Difference of soil carbon density under different grazing exclusion duration in Seriphidium transiliense desert with distinct degrees of degradation

Overgrazing and continuous grazing give rise to considerable decreases in aboveground biomass and soil organic carbon. Grazing exclusion (GE) has been determined to be an effective approach to enhance the soil carbon storage of arid and semiarid grasslands in China. However, at present, there is no consensus regarding whether GE affects soil carbon, especially in desert regions with differing degrees of degradation. This paper examines the changes in soil organic carbon density (SOCD), easily oxidizable carbon density (EOCD) and microbial biomass carbon density (MBCD) in slightly degraded desert (SD) and moderately degraded desert (MD) after different periods of GE. The results indicate that GE did not significantly alter SOCD in SD, but GE caused SOCD to decrease by 12.7–25.6% in 0–20-cm soil depth in MD. EOCD and MBCD in all soil surface layers of SD first decreased and subsequently increased with increasing GE duration, whereas in the 0–20-cm soil layer of MD, these values increased linearly with increasing GE duration and aboveground biomass. Therefore, we proposed that carbon density was significantly different among distinctly degraded deserts, and we should consider the degree of degradation and the condition of desert regions before implementing GE.