Impacts of increased N use and precipitation on microbial C utilization potential in the semiarid grassland of Inner Mongolia
施氮和增雨对内蒙古半干旱地区草原土壤微生物群落碳源利用潜力的影响

Plant community structure and composition have been noted to be sensitive to climate change and N deposition in the semiarid grassland of northern China. Despite this fact, little research has been conducted on the response of microbial community in this semi-arid grassland region. The aim of this study was to assess the variations in soil microbial C utilization potential under future scenarios of changes in precipitation and N deposition in the semiarid grassland of northern China. C utilization potential of soil microbial community was determined at community-based physiological profiles in a 3-year field experiment. To simulate changes in precipitation and N deposition in the area under the future scenario, increased precipitation and N treatments were performed in a experiment field in the semiarid grassland at Inner Mongolia. Based on the study, N application and increased precipitation changed the soil environment that in turn significantly influenced soil microbial C utilization. While increased precipitation increased soil moisture and soil organic matter, N application or N application combined with increased precipitation increased soil dissolved inorganic N and decreased soil pH in the semiarid grassland of the study area. Neither sole application of N nor increased precipitation influenced soil microbial C utilization potential. Positive interactions between increased precipitation and N application enhanced microbial C utilization potential, which implied that microbial C utilization potential was somewhat inactive until N and water were available in sufficient amounts. The response of soil microbial community to increased precipitation and N application confirmed the hypothesis that combined increase in precipitation and N application influenced microbial communities in semiarid grasslands. This enhanced microbial C utilization potential with possible acceleration of the C cycle due to future increases in precipitation and N deposition in the semiarid grassland of North China. Correlations between soil microbial C utilization potential and soil/plant factors suggested that soils, microbes and plants reacted with simultaneously increase in precipitation and N application.