Effect of Whole‐Tree Harvesting on the Sulfur Dynamics of a Forest Soil

Abstract

Abstract Sulfur constituents in the soil at the Hubbard Brook Experimental Forest are dominated by C‐bonded S and ester‐sulfate with smaller concentrations of adsorbed sulfate and ZnHCl‐reducible S forms. The relative proportions of these constituents are similar to those found in other Spodosols. Two years after a whole‐tree harvest of Watershed 5 there was a significant increase in adsorbed sulfate in the E and Bh horizons from 0.70 to 3.16 and from 2.73 to 4.96 kg ha −1 , respectively, while organic S pools remained relatively constant except for some change in ester‐sulfate pools. This increase in sulfate in these horizons is consistent with patterns of soil solution and stream chemistry, which indicate increased sulfate adsorption due to acidification following mineralization of N, nitrification, and nitric acid leaching. Mass balance calculations comparing SO 4 flux in stream water from watershed 5 with Watershed 6 (reference) accounted for 88% of the sulfate adsorbed in the E and Bh horizons of the former watershed. Organic S ranged 0.7 to 9.5 µmol S L −1 in stream and soil solutions. When this organic S is transported through the soil and deposited in the B horizon, it may serve as a large, stable pool of soil S, less subject to change than that of adsorbed sulfate.