Effects of vegetation indices to the spatial changes of desert environment using EOS/MODIS data: a case study of Sangong inland arid ecosystem

摘要

Sangong waddi basin in the north piedmont of Tianshan Mountains is a typical inland arid ecosystem in China. Desert environment especially land cover and land use in the basin changes dramatically in recent decades under the anthropogenic impacts. In order to develop an approach to highlight the environmental changes, we present a case study in the paper to examine the effects of different vegetation indices to the spatial changes of desert environment in the basin using Moderate-resolution Imaging Spectroradiometer (MODIS) data. First we compute the different vegetation indices including Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) for the basin from MODIS data and then compare their applicability to indicate the seasonal changes and spatial variation of vegetation in the basin. The results show that when the two vegetation index EVI and NDVI were used at the same time in monitoring the desert vegetation situation, Smaller the difference value between their values were, less the human activities interfere. The vegetation gradient variation of the desert vegetation is distinct in the basin. Therefore EVI can be used to highlight vegetation growth over the alluvial fans while NDVI is suitable to monitor vegetation growth in the hilly regions. With this finding, we further develop an approach to examine the desert environment changes in the basin. Based on the examination, several policy recommendations have been proposed in the study for better administration and utilization of arid land resources in the basin.