| Oasis is survival and development base of the people in arid area. Its changes have been the core research of biogeographic processes and human activities. The size of the oasis affects directly the oasis’ stability and regional economic development. Heihe is the second largest inland river basin in northwest China and it is one of the most promising areas in Hexi Corridor. As the development of socio-economic, the oasis’development and utilization level strengthen. However, shortage of water resources, fragile ecological environment, relatively backward socio-economic development level, urbanization lag and other factors which constrain the use of resources and regional economic development. Accordingly, there is a great practical significance for the suppression of desertification and promoting sustainable development of oases to study the oasis’ spatio-temporal change processes, to grasp accurately the characteristics and laws of the oasis’ development and change, to investigate the driving mechanism, to learn the oasisification and desertification processes in arid areas and its response to human activities and climate change, to develop ecological security strategy.This research selects Linze Oasis which located in the middle of Heihe River Basin in Hexi Corridor as the study area, using a combination of qualitative and quantitative methods, basing the extracted oasis information which used multi-source remote sensing image data in13typical periods from1963to2009, combining the decline and expansion of oasis, oasisification regional differences, and oasis landscape pattern changes, this paper comparatively analyzes the oasis’ spatio-temporal processes from the size and spatial distribution, and it reveals the oasis’dynamic trends. Finally, combining with field surveys, statistics and literature, it discusses the driving forces mechanism of the oasis’spatio-temporal change processes from the natural and human factors. The main results are as follows:1. Linze Oasis mainly distributed in the two sides of Heihe River, Liyuan River, and main canals, it extends to the periphery along rivers and channels. The oasis’scale obviously expand in fluctuate. The oasis’ area increased from350.65km2in1963to586.47km2in2009, and it has increased by67.25%in recent46years. 2. The decline and expansion areas of oasis are overlap. Central alluvial plains and northern desert and oasis ecotone are the interacting intensely area of oasisification and desertification. Throughout all the study period, the process of oasisification is absolutely dominant compared with desertification. Oasis decline mainly occured in the1970s and before, the decline area mainly distribute on the oasis’edge. Oasis massively expanded in the middle of1980s and later, in addition to the oasis’fringe, the expand areas were also within the complex plaques. The way of oasis expansion includes the body internally filled expansion and progressively peripheral extension. Oasis’changes are regional different. It is different at different times and areas. The most intense oasis’change is along with Lanxin Railway oasis, followed by the two sides along the Heihe River, and the third is the south piedmont of Liyuan river valley floor. The oasis’ development change transits from an unstable state to a relatively steady state.3. In the process of the oasis’expansion, it shows a landscape patches spread-expansion-integration and the large patches extended outward. Oasis landscape patches are scattered and broken early, with the expansion of oasis lately, scattered broken patches extended gradually into larger patches. The fragmented landscape patches in the internal oasis change into many neat block structure. Oasis landscape fragmentation degree dropped and its edge tends to structured on the whole which indicates that the impact of human activities on the oasis intensified greatly.4. Oasis changes were affected by natural and human factors. The natural and human factors worked together to form a resultant force to promote the changes of oasis.The natural environment and climate background in arid area which represented by precipitation, air temperature, total amount of water resources and natural disasters et al. are important factors of the oasis change driving force. At the same time, the continuous progress of human society and a variety of the accompanying and gradual strengthening human activities, which represented by the population growth, policy changes, economic development, the progress of agricultural science and technology and its inputs, the constructions of water conservancy infrastructure et al. are the most essential factors of oasis change driving force. The dominant factors which affected oasis changes are distinct in different of periods and area, and they interact with each other between. From1963to1978, the population growth and policy changes are dominant as the leading driving force. From1979to2002, the family-contract responsibility system led the change of the oasis together with the economic development. From2003to2009, the economic benefit has become the dominant factor. However, population growth and the constructions of water conservancy infrastructure are always influenced on the changes of oasis. The specific river distribution patterns and hydrological characteristics in arid region influence and determine the location and scale of oasis. Human activities influence oasis changes through interventing the spatial distribution of water resources. |
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