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

Impacts of increased N use and precipitation on microbial C utilization potential in the semiarid grassland of Inner Mongolia

已有许多研究证明,中国北方草地生态系统的植物群落结构和组成对气候变化和氮沉降较为敏感,但是关于草原土壤微生物群落响应多重环境因子变化方面的研究较薄弱。水和氮是陆地生态系统生产力的两大限制性因子。本研究在内蒙古多伦半干旱草原地区进行增雨和施氮的野外控制试验,以模拟未来该地区的降水变化和氮沉降,使用微生物群落水平生理图谱法,监测样地土壤理化指标和土壤微生物群落碳源利用潜力的变化。3年的跟踪监测结果显示:增雨显著提高了半干旱草原地区土壤含水量和有机质含量;施氮和增雨同时施氮则显著提高了土壤可溶性氮含量,降低了土壤pH;施氮和增雨都没有单独引起土壤微生物群落碳源利用潜力的显著变化,而在同时增雨和施氮试验处理下,微生物群落碳源利用潜力得到提高,说明在水和氮都充足的条件下,土壤微生物碳源利用潜力才会显著提高。以上研究结果预示着在未来降雨增加和氮沉降的全球变化背景下,中国北方半干旱草地生态系统的碳循环速率可能会加快。

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.