Soil carbon mineralization decreased in desert steppe by light grazing but not fencing management

Abstract

Fencing off grassland soils emits massive amounts of carbon into the atmosphere. Whether grazing management in desert steppes with fragile ecosystems can mitigate this trend remains highly uncertain. Here, we examined how soil carbon mineralization, as well as its underlying mechanisms, varied with grazing intensity by sheep in a long-term (17 − year) experiment in the desert steppe. Carbon mineralization decreased by 15 % − 55 % under different grazing intensities compared to fencing controls. Soil organic carbon (SOC) maintained high levels under light grazing, whereas it decreased with increasing grazing intensity. Reductions in plant carbon and absolute microbial abundance due to grazing, coupled with changes in soil carbon quality and the environment, drove the reduction in carbon mineralization. We suggest that mechanisms of carbon mineralization can be integrated into predictive modelling efforts to better understand the impact of grazing on carbon fluxes in ecologically fragile, but globally important, arid and semi-arid grasslands.