Modern oasis evolution analysis based on land-use and land-cover change: A case study in Sangong River Basin on the northern slope of Tianshan Mountains
The evaluation of land- use/land- cover changes (LUCC) in the arid region was scarcely quantified before the 1980s due to the unavailability of satellite data, resulting in our little knowledge of the effects of LUCC on climate change and carbon/water cycle in that period. In this study, we investigated the evolution of oases in Sangong river basin since the 1950s by using seven land cover maps derived from black-and-white aerial photographs (1958, 1968 and 1978), color-infrared aerial photograph (1987), Landsat TM imagery (1998),SPOT (2004) and Landsat OLI images (2014). Results show that: (1) Since 1950,the new oasis consecutively expanded more than four times towards the bottom of the alluvial plain, causing a huge shrinking of the desert landscapes dominated by haloxylon community and tamarix community. Furthermore, agricultural land had the most rapid expansion during the period of 1958- 1968 and built- up areas showed the fastest expansion after the 2000s. (2) Two basic management modes, "local mode" formed by the local governments and "farm management mode" developed by Xinjiang Production and Construction Group, have jointly caused oasis evolution in various LUCC stages. (3) The evolution of modern oasis from the 1950s to 2004 shows the common features of driest oasis area while the period 2004-2014 is characterized by large- scale inter- basin water diversion or some new water sources. (4) The modern oasis expands at the expense of the destruction of desert vegetation, resulting in distinct variation of structure of desert plant community, which will increase the difficulty to protect desert ecosystem.