens after selective cuts. The shade-tolerant trees Acer platanoides, A. campestre, A. tataricum, and Ulmus glabra that had gradually increased in the understorey subsequently reached the canopy; as a result, nowadays, cover of the overstorey is 60–70% despite the continuing fall of aged Quercus robur individuals (Ryzhkov and Ryzhkova 2006). The proportion of nemoral herbs also increases in the ground layer, and gradually, nemoral herb broad-leaved forests are developing. Xerophilous, nemoral, and boreal herb pine and birch forests (Pineto-Betuleta xerophyto-boreo-nemorosa) are described from the southern part of the entire nemoral region, mainly on Arenosols (Morozova 1999; Evstigneev 2010; Martynenko et al. 2003, 2005, 2008; Blagoveshchensky 2005). In the west of the region, these forests are described from the south of the Polesie relief and referred to the ass. Serratulo tinctoriae–Pinetum sylvestris J.  Mat. 1981 of the union Dicrano–Pinion (Libbert 1933) Matuszkiewicz 1962, of the class Vaccinio– Piceetea (Morozova 1999). In the Southern Ural Mts, these forests belong to several associations of the unions Caragano fruticis–Pinion sylvestris Solomeshch et al. 2002 and Veronico teucrii–Pinion sylvestris Ermakov in Ermakov et al. 2000 of the South Siberian class Brachypodio pinnati–Betuletea pendulae Ermakov, Koroljuk et Latchinsky 1991 (Martynenko et al. 2003, 2005, 2008). These forests described from the Middle Volga Upland do not include the Siberian species (Blagoveshchensky 2005) and are close to the union Dicrano–Pinion. These forests are mainly developed after planting of Pinus sylvestris, and they also gradually change as a result of the increase of broad-leaved trees (Neshataev and Ukhachova 2006).

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Cover of the overstorey varies from 35% to 60% and tree individuals in that layer vary from 12–15 to 20–24 m in height. Betula pendula and Pinus sylvestris always co-dominate in these forests throughout the region. Populus tremula often occurs in the overstorey in the west of the region and in communities located within the Middle Volga Upland; a small admixture of Quercus robur also occurs there. In the South Uralian forests, Tilia cordata, Acer platanoides, and Ulmus glabra also often occur in the canopy; Larix sibirica is rare and Sorbus aucuparia can be found in young forests. Undergrowth of Tilia cordata and Acer platanoides is common throughout the region and it is rather abundant sometimes. Undergrowth of Picea abies in the west and P. obovata in the east also often occurs. The shrub layer is sparse in the eastern and South Uralian forests; its cover varies from 1 to 15%. In the west of the region, the cover of the shrub layer often reaches up to 30–70% due to the permanent presence of Corylus avellana in high abundance. Euonymus verrucosa, Frangula alnus, and Sorbus aucuparia often occur throughout the region; Lonicera xylosteum and Genista spp. can be found. In the eastern and South Uralian communities, Chamaecytisus ruthenicus, Cerasus fruticosa, and Rosa spp. usually occur; Cotoneaster melanocarpus sometimes occurs. The steppe dwarf shrub Caragana frutex often occurs in low abundance in the Southern Ural Mts and also sometimes in the eastern communities of the Russian Plain. Rhamnus cathartica was noticed only in forests on the Middle Volga Upland. Cover of the field layer varies from 15 to 95% depending on the cover of the upper layers and green mosses. Usually, there is no significantly dominating species in the field layer. Various low-abundant xerophilous and xeromesophilous herbaceous species often occur. Common species among these are Campanula persicifolia, Filipendula vulgaris, Polygonatum odoratum, Fragaria viridis, F. vesca, Galium tinctorium, G. verum, Inula hirta, Stachys officinalis, Dracocephalum ruyschiana, Origanum vulgare, Clinopodium vulgare, Hieracium umbellatum, Serratula spp., and Geranium spp. (S. tinctoria and G. sanguineum in the Russian Plain, S. coronata and G. pseudosibiricum in the Southern Ural Mts), Vincetoxicum spp., Brachypodium pinnatum (except the western areas within the Polesie relief), Festuca ovina, F. valesiaca, and Calamagrostis epigeios. In the east of the Russian Plain and in the Souther n Ural Mts, Lathyrus pisiformis, Lilium pilosiusculum, Pyrethrum corymbosum, and Artemisia sericea are also common. Aizopsis hybrida, Poa transbaicalia, Bupleurum longifolium, and Digitalis grandiflora are common only in the Southern Urals. The xeromesophilous and mesophilous boreal species Calamagrostis arundinacea, Rubus saxatilis, Orthilia secunda, Solidago virgaurea, and Geranium sylvaticum usually occur as well as the piny fern Pteridium aquilinum. The dwarf shrubs Vaccinium myrtillus and V. vitis-idaea often occur in these forests in the Russian Plain but only in the east with high abundance. Arctostaphylos uva-ursi also rarely occurs there. Mesophilous meadow species, such as Galium boreale, Trifolium medium, Veronica chamaedrys, Elytrigia repens, Heracleum sibiricum, and Anthriscus sylvestris, always occur. Among the nemoral species, mainly xeromesophilous ones, such as Lathyrus vernus, Stellaria holostea, Melica nutans, Carex digitata, and C. macroura (in the Southern Ural Mts) often occur, while rarer species are Galium odoratum, Pulmonaria obscura,

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Convallaria majalis (in forests on the Russian Plain), Aegopodium podagraria, and Viola mirabilis. Green mosses always occur on the ground but often in very low abundance, though sometimes their cover reaches up to 50–60%; then Pleurozium schreberi and Dicranum spp. are common. Subsection of meadow herb forests includes forests on watersheds, the field layer of which is dominated by meadow herbaceous species, mainly grasses and forbs. These forests often occur in the nemoral region due to serious disturbances of forest ecosystems and fragmentations of forest lands in the course of economic development. Such forests develop on abandoned agricultural lands after mowing and ploughing, or they can be formed as a result of forest logging and grazing (Suslova 2006; Starodubtseva and Khanina 2009; Moskalenko and Bobrovsky 2012; Shirokikh et al. 2012). The pioneer deciduous trees Betula pendula and Populus tremula usually develop and dominate the canopy after clear-cuts. On abandoned arable lands Betula pendula or Salix caprea usually develop (Bobrovsky and Khanina 2015). Light-­demanding meadow-edge species, such as Deschampsia cespitosa, Dactylis glomerata, Veronica chamaedrys, Trifolium spp., Fragaria spp., and Achillea millefolium, often dominate the field layer; Leucanthemum vulgare, Hypericum maculatum, Prunella vulgaris, Stachys officinalis, Campanula patula, Viola canina, Anthriscus sylvestris, Vicia spp., Ranunculus spp., Plantago spp., Artemisia spp., Poa spp., Phleum pratense, Festuca pratensis, Elytrigia repens, and Carex contigua often occur (Suslova 2006; Semenishchenkov 2009; Starodubtseva and Khanina 2009; Moskalenko and Bobrovsky 2012; Shirokikh et al. 2012). The meadow herb birch and aspen forests (Betuleta, Populeta pratoherbosa) are referred to various subassociations within the class Querco–Fagetea, for example, to the subass. Geo rivali–Quercetum roboris deschampsietosum cespitosae Bulokhov et Semenishchenkov 2004 of the union Querco roboris– Tilion cordatae (Semenishchenkov 2009) or to the subass. Brachypodio pinnati– Tilietum cordatae betuletosum pendulae Grigojev ex Martynenko et Zhigunov in Martynenko et  al. 2005 of the union Aconito s­eptentrionalis–Tilion cordatae (Shirokikh et al. 2012), both in the order Fagetalia sylvaticae. After selective cuts, the previous tree layer is partially preserved and various mixed forests with pioneer deciduous tree species develop. In forests with Quercus robur, many nemoral herbs occur in the field layer together with many of the meadow herbs listed above (Suslova 2006; Starodubtseva and Khanina 2009). In forests with Pinus sylvestris, xeromesophilous and light-­demanding species, such as Calamagrostis epigeios, Agrostis tenuis, Tanacetum vulgare, Origanum vulgare, etc., often occur together with Fragaria vesca, Galium boreale, Achillea ­millefolium; the nemoral plants Convallaria majalis, Melica nutans, Carex pilosa, and C ­ . digitata; and the boreal species Calamagrostis arundinacea and Solidago virgaurea (Starodubtseva and Khanina 2009). Invasion of broad-leaved trees, especially Acer platanoides, into meadow herb forests often occurs together with a gradual change in species composition in the ground layer to the advantage of nemoral plants (Suslova 2006; Shirokikh et  al.

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2012; Bobrovsky and Khanina 2015). The rate of shade-tolerant tree invasion depends on the composition of surrounding forests, the presence or absence of artificial fires (Bobrovsky and Khanina 2015), forest grazing, and other features of forest use (e.g., features of recreational use). Thus meadow herb (“pastoral”) forests can exist for a long time in case of permanent disturbances of the succession process, whereas they can be replaced by forests with shade-tolerant trees and herbs if such disturbances are omitted. Subsection of nitrophilous herb forests. In the nemoral region, nitrophilous herbaceous species dominate in hygromesophytic and hygrophytic forest communities mainly belonging to the class Querco–Fagetea and sometimes to the class Alnetea glutinosae Br.-Bl. et Tx. 1943 em. Muller et Gors 1958. These forests are mainly situated on Phaeozems and Chernozems on watersheds and on Fluvisols in floodplains. Nitrophilous herbs, such as Urtica dioica, Geum rivale, Impatiens spp., Cardamine spp., and Chrysosplenium alternifolium, are common in all these forests together with species of moistened meadows, such as Filipendula ulmaria, Ranunculus repens, Lysimachia vulgaris, and L. nummularia. Hygromesophytic forests communities include nemoral and nitrophilous herb broad-leaved forests (Querceto-Tilieta nemoralo-nitrophiliherbosa) and forests dominated by pioneer deciduous trees developing after cutting of these communities. Such forests located in the west and center of the nemoral region are referred to the ass. Geo rivali–Quercetum roboris Bulokhov et Semenishchenkov 2004 (Semenishchenkov 2009) of the union Querco–Tililon (Morozova 1999; Semenishchenkov 2009; Starodubtseva and Khanina 2009; Evstigneev 2010). In the east of the nemoral region, hygromesophytic forests can be located in river and stream valleys, and they are often co-dominated by Pinus sylvestris and broadleaved trees (Martynenko et  al. 2003; Blagoveshchensky 2005). Nemoral and nitrophilous herb broad-leaved forests with pine (Pineto-Tilieta nemoralo-nitrophiliherbosa) located in the Southern Ural Mts are referred to the ass. Geo rivali– Pinetum sylvestris Martynenko et al. 2003 of the union Trollio europaea–Pinion sylvestris Fedorov ex Ermakov et al. 2000 and to the ass. Carici arnellii–Pinetum sylvestris Solomeshch et Martynenko in Martynenko 2009 of the union Aconito– Tilion (Martynenko et  al. 2003). Boreal herbs often occur in low abundances in these forests. Hygrophytic nitrophilous herb forests dominated by broad-leaved trees in the overstorey, or broad-leaved trees with Picea spp., or Alnus glutinosa (Querceta nitrophiliherbosa, Piceeto-Querceta nitrophiliherbosa, and Alneta glutinosae nitrophiliherbosa), are widespread in the region (Kuznetsov 1960; Evstigneev 2010; Poluyanov 2013) as well as hygrophytic forests dominated by pioneer deciduous trees and developing after cutting of the mentioned forests. All these hygrophytic forests are mainly referred to the union Alnion incanae Pawłowski, Sokołowski et Wallisch 1928 (synonym Alno–Padion Knapp 1942). In the Bryansk Polesie, such forests dominated by Alnus glutinosa are referred to the ass. Circaeo lutetianae–Alnetum glutinosum Oberd. 1953 of the union Alnion incanae (Morozova 1999; Evstigneev 2010). In the west of the region, hygrophytic broad-leaved forests are referred to the ass. Galio palustris–Quercetum

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roboris Semenishchenkov 2005 (Semenishchenkov 2009) of the union Alnion incanae; such forests dominated by Alnus glutinosa are referred to the ass. Urtico dioicae–Alnetum glutinosae Bulokhov et Solomeshch 2003 of the same union (Semenishchenkov 2009). One can refer hygrophytic forests dominated by Alnus glutinosa to the union Alnion glutinosae Malquit 1929 of the class Alnetea glutinosae. For example, in the north of the nemoral region forests dominated by Alnus glutinosa with an admixture of Picea abies in the overstorey and frequent presence of boreal herbaceous species in low abundance in the ground layer are referred to the ass. Violo palustris– Alnetum glutinosae Passarge 1971 of this union (Kuznetsov 1960; Bulokhov and Solomeshch 2003). In the southwest of the region, such forests belong to the ass. Ribo nigri–Alnetum glutinosae Sol.-Gór. 1975 (Poluyanov 2013). Hygrophytic forests dominated by Betula spp. described from the Southern Ural Mts are referred to the ass. Carici cespitosae–Betuletum pubescentis Solomeshch et Grigorjev 1992 in Martynenko et al. 2003 of the same A.g. union.

5.1.4  Section: Nemoral Swamp Forests Forests referred to this section occur on Histosols of various types, and they are usually dominated by Alnus glutinosa and Betula pubescens in the overstorey and hygrophilous herbs in the ground layer. These forests occur in valleys of rivers and streams and on watersheds or river terraces where groundwater discharges. Communities are usually referred to the class Alnetea glutinosae and they are discussed in Chap. 6. Alnus glutinosa forests dominated by hygrophilous herbs in the field layer are usually referred to the ass. Carici elongatae–Alnetum glutinosae Koch 1926 ex Tx. 1931. These forests are described from the north of the region within the Russian Plain (Fedotov 1999; Bulokhov and Solomeshch 2003; Smagin and Volkova 2012) and from the forest-steppe and steppe areas (Sokolova 2013). Swamp forests dominated by Alnus glutinosa and situated in the south of the nemoral region were also referred to the ass. Ribo nigri–Alnetum glutunosae Sol.-Gór. 1975 (Poluyanov 2013), and swamp forests dominated by Salix spp., found in the west of the region in shallow stagnant ponds located on watersheds, were referred to the ass. Salicetum pentandro-­cinereae (Almq. 1929) Pass. 1961. In karst sinkholes with strongly mineralized groundwater discharges, eutrophic swamp forests dominated by Betula pubescens are found; they were described only from the north of the region and referred to the typical (non-sphagnose) variant of the ass. Callo palustri–Betuletum pubescentis Vassilevitch 1997 that is common in the southern taiga (Smagin and Volkova 2012). Betula pubescens individuals reach up to 20 m in height. The nutrient-demanding sedges Carex elongata, C. vesicaria, C. acuta, and Scirpus sylvaticus or the hygrophilous ferns Athyrium filix-femina and Thelypteris palustris often dominate; various low-abundant forbs, such as Solanum dulcamara, Scutellaria galericulata, etc., occur. The moss layer can be well

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d­ eveloped; it is formed by the nutrient-demanding hygrophilous mosses Calliergon cordifolium or Plagiomnium medium. It is noteworthy that recently published data (Gornova 2014) show that Picea abies can co-dominate in the overstorey together with Alnus glutinosa in swamps located in zander landscapes. Tall herb Picea abies swamp forests are described from fens in the Bryansk Polesie. High species diversity (on average 62 vascular species per 100 m2) is a feature of these forests. Various microsites caused by treefalls with uprooting together with sedge tussocks, hillocks created by Alnus glutinosa roots, and flooring formed by the surface roots of Picea abies maintain the high species diversity of these forests (Kharlampieva and Evstigneev 2013).

5.1.5  Section: Sphagnum Forests Forests located on oligotrophic and mesotrophic bogs mainly occur in the north of the nemoral region, and they are only described from the Russian Plain. These forests grow in depressions on watersheds or river terraces, and they are very similar to forests of the sphagnum section described from the hemiboreal region (Fedotov 1999; Morozova 1999; Bulokhov and Solomeshch 2003; Smagin and Volkova 2012). The moss layer is dominated by Sphagnum spp.; Polytrichum commune can co-­dominate in oligotrophic forests and Calliergon spp. and Plagiomnium spp. in mesotrophic ones. Oligotrophic communities with rare individuals of Pinus sylvestris belong to the ass. Vaccinio uliginosi–Pinetum sylvestris Kleist 1929 em. Mat. 1962 and the ass. Sphagno angustifolii–Pinetum sylvestris Smagin 2000 (Bulokhov and Solomeshch 2003; Smagin and Volkova 2012). The field layer is dominated by bog dwarf shrubs, such as Ledum palustre, Oxycoccus palustris, Chamaedaphne calyculata, and Andromeda polifolia, and bog sedges, such as Eriophorum vaginatum, Carex lasiocarpa, and C. globularis. Mesotrophic forests are dominated by Pinus sylvestris, Betula pubescens, or Alnus glutinosa. Oligo-mesotrophic forests dominated by Pinus sylvestris with Betula pubescens or only Betula pubescens belong to the ass. Vaccinio uliginosi–Betuletum pubescentis Libbert 1933 (Bulokhov and Solomeshch 2003). The dwarf shrubs Vaccinium myrtillus and V. vitis-idaea and the boreal grass Molinia caerulea often occur in the ground layer together with the mentioned bog species. Mesotrophic Betula pubescens forests belong to the ass. Sphagno angustifolii–Betuletum pubescentis Vassilevitch 1997 (Smagin and Volkova 2012); the hygrophilous species Carex rostrata and Menyanthes trifoliata are common there. Mesotrophic forests dominated by Alnus glutinosa in the overstorey and Sphagnum spp. in the bottom layer belong to the ass. Sphagno squarrosi–Alnetum glutinosae Sol.-Gorn. 1975. The hygrophilous grass Phragmites communis often dominates the field layer; Carex cinerea, C. rostrata, and Naumburgia thyrsiflora often occur (Morozova 1999). Mesotrophic forests of similar structure, but dominated by Betula pubescens, belong to the ass. Callo palustri–Betuletum pubescentis Vassilevitch 1997 (Smagin and Volkova 2012).

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5.1.6  Conclusion The forest communities of the nemoral forest region in European Russia show many combinations in tree species composition and dominating herbaceous species. These forests not only contain the highest number of plant species of all Russian forest regions, due to a favorable temperature regime in the nemoral region, but also experience the highest variety in possible land-use practices. In this chapter, we have mainly described mesophytic and more floristically diverse variants of the main forest communities, based on dominant ecological-coenotic and on floristic approaches. These variants often are modified as a result of human impacts and, near their edges, as a result of “ecotonal effects”, which are common in the nemoral forest region because of the high level of fragmentation of the forest cover. Mesophilous meadow species as well as xeromesophilous herbaceous species persist in fragmented forests with long forest edges and maintain a high forest diversity. In general, it can be said that it is typical of the nemoral region that while it has a low proportion of forested land, it maintains a high level of vegetation diversity.

5.2  F  eatures of the Historical Land Use in the Nemoral Region The nemoral forest region knows a long history of cultural and economic development. The history of the northern area, which still has preserved broad-leaved forests, is closely related to the history of the southern areas, which had forests in the past but now consist of steppe and forest-steppe areas. Palaeoecological data show that in the area of the nemoral forest region, the broad-leaved tree species Quercus robur, Ulmus spp., Acer spp., Fraxinus excelsior, and Tilia cordata were most widespread around 5000–3200  years BP; this was shown for the Central Russian Upland (Serebryannaya 1981; Klimanov and Serebryannaya 1986; Novenko et al. 2009, 2012, 2015) as well as for the Middle Volga Upland (Blagoveshchenskaya 2009). The causes of forest devastation over large areas in Eastern Europe have been researched for a long time (see reviews by Milkov 1950, 1952; Komarov 1951; Smirnova 1994, etc.). The opinion that the modern vegetation of the steppe region is a secondary phenomenon resulting from the eradication of forests by man was expressed in the beginning of the past century, in the early works by Sukachev (1902), Krylov (1915), and Keller (1921, 1923) (cited according to Komarov 1951). A thorough analysis of the development of steppe vegetation in the Holocene led Komarov (1951) to the conclusion that the entire history of the Holocene steppes was a history of interaction of herders and farmers with what initially were forest

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and forest–steppe landscapes. According to archaeological data (Gorodtsov 1925, 1927; Krasnov 1971; Merpert 1974), the part of the Eastern Europe that was occupied by temperate forests in the Middle Holocene and now belongs to the steppe area started to be actively developed during the Bronze Age. The beginning of the formation of the most ancient cultures there, which were the Cucuteni-Trypillian and the Yamnaya cultures, is dated at around 6000 years ago. According to Armand’s assessment (1955), the population density of the Cucuteni-Trypillian culture reached up to 30–35 people per km2. The main occupation of the people were cattle breeding and partly farming, as well as smelting of copper for tools which required large amounts of wood. Along with pasturing, fires (in grassland as well as forest) were another factor playing a leading role in the transformation of nature in Europe. Broad-leaved forests are usually considered resistant to fires. Meanwhile, however, many authors point out that this is not the case when the purpose of the fire is specifically to burn the forest (see Simmons 1969, 1975, 1996; Edwards 1979, cited according to Moore 2000; Innes and Simmons 2000). All over Europe, fires played an important role in forming open landscapes and thus in maintaining the populations of Quercus spp., Pinus spp., Corylus spp., and many other plant species (Svenning 2002; Bradshawa et  al. 2003; Lindbladha et  al. 2003). The beginning of mass forest burnings in Europe is dated at the transition from the Mesolithic to the Neolithic era, i.e., also about 6000 years BP. About 4000 years ago, farming and cattle breeding had already spread into the more northern areas, in the modern nemoral forest region in Eastern Europe (Krasnov 1971). The basis of the economy of the Catacomb (4000–3600 years BP) and later Srubnaya (3600–3100 years BP) cultures, which were spread over the present-day forest-steppe and temperate forest areas, was cattle-breeding (Merpert 1974). The osteological material of that time contains fewer findings of bones of wild ungulates (Bison bonasus, Bos primigenius, Equus gmelini, etc.) as compared to the material of older times, and the proportion of livestock bones increases (Tsalkin 1956). Also pollen of cereals shows up in pollen spectra of that time (Krupenina 1973). The population was settled and, apart from cattle breeding and farming, was occupied by working on metal, stone, bone, and wood. Thus, during the process of the development of cattle-breeding and farming in the south of Eastern Europe, the tribes of the Cucuteni-Trypillian, Yamnaya, Catacomb, and Srubnaya cultures “shifted” the boundary of the forest-steppe from the coasts of the Black Sea and the Azov Sea, from the Lower Volga and Southern Ural to the north and northwest. Analysis of palaeobotanical and archaeological data shows that in the 3000–3500 years from the beginning of the active colonization of the northern coast of the Black Sea (6000–5500 years ago) till the time of the Scythian tribes, the southern boundary of the forested area shifted between 400 and 600 km to the north (Smirnova 2004). In the time of Herodotus (2500 years ago), Scythia was already woodless.

