| The arid areas account for about one third of Earth’s land surface, reaching to 47.74 milion km2, on which 10% of world’s population survive. Nowadays, the people give the top priority to the study of oasification and desertification in the arid areas, which has become one of the most booming fields in the study of international climatic system, global climate change, land deterioration and regional sustainable development around the world.Remote-sensing (RS) technology, as an emerging technological method, gets the widely use in the area of land use monitoring and ecological environment protection,which has so many advantages like large scale observation, short update period, large amounts of information, accurate data of land cover change and limited restriction. Moreover, applied this technique to investigate the oasis evolution can work out the problem that Human beings are unable to determine the boundary of oasis, so it has a lot of potential in this field.Yinchuan Plain’s Oasis is located in the sub-oasis areas of Hetao plain at the Ningxia Hui Autonomous Region. The region has a temperate continental arid climate. It is an important oasis agricultural base in China because of using surface water from the Yellow River for irrigation.With the development of increasingly making use of oasis, the human activity triggers a series of eco-environmental problems across the whole worlds, which have a direct effect on sustainable development of arid areas. Therefore, studying spatial-temporal changes has important significance in protecting and utilization oasis. Aimed to investigate the spatial-temporal changes of oasis, we take Yinchuan Plain as the study area, using land use data and multi-source remote sensing data (high-resolution satellite image in 1973,1975,1989,1995,2006 and 2014), in the support of ENVI, Workstation and GIS. In the study, we have analyzed spatial-temporal changing process of Oasis, characteristics, and divided changing process into some variation patterns. The main contents and conclusions of this paper were as follows:(1) During the past 42 years, Yinchuan Plain’s Oasis area shows a regular expansion trend. At the expansion period from 1973 to 2014, the total figure was 2219.33 km2, with the annual average speed of 52.84 km2/a. The period from 1973 to 1989, the oasis’area extend 1145.46 km2; from 1989 to 1995, extend 412.47 km2, and from 1995 to 2006, extend 296.3 km2, the next 9 years extend 365.1 km2. The Growth rate showed fast-fast-slow-fast feature(2) The changing patterns of Yinchuan Plain’s Oasis area are various among the different places. There was a expansion-expansion-expansion-expansion trend in the Shizuishan City.. Yinchuan urban areas、Yongning County、Lingwu County and Helan County; Pingluo County had a expansion-expansion-expansion-decline trend; and Wuzhong City which is expansion-decline-expansion-expansion.(3)The spatial-temporal shifting distribution of Yinchuan Plain’s Oasis illustrates a movement from west to south during the typical period (1973-2014):the distance of oasis’s centre shifted 3384m to the southwest, along with 189°21’00"s shifting angle. From 1973 to 1989, the centre turned to northwest with the number:2742m and 169°00’20". From 1989 to 1995, the direction changed to the northwest; distance and angle data were 834m,109°02’37"respectively. From 1995 to 2006, the distance shifted 361m to the southwest, and the angle was 255°13’28". After that, at recent 9 years. The shifting distance number was 1538m, and the angle was 259°23’55", which was the maximum of the whole period.(4)The shifting process of Yinchuan Plain’s Oasis from 1973 to 2014 indicates three directions:Yinchuan urban areas, Yongning County and Helan County turn to northwest. Shizuishan City, Pingluo County change to southwest; Wuzhong City and Lingwu County point to southeast(5)Oasts of the driving factors of change, the main factors in Yinchuan plain oasis development for geology and geomorphology, social and economic factors mainly population, GDP, fixed assets investment and traffic line mileage and so on. In addition, the agricultural policy, population policy and ecological protection policies have some effect on the development of oasis. |
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