Soil organic carbon stock responded more sensitively to degradation in alpine meadows than in alpine steppes on the Qinghai-Tibetan Plateau

Grassland degradation is commonly thought to cause soil organic carbon (SOC) change, and the response of SOC stock to degradation is highly dependent on grassland type. However, the effects of grassland type on changes in SOC stocks with grassland degradation over broad geographic scales remain unclear. Here, we explored the probably different responses of SOC stocks to grassland degradation for alpine meadows and alpine steppes based on 58 peer-reviewed publications regarding the Qinghai-Tibetan Plateau. The results showed that SOC stock consistently decreased with increasing degradation levels in both alpine meadows and steppes, whereas the magnitudes of reduction of SOC stock in alpine meadows were significantly larger than those in alpine steppes (p < 0.05). The variations in SOC stock were significantly positively correlated with variations in aboveground biomass in the alpine steppes only (p < 0.05) but were significantly positively correlated with variations in belowground biomass in both alpine meadows and alpine steppes (p < 0.01). The relationships between change rates of SOC stock with initial SOC stock and mean annual precipitation were both significantly negative during the lightly and moderately degraded stages, while the negative relationship became nonsignificant for the heavily degraded stage (p > 0.05). These findings suggest that soil organic carbon stock responded more sensitively to degradation in alpine meadows with higher initial SOC stock and annual mean precipitation than in alpine steppes. Our study might have significant implications for future sustainable management practices for carbon sequestration of alpine grasslands on the Qinghai-Tibetan Plateau.