海拔梯度变化对高寒草甸土壤N2O功能微生物的影响

N2O is one of the important damage material for atmospheric ozone and greenhouse gases and become the focus of all of the world. Most of the reseachers only mensurated the flux of N2O in different environments and not open out its producing mechanism.The impact of climate change on N2O emmission and its microbial driving mechanism are still unclear. Soils account for over 65% of the total of N2O in the atmosphere, and most of them is emission by denitrification and nitrification processes microbe-mediated. The Qinghai-Tibetan Plateau is thought to be one of the areas least distributed by human activities, in China or the world. It is the highest and youngest plateau in the world and was named "The third pole of the Earth"for its unique location. The alpine meadow is a typical vegetaion types in Qinghai-Tibetan Plateau. In this project,we will select typical alpine meadow soils dominant by Kobresia along the elevation gradient and use metagenomic sequencing and microbial functional Geochips and other molecular biology methods in combination with survey data for N2O emission,to study the effect of elevation gradient change on N2O emission,the microbial diversity of denitrification and nitrification processes and their activity. With the development and application of high throughout metagenomic approaches based on direct extraction DNA from environment samples, such as pyrosequencing-based and microarray-based metagenomics technologies, large data sets allowed the exploration of the microbial taxonomic and functional activity can be rapidly obtained in diverse ecosystems，thus making it possible to link the functional structure of microbial processes with ecosystem processes. The contribution of denitrification and nitrification for N2O emission the alpine meadow and their driving mechanism for climate change by mediated-microorganism will be analyzed.These study result will provide support for reduce the uncertainty for increasing N2O emission,and accurated evaluation the contribution of alpine meadow on global climate change and forecast the global nitrogen dynamics.

N2O是重要的大气臭氧层破坏物质和温室气体之一，已成为全社会关注的焦点问题，N2O的排放主要由微生物控制，已有研究大多停留在对N2O排放通量的表观测定上，较少对机理进行研究。本项目将选择青藏高原5个不同海拔高度的嵩草属(Kobresia)为优势种的高寒草甸为研究对象，应用宏基因组测序、微生物功能基因芯片、荧光定量PCR等技术和功能分子生态网络分析等方法，结合N2O排放和相关环境因素等，研究海拔梯度变化对土壤N2O排放的影响，研究海拔梯度变化对参与硝化和反硝化作用关键功能微生物的多样性及其功能基因表达活性差异；阐明硝化和反硝化作用对土壤N2O排放的贡献；分析海拔梯度变化对土壤N2O排放影响的微生物驱动机制；以空间代替时间，探讨气候变化对土壤N2O排放的影响。项目的实施将有助于降低对N2O增长原因认识的不确定性，并为准确评估高寒草甸对气候变化的贡献和预测氮的动态变化提供科学依据。

为了研究海拔梯度变化对高寒草甸土壤微生物和N2O功能微生物的影响，本项目在青藏高原三江源国家级自然保护区沿着海拔梯度（3200m-4800m），设立了6个（海拔梯度间隔200-300m）不同海拔高度的高寒草地研究样地。应用高通量测序、微生物功能基因芯片、Biolog生态板等技术和功能分子生态网络分析方法等，结合植物多样性、土壤N2O通量和氮循环相关地球化学成分监测等数据，研究了海拔梯度变化对高寒草地土壤微生物群落结构、多样性和微生物功能基因多样性的影响，特别是与N2O循环密切相关的微生物功能多样性的影响。研究初步揭示了青藏高原高寒草甸的主要土壤微生物物种和功能基因类群特征，特别是介导土壤硝化和反硝化的微生物功能基因多样性；表明海拔梯度变化对高寒草甸土壤微生物群落结构和N2O功能微生物将产生不同的影响，大多数参与氮循环的功能基因(e.g. nifH, amoA, nosZ 和nirK)的相对丰度随着海拔的降低而增加，氮循环相关功能基因的相对丰度与土壤总氮和有效氮具有显著的相关性；分析了土壤微生物介导的硝化和反硝化作用对氮循环过程的影响，综合分析了环境因素影响，探讨了气候变化对碳氮功能微生物的影响及其微生物驱动，并表明氮循环相关功能微生物可能具有较碳降解相关功能微生物更快的响应。项目的实施，在GenBank数据库提交了一批基因序列，完善了相关数据库；已发表论文7篇，另有4篇在审稿中，其中在Molecular Ecology等发表SCI论文3篇。