DEGREE AND SCALE OF TERRESTRIAL ACIDIFICATION AND AMPHIBIAN COMMUNITY STRUCTURE

Censuses of forest floor amphibian assemblages at 17 sites in New York revealed that amphibian density and species richness were lower in more acidic habitats. At least three species of salamanders have field distributions that suggest an avoidance of acidic conditions. A gradient of humus and mineral soil pH exists with relatively high [H+]s in the forest interior and lower [H+]s near streams and seepage areas. Small scale maps of humus and mineral soil [H+] reveal much spatial heterogeneity in a beech forest and little in,coniferous forests. The dominant modes of soil pH for New York and for sites around the globe are in the aluminum and iron buffering ranges, where these elements dominate soil chemistry. We hypothesize that high concentrations of aluminum and/or iron, in soil solutions at low pHs, reduce sodium available for uptake by amphibians, and together with increased sodium efflux on low pH substrates result in a toxic disruption of sodium balance. Future experiments must determine if artificially reduced humus and/or mineral soil pH reduce amphibian density and species richness.