Simulated impacts of soil erosion on regional carbon balance of continental China

Soil erosion has been known to cause land degradation and excessive carbon and nutrient loss, hence to decrease in regional net ecosystem carbon balance. In this study, we adopted a biogeochemistry model, TESim, to simulate the impact of soil erosion on regional net ecosystem carbon balance of continental China from 1961 to 2001. The model incorporates physiological traits of plant functional types and runoff-induced soil erosion and carbon loss into the general production-partition-littering-decomposition processes coupled with water and nitrogen cycles. The model was parameterized with large amount of field NPP and biomass data, and was tested against long-term observations on soil water dynamics and biomass dynamics in 25 sites at watershed and patch scales. The simulation indicates that soil erosion caused severe carbon loss on crop areas with small belowground biomass and low aboveground vegetation cover. However, soil erosion in wild vegetation is mostly small, but can be severe in some open locations without vegetation cover. For both cases in wild vegetation areas, long-term erosion-induced carbon loss is small, because the open sites in general have much lower content of soil organic carbon than the vegetated sites. Erosion on one hand decreased ecosystem carbon balance by removing soil organic carbon from soil, but on the other hand, erosion also decreased the substrates for microbes activities, thus causing decrease in heterotrophic respiration. Consequently, the regional net ecosystem carbon balance of whole continental China is relatively invariant with respect to soil erosion. However, soil erosion transfers large amounts of carbon and nutrients into aquatic ecosystems, hence has significant consequence on water quality and processes in aquatic ecosystems.