内蒙古温带草原土壤微生物生物量碳的空间分布及驱动因素

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

【目的】探索内蒙古温带草原土壤微生物生物量碳的空间分布特征以及驱动因素。【方法】在内蒙古自治区境内沿着年均温、年降水梯度选择17个草原样点,在土壤剖面上分0-10 cm、10-20 cm、20-40 cm、40-60 cm、60-100 cm五层,分别采集土壤样品,测定土壤微生物生物量碳以及主要的环境和生物影响因子,分析不同草地类型以及不同土壤深度土壤微生物生物量碳的差异,探索非生物因子和生物因子对土壤微生物量碳的影响。【结果】草甸草原土壤微生物量碳最高,典型草原次之,荒漠草原最低。在0-10 cm土壤中,草地类型间的微生物量碳变异系数高于草甸草原和典型草原,低于荒漠草原;在0-100 cm土壤中,草甸草原样点间的微生物量碳的变异系数低于典型草原和荒漠草原。土壤微生物量碳与年降水、土壤含水量、粘粒含量、土壤养分元素、地上生物量、地下生物量呈显著正相关,与年均温和土壤p H值呈显著负相关关系。随着土壤深度的增加,土壤微生物量碳显著减少,非生物因子与微生物量碳的相关性减弱,草地类型间以及同一草地类型不同样点间的变异系数增加。0-10 cm土壤微生物量碳与10-40 cm土壤微生物量碳的相关指数高于0.5,与40-100 cm的土壤微生物量碳的相关指数小于0.3。【结论】内蒙古温带草原土壤微生物量碳的垂直分布呈现一定的规律性,且非生物因子对微生物量碳的影响也呈现垂直减弱的规律。

[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 p H 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.