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Comparison of the map of present vegetation and the map of the distribution of Bronze Age culture shows an almost complete overlap of the northern boundaries of the Srubnaya culture and the modern steppe region (Komarov 1951; Smirnova 1994). This overlap probably is not due to the fact that the people of that culture settled in the steppe, but because the steppe itself was formed as a result of the economic activity of tribes of the Srubnaya and other cultures. It is often believed that shifts in the cultural economic setup of a local population of a certain area or its replacement by another culture with a different cultural economic setup generally occurs as a consequence of alterations in the natural environment. Yet in many cases, human activities cause the very changes in the natural environment. Starting with the Iron Age, the distribution of the broad-leaved trees Quercus robur, Ulmus spp., Acer spp., Fraxinus excelsior, and Tilia cordata was notably declining, and that obviously had anthropogenic causes. Simultaneously, the percentage of Betula spp., Pinus sylvestris, and cereal pollen in pollen diagrams, as well as the content of charcoal, was increasing (Serebryannaya 1981; Klimanov and Serebryannaya 1986; Novenko et  al. 2015). The anthropogenic impact on nature was not synchronized in different parts of the nemoral region. The beginning of large-scale anthropogenic changes falls into the period between 2500 and 1700 years ago. In the period from the Iron Age to the early Middle Ages, the northern and southern parts of the nemoral region increasingly differed because of their different economic use. The present-day area of broad-leaved forests and the northern part of the forest-steppe area experienced an intensive development of farming. Arable farming was partly introduced there not later than in the first centuries AD.  However, its widespread within the area of nemoral forests as well as in the area of hemiboreal forests (Sect. 4.2) was shown for the period of Slavic colonization, which occurred from the sixth to eighth centuries (Istoriya krestyanstva v SSSR… 1987a, b; Krasnov 1987). The period of “the great Russian ploughing up” is dated as from the eleventh to thirteenth centuries (Kulpin and Pantin 1993). As in other regions, expansion of arable lands under insufficient fertilization led to the impoverishment and degradation of the soils. As a result, farmers had to abandon their farms after some time, and a hybrid system of agriculture, combining the three-field system with fallow farming and elements of a slash-and-burn system, was developed (Milov 1998). The agricultural system developed by the middle of the 2nd millenium has existed without any substantial alterations till the nineteenth and twentieth centuries. This also held true for the tools and techniques of wood working, which were very similar and sometimes analogous to those used in the peasant’s domestic industry till the nineteenth and twentieth centuries (Levashova 1956). Specialization of lands gradually took place; exploitation of lands became rather strictly related to their landscape position, as can be seen up to the present time. The watersheds were mostly occupied by arable and fallow fields; hayfields were situated in the floodplains, at the bottom of ravines and in gullies. In the southern forest-steppe areas bordering the steppe, a “wild field” was formed. That area was mainly controlled by nomadic cattle-breeding tribes, among which the Cumans have played an important role for a long time. It is unknown

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what part of the forest-steppe lands was occupied by farms, forests, meadows, and steppes at that time: there is no direct historical data about this, just as there is no information about how many nomads lived in that part of the forest steppe before the Mongol invasion. The data presented by Kirikov (1979) allow one to suppose that the nomadic population on the southern forest-steppe area was not particularly high before the invasion of Mongols in the thirteenth century: the main nomadic camps were situated in more southern regions, in the steppe region. The nemoral region kept a predominantly forest character, this being also indicated by the frequent findings of bones of wild animals (such as Sus scrofa, Cervus elaphus, Alces alces, and Capreolus capreolus) in the archaeological excavations on the territories of the Dnieper-Don and the Central Chernozem forest-steppe areas (Kirikov 1979). With the advent of the Mongols in the middle of the thirteenth century, forest-­ steppe and steppe areas were not abandoned; they were used both for farming (serving as a “bread basket” of the Khans’ armies) and for pasturing and nomad camping. But nomadic camps steadily spread northward during fourteenth and fifteenth centuries (Kostenchuk and Tyuryukanov 1996; Kulpin 2009). Thus, in the fourteenth century, the northern border of Tatar summer camps run along the line from the upper reaches of the Seversky Donets River and the Tikhaya Sosna River to the lower reaches of the Medveditsa River, i.e., within the steppe region; in the 1470s, the Golden Horde nomads almost every year roamed near the southern border of the state of Moscow (along the line Ryazan–Tula) (Kirikov 1979), i.e., in the southern part of the broad-leaved forest region. Hundreds of thousands of sheep and goats destroyed the forest vegetation, forests were replaced by meadows, the meadow vegetation became more xerophytic, and Festuca valesiaca spread farther to the north, in the region of the nemoral forests (Smirnova 1994). In the fifteenth and sixteenth centuries, the density of the nomad population in the Eastern European steppe grew too high, and the limited amount of resources that steppe could provide to support their livestock became insufficient. An uncompromising struggle for pasturing resources began, and pastures were expanded into the forest-steppe area (Kulpin 2009). At that time, the winter camps of the Golden Horde nomads were sometimes situated more to the north than the summer camps of the Cumans. According to the Nikon Chronicle, in the fall of 1444, the steppe to the south of Ryazan was burnt over such a wide area that the Golden Horde prince Mustafa had to move his winter camp into Ryazan (Kulpin 2009). Sometimes, the Golden Horde nomads set their winter camps even further north than Belgorod. It is known that in 1501 the Crimean Khan Mengli I Girey learned that the Khan of the Golden Horde Ahmed was going to spend the winter in the lower reaches of the Seym River and in the vicinity of Belgorod, so he ordered to start fires to destroy the places suitable for camping (Kulpin 2009). As far back as the thirteenth and fourteenth centuries, along the line Ryazan– Tula–Kozelsk, a defensive zone consisting of natural mature forests with an Abatis line was being formed along the boundary separating the lands of the Slavic farmers and the territories controlled by the nomads. In the sixteenth century, during the military confrontation between Moscow State and the Crimean Khanate, the continuous defensive belt beyond the Oka River (“Zaokskaya Zasechnaya Cherta” in

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Russian) was built by the Russians with a total length exceeding 600  km (Ponomarenko et al. 1993). The belt consisted of areas of mature forests from 3 to 6  km wide, rivers, and Abatis lines of 10–20  m wide which were constructed of felled trees. Following the Zaokskaya Cherta, other defensive belts were later constructed farther to the south and to the east (Yakovlev 1916). It was important that these forests were excluded from economic exploitation and were preserved. In the course of the following centuries, these forests were partly included into the list of state forests, and some of them became state nature reserves or national parks in the twentieth century: the Kaluzhskie Zaseki Reserve (see Sect. 5.3), the Ugra National Park, the Belogorye Reserve, and others. Under the protection of their defensive belts, an active Russian colonization of the forest-steppe, and later the steppe region, began. In the basin of the upper Don River, large-scale ploughing of lands started at the end of the sixteenth century. More than 60% of the suitable areas were ploughed up within the first 120 years, but the area of arable lands increased less than 20% during the next 200 years (Panin et al. 1997; cited according to Ivanova et al. 2005). After the severe economic and demographic crises at the beginning of the seventeenth century, the growth of the Russian population became fast and almost persistent. In areas to the south of the Abatis belt beyond the Oka River, the territories were recolonized and the lands were allocated to settlers; the allocation was done under the presumption that these were permanent arable lands, mainly exploited on the basis of the three-field agricultural system (Ofman et  al. 1998). Toward the end of the seventeenth century, 40–60% of the land had been ploughed up in the upper reaches of the Don and Oka rivers and not more than 20% in the more southern provinces (Ivanova et al. 2005). However, the elimination of forests for arable lands continued, and by the end of the eighteenth century, the watersheds in many provinces within the nemoral region had been ploughed up to their limits: only forests under the special protection of the state and on lands of some landowners were preserved. On the whole, in the 1770s–1780s, the forest coverage in some provinces in the northern part of the nemoral region reached 80%, but by 1840, it had decreased to 25–35% (Tsvetkov 1957) (Fig. 5.1). In the nineteenth century, the expansion of arable lands occurred mostly at the expense of lands inconvenient for ploughing, such as sides of gullies and river valleys (Fig. 5.2). Exploitation of these latter sites, in turn, resulted in a sharp intensification of erosion processes and increased alluviation in riverbeds. This led to the disappearance of small watercourses and shallowing of large rivers as was observed in the central provinces of the European part of Russia at the end of nineteenth century. For example, in the Tula province, most of the small rivers and streams indicated on the maps of 1840–1850 were absent at the end of the nineteenth century (Ivanova et al. 2005). The forests of the nemoral region were intensively devastated not only due to ploughing of the land but also due to cutting and logging. There constantly was a shortage of both timber and fire wood (these types of forest exploitation begin to appear in historical documents from the sixteenth century). In the beginning of the seventeenth century, the industrial development began and that also increased the demand for wood. For example, a lot of small potash- and saltpeter-producing

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Fig. 5.1  M. Klodt’s painting “On the arable land” [Na pashne], 1872. Large continuous areas of arable lands were widespread in the nemoral forest region of European Russia from the eighteenth till the middle of the twentieth centuries

Fig. 5.2  M. Shishkin’s painting “Polesie”, 1884. Here is the typical combination of Pinus sylvestris forests with agricultural lands on sandy soils. In the foreground, the large proportion of weeds in the cereal crops can be seen

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f­actories were created in the nemoral region and they needed broad-leaved trees. The charcoal burning was carried out right in the forests, in specially constructed pits. From there, the wood ash was then transported to the factories. In the second half of the seventeenth century, the annual export of Russian potash amounted to 2.5–3 thousand tons (Milkov 1950) and later it gradually decreased. The rapid devastation of forests caused a reaction from the rulers, because forests had significant defensive value. In 1649 Aleksey Mikhailovich declared a classification of forest lands into various categories with a special emphasis on the reserved Abatis forests. In 1659 it was prohibited to establish new factories in forests within and near the Abatis belts without a special monarchic permission. It is interesting that among other things harm to beekeeping was specified as the reason for the ban: broad-leaved forests had long been the main region of apiculture, and its products, such as honey and wax, were important export goods. However, the ban was far from being strictly enforced: it is known that peasants “paved woodcutting paths,” cut trees and cleared plots, and even settled in the Abatis forests (Yakovlev 1916; Ponomarenko et al. 1992). At the beginning of the eighteenth century, Peter the Great issued a few decrees which restricted the use of forests. Quercus robur, Ulmus spp., Acer spp., Fraxinus excelsior, Abies sibirica, and mast individuals of Pinus sylvestris were decreed as protected trees for their use in shipbuilding and other military needs of the Russian State. In 1703 cutting of a single individual tree (except Quercus robur) entailed a 10-ruble fine, and cutting of one individual tree of Quercus robur or a large number of other protected trees was punishable by death penalty. In 1712 the punishment was alleviated: the death penalty was replaced by penal servitude. Milkov (1956) assumed that the absence of Fraxinus excelsior in one of the cutting ban decrees resulted in the rapid elimination of this species over the large areas. Huge areas of Quercus robur forests in the basins of the Oka and Don rivers were cut at the turn of the seventeenth and eighteenth centuries for the needs of fleet building (Milkov 1956); the cut trees were transported by the Don River to Azov. At the end of the eighteenth century, the cut trees, including trees from the basin of the Oka River, were transported by the Desna and Dnieper rivers to Kherson and Nikolaev. For a long time, the main kind of cuttings had been selective cuttings of different intensity. They have led to a gradual change in tree species composition and the widespread increase in the proportion of Populus tremula. Withal, in many places after selective cutting for timber, devastating clear-cutting was carried out. At that time, many forests that previously served as a part of the defensive belts were cut. In the nemoral as well as in the hemiboreal region, the volume of cuttings for the needs of industry, steamship companies, and later railroads increased significantly in the first half of the eighteenth century and the global forest devastation took place after the reform of 1861 (Arnold 1895; Tsvetkov 1957, etc.). Apart from the cuttings themselves, brushwood gathering and cutting of dead trees which were practiced in all forests (including state forests) had a large impact on forest ecosystems through the removal of biomass. Another permanent factor affecting the composition and structure of forests was forest pasturing. There was a lack of forest-cleared lands, and the cleared patches were mainly occupied by farms

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Fig. 5.3  M. Shishkin’s painting “Oak grove” [Dubovaya roshcha], 1887. It shows a typical old-­ growth Quercus robur forest without undergrowth and shrub layer, lacking as a result of forest pasturing

and hayfields, and as a result, the forest was the main place where livestock was pastured during the entire vegetation period (Fig. 5.3). Both private and state forests were used for pasturing; even plots in reserved Abatis forests were divided between villages to be used as pastures. At the turn of the nineteenth and twentieth centuries, many state forests were rented out for pasturing and haymaking and that became the most profitable use of forests (Otchet… 1905). Peasants also practiced the gathering of forest litter which they used for bedding in cattle sheds as well as for stocking up for compost. The use of forest litter in agriculture has long been known in Europe (Arnold 1895; Walter 1973). According to Gomilevsky (1897), Russian peasants had long used heather, moss, peat, marsh grasses, forest litter, and branches of coniferous trees (predominantly Picea spp. and Abies sibirica) for bedding in stalls. Stocking up with leaves and branches of Ulmus spp., Betula spp., Tilia cordata, Acer spp., and other trees for bedding and feeding cattle was carried out from the middle of May to the middle of June; it was done simultaneously with barking individuals of Tilia cordata for bast. Leaves and bark of Quercus robur were stocked in spring. These practices were spread in peasant farms all over European Russia during the eighteenth and nineteenth centuries (Skvortsov 1865; Gomilevsky 1897). Skvortsov (1865) considered gathering forest litter as the most important “supplementary use of forest.” Numerous stockings of branch fodder for winter might have played an important role in the reduction of the areas of distribution of trees such as Ulmus spp., Abies sibirica, etc. (Komarov 1951). The high density of the peasant population and the high diversity of trees in

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the nemoral forest region determined an advanced level of forest-specific crafts: wood was intensively used for making tableware, barrels, carts, sledges, and a great variety of other goods. Farming usually generated only a third of the peasant’s incomes needed for their living; other revenue came from various crafts. In the Kozelsk province, for example, the profit that peasants had from their crafts amounted to 65% of the total money income of the peasants (Statisticheskoe opisanie… 1898). During the eighteenth and nineteenth centuries, rulers of the Russian Empire repeatedly tried to regulate the use of forests and to implement forest management regarding cuttings and forest preservation. The majority of decrees and practical measures were mainly directed at the forests in the nemoral region. The reasons were obvious: the forests that were strategically important for defense and industry and the rates of their devastation were menacing. In 1722 Peter the Great established the post of Überwaldmeister (head forester in Russia) to manage forest reserves and issued a special instruction which prescribed to make an inventory of forests. In 1723 a new Waldmeister instruction increased the number of forest officers. In 1729 Peter II ordered to use for state needs not only state forests but also to buy high-quality Quercus robur forests from landlords in order to encourage them to plant and protect this species. In 1732 Anna Ioannovna issued a special statute prescribing sowing and planting of forests. Instructions were made of how to plant and protect new forests. To implement the statute, forstmeisters were invited from Germany; apart from planting, care, and protecting trees, forstmeisters were also charged with teaching Russian apprentices “the forest trade.” The supervision of forests has worsened since 1762, when the manifesto by Peter III granted the freedom of the nobility and the Waldmeister office ceased to exist (Arnold 1895). Until that time, it was a duty of the nobility to be heads of forest guards and they did it for free. In 1798 Pavel I established a special department which was later called the Forest Department. An Überforstmeister (head forester) was appointed in each province with a staff of forstmeisters (foresters), forest apprentices, and forest wardens. Their duties were to protect and cultivate forests (Arnold 1895; Tsvetkov 1957). The first documented plantings of Quercus robur in the Tula Abatis forests are dated at 1798. In 1802 the Emperor Alexander I established ministries and ordered to establish schools for teaching foresters (Arnold 1895). In 1803 a forestry school for 20 apprentices was opened in Tsarskoe Selo near St. Petersburg; in 1804 a forestry institute for 30 students was opened near Kozelsk, in Kaluga province, in a forest inside the former Abatis belt beyond the Oka River (in the Zaokskaya Zasechnaya Cherta). In 1802 the system of guarding forests was changed. In the seventeenth and eighteenth centuries, local people were temporarily selected to guard forests and the system did not work well. As from 1802, strangers, with a salary, were appointed for the guarding and it became more effective (Popov 1937). In 1802, 80 and 40 former soldiers and sailors were appointed as forest guards in the Kaluga and Tula provinces, respectively (Arnold 1895). In 1803, 68 staff forest wardens and 10 horse rangers were allocated in addition to 212 already permanently appointed wardens in

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the Tula and Kaluga Abatis forests, in the Shipov and Tellerman forests both in the Voronezh province, in the Polninsky Forest in the Orel province, and in the PogonnoLosiniy Island near Moscow (Tsvetkov 1957). From 1700 till 1840, forests were mainly planted on woodless areas (Arnold 1895; Gomilevsky 1897; Popov 1937; Tsvetkov 1957). In the 1840s, the inventory of state forests began; it included the description of forests, their division into blocks separated by cut lines, and the development of plans for forest management. In 1843 an instruction on the rules of forest description was published and in 1845 the first forest inventory and forest cultivation instructions were issued. Forest planting has actively begun on cutting plots since that time. Also in 1845, selling of wood by auction began, and it became widespread after 1854 and significantly increased the income from state forests and, correspondingly, increased funds for forest restoration. In 1870 rules regulating the renting of cutting plots and forest glades in state forests for temporary agricultural use were adopted (Nekhoroshev 1903). Peasants cleared and often stubbed cutting areas for the right to freely use the areas for cropping of cereals for 2–4 years. Sometimes peasants also participated in planting and/ or cultivation of trees at the logging sites in order to allow the use of cutting areas (Zhukov 1949). The forest protection law of 1888 decreased the rates of forest devastation and effectively preserved water protection forests from cutting. The law of 1899 about prepayment for industrial cuttings provided funds for the regular planting of trees at the logging sites. The data on forest planting from the end of the nineteenth to the beginning of the twentieth centuries indicate that those plantings were huge. And that, together with the other kinds of human activity, largely determined the species composition of modern forests in the nemoral region (Tsvetkov 1957; Rechan et al. 1993; Bobrovsky 2002). Presently, in this region of European Russia, the most mature and old stands dominated by Quercus robur, Pinus sylvestris, and Picea abies are old planted forests and most of them were planted between 1899 and 1914. The fact that those old forests were planted easily explains the massive dying off and decay of the trees at the present time. After the February and then the October revolutions of 1917, forest use became practically uncontrolled: cuttings and other types of forest use were not restricted by any rules, and there was no concern about preservation of forests and their renewal whatsoever. Selective cuttings became widespread again; only small individuals and non-valuable tree species remained in forests. By 1930 about a quarter of the forests in the western part of the nemoral region in European Russia had been turned into young cutting sites and waste plots. The situation somewhat improved after 1936, when the Main Department of Forest Protection and Cultivation was established. A law on water protection zones was adopted; cutting became substantially restricted in many riparian Quercus robur forests. During the Second World War, forest use was irregular. During the war, the rural population was significantly reduced in the nemoral forest region and many settlements were wiped out. After the war, large areas of agricultural lands were abandoned and many of them were planted with Pinus sylvestris and Picea abies; this

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was done during the first postwar years. Quercus robur forests were intensively exploited at that time: hardwoods were cut for parquet production, aircraft needs, etc. Before the 1960s, cuttings were mostly carried out during the winter and horses were used for skidding. The use of tractors has begun since the 1960s (Nabatov and Turkin 1968). Until the middle of the 1980s, an active supplementary use of forests continued: it was first of all forest pasturing, removal of snags, gathering of dead woods. During 1985–1989, a social-economic crisis strokes the country. Among the consequences of this were another reduction of the rural population, the abandonment of many villages and settlements and the abandonment of large areas of ­agricultural lands, the cessation of forest pasturing, and many other kinds of supplementary forest use.

5.2.1  Conclusion Presently, there are practically no large areas of undisturbed broad-leaved forests in the nemoral forest region. Old-growth forests are mainly located in nature reserves and national parks. The largest tracts of these forests occur in areas that belonged to the defensive belts of Moscow State in the sixteenth and seventeenth centuries. The transformation of flora and fauna in the course of the economic development of the nemoral region is well reviewed (Milkov 1950, 1956; Turchanovich 1950; Komarov 1951; Tsvetkov 1957; Kurnaev 1980; Smirnova 1994). The general features of the ecosystem history in the region consisted of a widespread occurrence since ancient times of slash-and-burn agriculture, forest pasturing, and cuttings; it also consisted of multiple alterations in land-use practices in  local areas that were determined by both land-use technology and social-economic causes. The clearest divergence between the ways of forest development in the northern and southern parts of the nemoral region was probably launched from the middle to the end of the 1st millennium AD and later continued. Arable farming was widespread in the northern part of the region since that time; areas of forests and arable fields alternated there. Forest tracts were preserved or formed anew along the southern border of this part; the forests served as a shield against steppe nomads. At different periods of the twentieth century, many agricultural lands were abandoned and became forest lands. Nowadays, about 25% of the northern part of the nemoral region is covered by broad-leaved deciduous forests. The southern part of the nemoral region had remained a “wild field” until the seventeenth and eighteenth centuries with pasturing and burning having led to a significant decrease of forested areas. As from then, these areas were mainly turned into arable lands and rarely into meadows. Nowadays it is a forest-poor forest-steppe area.

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5.3  O  ld-Growth Nemoral Forests and Vegetation Dynamics in the Kaluzhskie Zaseki State Nature Reserve The Kaluzhskie Zaseki State Nature Reserve (number 31 in Fig. 2.1) is situated in the southeast of the Kaluga region, in the territory adjacent to the Orel and Tula regions. The geographical coordinates of the Reserve range from 53.5 to 53.9°N and from 35.6 to 35.9°E. The Reserve was established in 1992 due to the presence of unique old-growth broad-leaved forests which was mostly undisturbed by cutting and ploughing (Smirnova 1994). The Reserve consists of two separate parts which are 12 km apart. The total area of the Reserve is 185 km2: the northern part (the Ulyanovo forestry unit) measures 67 km2 and the southern part 118 km2 (with the Yagodnoe forestry unit 60% and the Leninskoe forestry unit 40% of the southern part). The Reserve is situated in the northwest of the Central Russian Upland, in the basin of the upper reaches of the Oka River, at the watershed between the Oka and the Vytebet rivers (the latter is a tributary of the second order of the Oka River), on gently sloping upland mostly at elevations between 150 and 250  m asl with the highest point at 275 m asl (Popadyuk et al. 1999). The erosional relief is densely dissected by ravines, gullies, and streams; ravines reach depths of more than 30 m; about 20 small rivers and streams run through the area. Fluvioglacial sands prevail in the Reserve area except in the northern part of the Yagodnoe forestry unit and the southeastern part of the Ulyanovo forestry unit where loams dominate. The valley of the Vytebet River is formed by modern and ancient alluvium. The average annual temperature is 4.5°C; the average annual precipitation is 700  mm (Shekhtman 1964, 1967). The maximal precipitation occurs in July and August; the lowest in December and January. The frost-free season is about 140 days and the vegetation season (with the average daily temperature higher than 5°C) is about 180 days.

