The Effects Of Fire On The Life History Traits Of Tallgrass Prairie Forbs

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THE EFFECTS OF FIRE ON THE LIFE HISTORY TRAITS OF TALLGRASS PRAIRIE FORBS

By

BRADLEY D. ELDER

A DISSERTATION Submitted in fulfillment o f the requirements for the degree

DOCTOR OF PHILOSOPHY

Division of Biology College of Arts and Sciences

KANSAS STATE UNIVERSITY Manhattan, Kansas 2001

Approved by:

Major Professor DR. DAVID HARTNETT

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UMI Number: 3013096

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ABSTRACT The effect o f fire frequency, fire season, and fire temperature on tallgrass prairie plants were studied in three separate but related studies. First, I examined the effect of fire on the life history traits of five species o f tallgrass prairie forbs (Baptisia bracteata,

Oenothera speciosa, Vemonia baldwinii, Salvia azurea, and Solidago missouriensis). The forbs studied here did not exhibit a positive response to any one particular bum frequency, while four o f the five did respond positively to summer burning. There were only two underlying similarities among these five species o f forbs, a lack o f a relationship between percent cover data and sexual reproductive effort and all five forbs behave like satellite species, becoming temporarily locally absent at least once during the last 18 years. Neither fire frequency or fire season produced an overriding influence on plant growth and reproduction. In the second study, I examined what role fire frequency and fire temperature play in altering rhizome development and depth distribution. Rhizome depth was found to be greatest on infrequently burned watersheds. The best predictor o f maximum soil temperature generated by fire was initial soil temperature. Fire frequency did influence rhizome depth, but the differences in rhizome depth were not directly due to lethal fire temperatures. Rhizome and tiller density was highest on frequently burned watersheds, though the probability of tillering was greatest on infrequently burned watersheds. Finally, I study examined the effects o f fire on the tallgrass prairie forb Solidago

canadensis. S. canadensis showed increases in percent cover, genet size, aboveground biomass, reproductive biomass, flower number and sexual reproductive effort (SRE) in

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response to infrequent burning. Mean rhizome number, length, depth, and mass were all significantly greater in sites with low fire frequency. Data indicate that this species is negatively affected by frequent fire, however, sexual reproductive effort was significantly higher in infrequently burned sites, providing no support for the hypothesis that clonally herbs in unfavorable sites “escape” poor conditions though increased SRE.

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TABLE OF CONTENTS

LIST OF FIGURES..................................................................................................................... iii ACKNOWLEDGMENTS..........................................................................................................vi Chapter 1. The Effect o f Fire Frequency and Fire Season on Five Tallgrass Prairie Forbs. ABSTRACT...................................................................................................................................1 INTRODUCTION........................................................................................................................ 3 METHODS................................................................................................................................... 7 RESULTS....................................................................................................................................11 DISCUSSION............................................................................................................................. 17 CONCLUSIONS........................................................................................................................ 28 LITERATURE CITED.............................................................................................................. 30 FIGURE LEGENDS..................................................................................................................35 FIGURES.....................................................................................................................................37 Chapter 2. Fire and Patterns of Rhizome Development and Depth Distribution in the Tallgrass Prairie. ABSTRACT................................................................................................................................42 INTRODUCTION...................................................................................................................... 44 METHODS................................................................................................................................. 48 RESULTS................................................................................................................................... 52 DISCUSSION.............................................................................................................................56 CONCLUSIONS........................................................................................................................ 60 LITERATURE CITED.............................................................................................................. 61

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FIGURE LEGENDS................................................................................................................. 65 FIGURES.................................................................................................................................... 67 Chapter 3. Patterns o f Sexual and Vegetative Reproduction in Solidago canadensis Asteraceae Under Different Fire Frequencies in the Tallgrass Prairie. ABSTRACT................................................................................................................................72 INTRODUCTION......................................................................................................................74 METHODS................................................................................................................................. 78 RESULTS................................................................................................................................... 82 DISCUSSION.............................................................................................................................85 CONCLUSIONS........................................................................................................................ 89 LITERATURE CITED.............................................................................................................. 90 FIGURE LEGENDS................................................................................................................. 93 FIGURES.................................................................................................................................... 95 CONCLUSIONS.......................................................................................................................104

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LIST OF FIGURES Chapter 1.

