Piedmont Alluvial Vegetation: Classification, Geographic Variation, and Restoration
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Piedmont Alluvial Vegetation: Classification, Geographic Variation, and Restoration Elizabeth Rainey Matthews A dissertation submitted to the faculty of the Univeristy of North Carolina at Chapel Hill in partial fulfillment of the requirements of the degree of Doctor of Philosophy in Ecology in the Curriculum for the Environment and Ecology Chapel Hill 2011 Approved by: Robert K. Peet Alan S. Weakley Thomas R. Wentworth Peter S. White James S. Clark © 2011 Elizabeth Rainey Matthews ALL RIGHTS RESERVED ii Abstract Elizabeth Rainey Matthews Piedmont alluvial vegetation: Classification, geographic variation, and restoration (Under the direction of Robert K. Peet) Riparian ecosystems are home to diverse and highly productive plant communities, long known to be among the more species-rich terrestrial communities. However, few pristine riparian systems remain, particularly in North America. Due to their ecological significance and their current imperiled status, there is substantial interest in conservation and restoration of riparian habitat in the Southeastern United States. Successful conservation and restoration require detailed information regarding the composition and structure of natural floodplain plant communities, in addition to an understanding of the environmental drivers associated with compositional variation. While southeastern alluvial vegetation has been well-studied, most studies have focused on the larger rivers of the Coastal Plain region, rather than the relatively smaller streams of the topographically more complex inland Piedmont. In fact, there is relatively little documentation or understanding of Piedmont bottomland vegetation in North Carolina or elsewhere on the Southeastern Piedmont. This dissertation advances our understanding of Piedmont alluvial vegetation by documenting and describing vegetation patterns and environmental drivers in this system. This work provides the vital information that is necessary both for successful management of alluvial habitat and for restoration of degraded alluvial vegetation. As part of this work, I sampled high-quality alluvial vegetation in five North Carolina river basins: the Catawba, iii Yadkin-Pee Dee, Cape Fear, Neuse, and Tar-Pamlico. As a first step towards advancing our understanding of these systems, I developed a vegetation classification of the Piedmont alluvial plant communities in North Carolina. I expect this classification will provide guidance for revising Piedmont alluvial plant community concepts currently recognized in the U.S. National Vegetation Classification. I also explored the spatial distribution of plant species richness across the Piedmont riparian landscape and examined compositional variation in a metacommunity context, quantifying the relative influence of niche-processes and dispersal-processes in shaping riparian plant community composition. I found that niche- processes are dominant in this system, with environmental variables explaining more variation in community composition than spatial structure. Finally, I developed an approach for using quantitative vegetation descriptions to develop reference information for riparian restoration efforts. Because these communities are strongly structured by environmental variables, I was able to develop a matching tool to link restoration sites to described vegetation types based on environmental similarity. In all, I expect the work described in this dissertation to improve management and restoration outcomes for alluvial plant communities in the North Carolina Piedmont. iiiiv Acknowledgements Many individuals and organizations supported both the research and the writing of this dissertation. First, I would like to thank the members of my committee for their guidance, encouragement, and helpful feedback throughout this process. I would like to thank my co-advisors, Robert Peet and Alan Weakley, for their invaluable advice and insight from the very beginning of this project; their knowledge of North Carolina vegetation is unmatched, and I am extremely grateful to have learned so much from them about the flora and natural history of North Carolina. I would also like to thank Tom Wentworth, Peter White, and Jim Clark for their helpful comments and constructive feedback from the early stages of developing my ideas through the completion of this dissertation. I thank the many individuals and institutions that provided logistical and financial support. First and foremost, I would like to thank my three fabulous field assistants, Jessie Outz, Jose Zúñiga, and Megan Faestel, who worked long, hot summer days with me in poison-ivy and insect infested Piedmont bottomlands-- and still kept their cool. I could not have completed this project without their hard work and companionship! Many private organizations, land owners, and land trusts granted permission to access privately owned alluvial forests, including Lislott Harbets of Allison Woods, the Triangle Land Conservancy, the Land Trust for Central North Carolina, the Piedmont Land Conservancy, and the Catawba Land Conservancy. I would also like to thank Bruce Sorrie, Richard LeBlond, and Michael Schafale of the North Carolina Natural Heritage Program. Bruce and Richard were v invaluable resources in identifying pressed plant specimens. Bruce and Michael suggested many high-quality alluvial forests for sampling, which I never would have located without their guidance. Michael Schafale also offered extremely helpful insights on Piedmont alluvial systems and vegetation, gained from many years of field experience, in addition to offering feedback at many junctures in the development of the vegetation classification. The North Carolina Ecosystem Enhancement Program (NC-EEP) funded three years of this research, and financial support from the Society of Wetland Scientists and North Carolina Beautiful improved the quantity and quality of data I was able to collect. The University of North Carolina, the Curriculum for the Environment and Ecology, and the Department of Biology also provided funding in the form of fellowships and teaching assistantships to support my work. I also want to acknowledge and thank my fellow students, friends, and Chapel Hill family, all of whom supported the completion of this work. The UNC Plant Ecology Lab was always a major source of support, both intellectually and socially. In particular, I would like to thank Forbes Boyle, Brenda Wichmann, Jackie White, Kyle Palmquist, Megan Faestel, Brooke Wheeler, Sam Tessel, Michael Lee, Stephanie Seymour, Bianca Lopez and Peter Wilfahrt for their friendship and for being an endless source of fun around Coker. It was on PEL excursions that I first experienced many NC landscapes and vegetation types (pocosins, long-leaf pine, the Sandhills, coastal fringe, and more). I learned much about the NC flora with PEL, in addition to developing important skills related to analyzing and organizing vegetation data in lab meetings. I would also like to thank the Talikoff family for being an important part of my Chapel Hill family; over the last few years, Kim and Alex have been vi my biggest supporters and cheerleaders, and Meg and Lu were experts at distracting me from the stresses of graduate school and reminding me to enjoy each day. Above all, I want to thank my family. My closest friend and roommate for much of my adult life, Chrissie Norton, is a major source of joy and laughter in my life, and she is my favorite, often much-needed and always super-fun, distraction from school. She helped me get through three field seasons in the North Carolina Piedmont (poison ivy, ticks, and more!) and was always there with the emotional and social support I needed throughout my graduate school experience. My boyfriend and favorite botanizing-exploring-socializing-relaxing partner, Jose Zúñiga, not only shared a field season with me, but is my only family member that can provide the “scientist” perspective. He supported and encouraged me to push through to the end of my graduate work many times, and his encouragement always means so much because I know he understands many of the frustrations and difficulties I have confronted. Last, but certainly not least, I want to thank my parents and sisters, who I think are the most wonderful people alive; their unconditional love and support is the inspiration for everything I do. vii Table of Contents List of Tables ......................................................................................................................... xii List of Figures ....................................................................................................................... xiii Chapter 1. Introduction: Piedmont brown-water alluvial vegetation...................................... 1 Introduction ............................................................................................................... 1 Chapter Summaries ................................................................................................... 4 References ................................................................................................................. 7 2. Classification and description of alluvial plant communities of the Piedmont region, North Carolina, U.S.A. .............................................................. 10 Abstract .................................................................................................................... 10 Keywords ................................................................................................................