SOIL SOLUTION CHEMISTRY ON THE THREE SLOPES OF A NATURAL HARDWOOD STAND IN THE SUBTROPICS OF THE FUSHAN FOREST

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Abstract

The soil solutions in three different horizons on the upper slope, middle slope, and lower slope of a natural hardwood from 2001 to 2004 were investigated. Soil solution pH from all the slopes showed a trend of becoming more acidic throughout the duration of the study. In contrast with pH, the Al and Mn concentrations showed a significant elevation from the upper and middle slopes in the soil solution for the duration of the study. Hence, the response to acid anion or proton input was through Ca and/or Al mobilization. The NO3− concentrations declined during the 3-year study period for all slopes and depths, with a larger decrease in concentration trend for the lower slope. The concentrations of SO42− and HCO3− increased during the monitoring period, especially for the lower slope. Except Na in the 30-cm and 60-cm depth, the trends for K, Na, Ca, and Mg were always negative, suggesting that the soils were becoming more acidic. When precipitation passed through the canopy, total ion concentration increased, except for H+. Concentrations of Na, K, Ca, Mg, F, Cl, PO43−, SO42−, and HCO3− in the throughfall generally exceeded the soil solution at the upper and middle slopes, whereas at the lower slope, Na, Ca, Mg, F, and Cl concentrations were the highest at the 15-cm soil depth.

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