Figure 1. Percent cover and life history traits for B. bracteata. Analysis for periodic and seasonal bums were preformed separately. Figure 2. Percent cover and life history traits for O. speciosa. Analysis for periodic and seasonal bums were preformed separately. Figure 3. Percent cover and life history traits for V. baldwinii. Analysis for periodic and seasonal bums were preformed separately. Figure 4. Percent cover and life history traits for S. azurea. Analysis for periodic and seasonal bums were preformed separately. Figure 5. Percent cover and life history traits for 5. missouriensis. Analysis for periodic and seasonal bums were preformed separately. Chapter 2. Figure 1. Fire frequency effects on rhizome meristems densities. Different letters denote statical differences (P z 0.05).

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Figure 2. The average temperature for each depth (0.5 cm, 2.0 cm, and 4.0 cm). Different letters denote statical differences (P £ 0.05). Figure 3. Fires produced a range o f responses that were grouped into 4 distinct types. Figure 4. Fuel load was not significantly connected with the maximum fire-generated temperatures in the soil (P = 0.26, R2 0.036). Figure 5. The maximum fire generated temperatures in the soil were inversely related to soil moisture only at the 2.0 cm sampling depth (P = 0.006, R2 = 0.107). Chapter 3. Figure 1. Percent cover of S. canadensis on annually (— ) and 20 (—) year burned watersheds. Figure 2. Life history traits of S. canadensis for different fire frequencies. Figure 3. Clone area (m'2) for S. canadensis on annually, 2-yr, 4-yr, 10-yr, and 20-yr. burned watersheds. Figure 4. Percent o f observations o f S. canadensis in different size classes. iv

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Figure 5. Intraclonal ramet density of S. canadensis on annually, 2-yr, 4-yr, 10-yr, and 20yr. burned watersheds. Figure 6. The number of belowground meristems per ramet by fire frequency. Figure 7. Rhizome depth on annually and 20 year burned watersheds. Letters denote significant differences. Figure 8. Average rhizome length of ramets o f S. canadensis on annually and 20 year burned watersheds (a). Per ramet belowground rhizome biomass o f S. canadensis (b). Figure 9. The average weight of rhizomes per centimeter.

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ACKNOWLEDGMENTS Very few people are fortunate enough to be able to clearly appreciate how much of their success is the result o f those around them. Because o f my handicap (dyslexia) I was told from a very young age that I could not go to college, that I just did not have what it takes to make the grade. While I know that I do, I also know that I simply would not have made in it to a Ph.D. program, let alone graduate, without the help o f many people. It is important that these people be thanked. I will leave the remainder o f this section unspell checked so that those who have helped me follow my dreams may have a greater appreciation o f their accomplishment. It is no small effort on their part that this dissertation reached completion. First, I must thank David Hartnett. I have learned an emince amount from him. I have yet to not gane some new insite into ecology when we have dicused my disertation or other topics in biology. I am profoundly graitful for his pacents and support throughout a tamultous program. I am extremely graitful to my other commettie members, Don Kaufman, Alan Knapp, and Paul Nelson. They have provided constructive crisisim through out my time at Kansas State Univeristy. I would alos like to thank Stephen Thien for serving as my outside chair. I must also thank Jim Reichman for first accepting me to the graduat program. Both Jim Reichman and Chris Smith had a profound impact on my “thinking" about science and evolution. In particular, they shaped my way o f thinking about science when I first arived at KSU. Thanks must also go to Tim Guikema for alowing me time off when other matters were more pressing.

