|其他摘要||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 region of northern slope of the Tianshan Mountains is an important oasis in whole arid area, in the meantime, the development of this region affects directly the oasis’ stability and regional economic development, it is also the most promising areas in XinJiang. In recent decades, the growth of population and the development of economy and the exploitation of resources and the development of agriculture in northern slope of the Tianshan Mountains promote the expansion of oasis in this region, however, it cause a series of ecological and environmental problems. Therefore, there is a great practical significance for the suppression of desertification and promoting sustainable development of oases to study the oasis’ development and change, to investigate the driving mechanism, to learn the oasification and desertification processes in arid area and its response to human activities and climate change, to develop ecological security strategy.
This research uses a combination of qualitative and quantitative methods, basing the extracted oasis information which used multi-source remote sensing image data in 6 typical periods from 1960 to 2010, combining the decline and expansion of oasis, oasification regional differences, and oasis landscape pattern changes, this paper comparatively analyzes the oasis’ spatial-temporal processes from the size and spatial distribution, and it reveals the oasis’ dynamic trends. Finally, combining with field surveys, statistics and literature, it discussed the driving forces mechanism of the oasis’ spatial-temporal change processes from the natural and human factors. The main results are as follows:
1、0ver the past 50 years, oasis simultaneous expansion and retreat. The oasis’ scale obviously expand in northern slope of the Tianshan Mountains. The oasis’ area increased from 42416.38 km² in 1960 to 116692.75km²,among these increased, the area of natural oasis had an increase of 74276.37 km²and artificial oasis had an increase of 23857.25 km². Natural oasis’ area had increased by 200.01%, and artificial oasis’ area had increased by 176.59%. The area of natural had a larger increase, however, the growth rate of natural oasis is larger than natural oasis.
2、The decline and expansion areas of oasis are overlap. Throughout all the study period, the process of oasification is absolutely dominant compared with desertification. The period before 2000 is the fastest-ever period of oasis expansion, after 2000, the pace of expansion of the oasis slowed down significantly. The expansion of grassland is the dominant process among the expansion of natural oasis. Grassland expansion mainly concentrated in the southern Yili, Urumqi and Changji, in addition to the expansion of woodland distributed in the northern district of Urumqi , Tacheng and Changji states. The expansion of cultivated farmland is the main expansion process to artificial oasis. The expansion of farmland mainly distributed in the Bozhou, Tacheng, and the center of Changji. The distribution of expanded urban construction land is same as the expansion of farmland, however, the retreat area of oasis presented a relatively scattered distribution in the study area.
3、In the process of the oasis’ expansion, all regions have different relative change rate compared with the whole region, in addition to, all regions also have different dynamic degree.
The relative change rate of oasis in eastern Tianshan Mountains is higher than other regions before 1980, but the regions owning higher relative change rate of oasis transferred to the western region from the eastern regions after 1980. The expansion of natural oasis and artificial oasis have big difference with the whole oasis. The dynamic degrees of natural oasis in Wujiaqu, Changji, Karamay are higher than other regions before 2000, however, all regions’ dynamic degrees have almost no difference after 2000.The expansion of artificial oasis is more complicated than the expansion of natural oasis. All regions’ dynamic degrees present a fluctuating trend throughout the process of the oasis’ expansion.
4、0asis are affected by natural and human factors. The natural environment and climate background in arid area which represented by precipitation, air temperature , total amount of water resources and sunshine hours 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 agriculture science and technology and its inputs 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. Throughout the process of expansion, air temperature is more dominant than evaporation as the leading driving force among these natural factors, considering that evaporation is far larger than precipitation. Population and economic factors play the important role in the process of expansion among these human factors, such as population growth, GDP, the progress of agriculture science and technology and its inputs.|