【英文摘要】Under climate change, the patiotemporal shifts in the extent and distribution of alpine ecosystems in source region of the Yangtze and Yellow Rivers of Qinghai-Tibet plateau were investigated. The cause mechanism of alpine ecosystems variation and the influences of the grassland coverage changes on water cycle and hydrological processes were studied. The results shown that the alpine ecosystems have continually degraded in recent 45 years under climate warming. The greatest wetland degradation occurred in the headwaters region of Yangtze River, where wetland areas shrank by 29%, and the area of dried-up lakes rose by 17.5%. While, the high-cover areas of alpine meadow in the headwaters region of Yellow River shrank by 23.2％.The vegetation cover and biomass of the alpine cold meadow exhibit a significant relationship with the increase in the thickness of active layer, and the changes of alpine meadow and wetland areas have a significant relation to climate warming. The climate changes and permafrost environment variation are the most important and direct factors leading to the changes of alpine-cold ecosystem in the region.An ecosystem-biomass model was developed, employing empirical spatial-distribution models of the study region's precipitation, air temperature and soil temperature. This model was then successfully used to simulate the spatio-temporal variations in annual alpine ecosystem biomass production under climate change. For a 0.44 C decade-1 rise in air temperature, the model predicted biomass of alpine meadow and alpine steppe to decrease by 6.3% and 6.7%, respectively, if precipitation remained constant.Changes in vegetative cover of the alpine frost meadow affected soil moisture and its distribution, as well as the relationship between soil water and soil temperature. The changes of the coupling relationship between soil water and temperature and the soil water distribution were the main factors to cause the rainfall-runoff pattern and the FDC changes in a river basin scale.