Vegetation Cover Change with Climate and Land Use Variation along Main Stream of Tarim River

The RS and GIS technology were used to monitor the spatial and temporal variations of vegetation cover along the main stream of the Tarim River during the period of 1998—2008 based on the Normalized Difference Vegetation Index(NDVI)data of SPOT-VEGETATION with 1 km×1 km spatial resolution.The relationship between vegetation cover change and climate and land use change was analyzed.The results are as follows.The change of vegetation cover experienced two various periods:the vegetation degradation period during 1998—2001,when vegetation cover improved with fluctuations from2002 to 2007;the vegetation restoration period from2002 to 2007,and the NDVI level in 2007 was obviously higher than that at the end of the 21 century.There was a significant difference of the vegetation cover change between oasis and desert grassland.The vegetation cover in oasis agricultural irrigation area and ecological restoration zone improved significantly,but the NDVI of desert forest and grassland decreased severely.The change of vegetation cover was the result of interaction of climate change and land use change.The influence of temperature on vegetation cover change is presented as controlling the rule of annual vegetation growth and prolonging the growth period of vegetation.The increase of annual precipitation was the dominant factor of vegetation cover improvement.Excessive reclamation and overgrazing were the reasons of cultivated land increasing and grassland degradation,respectively.