Based on the topographic factors NDVI spatial distribution characteristics in Nanchong city, Sichuan province, China

摘要

Vegetation coverage is the main body of terrestrial ecosystem. Detecting the spatial distribution pattern of vegetation will benefit the regional ecological environment protection and soil erosion control. This study, taking the Nanchong city as the research area, MODIS NDVI (resolution 500 m) date and GIS technology were used to obtain spatial distribution features of the different NDVI degree in the case of elevation, slope degree and slope direction via overlap of distribution maps of NDVI and topographic factors maps extracted from digital elevation model. The results showed that (1) the average NDVI value was 0.76, which indicated that the ecological environment was better in Nanchong city. The high vegetation coverage distributed in the eastern region, while the middle vegetation coverage distributed in the western region. Low vegetation coverage distributed in the Jialing River valley, especially in urban area. (2)At the different elevation and slope degree, NDVI mean is rising. In which the largest vegetation coverage area of high, medium and low appeared at 300-500 m in different altitude. And in different slope degree, the distribution of high and middle vegetation coverage area was assumed as single peak, while the distribution of low vegetation coverage area was decreasing. The high vegetation coverage area was larger than middle and low vegetation coverage area above 25 degree. For different slope direction, the low and middle vegetation coverage area was larger in sunny slope, by contrast, while in the shady slope, the situation was just the opposite.