5.3.1  History of the Reserve Area “Kaluzhskie Zaseki” (“Kaluga Abatis belt”) is a name that has been used since the eighteenth century to designate the part of the Kaluga province included into the Abatis belt beyond the Oka River of the Moscow State of the sixteenth and seventeenth centuries (Fig.  5.4). The Reserve contains remaining fragments of Abatis forests (the Stolpitskaya and Dubinskaya sections of the Kozelsk Abatis belt); the other remaining forests of this Abatis belt in the Kaluga region are included into the Ugra National Park (number 30 in Fig. 2.1). The territory of the upper reaches of the Oka River is known to be settled several millenia ago, with the slash-and-burn agriculture being widespread since the end of

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the 3rd millenium B.C. (Krasnov 1971; Kraynov 1972). The basin of the Upper Oka River was colonized by the Slavs in the eighth and ninth centuries. By the twelfth and thirteenth centuries, the watersheds were almost completely covered with farms of the three-field agricultural system (Istoriya krestyanstva v SSSR… 1987b). As from the end of the fifteenth century, sections of the future Abatis belt beyond the Oka River (“Zaokskaya Abatis belt”) started to be developed in the area that now belongs to the Reserve (see Sect. 5.2). The Abatis belt was finished in 1563–1566. 1566 was mentioned in the Chronicles as the year when large-­scale works were completed in the Zaokskaya Abatis belt, and the results were inspected by Ivan IV personally (Yakovlev 1916; Bobrovsky 2002). The Zaokskaya Abatis belt was detailedly mapped by Yakovlev (1916), who used guard books of the belt and some other documents from the seventeenth century. Fragments of the belt have been preserved till the present days (see Ponomarenko et al. 1993; Popadyuk et al. 1999; Bobrovsky 2002). The Zaokskaya Abatis belt lost its defensive value toward the end of the seventeenth century. Potash and tar factories were built in the Abatis forests and partial cuttings, plowing, and pasturing occurred there (Bobrovsky 2002; Tsvetkov 1957). Nevertheless, guards were dispatched along the belt till the end of the seventeenth century; the Abatis forests were identified as a separate category, and on the whole, protection of the forests continued (Wrangel 1841). Besides, the

Fig. 5.4  Preserved forest tracts in the area of the former Zaokskaya Abatis belt (According to Kurnaev 1980 with modifications)

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Fig. 5.5  Schematic map of old Quercus robur plantations in the Kaluzhskie Zaseki Reserve in areas of the Ulyanovo (a) and Yagodnoe (b) forestry units: 1 before 1790; 2 between 1790 and 1830; 3 between 1830 and 1880 and 4 between 1890 and 1914

region of the Abatis forests was a traditional place of wild honey farming; it is known that on the area of the modern Reserve, to the west of Kireykovo village, there was a large Monarchic honey farming forest (Bobrovsky 2002). In 1712, thinking about the economic support for his military politics, Peter the Great founded the Tula Armory and the Bryansk Admiralty. In 1737 and 1739, he issued decrees which transferred a number of Abatis forests, including forests of the Kaluga and Tula Abatis belts, under the authority of the Armory Office of the Tula factory. This event chiefly determined the history of those forests in the eighteenth and nineteenth centuries. A strict protection of the forests that, however, allowed for a moderate exploitation was the consequence of that event. In 1732, Anna Ioanovna issued an instruction about the cultivation of new forests for the needs of the fleet (Arnold 1895). Probably the oldest preserved cultures of Quercus robur in the Kaluzhskie Zaseki Reserve date from that time (Fig. 5.5.) In 1772 and 1774, in the Bolkhov and Kozelsk districts of Kaluga province, a general land survey was conducted and documents about that are preserved in the Russian state archives. From the economic comments to the plans of the general land survey, one can have an idea about the state of the Abatis belts at that time. A part of the Kaluga Abatis belt, which is now within the Reserve (the Stolpitskaya and Dubenskaya sections of the Kozelsk Abatis belt), was forested and belonged to the Tula factory; another part, outside the boundaries of the Reserve, was sold to private owners. By the end of the nineteenth century, those private territories were entirely deforested and partially ploughed; forests were transferred to the category

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of firewood. At the Kaluga side of the Abatis belt, fields were scattered inside forests on watersheds; they were isolated and measured 150 dessiatinas (app. 1640  m2) each; at the Orel side, there was merely open space and only ravines were covered by firewood forests (Smirnova 1994). By the beginning of the nineteenth century, the Kaluga province became one of the centers of forestry, being an example for the neighboring provinces (Arnold 1895; Orlov 1895). In 1845, the first forest inventory was conducted in the Kozelsk Abatis belt. The division of the forests into blocks separated by cut lines and their numerations have been preserved almost without changes until now. In 1846, the forests of the Kaluga province were divided into two districts and ten forestry units. The forests of the former Kozelsk Abatis belt amounted to 40% of the state forests of the province (Report of the Kaluga Chamber for Forest Management of 1846, cit. on Bobrovsky 2003). Since that time, trees were planted in the Abatis forests almost every year (Popov 1937). As usual, most of the plantings were performed on deforested areas, on arable lands, and on meadows (Tursky 1884). In addition, renewal of Quercus robur plantations was secured in the logging spots by leaving seed trees and by seeding, or rarer planting, of Quercus robur and Picea abies seedlings. There are preserved registers of seeding and planting of forests in the period from 1844 to 1852 in Central Russia (Bobrovsky 2003), according to which more than 1.6 km2 were forested in the state forests of Kaluga province between 1849 and 1852. The plantings continued in 1853–1857 (Arnold 1891). After the reform of 1861, during the extensive forest devastation, the Kozelsk Abatis forests luckily avoided a total cut down: by landowners, because these forests were state forests; by the state, since the forests fell under the authority of the Tula armory, not the government; and the Tula armory that practically did not exploit forests (cit. on Gamel 1826). After the forest protection law of 1888 and the law of 1899 about prepayment for industrial cuttings (the tax was used for forest planting) and until the First World War, trees were planted in Central Russia over truly huge areas (Zhukov 1949; Morozov 1950; Rechan et al. 1993). However, cuttings were intensive and large as well. Industrial clear-cuts were performed on rented sites. After cutting, most of the logged sites were reforested; there were also sanitary cuttings conducted regularly from 1890s to 1900s (Popov 1960). In the Kozelsk district, the interval between clear-cuts on the same place varied from 30 to 120 years in the state forests and from 10 to 15 years in the peasant forests (Statisticheskoe opisanie et al. 1898). Thus, by 1914, most of the state forests within the Kaluga Abatis belt consisted of Quercus robur plantations (from young to overmature stands) created at different times (Fig. 5.5) with the purpose of obtaining high-quality commercial timber. The rest of the stands were dominated by Populus tremula developed as a result of multiple clear-cuts of broad-leaved forest. In 1914, the planting and nursing of Quercus robur stopped. Cuttings “for war needs” during the First World War did not practically affect the Abatis forests, yet, as from 1917, cuttings became very irregular: selective felling prevailed, but some-

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times clear-cuts on small plots with good soil occurred with the purpose of clearing and transferring lands into other land-use categories (Guman 1926). After those cuttings, Populus tremula and shade-tolerant broad-leaved trees renewed from their stumps, and presently, those trees are mature and overmature Populus tremula and broad-leaved trees of vegetative origin. In 1925, the Soviet state for the first time attempted to regulate forest management: the Kozelsk Forestry unit (in which the forests of the modern Reserve were included) was one of the first to be established and inventoried. However, only in 1937, irregular cuttings were stopped and forest cultivation was resumed; Quercus robur was planted on small areas within the Abatis forests. During the Second World War, forest exploitation became irregular again; the largest-scale cuttings in the Abatis forests occurred in 1941–1943, when the frontlines run along the right banks of the Vytebet and Zhizdra rivers. During the wartime, the rural population of the region was substantially reduced. Many agricultural lands were abandoned and a large part of them was reforested with Pinus sylvestris and Picea abies plantings just after the war. By the 1970s, the forest covered more area in the region than at the end of the nineteenth century. In 1970–1980, the planting of Picea abies was especially intensive: they were conducted on logging sites as well as under the canopy of broad-leaved forest. Supplementary forest use (first of all, forest pasturing and removal of deadwoods) was also intensive in the modern Reserve area until the middle of the 1980s. Important consequences of the last social-economic crisis of 1985–1989 for spontaneous ecosystem dynamics were the following reduction of the rural population, the abandonment of many villages and large areas of farmlands (Fig.  5.6), the cessation of forest pasturing, etc. Summing up all the aforesaid, one can conclude that features of the historical land use in the Reserve area led to the preservation of large forest tracts there. The main cause of forests being preserved was the administrative geographic position of the area, which was frontier, in one way or another, for many centuries. Long before the Reserve proclamation, forest exploitation in the area was restricted for different reasons. From the fifteenth to seventeenth centuries, the forests were preserved because of their defensive value at the borderline of Moscow State. In the eighteenth and nineteenth centuries, forests were taken care of because the government was concerned about the reserves of ship and construction timber. In the twentieth century, the forests were not exploited much because of the absence of good roads and the reduced rural population, especially after the Second World War. The main anthropogenic factors affecting the formation of the modern vegetation cover in the Reserve area during the last centuries were (i) in the area of the former Abatis belt, forest planting, selective felling, clear-cut, and forest pasturing, and (ii) in the rest of the area, agricultural use of lands (ploughing, haymaking, and pasturing) and forest planting after the Second World War.

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Fig. 5.6  Sheaves of the common flax (Linum usitatissimum) on the field bordering the Kaluzhskie Zaseki Reserve at the last year before abandonment (the photo was taken in 1997 by M. Bobrovsky)

5.3.2  Methods of Investigation The area of the Reserve consists of three forestry units: Ulyanovo, Yagodnoe, and Leninskoe. Only the first two units were the object of our investigations due to the absence of old-growth forests in the last forestry unit. That is occupied by post-cut young forests and was later added to the Reserve area aiming to create a buffer zone for the Reserve “core.” Vegetation was sampled, and the ontogenetic structure of tree populations was studied in the main communities from 1990 to 1998 under the leadership of Prof. Olga Smirnova, Dr. Roman Popadyuk, and Dr. Maxim Bobrovsky. The main types of plant communities were earlier defined (Bobrovsky and Khanina 2000; Khanina et al. 2002). We used more than 700 phytosociological relevés to specify the structure and composition of the communities and to estimate the vegetation diversity of the Reserve according to the methods described in Chap. 2 and some additional approaches (Smirnov et al. 2014). A cluster dendrogram of community types was calculated with the group average method and was based on the within-type and between-type binary Jaccard dissimilarities (Oksanen et al. 2011). To compare the alpha-diversity of different community types, boxplots of species number per sample plot were constructed and 999 pairwise randomization tests (Manly 2007) were conducted; the p-values obtained were adjusted for multiple comparisons. The beta-­ diversity for each community type was estimated as an average Jaccard dissimilarity

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( D ) and as a number of half compositional changes calculated according to McCune and Grace (2002). To compare the gamma-diversity (species richness) of communities differing in the number of relevés sampled, species accumulation curves according to Colwell et al. (2012) with 95% confidence intervals were constructed. Comparisons of alpha- and gamma-diversities were conducted only for the 10 best represented communities, i.e., those represented by more than 15 sample plots. The R statistic software (R Development… 2012) and the EstimateS program (Colwell 2013) were used for the calculations (Smirnov et al. 2014). More than 300 trees of Quercus robur, Fraxinus excelsior, Acer platanoides, Ulmus glabra, Pinus sylvestris, and Picea abies were cored to determine the absolute ages of the trees and to reconstruct the stand history; about half of the cored trees were Quercus robur individuals, but only for 30% of them, it was possible to determine the absolute age due to stem rot that afflicted most trees. Vegetation on abandoned arable lands and pastures located inside and close to the Reserve were additionally sampled from 2012 to 2014 aiming to assess the vegetation dynamics there. Soil research (more than 600 soil profiles in the Reserve area) has also been done (Ponomarenko et  al. 1993; Popadyuk et  al. 1999; Bobrovsky 2003, 2010; Bobrovsky and Loyko 2016), and the main soil features are discussed in the general description of the vegetation communities.

5.3.3  General Description of the Vegetation According to the 1986 forest inventory data, forests dominated by Quercus robur together with shade-tolerant broad-leaved trees occupy a quarter of the studied Reserve area (25%), Betula pendula and B. pubescens 26%, Populus tremula 22%, Picea abies 12%, Pinus sylvestris 12%, and Alnus glutinosa 1%; and 3% of the area is occupied by meadows and Salix spp. brushwood (Fig. 5.7). Nemoral herbaceous species dominate the ground layer in the greater part of the Reserve. Quercus robur broad-leaved forests are mainly located within the former Kozelsk Abatis belt consisting of several sections. In the Ulyanovo forestry unit (Fig. 5.7a), most of these forests occur as a large continuous tract located within the borders of the former Stolpitskaya section. Most of the Quercus robur individuals and late-­successional broad-leaved trees in the overstorey are nowadays between 100 and 160 years old. The elder individuals of all deciduous tree species (except Quercus robur) mainly grow from basal lateral shoots on stumps left after felling. Such a vegetative origin of elder trees shows the large-scale logging of the forest that took place in the area in the past. In the Yagodnoe forestry unit (Fig.  5.7b), stands dominated by Quercus robur and shade-tolerant broad-leaved trees are more fragmented; they are parts of the former continuous forest tract within the borders of the Dubenskaya section. The total area of these stands is practically the same as in the northern part of the Reserve. Quercus robur individuals in the southern part are nowadays mostly between 150 and 250 years old; the maximum age of the other tree species is more than 150  years old. Quercus robur specimens of more than

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Fig. 5.7  Schematic map of the studied forestry units in the Kaluzhskie Zaseki State Nature Reserve according to forest inventory data of 1986: A the Ulyanovo forestry unit (the northern part of the Reserve) and B the Yagodnoe forestry unit (the southern part of the Reserve)

300 years old occur in the northeast of the Yagodnoe forestry unit (Figs. 5.5 and 5.7b), where the largest area of well-preserved forest area is located. Luvisols predominate. Nemoral herbaceous species dominate the ground layer in all Quercus robur broad-leaved forests, so only one forest type, Querceto-Tilieta nemorosa, was distinguished. Quercus robur individuals of large sizes (up to 30 m in height and from 80 to 160 cm in diameter) often occur in the overstorey (Fig. 5.8). Besides Quercus robur, the other broad-leaved trees Tilia cordata, Fraxinus excelsior, Ulmus glabra, Acer platanoides, and A. campestre often dominate the overstorey. Populus tremula,

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Fig. 5.8 Large Quercus robur individual together with Tilia cordata and Fraxinus excelsior in the Querceto-Tilieta nemorosa in spring in the Yagodnoe forestry unit in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

Betula pendula (more often) or B. pubescens (less often), Salix caprea, Picea abies, and Ulmus laevis (rarely) occur. Cover of the overstorey is 60%; cover of the shrub layer averages 40%. Corylus avellana often dominates the shrub layer; its individuals are more than 200 years old, while the age of several individual stems is more than 50 years. Euonymus europaea, E. verrucosa, Lonicera xylosteum, and Padus avium are common, as is the undergrowth of Tilia cordata, Ulmus glabra, Acer campestre, A. platanoides, and Fraxinus excelsior. Cover of the field layer averages 65%. Nemoral species always dominate and average 72% of all species per plot in the field layer (Fig. 5.9a) though they account for only a third of all the herbaceous species recorded in these forests (Fig. 5.9b). Aegopodium podagraria, Asarum europaeum, Galeobdolon luteum, Pulmonaria obscura, Stellaria holostea, Mercurialis perennis, Milium effusum, Dryopteris ­filix-­mas, and other typical nemoral species are common in all broad-leaved forests (Fig.  5.10). There are many spring-growing and -flowering perennial herbs: Anemonoides ranunculoides, Ficaria verna, Gagea lutea, G. minima, and Corydalis solida are common not only in broad-leaved forests but also in other plant communities in the Reserve, whereas Corydalis cava, C. marschalliana, C. intermedia, Dentaria bulbifera, and D. quinquefolia mainly occur (often in high abundance) in forests dominated by Quercus robur and other broad-leaved trees (Fig. 5.11). Allium ursinum dominates in many stands; there are areas where this species totally covers the field layer from May till July and a ground layer of vegetation is absent there

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from the second half of the summer onward. The moss layer is poorly developed. Mosses mainly occur on trunk bases and on fallen trees. There are six variants of broad-leaved forests in the Reserve that differ in the ontogenetic structure of their tree populations (Fig. 5.12) and in features of the vegetation of the ground layer mainly due to differences in the ecosystem history of these forests. The first four variants developed after Quercus robur planting in the eighteenth, nineteenth, and the beginning of the twentieth centuries (Fig.  5.5). Thinning and other caring operations were usually carried out some time after the planting: this is indicated by large increases in the sizes of yearly rings for the first 30–40 years in the stem centers of older Quercus robur individuals. The first three variants are mainly described from the Yagodnoe forestry unit; the oldest forest stands occur there. The first variant (Q1 in Fig. 5.12) is the uneven-aged multi-species old-growth forest developed over a long period of spontaneous forest development after Quercus robur planting in the eighteenth and nineteenth centuries. The mean age of Quercus robur individuals is 220 years old (Fig. 5.8). Such forest is mainly located in the northeast of the Yagodnoe forestry (Fig.  5.5). Populations of Fraxinus excelsior, Acer spp., Tilia cordata, and Ulmus glabra have stable ontogenetic structures: individuals at all ontogenetic stages with the highest numbers of young specimens. Populations of Quercus robur and Populus tremula show regressive trends: only individuals at mature and old reproductive stages are found. Betula pendula rarely

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Fig. 5.11  The spring-growing and -flowering perennial herbs Corydalis cava (a) and Anemonoides ranunculoides, Corydalis solida, and C. marschalliana together with Allium ursinum, Pulmonaria obscura, and Aegopodium podagraria (b) in the Querceto-Tilieta nemorosa in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

occurs in the overstorey. Tree individuals of seed origin prevail and that indicates the absence of mass tree cutting in the past. Gaps in the canopy caused by the fall of large trees are rather well expressed. There is deadwood of different size at different decay stages; large fallen trees prevail (Fig. 5.13). Pits and mounds caused by treefalls with uprooting at different stages of their decay are common. Diversity of microsites defines diversity of herbaceous species. Besides common nemoral herbs, the nitrophilous species Matteuccia struteopteris, Filipendula ulmaria, Urtica dioica, and Lunaria rediviva often occur (Fig. 5.14a and b), sometimes with high abundance; the nemoral tall herbs Campanula latifolia, Stachys sylvatica, and Aegopodium podagraria can be often found at sites with improved light conditions caused by canopy gaps (Fig. 5.10). There are species occurring only on large fallen trunks, while they are absent from other forest sites: among them, the nitrophilous herbs Cardamine parviflora and Chamaenerion angustifolium, the meadow-edge Fragaria vesca and Taraxacum officinale, and the boreal herb Circaea alpina often occur (Fig. 5.14c and d). On large fallen trunks, juvenile and immature individuals of Betula spp. and all shade-tolerant trees are common. The nitrophilous plants Urtica dioica, Rubus idaeus, and Impatiens noli-tangere as well as the nemoral herbs Galeobdolon luteum and Glechoma hederacea occur in high abundance on large fallen trunks, and they also occur on mounds formed after treefalls with uprooting. Luvisols prevail in all broad-leaved forests (Fig. 5.15), but Phaeozems can also be found in these uneven-aged multi-species old-growth forests (Fig.  5.16) (Bobrovsky 2003; Bobrovsky et al. 2012). The humus horizon is 50 cm thick, on average, in Phaeozems; it forms as a result of activities of soil macrofauna (first of

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Fig. 5.12  Ontogenetic structures of tree species populations in the Querceto-Tilieta nemorosa in the Kaluzhskie Zaseki Reserve. Numbers of stems per hectare are presented on a logarithmic scale

all earthworms) decaying litter of tree leaves and herbs rich in nutrients. The number of earthworms in Phaeozems varies from 240 to 556 ind./m2; the worm biomass reaches 94  g/m2 (Shashkov 2014) and sometimes even more than 100  g/m2. Sometimes a humus horizon of 130 cm thick occurs as a consequence of the transfer of the humus material from the upper soil horizon into the pits during the treefalls with uprooting (Bobrovsky and Loyko 2016). Phaeozems probably are the initial soils formed during the spontaneous development of the forest ecosystem over a long time in the nemoral forest region, whereas Luvisols are formed as a result of farming, including ancient ways of land use (Bobrovsky 2010).

