气候变化对长江源地区高寒草甸生态系统的影响

近十几年来，长江源区气候暖干化趋势明显，冰川退缩、湖泊萎缩、草场退化、土地沙漠化、水土流失等环境问题日益严重。高寒草甸是长江源地区主要的植被类型之一，在全球变化影响下，以耐低温寒冷的嵩草属（Kobresia）植物为建群种的高寒草甸将面临更严重的生态胁迫。以长江源地区高寒草甸生态系统为研究对象，采用国际通用的生物地球化学模型模拟高寒草甸生物量、生产力和土壤有机质等的动态变化，并综合考虑人类活动对生态系统生产力和营养元素生物地球化学循环的影响，探讨了全球气候变化对高寒草甸生态系统可能造成的影响。

IMPACTS OF GLOBAL CHANGE ON THE ALPINE MEADOW ECOSYSTEM IN THE SOURCE REGION OF THE YANGTZE RIVER

The source region of the Yangtze River, located in the middle region of the Tibetan Plateau, is characteristic of high-altitude and cold environment, and is a sensitive area to global change. As a major part of the National Three River Sources Nature Reserve, it is one of the principle areas of alpine wetlands as well. While in recent decades, in the influence of improper human activities and global climate changes, climate in this region has become warmer and drier in an obvious way. Accordingly, the glaciers and lakes have been retreating. Grassland has been degrading because of over-grazing. As a result, land desertification and soil erosion are increasingly expanding. These will be a threat to the Yangtze River Valley, and to the ecological security of the whole Yangtze River Basin. The alpine meadow is one of major high-altitude cold ecosystems in this region. In the influence of global change, undoubtedly, the alpine meadow dominated by cold resistant Kobresia plant will have to face ecological menace. Therefore, to discuss the impact of global change on the alpine meadow is of high value for understanding global change and reducing its negative influence. The alpine meadow in the source region of the Yangtze River is taken as a study case in this paper. Firstly, the ecological and environmental characters in the source region were clarified. Then the authors employed CENTURY model, a popular biogeochemistry model to simulate alpine meadow ecosystem, in terms of its long-term dynamics in productivity and carbon balance. Grazing, a main human activity in the plateau, was taken into account to simulate probable impacts on the ecosystem as well. In accordance with climate change scenarios from RCMs, possible impacts of climate change on ecosystem were analyzed. Finally, proper adaptation countermeasures were proposed in order to reduce the negative impact of climate change.