Integrated response of carbon sequestration along co-varying gradients of climate and grazing intensity in a desert steppe ecosystem

The interactive effects of grazing and climate on carbon (C) storage are important for the global C budget and regional C management. In a regional-scale field experiment based on multiple grazing gradients, we examined how changes in grazing intensity and climate affected the C sequestration rate and C storage at five desert steppe sites. The mean total ecosystem C storage at each site ranged from 1502 to 3728 g C m(-2) and averaged 2341 g C m(-2). The peak value of the C sequestration rate (290 g C m(-2) yr(-1)) occurred in the light grazing intensity. The light grazing and fencing management were more beneficial to C sequestration. The rising temperature would decrease C storage in desert steppe, while rising precipitation would promote C sequestration. Soil nitrogen content plays an important role in the driving mechanism of C sequestration in desert steppe. The soil C pool, which dominated the C dynamics in desert steppe, was influenced by the changes of precipitation and grazing intensity. Grazing affects soil nitrogen content by changing the aboveground C pool. Precipitation changes may change soil C storage by influencing the aboveground C pool to change soil nitrogen content and microbial biomass. Such information improves understanding of the dynamics of C storage and sequestration in desert steppe, and is critical for improving the sustainability of grassland ecosystem services and C management.