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Fig. 5.13  Large fallen trunk of Quercus robur with Urtica dioica and Impatiens noli-tangere in the uneven-aged multi-species old-growth broad-leaved forest (type Q1, see the text) in the Yagodnoe forestry unit in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

The second variant (Q2 in Fig. 5.12) is the pastoral Quercus robur forest which developed from the same Quercus robur plantations but under continuous intensive influence of forest grazing. The renewal of tree species and shrubs was suppressed until the termination of grazing (final in 1992). Young individuals of shade-tolerant tree species prevail and their populations show invasive types. Only mature and old reproductive specimens of Quercus robur occur. Recently, fallen trunks of the oldest Quercus robur individuals rarely occur. Carex pilosa often dominates the ground layer because this species is able to recover quickly on depleted and compacted soils after forest grazing (Remezova 1961; Kurnaev 1980); Allium ursinum is absent (Fig. 5.10). The third variant (Q3  in Fig.  5.12) is the forest dominated by large Quercus robur individuals (up to 1.5–2 m in diameter) in the overstorey with a much smaller ­participation of all other tree species. Such forest developed from the same plantations of Quercus robur in the eighteenth and nineteenth century followed by felling of all adult trees except Quercus robur at the end of the nineteenth or the beginning of the twentieth centuries. After improvement of the light regime, Quercus robur individuals began to grow successfully; some light-demanding trees, such as Betula pendula and Populus tremula, also quickly grew, and now these species, with a clear dominance of Quercus robur, form the upper layer of the canopy. Shadetolerant broad-­leaved trees also occur in the overstorey, but they are much smaller and form the second sublayer of the canopy. Young individuals of all light-demand-

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Fig. 5.14  Diversity of herbaceous species in the uneven-aged multi-species old-growth broad-­ leaved forest (Q1) in the Yagodnoe forestry unit in the Kaluzhskie Zaseki Reserve: Matteuccia struteopteris with Allium ursinum (a) and Urtica dioica, Matteuccia struteopteris, and Campanula latifolia (b) in the canopy gaps; Circaea alpina (c) and Fragaria vesca (d) on large fallen Quercus robur trunks (Photo A was taken by D. Bobrovsky and photos b–d were taken by M. Bobrovsky)

ing trees are absent, whereas populations of all shade-tolerant tree species are normal: specimens at all ontogenetic stages with the highest numbers of young individuals occur. Fallen Quercus robur trees rarely occur; the gap-mosaic in the canopy is practically absent. Typical nemoral species are common in the ground layer; on wet and nutrient-­richest sites, Allium ursinum often dominates covering the ground totally till the middle of summer (Fig. 5.10). Phaeozems occur at these sites (Bobrovsky 2003). The fourth variant (Q4 in Fig. 5.12) is the multi-species even-aged forest developed after Quercus robur planting on clear-cut areas at the end of the nineteenth and

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Fig. 5.15  Typical soil profile (Albic Luvisol) in the Querceto-Tilieta nemorosa in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

Fig. 5.16  Soil profile (Luvic Phaeozem) with an old pit pattern (a cauldron) caused by rotational treefall in the uneven-aged multi-species old-growth broad-leaved forest (Q1) in the Yagodnoe forestry unit in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

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Fig. 5.17  Broad-leaved forest (Q4) with fallen trunks of Quercus robur, shrubs of Corylus avellana in the understorey, and Allium ursinum in the ground layer in spring in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

the beginning of the twentieth centuries. Such forests occupy most of the broad-­ leaved forest tract located in the northern part of the Reserve. Broad-leaved forests had been clear-cut and Quercus robur were planted, but no care was taken of the plantations for any prolonged period of time. As a result, shade-tolerant trees began to grow from their stumps that were left and the growth of Quercus robur became suppressed. Present-day stands consist of mature and old reproductive individuals of Quercus robur with a low vitality, which are mainly of seed origin, and individuals of shade-tolerant broad-leaved trees of the same age (from 100 to 120 years old) which are growing from root shoots or basal lateral shoots (vegetative origin). The populations of all shade-tolerant tree species show stable ontogenetic structures. Patches of mass treefalls occur in these forests now (Fig. 5.17) and Urtica dioica and Lunaria rediviva dominate the field layer there (Figs. 5.10 and 5.18). The fifth variant (Q5 in Fig. 5.12) is presented by forests dominated more often by Tilia cordata or rarely Fraxinus excelsior or Ulmus glabra (Fig.  5.19). They developed as a result of numerous selective cuttings of broad-leaved forests often under conditions of moderate forest grazing. Most adult trees are growing from root shoots or basal lateral shoots. These forests occupy smaller areas throughout the Reserve. Quercus robur is absent; Populus tremula and Betula pendula usually occur in the overstorey and are absent in the undergrowth. Population structures of shade-tolerant broad-leaved species are mainly normal. Fallen trees and pit-and-­ mound topography are practically absent. Typical nemoral species dominate the

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Fig. 5.18  Lunaria rediviva in the broad-leaved forest (Q4) in the Ulyanovo forestry unit in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

Fig. 5.19  Broad-leaved forest dominated by Tilia cordata, Fraxinus excelsior, and Ulmus glabra with adult tree individuals growing from root or basal lateral shoots (Q5) and Allium ursinum in the ground layer in spring in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

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ground layer of the vegetation; sometimes Allium ursinum dominates with 100% coverage; Phaeozems can be found at such places. The sixth variant (Q6 in Fig. 5.12) is presented by broad-leaved forests growing in ravines earlier surrounded by agricultural fields that existed before the Second World War in the northern part of the Reserve and before the 1990s in the southern part. These fields are now overgrown by Betula spp. or planted by Pinus sylvestris (in the northern part of the Reserve). In the past, the broad-leaved forests in ravines were affected by moderate forest grazing and regular selective cutting. Vegetatively renewed individuals of Tilia cordata and Quercus robur dominate the overstorey; Populus tremula and Fraxinus excelsior often occur. Only in these ravine forests the populations of Quercus robur have a stable ontogenetic structure. Tilia cordata populations also show a stable ontogenetic spectrum; the populations of other shade-tolerant tree species are fragmented. Convallaria majalis and meadow-edge species as Fragaria vesca dominate the ground layer, besides typical nemoral species (Fig. 5.10). Populus tremula forests occupy rather small areas in the northern part of the Reserve; they are usually located inside the forest tracts dominated by Betula spp. or Pinus sylvestris, whereas in the southern part of the Reserve, Populus tremula forests occupy large areas (Fig. 5.7). Populus tremula forests are mainly located on Luvisols. Nemoral herbaceous species dominate the ground layer in all Populus tremula stands, so only one forest type Populeta nemorosa was distinguished (Fig. 5.20).

Fig. 5.20  Populeta nemorosa with Tilia cordata in the undergrowth and the second sublayer of the canopy in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

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Besides Populus tremula, the shade-tolerant trees Tilia cordata, Acer platanoides, and Ulmus glabra and the light-demanding trees Betula pendula and B. pubescens often occur in the overstorey; individuals at ages from 60 to 90 years prevail in the stands. Cover of the overstorey is about 70%. These forests mainly developed after repeated selective felling of forests dominated by broad-leaved trees, so the ontogenetic structures of the tree species populations are similar to those described from post-cutting forests dominated by Tilia cordata (Q5 in Fig. 5.12) with the difference that reproductive individuals of Populus tremula prevail in the spectrum, but young individuals of this species are absent. Undergrowth of Tilia cordata, Fraxinus excelsior, and Acer platanoides dominates. Corylus avellana dominates the shrub layer; Lonicera xylosteum, Euonymus europaea, E. verrucosa, and Sorbus aucuparia are common. Cover of the shrub layer averages between 30 and 40%. Cover of the field layer is 70% on average. Nemoral herbaceous species dominate the ground layer and average 68% of the species per plot, close to that in forests dominated by Quercus robur and shade-tolerant broad-leaved trees (Fig. 5.9a), but in Populus tremula forests nemoral species account for 48% of the total list of herbaceous species (Fig. 5.9b). Aegopodium podagraria, Pulmonaria obscura, Asarum europaeum, Galeobdolon luteum, Stellaria holostea, and Carex pilosa often occur. Among spring-growing and -flowering herbs, Corydalis cava, C. solida, Anemonoides ranunculoides, Gagea lutea, and Ficaria verna are common. Betula spp. forests developed as a result of spontaneous overgrowing of ­abandoned agricultural lands and clear-cut areas. Luvisols dominate in Betula spp. forests located on sandy loams; Arenosols and rarer Podzols dominate in these forests located on sands. In the Reserve area, we distinguish meadow herb and nemoral herb Betula pendula / B. pubescens forests (Betuleta pratoherbosa and Betuleta nemorosa, respectively). Meadow herb Betula spp. forests developed as a result of overgrowing of former arable lands, meadows, and pastures. Before the proclamation of the Reserve, these forests were maintained by grazing and rarely haymaking. Stands are sparse; cover of the overstorey averages 30%. Betula pendula dominates the stands; Betula pubescens and Populus tremula often co-dominate. Quercus robur, Tilia cordata, Salix caprea, Picea abies, and Pinus sylvestris rarely occur. Cover of the shrub layer is 30%. Corylus avellana, Tilia cordata, and Quercus robur dominate the understorey; Sorbus aucuparia, Malus sylvestris, Betula pendula, B. pubescens, Populus tremula, Picea abies, and Frangula alnus can be found. Cover of the field layer is 70%. Meadow-edge species average 54% and nemoral species 18% per plot (Fig. 5.9a), and their proportions in the total list of herbaceous species in this forest type are similar (Fig.  5.9b). Fragaria vesca, Veronica chamaedrys, Angelica sylvestris, Hypericum maculatum, Knautia arvensis, Potentilla erecta, etc. often occur. A moss layer is absent. In the absence of external impacts (such as grazing, mowing, and fire), shade-­ tolerant trees, shrubs, and herbs re-populate these forests, and Betuleta pratoherbosa is gradually changed into Betuleta nemorosa (features of the forest recovery are discussed below in this section).

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Fig. 5.21  Betuleta nemorosa (with old stumps of Quercus robur formed after clear-cut of broad-­ leaved forest) in spring in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

Nemoral herb Betula spp. forests are mostly located in the Yagodnoe forestry unit. These forests developed either as a result of forest recovery after Betuleta pratoherbosa or after clear-cut of broad-leaved forests (Fig.  5.21). When broadleaved forests are cut with serious disturbance of the ground layer, as usually happens in a summer cutting, then the soil is bared and Betula spp. have the opportunity to establish successfully. In mesophytic conditions on sandy loams, the field layer of the vegetation usually quickly recovers, and nemoral herbaceous species begin to dominate. Cover of the overstorey is 60%. Betula pendula mainly dominates the overstorey; B. pubescens sometimes co-dominates. Populus tremula, Tilia cordata, and Quercus robur usually occur in the stands with low abundance; Picea abies, Acer campestre, A. platanoides, Fraxinus excelsior, and Ulmus glabra rarely occur. Cover of the shrub layer averages 40%. Corylus avellana and undergrowth of Tilia cordata dominate the shrub layer. Sometimes Picea abies, Sorbus aucuparia, and Acer platanoides occur in the understorey with high abundance. Cover of the field layer averages 70%. Nemoral species dominate the ground layer and account for 60% per plot on average (Fig. 5.9a); they comprise 40% of the total list of herbaceous species in this forest type (Fig.  5.9b). Aegopodium podagraria, Asarum ­europaeum, Carex pilosa, Galeobdolon luteum, Stellaria holostea, and Pulmonaria obscura, etc. are common. A moss layer is absent. Picea abies forests are plantations of Picea abies on abandoned agricultural lands or on forest areas after clear-cut. In the Reserve, these plantations occupy

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rather small areas and they are surrounded by nemoral herb forests (Fig. 5.7). Picea abies was mainly planted on sandy soils; Podzols and Arenosols dominate there. In the Yagodnoe forestry unit, some Picea abies stands are located on Luvisols. Borealnemoral and nemoral herb Picea abies forests (Piceeta boreo-nemoroherbosa and Piceeta nemorosa, respectively) are distinguished in the Reserve. Boreal species in the ground layer appeared first after the planting of Picea abies. This is always the case when trees are planted on former agricultural fields, and we also observed this in plantations on clear-cut areas inside broad-leaved forests. That is an age stage in the development of these stands when the density of trees is high and the ground layer is strongly shaded. Boreal species, such as Maianthemum bifolium, Luzula pilosa, Solidago virgaurea, etc., dominate. With increasing stand age, their density decreases and that goes together with an expansion of nemoral herbs, such as Galeobdolon luteum, Asarum europaeum, Stellaria holostea, Pulmonaria obscura, etc., and the nemoral herb Picea abies forest develops. Thus, Piceeta boreo-nemoroherbosa and Piceeta nemorosa are successional stages of Picea abies plantations in the Reserve, and probably, this is true for all Picea abies plantations under mesophytic conditions over the entire nemoral forest region. In the boreal-nemoral herb Picea abies forests, cover of the overstorey averages 80%. Besides Picea abies, only Quercus robur and Betula pendula occur in the stands. The number of individuals in the undergrowth is small due to high coverage of the overstorey and shading of the lower layers: only young specimens of the shade-tolerant species Tilia cordata, Acer platanoides, and Picea abies can be found. Cover of the shrub layer is 40%. Corylus avellana, Sorbus aucuparia, and Frangula alnus occur. Cover of the field layer is 30%. The boreal herbs Maianthemum bifolium, Luzula pilosa, Solidago virgaurea, and Rubus idaeus together with the nemoral species Convallaria majalis, Carex digitata, and Dryopteris carthusiana often occur. Nemoral herbaceous species average 44% and boreal species 42% of the field layer per plot (Fig. 5.9a); the same ratios for these groups of species were calculated for the total list of herbaceous species in this forest type (Fig.  5.9b). Mosses cover 40% of the ground. Pleurozium schreberi, Hylocomium splendens, and Dicranum spp. prevail. In the nemoral herb Picea abies forests, cover of the overstorey averages 80%. Besides Picea abies, Populus tremula is common in the overstorey; Betula pendula often occurs. Quercus robur, Acer platanoides, Tilia cordata, Fraxinus excelsior, and Ulmus glabra also can be found. The age of Picea abies widely varies from 35 to 140  years. The majority of the individuals is between 40 and 95  years old. Undergrowth of Acer platanoides, Sorbus aucuparia, and Tilia cordata is common. Undergrowth of Picea abies rarely occurs in stands located inside nemoral herb broad-leaved forests due to the high competitive abilities of nemoral herbs, shrubs, and trees which impede the renewal of Picea abies. In plantations located on abandoned arable lands, Picea abies successfully renews. Cover of the shrub layer is 50%. Corylus avellana dominates. Cover of the field layer is about 50%. Nemoral species, such as Galeobdolon luteum, Asarum europaeum, Stellaria holostea, Pulmonaria obscura, Carex pilosa, Aegopodium podagraria, and Dryopteris carthusiana, often occur. The same spring-growing and

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-flowering species occur as those occurring in the Quercus robur forests, except for Corydalis marschalliana. Nemoral herbaceous species average 72% of the field layer per plot (Fig. 5.9a), and they account for 48% in the total list of herbaceous species in this forest type (Fig. 5.9b). Cover of the moss layer is not more than 5%. Pinus sylvestris forests developed as a result of planting of Pinus sylvestris on abandoned arable lands and meadows; they are mainly located in the northern part of the Reserve (Fig. 5.7). Pinus sylvestris is mainly between 60 and 75 years old; individuals of 150 or 160 years old rarely occur. Pinus sylvestris was planted on sandy soils; variants of Podzols, sometimes Arenosols, dominate there. We distinguish nemoral herb, piny (or xerophytic) herb, and meadow herb Pinus sylvestris forests (Pineta nemorosa, Pineta xerophyta-herbosa and Pineta pratoherbosa, respectively). Nemoral herb and piny herb Pinus sylvestris forests developed from the same plantations of Pinus sylvestris on abandoned agricultural lands surrounded by Quercus robur and shade-tolerant broad-leaved forests. Nemoral species could penetrate into Pinus sylvestris plantations only without fire, since fire limits the survival of seedlings and the development of nemoral species. Without fire, nemoral species successfully establish and already 30- or 50-year-old plantations of Pinus sylvestris have Quercus robur and other broad-leaved trees in the overstorey and in the understorey; and they also have nemoral shrubs and herbs in their species composition. On the contrary, in places with repeated ground fires (once in 3–8 years before the proclamation of the Reserve), only piny species dominate and nemoral plants are practically absent. In the Reserve, patches of nemoral and piny herb Pinus sylvestris forests are located in compliance with the local fire frequency. Piny herb Pinus sylvestris forests are located close to the roads and borders of the Reserve where spring grass fires often happen due to local people. In nemoral herb Pinus sylvestris forests, Betula spp. often co-dominate with Pinus sylvestris in the overstorey; Quercus robur also occurs. Acer platanoides, Tilia cordata, and Picea abies are common as an admixture in the second sublayer of the canopy. Cover of the overstorey is 60%. Cover of the shrub layer averages also 60%. Corylus avellana, Picea abies, Quercus robur, Acer platanoides, and Sorbus aucuparia dominate. Tilia cordata, Betula pendula, Fraxinus excelsior, Ulmus glabra, Acer campestre, Frangula alnus, and Euonymus verrucosa often occur. Cover of the field layer is 50%. The nemoral species Stellaria holostea, Galeobdolon luteum, Convallaria majalis, and Dryopteris carthusiana and the boreal herb Rubus idaeus often occur. Nemoral species dominate the field layer and account for 48% of the herbaceous species per plot on average (Fig. 5.9a) though they make up for only 29% of the total list of herbaceous species in this forest type (Fig.  5.9b). A moss layer is not developed, but Pleurozium schreberi and Brachythecium salebrosum can be found; green mosses occur on dead woods and on the bases of trunks. In piny herb Pinus sylvestris forests only Pinus sylvestris dominates the overstorey (Fig. 5.22). Occurrence of other species depends on fire frequency. Invasions of broad-leaved trees into these forests from surrounding stands are common. However, during the next fire, most of these invaded individuals die and a new invasion wave

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Fig. 5.22  Pineta xerophyta-herbosa with Picea abies undergrowth in the Ulyanovo forestry unit in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

begins. Quercus robur populations are the most successful in this process because their fruits are dispersed and buried by jays and even young Quercus robur individuals show some degree of fire resistance and survive mild or mediocre fires. Some Quercus robur individuals reach the young reproductive ontogenetic stage in these communities. Cover of the overstorey varies between 30 and 50%. More often Quercus robur, Betula spp., and to a lesser extent also Picea abies and Populus tremula occur in the overstorey. Cover of the shrub layer is about 20%. Quercus robur, Pinus sylvestris, Betula pendula, Sorbus aucuparia, and Frangula alnus often occur; Picea abies and Corylus avellana can also be found. Cover of the field layer strongly varies and averages 30%. Piny herbaceous species, such as Festuca ovina, Calamagrostis epigeios, Hieracium umbellatum, Antennaria dioica, etc., often occur, sometimes in high abundance; meadow species, such as Agrostis tenuis, Fragaria vesca, Galium mollugo, etc., often occur; the boreal species Anthoxanthum odoratum, Luzula pilosa, and Solidago virgaurea also occur. Species of the piny group account for 21% per plot on average, meadow and boreal species for 43 and 21%, respectively (Fig.  5.9a), but in the total list of ­herbaceous species of this forest type, piny species make up only 13% due to prevalence of meadow species (51%) (Fig. 5.9b). Cover of the moss layer varies from 60 to 80%. Pleurozium schreberi and Dicranum spp. dominate. Meadow herb Pinus sylvestris forests occupy relatively small areas in the Reserve, near former villages. These forests developed as a result of Pinus sylvestris planting on mesophytic meadows. Before the Reserve was proclaimed, meadow

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species were maintained in the plantations by ground fires and grazing. Now the composition of these communities gradually changes toward nemoral species. Cover of the overstorey is relatively low and averages 40%. Only Pinus sylvestris occurs there. Before the proclamation of the Reserve, these forests were pastoral ones: an undergrowth of shrubs and trees was absent. After the cessation of grazing and mowing, some places have seen a renewed establishment of Pinus sylvestris especially in the areas that were intensively grazed earlier on; undergrowth of Quercus robur and Betula spp. also occurs. Generally, the shrub layer is very sparse; its cover averages 5%. Betula pendula, B. pubescens, Malus sylvestris, Picea abies, Juniperus communis, Salix caprea, and Pinus sylvestris rarely occur. Cover of the field layer is 80%. Meadow species dominate and account for 43% of the species per plot on average (Fig. 5.9a); they account for 51% of all herbaceous species for this community (Fig. 5.9b). Knautia arvensis, Veronica chamaedrys, Galium mollugo, Pimpinella saxifraga, Fragaria vesca, etc. often occur. The moss layer is not developed. Alnus glutinosa forests occupy small areas in floodplains of small rivers throughout the Reserve (Fig. 5.7). As a result of intensive livestock grazing, cuttings, and the complete absence of beaver (Castor fiber) settlements before the Reserve’s proclamation, Alnus glutinosa riparian forests hardly occurred and their habitats were largely occupied by Salix spp. brushwood and hygrophytic meadows; Alnus glutinosa survived only in areas where grazing was insignificant. Beaver settlements appeared in the Reserve in the middle of the 1990s: while the area only was protected from visitors and hunters, Castor fiber has sharply increased in numbers and settled in all available streams. In floodplains of small rivers and streams, the beavers create a specific landscape altering the hydrological regime and forming a plurality of specific ecotopes, such as dams, ponds, marshy meadows, canals, etc. (Zavyalov 2015; Fig. 5.23). As a result, the floodplain landscape in the Reserve is increasingly invaded and dominated by Alnus glutinosa, also in the tree layer. Forests dominated by Alnus glutinosa are located on Fluvisols and Histosols. Nitrophilous species dominate the ground layer in Alnus glutinosa communities, so only one forest type, Alneta glutinosae nitrophiliherbosa, is distinguished. Cover of the overstorey averages 40%. Alnus glutinosa dominates and sometimes Betula pubescens and Populus tremula co-dominate the overstorey due to cuttings it in the past. Populations of Alnus glutinosa show fragmentary ontogenetic structures: there are mature and old reproductive individuals as well as immature ones; the number of virginal and young reproductive individuals is small. Young individuals of Alnus glutinosa appear on deadwood; filial individuals of Alnus glutinosa also develop out of dormant buds at the base of the trunks that are activated by the damage related to river activities. It is noteworthy that new stems develop from dormant buds located on the somewhat higher part of the stem base; the first subordinate roots of new stems initially hang in the air and then grow out to water or soil level and start branching. As a result, Alnus glutinosa roots create a hillock: the open space between the hanging roots is filled with litter, soil material, and deadwood and becomes a good substrate for the settlement of many plant species

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Fig. 5.23  Alneta glutinosae nitrophiliherbosa with a beaver’s dam and pond in spring in the Moshok River in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

(Sarycheva 1998). Shade-tolerant broad-leaved trees and Picea abies also have begun to renew in the communities; their populations are invasive ones. The shrub layer is sparse (cover is 10–20%), but its diversity is high; Padus avium, Alnus glutinosa, and Frangula alnus are common. Cover of the field layer averages 80%. Nitrophilous species, such as Filipendula ulmaria, Urtica dioica, Lysimachia vulgaris, Impatiens noli-tangere, etc., dominate and often occur. They average 35% of the species per plot; 22% and 21% are accounted for by species of the water-marsh and nemoral groups, respectively (Fig. 5.9a); the proportions of these groups are practically the same in the total list of herbaceous species for this forest type, with exception of the increasing number of meadow-edge species (Fig. 5.9b). Cover of the green and sphagnum mosses strongly varies and averages 20%. Salix spp. brush woods are recently overgrown meadows mainly located in valleys of small rivers. Nitrophilous species dominate the ground layer, and only Saliceta nitrophiliherbosa is distinguished. There is no tree canopy. Cover of the shrub layer is 50%. Salix cinerea dominates; S. aurita, S. triandra, S. pentandra, S. myrsinifolia, and Betula pubescens co-dominate. Padus avium, Populus tremula, and Salix caprea often occur. Cover of the field layer averages 65%. The nitrophilous species Filipendula ulmaria, Lysimachia vulgaris, Deschampsia cespitosa, etc. dominate; the water-marsh species Scutellaria galericulata, Galium palustre, Juncus effusus, and Rumex aquaticus often occur. Species of water-marsh, nitrophilous, and meadow-edge groups average 32%, 27%, and 28% per plot in the herbaceous layer of the vegetation (Fig. 5.9a); these proportions are practically the same

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in the total list of herbaceous species for this community (Fig. 5.9b). Cover of the moss layer varies from 10 to 20%. Meadow communities occupy fields that have long been cleared of forest. They contain abandoned arable lands, pastures, and hay meadows, the latter two occurring on watersheds as well as in floodplains. The same fields may have been used at different times in different ways; grass fires may have occurred there in the past. In the northern part of the Reserve, these fields are small; they were used as hay meadows and pastures during the last years before the proclamation of the Reserve. In the studied southern part of the Reserve, the largest fields are located in the north (Fig. 5.7). Here the “Chichin Meadow” area was cleared not later than in the middle of the nineteenth century, as shown by historical documents, and was used for ploughing, haymaking, and later as pastures. Mesophytic meadows (Prata mesophyto-herbosa) are mainly located on Luvisols. Phaeozems occur in some parts of the Chichin Meadow; probably these parts were not ploughed, but they were used for haymaking for most of the time since forest clearing. Cover of the field layer averages 90%. Meadow species dominate and average 79% of all species per plot (Fig. 5.9a); these species account for 66% of the total list of herbaceous species in mesophytic meadows (Fig. 5.9b). The meadow species Achillea millefolium, Agrostis tenuis, Campanula patula, Centaurea jacea, Festuca rubra, Knautia arvensis, Phleum pratense, Veronica chamaedrys, and Leucanthemum vulgare often occur. Green mosses cover about 10%. Hygrophytic meadows (Prata hygrophyto-herbosa) are mainly located on Fluvisols. Cover of the field layer averages 90%. The nitrophilous species Deschampsia cespitosa, Filipendula ulmaria, Lysimachia vulgaris, and Urtica dioica dominate and often occur; water-­ marsh species, such as Carex vesicaria, Calamagrostis canescens, Agrostis canina, etc., often occur. Meadow, water-marsh, and nitrophilous species average 42%, 23%, and 22% of all species per plot (Fig. 5.9a); these proportions are close to those in the total list of herbaceous species (47%, 19%, and 15%) (Fig. 5.9b). Green mosses cover about 25%. Presently, the meadow communities are overgrown by forest vegetation; below, we describe this in detail for mesophytic meadows. Renewal of tree species on hygrophytic meadows occurs only on fallen trunks of dead trees, and thus, these meadows, located far from forests, can be preserved for a long time. Moreover, without human impacts, the meadow communities in the Reserve more or less can be maintained by animals. Mesophytic meadows are maintained by European bison (Bison bonasus) (Ivanova et al. 2018), which were reintroduced in the Reserve in 2001 (Fig.  5.24a), and hygrophytic meadows are mainly maintained by beavers (Fig. 5.24b). Phytosociological research on this topic was not yet done, but a floristic study showed the large positive influence of these animals on species composition in the Reserve area (Reshetnikova and Bobrovsky 2016). Thus, rare species, such as Ophioglossum vulgatum, Trisetum sibiricum, Carex hartmanii, Dracocephalum ruyschiana, Epilobium parviflorum, Veronica teucrium, Galium boreale, Dipsacus strigosus, etc., were first registered in the Reserve in 2014 and 2015 on meadows with bison grazing and on bison tracks (Reshetnikova et al. 2015). In communities

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Fig. 5.24  Habitats which were physically altered by herbivores in the Kaluzhskie Zaseki Reserve: (a) a locality with a free ranging Bison bonasus population and a large Ulmus glabra individual damaged by bison and (b) a Castor fiber’s dam and pond in the Moshok River (Photos by M. Bobrovsky)

formed by beavers, a lot of rare species, such as Scirpus radicans, Spirodela polyrhiza, Polygonum amphibium, Ceratophyllum demersum, C. submersum, Utricularia australis, Scrophularia umbrosa, etc., have been recorded (Reshetnikova et al. 2015).

