退牧还草工程生态效益逆转监测评价及其驱动力机制研究

The returning grazing lands to grasslands (RGLG) project is a powerful guarantee for promoting ecological benefit reversal of the degraded grassland. Thus, dynamic monitoring and evaluation of the ecological benefits of RGLG project and exploring its driving force mechanism play an important role in understanding the eco-environmental changes of degraded grassland, optimizing the process management modes, and raising the ecological comprehensive monitoring levels. But so far, the ecological benefits of the RGLG project and their driving mechanisms at larger scale are not clear yet. In this project, key implementation counties of RGLG project are taken as the research area, some innovative tasks will be carried out as follows: (1) to study on grassland community composition information detection by multi-source remote sensing and optimized multiple endmember spectral mixture analysis; (2) to build an ecological benefit reversal index and propose a new practical method of large area remote sensing monitoring of eco-environmental benefit based on grassland vegetation and soil indicators; and to explore the carbon source or sink benefit of this project; (3) to quantitative assess on the contributions of climate change and human activities in ecological benefit reversal and revealing its driving mechanism. This study aims to explore degraded grassland eco-environmental changes from a new perspective of “reversal”, and the “ecological benefit reversal index” should be presented in this project will rich the theories and methods of eco-environmental benefit evaluation, and provide a model for similar research and practice. At last, results of this project will provide important theoretical and data support for reasonable planning of the RGLG project and space management decision-making of grassland resources.

退牧还草工程是促进退化草地生态效益逆转的有力保障；动态监测评价其生态效益及驱动机制，对准确认识退化草地生态环境变化、优化其过程管理模式和提高生态综合监测水平具有重要作用。但迄今对大尺度退牧还草工程的生态效益及驱动机制尚不明晰。本项目选用退牧还草工程重点实施县为研究区，拟开展如下研究工作：（1）利用多源遥感和优化多端元混合像元分解探测草地群落组成信息；（2）基于模型模拟和光谱分析获取草地植被和土壤指标，以构建生态效益逆转指数，形成实用化大面积生态环境效益遥感监测新方法；并探究生态工程的碳源/汇效应；（3）量化驱动草地生态效益逆转的气候和人为因子，揭示其成因机制。本研究从“逆转”的新视角探究退牧还草背景下退化草地的生态效益变化，所提出的生态效益逆转指数将丰富生态环境效益评价的理论和方法，为同类研究提供示范和借鉴；研究结果将为我国退牧还草工程的合理规划和草地资源空间管理决策提供重要的科学依据。

草地是陆地生态系统的重要绿色屏障，然而伴随全球气候变暖和人类活动干扰的加剧，草地退化沙化加速，带来众多生态环境问题；为了扭转草地退化局面，国家开展了退牧还草等生态恢复工程。那么在气候变化和生态恢复措施下，退化草地是否恢复、气候和人类活动谁是主导因子、空间格局特征等如何？基于此，本项目从生态效益“逆转”的新视角，选取三江源区和鄂尔多斯市为研究区，通过生态遥感耦合模型模拟和野外实测获取植被（覆盖度、NPP、NEP、毒杂草）与土壤指标（SOC），以此构建生态效益逆转指数，评价退化草地生态效益逆转现状；探究退牧还草工程的碳源/汇效应和空间格局；基于净初级生产力，量化气候和人类活动因子对生态效益逆转的贡献率，揭示生态效益逆转的成因机制和格局特征。.本项目取得的重要结果为：（1）鄂尔多斯市和三江源区退化草地生态效益逆转的面积分别占该各自草地总面积的32.3%和10.4%。无论从单因子（覆盖度、NPP、NEP、SOC），还是生态效益综合逆转水平和等级上，鄂尔多斯草地逆转状况都优于三江源区，说明鄂尔多斯市生态修复工程效果显著；三江源区典型毒杂草光谱具有明显高台反射区。（2）鄂尔多斯市和三江源区草地植被均表现为碳汇功能，年均碳汇总量分别为7.2TgC和24.8TgC。（3）定量化评估显示：鄂尔多斯市气候和人类活动的驱动贡献率分别为21.2%和78.8%；三江源区气候和人类活动的驱动贡献率分别为71.5%和28.5%；表明驱动鄂尔多斯和三江源区退化草地逆转的主导因子分别是人类活动和气候因子。.通过本项目研究，系统揭示驱动退化草地逆转的成因机制和空间分布，构建的生态效益逆转评价体系和定量化评估方法，可为大区域草地生态环境监测和驱动机制的定量评估提供理论参考，也为退牧还草工程精细化开展和草地资源管理提供数据支撑。.