Enabling a process-oriented hydro-biogeochemical model to simulate soil erosion and nutrient losses

Abstract. Water-induced erosion and subsequent particulate carbon (C), nitrogen (N) and phosphorus (P) nutrient losses were the vital parts of biogeochemical cycling. Identifying their intensity and distribution characteristics is of great significance for the control of soil and water loss and N/P nonpoint source pollution. This study incorporated the modules of physical soil erosion and the particulate C, N and P losses into the process-oriented hydro-biogeochemical model (CNMM-DNDC) to enable it to predict soil and water loss. The results indicated that the upgraded CNMM-DNDC i) performed well in simulating the observed temporal dynamics and magnitudes of surface runoff, sediment and particulate N/P losses in the lysimetric plot of the Jieliu catchment in Sichuan Province; ii) successfully predicted the observed monthly dynamics and magnitudes of stream flow, sediment yield and particulate N losses at the catchment outlet, with significant zero-intercept univariate linear regressions and credible Nash–Sutcliffe indices larger than 0.74. The particulate N accounted for 16.2 %−26.6 % of the TN components during the period with larger precipitations. The intensities of soil erosion and particulate nutrient losses in the Jieliu catchment was closely related to land use type in the order of sloping cultivated cropland > residential area > forest land. The scenario analysis demonstrated that high greenhouse gas (GHG) emissions scenarios provided a greater risk of soil erosion than did low GHG emissions scenarios and land use change could help to mitigate soil and water loss accelerated by climate change in the future. The upgraded model was demonstrated to have the capability of predicting ecosystem productivity, hydrologic nitrogen loads, emissions of GHGs and pollutant gases, soil erosion and particulate nutrient losses, which may become a decision support tool for soil erosion and nonpoint source pollution control coordinated with increasing production and reducing GHGs and pollutant gases emissions in a catchment.