The vegetation cover over last 20 years in karst region of Guizhou province using AVHRR data

The vegetation cover is a major feature for the ecological system. Its change in large area is mainly caused by climate and human activities. The Karst region possesses quite fragile eco-environment as its peculiar cavern geomorphology. Nowadays, with population increasing, ecological environment is gradually deteriorating. These changes have already seriously affected the development in Karst region. Therefore, it is necessary to study the change of vegetation cover in the Karst region, which will help us understand climate influences and impacts of human activities. In order to understand the change of vegetation cover in the Karst region of Guizhou province, China and its influencing factors, we use the data of AVHRR-NDVI and the information of meteorological stations in this region covering, 1982-1999 to analyze their spatial distribution and temporal change. On the basis of calculating the NDVI mean deviation and Moisture Index (MI) mean deviation, we study the change rates of NDVI and MI mean deviation and the correlation between them. Finally, some conclusions are drawn. Firstly, the humid degree was on decrease in 80's, and is on little increase from 1990, but the vegetation cover is increasing all the while. Secondly, the correlation between NDVI and MI mean deviation demonstrates the humid degree isn't the main influencing factor of vegetation cover. Thirdly, the average speed of vegetation cover increase was 0.26%, which shows the achievement of ecological measurements better in China. The rate of vegetation cover increased in the main ecological preservation is 0.7-2%, while the Vegetation cover in the desert region is decreasing with the speed of 0similar to1.3%, it reflection of the rock-desertification. Then we can make good use of conclusions to guide our actions in the ecological constructions of the Karst region.