Objective This study aimed to make sure the characteristics of soil microbial biomass and its stoichiometry in the process of alpine meadow shrubification in the Qinghai-Tibet Plateau.

Method The shrub patches, shrub-grassland patches and grassland patches were selected in the alpine meadow shrubification area of the Three Rivers Source Region in the Qinghai-Tibet Plateau, and the microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) were analyzed at soil depths of 0 ~ 100 cm. Chi-square tests, ordinary least squares methods, and variance decomposition methods were used to study the MBC, MBN, MBP, and their stoichiometry under different patches, and to analyze their regulatory factors.

Result Among them, with the increase of soil depth, MBC and MBN showed a decreasing trend. There was no clear change pattern in MBP, MBC∶MBN, MBC∶MBP, and MBN∶MBP among shrub patches, shrub-grassland patches, and grassland patches. With the increase of soil organic carbon, easily decomposable organic carbon I, easily decomposable organic carbon II, difficultly decomposable organic carbon, soil total nitrogen, soil total phosphorus, soil temperature, and soil humidity, MBC and MBN showed a significant increasing trend; while with the increase of soil pH and soil bulk density. MBC and MBN showed a decreasing trend. MBP was a significantly positive correlation with soil organic carbon, easily decomposable organic carbon II, difficultly decomposable organic carbon, and total nitrogen, while it had a significantly negative relationship with soil pH and soil bulk density.

Conclusions Soil physical and chemical properties can significantly affect MBC, MBN and MBP, while their influence on the stoichiometric characteristics is relatively weak.