Precipitation Change and Soil Leaching: Field Results and Simulations from Walker Branch Watershed, Tennessee

Abstract

Abstract. To investigate the potential effects of changing precipitation on a deciduous forest ecosystem, an experiment was established on Walker Branch Watershed, Tennessee that modified the amount of throughfall at 4 -33 %. ambient (no change), and +33 % using a system of rain gutters and sprinklers. We hypothesized that the drier treatments would cause: 1) disproportionate changes in soil water flux, 2) increased total ionic concentrations in soil solution that would in turn cause 3) decreased SO₄, Cl^- ratios, 4) decreased HCO₃-, concentrations, and 5) increased ratios of Al to (Ca²⁺ + Mg²⁺) and of (Ca²⁺ + Mg²⁺) to K’. Hypothesis I was supported by simulation results. Hypotheses 2 and 3 were supported in part by field results, although interpretation ofthese was complicated by pre-treatment biases. Hypotheses 4 and 5 were not supported by the field results. Comparisons of field data and Nutrient Cycling Model (NuCM) simulations were favorable for most ions except Cl^- and K’. The disparities may be due to underestimation ofsoil buffering in the case of Cl^-and overestimation ofsoil buffering in the case of K’ in the model. Long-term simulations with NuCM suggest that reducing water inputs will slow the rate of soil acidification and P loss, but will not materially affect growth or ecosystem N status.

Citation

Johnson, D.W.; Hanson, P.J.; Todd, D.E., Jr.; Susfalk, R.B.; Trettin, Carl C. 1998. Precipitation Change and Soil Leaching: Field Results and Simulations from Walker Branch Watershed, Tennessee. Water, Air, and Soil Pollution 105: 251-262, 1998