关键词: 青藏高原, 干湿状况, 干燥度指数, EVI, 人为干扰

Abstract: As one of the striking characteristics of global change，regional dry-wet climate variations and its effects on ecosystems has become one of the most important environment problems being faced by the world，and has been the focus and the advancing edge of global change study. Qinghai-Tibetan Plateau （QTP） is both a climate change frontier and natural defense of stable climate system of China and around the world. However，impacted by the global warming and anthropogenic activities，the ecological environment problems is showing up gradually，and the ecological shelter zone is seriously threatened. Vegetation is the most important and the most sensitive composition of climate change，and compared to other regions，the action of the vegetation system can have earlier and more obvious indicating effects of global change. The study of regional dry-wet status of the QTP and its relation to the vegetation changes will improve our understanding of the response and adaptation mechanisms of terrestrial ecosystems to climatic change，and also will have very important implications to the implementation of the scheme of ecological shelter zone and contribute to global ecosystem management activities. In this study，the model of RFE 2.0 and Penman-Monteith were used to estimate the precipitation and potential evapotranspiration of the QTP in growth season of the last ten years，respectively. Then based on the aridity index derived from the precipitation and potential evapotranspiration，the temporal and spatial character and the relationship between variations of regional dry-wet climate and vegetation change were explored and discussed. The results showed as follows：（1）Aridity index of QTP increased from SE to NW in general，with 67% of the entire plateau belonging to arid and semiarid regions. Over the ten-year period，about 25% of the area become drier，and obvious difference was detected between the north and the south for the drought trend；（2）The spatial pattern of [EVI] during the growing season were similar to that of drought，showing clearly defined boundaries for the western and eastern. About 25% of the area present obvious vegetation degradation during the last 10 years. （3）The degree of wet-dry has significant influence on the vegetation distribution of QTP，especially in the semi-arid areas which covered 44% of the whole plateau，the correlation coefficient between both was the biggest，the effect of Human disturbance on the vegetation distribution was not very apparent，but there was a relatively weak relationship between aridity index and EVI in the area with intensive human interferences；（4）In terms of the sensitivity of vegetation to the changes of wet-drought，The higher sensibility of EVI to aridity index of 96 meteorological sites during the growing seasons was distributed mainly in northeast and central plateau，and also along the upstream of Brahmaputra River，and as drought conditions worsen，the vegetation of more than 60% of those meteorological sites were degenerated in the nearly 10 years.

Key words: Qinghai-Tibet Plateau； , dry-wet condition； , aridity index； , [EVI]； , human , disturbance