Response of carbon acquisition enzyme activity and organic carbon mineralization to soil erosion and deposition

Soil carbon (C) acquisition enzymes are useful for studying the biological mechanisms that drive the soil C cycle. As such, understanding the mechanisms that underpin the effect of soil C acquisition enzymes to soil erosion and deposition can help further elucidate the role of soil erosion in the global C cycle. Here, we investigated the relationships between soil CO2 efflux, C acquisition enzyme activity, and soil physicochemical indicators in areas affected by erosion or deposition in a typical watershed in the Loess Plateau, China. We found that C acquisition enzyme activity was significantly higher in the erosion zone than in the deposition zone. Soil organic carbon (SOC) sequestration was higher in the deposition zone, a feature that may dramatically reduce CO2 emissions. Silt and clay pellets directly affected C acquisition enzyme activity by altering SOC, TN (total nitrogen), POC (particulate organic carbon), and EOC (easily oxidizable organic carbon) content, while SOC, TN, POC, and EOC indirectly affected C acquisition enzyme activity by modulating MBC (microbial biomass carbon), which ultimately affects CO2 efflux. In addition, we found differences in the effects of the same pathways on C acquisition enzymes between erosion and deposition zones. Soil C acquisition enzymes are limited by SOC in erosion zones but are limited by TN in deposition zones. Future C cycle studies should consider the spatial variability of C acquisition enzyme activity to reduce uncertainty related to the effects of erosion and deposition on terrestrial C budgets.