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

Abstract

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.

Numerical Simulations of the Impacts of Mountain on Oasis Effects in Arid Central Asia

“…Atmosphere 2017, 8,212 12 of 20 consistent with circulation patterns, illustrating that the water and heat patterns in the study area are controlled by larger-scale circulation and the climate background in the absence of high-relief terrain. The continuous stripe-like temperature patterns and the oasis cooling effect are further illustrated by the vertical section of temperature patterns from the mod and non-oasis simulations and the temperature differences between the mod and the non-oasis simulations and between the mod and non-mountain simulations (Figure 7).…”

“…The total oasis area has expanded to 4.23 times its original value (from 121.0 × 10 4 ha in 1949 to 512.5 ×10 4 ha in 2010). As a result, a series of ecological problems have appeared due to the limited water and soil conditions [7][8][9], such as desertification and soil salinization [10,11]. These problems have hindered the sustainable development of the oases.…”

Numerical Study of the Interaction between Oasis and Urban Areas within an Arid Mountains-Desert System in Xinjiang, China

“…It lies in the central part of Xinjiang province (China) and is surrounded by two deserts, Gurbantunggut desert in the north and Taklimakan desert in the south, forming several typical mountains-desert systems. The oases in the north slope of Tianshan Mountains were first developed in the groundwater overflow zone and then were extended along the rivers, where water resource was abundant [1,24].…”

“…With the rapid development of the economy and the increase of the population, the anthropization of the oasis area in the north slope of Tianshan Mountains has increased more than four times since the 1950s, resulting in a significant land use and land cover change including an intensive urbanization [23,24]. Our study area includes the oases areas and their surrounding deserts and the mountainous areas in the north slope of Tianshan Mountains (with average height about 4000 m above sea level (asl), highest point Thomuer 7439 m asl and lowest point 154 m below sea level (Figure 1a).…”

“…Moreover, with the development of the population, economy and technology, the oasis area in the north slope of Tianshan Mountains has increased more than 4 times since the 1950s, resulting in a significant land-use and land-cover change and intensive urbanization [23,24]. This intense land use and land cover change has altered the land surface properties, such as albedo, leaf area index and roughness length, resulting in the change of surface energy budget that may affect the oasis-desert breeze and local climate [25].…”