ABSTRACT SZAKACS, ALEXANDRIA DIANE. Using Multiple Approaches to Explore the Past and Present of “Piedmont Prairie” Vegetation. (Under the direction of Dr. Alexander Krings and Dr. William Hoffmann). Historical records and paleontological evidence suggest the eastern Piedmont of North America, a currently heavily developed and otherwise forested region, once had areas of grassland, savanna, and/or woodland that were characterized by shade-intolerant native heliophytes. Naturally open areas of the landscape were almost entirely lost following European settlement of the region due to changes in land use and disruption of historical fire regimes. Because some of the remnant heliophytes are midwestern prairie disjuncts (e.g., Silphium terebinthinaceum), or southeastern endemic congeners of prairie-affinity genera (e.g., Echinacea laevigata), the term “Piedmont prairie” has become a popular name for this vegetation type. Remnant prairie-affinity flora now largely persist in human-maintained open areas, such as roadsides and utility right-of-ways. Such marginal existence of a once-common ecosystem is cause for concern, so conservation and restoration of Piedmont prairie vegetation are now receiving much attention. Several impediments to successful conservation and restoration exist. For example, the historical distribution and composition of this vegetation type(s) is uncertain, and so few high-quality remnants remain that it is difficult to formulate clear goals for conservation and restoration. This work uses multiple approaches to better understand Piedmont prairie vegetation. We explored the potential utility for historical vegetation reconstruction in the Southeast using phytoliths, silica plant microfossils. To this end, we created the first comprehensive reference collection of phytoliths produced by 28 species of eastern North American conifers (Chapter 1). While we did not find clear distinctions between species or between most genera we sampled, we did document at least one phytolith type that was characteristic of Pinaceae; future studies using higher magnification to study phytolith surface features seem promising. We then compiled a carefully selected 1300-plot dataset from the Carolina Vegetation Survey database, the largest database of regional vegetation plots, to assess the shade-tolerance of regional herbaceous species by proxy of their association with open, semi- open, and closed habitats (Chapter 2). We identified 141 (17% of herbaceous species in our dataset) heliophytes associated with very open habitats (canopy cover <25%), and only 81 (10%) very shade-tolerant species associated with closed habitats (canopy cover >75%). We examined a series of vegetation surveys that took place over 25 years in a putative Piedmont prairie remnant (Picture Creek Diabase Barrens located in Granville County, North Carolina) in order to assess how rare heliophytes, such as Echinacea laevigata, and associated vegetation are responding to differences in management (Chapter 3). We found that vegetation in the monitoring plots has been very forest-like during the last 25 years (most of this time under fire suppression), but recent (2017) prescribed fire is shifting vegetation toward a more open, pine- woodland structure with increasing herbaceous understory. Finally, we used a 195-plot subset of the 1300-plot Carolina Vegetation Survey dataset to characterize and better define the major types of Piedmont heliophilic vegetation through multivariate analyses (Chapter 4). Using hierarchical clustering, partition optimization, and nonmetric multidimensional scaling ordination, we identified and characterized 12 major types of Piedmont heliophilic vegetation, which we organized into five larger groupings: Piedmont Oak-Hickory and Red Cedar Woodlands, Piedmont Glades, Piedmont Pine Woodlands, Piedmont Savannas and Grasslands, and Piedmont River Terrace Glades. We found plots traditionally refered to as “Piedmont prairie” formed a compositionally distinctive cluster characterized by the abundance of heliophytes such as Oenothera fruticosa, and Silphium terebinthinaceum. © Copyright 2020 by Alexandria Diane Szakacs All Rights Reserved Using Multiple Approaches to Explore the Past and Present of “Piedmont Prairie” Vegetation. by Alexandria Diane Szakacs A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Plant Biology Raleigh, North Carolina 2020 APPROVED BY: _______________________________ _______________________________ Alexander Krings William Hoffmann Committee Co-chair Committee Co-chair _______________________________ _______________________________ Thomas Wentworth James Mickle _______________________________ Gary Blank BIOGRAPHY Alexandria Szakacs grew up in Warren, Ohio. She developed a love and appreciation of nature at a young age, and her parents encouraged her interest in science. She attended Youngstown State University (YSU) where she met Professor Carl Chuey, who invited her to work in the Youngstown State University Herbarium and inspired her to pursue the study of Plant Systematics and Field Botany. After earning a Bachelor’s in Biology at YSU, she moved to Raleigh, North Carolina and joined the Plant Biology Graduate Program at North Carolina State University to pursue a Doctorate studying the ecology of native prairie plants. ii ACKNOWLEDGMENTS Thank you to everyone who helped and supported me on these projects. I must give special thanks to Dr. Alexander Krings for your constant support and contagious enthusiasm and to Dr. Tom Wentworth for sharing your endless wisdom and insights. Thank you to Dr. Bill Hoffmann for always asking pointed questions and to Dr. Jim Mickle for your encouragement. Thank you to Dr. Gary Blank for changing the way I think about the history of our landscape and how that history continues to shape the present. I also thank the faculty and support staff of the NCSU Plant Biology department. Your day- to-day support and assistance keeps us all moving forward. I also thank Rachel Clark, Larry Blanton, and Chad Jordan for being so important to my experiences as a teaching assistant. Thank you to the undergraduates Chase Joyner, John Knight, and Athena Giavasis who helped with some of the field and lab work. Thank you to the professionals who shared reports and site information, and, especially, to Erin Jones, Cecil Frost, and David Schnake for sharing your notes and insights for Picture Creek Diabase Barrens. Thank you to my friends and family, whose love and support continues to inspire and encourage me. Thank you to Diane Szakacs for always being a wonderful mother. Thank you to Mark Bryant, my fiancé, best friend, and most stalwart field assistant. I am sorry about all the spiders and ticks we encountered but I am very glad you still want to marry me. iii TABLE OF CONTENTS LIST OF TABLES ......................................................................................................................... v LIST OF FIGURES ...................................................................................................................... vi CHAPTER 1: Phytoliths Produced by Eastern North American Conifers and Their Potential for Reconstructing Historical Vegetation of the Southeast ..................................... 1 Introduction ........................................................................................................................ 2 Methods.............................................................................................................................. 4 Results ................................................................................................................................ 5 Discussion .......................................................................................................................... 7 References ........................................................................................................................ 10 Tables ............................................................................................................................... 14 Figures.............................................................................................................................. 22 CHAPTER 2: Shade-tolerance Classification of the Upland Herbaceous Flora of the Carolina and Virginia Piedmont .............................................................................................. 35 Introduction ...................................................................................................................... 36 Methods............................................................................................................................ 37 Results .............................................................................................................................. 40 Discussion ........................................................................................................................ 42 References ........................................................................................................................ 44 Tables ............................................................................................................................... 48 Figures.............................................................................................................................. 76 CHAPTER 3: Long-term Monitoring of Vegetation Plots and Echinacea laevigata