5.3.4  Plant Diversity Assessment Thirteen plant communities were distinguished in the Reserve area. There were 577 vascular plants including 25 tree, 25 shrub, and 527 herbaceous species in 722 analyzed phytosociological relevés, and more than 700 vascular species are registered in the list of the Reserve’s flora (Shovkun and Yanitskaya 1999; Reshetnikova and Bobrovsky 2016). According to the ecological indicator values of the species (Ellenberg et al. 1991; Landolt et al. 2010), soil moisture and illumination are the main ecological gradients along which the vegetation varies (Bobrovsky and Khanina 2000). Cluster analysis of the communities showed the high floristic similarity between communities dominated by species of the same ecological-coenotic groups (Fig. 5.25). There are three main branches in the dendrogram (from left to right in Fig. 5.25): (1) communities dominated by meadow-edge species in the field layer of vegetation, (2) communities dominated by nemoral and piny-boreal species, and (3) communities dominated by nitrophilous and water-marsh species in the field layer. The central branch (2) is well divided into plant communities dominated by nemoral species in the field layer, and communities dominate by piny and boreal species. Only plots sampled in nemoral herb Pinus sylvestris forests appeared to be floristi-

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Fig. 5.25  Cluster dendrogram of 13 plant communities described from the State Nature Reserve Kaluzhskie Zaseki. Plant communities: MH Prata mesophyto-herbosa, BM Betuleta pratoherbosa, PnM Pineta pratoherbosa, PpN Populeta nemorosa, QN Querceto-Tilieta nemorosa, BN  Betuleta nemorosa, PcN Piceeta nemorosa, PnF Pineta xerophyta-herbosa, PcB Piceeta boreo-nemoroherbosa, PnN Pineta nemorosa, MW Prata hygrophyto-herbosa, ANt Alneta glutinosae nitrophiliherbosa, and SNt Saliceta nitrophiliherbosa

cally closer to plots sampled in boreal herb Picea abies forests and piny herb Pinus sylvestris forests than to communities dominated by nemoral herbs in the field layer, but that is well expressed in similarities the ecological-coenotic structure of these communities (Fig. 5.9). Number of vascular plants per plot (100 m2) greatly varied from 10 to 77 and averaged 33.5 for all the plots; the large range was observed in communities of mesophytic meadows and meadow herb Betula spp. forests (Fig. 5.26). Mean number of vascular species per plot within the plant communities (alpha diversity of the communities) varied from 21.9 in boreal herb Picea abies forests to 55.7 in meadow herb Pinus sylvestris forests. There were four community groups inside which the alpha-diversity was not significantly different (letters from a to d in Fig. 5.26). They are two of the richest groups consisting of (a) meadow herb Betula spp. forests and mesophytic meadows (alpha-diversity varied from 46.4 to 48.3) and (b) Alnus glutionsa forests and hygrophytic meadows (alpha-diversity varied from 31.9 to 35.7),

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Fig. 5.26  Boxplots of the numbers of vascular species per plot in the plant communities of the Reserve Kaluzhskie Zaseki; n is sample size. The midline is the median, the top and bottom of the box are the upper and lower quartiles, the whiskers are extended to the largest/smallest observation within 1.5 interquartile ranges of the top/bottom, and the circles denote observations beyond these limits. Boxes with the same letter were not significantly different (at 5% significance level) according to results of pairwise randomization tests for the ten best represented communities. Plant communities are the same as in Fig. 5.25

and two groups poorer in alpha-diversity and mainly consisting of communities dominated by nemoral species in the ground layer (ranges of alpha-diversity were (c) from 25.1 to 31.9 and (d) from 24.2 to 28.2). Alpha-diversity in forests dominated by Quercus robur and/or shade-tolerant broad-leaved trees was 28.9 vascular species per 100 m2. Values of beta-diversity calculated as an average Jaccard dissimilarity and as a number of half compositional changes (McCune and Grace 2002) differ in the same way. Maximum values of beta-diversity were calculated for meadow communities (Fig.  5.25): average within-group Jaccard distance was 0.89 and 0.81 for hygrophytic and mesophytic meadows, respectively. Minimum values of beta-diversity

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Fig. 5.27  Interpolation (QN and MH) and extrapolation (the other communities) estimates of ­species richness of the ten best represented communities of the Kaluzhskie Zaseki Reserve. Species accumulation curves and confidence (95%) intervals are constructed according to Colwell et al. (2012); no overlap of the intervals shows statistical difference in species richness for sample groups. Intervals correspond to a reference sample of 57 relevés. Plant communities are the same as in Fig. 5.25

(Jaccard dissimilarity less than 0.7) were calculated for forests dominated by Picea abies, Populus tremula, Quercus robur, and/or shade-tolerant broad-leaved trees. On the whole, floristic heterogeneity was rather high as the McCune and Grace index was not less than 1.5 for each community, and the total index for the whole Reserve was 2.03 (Smirnov et al. 2014). Mesophytic and hygrophytic meadows, meadow herb Betula spp., Alnus glutinosa, and Quercus robur forests were richest in the total number of vascular species (gamma-diversity): 401, 280, 256, and 255 vascular species were, respectively, registered there. The other communities were rather poorer: their species richness decreased from 195 to 76 species per community. However, analysis of species accumulation curves and confidence (95%) intervals (Fig. 5.27) for the ten best represented communities of the Reserve identified two large groups of communities

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statistically differing in gamma-diversity: (1) the richest communities are those dominated by meadow and nitrophilous species in the ground layer and (2) the other communities are the poorer ones. Thus, the analysis of plant species diversity showed that although forests dominated by Quercus robur and shade-tolerant broad-leaved trees hold a large number of vascular species which are not only nemoral but also meadow-edge and nitrophilous species (Fig. 5.9b), the maintenance of the high plant diversity in the Reserve is possible as long as meadows and water-rich habitats persist within the broad-­ leaved forest landscape, for example, due to bison and beaver activities.

5.3.5  Forest Recovery on Abandoned Agricultural Lands For several reasons, abandoned agricultural lands in the Reserve area are unique objects to study spontaneous reforestation on the fields. Firstly, we know the history of these sites, including their fire history, the time of abandonment of the fields, and the last anthropogenic impacts. Secondly, there are fields which were not affected by fire and that is rare in central Russia. Thirdly, abandoned fields are surrounded by species-rich old-growth broad-leaved forest and that also is not typical for the nemoral region. We have studied vegetation dynamics on the former arable lands and pastures abandoned between 25 and 30 years ago and mainly located in the Chichin Meadow area in the Yagodnoe forestry unit (see above). Composition and structure of the vegetation were studied in ten fields separated by forested ravines within the Chichin Meadow: four former ploughed fields and six former pastures (Fig. 5.28). Aiming to research forest recovery with and without fire, we additionally studied two and four abandoned ploughed fields adjoining the Reserve in the east and the west, respectively. Most of the abandoned fields were 200 m wide though the widest fields were 500 m. We distinguish between former arable lands and pastures because of the big difference in their initial conditions for forest recovery. An abandoned ploughed field is bare land on which the pioneer tree species Betula spp. and Salix caprea easily establish themselves since they successfully compete with other species due to their large number of seeds and high growth rates. An abandoned pasture (used for grazing as well as haymaking) is mainly covered with the tussocks of the grasses. For successful germination and establishment, nearly all tree species need the open sites with somewhat loose soil which are created due to burrowing activities of animals, such as wild boar, murine rodents, and moles. Of the regional tree species, only Quercus robur has the ability to germinate on the undisturbed soil surface patches between the tussocks; additionally, many acorns are buried by jays and then germinate. Furthermore, former pastures in the Reserve usually have a higher initial plant diversity than arable lands, but that also depends on grazing intensity. Thus, the following three types of the biotope were studied (Moskalenko and Bobrovsky 2012, 2014): (1) overgrown former arable lands on which no fires had burnt, (2) overgrown former arable lands affected by fires, and (3) overgrown for-

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Fig. 5.28  Satellite images of abandoned agricultural lands surrounded by old-growth forest in the Kaluzhskie Zaseki Reserve in 2005. (a) the Chichin Meadow area in the Yagodnoe forestry unit: 1 former ploughed fields overgrowing without fire, 2 former ploughed fields affected by fire, 3 former pastures. (b), (c) examples of former ploughed fields overgrowing without fire and affected by fire, respectively, and (d) an example of a former pasture

mer pastures without fire. Luvisols dominate in all these former lands. Vascular plants were sampled in 134 square plots of 100 m2; within each plot, each tree with a DBH of more than 5 cm was recorded; smaller tree individuals were counted per species in 3 square plots of 2 × 2 m located on 2 corners and in the center of 100 m2 plot. Annual increases in height were measured for the undergrowth of six tree species: Acer platanoides, A. campestre, Fraxinus excelsior, Quercus robur, Tilia cordata, and Ulmus glabra; the last 5 annual height increases of the main axes were measured for 170 tree individuals. All measurements were done in 2012–2014, but we have observed these fields since the beginning of 1990s, and that allows us to give a qualitative description of the overgrowth stages. The following results on features of forest recovery, and on vegetation and plant diversity dynamics, were obtained for the three studied biotopes surrounded by old-­ growth broad-leaved forest. (1) Ploughed fields which were not affected by fire since abandonment: they were abandoned in the middle of the 1980s or in the beginning of 1990s. These fields were evenly covered by seedlings of the pioneer tree species Betula pendula (often), B. pubescens, and Salix caprea (rarer) in the first year after their

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a­ bandonment. Crowns of immature individuals of these species first closed up in 3 or 4 years. As the size of the individuals increased, self-thinning occurred: some tree individuals died, while others grew. The last self-thinning of these pioneer trees occurred in 20–25 years, and thus, in 25–30 years after land abandonment, there was young forest dominated by elder virginal and young reproductive individuals of Betula pendula, B. pubescens, and Salix caprea. The number of trees in the overstorey varied on different fields from 500 to 1725 ind./ha; cover of the overstorey averaged 60%; tree crown distribution was uniform (Fig. 5.28a number 1, b). Besides Betula spp. and Salix caprea, Populus tremula rarely occurred; single specimens of Tilia cordata and Picea abies occurred on a single field. Ten to fifteen years after the abandonment of the land, the shade-tolerant broad-­ leaved trees Fraxinus excelsior, Tilia cordata, Acer platanoides, A. campestre, and Ulmus glabra and shade-tolerant shrubs such as Lonicera xylosteum, Euonymus verrucosa, E. europaea, and Corylus avellana appeared in the understorey from the side of the old-growth broad-leaved forest. And 25–30 years after the abandonment of the land, in a 100  m wide zone along the forest margin (i.e., the abandoned ploughed field zone adjacent to the old-growth broad-leaved forest), shade-tolerant broad-leaved trees predominated in the understorey (Fig. 5.29a). Total number of tree individuals in the undergrowth varied on different fields from 20,558 to 83,314 ind./ha; Fraxinus excelsior and Acer platanoides dominated. During the first stage (the first 10–15 years), herbaceous meadow and grassland species occupied the ground layer of the establishing young forests dominated by Betula spp. or Salix caprea; they came in after the trees. After the appearance of shade-tolerant trees and shrubs in the understorey (10–15 years after the abandonment of the lands), the shade-tolerant herbs Asarum europaeum, Pulmonaria obscura, Galeobdolon luteum, Stellaria holostea, Aegopodium podagraria, Dryopteris carthusiana, etc. started to penetrate from the forest margin. In the study area, the range dispersal of most of the herbaceous forest species was 50–70 m from the forest margin; the maximum range was about 120 m. During the next 10–15 years, shade-tolerant herbaceous species won in the competition from the grasses and other light-demanding species and began to dominate the ground layer in the area close to the old-growth forests with a dense undergrowth of broadleaved trees. Thus, in 25–30 years, after the beginning of forest recovery on the abandoned arable fields, the area within 50–70  m from the forest margin was covered by a 25–30-year-old Betula spp. with Salix caprea forest with a dense undergrowth of all broad-leaved trees and a well-developed ground layer dominated by shade-tolerant herbaceous species; this forest belongs to the Betuleta nemorosa (Fig. 5.30). At a distance of more than 70  m from the forest margin, there was the same young forest dominated by 25–30-year-old Betula spp. in the overstorey, but with a sparse undergrowth of broad-leaved trees and light-demanding meadow and grassland species dominated in the ground layer. This forest belongs to the Betuleta pratoherbosa. Forty-four vascular species per 100  m2 on average were recorded there. In the area bordering the old-growth forest, we scored 36 vascular species per 100 m2 and in the old-growth forest 26 species per plot on average. From the margin with the old-growth forest to the center of the former arable lands, the number and

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Fig. 5.29  Proportion of the total number of tree species individuals in the undergrowth on former arable lands and pastures in the Kaluzhskie Zaseki Reserve: (a) abandoned arable lands without fire, (b) abandoned arable lands with fire, (c) marginal zone of abandoned pastures, and (d) center of abandoned pastures. On the horizontal axis the studied fields: A arable fields without fire, AF arable fields affected by fires, P pastures

proportion of nemoral species decreased and meadow-edge species increased, whereas the numbers of boreal and nitrophilous species were the same (Fig. 5.31a). (2) Ploughed fields affected by fires were abandoned in the beginning of the 1990s. After a fire, tree growth is delayed or terminated, whereas the plant diversity may be even higher than the diversity of vegetation developing without fire, but it decreases when frequency and intensity of the fire are increasing. Thus, various scenarios may develop depending on the duration since the last fire, fire intensity, and frequency. In the studied fields, these parameters changed from a single fire more than 20 years ago to more than 5 fires after the abandonment of a field with the last fire being 8 years ago. After a single or a few fires which occurred more than 20 years ago, forests with glades dominated by Betula spp. and Salix caprea developed. With increasing fire frequency, the number of trees and coverage of the tree layer decreased. Number of tree individuals in the overstorey on studied fields strongly varied, from 20 to 1333

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Fig. 5.30 This Betuleta nemorosa developed in 30 years on the abandoned ploughed field that was not affected by fire and is located in the Chichin Meadow in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

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Fig. 5.31  Mean number of vascular species of different ecological-coenotic groups per 100 m2 on former arable lands and pastures in the Kaluzhskie Zaseki Reserve. (a) abandoned lands without fires: up to 70 and over 70 m from the border between the old-growth broad-leaved forest and the abandoned ploughed fields; marginal and central parts of abandoned pastures. (b) abandoned arable fields with fire; fields arranged in order of an increased fire affect. Ecological-coenotic groups: Nm nemoral, Br boreal, Nt nitrophilous, Pn piny, Md meadow-edge, and Wt water-marsh groups

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ind./ha. An uneven spatial distribution of tree individuals (single or in groups) ­prevailed on all fields (Fig. 5.28a number 2, c). Betula spp. and Salix caprea dominated; Populus tremula and Tilia cordata sporadically occurred in the overstorey. An undergrowth of all shade-tolerant trees occurred on these fields (Fig. 5.29b). Fraxinus excelsior and Acer platanoides dominated in the field where a single fire happened more than 20 years ago (AF1 in Fig. 5.29b). With the increase in fire frequency, the number of shade-tolerant trees in the understorey decreased; Salix caprea and Betula spp. began to dominate. Pinus sylvestris dominated in the field where more than 5 fires were registered and the last fire had occurred 8 years before the time of data sampling (AF5 in Fig. 5.29b). The number of tree individuals in the undergrowth strongly varied, from 1167 to 37,222 ind./ha. We estimate that fires delayed the development of tree populations for 5 to more than 25 years on the studied fields due to a direct destruction of tree specimens as well as to the postfire development of tall weeds and piny grasses which hamper the establishment of tree seedlings. Composition of the ground layer also depends on fire frequency, intensity, and duration since the last fire. As a result, on abandoned lands affected by fires, a much greater diversity of forest communities, which also differ in species diversity, will develop than on abandoned lands without fire. In the field where the single fire happened more than 20  years ago, shade-tolerant species co-dominated with light-­ demanding plants and a rather high species diversity was registered there (43 species per 100 m2 on average) (AF1 in Fig. 5.31b). With the increase in fire frequency, the number of nemoral species gradually decreased and the number of piny species gradually increased. We recorded the highest mean number of vascular plants (about 50 species per 100 m2) in the field where fires occurred 3 times with the last one between 11 and 15 years ago (AF4 in Fig. 5.31b) and the lowest mean number of species (28 per 100 m2) in the field that burned more than 5 times (AF5 in Fig. 5.31b). Plant diversity on abandoned fields affected by fires probably mainly depends on the degree of postfire soil degradation and on the light conditions as determined by the developing undergrowth. (3) Pastures overgrowing without fire were abandoned in the mid-1980s though a bit of grazing remained till 1992. Two zones were distinguished in the former pastures: the marginal zone where frontal overgrowing was observed and the central zone where meadow vegetation prevailed and single trees or tree groups occurred (Fig. 5.28a number 3, d). A forest dominated by Betula spp. and/or Salix caprea developed in 25–30 years in the zone of 30–80 m wide adjacent to the forest margin; the number of trees varied from 750 to 1400 ind./ha. In the centers of the fields, the number of adult trees varied from 83 to 1104 ind./ha; trees grew singly or in small groups of 1–5 individuals; specimens of 30 years old prevailed (Fig. 5.32). Fraxinus excelsior, Acer platanoides, and Tilia cordata dominated in the undergrowth in the marginal zone of the former pastures (Fig. 5.29c); the total number of trees varied from 27,292 to 106,944 ind./ha; immature specimens prevailed and that partly explains the high number of the individuals there. In the central parts of the fields, the number of individuals in the undergrowth was not high: it varied from 655 to 6150 ind./ha (Fig.  5.29d). Fraxinus excelsior and Acer platanoides dominated under adult individuals of Betula spp.; Quercus robur and Malus sylvestris dominated

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Fig. 5.32  Virginal individuals of Quercus robur in the central zone of the pasture abandoned 30 years ago in the Chichin Meadow in the Kaluzhskie Zaseki Reserve (Photo by M. Bobrovsky)

among the singly growing young trees in the fields. The main feature of overgrowing in the central parts of the former pastures was the simultaneous renewal of all regional tree species including both the light-demanding and the shade-­tolerant tree species. Pinus sylvestris, Quercus robur, Fraxinus excelsior, Acer platanoides, Picea abies, and others together with the fruit trees Malus sylvestris and Pyrus communis were common among the single young individuals occurring in the abandoned pastures. Probably only the presence of bare soil, arising from the burrowing activities of animals, was necessary for the establishment and survival of the tree seedlings. In the ground layer of the vegetation, nemoral species dominated in the marginal zone of the fields and meadow-edge species predominated in their central parts; highest vascular species diversity (50 species per 100 m2) was registered in the central parts (Fig. 5.31a). Among the studied broad-leaved trees, Fraxinus excelsior, Acer platanoides, and Ulmus glabra had the highest height growth rates, on abandoned arable lands as well as on former pastures. Annual height growth averaged 5  cm for immature ­individuals of these species and from 50 to 70 cm for virginal individuals; the maximum annual height growth was 170–180 cm. Tilia cordata was faster than others at its immature stage on former arable lands (increases averaged 15 cm in height per year), but then Tilia cordata lagged behind the rest shade-tolerant species (mean annual height growth was less than 40 cm). On former pastures, Tilia cordata had the same rate of height growth as the other shade-tolerant species: mean values varied from 20 to 45  cm per year. Quercus robur had minimal values of annual

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height growth (from 5 to 10 cm) on the abandoned ploughed fields and in marginal parts of the former pastures. However, in the central parts of the former pastures, height increases of Quercus robur averaged from 40 to 60  cm per year. Overall, Quercus robur built an abundant undergrowth of high vitality in former pastures due to its earlier establishment there compared with the other broad-leaved trees and the absence of competition for light in the central parts of these fields. Our results show that in the absence of fire and in the presence of a stable seed flow of forest plants, about 90 and 80% of the herbaceous species from nearby old-­ growth forest establish on abandoned ploughed lands and pastures, respectively, within 25–30  years after abandonment; all shade-tolerant trees and shrubs also gradually occur in the undergrowth. With fires, forest recovery is delayed on the abandoned arable lands for an undetermined period of time, although plant diversity can be higher than in absence of fire. When frequency and intensity of fire are increasing, the plant diversity begins to decrease. Practically all forest plant species can establish on abandoned agricultural lands within 20–30 years of successional forest recovery. This proves that landscapes with rotation of lands under traditional land use can maintain their forest species. But as the size of cleared areas increases, the forest species diversity probably will gradually decrease. When large tracts of species-rich forests will be cleared at once, the diversity in forest species in the whole region will be gradually reduced.

5.3.6  Conclusion A large area of the Kaluzhskie Zaseki State Nature Reserve is occupied by multi-­ species old-growth nemoral forests dominated by Quercus robur and the shade-­ tolerant broad-leaved trees Tilia cordata, Fraxinus excelsior, Acer platanoides, A. campestre, Ulmus glabra, and U. laevis. All regional broad-leaved tree species occur in the Reserve area. The shrub and field layers of the vegetation are also diverse and contain species of the mesophytic European nemoral forests, such as Euonymus europaea, Festuca altissima, Polygonatum multiflorum, Carex remota, Lunaria rediviva, Galium intermedium, Campanula latifolia, Moehringia lateriflora, Arctium nemorosum, Omphalodes scorpioides, etc., which rarely occur in nemoral forests in European Russia. Numerous spring-growing and -flowering herbs, such as Corydalis marschalliana, C. cava, C. intermedia, Dentaria quinquefolia, D. bulbifera, Allium ursinum, etc., also often occur in the Reserve and often dominate the ground layer in spring. Of great importance for the preservation of nemoral forest species in the Reserve area is the fact that during many centuries, broad-leaved forests covered large tracts of land there. The areas of diverse anthropogenic impacts were relatively small and that formed a favorable combination with the large proportion of forest cover in the region. As a result, nothing prevented the dispersal of forest species once the human impact locally stopped. Moreover, the general recovery of the forest was also promoted because the anthropogenic impacts occurred over relatively small areas.

