Sulfur Transformations in Forest Litter and Soil: Results of Laboratory and Field Incubations
- M. E. Watwood and
- J. W. Fitzgerald
Field incubations of litter (01 and 02 layers) and A horizon soil utilizing 35S-labeled inorganic sulfate were conducted during July 1985 in an eastern white pine (Pinus strobus L.) and a hardwood forest. Samples were assayed for the capacity to form 35S-labeled organic S, and in most cases these capacities were very similar to those determined in corresponding laboratory incubations. The A horizon soils from both watersheds formed approximately 3.0 nmol of organic S g−1 dry weight of sample during 2-d field or laboratory incubations. No substantial increase in this amount was observed after 7-d field incubations. Intrinsic S fractions of samples were quantified prior to and following field incubations, and organic S represented the majority of the total S in all cases. Total S ranged from 260 to 1180 and from 150 to 270 mg kg−1 in the litter layers and the A horizon, respectively. Sulfonate S (13–74% of total S) and nonphosphate extractable ester sulfate (16–82% of total S) were the largest organic S pools. Water soluble and phosphate extractable S pools were comprised of both inorganic sulfate and ester sulfate, and the latter was found to represent up to 8.1% of total S. The distribution of 35S following field incubations was determined, and organic 35S fractions in a variety of linkage groups were again found to predominate. Total C, moisture content, and throughfall sulfate concentrations during the field incubations were also determined.
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