Analysis of vegetation coverage change based on NDVIA case study in Ganzhou area, Zhangye city, Gansu

In order to analyze the dynamic change of vegetation coverage in Ganzhou area from 1987 to 2006, TM images of 1987,2006 and 1∶100 000 topographic maps of Zhangye city were used to extract two levels of vegetation coverage maps, the vegetation coverage changes in this region was analyzed quantitatively by means of vegetation index (NDVI) and quantitative remote sensing model on vegetation fraction. The results showed that the total vegetation coverage declined overall the last 19 years, the areas of poor vegetation conditions such as desertification grassland degraded seriously, vegetation coverage of oasis was stable, some areas even increased.