青藏高原多年冻土区沼泽草甸和草甸CH4和N2O的释放及机制

The Qinghai-Tibetan Plateau occupies the largest low-latitude permafrost in the world and the greenhouse gas emissions from this region may affect the regional and even global climate. Many studies have been performed on the CO2 emissions, while little is known about the CH4 and N2O emissions. The present study will select the meadow and wet meadow, which store high stocks of soil organic carbon, in the permafrost regions on the plateau as study areas. The emission patterns of these two greenhouse gases will be examined by using continuous monitoring the CH4 and N2O fluxes. The soil hydro-thermal conditions will be also monitored. The soil physico-chemical variables and stable isotope compositions of soil organic carbon will be also analyzed. The quantitative descriptions of effects of hydrothermal conditions and soil variables on greenhouse gas emissions will be investigated using statistical analysis. Using real time qPCR, we will also quantify the functional genes which are associated with the production of these two greenhouse gases. The structure of bacteria which are associated with N2O production and Archaea will be also investigated by high throughput sequencing. Based on these data, the microbial mechanisms for the greenhouse gas emissions will be analyzed. The results will provide us with the knowledge of CH4 and N2O emissions and their patterns in the soils under alpine wet meadow and meadow in the permafrost regions on the Qinghai-Tibetan Plateau. In addition, the microbial mechanisms under the greenhouse gas emissions which are driven by soil variable during the freeze-thaw cycles will be also proposed. The result will supply data for the possible changes in the CH4 and N2O emissions under future global warming and permafrost degradation scenarios and thus also provide knowledge for the cryospheric science, as well as well as scientific basis for the environment protection of alpine ecosystem on the plateau.

青藏高原是世界上最大的中低纬度多年冻土分布区，其土壤温室气体的释放会影响区域乃至全球气候。目前关注的重点主要是CO2的释放，而对CH4和N2O这两种重要的温室气体研究还较少。本研究选择青藏高原多年冻土区有机质储量高的沼泽草甸和草甸为研究对象，连续监测CH4和N2O的释放情况，分析其释放规律；监测活动层水热过程，分析土壤理化性质及13C同位素，通过统计分析，研究土壤水热特征、理化性质对温室气体释放的影响；选择对应的功能基因，利用实时荧光定量PCR法和高通量测序法，测定功能基因丰度和微生物群落结构，研究CH4和N2O释放的微生物机制。结果可认识高原多年冻土区沼泽草甸和草甸CH4和N2O的释放及其规律，以及冻融循环过程中水热变化驱动的CH4和N2O释放的微生物机制。结果有助于认识全球变化背景下多年冻土退化对这两种温室气体排放的可能影响，进而为冰冻圈科学的发展提供资料，并为高原环境保护提供参考。

本项目选择青藏高原多年冻土区有机质储量高的沼泽草甸和草甸为研究对象，通过室内培养和野外监测，分析甲烷和氧化亚氮的释放情况，研究其释放规律并分析其与环境因子及微生物群落的关系，结果表明，在青藏高原草甸和沼泽草甸地区，甲烷的季节排放通量总体呈单峰曲线，在8、9月到达了最高峰。高海拔（4100m-3900m）高寒沼泽草甸地区为重要的甲烷源，而中部（3700-3500）高寒草原以及低部（3300-3100）高寒草甸是重要的甲烷汇。相关分析结果表明，草甸和沼泽草甸土壤含水率和电导率是影响甲烷通量的主要因素。mcrA基因丰度与甲烷通量呈正相关关系，pmoA基因丰度与甲烷通量无明显关系。mcrA基因丰度随海拔有着明显的上升趋势，pmoA基因丰度随海拔无明显变化。微生物的群落多样性与土壤中的总碳和土壤有机碳呈正相关。可见，水分、温度、有机质含量与甲烷氧化菌的基因丰度是影响草地生态系统甲烷源汇效应的主要因素。而在氧化亚氮的研究中，发现沼泽草甸和草甸地区的氧化亚氮释放的变化范围很大，与环境因子及相关的功能微生物基因丰度之间没有显著规律；同样，在室内的有氧培养和厌氧培养过程中，都有氧化亚氮的释放，但是其氧化亚氮的产生速率变化很大，结果表明青藏高原草甸和沼泽草甸土壤中产生氧化亚氮的硝化和反硝化过程和影响因素十分复杂，以植被类型和季节因素来考虑不足以确定其释放的规律。项目执行期间，发表SCI论文15篇（中科院一区论文13篇），中文核心论文9篇，培养博士生2名，硕士生5名。