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At the same time, the Reserve area has an old and diverse history of land use. Direct anthropogenic impacts affected the vegetation and ecosystems up to the proclamation of the Reserve. Therefore practically all plant communities, there are at different successional stages. The oldest successional stage is an uneven-aged multispecies old-growth forest that developed over a long period of spontaneous forest development after the Quercus robur plantings in the eighteenth and nineteenth centuries (Q1 in Fig. 5.12). This is proved by deadwood of different sizes at different stages of decay, well-developed gaps in the canopy and pit-and-mound topography caused by the fall of large trees with uprooting, and a high diversity of plant species. Soils with a thick mull humus horizon with no trace of human impacts, such as ploughing and burning, occur in these forests. The other variants of broad-­leaved forests dominated by Quercus robur and shade-tolerant trees are poorer in structural and species diversity; a gap-mosaic in the canopy and a pit-and-mound topography will be realized there in a course of succession. In forests dominated by Betula spp., Picea abies, and Pinus sylvestris as well as in meadow communities, the successional development is accompanied by an invasion of nemoral trees, shrubs, and herbaceous species that leads to the development of a nemoral herb broad-leaved forest. Our results also showed that, while forests dominated by Quercus robur and shade-tolerant broad-leaved trees hold a large number of vascular species which are not only nemoral, but also meadow-edge and nitrophilous ones, the maintenance of the highest plant diversity in the Reserve is possible only under conditions of a sustainable existence of meadows and water-rich habitats. Probably, that is possible with the presence of herbivores that physically alter habitats, such as Bison bonasus and Castor fiber, within the broad-leaved forest landscape. In the Reserve, for 15–20 years, the vital activities of bison and beaver led to an increasing number of light-demanding meadow and water-marsh species and to the appearance of new plants in the Reserve which are rare species in the region.

5.4  E  ighty Years of Vegetation Dynamics in the Voronezh State Nature Reserve The Voronezh State Nature Reserve is situated in the forest-steppe region, at the border between the Lipetsk and Voronezh regions (number 34  in Fig. 2.1). The Reserve was established in 1923 with the purpose to restore the beaver (Castor fiber) population, which was practically wiped out in its Eurasian distribution area at the beginning of the twentieth century. The area of the Reserve was expanded in 1934 and since then it covers 310 km2. The geographical coordinates of the Reserve are 51.5 to 52.0°N and 39.2 to 39.5°E. The Reserve is located on the border of the Atlantic continental with the continental climatic regions, and accordingly, its climate is of the moderate-continental type with a relatively hot summer and a relatively cold winter. Long-term observations at the

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Reserve’s weather station (Sapelnikova and Bazilskaya 2015) show that the average annual temperature is 5.6°C; the average temperature of July (the warmest month) is 19.5°C, and the average temperature of January (the coldest month) is minus 8.7°C. The average annual precipitation is 638 mm. Most of the precipitation occurs in June–July and it is lowest in February–March. The average height of the snow cover is 50.2  cm; snow lies on average during 122  days. The frost-free season averages 199 days and the vegetation season (with temperatures higher than 10°C) 152 days. According to the temperature regime, the Reserve area belongs to the forest-steppe region, yet the values of the duration of the snow cover period, the thickness of the snow cover, and some other climatic parameters are more like that of the forest region. The Reserve envelops the northern half of the Usmanskiy Pine (Pinus sylvestris) Forest, which is a large “island” of woody vegetation, situated between the Voronezh and Usman rivers at the western edge of the Oka-Don Plain. The area is largely ­situated within the Voronezh River valley and includes the floodplain on the left side and the sandy terraces above the floodplain which were formed in the Quaternary. The thickness of the sand layer varies from 0.5 to 20 m in the Usmanskiy Forest and is up till 8 m in the Reserve. In these sands, there are clay and loam deposits that form waterproof horizons at different depths and these are crucial to retain moisture in these sandy soils. Arenosols and different variants of Podzols dominate (Solntsev et al. 2004). Using a river basin approach 12 landscape units (LUs) were distinguished within the Reserve area. Each LU is characterized by its predominant relief position and its geomorphological and landscape features (Solntsev et al. 2004, 2006; Starodubtseva et al. 2013). The following LUs were identified (Fig. 5.33): 1. The floodplain of the Voronezh River. It has the lowest elevation (90 m asl). A 4 km long segment of the Voronezh River goes through the Reserve. 2. The first terrace above the Voronezh River floodplain. It is located at 5–8  m above the Voronezh River and characterized by loamy streaks lying close to the surface and even cropping out here and there. Swamps and sphagnous bogs occupy large areas there. 3. The western part of the second terrace, 15–25  m above the Voronezh River floodplain. It is located on the right bank of the Ivnitsa River at an elevation of 100–120 m asl. It is a flat sloping plain on deep fluvioglacial and alluvial sands with sandy hillocks, ridges, and shallow hollows. 4. The eastern part of the second terrace above the Voronezh River floodplain. It is located on the left bank of the Ivnitsa River with more aligned relief and a steeper slope to the Ivnitsa River floodplain compared to the prior LU; sand deposits with loamy streaks are denser and less deep (Solntsev et al. 2004). 5. The third terrace, 35–40 m above the Voronezh River floodplain, is characterized by an undulating relief with plenty of damp hollows and depressions surrounded by somewhat higher ground. 6. The flat ledge between the third and fourth terraces above the Voronezh River floodplain is characterized by undulating and gently sloping relief with some depressions and large hillocks.

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Fig. 5.33  Landscape units in the Voronezh State Nature Reserve: 1 the floodplain of the Voronezh River; 2 the 1st terrace above the Voronezh River floodplain; 3 the western part of the 2nd terrace of the Voronezh River; 4 the eastern part of the 2nd terrace of the Voronezh River; 5 the 3rd terrace of the Voronezh River; 6 flat ledge between the 3rd and 4th terraces of the Voronezh River; 7 the 4th terrace of the Voronezh River; 8 floodplains of the Usman and Ivnitsa rivers with remnants of the 1st terraces above the floodplains of these small rivers; 9 sloping-stepped ledge of the Usman River valley; 10 the 2nd terrace of the Usman River; 11 the valleys of tributaries of the Usman and Ivnitsa rivers; and 12 the watershed area between the Usman and Baigora rivers

7. The fourth terrace above the Voronezh River floodplain has the highest elevation in the Reserve: 165–169 m asl. The undulating surface is formed by hilly sands. The layer of sand located above the loamy streaks is 2–5 m thick, reaching up to 6–7 m thick in some hillocks. There are numerous grass and sedge swamps in the depressions due to loamy streaks close to the surface. 8. The floodplains of the Usman and Ivnitsa rivers which are left-side tributaries of the Voronezh River. The hydrological regime of these small rivers is largely determined by dams built by beavers and humans. The floodplain surfaces are complicated by former riverbeds, beaver channels, inflowing streams, and remnants of the first terraces above the floodplains of these rivers. 9. The sloping-stepped ledge of the Usman River valley is characterized by the predominance of gentle slopes as well as slightly concave extensive depressions.

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10. The second terrace above the Usman River floodplain is a narrow band (which is irregular on the right bank) between the wide floodplain and steep slopes of the sloping-stepped ledge of the Usman River valley. Gently sloping flat surfaces are often complicated by low sandy hills, shallow flat depressions and deeper waterlogged pits. 11. The valleys of tributaries of the Usman and Ivnitsa rivers. Two dozen streams located in the Reserve have different water supplies, valley reliefs, and watering regimes that maintain the existence of various ecotopes within this LU. 12. The watershed area between the Usman and Baigora rivers. The predominant elevations are 160–169  m asl. Smoothed surfaces dominate; in some places, they change to hilly elongated formations with a large number of closed depressions, often waterlogged. The Voronezh Reserve was established in an area which was substantially transformed by man. There are remnants of an ancient settlement of the Sarmatian period (the first to second century AD) in the Reserve, and many other settlements have been established near and inside the Usmanskiy Forest since the end of the sixteenth century, when the region was actively colonized by Russians. Forest resources have been intensively exploited since that time. The building of the first Russian navy by Peter I became a period of devastating cuttings accompanied by fires in the Usmanskiy Forest. In the seventeenth century, factories, plants, and watermills appeared in the area together with houses and even settlements, which were erected in different parts of the Forest. More than ten distilleries were built there along with glass works, tanneries, and tar factories. “All this stripped, fast and quickly, the Usmanskiy woodland of its initial wild character; it came to a point when a vast steppe appeared at places where centuries-old trees stood before with no switch at hand to goad the horse. Then a new, even more devastating, woe came to the forest: pasturing. Herds and flocks of livestock were devouring the appearing undergrowth for several decades…” (Usmanskaya… 1851). By the middle of the nineteenth century, the intensive and diverse exploitation of forest lands resulted in a situation in which practically no trees older than 30 years old could be found in the whole area of the Usmanskiy Forest and 75% of the woodland area were covered with forests dominated by Betula spp. (Skryabin 1959). When the State status was granted to the Forest in the middle of the nineteenth century, its protection by armed patrols was organized. After the first forest inventory in 1844, the main task of forest management was the restoration of Pinus sylvestris “on suitable soils”; the first trees were planted at the localities with cuttings, burn-out spots, and abandoned agricultural lands (Skryabin 1959). At the turn of the nineteenth to twentieth centuries, the Usmanskiy Forest belonged to different owners: most of the woodland area had the State status, some lands were private, and there also were forests of settlements and forests of the Tolshevskiy Monastery.

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A part of the Usmanskiy Forest that was excluded in 1934 from economical use contained ecosystems at different (mostly initial) stages of succession after cuttings, fires, and other kinds of anthropogenic impacts. Some parts of forest lands were so strongly disturbed by the earlier cultural activities that in the forest inventory of 1937, they were described as “half-sodded sands with blown-soil pits.” In the first years after the Reserve was proclaimed, the planting of trees (Pinus sylvestris mainly) continued, but on some plots, other species (including introduced ones) were planted as well. There were also cuttings, pasturing, haymaking, and, rarer, ploughing up of cleared plots for vegetable gardens. To help beavers to feed themselves, Salix fragilis was planted along rivers and streams and Populus tremula was cut for fodder. Until the 1960s, logging was carried out in the Reserve (in some years more than 150,000 m3); haymaking took place in an area of 400–600 ha and up to 1400 heads of cattle were pastured (Likhatskiy 1994). In the middle of the 1980s, zoning of the Reserve area was done: a “core area” with a strict regime limiting any impact (about 55% of the Reserve) and a “buffer zone” (the rest of the area) were identified. These zones are maintained until today. However, due to a sharp reduction in the number of private livestock which commenced practically at the same time, haymaking and pasturing became substantially reduced over the entire Reserve area. At present, many fields in the buffer zone are being overgrown with woody vegetation. It also should be noted that the Reserve is situated in a highly developed and densely populated region. The Reserve is surrounded by settlements, the Reserve area is crossed by the trunk railway Voronezh – Moscow, and a high-­ voltage transmission line, and there is a ramified road network. As a result, there certainly is exogenous influence on the ecosystems in the Reserve.

5.4.1  Methods of Investigation More than 1050 phytosociological relevés sampled in the Reserve since 1929 were analyzed and served to describe 80 years of vegetation dynamics in relation to the landscape structure (Starodubtseva et al. 2013). The vegetation was analyzed in 11 LUs: the floodplain of the Voronezh River and the first terrace above the Voronezh River floodplain (numbers 1 and 2 in Fig. 5.33; totalling 9% of the Reserve area) were not analyzed due to lack of phytosociological data, whereas remnants of the first terraces above floodplains of the Usman and Ivnitsa rivers were analyzed as a separate LU (8a). Swamps and bogs mainly located on the 4th terrace of the Voronezh River, on the ledge of the Usman River valley, and on the western watershed (LUs 7, 9 and 12, respectively) also were not analyzed due to lack of data. It should be noted that most of the relevés were sampled along a geobotanical profile that was established in the 1930s. The profile, with a total length of 22 km and a width of 1 km, traverses the area from the east to the west at the widest part of the Reserve and passes through all the analyzed landscape units. All phytosociological relevés were assigned to appropriate LUs and grouped into three periods of time when vegetation was sampled: initial, middle, and modern

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periods of time (1st, 2nd, and 3rd periods) were distinguished comprising, respectively, the relevés sampled from 1929 to 1940, during the 1960s, and from the middle of the 1980s till 2009. Classification of the vegetation sample plots and assessment of the dynamics was done by Starodubtseva and Khanina (2009) and Starodubtseva et al. (2013), respectively, and followed largely the methods described in Sect. 2.5. In addition, ANOVA was used to relate vegetation dynamics to landscape units.

5.4.2  General Description of the Vegetation According to the 1991 and 2013 forest inventory data, Pinus sylvestris, Quercus robur, and Populus tremula forests prevail in the Reserve: in 1991, these species dominated in 32.3%, 29.3%, and 19.3% of the area, respectively; in 2013, these values had changed to 33.2%, 31.3%, and 15.0%. Forests dominated by Betula spp. (B. pendula and B. pubescens) occupied 5.7% in 1991 and 3.7% in 2013. The area dominated by Alnus glutinosa changed from 5.2% in 1991 to 6.2% in 2013. Herbaceous communities on dry, moderately moist, and damp (but not swamped) soils covered 3.0% in 1991 and 2.3% in 2013; swamps occupied 2.2% of the Reserve area in both 1991 and 2013. It should be noted that the Quercus robur area includes areas dominated by other broad-leaved trees such as Tilia cordata, Fraxinus excelsior, Acer platanoides, A. campestre, Ulmus glabra, and U. laevis, which occupy small but ever-increasing areas in the Reserve. Thus, the areas with pioneer communities dominated by Betula spp., Populus tremula and also area of forest glades and meadows decreased in the Reserve, whereas the area dominated by late-­ successional trees increased. (Increase of the Pinus sylvestris area is partly due to a change in dominance of mixed low-density stands with Betula spp. and Populus tremula, but probably it is also due to technical reasons: a more accurate digital technology of forest inventory was used in 2013 that led to changes in the estimates for large polygons.) Pinus sylvestris forests are widespread on the first and second terraces of the Voronezh River and on the second terrace of the Usman River (LU 2, 3, 4, and 10); they occupy large areas on the fourth terrace of the Voronezh River (LU 7) and are absent in floodplains of small rivers and streams (LU 1, 8, and 11); on the other LUs, Pinus sylvestris forests occupy small areas. Forty-five percent of the Pinus sylvestris forests are recorded as plantations of different age, though probably their proportion is much larger and most of the stands were planted with the exception of the areas where the pine renewed naturally after a fire. In more than half of the Pinus sylvestris forests (54% of the area according to the 2013 forest inventory), individuals of between 80 and 120 years old prevail. In 31.6% of the area, individuals of 120–160 years old dominate. Middle-aged forests (with individuals of 40–80 years old) make up 13.1% of the area. Overmature individuals (with trees of more than 160 years old) occur in 1.8% of the area and young trees (up to 40 years old) prevail in 0.5% of the area.

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Fig. 5.34  Centroids and convex hulls from a DCA-ordination of 331 vegetation plots sampled in Pinus sylvestris forests in the Voronezh Reserve. Pn-L Pineta (hylocomioso-)cladinosa, Pn-MdPn Pineta (hylocomioso-)xerophyto-herbosa, Pn-Br Pineta (hylocomioso-)parviboreoherbosa, Pn-NmMd Pineta prato-nemoroherbosa, Pn-Nm Pineta (Pineto-Querceta) nemorosa, and Pn-BrNm Pineta (P.-Querceta) boreo-nemoroherbosa. Radiating lines show the direction and strength of the linear correlations of Tsyganov’s (1983) ecological values with the plots scores: Rc soil reaction, Hd soil moisture, Nt soil fertility (rank values are directly dependent on values of soil parameters), and Lc light availability (rank values range from high light availability to more shady habitats)

The field layer is very diverse: it is dominated by lichens and green mosses, herbaceous species of the piny group, piny and meadow groups, boreal species, nemoral and meadow species, strictly nemoral species, and species of the boreal and nemoral groups together. Green mosses occur in all Pinus sylvestris forests, but their cover differs: it varies from very dense in piny, boreal, and piny-meadow forests to single occurrences in nemoral-meadow, boreal-nemoral, and nemoral stands. The composition of the tree layer also differs: it varies from pure Pinus sylvestris stands, especially in plantations dominated by piny and piny-meadow herbaceous species to a composite structure of the tree layer including broad-leaved trees in nemoral Pinus sylvestris forests. The diverse composition of Pinus sylvestris forests in the Reserve relate to diverse environmental conditions which can change during succession. The ordination analysis (Starodubtseva and Khanina 2009) showed a rather wide variation in vegetation along gradients of light availability and soil fertility and a moderate variation along gradients of soil reaction and moisture (Fig. 5.34).

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Fig. 5.35  Pineta cladinosa with Cladonia spp. and Koeleria glauca in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

The Pinus sylvestris forests were classified into six forest types on basis of the dominance of species of different ecological-coenotic groups in the ground layer (Fig. 5.34). (1) Pinus sylvestris forests dominated by lichens and piny herbaceous species in the ground layer (Pineta (hylocomioso-)cladinosa) (Fig.  5.35) occur only in the western part of the 2nd terrace above the Voronezh River floodplain (LU 3) where they occupy small areas on the tops of sandhills in piny-meadow Pinus sylvestris forests. Poor soil, a large depth of the groundwater table together with frequent fires (coming from outside of the Reserve), and some isolation of this LU from the Reserve forests by the lower reaches of the Ivnitsa River determine the specificity of the species composition of these communities and the delay in their succession. Such forests can occasionally be found nowadays on the 4th terrace of the Voronezh River (LU 7) in localities with frequent fires due to the railway. Pinus sylvestris with a single admixture of Quercus robur forms the overstorey. Chamaecytisus ruthenicus and Genista tinctoria dominate the shrub layer. The lichens Cladonia sylvatica, C. rangiferina, and Cetraria islandica dominate the ground layer; piny grasses and herbs, such as Koeleria glauca, Rumex acetosella, and Peucedanum oreoselinum, often occur. Piny herbaceous species prevail in the field layer and meadow species make up a quarter of the vascular species list

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Fig. 5.36  Ecological-coenotic structure of the vegetation in the community types described from the Voronezh State Nature Reserve. Community types are the same as in Fig. 5.34, 5.39, 5.43, 5.45, 5.47, and 5.49. Ecological-coenotic groups: Nm nemoral, Br boreal, Nt nitrophilous, Pn piny, Md meadow-edge and Wt water-marsh groups

(Fig.  5.36a). The green mosses Dicranum polysetum, Pleurozium schreberi, and sometimes Polytrichum piliferum also often occur in the bottom layer. Green mosses replace lichens during the succession, and as a result, the area occupied by these communities gradually decreases in the Reserve: they occupied 200 ha in the 1930s (Nikolaevskaya 1971) and only 10 ha in the 1991 forest inventory. (2) Pinus sylvestris forests dominated by piny and meadow herbaceous species in the ground layer (Pineta (hylocomioso-)xerophyto-herbosa) are mainly plantations of different age. At the earlier after-planting stages, only Pinus sylvestris forms the one-layer stands; at the later stages, Quercus robur, Betula spp. (often), and Populus tremula or Tilia cordata (rarer) occur in the second sublayer of the overstorey. Chamaecytisus ruthenicus, Sorbus aucuparia, Genista tinctoria, Cerasus fruticosa, and Euonymus verrucosa often occur in the shrub layer; Frangula alnus, Sambucus racemosa, Acer tataricum, and Corylus avellana can also be found. In the field layer, Calamagrostis epigeios, Fragaria vesca, Polygonatum odoratum, Orthilia secunda, and also Rubus idaeus often occur with high abundance. Meadow and piny herbaceous species prevail in the field layer, whereas the proportions of

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boreal and nemoral species are smaller and about equal in size (Fig. 5.36a). As a whole, the ecological-coenotic structure of this community is close to the structure of the lichen and piny herb Pinus sylvestris forests with a smaller proportion of piny species and larger proportions of meadow, boreal, and nemoral species. Green mosses occur in 64% of the relevés; Pleurozium schreberi and Dicranum polysetum dominate; ground lichens can be found. These communities mainly develop from the Pineta (hylocomioso-)cladinosa (Nikolaevskaya 1971). Without fires, piny and meadow herb Pinus sylvestris forests develop into boreal herb pine forest at wetter sites and to nemoral herb pine forest at drier sites (Starodubtseva et al. 2004). At that, the number of species per plot and composition are richer in the transitional community than in the initial and the two subsequent communities (Fig. 5.36a). Fires, depending on their intensity, return the community into a particular preceding stage of the succession. In the first years after fire, Chamaenerion angustifolium, Rumex acetosella, etc. can be abundant. After a fire, Calamagrostis epigeios usually grows vigorously, thereby actively preventing the appearance of a tree undergrowth. In such places, steppe glades with Chamaecytisus ruthenicus can develop. However, recurrent fires maintain the occurrence of the steppe species Potentilla alba, Pulsatilla pratensis, Scorzonera purpurea, Trifolium alpestre, etc.; species of dry Pinus sylvestris forests, such as Koeleria glauca, Helichrysum arenarium, Chimaphila umbellata, Vaccinium vitis-­idaea, Antennaria dioica, Veronica incana, Polygonatum odoratum, Genista tinctoria, Hylotelephium maximum, and Pulsatilla patens; and species of dry meadows, such as Festuca rubra, Peucedanum oreoselinum, Tanacetum vulgare, and Vincetoxicum hirundinaria. At that, many species do not survive under a fire regime; frequent fires gradually degrade the soil properties and finally lead to a decrease in species diversity in the steppe (Iljina 2011). In the LU 3, 4, 7, and 12, piny and meadow herb Pinus sylvestris forests did occur during all periods of observation. However, in LU 5, 6, and 10, they were found only during the first or first two periods; in the later period, succession had changed these forest stands into other types. (3) Pinus sylvestris forests dominated by boreal herbaceous plants (Pineta (hylocomioso-)parviboreoherbosa develop after ground fires on wet and damp areas: in depressions on watersheds, in areas with shallow groundwater tables, on lower parts of slopes to the swamps, and in narrow strips around swamps (Fig. 5.37). These forests were found during all periods of observation in LU 3, 4, 7, 8a, 10, and 12. Besides Pinus sylvestris, Quercus robur, and Betula pendula often occur as an admixture in the overstorey. Frangula alnus, Acer tataricum, Euonymus verrucosa, Salix cinerea, Padus avium, and Sorbus aucuparia often occur in the understorey. In the field layer, boreal species dominate and a quarter of the vascular species consists of piny herbaceous species (Fig. 5.36a). Vaccinium vitis-idaea, Molinia caerulea, and V. myrtillus often dominate. Pleurozium schreberi, Dicranum polysetum, and Polytrichum commune often occur in the bottom layer; Sphagnum spp. can be found on wetter sites. It should be noted that this community, in addition to sphagnum bogs, is a refugium for boreal plants in the Reserve, as it is located close to the southern border of

