Sulfur Distribution and Cycling in a Deciduous Forest Watershed

Abstract

AbstractSulfate sulfur concentrations and pH of precipitation and streamflow, and sulfur concentrations of biomass and soil components, were determined for a 97.5‐ha mixed deciduous forest (Walker Branch Watershed) in eastern Tennessee. Amounts of sulfur (S) added precipitation and lost by streamflow were compared to fluxes of S between biomass pools. Approximately 18.1 kg/ha per year entered the watershed from the atmosphere, while only 11.5 kg/ha per year were lost in streamflow. Analysis of biomass and soil concentrations of S indicate that, of the 6.6 kg/ha per year apparent accumulation of S for the watershed as a whole, 8.6 kg accrue to mineral soil while 4.3 kg are lost from organic soil horizons, and 2.3 kg accrue to annual increment of vegetation.Seasonal variations in S input and export from the watershed were closely tied to precipitation events. The weighted mean pH of the rainfall samples collected at five sampling sites on the watershed was pH 4.2. Sulfate accounts for 80% of major anions (millequivalent basis) contributed to the watershed. The behavior of S on Walker Branch Watershed appears to differ significantly from locations in the northeastern U.S., however the data suggest active expansion to the southeastern U.S. of the area impacted by atmospheric sulfate pollution commonly associated with the northeastern region of the U.S.