SULFUR SPECIATION AND DISTRIBUTION IN SOILS AND ABOVEGROUND BIOMASS OF A BOREAL CONIFEROUS FOREST

Major sulfur pools are quantified in soils and aboveground biomass of a coniferous boreal forest. Total ecosystem S averages 1395 kg.ha-1 of which 98% is found in the soil, with 89% being in the mineral horizons. Organic S dominates in soil, tree parts (trunks, branches + foliage, roots) and litterfall, ranging from 77 to 99% of total S concentration. Carbon-bonded S, ester sulfate and SO4-S in soil profiles range respectively from 51-68%, 29-37% and 1-14% of total S concentrations and account respectively for 57, 33 and 10% of total S on an areal basis. Adsorbed SO4 accounts for 82% of total SO4, and can be predicted from Al bound to organic matter, amorphous Al and pH (r2 = 0.81). There is a strong relationship between % carbon and carbon-bonded S in 4 of the 5 soil horizons studied which represent over 95% of the total soil organic matter, whereas ester sulfate is related to % carbon in 3 soil horizons representing only 37% of the soil organic matter. An analysis of atmospheric S loading and S data for 10 forested sites in Europe and North America suggests that the size of the organic S pool in forested systems is independent of atmospheric loading.