Spatial-temporal variations of NDVI and their relationship with different land use types in Hexi region from 1999 to 2009

Based on the SPOT VEGETATION NDVI data, the spatial-temporal variations of vegetation cover in Hexi region of Gansu province were analyzed by using the MVC (Maximum Value Composites) method and the linear regression analysis during 1999 to 2009, the NDVI change trends and characteristics of different land use types were extracted. According to the results, during the last 11 years, the vegetation cover showed an increasing trend in the overall Hexi region with the rate of 3.70%/10a. The improved area and degraded area account for 24.37% and 3.80% of the total area respectively, vegetation improved region is greater than the degraded region significantly. The vegetation cover has obviously increased in the oasis agriculture region, however, the degraded area of vegetation cover are mainly distributed in the southeastern high altitude mountainous area. Viewed from the land use types, in addition to the NDVI of forest and high coverage grassland have declined, other types have increased.