Effects of Liming on Soils and Streamwaters in a Deciduous Forest: Comparison of Field Results and Simulations

Abstract

AbstractSoil and stream chemical responses to liming in a deciduous forest watershed at Coweeta, NC, are compared with simulation results using the Nutrient Cycling Model (NuCM). Field comparisons of limed and unlimed soils after 23 yr indicated substantial net retention of applied Ca2+ and Mg2+ in upper soil horizons, even in black locust (Robinia pseudoacacia L.) sites where NO−3 leaching was elevated. We hypothesized that NuCM simulations would also show that (i) retention of most applied Ca2+ and Mg2+ in the upper horizons and (ii) increased Ca2+ and Mg2+ retention with increased cation exchange capacity (CEC) and exchangeable H+ (simulating pH‐dependent CEC). Both hypotheses were supported by simulation results for Ca2+, but not for Mg2+. Most applied Mg2+ in the simulations was retained in the BC horizon, where the largest pool of exchangeable Mg2+ was initially located. Increasing CEC and exchangeable H+ did result in increased retention of applied Ca2+ and Mg2+ in surface horizons. However, increasing CEC caused lower Mg2+ retention in the BC horizon, which offset the surface horizon increases and resulted in lower total retention of applied Mg2+. Simulated BC horizon soil solution concentrations mimicked the general patterns in streamwater NO−3, Mg2+, Na+, Cl−, SO2−4, and K+ between 1971 (12 yr after liming) and 1979. NuCM simulations did not, nor was it possible to simulate the observed effects of an insect outbreak on streamwater NO−3.