青藏高原草地退化/恢复对水源涵养服务的影响及机理研究

Qinghai-Tibetan Plateau is an important ecological barrier region in China. Water conservation service is the core service in many ecological barrier functions. The research on influence factors and mechanisms of water conservation service is required by China government to guarantee the national ecological security. Plenty of Government Programs, ecological conservation measures, and ecological conservation projects had been put into effect in this region. So, it demands to study relevant scientific proposition urgently. So far, how to reveal the water conservation service of grassland ecosystem quantitatively, how to evaluate the effect of project measures, how to recognize the contribution between climate change and ecological projects, are still difficult to meet the needs of government..In our research, it is a main line to reveal the mechanisms between grassland degradation/restoration and water conservation service. Naqu and Yushu have been selected as study area. Based on the knowledge mining of literature, many influence factors of water conservation will be filtered, which can be used to build the grassland ecosystem evaluation model of water conservation. Under the support of observation data and sampling data, the mechanisms of grassland degradation/restoration and water conservation could be concluded. Within the remote sensing method, a spatial-temporal patterns can be simulated by the model to describe the evolution process of water conservation service. At last, scenario analysis technology will be used to recognize the contribution between climate change and ecological project. Also, a set of integrated scenario, which is coupling of climate change and ecological project, will be built before contribution recognization.

青藏高原是我国重要的生态屏障区，水源涵养服务是其众多生态屏障功能中的核心服务，对水源涵养服务影响因素和作用机理的研究是保障国家生态安全的需要。国家在该区实施了一系列的生态规划、保护与建设项目，对相关科学命题的研究提出了迫切需求。目前，定量揭示草地生态系统水源涵养服务、评估工程措施成效、厘定气候与工程建设贡献等方面的研究仍难以满足现实需要。.本研究以揭示草地退化/恢复对草地生态系统水源涵养服务的影响机理为主线，选择西藏那曲地区和青海玉树地区为研究区，基于对文献资料的知识挖掘，定量描述水源涵养服务的影响因素，构建草地生态系统水源涵养服务评估模型；在样点与观测数据的支撑下，分析草地退化/恢复对水源涵养服务的作用机理，并采用遥感手段，模拟区域草地生态系统水源涵养服务时空演化格局；在耦合气候变化与生态建设工程的未来情景下，通过多情景模拟与比较，厘定气候变化与生态建设工程对水源涵养服务的贡献。

近年来，生态文明建设作为国家“五位一体”总体布局的关键一环，关系到国家和民族的复兴进程。党的十九大提出，要加大生态系统保护力度，优化生态安全屏障体系，提升生态系统质量和稳定性。青藏高原是我国重要的生态屏障区，是我国主要大江大河的源头区，肩负着区域气候调节和下游水资源安全供给的多重职责，水源涵养服务作为该区域众多生态系统服务功能中的核心，其功能的高低直接影响着下游的生态安全。在资料稀缺的青藏高原地区，选择青海三江源作为典型研究区，通过遥感监测与模型模拟，建立了区域草地退化与恢复的时空变化过程，揭示了整个三江源地区在气候变化作用下，草地生态系统自2005年之后逐步恢复，黄河流域是草地恢复较为明显的区域。其次，通过模拟发现，在过去的30年中，三江源区多年平均降水量为587mm，蒸散量为452mm，年均蒸散量与年降水量呈现基本一致的波动趋势，空间分布呈现东高西低的基本格局。通过对三江源地区2020-2050年气候变化情景数据的分析发现，三江源区未来气候变化总体呈降水波动、显著增温的趋势，且2030年代中期之后，增温幅度加大。基于此数据，对不同气候变化模式下的蒸散格局进行了模拟，发现：2020-2050年三江源区蒸散发格局与降水及年均温格局基本一致，并受生态系统类型的明显影响，RCP4.5和RCP8.5情景的蒸散量增加明显高于RCP2.6情景。通过水量平衡法，发现：2030年代以后，三江源区产流量明显降低，水资源输出能力减弱。在全国生态保护红线划定工作中，青海省和西藏自治区都是我国生态保护红线占比较高的省份，尤其是青海三江源地区、西藏羌塘地区等，基本都纳入了生态保护红线的范围。本研究的相关成果对于掌握这些地区生态保护红线的基本状况，了解区域核心生态系统服务功能的影响因素和变化情况，预测未来生态系统服务功能变化提供了科学依据。