TEMPORAL AND SPATIAL PATTERNS IN MID-APPALACHIAN SPRINGS

Abstract

The major topographic features and river courses of the mid-Appalachian Mountains are geologically ancient. Small rheocrenes are numerous in carbonate valleys with macroinvertebrate assemblages typically dominated by peracaridans and sometimes gastropods, with subordinate abundances of bivalves, triclads, and insects. Springs were approximately rank ordered by temporal persistence, using size, catchment area, proximity to base level, and bedrock permeability factors as criteria. A 38-m²rheocrene, Ell Spring, was sampled seasonally over a 2-year period for distribution and abundances of taxa. Physicochemical factors and rank order of ordinal abundances were stable the 1st year, but less so the 2nd year after a watercress cover was removed. Ell Spring is divided into nine distinct habitat patches. Some species distributions are strongly associated with patches and others are broader. Regionally, heterozygosity and allele frequency patterns ofGammarus minus(Amphipoda) are conditioned by latitude, indicative of the effects of Pleistocene glaciation, and by distance to regional master streams. These factors do not detectably influence the ordinal composition of macroinvertebrate assemblages. However overall invertebrate abundances and the ratio of non-insect orders (which are presumably less rapid colonists) to insect orders are greater in long-persisting than in frequently disturbed springs. The species assemblages of disturbed springs may be influenced by recent history as well as by water chemistry, substratum, and other equilibrium factors.