Biogeochemistry of a forested watershed in the central Adirondack Mountains: Temporal changes and mass balances

Abstract

Information on atmospheric inputs, water chemistry and hydrology were combined to evaluate elemental mass balances and assess temporal changes in elemental transport from 1983 through 1992 for the Arbutus Lake watershed. This watershed is located within a northern hardwood ecosystem at the Huntington Forest within the central Adirondack Mountains of New York (USA). Changes in water chemistry, including increasing NO₃ ⁻ concentrations (1.1 μmol _c , L⁻¹ yr-1), have been detected during this study period. Starting in 1991 hydrological flow has been measured from Arbutus Lake and these measurements were compared with predicted flow using the BROOK2 hydrological simulation model. The model adequately (r²=0.79) simulated flow from this catchment and was used to estimate drainage for earlier periods when direct hydrological measurements were not available. Modeled drainage water losses coupled with estimates of wet and dry atmospheric deposition were used to calculate solute budgets. Export of SO₄ ²⁻ (831 mol _c ha⁻¹ yr⁻¹) from the greater Arbutus Lake watershed exceeded estimates of atmospheric deposition in an adjacent hardwood stand suggesting an additional source of S. These large drainage losses of SO₄ ²⁻ also contributed to the drainage fluxes of basic cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺). Most of the atmospheric inputs of inorganic N were retained (average of 74% of wet precipitation and 85% total deposition) in the watershed. There were differences among years (56 to 228 mol ha⁻¹ yr⁻¹) in drainage water losses of N with greatest losses occurring during a warm, wet period (1989–1991).