LOCAL AND LANDSCAPE INFLUENCES ON THE PLANT COMMUNITIES OF CAROLINA BAYS

Carolina bays represent a subset of depressional geomorphic features that are widespread across several geological surfaces on the Atlantic Coastal Plain. As a hydrogeomorphic class, these depressions support wetlands with predominantly vertical hydrodynamics. The wetlands have ecological value in supporting a diverse range of plant communities and providing critical breeding habitats for a distinctive semi-aquatic fauna. Our work has sought to understand the environmental drivers of depression vegetation diversity. In addition to traditional analyses relating plant communities to local-scale wetland properties (e.g., hydroperiod, basin size), we also explored the potential for a hydrogeomorphic framework to predict local properties and thus shape regional-scale patterns of vegetation diversity. We sampled Carolina bays and similar depressions across the Inner and Outer Coastal Plains of South Carolina, and analyzed plant community distribution in relation to wetland-specific properties and to landscape settings defined by surficial geology and soils. At the local scale, vegetation type is most strongly correlated with the hydrologic regime, but other properties such as basin size, soil textural class, and land use are also important. Because hydrogeomorphic landscape setting is a partial predictor of some wetland properties, vegetation types are distributed non-randomly across the regional landscape. However, landscape setting does not uniquely predict individual depression vegetation; rather, the dominant plant communities reflect complex interactions between local features and landscape-influenced processes. These concepts are incorporated into a landscape-contingent conceptual model for vegetation dynamics. Additional work on the hydrogeologic mechanisms for depression hydrology could improve our predictive understanding of Carolina bay vegetation diversity.