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Historical accounts describe savanna-like conditions over portions of the Piedmont of the southeastern United States dating at least as far back as the 1500s. These open habitats are thought to have declined because of human development, Fire suppression, and loss of native grazing animals. Unfortunately, conservation efforts to restore and sustain Piedmont savanna are hampered by our current rudimentary understanding of community assembly and maintenance dynamics. Such understanding would be facilitated by a robust classification of species into specialist and generalist guilds related to canopy openness, a classification that is currently unavailable on a broad scale. Consequently, our objective was to develop a shade-tolerance classification for the upland Piedmont herbaceous flora of the Carolinas and Virginia, based on quantitative plot data from the region. To achieve this objective, we utilized a dataset of plot records (representing natural and semi-natural vegetation) from the Carolina Vegetation Survey. These are permanent plots on public and private land that were surveyed between 1977 and 2015. Following quality control, the dataset contained 1300 plots and 1550 species (including 835 native herbaceous species after single occurrences were removed), with species abundances in plots reported in cover classes. We estimated the canopy cover of each plot from the cover codes of its tree species and assigned each plot to habitat shade classes: open (75% canopy cover; n = 1097). We calculated point biserial correlation coefficients ([r.sub.pb]), which provided a positive or negative value for each species, dependent on its abundance and habitat association. We considered single (open, semi-open, or closed) and combined (open+semi-open, closed+semi-open, or open+closed) habitat classes during our analysis. Of the 835 native herbaceous species in the dataset, we found 141 (17%) to be heliophytes (specialists of open habitats with canopy cover 75%), despite 84% of plots in the dataset being classified as closed habitats. Our work suggests that open and semi-open habitats may contain a disproportionate diversity of regional herbaceous flora and provides the first quantitative shade-tolerance classification for over 800 herbaceous species. This work provides a resource that can be used by field biologists and land managers to identify heliophyte communities, and to assess the success of habitat restoration and creation efforts., INTRODUCTION Eastern United States Piedmont upland prairies, savannas, and woodlands with a heliophytic flora of Midwest prairie affinity trace an arc beginning with the Blackland prairies of Mississippi and Alabama [...]

Although vegetation succession in the Piedmont of eastern North America favors closed-canopy forest in the absence of disturbance, historical evidence suggests upland vegetation of the region was, in near history, characterized by areas of heliophilic vegetation, such as prairies, savannas, and woodlands. While some work has been undertaken to characterize putative remnant communities at the local and subregional level, there has been no comprehensive, quantitative study to characterize the breadth of heliophilic vegetation commonly referred to as "Piedmont prairies" in the mid-Atlantic portion of the Piedmont, despite evidence that more than one community type is likely represented. We fill this gap by assessing Piedmont prairie communities in the present-day landscape using the best quantitative vegetation data currently available from the Carolina Vegetation Survey vegetation-environment database. We extracted records for 195 permanent vegetation plots representative of upland, terrestrial, open or semi-open vegetation in the Piedmont of the Carolinas and Virginia, a region coinciding with 17th- and 18th-century accounts of historical savannas. Through hierarchical clustering (flexible-β) and stride analysis (plotting the PARTANA ratio and silhouette width), we determined the optimal partition for our dataset to be 12 clusters. The R package optpart was used to move plots between clusters to further ensure plots are members of their best-fit cluster. Nonmetric multidimensional scaling ordination was used to visualize compositional trends in the dataset. We identified 12 major types of heliophilic vegetation that can be categorized 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. [ABSTRACT FROM AUTHOR]

Narrative accounts and floristics suggest a broader historical distribution of Piedmont upland savannas and woodlands with a prairie-affinity flora than today, although dates of emergence, spatiotemporal extent, and historical dynamics remain unclear. To help address the question whether remnant prairie-affinity patches in the state represent at least historical, if not ancient, grasslands, we analyzed stable carbon isotopes from soil organic matter from two well-known localities hosting prairie-affinity heliophytes, both within the boundaries of historically mapped "Grande Savane". Soil cores for d13Corg analysis and radiocarbon dating were collected from five sites, hosting different present-day plant communities and spanning three soil orders. Recovered d13Corg values suggest historical grasslands, likely savanna-type with some fluctuations in cover, were present at both localities essentially continuously over the past 2000 years until the more recent canopy closure over the past century. These findings are consistent with historical narrative accounts, although significant additional sampling is needed to determine its spatiotemporal extent. While the general trend at our localities transitions from open to closed systems, pronounced fluctuations are apparent in all profiles, particularly between 1254-1468 CE. Precipitation does not appear predominantly responsible, but available climatic reconstructions are from an adjacent basin. The timing of the pronounced vegetation class fluctuations is intriguingly coincidental to the timing of Siouan occupancy and intertribal movements, suggesting a need for more vigorous interdisciplinary investigations. [ABSTRACT FROM AUTHOR]