An analysis of oasis evolution based on land use and land cover change: A case study in the Sangong River Basin on the northern slope of the Tianshan Mountains

This study investigated oasis evolution and the changes of peripheral desert in the Sangong River Basin since the 1950s by rebuilding seven land cover maps derived from black-and-white aerial photographs (1958, 1968, and 1978), a color-infrared aerial photograph (1987), Landsat Thematic Mapper (TM) imagery (1998), Satellite Pour l'Observation de la Terre (SPOT) imagery (2004), and Landsat Operational Land Imager (OLI) imagery (2014). The results showed that: (1) Since 1950, the oasis consecutively expanded more than four times from an alluvial fan to an alluvial plain, causing the shrinkage of desert landscapes that were dominated by a Haloxylon ammodendron Bunge community (HBC) and a Tamarix chinensis Lour community (TLC). Furthermore, the primary (1958-1968) and final (2004-2014) stages were the most important periods, during which agricultural land experienced the most rapid expansion during the period 1958-1968, and the built-up area showed the most rapid expansion after the 2000s. (2) Two basic management modes, a local mode formed by the local governments and a farm management mode developed by Xinjiang Production and Construction Corps, together promoted oasis evolution under various land-use and landcover (LULC) stages. (3) The evolution of the modern oasis during the 1950s-2004 showed the general features of an arid oasis, while during the period of 2004-2014 it was characterized by a large-scale inter-basin water diversion or the import of new water sources. (4) The oasis expanded at the expense of desert vegetation, resulting in distinct variation in the structure of the desert plant community, which will make it more difficult to protect the desert ecosystem.