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.