基于原位观测和机理模型研究青藏高原自然生态系统CH4源汇现状及动态

Being the second largest long-live greenhouse gas, methane (CH4), the natural ecosystems play a role in regulating its concentration in the atmosphere. The Tibetan Plateau, TP in short, contributes roughly 30% and 40% of China’s natural wetlands and grasslands, respectively. Thus, it’s expected to be a vital player in CH4 cycle. During the past two decades, efforts have been made to measure and quantify the CH4 exchanges on the TP, overcoming the harsh climate, altitude sickness and lack of traffic accessibility. However, there still remains large uncertainty regarding the function of the TP in CH4 cycle and its magnitude, due mainly to lack of an integrated study. Furthermore, the rapid warming and wetting climate, as well as non-linear variation of wetland extent of the TP, also made the CH4 budget more uncertain. Therefore, the tasks of this study are triple: (1) to conduct in-situ measurements of CH4 exchanges of the natural ecosystems, especially on the western TP; (2) to simulate and estimate contemporary CH4 budget of the natural ecosystems of the TP, by revising and calibrating a process-based model; (3) to understand how the CH4 budget of the TP was affected by the changing climate during the past three decades, forced by dynamic wetland extent maps and high-spatial/temporal-resolution climatological datasets. This study dedicates to integrate different methods, i.e., in-situ measurement, literature synthesis and model simulation, to quantify contemporary CH4 budget of the natural ecosystems of the TP, as well as to understand how and to what extent the CH4 budget of the TP was affected by the changing climate, directly and indirectly.

CH4是第二大长寿命温室气体，自然生态系统在调节其浓度中发挥着重要的作用。青藏高原占我国天然湿地的30%和天然草地的40%，是重要的CH4源汇功能区。过去二十年，中国科学家克服高寒缺氧和路途艰险的困难，在定量CH4源汇通量方面取得了长足进展。但由于缺乏机理性和集成性研究，青藏高原自然生态系统源汇性质和强度仍极大不确定，同时还面临着来自气候暖湿化和湿地面积非线性变化的影响。因此，本研究拟：（1）在申请人前期工作基础上，开展高原中西部地区典型生态系统CH4通量的原位和机理性观测；（2）基于观测改进机理模型，模拟青藏高原自然生态系统CH4源汇现状；（3）在以上基础上，研究过去30年气候变化和湿地面积/格局变化影响青藏高原CH4源汇变化的过程和程度。本项目旨在通过原位观测、资料汇总和机理模型的集成，定量青藏高原自然生态系统CH4源汇现状，并理解气候变化直接和间接影响其CH4源汇的过程和程度。

CH4是第二大长寿命温室气体，自然生态系统在调节其浓度中发挥着重要的作用。青藏高原占我国天然湿地的30%和天然草地的40%，是重要的CH4源汇功能区。过去二十年，中国科学家克服高寒缺氧和路途艰险的困难，在定量CH4源汇通量方面取得了长足进展。然而，由于缺乏集成性的研究，青藏高原自然生态系统源汇性质和强度仍极大不确定，同时还面临着来自气候暖湿化和湿地面积非线性变化的影响。因此，本项目通过原位观测和机理模型模拟，得到如下结论：（1）青藏高原高寒湿地CH4释放低于预期，并呈现出显著的海拔格局；（2）青藏高原高寒生态系统总体是弱的CH4源，非湿地生态系统在调节CH4源汇平衡方面发挥着重要作用；（3）气候暖湿化及湿地恢复性增长驱动青藏高原高寒生态系统CH4平衡向源转换，将对气候系统形成正反馈。通过原位观测、资料汇总和机理模型的集成，本项目定量了青藏高原自然生态系统CH4源汇现状，理解了气候变化直接和间接影响其CH4源汇的过程和程度。