Dry deposition of sulfur: a 23‐year record for the Hubbard Brook Forest ecosystem

Dry deposition of S was estimated for watershed‐ecosystems of the Hubbard Brook Experimental Forest from 1964–65 through 1986–87. Two approaches, a regression analysis of bulk precipitation inputs and stream outputs and a mass‐balance method, gave similar average values for Watershed 6 (430 and 410 eq SO₄⁼/ha‐yr, respectively, for this 23‐year period). Dry deposition contributed about 37% of total S deposition, varying from 12% in 1964–65 to 61% in 1983–84. Long‐term data from “replicated” watershed‐ecosystems showed that temporal variability in estimates of dry deposition was considerably greater than spatial (between watersheds) variability.