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

Biological Sciences Center, Desert Res. Inst., P.O. Box 60220, Reno, NV and Environmental and Resource Sciences, Univ. of Nevada, Reno, NV 89512;

Wayne T. Swank and James M. Vose

Coweeta Hydrologic Lab., U.S. Forest Service, 999 Soweeta Lab Road, Otto, NC 28763.

^* Corresponding author (dwj{at}maxey.dri.edu)

ABSTRACT

Soil 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^–, SO^2–₄, 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.