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Gail Wilson’s freindship and unflaging support was invaluable as was her constant construtive criticism o f my work. I was fortunut to be a part o f two labs and enjoyed livley debates and support from both, notably, Becky Burton, Jose’ Harea, Said Damhoureyeh, Emily Benson, Mark McDonald, and Eva Home. My success at KSU was also due in large part to Gretchen Holden and Andrea Blair both o f Disables Student Services. With out the acomidations provided I would ahve been unable to even compleet my first exam at KSU. Two other LD instructors that diserve a lot o f thanks are Marsha Sandals and Phyllis Blevens. Both strugled hard with my instructors so that I might get the accomidations that would allow me to graduate. My undergraduate carere was jump started by Dr. Craig Weatherby. His style, enthouisam, and love of learning continues to einfluance me today and is undoubtibly influanceing my students. A big thank you must go to Mr. Arie, who fostered my eraly intrenist in science. I must thank my Famliey who have been suportive thought out my education. With out their suport I would not have made it out o f highschool. My three sets o f granparents fostered my intrest in geology, biology, and teaching, and set the course I would follow for most o f my life. Finaly I must thank two people who have been wonderful friends throughout my time as a Ph.D. student, Amanda Kuhl and Gail Wilson. Both have kept me sane when things were toughf and were always there when I needed help and usualy without me asking.

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CHAPTER 1

The Effect o f Fire Frequency and Fire Season on Five Tallgrass Prairie Forbs

Abstract The effects of fire frequency and fire season on five species of forbs (Baptisiu bracteata. Oenothera speciosa. I'ernonia baldwinii. Salvia azurea. and Solidago missouriensis) were studied in a tallgrass prairie environment. The forbs present here did not exhibit a positive response to any one particular bum frequency. Baptisia bracteata and S. azurea were favored by frequent burning while f' baldwinii responded positively to 2-yr bum frequencies. Growth and reproduction was highest for O speciosa on infrequently burned treatments. Solidago missouriensis also put more energy into growth on infrequently burned plots but allocated relatively more energy to flowering on frequently burned treatments. The response o f forbs to different seasons of fire produced more consistent trends with four of the five forbs responding positively to summer burning. O. speciosa responded positively to summer bums alone while V. baldwinii and 5. azurea responded positively to summer and spring bums and 5. missouriensis l

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responded positively to summer and fall bums. By contrast Baptisia bracteata responded positively to fall and winter burning. The positive response o f four species to summer burning supports Howe’s assertion that summer fires may have a positive effect on some nondominant species. However, the result o f the summer bums presented here may be confounded by the lower burning frequency of the summer burned treatments. Therefore, generalizations about forb responses to summer bums are tenuous. There were only two underlying similarities among these five species of forbs. First, there was a lack of a relationship between percent cover data and sexual reproductive effort. Second, all five forbs behaved like satellite species by becoming temporarily locally absent at least once during the last 18 years. The two treatment types

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a ■o o Cl 0>) a 5 mm) between the two treatments (Fig. 6). The position of buds and elongated rhizomes was significantly (P < 0.001) deeper in the soil on 20-yr burned watersheds compared to those on annually burned watersheds (Fig. 7). Further, elongated rhizomes of clones on 20-yr bum watersheds were also significantly longer (P < 0.001) (Fig. 8a) and possessed a significantly greater dry weight

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per ramet (P < 0.001) than those of clones on annually burned watersheds (Fig. 8b). However, rhizome thickness or provisioning (as estimated by the grams per centimeter of rhizome) did not differ significantly (P = 0.23) between clones on annually burned watersheds and those on 20-yr burned watersheds (Fig. 9).

