Dynamic change detection of urban vegetation cover using remote sensing -A Case Study in Chengdu

Using ETM + in 2000 and 2007 TM remote sensing image, Normalized Difference Vegetation Index (NDVI) was calculated, then vegetation cover information of two years in Chengdu City was extracted by adjusting threshold values. Analyzed vegetation cover change and spatial variation based on above work. The results show that: (1) from 2000 to 2007, increased vegetation cover has decreased, but the general trend was substantially reduced. Vegetation cover rate from 33.85% in 2000 fell to 10.94% in 2007, 22.91% reduction in total, and average annual reduction was 3.27 %. (2) In terms of the spatial distribution of vegetation, the area without vegetation in two years occurred in urban built-up areas, particularly within the Second Ring Road. The area with vegetation in two years distributed in the region between the Second Ring Road and the Third Ring Road, and three parks areas within the Second Ring Road. The region there was vegetation in 2000 and no vegetation in 2007(that is, the region which vegetation purely reduce) mainly distributed between the Second Ring Road and the Third Ring Road, which mainly caused by the city built-up area expansion from the Second Ring Road to the Third Ring Road. The region there was vegetation in 2007 and no vegetation in 2000(that is, the region which vegetation purely increase) sporadically distributed in the eastern city. There were many industries in the eastern city, and there was no vegetation cover. After implementation of industrial relocation, the area changed into a commercial and residential land, and vegetation cover increased. Urbanization is the main reason for reduction of vegetation cover. The results coincide with the actual situation, which can offer the basis for the government.