Analysis of carbon and nitrogen dynamics in riparian soils: Model validation and sensitivity to environmental controls

The Riparian Soil Model (RSM) of Brovelli et al. (Sci. Total Environ., this issue) was applied to study nutrient turnover in a revitalized section of the Thur River, North-East Switzerland. The model was first calibrated on field experimental data. The model satisfactorily reproduced soil respiration, organic matter stocks and inorganic nitrogen fluxes. Calibrated rates were in good agreement with the ranges reported in the literature. The main discrepancies between model and observations were for dissolved organic carbon. Following model testing, its sensitivity to environmental factors was analysed. Soil temperature was the most influential factor at daily and seasonal scales while soil moisture effects were overall weak. The ecosystem sensitivity to temperature changes was quantified using the Q10 index. Seasonal behaviour was observed, which was related to the influence of other forcing factors and to the different state (density and activity) of the microbial biomass pool during the year. Other environmental factors influencing microbial decomposition, such as the C:N ratio and litter input rate, showed intermediate sensitivity. Since these parameters are tightly linked to the vegetation type, the analysis highlighted the effect of the aboveground ecosystem on soil functioning.