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Discussion Fire frequency strongly influenced patterns of sexual reproduction and vegetative reproduction in Solidago canadensis. This species is clearly negatively affected by annual burning, as measures of ramet growth, sexual reproduction and vegetative reproduction were greater in sites with lower fire frequency. Similarly, mean clone (genet) size and total percent cover of S. canadensis were greater on infrequently burned sites relative to annually burned sites. Despite the large reductions in plant performance and population abundance with increasing fire frequency, viable S. canadensis populations nonetheless persisted after more than 30 years o f annual spring burning. There was no evidence in this study that S. canadensis increased its energy allocation to sexual reproduction in unfavorable (annually burned) sites as an adaptation to "escape" to more favorable sites via increased seed production and dispersal. In fact, the opposite trend of greater sexual reproductive effort (SRE) in infrequently burned sites was observed. It was impossible to directly measure vegetative reproduction effort in this study as peak rhizome production for S. canadensis occurs in late fall after much o f the aboveground vegetative biomass had senesced and fallen to the ground. Thus, calculating vegetative reproductive effort (rhizome biomass total ramet biomass) was not possible. Therefore, relative shifts in proportional allocation to vegetative reproduction and sexual reproduction remain unclear. However, as with flower number and reproductive biomass, ramets on 20 year burned watersheds produced more rhizomes with greater biomass then ramets on annually burned plots. Overall, annual burning had a proportionally greater negative effect on seed

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reproduction than on rhizome production. Thus, these general trends suggest that the primary strategy o f S. canadensis for coping with frequent (e.g. annual) fire, is not to divert a larger proportion of its resources to increased seed production and escape via dispersal, but rather to survive and persist over time by maintaining belowground resources in rhizomes and regenerating ramet populations each season via vegetative reproduction. Clones on sites burned at 10-yr intervals exhibited no significant difference in mean genet size compared to genets on annually and bi-annually burned watersheds. Thus, the small mean genet size in the sites bums at 10-year intervals may be explained by a high density of very small genets newly established on those sites. It is possible that the conditions for seedling establishment may be much more favorable on that site exposed to a 10-yr fire frequency as compared to four-year burned sites. Despite the shifts in population structure, the differences in SRE. and the differences in clone size, intra-clonal ramet density was remarkably stable and exhibited no significant difference between burning treatments. That is. the production o f shorter rhizomes on annually burned sites did not result in a change in intra-clonal ramet density. This supports the idea that intraclonal ramet density for many clonal plants is genetically some optimal level and is independent of environmental variables (Briske 1991). Further, as the average number of belowground rhizome meristems per m‘ was greater than the -i

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average number o f established ramets per n r for both annually (58 ramets per m ' and 232 rhizomes per m: ) and 20 year (58 ramets per n r and 348 rhizomes per m; ) burned sites. S. canadensis populations do not appear to be meristem limited.

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While ramet density was similar between treatments, the number o f meristems per ramet was not. Plants on 20 year burned sites had more belowground meristems per ramet than did plants on annually burned sites. Interestingly, this was due to the difference in the number o f elongated rhizomes (rhizomes greater than 5 mm) as there was no difference in the number o f rhizome buds (rhizomes less than 5 mm) between annually and 20 year burned watersheds. The similarity in bud number but not in elongated rhizome number may indicate a genetically predetermined size to the bud pool per ramet. Rhizome Depth: McLean (1969) proposed that plants with deeper rhizomes should be favored over those plants that have shallow rhizomes in fire prone habitats. Contrary to McLean’s (1969) hypothesis. Elder (chapter 2 this volume) observed that plants communities in the lowlands o f the KPBS had deeper rhizomes when exposed to lower fire frequencies than when exposed to higher fire frequencies. It was proposed that this result could be explained by species-specific rhizome depth patterns coupled with differences in species composition between environments that are exposed to different fire frequencies. That is. species which were favored by low fire frequencies, tended to have deeper rooted rhizomes than did species that were favored by high fire frequencies. In the present study S canadensis also had deeper rhizomes on infrequently burned watersheds as compared to those on frequently burned watersheds. Thus, community composition cannot be the sole explanation for deeper rhizomes on infrequently burned watersheds. The benefit o f deeper rhizomes however is not clear. Elder (chapter 2 this volume) demonstrated that fire temperature is not a factor for the selection o f deeper

