Study of the Vegetation Cover Change and Its Driving Factors over Xinjiang during 1998—2007

A time series of SPOT-VEGETATION Normalized Difference Vegetation Index(NDVI) data with 1km 1km spatial resolution were used to monitor the inter-annual and spatial vegetation cover change during the period of 1998 to 2007 in Xinjiang.The vegetation change reasons were analyzed from the points of view of climate change and human activities.Vegetation cover change experienced the following two periods in the recent decade in Xinjiang: a vegetation degradation from 1998 to 2001 and a wavy recovery from 2002 to 2007,as a result,the NDVI was obviously higher than the vegetation cover level at the end of the last century.There were some significant spatial differences of the vegetation cover change.The NDVI of natural forests and grasslands,such as Altay Mountain forest and Bayingbuluke grassland,obviously degenerated,and the vegetation cover change of agriculture irrigation areas and ecological construction areas increased significantly.The NDVI of sandy land and cultivated land had an ascending tendency,but the vegetation cover of forest land and grassland degenerated severely.It is found that the vegetation cover change was caused by both climate change and human activity in Xinjiang.The influence of temperature on NDVI change results in controlling the metrical of annual vegetation growth and prolonging the spring growth period of vegetation.The wavy decrease in annual precipitation is the dominant factor for the two periods of NDVI change.The improvement of agricultural production level is a very important reason to increase the NDVI in the agriculture irrigation areas,and the ecological effect of large scale ecological construction project has presented.