Mobilization of recently formed forest soil organic sulfur

Abstract

Soils from a mixed mature hardwood forest were assayed for their capacity to mobilize sulfur which had been previously immobilized into a nonsalt-extractable (insoluble) form. These soils rapidly released soluble organic sulfur and inorganic sulfate from this fraction. It is suggested that the former component is a depolymerization product of a more complex organic sulfur matrix. The activity of preformed extracellular depolymerase and sulfohydrolase enzymes in the soil may be responsible for the depolymerization and subsequent desulfation of the organic sulfur matrix. This is supported by observations that treatment of soil samples with sodium sulfate, sodium azide, erythromycin, or candicidin failed to inhibit the capacity of A1-horizon soils to mobilize the organic sulfur fraction. The rates and final levels of sulfur mobilization increased with an increase in temperature and decreased with sample depth.