Carolina bays are precipitation-driven, depression wetlands found on the southeastern U.S. Coastal Plain, chiefly from Georgia through the Carolinas and into Virginia. Elliptical in shape, bays are oriented northwest to southeast and often have a sand rim that is most prominent on the southeast side (Fig. 1). These wetlands are characterized by highly variable hydrologic regimes that can differ widely between individual bays. Thus the vegetative composition of even adjacent bays may differ as a result of disparate hydrographs. Species composition within bays also changes in accord with the dominant hydrology of a given time.

From mid-1998 through 2002, the Upper Coastal Plain of South Carolina experienced prolonged drought, providing an opportunity to study how vegetative composition of bays characterized by herbaceous species changed following a relatively wetter period in the mid-late 1990's (Fig. 2). Numerous bays on the Savannah River Site (SRS) (Fig. 3) had a record of vegetation and hydrology pre-dating the drought, and by re-sampling a selection of these bays during the drought, changes in species composition could be assessed. Bays with similar hydrologic regimes were hypothesized to exhibit comparable changes in composition as a result of drought. Further, the response of vegetation to hydrologic change was thought to be general enough to be portrayed by a concise descriptive model. Such a descriptive model can guide predictions of composition under a variety of conditions. An understanding of how Carolina bay vegetation responds to climatic variability can provide a useful tool for guiding management decisions that may alter their hydrology and may provide a mechanism for assessing the success of bay restorations.