Effect of Grazing on the Properties of Soils in the Northeastern Qinghai-Tibet Plateau

Grazing is one of the most important biological disturbance factors in grassland ecosystems, affecting the ecological processes of vegetation and soil. However, we do not know how various grazing types (grazing intensity, grazing duration, and grazing season) affect the functions of alpine grassland ecosystems, which hinders our understanding of grassland biodiversity maintenance and sustainable use of grasslands. This study investigated different grazing types in Maqu County, Qinghai-Tibet Plateau, China, obtained soil and vegetation data, and used meta-analysis to analyze grazing-related variables. The results showed that: (1) Increased grazing intensity significantly reduced soil organic carbon (SOC), soil total nitrogen (STN), and soil total phosphorus (STP), and different grazing times and seasons had significant negative effects on SOC, STN, and STP. (2) Grazing intensity reduced soil carbon-nitrogen ratio (C : N) and carbon-phosphorus ratio (C : P) by 29.3 and 36.1%, respectively, and increased nitrogen-phosphorus ratio (N : P) by 11%. Both grazing intensity and duration had negative effects on C : N and C : P, and positive effects on N : P. (3) Grazing also changed the soil environment. Soil bulk density (SBD), pH, and soil temperature (ST) increased significantly by 12.3, 11.2, and 19.8%, respectively, and soil water content (SWC) decreased significantly by 24.2%. (4) With the increase in grazing intensity, aboveground biomass (AGB), aboveground net primary productivity (ANPP), belowground biomass (BGB), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and soil ciliate biomass (SCB) all showed a decreasing trend, but the number of species and diversity index showed a trend of first increasing and then decreasing.