不同增温幅度和刈割对高寒草甸温室气体平衡的影响及其机制

The sink and source of greenhouse gas (CO2, CH4, N2O) fluxes in alpine ecosystems and their responses to climate warming and human activity is one of the most significant uncertainties in global change ecology. Previous manipulated warming experiments at alpine regions have mainly evaluated carbon fluxes and focused on growing season, however, much less work has been done in quantifying the annual balance of three greenhouse gases and its response to different warming levels. Thus, with a manipulated experiment of warming (unwarming, +1.5°C,+ 3.0°C) and mowing (unmowing, mowing) in an alpine meadow on the Qinghai-Tibetan Plateau, the greenhouse gas fluxes in both growing and non-growing seasons were measured by using automatic multi-chamber observation system for the CO2, CH4, N2O fluxes and closed chamber method. Based on the field investigations and laboratory analysis, this study aims to investigate the CO2, CH4, and N2O fluxes and greenhouse gas balance in response to varying warming levels and mowing, moreover, in order to compare the differences in the responses between the growing and non-growing seasons and explore the microbial mechanisms that regulate the responses of greenhouse gas fluxes to warming and mowing. This study will provide parameter test and model verification for modeling and predicting the responses of alpine grasslands to climate warming and mowing. It will also contribute to make effective management measures to reduce greenhouse gas emissions for the alpine ecosystems.

高寒生态系统温室气体（CO2、CH4、N2O）通量对气候变暖和人类活动的响应和反馈是全球变化生态学研究中最具不确定性的科学问题之一。以往高寒地区模拟增温控制实验主要关注碳通量且集中于生长季，很少综合考虑年尺度上三种温室气体平衡对不同增温幅度的响应。本项目拟以青藏高原高寒草甸生态系统为研究对象，基于野外增温（不增温，1.5°C增温、3.0°C增温）和刈割（不刈割、刈割）交互控制实验，采用全自动多通道温室气体通量协同观测系统和静态箱法测定全年CO2、CH4和N2O通量，并结合野外生态调查和室内分析，揭示CO2、CH4、N2O通量和温室气体平衡对不同增温幅度和刈割的响应特征；比较非生长季和生长季温室气体通量的响应差异；探明温室气体通量对不同增温幅度和刈割响应的微生物学机制。该研究将为模拟和预测高寒草地生态系统对气候变暖和刈割的响应提供参数检验与模型验证，并有助于制定有效的温室气体减排措施。

高寒生态系统温室气体（CO2、CH4、N2O）通量对气候变暖和人类活动的响应和反馈是全球变化生态学研究中最具不确定性的科学问题之一。以往高寒地区模拟增温控制实验主要关注CO2通量且集中于生长季，很少考虑CH4和N2O通量以及年尺度上三种温室气体平衡对气候变暖的响应。基于不同增温幅度和刈割控制实验，我们发现增温3oC显著增加了CH4吸收，降低了N2O释放，而刈割对这两种温室气体均没有显著影响；增温对CH4吸收的影响主要集中在生长季，而对N2O释放的影响主要发生在非生长季。当进一步同时考虑三种温室气体平衡时，研究发现增温3oC使得生态系统从一个净的温室气体汇转变为源，且增温引起的温室气体源汇关系的转变主要由非生长季CO2释放增加所引起的。这些发现强调了将全球温度上升控制在2oC以内的重要性以及非生长季温室气体通量对年尺度温室气体平衡的贡献，对于改进地球系统模式、预测生态系统与气候变暖的反馈关系具有重要意义。