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rhizomes. Differences in nutrient resources between frequently and infrequently burned watersheds have been demonstrated for both soil moisture and nitrogen availability (Anderson. 1965: Knapp et al. 1998). Soil moisture and nitrogen were higher on infrequently burned watersheds as compared to annually burned watersheds. It is unlikely that rhizomes would be influenced by any differences in nutrient availability as rhizomes generally are not involved in the uptake of nutrients. Further, is unclear what advantage would be gained by having rhizomes deeper in a high moisture/nitrogen rich soil. Vleyer and Bernhard (1999) and Sumerford et al. (2000) demonstrated that rhizome length was a good indicator of the probability that a rhizome would become an established ramet. The length of a rhizome then is an indication of parental provisioning of daughter meristems. If rhizome length is the product o f parental energy investment in future daughter ramets. then deeper rhizomes will also need to be longer rhizomes as increasing the depth will require additional energy to reach the soil surface. Because of the high litter buildup that occurs in the tallgrass prairie on infrequently burned sites, light availability at the soil surface is decreased (Knapp 1986). This effectively increases the distance that an emerging ramet'shoot will have to grow in order to reach sunlight. Thus, rhizomes on infrequently burned watersheds may require more energy than rhizomes at the same depth on an annually burned watersheds and thus these rhizomes should be longer. Though this accurately describes rhizomes of 5. canadensis on annually and 20 year burned watersheds, it does not explain the benefit of a shallowly or deeply placed rhizome found in the two bum treatments.

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Conclusions Solidcigo canadensis, a clonal perennial herb, was significantly influenced by fire frequency. Population responses are driven by the fire's effect on both sexual and vegetative reproduction. Belowground demography responses to fire frequency are particularly important and understanding watershed population responses as recovery from fire occurs via rhizomes.

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Literature Cited Abrahamson. W. G. 1980. Demography and vegetative reproduction. In: Solbrig 0 . T. [eds.] Demography and evolution in plant populations. Blackwell Scientific Publications. Oxford. 89-106. Anderson. K. L. 1965. Time of burning as it affects soil moisture in ordinary upland bluestem prairie in the Flint Hills. Journal of Range Management 18:311-316. Ashmum. J. VV.. R. L. Brown, and L. F. Pitelka. 1985. Biomass allocation in Aster acuminatus: variation within and among populations over 5 years. The Canadian Journal of Botany 63:2035-2043. Briske D. D. 1991. Developmental morphology and physiology of grasses. In: Heitschmidt. R. K. and Smith. J. \V. [eds.] Grazing management: an ecological perspective. Timber Press. Portland. Oregon. USA. Pp. 85-108. Douglas. D. A. 1981. The balance between vegetative and sexual reproduction of Mimulus primuloides (Scrophulariaceae) at different altitudes in California. The Journal of Ecology 69:295-310. Elder (chapter 2 this volume) Freeman. C. C.. and L. C. Hulbert. 1985. An annotated list of the vascular flora of Konza Prairie Research Natural Area. Kansas. Transactions of the Kansas Academy of Science 88:84-115. Glenn-Lewin. D. C.. L. A. Johnson. T. W. Jurik. A. Akey. M. Leoschke. and T. Rosburg. 1990. Fire in Central North American grasslands: vegetative reproduction, seed germination and seedling establishment. In Collins. S. L. and L. L. Wallace [eds.]

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Fire in North American tallgrass prairies. 28-45. University o f Oklahoma Press. Norman. Harper. J. L. and J. Ogden 1970. The reproductive strategy o f higher plants I. The concept of strategy with special reference to Senecio vulgaris L. The Journal of Ecology 58(3): 681-98. Hartnett. D. C. 1987. Effects of fire on clonal growth and dynamics o f Pityopsis graminifolia (Asteraceae). The American Journal of Botany 74( 11): 1737-1743. Hartnett. D. C. 1991. Effects of fire in tallgrass prairie on growth and reproduction of prairie coneflower (Ratibida columnifera: Asteraceae). The American Journal of Botany 78(3):429-435. Hartnett. D. C. 1993. Regulation of clonal growth and dynamics o f Panicum virgatum (Poaceae) in tallgrass prairie: effects o f neighbor removal and nutrient addition. The .American Journal of Botany 80(10): 1114-1120. Holler. L. C. and W. G. Abrahamson. 1977. Seed and vegetative reproduction in relation to density in Fragaria virginiana (Rosaceae). The American Journal of Botany 64(8): 1003-1007. Knapp. A. K. and T. R. Seastedt. 1986. Detritus accumulation limits productivity of tallgrass prairie. Bioscience 36(10):662-668. Knapp. A. K.. J. M. Briggs. D. C. Hartnett, and S. C. Collins [eds.]. 1998. Grassland Dynamics: long-term ecological research in the tallgrass prairie. Oxford University Press. New York. NY. McLean. A. 1969. Fire resistance o f forest species as influenced by root systems.

