The xeric limestone prairies of Pennsylvania

There is increasing interest in the restoration of classic landscapes such as native grasslands in the northeastern United States. This study characterizes the species composition and range of natural variability of xeric limestone prairies in unglaciated central Appalachia. Bouteloua curtipendula, the characteristic and dominant graminoid, is the primary indicator species for xeric limestone prairies in Pennsylvania, and its distribution is restricted to dry, south-southwest facing slopes within the valleys of the Ridge and Valley Physiographic Province. Only ten such prairies are known to remain in Pennsylvania and their total area is <1 hectare. A total of 126 native taxa representing 40 families was found on the extant prairies. Twelve rare, state-listed prairie species were found on these sites, and their state-wide distributions also were concentrated in the Ridge and Valley. In comparison to Ohio and West Virginia limestone prairies, community structure, determined by dominant graminoids, was identical, but species composition, particularly related to prairie forb assemblages, was slightly different (average Sorenson similarity coefficient = 38%). The limestone prairies of Pennsylvania have a strong association with the Opequon soil series, which is found only in limestone valleys. Xeric limestone prairies in Pennsylvania likely were never a large component of the presettlement landscape, were likely concentrated in central Pennsylvania, and currently serve as important refugia for uncommon eastern prairie species.