Abstract: Hydrological conditions affect the development of riparian ecosystems in sensitive watershed.The water-conveyance embankment project constrains overflow in the middle reaches of the Tarim River in flood season and improves the water conveyance efficiency downstream.However,the project also brings about some ecological problems.In this paper,the natural vegetation along the middle reaches of the Tarim River was regarded as the research object,and the changes of normalized differential vegetation index (NDVI) and land use in 2000 (before the project) and 2010 and 2014 (after the project) were comparatively analyzed using the remote sensing and GIS means.The results showed that the NDVI of natural vegetation decreased with the increase of the distance away from the embankment.The NDVI value in a 2 km wide zone away from the embankment in 2000 was holistically higher than that in 2010 except that in a 600-800 m wide zone; in a 20 km wide zone away from the embankment,the NDVI value around a 10 km wide zone in 2000 was higher than that in 2010,on the contrary,it in a zone further than 10 km away from the embankment in 2010 was higher than that in 2000 due to the increase of human activities and the decrease of the effect of natural factors on vegetation.Viewing from the land use change,the area of cultivated land in the study area in 2014 was about 9 times of that in 2000,the vegetation area was reduced by 11.22%,and some natural forest land was transformed into farmland.

Key words: GIS buffer analysis, NDVI, remote sensing, land use classification, spatiotemporal variation, Tarim River