ORGANIC SULFUR TRANSFORMATIONS AND SULFUR POOL SIZES IN SOIL AND LITTER FROM A SOUTHERN APPALACHIAN HARDWOOD FOREST

Abstract

We assayed litter and soil samples from a mixed mature hardwood forest for the capacity to incorporate sulfate-sulfur into organic matter and for the capacity to subsequently mobilize the organic sulfur formed. The levels of total S, carbon-bonded S, ester sulfate, and free and adsorbed S Were also determined. We found seasonal variation in sulfur pool sizes, transformation rates between inorganic sulfate and organic sulfur, and in transformation rates among the organic sulfur pools. Higher incorporation rates were observed with samples having higher contents of carbon-bonded S. Amounts of this form levels of amino acid S and sulfolipid, thus reflecting the level of readily available carbon and energy. During sampling dates when ester sulfate contents were low, organic S mobilization rates were elevated and free and adsorbed S pools increased. These observation support the possibility that ester sulfate in soil may serve as an important supply of sulfur for biological uptake.