Relationship of atmospheric deposition to the water chemistry and biota of treehole habitats

We monitored water chemistry of rain, stemflow, and treehole invertebrate communities in three landscape-scale regions in Pennsylvania receiving high, but different, atmospheric inputs of hydrogen and sulfate ions. We predicted that treeholes in the westernmost plateau region receiving the highest levels of those ions would have different water chemistry than those in other regions. We found that the plateau region had significantly lower pH and higher [SO4] than the central valley and easternmost ridge regions. This was correlated with higher [SO4] in plateau rain. Higher [SO4] in stemflow than rain indicated substantial dry deposition, and correlation of stemflow [SO4] and treehole [SO4] indicated that dry deposition influenced water chemistry of treeholes. Treehole [NO3] differed with time and region and was highest in August. Other chemical parameters in rain and stemflow were correlated with treehole water chemistry. Treehole [Mg] followed the pattern in stemflow, which was also correlated with rain [Mg]. However, higher [Mg], [Ca], and [K] in treehole water than in aqueous inputs indicated contribution of these cations via alternate pathways, such as the breakdown of leaf litter. No regional effects of deposition on treehole fauna were found, however, treehole insect densities and species richness were related to water volume, [SO4], [Na], and dissolved organic carbon (DOC).