GIS- based studies on patterns of vegetation changes in the northern Ordos Basin

Based on the partition of vegetation in northern Ordos Basin, we carried out a GIS-based analysis of the correlation between vegetation types and groundwater depth using MODIS NDVI data and groundwater level data over the same period to provide groundwater threshold of different vegetation types in northern Ordos Basin. The result shows that low humidity vegetation mainly concentrated in places where groundwater depth is less than 5m. The distribution of low humidity vegetation is very small where groundwater depth is larger than 5m. There are remarkable differences between other types of vegetation and low humidity vegetation in distribution. Groundwater depth in which pixels of zonal-vegetation, like the steppe, desert steppe and steppe desert vegetation,mainly located is larger than 5m, as well as the peak interval of the pixels. Sandy vegetation mainly distributes in areas where groundwater depth ranges in 1m-35m.