Grazing exclusion-An effective approach for naturally restoring degraded grasslands in Northern China

Nearly 90% of the 390 million ha of grasslands in northern China are degraded. 'Grazing exclusion' has been implemented as a nature-based solution to rejuvenate degraded grasslands, but the effectiveness of the rejuvenation processes is uncertain. Here, we investigated the effects of grazing exclusion on aboveground plant community traits, soil physiochemical and biological properties, and the mechanisms responsible for enhanced grassland rejuvenation. A meta-analysis across various studies was used to assess the effectiveness. On average, grazing exclusion improved vegetation coverage by 18.5 percentage points and increased aboveground biomass by 1.13 t ha-1 and root biomass by 1.27 t ha-1, which represent an increase of 84%, 246%, and 31%, respectively, compared with continuous grazing practices. Grazing exclusion reduced soil bulk density by 13.7% and increased soil water content by 68.9%. Grasslands under grazing exclusion increased soil organic carbon (SOC) in the 0-to 15-cm depth by 3.95 (+/- 0.35 Std err) t ha-1 and total soil N, available N, and total soil P in the 0-to 40-cm depth by 2.39 (+/- 0.14), 0.83 (+/- 0.37), and 1.96 (+/- 0.44) t ha-1, respectively, compared with continuous grazing; these values represent an increase of 31%, 25%, 23%, and 14%, respectively. Prolonging the duration (years) of grazing practices enlarged the differences in SOC and soil N content between grazing exclusion and continuous grazing. Grazing exclusion has improved plant community traits and enhanced soil physiochemical and biological properties of degraded grasslands, and thus, this 'nature-based' approach can serve as an effective means to rejuvenate degraded grasslands.