Abstract: This study was aimed to study the changes and influencing factors of the Three-River Headwaters Region Index (NDVI). Vegetation type,moderation-resolution imaging Spectroradiometer (MODIS) NDVI products and meteorological data were collected. Trend analysis and partial correlation analysis were performed to analyze the spatial and temporal changes of NDVI in the vegetation coverage area of the Three-River Headwaters Region,and the main factors that caused NDVI changes. The results showed that the NDVI of 38.49% of the study area increased while 1.49% of that significantly decreased. Climate change promoted the increase of NDVI in the study area,in the western area it was mainly caused by the increase of temperature and in the eastern area it is caused by the increased precipitation. In addition,the melting of frozen soil caused by rising temperature caused soil moisture loss in high-slope areas,which in turn reduced the NDVI of water-sensitive vegetation such as meadows.

Key words: Vegetation cover, NDVI, Climate change, Three-River Headwaters Region

摘要： 为研究三江源植被覆盖区归一化植被指数(Normalized difference vegetation index，NDVI)的变化及其影响因素，本研究利用植被类型、中分辨率成像光谱仪(Moderate-resolution imaging spectroradiometer，MODIS) NDVI产品和气象数据等，结合趋势分析和偏相关分析等方法，分析了三江源植被覆盖区2000—2019年NDVI时空变化和引起NDVI变化的主要影响因素。结果表明，三江源植被覆盖区NDVI主要呈增加趋势，明显增加比例为38.49%，局部地区出现减小趋势，明显减小比例为1.49%。气候变化促进研究区NDVI增加，温度升高在研究区西部起主导作用，降水增加在东部地区的作用效果较明显，日照时数对局部地区的影响较大。另外，气温上升引起的冻土消融会造成高坡度地区土壤水分流失，进而导致对水分较敏感的植被如草甸的NDVI减小。

关键词: 植被覆盖区, NDVI, 气候变化, 三江源