The effects of atmospheric deposition on potassium, calcium, and magnesium cycling in two deciduous forests

Abstract

Sulfate was the dominant anion in throughfall and soil solutions from a chestnut oak (Quercuspinus L.) and a yellow poplar (Liriodendrontulipifera L.) forest in eastern Tennessee. Assuming much of this [Formula: see text] was of anthropogenic origin, cation-leaching rates from foliage and in soils of these forests would have to have been accelerated by acid deposition by two- to three-fold. This acclerated leaching could, in turn, cause changes in the rates of K+, Ca2+, or Mg2+ cycling according to any of a number of possible scenarios explored in this paper. Subsoils beneath the chestnut oak stand adsorbed [Formula: see text] from atmospheric deposition, which reduced [Formula: see text]-mediated cation leaching to some extent. In contrast, subsoils from the yellow poplar stand showed a current net output of [Formula: see text] (perhaps desorbing sulfate adsorbed during previous periods of higher input) and much higher rates of cation leaching. The yellow poplar site showed net annual exports of Ca2+, Mg2+, K+, and Na+, but the chestnut oak site showed a net accumulation of Ca2+ and lower net annual exports of Mg2+ and K+ than the yellow poplar site. Both sites had inexplicably large net exports of Na+.