Organic sulfur in throughfall, stem flow, and soil solutions from temperate forests

In the assessment of S cycling in forest ecosystems, solutions passing through the forests are normally analyzed for inorganic SO 4 ; other forms of S are rarely considered. In this study, organic S (estimated as the difference between total S and SO 4 -S) was measured in canopy and soil solutions from eight forest stands spanning a broad range of overstory and soil types. Organic-S concentrations varied among the different types of solutions and among the forests, with values ranging from 0 to 50 μmol S*L −1 . Organic S was ≤10% of total S in precipitation, 5 to 54% in throughfall, 1 to 50% in stem flow, 16 to 46% in O-horizon solution, 11 to 21% in A- or E-horizon solutions, and 0 to 29% in B-horizon solutions. Organic S was positively correlated with organic C and organic N in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and red alder (Alnusrubra Bong.) soil solutions and in Douglas-fir stem flow (r 2 = 0.68 to 0.96, p