PS 6-59 - Floristics of Virginia’s forgotten Piedmont grasslands

Background/Question/Methods

Temperate and subtropical grasslands are among the most globally threatened biomes. Increased recognition of grassland biodiversity and functional value is needed to promote their conservation and restoration. The southeastern grasslands of the United States exemplify this plight. For example, grasslands of the Southeastern Piedmont have lostover 90% of their historic range, and those that remain face continued habitat loss, the disruption of natural disturbance regimes, and invasive species pressure. To conserve the remaining Piedmont grasslands, we need to recognize their natural extent, characterize distinct grassland floristic community subtypes, and identify the disturbance regimes and edaphic factors that drive their persistence. To discern if Piedmont grassland communities have distinct subtypes driven by variation in edaphic characteristics, we surveyed plant communities and collected soil samples using modified Whittaker plots in 135 remnant and semi-natural grassland fragments across the northern and central Virginia Piedmont.

Results/Conclusions

We identified 684 taxa across 135 survey sites, including the globally imperiled Torrey’s Mountain-Mint (Pycnanthemum torreyi). Remnant grassland communities varied on similar environmental axes as regional forests, with diverging species assemblages in upland versus wetland locations and acidic versus mafic substrates. PERMANOVA of the plant community data shows evidence that Piedmont grasslands can be divided based on their generalized lithology (P < 1 x 10^-5, R² = 0.14292) and soil order (P < 1 x 10^-5, R² = 0.05271). We can refine these broad categories into community subtypes based on substrate and soil characteristics, such as acidic wet grasslands and mesic upland grasslands. These refined subtypes can guide targeted community description and conservation efforts. By describing environmentally driven variation in Piedmont grasslands, we can raise awareness about these undervalued but historically common ecosystems, identify unique natural communities worthy of conservation, and inform nuanced reference models for grassland and savanna restoration.