Simulated effects of reduced sulfur, nitrogen, and base cation deposition on soils and solutions in southern Appalachian forests

Effects of reduced deposition of N, S, and C-B on nutrient peels. fluxes, s oil, and soil solution chemistry a ere simulated for two Appalachian forest ecosystems using the nutrient cycling model. In the extremely acidic, N- a nd S-saturated red spruce [Picea rubens (Sarg.)] forest (Nolan Divide), red ucing C-B deposition by 50% reduced C-B leaching by similar to 40% during t he 24-yr simulation period. This was due solely to the effects of Cb deposi tion on the soil exchanger rather than effects on soil solution. Reducing S and N by 50% caused immediate reductions in total anion and cation leachin g at Nolan Divide, but the effects on soil solution C-B diminished and C-B leaching was reduced by only 17% over the simulation period. Reducing 5 and N deposition had a greater effect on soil solution aluminum (Al) and molar Ca/Al ratio than reducing base cation deposition at Nolan Divide. In the m oderately acidic, N- and S-accumulating mixed deciduous forest at Coweeta, reduced C-B deposition by 50% caused a,very slight (< 4%) reduction in C-B leaching as a result of slightly reduced base saturation and increased soil sulfate adsorption. The effects on reducing S and N deposition by 50% on C -B leaching (16% over the simulation period) were greater than those of red uced C-B deposition. The system continued to accumulate both S and N even a t reduced deposition at Coweeta, although growth and vegetation uptake were slightly reduced (-5%) because of increased N deficiency, Base saturation remained well shove the Al buffering range at all times at Coweeta and Al H as an unimportant component of soil solutions in all scenarios.