Monitoring of Vegetation Cover Dynamic in Xinjiang Based on SPOT-VGT Date from 1998 to 2007

The dynamic of vegetation cover in Xinjiang Wei Autonomous Region was analyzed based on 1 km×1 km SPOT-VGT data from 1998 to 2007.The MVC method,difference value method were used to analyze the annual,seasonal and monthly NDVI changes.The univariate linear regression of one variable was used to simulate the changing trend of the NDVI values.The results show that from 1998 to 2007,the annual maximum NDVI value declineds slightly in Xinjiang.The NDVI values showed an increasing trend in spring while decrease strikingly in autumn.The maximal NDVI value of a year appears in July in Xinjiang.In the last 10 years,the accumulation of monthly NDVI evidently increased in March,April and June;the maximal decrease was in September.The simulating results indicated that there were some regions where vegetation cover was increasing,but the increasing range was smaller than the decreasing range on the whole.The improved regions of vegetation cover mainly were oasis agriculture areas;the degenerated regions mainly appeared in mountain areas.