Effects of low-level SO2 fumigation on decomposition of western wheatgrass litter in a mixed-grass prairie

Litter bags were used to determine the effects of SO₂ and substrate-S content on decomposition rates of western wheatgrass tillers in the field. Atmospheric SO₂ decreased monthly decomposition rates 32 to 44% in spring and early summer and 12% in dry late summer. Increased S content of the substrate (980 μg g^?1 vs 590 μg g^?1 in control) had no measurable effect on decomposition. The observed inhibition was probably caused by reduced pH and/or accumulation of toxic derivatives of SO₂ in the microenvironment of organisms on the decaying leaf surfaces.