Changes in soil sulfur constituents in a forested watershed 8 years after whole-tree harvesting

Soil S constituents were evaluated before and after the whole-tree harvesting of Watershed 5 (W5) at the Hubbard Brook Experimental Forest, New Hampshire. Soil solution and stream water concentrations of SO₄/^2-, NO₃/^-, and H⁺ were compared between W5 and W6 (reference watershed). Whole-tree harvesting increased phosphate-extractable SO₄/^2- (PSO₄) in the E horizon, from 2 mg S · kg^-1 soil in pre-harvest to 9 and 10 mg S · kg-1 soil 3 and 8 years post-harvest, respectively. Harvesting increased PSO₄ in the Bh horizon from 11 mg S · kg^-1 soil prior to harvesting to 20 and 25 mg S · kg^-1 soil 3 and 8 years after harvesting, respectively. Temporal patterns in soil chemistry were also reflected in stream SO₄/^2-, NO₃/^-, and H⁺ concentrations. Eight years after harvesting, PSO₄ concentrations in the mineral soil increased with elevation. This elevational pattern was likely due to the higher concentrations of SO₄/^2- and H⁺ in soil solutions that enhanced SO₄/^2- adsorption at the higher elevations. The high H⁺ concentrations were attributed to enhanced nitrification and differences in vegetation at upper elevations. The importance of these factors were discussed with respect to the effects of forest harvesting and changes in atmospheric S deposition.