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Fig. 5.37  Pineta hylocomioso-parviboreoherbosa with Vaccinium mytillus in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

their distribution areas. Therefore the boreal species Vaccinium myrtillus, Maianthemum bifolium, Trientalis europaea, and Orthilia secunda, as well as plants of fresh and wet Pinus sylvestris forests, such as Lycopodium annotinum, L. clavatum, Diphasiastrum complanatum, Vaccinium vitis-idaea, and Calluna vulgaris occurring in these forests, are rare species over the entire Voronezh region. (4) Pinus sylvestris forests dominated by meadow and nemoral herbaceous plants (Pineta prato-nemoroherbosa) are forests in successional transition from piny and meadow herb to nemoral herb Pinus sylvestris forests. They occur in rather small areas practically in all LUs in the Reserve, except on floodplains of small rivers and streams. While Pinus sylvestris dominates, the other tree species, such as Quercus robur, Betula pendula, Populus tremula, or Tilia cordata, often occur in the overstorey and in the second sublayer of the canopy. In the understory, besides the typical species of piny-meadow communities Chamaecytisus ruthenicus, Sorbus aucuparia, and Euonymus verrucosa, the nemoral shrubs Corylus avellana and Rosa majalis often occur. Cerasus fruticosa and Genista tinctoria are less common compared with the piny-meadow Pinus sylvestris communities. Meadow and nemoral herb Pinus sylvestris forests are richest in plant diversity among all Pinus sylvestris forests: meadow-edge and nemoral species are the most prominent species in the ground layer, whereas the number and abundance of piny

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herbaceous species are also high (Fig. 5.36a). Species of fresh and dry meadows, such as Fragaria vesca, Achillea millefolium, Origanum vulgare, and Peucedanum oreoselinum, often occur together with the meadow grasses Brachypodium pinnatum, Elytrigia repens, Festuca rubra, Agrostis tenuis, and Poa pratensis; the steppe species Geranium sanguineum and Poa angustifolia; the nemoral grasses Melica nutans and Brachypodium sylvaticum; the piny grass Calamagrostis epigeios; and the boreal species C. arundinacea and Rubus idaeus. Number and abundance of steppe species are highest in this community among all Pinus sylvestris forests and among all forest communities in the Reserve as well. Green mosses occur in 41% of the relevés. (5) Pinus sylvestris forests dominated by nemoral herbs (Pineta(P.-Querceta) nemorosa) have been described from the Reserve only since the 2nd period of time (from the 1960s). This confirms their successional origin, as does the general increase in nemoral species and decrease in piny and meadow species in the Reserve communities. The Pineta(P.-Querceta) nemorosa occupy small areas over the entire Reserve except the western part of the 2nd terrace of the Voronezh River (LU 3), valleys of tributaries and remnants of the first terraces of the Usman and Ivnitsa rivers (LU 11 and 8a), and the eastern watershed (LU 12). Pinus sylvestris dominates the overstorey with considerable admixture of Quercus robur, Betula pendula, and Populus tremula. The second sublayer of the canopy is well developed and formed by Quercus robur, Acer platanoides, and Tilia cordata and rarer Ulmus glabra and Fraxinus excelsior. Corylus avellana, Acer tataricum, Euonymus verrucosa, Sorbus aucuparia, and Padus avium form the understory. The nemoral species Stellaria holostea, Convallaria majalis, Geum urbanum, Glechoma hederacea, Viola mirabilis, and Aegopodium podagraria often occur with high abundance in the ground layer. (6) Pinus sylvestris forests dominated by nemoral and boreal herbaceous plants Pineta(P.-Querceta) boreo-nemoroherbosa are a transitional forest type from the Pineta (hylocomioso-)parviboreoherbosa to the Pineta(P.-Querceta) nemorosa (Fig.  5.38). These communities have appeared in the Reserve mainly since the 1960s: only few such vegetation plots were described there in the 1930s from the eastern part of the 2nd Voronezh River terrace (LU 4), whereas later such forests occurred in different LUs of the Reserve including the floodplains of the small rivers (LU 8). The overstorey is formed by Pinus sylvestris with an admixture of Quercus robur and Betula spp.; the second sublayer of the canopy is often formed by Quercus robur, Tilia cordata, Acer platanoides, Populus tremula, Betula spp., and Malus sylvestris. Frangula alnus, Acer tataricum, Euonymus verrucosa, E. europaea, Chamaecytisus ruthenicus, Sorbus aucuparia, and Corylus avellana often occur in the understorey. An undergrowth of Tilia cordata and Acer platanoides also occurs. The nemoral and boreal herbaceous plants Molinia caerulea, Carex pilosa, Aegopodium podagraria, Convallaria majalis, and Rubus saxatilis often dominate the ground layer together with the piny species Pteridium aquilinum and Vaccinium vitis-idaea. The nemoral grass Melica nutans; the boreal species Solidago ­virgaurea, Calamagrostis arundinacea, and Rubus idaeus; and the meadow and steppe species

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Fig. 5.38  Pineto-Querceta boreo-nemoroherbosa with Calamagrostis arundinacea, Convallaria majalis, and Rubus saxatilis in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

Stachys officinalis, Fragaria vesca, and Geranium sanguineum often occur. Plant diversity is rather high due to the composite character of the field layer (Fig. 5.36a). Quercus robur broad-leaved forests are mainly located in the central and southeastern parts of the Reserve, in the LUs 6, 7, 9, and 12. Quercus robur mainly dominates among the other broad-leaved trees. According to the 2013 forest inventory, one third of the Quercus robur forests are between 80 and 120  years old; another are 160–200 years old; 18% of the forests are 120–160 years old; and 14% are more than 200  years old. On 4% of the area, individuals of 40–80  years old dominate and young trees (up to 40 years old) dominate only on 0.2% of the area. Forests dominated by Tilia cordata, Fraxinus excelsior, and Acer platanoides occupied 2% of the area covered by broad-leaved forests in 1991 and 7.6% in 2013. At that, Acer campestre, Ulmus glabra, and U. laevis began to dominate in some stands in 2013. Most Acer platanoides and Fraxinus excelsior individuals were more than 40 years old in two thirds of the area in which they dominated; Tilia cordata of more than 20 years old prevails in two thirds of its area of dominance. The ground layer is rather diverse: besides forests dominated only by nemoral herbaceous species, there are Quercus robur forests dominated by nemoral and nitrophilous species, boreal and nemoral species, meadow and nemoral species, and meadow and piny herbaceous species. The diverse composition of these forests indicates the diverse environmental conditions and land-use history in these forests

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Fig. 5.39  Centroids and convex hulls from a DCA-ordination of 217 geobotanical relevés of Quercus robur broad-leaved forests in the Voronezh Reserve. Q-Nm Querceta nemorosa, Q-NmNt Querceta nemoralo-nitrophiliherbosa, Q-BrNm Querceta boreo-nemoroherbosa, Q-MdPn Querceta xerophyto-herbosa, and Q-MdNm Querceta prato-nemoroherbosa. Radiating lines are the same as in Fig. 5.34

(Starodubtseva and Khanina 2009; Bobrovsky 2010). Ordination analysis showed a rather wide variation of vegetation along the gradients of soil fertility and light availability and a weaker variation along the gradients of soil reaction and moisture (Fig. 5.39). The Quercus robur broad-leaved forests were classified into five forest types. (1) Quercus robur forests dominated by nemoral herbaceous species (Querceta nemorosa) have been found in practically all LUs since the 1960s (except the western part of the 2nd terrace of the Voronezh River, LU 3, located on deep sands), whereas at the initial time of observation (in the 1930s), these communities occurred only in the LUs 7, 9, and 10. The canopy is complex and formed by several sublayers dominated by Quercus robur with an admixture of Fraxinus excelsior, Acer platanoides, Tilia cordata, and A. campestre. The understorey is dense and formed by Corylus avellana, Frangula alnus, Acer campestre, Euonymus europaea, E. verrucosa, Padus avium, and Sorbus aucuparia. On the whole, these forests are rather young and only a few large trees have fallen. As a result, gaps in the canopy are absent and light availability at the ground layer is low. Species diversity is also low in these forests and only shade-­tolerant nemoral herbs prevail (Fig.  5.36b). In spring, the spring-growing and -flowering

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Fig. 5.40  Querceta nemorosa in spring with the spring-growing and -flowering species Corydalis marschalliana, C. solida, Anemonoides ranunculoides, and Scilla siberica in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

species Corydalis spp., Anemonoides ranunculoides, and Scilla siberica often dominate (Fig. 5.40). In summer, Aegopodium podagraria, Carex pilosa, and sometimes Urtica dioica dominate (Fig.  5.41); Asarum europaeum, Pulmonaria obscura, Stellaria holostea, Glechoma hederacea, Lathyrus vernus, Pulmonaria obscura, and Viola mirabilis often occur. (2) Quercus robur forests dominated by nemoral and nitrophilous herbs (Querceta nemoralo-nitrophiliherbosa) were described from floodplains of small rivers (LU 8) and their first terraces (LUs 9 and 10) in the first period of time of recording and from tributaries of small rivers (LU 11) and the eastern watershed (LU 12) in the third period of time. These forests developed after cutting in the floodplains (Nikolaevskaya 1971). After cessation of logging Alnus glutinosa begins to dominate and replaces Quercus robur in communities dominated by nemoral and nitrophilous herbs. Quercus robur dominates the overstorey with an admixture of Betula spp., Populus tremula, Alnus glutinosa, and rarer Pinus sylvestris. Frangula alnus, Sorbus aucuparia, Padus avium, Euonymus verrucosa, Tilia cordata, Corylus avellana, and Salix cinerea form the understorey. Humulus lupulus often occurs. The nitrophilous species Filipendula ulmaria, Geum rivale, Deschampsia cespitosa, Ranunculus repens, Lysimachia vulgaris, and Urtica dioica often dominate; the nemoral species

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Fig. 5.41  Querceta nemorosa with Aegopodium podagraria and Urtica dioica in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

Aegopodium podagraria and Carex pilosa often occur in the ground layer. Besides nemoral and nitrophilous species, the number and abundance of meadow-edge and water-marsh species are also high (Fig. 5.36b); the average number of boreal species is also rather high, but their abundance is low (Starodubtseva and Khanina 2009). (3) Quercus robur forests dominated by nemoral and boreal herbaceous species (Querceta boreo-nemoroherbosa) occur in depressions, more often on watersheds (LUs 7, 9, 10, 12, etc.). The overstorey is formed by Quercus robur, Betula pendula, Populus tremula, and Pinus sylvestris (the latter occurred only during the first two periods of time of recording); sometimes Fraxinus excelsior forms the first layer, whereas Tilia cordata and Acer platanoides occur in the second sublayer of the canopy. Frangula alnus, Sorbus aucuparia, Euonymus verrucosa, E. europaea, Padus avium, Acer tataricum, Corylus avellana, and rarer Viburnum opulus occur in the understorey. In the 1930s, Vaccinium myrtillus and Molinia caerulea often dominated the ground layer; Carex pilosa and Aegopodium podagraria often occurred with low abundance. The participation of nemoral species has gradually increased in the field layer. Together with the decrease of Pinus sylvestris in the canopy, this testifies the transitional character of these communities: from boreal and nemoral– boreal Pinus sylvestris forests to Quercus robur forests dominated by nemoral herbs. Since the 1960s, the nemoral species Carex pilosa, Aegopodium podagraria,

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Fig. 5.42  Querceta xerophyto-herbosa in spring with Calamagrostis epigeios and Pteridium aquilinum in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

and Stellaria holostea often dominated together with Rubus idaeus, Pteridium aquilinum, and Calamagrostis canescens. Rubus saxatilis, Maianthemum bifolium, Molinia caerulea, and Convallaria majalis often occur. On the whole, half of the species in these communities consist of nemoral species, while boreal species make up about a quarter (Fig. 5.36b). (4) Quercus robur forests dominated by piny and meadow herbaceous species (Querceta xerophyto-herbosa) (Fig. 5.42) occur over the entire Reserve area except in the floodplains, but they were more common during the first two periods of observation. Presently, they occur only on the flat ledge between the 3rd and 4th terraces of the Voronezh River, on the 4th terrace of this river, on the stepped ledge of the Usman River valley, and on the eastern watershed (LUs 6, 7, 9, and 12). These forests probably developed after selective cutting in forests dominated by Pinus sylvestris with Quercus robur (Nikolaevskaya 1971). For a relatively long time, these communities have been maintained by browsing of wild ungulates and grazing of livestock which both were common in the Reserve till the 1970s (Likhatskiy 1994). After cessation of these impacts, nemoral species began to replace piny and meadow species and the area occupied by these forests began to decrease. Quercus robur dominates the overstorey with an admixture of Betula pendula and rarer Pinus sylvestris and Populus tremula. Cerasus fruticosa, Genista tincto-

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ria, and Chamaecytisus ruthenicus often dominate the understorey; Euonymus spp., Sorbus aucuparia, Acer tataricum, Frangula alnus, Corylus avellana, Padus avium, and Tilia cordata can also be found. The piny and meadow species Calamagrostis epigeios, Pteridium aquilinum, Agrostis tenuis, and Brachypodium pinnatum ­dominate together with the nemoral plants Carex digitata, Stellaria holostea, and Convallaria majalis. The piny herbs Peucedanum oreoselinum, Veronica incana, and Polygonatum odoratum and the boreal species Rubus idaeus often occur. These communities are the richest in species diversity among the Quercus robur forests due to the relatively large number of meadow-edge, piny, boreal, and nemoral species (Fig. 5.36b). (5) Quercus robur forests dominated by meadow and nemoral herbaceous species (Querceta prato-nemoroherbosa) successionally develop from the Querceta xerophyto-herbosa. These forests more often occur in the 2nd and 3rd periods of the observation. They are mainly described from the 3rd and 4th terraces and from the flat ledge between these terraces of the Voronezh River and from terraces of the Usman River and the eastern watershed (LUs 5, 6, 7, 9, 10, and 12). Quercus robur dominates the overstorey with a large admixture of Populus tremula, Betula pendula, Acer platanoides, and Tilia cordata. In the understorey, Euonymus verrucosa, Corylus avellana, Padus avium, and Tilia cordata prevail; Cerasus fruticosa, Genista tinctoria, Chamaecytisus ruthenicus, Euonymus europaea, Sorbus aucuparia, Acer tataricum, and Frangula alnus can be found. The nemoral and meadow plants Aegopodium podagraria, Carex pilosa, Melampyrum nemorosum, Convallaria majalis, Brachypodium pinnatum, etc. dominate in the ground layer; Melampyrum pratense and Glechoma hederacea also often occur. The average number of species per plot is rather high though lower than in the Querceta xerophyto-herbosa due to a decrease in meadow and piny species (Fig. 5.36b). Populus tremula forests occupy now 15% of the Reserve’s area, whereas they covered more than 25% of the Reserve in the 1930s. They often occur in all landscape units except LU 3 where they cover a very small area. These forests develop after the felling of Pinus sylvestris forests and Quercus robur forests that grew under different environmental conditions, and therefore they are dominated not only by nemoral plants in the ground layer (which is typical for Populus tremula forests) but also by boreal, nitrophilous and nemoral, and nemoral with meadow plants. Ordination analysis showed rather the wide variation in the vegetation along gradients of light availability, soil fertility, and moisture (Fig. 5.43). Four forest types were distinguished within the Populus tremula forest: (1) Populus tremula forests dominated by boreal herbaceous species in the ground layer (Populeta parviboreoherbosa) occupy small areas in the Reserve; they developed after felling of the Pineta (hylocomioso-)parviboreoherbosa (Nikolaevskaya 1971). These communities are described from depressions between sandhills on the slopes to the Ivnitsa River (LU 4) and from edges of sedge and sedge-sphagnum bogs (LU 7). Populus tremula dominates the overstorey with a considerable admixture of Quercus robur, Betula spp., and rarely Pinus sylvestris. The understorey is formed by Acer tataricum, Sorbus aucuparia, Frangula alnus,

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Fig. 5.43  Centroids and convex hulls from a DCA-ordination of 189 geobotanical relevés of Populus tremula forests in the Voronezh Reserve. Pp-Br Populeta parviboreoherbosa, Pp-MdNm Populeta prato-nemoroherbosa, Pp-Nm Populeta nemorosa, and Pp-Nt Populeta nitrophiliherbosa. Radiating lines are the same as in Fig. 5.34

rarer Euonymus verrucosa, and Tilia cordata. Boreal species dominate the ground layer with a high abundance, though in species number they are equal, on average, to nemoral plants (Fig. 5.36c). The boreal grass Molinia caerulea often dominates with the boreal plant Rubus saxatilis; sometimes Vaccinium myrtillus dominates. Melampyrum pratense and Maianthemum bifolium often occur. The moss layer sometimes develops with Pleurozium schreberi, Dicranum polysetum, and Polytrichum commune. In these communities, the rare (for the Reserve) species Dactylorhiza fuchsii, Platanthera bifolia, and Lycopodium clavatum are found. (2) Populus tremula forests dominated by meadow and nemoral species in the ground layer (Populeta prato-nemoroherbosa) mainly occur in small patches on the 2nd terrace of the Voronezh River (LUs 3 and 4), on slopes to river floodplains, and on watersheds in different LUs. These forests develop after cutting of Pinus sylvestris and Quercus robur forests dominated by piny and meadow species in the ground layer and were maintained by forest grazing which was common in the Reserve till the 1970s. Ten-year-old Populus tremula forests dominated by meadow and nemoral species in the ground layer and with a high participation of Tilia cordata, Acer platanoides, and Quercus robur in the understorey were also described from the eastern watershed (LU 12) where they developed after a catastrophic windfall that occurred in 1986. Populus tremula dominates the overstorey often with a considerable admixture of Quercus robur and Betula pendula; Pinus sylvestris occurs sporadically. Tilia

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Fig. 5.44  Populeta nemorosa with Aegopodium podagraria in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

cordata, Sorbus aucuparia, Frangula alnus, Acer tataricum, Euonymus verrucosa, Cerasus fruticosa, Chamaecytisus ruthenicus, Genista tinctoria, Corylus avellana, and Padus avium occur in the undergrowth. In the ground layer, the nemoral species Aegopodium podagraria, Carex pilosa, Stellaria holostea, and Viola mirabilis dominate together with the meadow-edge species Elytrigia repens, Brachypodium pinnatum, Dactylis glomerata, and others. Species of the meadow-edge, piny, nemoral, and rarer the boreal ecological-coenotic groups, such as Poa pratensis, Agrostis tenuis, Veronica chamaedrys, Fragaria vesca, Clinopodium vulgare, Calamagrostis epigeios, Brachypodium sylvaticum, Melica nutans, Melampyrum nemorosum, Galium rubioides, Convallaria majalis, Rubus saxatilis, etc., often occur. These communities are the richest in species among the Populus tremula forests; meadow-­ edge and nemoral species co-dominate, both in mean number of species per plot (Fig. 5.36c) and in mean coverage (Starodubtseva and Khanina 2009). (3) Populus tremula forests dominated by nemoral species in the ground layer (Populeta nemorosa) (Fig. 5.44) occur in all LUs of the Reserve except in the western part of the 2nd terrace of the Voronezh River (LU 3). They developed after cutting of the Querceta nemorosa and are the most common Populus tremula forests. Populus tremula dominates with a small admixture of Quercus robur, rarer Betula pendula, Tilia cordata, and solitary Pinus sylvestris. The second sublayer of

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the canopy consists of Acer platanoides, A. campestre, Tilia cordata, Ulmus glabra, and Fraxinus excelsior and rarely Quercus robur, Betula pendula, and Malus sylvestris. The understorey is formed by Corylus avellana, Padus avium, Sorbus aucuparia, Tilia cordata, Euonymus europaea, and E. verrucosa. Nemoral herbaceous species dominate the ground layer (Fig.  5.36c). Carex pilosa and Aegopodium podagraria are common; Stellaria holostea and Urtica dioica often occur with a high abundance; sometimes Brachypodium sylvaticum dominates. Pulmonaria obscura, Asarum europaeum, Glechoma hederacea, Lathyrus vernus, and Viola mirabilis often occur. (4) Populus tremula forests dominated by nitrophilous species in the ground layer (Populeta nitrophiliherbosa) occur at the foot of the floodplain slopes, in riparian areas, and rarely on edges of sedge-sphagnum bogs. They were described from LUs 8, 11, and 9. Populus tremula dominates the overstorey with an admixture of Betula spp., Quercus robur, Alnus glutinosa, and rarer Ulmus laevis. A second sublayer of the canopy is not developed which furthers the improved light availability in these communities. The understorey is formed by Frangula alnus, Acer tataricum, and Salix cinerea; sometimes Padus avium, Ribes nigrum, Ulmus laevis, Viburnum opulus, and Euonymus verrucosa occur. Nitrophilous and water-marsh species, such as Filipendula ulmaria, Carex acuta, C. vesicaria, Deschampsia cespitosa, Phragmites australis, Urtica dioica, etc., often dominate. Lysimachia vulgaris, Cirsium oleraceum, and Humulus lupulus often occur. In some communities, Calamagrostis canescens and Molinia caerulea can be found. Due to the diverse environmental conditions in floodplains, species of different ecological-­ coenotic groups are well presented in the Populeta nitrophiliherbosa and provide a relatively high species diversity (Fig. 5.36c). Betula spp. forests occupy now only 4% of the Reserve and occur sparsely over the area. In the past, these forests were much wider spread: according to the 1844 forest inventory data, Betula spp. forests occupied 75% of the present Reserve area and that was due to widespread clear-cutting and fires (Skryabin 1959). Betula spp. forests develop after cutting, fires, and abandonment of hayfields, so they occur under different environmental conditions and are dominated by boreal, piny and meadow, nemoral and boreal, and nemoral and nitrophilous species. Ordination analysis showed wide variation in the vegetation along gradients of soil fertility, moisture, and soil reaction (Fig. 5.45). Five forest types were distinguished among the Betula spp. forests on basis of domination of species of different ecological-coenotic groups in the ground layer. (1) Betula spp. forests dominated by boreal herbaceous species in the ground layer (Betuleta (hylocomioso-)parviboreoherbosa) (Fig. 5.46) occupy unfertile and rather moist sites mainly formed after fires and cuttings in boreal herb Pinus sylvestris forests. The Betuleta parviboreoherbosa are mainly described from LUs 3, 7, 9, 10, and 12. Betula pendula and B. pubescens dominate the overstorey with an admixture of Quercus robur, Populus tremula, and Pinus sylvestris. Frangula alnus, Sorbus aucuparia, Salix caprea, Viburnum opulus, and Acer tataricum form the understorey. The boreal species Vaccinium myrtillus and Molinia caerulea, the piny grass

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Fig. 5.45  Centroids and convex hulls from a DCA-ordination of 128 geobotanical relevés of Betula spp. forests in the Voronezh Reserve. B-Br Betuleta parviboreoherbosa, B-MdPn Betuleta xerophyto-herbosa, B-NmBr Betuleta boreo-nemoroherbosa, B-Nm Betuleta nemorosa, and B-Nt Betuleta nitrophiliherbosa. Radiating lines are the same as in Fig. 5.17

Fig. 5.46  Betuleta hylocomioso-parviboreoherbosa with Polytrichum commune in the bottom layer in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

