热融滑塌对高寒草甸区土壤有机碳分解及温室气体排放的影响-以俄博岭多年冻土区为例

Permafrost degradation affects carbon cycle, which has an important role in climate change. Thermokarst is a typical process that associates with permafrost degradation. One of the most striking features of thermokarst is thermal erosion. The thermal erosion increases soil temperature, and also changes soil moisture. In addition, thermal erosion can abruptly expose soil organic matter from meters below the ground surface, thus may play an important role in soil carbon cycle. However, little is known about the effect of thermal erosion on content and characteristic of organic carbon and greenhouse gas emission on the Qinghai-Tibet Plateau (QTP). We will investigate the effects of thermal erosion on organic carbon content and its chemical characteristics in a typical thermal erosion region over the Eboling Mountains in the northern QTP. The study will be conducted by analyzing the characteristics of soil organic carbon, dissolved organic carbon, microbial biomass carbon and stable carbon isotope from no erosion and eroded soil samples. The effect of ultra violet (UV) radiation on the decomposition of exposed organic carbon will be examined through incubation experiments under UV light conditions. The effects of hydrothermal condition change during thermal erosion on ecosystem carbon emissions will be investigated by monitoring soil temperature, moisture and ecosystem CO2 and CH4 fluxes. The results will be helpful to understand the mechanisms of carbon cycle during permafrost degradation, and provide scientific base for the environment study of permafrost regions.

多年冻土退化影响碳循环过程，并对气候变化有着重要影响。多年冻土退化最直观表现为热喀斯特，热融滑塌是其最显著特征之一。热融滑塌不仅升高土壤温度、改变水分条件，而且导致地下深层有机质暴露于空气中，因而必然对碳循环具有重要影响。但是目前青藏高原多年冻土区热融滑塌对有机碳含量、性质和温室气体排放的影响还不清楚。本研究选择高原北部俄博岭多年冻土区典型的热融滑塌区域，通过采集未滑塌和已滑塌样地土样，分析土壤有机碳、溶解性有机碳、微生物量碳和稳定性碳同位素特征，研究热融滑塌对有机碳含量及其化学性质的影响；通过设置有/无紫外光照条件下土壤培养实验，研究紫外辐射对滑塌暴露的有机碳分解性质的影响；利用野外监测滑塌微地貌的土壤温度、水分及高寒草甸生态系统CO2和CH4通量，研究热融滑塌引起的土壤水热变化对生态系统碳排放的影响。研究结果有助于深入认识多年冻土退化对碳循环过程的影响，并为生态环境研究提供参考。

多年冻土退化影响碳循环过程，并对气候变化有着重要影响。多年冻土退化最直观表现为热喀斯特，热融滑塌是其最显著特征之一。热融滑塌不仅升高土壤温度、改变水分条件，而且导致地下深层有机质暴露于空气中，因而必然对碳循环具有重要影响。本研究选择高原北部俄博岭多年冻土区典型的热融滑塌区域，研究热融滑塌对有机碳含量及其化学性质的影响；探讨微生物分解和紫外辐射对滑塌暴露的有机碳分解过程的影响；通过野外监测滑塌微地貌的土壤温度、水分及高寒草甸生态系统CO2和CH4通量，研究热融滑塌引起的土壤水热条件变化对生态系统碳排放的影响。研究结果表明热融滑塌不仅造成表层土壤碳氮损失约30%，也改变了有机质的化学性质，进而影响有机质的分解速率。热融滑塌引起的温度、水分和紫外光照等因素变化对生态系统碳排放具有重要影响。热融滑塌也改变了水文过程和土壤氧化还原条件，加速微生物反硝化作用。生长季节整个热融喀斯特地貌区由碳汇表现为碳源，但总体上减少CH4排放，加速了N2O排放速率。多年冻土退化对径流DOC输移及转化的影响与多年冻土退化过程和热融喀斯特具体发生的面积相关。本研究有助于深入认识多年冻土退化对碳循环过程的影响，并为生态环境研究提供参考。