To reveal the spatial distribution characteristics and driving mechanisms of soil microbial biomass carbon （MBC）， nitrogen （MBN）， and phosphorus （MBP） stoichiometry under precipitation gradients， this study collected 57 sampling points of three grassland types along a 3000 km transect in Inner Mongolia. The spatial distribution characteristics of microbial biomass and its stoichiometry were analyzed， and their relationship with climate and soil physicochemical factors was explored. The results showed that MBC content was significantly higher than that of MBN and MBP. Microbial biomass was positively correlated with available carbon， nitrogen， and phosphorus in the soil. MBN was negatively correlated with aridity， mean annual temperature （MAT）， and soil bulk density （SBD）. MBP was negatively correlated with aridity， MAT， and soil pH. The microbial biomass carbon-nitrogen ratio （Mcn） was significantly negatively correlated with mean annual precipitation （MAP）， the microbial biomass carbon-phosphorus ratio （Mcp） was significantly positively correlated with aridity， and the microbial biomass nitrogen-phosphorus ratio （Mnp） was significantly positively correlated with soil pH. Random forest analysis indicated that MAP， aridity， and soil pH were the main driving factors of microbial biomass. This study deepened our understanding of the response of soil microorganisms to climate change and provided theoretical support for protecting the nutrient cycling function of grassland ecosystems.

Inner Mongolia grassland  /  Soil microbial biomass  /  Stoichiometric ratios  /  Biotic and abiotic factors