Modeling Soil Moisture Effects on Net Nitrogen Mineralization in Loamy Wetland Soils
2008
Sleutel, Steven | Moeskops, Bram | Huybrechts, Willy | Vandenbossche, Annemie | Salomez, Joost | De Bolle, Sara | Buchan, David | De Neve, S. (Stefaan)
Nutrient dynamics in wetland ecosystems are largely controlled by soil moisture content. Therefore, the influence of soil moisture content on N mineralization should be explicitly taken into account in hydro-ecological models. The aim of this research was to establish relationships between N mineralization and soil moisture content in loamy to silty textured soils of floodplain wetlands in central Belgium. Large undisturbed soil cores were taken, incubated for 3 months under various moisture contents, and zero order and first order N mineralization rates were calculated. We used the percentage water-filled pore space (WFPS) as an expression of soil moisture because it is a better index for aeration dependent biological processes than volumetric moisture content or water retention. The relationship between the N mineralization rate and %%WFPS was described by a Gaussian model. The optimum WFPS for N mineralization ranged between 57%% and 78%%, with a mean of 65%% ±± 6%% WFPS. Expected annual net N mineralization rates at field temperature (9.7°°C) and at optimal moisture content varied between 30 and 186 kg N ha⁻⁻¹ (0––15 cm depth) year⁻⁻¹, with a mean of 110 ±± 42 kg N ha⁻⁻¹ (0––15 cm) year⁻⁻¹. The mean N turnover rate amounted to 2.3 ±± 1.1 g N 100 g⁻⁻¹ N year⁻⁻¹. Multiple linear regressions between N mineralization and general soil parameters showed that soil structure has an overriding impact on N mineralization in wetland ecosystems.
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