Importance of organic and inorganic sulfur to mineralization processes in a forest soil

Sulfur mineralization rates, changes in organic and inorganic S constituents and arylsulfatase activity were determined in four soil horizons (O2, B21h, B22hir and B23) which represent the major portion of a forest Spodosol (Becket). Biweekly, for 20 weeks, soil subsamples were leached with deionized water and analyzed for S constituents. Rates of water-soluble sulfate release were 123, 39, 34 and 18 nmol S g^?1 dry mass week^?1 for O2, B22hir, B23 and B21h horizons, respectively. Only in the organic O2 horizon did non-sulfate inorganic S (Zn-HCl-S) increase (15 nmol S g^?1) while phosphate extractable S decreased in all the mineral horizons (13, 19 and 28 nmol S g^?1 week^?1, B21h, B22hir and B23, respectively) due to desorption. Ester sulfate was mineralized in the B22hir and B23 horizons (?66 and ?22 nmol S g^?1 week^?1) and increased in the O2 (174 nmol S g^?1 week^?1). Arylsulfatase activity varied among horizons and decreased with time. Carbon-bonded S decreased in all horizons, especially those with high respiration rates (i.e. O2 and B21h), but changes were not significant. Only the B22hir horizon exhibited a significant loss of total S (128 nmol S g^?1 week^?1). The interrelationships among inorganic and organic S dynamics were outlined.