Spatial pattern of soil microbial biomass carbon and its driver in temperate grasslands of Inner Mongolia

Abstract:

[Objective] We aimed to explore spatial pattern of soil microbial biomass carbon (C) and its driver in temperate grasslands of Inner Mongolia. [Methods] Soil samples were collected from 5 discrete depths (0?10 cm, 10?20 cm, 20?40 cm, 40?60 cm, 60?100 cm) for 17 study sites. The variations of microbial biomass C, major abiotic and biotic factors were analyzed across three community types and five soil depths. Effects of abiotic and biotic factors on microbial biomass C were evaluated. [Results] Soil microbial biomass C in meadow steppe was significantly higher than that of typical steppe and desert steppe. In 0?10 cm soil layer, coefficient of variation among different grassland types was higher than the variation among different sites within meadow steppe and typical steppe and lower than desert steppe. In 0?100 cm soil layer, coefficient of variation among different sites in meadow steppe was lower than typical steppe and desert steppe. Soil microbial biomass C showed significant positive correlation with mean annual precipitation, soil moisture, clay content, soil nutrient content, aboveground biomass and root biomass and negative correlation with mean annual temperature and soil pH value. With the increase of soil depth, soil microbial biomass C, coefficients of variation among different sites in the same grassland type and among different grassland types all decreased significantly. Relationship between soil microbial biomass C and abiotic factors weakened with soil depth increase. Correlation index between soil microbial biomass C in 0?10 cm soil layer and 10?40 cm soil layer was more than 0.5. Nevertheless, correlation index of microbial biomass C between 0?10 cm soil layer and 40?100 cm soil layer was less than 0.3. [Conclusion] Soil microbial biomass C in temperate grasslands of Inner Mongolia showed obvious vertical distributions. Besides, the effects of abiotic factors on soil microbial biomass C dramatically declined with soil depth.