Title: Precipitation Change and Soil Leaching: Field Results and Simulations from Walker Branch Watershed, Tennessee
Author: Johnson, D.W.; Hanson, P.J.; Todd, D.E., Jr.; Susfalk, R.B.; Trettin, Carl C.
Source: Water, Air, and Soil Pollution 105: 251-262, 1998
Description: 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.
Keywords: Nutrient Cycling Model, rainfall, soil solution chemistry, Walker Branch Watershed
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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.