The Relationship between NDVI and Terrain Factors --A Case Study of Chongqing

AbstractNormalized difference vegetation index (NDVI) has been widely used for qualitative and quantitative estimation of vegetation cover and growth activity. Understanding the relationship between NDVI and terrain attributes is of critical importance for protecting environmental and natural resources. A total 36 images of SPOT-VGTS10 with a spatial resolution of 1 km of 2007 were used to investigate the relationship between NDVI and topography in Chongqing. Three terrain attributes, namely, aspect, slope and altitude, were derived from a digital elevation model (DEM). According to its topographical characteristics, Chongqing was classified into four areas, namely, Northeastern Chongqing, Southern Chongqing, Central Chongqing and Western Chongqing. The results showed that topography had strong influence on the distribution and growth of vegetation in the study area. The values of NDVI varied from 0.5 to 0.8 for northeastern Chongqing, from 0.15 to 0.6 for western Chongqing, from 0.5 to 0.65 for central Chongqing, and from 0.4 to 0.8 for southern part of Chongqing. The values of NDVI increased with altitude in the four regions, especially in low altitude areas. The vegetation mostly occupied on 0-25 degree, north-facing and south-facing slopes for northeastern Chongqing, on 0-9 degree, east-facing and west-facing slopes for western Chongqing, on slope of 0-15 degree for central Chongqing, and on 0-20 degree, east-facing and west-facing slopes for southern Chongqing, respectively