Dynamic changes of vegetation coverage in Manas county based on SPOT-VGT NDVI data

The spatio-temporal changes of vegetation coverage in Manasi county,Xinjiang province and their relationship with monthly temperature and precipitation were studied based on SPOT-VGT Normalized Different Vegetation Index data. The results showed that:( 1) Annual NDVI presented a decreasing trend then steadily increasing trend during 1999-2007,suggesting the total ecological environment was improved in the county in the study period. The average annual NDVI was 0. 17 while the seasonal NDVI fluctuated between 0. 02 and 0. 33.The monthly NDVI maximum NDVI appeared in July and increased largely from March and reached the maximum value in July,then decreased more quickly from July to December.( 2) The spatial distribution of NDVI had high association with water source area,altitude and vegetation form. From the spatial distribution of NDVI,flatlands and desert area showed a relatively high increasing trend than that in mountain area which suggested that Manasi county made progress in greening project,basic farmland protection,farmland shelterbelt construction and protection forest.( 3) Temperature and precipitation were the main factors that affected NDVI. NDVI showed linear relationship with monthly temperature with the coefficient of 0. 0071,while showed exponent correlation with the precipitation with the index of 0. 1203.