季节性放牧对内蒙古典型草原N2O排放的影响及其微生物机制

For the current lack of the responsible microbial mechanism of soil N2O emission flux from different seasonal grazing in a semi-arid grassland. It had fatal research significance on N2O mitigation and greenhouse effect. We conduct this research through N2O emission observation; using incubation and Q-PCR method to determine the impact of different seasonal grazing on the N2O produce rates from nitrification and denitrification processes and gene abundances of AOA, AOB, narG, nirK/S and nosZ which related to N2O emissions in soil.Therefore, the coupling relation were determined among different seasonal grazing, soil N2O emissions, N2O produce rates and affected factors(grassland production, biodiversity, ammonia nitrogen and nitrate nitrogen, soil organic carbon, and pH), and soil microbe. This would help to explore the microbial mechanism of soil N2O emission in semi-arid grassland of different seasonal grazing. Orientation regulation on nitrogen transformation, and finding mitigation measure were concerned by this study. This research would provide scientific foundation for these research.

氧化亚氮(N2O)不仅是重要的温室气体，其排放也是草原氮损失的重要途径。放牧是草原利用的主要方式，对草地氮循环的影响存在季节性变化。开展不同季节放牧对内蒙古典型草原N2O排放特征影响及微生物机理研究，对于准确估算区域N2O的温室效应和探讨其产生机理具有重要意义。本研究通过控制实验设置围封、生长季初期、盛期、末期和全季节放牧5个处理在生长季高频观测草原生态系统N2O排放特征；通过乙炔抑制法和荧光定量PCR分析生长季不同时期的土壤硝化、反硝化活性及相关微生物功能群（AOA, AOB, narG, nirK/S和nosZ）数量的变化，阐明N2O排放、硝化、反硝化过程及相关微生物功能群对不同季节放牧的响应机制，解析季节性放牧、土壤N2O产生、排放和关键影响因子(草地生产力、多样性、铵态氮和硝态氮、有机碳、pH)及其土壤微生物特征之间的耦合关系，揭示季节性放牧草原土壤N2O产生与排放的微生物学机制。

本项目以中国北部锡林浩特典型草原为研究对象，基于草地适应性利用原理开展典型草原季节性放牧利用对氧化亚氮产生过程及排放的影响研究，具体研究包括:1）季节性放牧对氧化亚氮排放及环境因子影响的监测；2）硝化、反硝化过程微生物功能群及其活性分析；3）影响放牧草地土壤N2O排放因素与微生物学机理解析等。本项目研究表明:（1）全季节放牧对土壤氮循环过程影响较大，造成了草地一定程度的退化；（2）季节性放牧可以有效的减缓草地退化过程，生长季初期和盛期放牧会一定程度的加速土壤氮循环过程，但长期看还存在加速氮损失并造成草地退还的可能；（3）生长季末期放牧有利于草原生态系统的稳定;（4）放牧活动主要通过调节水分影响硝化过程、主要通过调节土壤养分来影响反硝化过程从而影响N2O通量。该结论对于理解放牧对内蒙古典型草氮循环过程的影响机制具有重要的理论意义，同时也为优化内蒙古草原农牧业管理措施，为草地的恢复、保护和管理提供了科学依据与指导。