4.3 Implications for management practices
Ecosystem organic carbon and nitrogen stocks in grasslands are determined by soil, plants, and their interactions. Although there was a decrease in ecosystem nitrogen stock, GE significantly increased the ecosystem organic carbon stock and improved its distribution in the aboveground soil and roots and enhanced plant productivity, as compared to those observed after implementing the grazing methods in this region (Table 2). This suggests that long-term GE is an effective way to improve ecological health and resilience in karst grasslands, regardless of livestock grazing. Although the ecosystem organic carbon and nitrogen stocks were not significantly different among grazing methods, we found that the EOCs and ETNs of MG and RG increased by 16.31% and 7.76%, respectively, while MG increased the EOCs by 22.29% and slightly decreased the ETNs compared with CG (Table 2), indicating that grazing could partly improve the ecosystem C and N stocks. Similar results were found in other studies (Chen et al., 2021; Wen Li et al., 2017). RG can substantially increase livestock stocking levels while improving vegetation, soil carbon, and water infiltration functions (Mosier et al., 2021). According to the moderate disturbance hypothesis, reasonable grazing or mowing causes an increase in grassland productivity and improve soil physicochemical properties, thus maintaining a continuous supply capacity of nutrients and enabling the ecosystem to stay in a healthy and stable condition (T. D. Mipam, Zhong, Liu, Miehe, & Tian, 2019; G. Zhou et al., 2017). Previous studies also found that RG increased SOC and TN stocks (0-1 m) by 13% and 9%, respectively, compared with continuous grazing (Mosier et al., 2021). Mowing significantly increased the SOC and TN stocks in the topsoil layer (0–30 cm) (Chen et al., 2021). Overall, GE is a viable approach to significantly improve vegetation resilience and soil carbon storage, whereas RG should be considered under the condition of pasturing utilisation in karst grasslands (regardless of GE).