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Calamagrostis epigeios and the piny fern Pteridium aquilinum often dominate the field layer. On average, boreal species predominate in the number of vascular plants per plot (Fig. 5.36d) and in coverage. The moss layer is well developed: Polytrichum commune, P. juniperinum, Aulacomnium palustre, and Sphagnum spp. dominate. Sometimes, Lycopodium clavatum and L. annotinum dominate the field layer in Betula spp. forests located in narrow strips on slopes to bogs and depressions within boreal herb Pinus sylvestris forests; various water-marsh plants and the nitrophilous herb Lysimachia vulgaris often occur in such forests. (2) Betula spp. forests dominated by meadow and piny herbaceous species (Betuleta xerophyto-herbosa) are described from a small number of plots mainly located on the 4th terrace of the Voronezh River (LU 7), where these communities developed in small hollows and on slopes, after fire in Pinus sylvestris communities. Betula pendula and B. pubescens dominate the overstorey with an admixture of Quercus robur, Pinus sylvestris, and Populus tremula. Quercus robur, Euonymus verrucosa, Sorbus aucuparia, and Frangula alnus often occur in the understorey. The composition of the ground layer is very heterogeneous: piny species cover on average more than 35% of the ground layer (Starodubtseva and Khanina 2009) though in the number of species per plot, they are more or less equal to meadowedge, nemoral, and boreal plants (Fig. 5.36d). Pteridium aquilinum, Poa pratensis, Agrostis tenuis, Carex pilosa, Calamagrostis arundinacea, C. epigeios, and Rubus saxatilis dominate; Geranium sanguineum, Brachypodium pinnatum, Convallaria majalis, Polygonatum odoratum, Peucedanum oreoselinum, etc. often occur. (3) Betula spp. forests dominated by nemoral and boreal species in the ground layer (Betuleta boreo-nemoroherbosa) are a successional stage between the Betuleta parviboreoherbosa and the Betuleta nemorosa. The total number of species and average number of species per plot increase in these communities together with the proportion of nemoral species (Fig.  5.36d). The Betuleta boreo-nemoroherbosa occurred at the first stages of observation (in the 1930s and 1960s) on the eastern part of the 2nd Voronezh River terrace (LU 4), in floodplains of small rivers, and on remnants of the 1st terraces of these rivers (LUs 8 and 8a). And these forests have been found during the entire time of observation in valleys of tributaries of small rivers (LU 11) and on the 2nd terrace of the Usman River (LU 10). On the 4th terrace of the Voronezh River and on the western watershed (LUs 7 and 12), these forests occurred only at the last period of observation. Betula spp. dominate the overstorey; Populus tremula, Quercus robur, and Pinus sylvestris also often occur. The boreal and nemoral shrubs and trees Frangula alnus, Sorbus aucuparia, Acer tataricum, Quercus robur, and rarer Tilia cordata dominate the understorey. The boreal and nemoral species Molinia caerulea, Carex pilosa, Rubus saxatilis, Convallaria majalis and Maianthemum bifolium and the piny fern Pteridium aquilinum often dominate the ground layer. The rare (for the Reserve) species Dactylorhiza maculata, Orthilia secunda, Platanthera bifolia, and Pyrola rotundifolia occur in these communities just as in the boreal herb Betula spp. forests. (4) Betula spp. forests dominated by nemoral herbaceous plants (Betuleta nemorosa) were described from one plot in the 1930s, whereas later these ­communities began more often to occur and nowadays they are widespread in flood-

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plains of small rivers and their tributaries (LUs 8 and 11); they also occur in the eastern part of the 2nd Voronezh River terrace (LU 4). Betula pendula with an admixture of Quercus robur, Populus tremula, rarer Pinus sylvestris, Acer platanoides, and Alnus glutinosa (in floodplains) form the overstorey. The understorey consists of Sorbus aucuparia, Tilia cordata, Acer campestre, A. tataricum, Frangula alnus, Padus avium, Corylus avellana, Euonymus europaea, and E. verrucosa. Nemoral species prevail in the ground layer, but boreal and nitrophilous species also often occur (Fig.  5.36d). Aegopodium podagraria, Geum urbanum, Glechoma hederacea, Viola mirabilis, Stellaria holostea, Carex pilosa, Rubus saxatilis, etc. often dominate; Urtica dioica, Pteridium aquilinum, Maianthemum bifolium, and others occur. (5) Betula spp. forests dominated by nitrophilous species (Betuleta nitrophiliherbosa) mainly occupy moist and swampy sites in floodplains (LUs 8 and 11). Betula pendula and B. pubescens dominate the overstorey with an admixture of Alnus glutinosa, Populus tremula, Quercus robur, and rarer Salix fragilis and Tilia cordata. Nitrophilous, boreal, and nemoral species, such as Padus avium, Viburnum opulus, Ribes nigrum, Sorbus aucuparia, Frangula alnus, Acer tataricum, Corylus avellana, and Salix cinerea, form the understorey. The nitrophilous and water-marsh species Filipendula ulmaria, Urtica dioica, Thelypteris palustris, Geum rivale, Carex vesicaria, Phragmites australis, and Calamagrostis canescens dominate the ground layer; Cirsium oleraceum, Lycopus europaeus, Glechoma hederacea, Rubus idaeus, Equisetum sylvaticum, Iris pseudacorus, etc. often occur. On the whole, the ecological-coenotic structure of the Betuleta nitrophiliherbosa is similar to the structure of the Populeta nitrophiliherbosa: dominance of nitrophilous species with a relatively high proportion of water-marsh, nemoral, and boreal species (Fig. 5.36d). Alnus glutinosa forests occur in floodplains of small rivers and their tributaries (LUs 8 and 11). Communities dominated by Salix alba and S. fragilis (which were planted for beaver feeding from the 1930s to the 1950s) also occur in the floodplains; presently their structure does not much differ from Alnus glutinosa forests, so they were analyzed together. Three community types were distinguished within Alnus glutinosa forests based on the dominance of species of different ecological-coenotic groups in the ground layer (Fig. 5.47): forests dominated by nemoral and nitrophilous herbaceous plants, by nitrophilous plants, and by water-marsh species. Ordination analysis showed a moderate variation of the vegetation along gradients of light availability and moisture (Fig. 5.47): from darker and dryer nemoral–nitrophilous herb communities to lighter and more moistened nitrophilous herb and then water-marsh communities. Alnus glutinosa forms the overstorey; Populus tremula and Betula pendula sometimes occur. The understorey of all Alnus glutinosa forests is formed by Padus avium, Frangula alnus, Salix cinerea, and Ribes nigrum. In communities dominated by nitrophilous species and nitrophilous and nemoral species, Quercus robur, Acer tataricum, Euonymus europaea, and Sorbus aucuparia also occur in the understorey. Corylus avellana occurs only in nemoral–nitrophilous herb communities. Salix fragilis, Ulmus laevis, Betula pubescens, and Viburnum opulus occur in nitrophilous herb and water-marsh communities.

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Fig. 5.47  Centroids and convex hulls from a DCA-ordination of 58 geobotanical relevés of Alnus glutinosa and Salix spp. forests in the Voronezh Reserve. A-NmNt Alneta glutinosae nemoralo-­ nitrophiliherbosa, A-Nt Alneta glutinosae nitrophiliherbosa, and A-Wt Alneta glutinosae uliginoso-­magnoherbosa. Radiating lines are the same as in Fig. 5.34

(1) Alneta glutinosae nemoralo-nitrophiliherbosa occupy levees and upper parts of floodplains. Due to the absence of long-term flooding, a quarter of the average number of species per plot consists of nemoral plants, whereas half of the species are nitrophilous ones (Fig.  5.36e). The nemoral and nitrophilous species Aegopodium podagraria, Urtica dioica, Impatiens noli-tangere, and Filipendula ulmaria often dominate; Humulus lupulus and Glechoma hederacea often occur. (2) Alneta glutinosae nitrophiliherbosa are the most common among the Alnus glutinosa forests (Fig. 5.48). Half of the species per plot consists of nitrophilous plants, and a third are water-marsh species (Fig.  5.36e). The nitrophilous herb Filipendula ulmaria and the water-marsh species Phragmites australis are common. The nitrophilous herbs Lysimachia vulgaris, Solanum dulcamara, and Urtica dioica and the fern Athyrium filix-femina often occur. Sometimes Carex cespitosa, C. pseudocyperus, C. vesicaria, and Thelypteris palustris dominate. (3) Alneta glutinosae uliginoso-magnoherbosa occupy low-lying areas of floodplains with excess water, depressions with long stagnant water, sites adjacent to the water edges, and shores of ducts created by beavers. Water-marsh and, rarer, nitrophilous species, such as Iris pseudacorus, Filipendula ulmaria, Phragmites australis, Cicuta virosa, Lythrum salicaria, Ranunculus repens, Rumex hydrolapathum, Alisma plantago-aquatica, Naumburgia thyrsiflora, and Caltha palustris, often occur. Water-marsh species make up more than half of the number of species per plot and cover more than 60% of the field layer; nitrophilous species average

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Fig. 5.48  Alneta glutinosae nitrophiliherbosa with Urtica pubescens and Filipendula ulmaria in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

more than a third of the species per plot (Fig. 5.36e) and cover somewhat less than 30% of the layer. Herbaceous communities on dry, moderately moistened, and damp (but not swamped) soils developed after forest clearing by fire and felling before the proclamation of the Reserve. A substantial part of these communities developed after abandonment of ploughed lands. These communities occur under different environmental conditions and include mesophytic, hygrophytic, and xerophytic meadows and forest glades dominated by boreal and nemoral species. An ordination analysis of geobotanical relevés showed a wide variation of vegetation along gradients of soil moisture and fertility (Fig. 5.49); light availability also forms one of the main ecological gradients though it seems to play a clearer role within each community type than in the whole dataset. (1) Xerophytic meadows (Prata xerophyto-herbosa) occupy tops of sandhills and other elevations with a deep groundwater table; they are mainly located in the western part of the 2nd Voronezh River terrace; and they are also described from remnants of the 1st terraces of the Ivnitsa and Usman rivers, the slopes, and valleys of tributaries of these small rivers and, after fires, from the 4th terrace of the Voronezh River (LUs 3, 7, 8a, 9 and 11). Piny and meadow species average about 86% of the species per plot (Fig. 5.36f); about two-thirds of the meadow-edge species are typical of dry meadows and steppes (Fig. 5.50). Steppe species cover up to

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Fig. 5.49  Centroids and convex hulls from a DCA-ordination of 83 gebotanical relevés of herbaceous communities in the Voronezh Reserve. Pr-Br Prata boreoherbosa, Pr-Nm Prata nemoroherbosa, Pr-PnMd Prata xerophyto-herbosa, Pr-Md Prata mesophyto-herbosa, and Pr-Wt Prata hygrophyto-herbosa. Radiating lines are the same as in Fig. 5.34

Fig. 5.50  Prata xerophyto-herbosa with Stipa pennata and Chamaecytisus ruthenicus in the Voronezh State Nature Reserve (Photo by E. Starodubtseva)

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30% of the plots and make up 12% of the species number per plot on average (Starodubtseva and Khanina 2009). The piny and meadow grasses and herbs Calamagrostis epigeios, Peucedanum oreoselinum, Chamaecytisus ruthenicus, Achillea millefolium, Veronica incana and Rumex acetosella often occur. The species of dry Pinus sylvestris forests and steppe grasslands Hieracium pilosella, H. umbellatum, Artemisia marschalliana, Genista tinctoria, Vincetoxicum hirundinaria, Stipa pennata, and Pulsatilla pratensis occur only in these herbaceous communities. The Prata xerophyto-herbosa are richest in species numbers among all herbaceous communities of the Reserve: 184 vascular plants were recorded in a total of 26 vegetation plots. Presently, these communities develop after fire in dry Pinus sylvestris forests when Calamagrostis epigeios begins to grow actively and prevents the restoration of woody vegetation. Cladonia spp. and the mosses Polytrichum juniperinum, Ceratodon purpureus, etc. often occur in those plots. These communities also occur on slopes of railway embankments and on sandy sites along the power line, where in addition to periodic cutting of trees and shrubs grazing was common. However, on the whole, the area with xerophytic meadows decreases in the Reserve due to succession; steppe species become rare and are gradually disappearing (Starodubtseva 2016). (2) Mesophytic meadows (Prata mesophyto-herbosa) occupy well-drained sites which do not experience long-term flooding; forests on these sites were cleared by felling, and subsequently, the meadows were maintained by haymaking. Termination of mowing leads to overgrowing with woody vegetation. Presently, Betula spp. forests develop in such areas. Mesophytic meadows have, on average, the highest number of vascular species per plot (28.7  ±  2.3) of all communities studied in the Reserve. Meadow-edge species dominate and within that group species of fresh meadows are most important; nitrophilous species average 13% (Fig. 5.36f). The grasses of different ecological-coenotic groups Poa pratensis, Phleum pratense, Calamagrostis epigeios, Dactylis glomerata, Deschampsia cespitosa, Bromopsis inermis, etc. often occur together with the herbs Achillea millefolium, Prunella vulgaris, Veronica chamaedrys, Leucanthemum vulgare, Trifolium pratense, T. repens, Fragaria viridis, Ranunculus acris, Plantago lanceolata, Campanula patula, and others. (3) Hygrophytic meadows (Prata hygrophyto-herbosa) are located in floodplains of small rivers; they developed after the felling of floodplain forests and were maintained by grazing. Water-marsh species average 50% of the species per plot; 35% consists of nitrophilous species and 10% of plants of fresh meadows (Fig.  5.36f). The water-marsh plants Lythrum salicaria, Phragmites australis, Calamagrostis canescens, Iris pseudacorus, Carex vesicaria, and Glyceria maxima together with the nitrophilous herb Filipendula ulmaria often occur. Nowadays, hygrophytic meadows become overgrown by Salix spp. thickets or Alnus glutinosa. (4) Glades dominated by boreal herbaceous species (Prata boreoherbosa) develop following intense ground fires in Pinus sylvestris forests dominated by boreal plants in the ground layer. Trees wither after such intense fires, and as a result, glades are formed. Such glades are covered by species of the prefire

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c­ ommunity, such as Molinia caerulea, Solidago virgaurea, Pteridium aquilinum, Vaccinium myrtillus, V. vitis-idaea, Convallaria majalis, etc., together with the typical postfire vascular plants Chamaenerion angustifolium and Calamagrostis epigeios and the mosses Marchantia polymorpha and Polytrichum juniperinum. Species which often grow on bare sands, such as Conyza canadensis, Rumex acetosella, Taraxacum officinale, Galeopsis bifida, Lactuca serriola, Cirsium arvense, C. vulgare, Setaria viridis, etc., also occur. Thus, boreal and piny species occur in equal proportions, and together they average 50% of the species per plot; 30% of the species are meadow-edge plants (Fig. 5.36f). Three to five years after a fire, these glades are covered by Betula pendula or Populus tremula and boreal herb forest communities begin to develop. (5) Glades dominated by nemoral herbaceous species (Prata nemoroherbosa) develop after felling in nemoral herb forest communities. Single adult individuals of Quercus robur sometimes occur in the glades. Euonymus verrucosa and Cerasus fruticosa can be found in the shrub layer. The nemoral plants Stellaria holostea and Convallaria majalis often dominate; Glechoma hederacea and Ranunculus auricomus often occur in the ground layer. The piny species Calamagrostis epigeios and Hylotelephium maximum and the meadow-edge and steppe plants Veronica chamaedrys, Poa pratensis, Achillea millefolium, Galium verum, and Geranium sanguineum also often occur. In spring, the spring-­growing and -flowering species Anemonoides ranunculoides, Corydalis bulbosa, and Scilla siberica often dominate; the rare spring-flowering species Fritillaria ruthenica often occurs together with Gagea minima and Primula veris. Nemoral species average 60% of the vascular species per plot; species of fresh meadows average about 20%, and piny herbaceous plants average 10% (Fig. 5.36f). Thus, 23 forest types dominated by different tree species in the overstorey and different groups of species in the ground layer are described from 923 vegetation plots sampled in the Voronezh Reserve between 1929 and 2004, and 5 types of herbaceous communities are described based on 83 sample plots. There are four other forest types which occur in the Reserve but are not described due to the small number of the relevés that have been surveyed in those forests (Table 5.1). Furthermore, sphagnum forests dominated by Betula pubescens and Populus tremula can be found in narrow strips around rare sphagnum bogs; Betula pubescens is also found inside bogs with a sphagnum quagmire; but those are very rare in the Reserve. Grass and sedge swamps and rarer reed swamps occur in small shallow depressions on watersheds.

5.4.3  Eighty Years of Vegetation Dynamics The relations between the periods of time of observation and the landscape units with the composition and abundance of species in the ground layer of the forest communities were analyzed by nonparametric multivariate analysis of variance perMANOVA (McArdle and Anderson 2001) realized as adonis function in the

5  Nemoral Forests

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Table 5.1  Forest types in the Voronezh State Nature Reserve

Dominant group of species in the ground layer Piny herbaceous species with lichens Meadow and piny herbaceous species (with green mosses) Boreal herbaceous species (with green mosses) Meadow and nemoral herbaceous species Nemoral herbaceous species Nemoral and boreal herbaceous species Nemoral and nitrophilous herbaceous species Nitrophilous herbaceous species Water-marsh herbaceous species

Dominant in the overstorey Quercus robur (and other Populus Alnus Pinus sylvestris broad-leaved trees) tremula glutinosa + − − −

Betula spp. −

+

+

−

−

+

+

−

+

−

+

+

+

+

−

*

+ +

+ +

+ *

− −

+ +

−

+

*

+

*

−

−

+

+

+

−

−

−

+

−

Note: + this forest type is described based on geobotanical relevés; * this forest type is present in the Reserve but is not described from the relevés; − this forest type does not occur in the Reserve

package vegan (Oksanen et al. 2011) in the R software (R Development… 2012) (see details in Starodubtseva et al. 2013). The analysis showed that the contributions of these factors to the variation in the ground layer are significant, but not large: period of observation amounts to 3% and LUs to 19% of the general variation in the vegetation. This indicates that for the current development of the vegetation, the landscape structure of the area is of greater importance for the variation in vegetation than the time parameter. Within each time period, separate univariate perMANOVA were performed to analyze the effects of LUs on the composition and abundance of species (in the ground layer) together with pairwise comparisons of vegetation within different LUs. The analysis showed that in the first period of time eight pairs of LUs (from 55) significantly differed, of which seven pairs concerned the comparison of floodplains of the Usman and Ivnitsa rivers (LU 8) with other LUs. The difference in vegetation between floodplains and other LUs was expected. However, it is interesting that besides floodplains, only LU 3 occupied by Pineta (hylocomioso-)cladinosa and forests mainly dominated by piny and meadow herbaceous species in the ground layer differed significantly from LU 9 which was mainly occupied by forests with a high proportion of nemoral herbs (Fig. 5.51). The other pairs of LUs were not significantly different among themselves. Probably this result was obtained due to insufficient numbers of relevés: only 128 plots distributed over 11 LUs are available for the first time period. Within the second and third periods of time, the number of

0%

10%

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40%

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90%

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0.0

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3/3/3/ 1 2 3 Boreal

5/5/5/ 1 2 3

Nemoral

4/4/4/ 1 2 3 Piny

7/7/7/ 1 2 3

Nitrophilous

6/6/6/ 1 2 3

8a 8a 8a /1/2/3 Meadow-Steppe

8/8/8/ 1 2 3

10 10 10 /1/2/3 Water-marsh & oligotrophic

9/9/9/ 1 2 3

11 11 11 /1/2/3

12 12 12 /1/2/3

Fig. 5.51  Average number of species per plot with standard deviations (a) and mean ecological-coenotic structure of plots (b) in landscape units (LUs) of the Voronezh Reserve for three different periods of time of observation (see text). LUs are the same as in Fig. 5.33 and change from 3 to 12 with the additional LU 8a (remnants of the first terraces above floodplains of the Usman and Ivnitsa rivers). Periods of time change from 1 to 3

b

Average number of species per 100 m2

a

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significantly different LU pairs increased to 34 (62% of all pairs) and 55 (100%), respectively, whereas the numbers of relevés sampled also increased to 324 and 599. However, the finding of a relatively high homogeneity in the ground vegetation in the Reserve in the 1930s can be explained by the high degree of anthropogenic transformation of the vegetation before the proclamation of the Reserve. Meadow, steppe–meadow, and piny herbaceous species prevailed over the entire Reserve area in the first period of the observation; only forests dominated by piny and meadow species in the ground layer (Pinus sylvestris, Quercus robur and Betula spp. forests) occurred in all landscape units of the Reserve, except in the floodplains (Starodubtseva et al. 2013, Table 1). LUs located in the central part of the Reserve and adjacent to each other (LUs 4, 5, and 6) were richest in average number of species per 100 m2 in the first period of observation (Fig. 5.33); species of different ecological-coenotic groups (nemoral, meadow-edge, and partly piny groups) were well presented there (Fig. 5.51b). Over time, the average number of species per plot decreased in all LUs (Fig. 5.51a); to a lesser extent, these processes were also observed in the floodplains (LU 8) and on the western part of the 2nd terrace of the Voronezh River (LU 3). Larger changes were observed between the first and second than between the second and third periods of time (Fig. 5.51a). Total species richness in the area increased over time: 331, 340, and 434 vascular plants were recorded in the geobotanical relevés at the initial, middle, and final periods of the observation, but this result was mainly caused by the increasing number of sample plots. Results of statistic modeling on subsamples of fixed size (Smirnov 2012) showed that there is no evidence to suggest a significant increase in the total number of vascular plants from the 1st to the 3rd period of time. Two univariate ANOVAs performed separately for the proportions of nemoral and meadow-edge species within the plots in the three periods of time (totally for all LUs) showed significant changes in the proportions of these species over time (Table  5.2). A Tukey HSD post hoc test for pairwise comparisons showed that nemoral species significantly changed (increased) between the first and second, and the first and third periods of time, and that meadow-edge species significantly changed (decreased) from the first to the second and then to the third periods of time. Thus, the general dynamics of the vegetation in the Reserve expresses itself in an increase in the number and coverage of nemoral species and a decrease in the number and coverage of meadow-edge species in most of the LUs as well as over the entire Reserve area. In the third period of time of observation, Pinus sylvestris, Quercus robur, Populus tremula, and Betula spp. forests dominated by nemoral herbaceous species in the ground layer were recorded in all LUs of the Reserve with exception of the western part of the second terrace of the Voronezh River located on deep sands (Starodubtseva et al. 2013, Table 1). Our conclusion that the position of the nemoral species over time was strengthened corresponds with the results earlier described on basis of the Reserve’s permanent sample plots (Starodubtseva et al. 2004) and the Reserve’s geobotanical profile (Utekhin et al. 1990). A change from light-demanding species to shade-tolerant species while the fertility of the soil increases represents the main succession trend, and in the

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Table 5.2  Two univariate ANOVAs for the proportion of nemoral and meadow-edge species in the ground layer (for all LUs totally) in three periods of time performed by the function aov in the R software (R Development… 2016); homogeneity of variance was checked by Levene’s test Number of degrees Mean sum Source of variation of freedom of squares Nemoral species** Period of time 2 1.514 Residual 878 0.225 Comparison (pairwise a posteriori tests among periods of time) First versus second First versus third Second versus third Meadow-edge species*** Period of time 2 9.434 Residual 740 0.646 Comparison (pairwise a posteriori tests among periods of time) First versus second First versus third Second versus third

F 6.72

P*