Vegetation change during 1990-2000 and its response to climate change in the northern slope of Tianshan Mountains

We have investigated the vegetation change based on the soil-adjusted vegetation index (SAVI) and its response to the climate change in the northern slope of the Tianshan Mountains, Xinjiang, northwest China during 1990-2000. The SAVIs are derived from Landsat TM images between July 1990 to July 2000. 13 types of land cover are determined and their vector data are established based on visual interpretation and TM images by using ARC/Info software. In order to study the vegetation change in detail, we have divided the 13 types of land cover into two categories: (1) the vegetation-land cover (VLC) and (2) the nonvegetation land cover (NVLC) and the study area has been divided into 5 geographical subregions. The SAVI values of the different VLC types in the different subregions are calculated by applying ARC/Info and ERDAS Image software. We have put forward the integrated vegetation index (IVI) based on the SAVI values of the different VLC types and their area composition, and calculated the IVIs in the different subregions. The results show that the IVI significantly increased by 5.76% between 1990 and 2000. There were the different increases in the different geographical sub-regions during the period. These reveal that the vegetation coverage and the biomass increased in 2000, compared with that in 1990, which responded to the annual precipitation increase during 1991-2000.