We monitored water chemistry of rain, stemflow, and treeholes in three landscape-scale regions in Pennsylvania receiving high, but different, atmospheric inputs of hydrogen and sulfate ions. Input of water into treeholes is primarily via stemflow, which can be altered dramatically by dry deposition. We found that pH, [SO4], and [NO3] of treehole water differed among the three regions: the westernmost 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 levels of [SO4] in stemflow than rain indicate substantial dry deposition. Correlation of stemflow [SO4] and treehole [SO4] indicates that dry deposition influences 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 indicates contribution of these cations via alternate pathways, such as the breakdown of leaf litter. Treehole water chemistry varies at the landscape and local spatial scales, and biotic variation among treeholes may be larger than variation among regions. Consequently, no obvious effect of regional deposition on treehole fauna was found.
atmospheric deposition, pH, sulfate, treeholes, stemflow
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