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Journal of Range Management 22(2): 120-122. Meyer. A. H. and S. Bernhard 1999. Experimental demography of rhizome populations o f established clones o f Solidago altissima. The Journal o f Ecology 87(1): 42-45 Ogden. J. 1974. The reproductive strategy of higher plants. The Journal of Ecology 62:291-324. Sumerford. D. V.. W. G. Abrahamson. and A. E. Weis 2000. The effects of drought on the Solidago altissima-Eurosta solidaginis-natural enemy complex: population dynamics, local extirpations, and measures o f selection intensity on gall size. Oecologia 122(2):240-248. Winn. A. A. and L. F. Pitelka. 1981. Some effects o f density on the reproductive patterns and patched dynamics of Aster acuminaius. The Bulletin of the Torrey Botanical Club 108(4):438-445.

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Figure Legends Figure 1. Percent cover of S. canadensis on annually (— ) and 20 (— I year burned watersheds. Percent cover has increased on 20 year burned watersheds throughout the 15 years of this study while percent cover has remained relatively constant on annually burned watersheds. The initial low starting value is likely due to the burning history prior to 1983.

Figure 2. Life history traits of 5. canadensis for different fire frequencies: mean ramet height (A), aboveground ramet biomass (B >. number of flower heads per ramet (C). reproductive biomass (D). SRE 1 (E). and SRE 2 (FI. Letters denote significant differences. Error bars represent = SE.

Figure 3. Clone area (m'2) for S. canadensis on annually. 2-yr. 4-yr. 10-yr. and 20-yr. burned watersheds. Letters denote significant differences. Error bars represent = SE.

Figure 4. Percent of observations of 5. canadensis in different size classes.

Figure 5. Intraclonal ramet density o f S. canadensis on annually. 2->t. 4-yr. 10-yr. and 20-vr. burned watersheds. Letters denote significant differences. Error bars represent ± SE. Figure 6. The number of belowground meristems per ramet by fire frequency. Meristems

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were classified as buds if they were < 5 mm and > 0.05 mm in length, while meristems were classified as rhizomes if had attained a length greater than 5 mm. Meristems = 0.05 mm were not counted. Letters denote significant differences between meristem classifications (bud. rhizome, and total). Error bars represent = SE.

Figure 7. Rhizome depth on annually and 20 year burned watersheds. Letters denote significant differences. Error bars represent = SE.

Figure 8. Average rhizome length o f ramets o f S. canadensis on annually and 20 year burned watersheds (a). Per ramet. belowground rhizome biomass of S. canadensis (b>. Letters denote significant differences. Error bars represent = SE.

Figure 9. The average weight o f rhizomes per centimeter. Letters denote significant differences. Error bars represent = SE.

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1 yr

1 yr 2 yr 4 yr 10 yr 2 0 yr

10 yr 20 yr

96

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Figure 3.

Clone

Area

(IVT )

600

400

200

1 yr

2 yr

4 yr

10 yr

2 0 yr

97

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Figure 4.

P ercent of O b s e rv e d

100

100

0

>

5CS) 50

50 o 0

25

25

0

CL

0

0

700

1400

2100

2800

roo

Area (m ' 2 )

1400

2100

2800

2100

2800

Area (m ' 2 )

100

P e rc en t of O bserved

4 yr 75 0

>

0