全球变化对中国湿地生态系统CO2和CH4源汇功能的影响及其机制

Wetlands have ability to simultaneously sequester CO2 and emit CH4, so wetlands may potentially generate negative climate feedbacks and positive feedbacks depending on the sink or source of CO2/CH4 from wetlands. It is still unknown whether wetlands act as a climate “mitigation” or “amplifier” in the context of global change. Wetland area in China has a dramatically decrease and functions of wetlands also changed during the past few decades, because of climate change and human activities. Meanwhile, more and more wetlands in China are under protection and restoration by Chinese government, and the protected and restored wetland area will continue to increase in the future. Thus, it is essential to know that the impacts and drivers of global change on CO2/CH4 fluxes of wetlands in China and whether wetlands in China contribute to climate change mitigation? In this project, we plan to compile CO2/CH4 observation data from sites, meteorological and remote sensing data, and to use data assimilation and terrestrial biosphere model to explore the changes in spatial-temporal patterns of wetlands CO2/CH4 fluxes on both site scale and national scale and their drivers. Then we try to predict wetlands CO2 and CH4 fluxes in the future under different climate and management scenarios. Furthermore, an assessment about the climate feedbacks of wetlands will be comprehensively quantified. This project will not only help improve our knowledge about the responses of wetlands CO2/CH4 fluxes to global change and their mechanisms, but also provide guidelines for future policies about climate mitigation and wetland management for Chinese government and shareholders.

湿地一般被认为既是大气CO2重要的“汇”又是大气CH4重要的“源”，湿地的综合气候效应减缓还是加剧气候变化仍不确定。过去几十年，在气候变化和人为活动干扰下，中国湿地不仅面积锐减而且功能也发生了巨大变化。我国政府计划增加未来湿地保护和恢复的面积和质量。那么，中国湿地CO2和CH4源汇功能对全球变化如何响应？其综合温室效应减缓还是加剧气候变化？本项目拟利用站点观测数据，遥感和气象数据，结合数据同化和陆地生态系统过程模型，探讨站点尺度和国家尺度上我国湿地CO2和CH4源汇功能时空格局的变化及其机制，并探讨在未来不同气候变化和湿地管理情景下我国湿地CO2和CH4源汇功能时空格局变化。在此基础上，定量评估我国湿地CO2和CH4源汇功能的综合气候效应。本项目的实施不仅有助于提高对我国湿地CO2和CH4源汇功能对全球变化响应机制的认识，而且为我国制定气候减缓和湿地管理政策提供科学依据。

湿地一般被认为既是大气CO2的汇又是大气CH4的源，湿地的综合气候效应是减缓还是加剧气候变化仍不确定。中国湿地CO2和CH4源汇功能和综合气候效应如何响应全球变化不仅具有重要的科学意义，也会为我国制定减缓气候变化和湿地管理政策提供科学依据。本项目整合地面站点观测数据、遥感数据和模型模拟，研究全球变化对湿地CO2和CH4源汇功能和综合气候效应的影响，取得了以下成果：（1）改进了湿地动态和CO2和CH4源汇功能模块，基于站点观测数据优化了模型参数，提高了模型对中国湿地CO2和CH4源汇功能的模拟精度；（2）模拟了近40年气候变化对中国湿地CO2和CH4源汇功能的影响，探讨了模型模拟的不确定性，揭示了中国湿地整体的综合气候效应减缓了气候变化；（3）模拟了未来三个气候变化情景下(SSP1-2.6, SSP3-7.0和SSP5-8.5)中国湿地CO2和CH4源汇功能的变化，阐明了未来三个情景下到本世纪末中国湿地综合气候效应仍表现为减缓气候变化，而不同土地利用变化情景对中国湿地甲烷排放和碳汇的影响不同。研究结果揭示了我国湿地恢复和保护同时具有减缓气候变化的协同效应，为我国湿地保护和气候变化减缓政策制定提供了科学依据。