| Heihe watershed, a typical arid area with its over-exploitation of water and land resources and intensive human activities in arid and poor natural condition, enduring with long-term farming activity and climate change, has been well known intenationaly on its frequenct and serious environmental problems. Heihe watershed was the hotspot on research of modern geo-ecological processes and human activities in arid area. Oasis area in inland watershed has been changed due to the development of economic and the increasing of population since the founding of new China, especially in Jinta agricultural oasis, a typical oasis of agricultural production in middle part of Heihe watershed. In this paper, Jinta oasis, was selected as a case to study the spatio-tempral change and its driving forces. The result will be very useful for the exploitation of oasis resource and sustainable development in arid area of China.Based on the historical documents and files material, aerial photographs (1963and1968), Landsat MSS images (1973and1977), Landsat TM/ETM+images data (1986,1990,1993,1996,1999,2002,2006,2009), with technology of RS, GIS, GPS and adopting the automatic threshold extraction and human-computer visual interpretation, the Jinta oasis map were reconstructed and the spatial and temporal characteristics were analysised in this paper. Meanwhile, the quantitative analysis of driving forces of oasis change was analysed. The results showed briefly as below:(1)The area of Jinta oasis expanded from1949to2009as the trend of "four rise and three fall". The change of oasis area can be divided into several periods as below. First, the area change of Jinta oasis was constantly increasing in the early period of New China, but decreased in1959-1963. Second, oasis area was constantly increasing from middle of1960s to middle of1970s. In later of1970s, the area decreased slowly. Third, the oasis area increased rapidly in1980s. Fourth, the areas of oasis fluctuated in early and middle of1990s, the area of Jinta oasis was the smallest (316.81km2) in1996year. Fifth. the oasis area increased rapidly after1996and achieved its maximum in2009year (523.17km2)(2) The spatial distribution of Jinta oasis was mainly along the irrigation system around river and canal sides. The change of Jinta oasis was mainly happened as land cover changes in the oasis internal and expansion and shrink in the transitional zone between oasis and desert.Oasis expanded and shrinked repeatedly several times, especially in the change of area of cultivated land. Oasis change degrees were different in the township scale. Oasis of Xiba and Yangjingziwan township changed apparently while Sanhe town only changed a little.(3) Jinta oasis was in an unstable condition in the period from1949to2009, that is, the area of oasis increased or decreased sometimes. Oasis landscape changed as the area increase of cultivated land, forest land, water area and construction land, and the decrease of beaches and unused land obviously from1949to2009. The characteristic of landscape change of Jinta oasis were fragmentation and no rule in common. The inside structure of oasis became more complicated.(4) The analysis of driving forces of oasis change showed that human-dimensional factors were the major causes of the spatio-temporal change of Jinta oasis (the contribution rate is70.49%), the physical driving factor(such as, rainfall, the temperature and disastrous weather) also play a crucial impact (19.41%) in the latest60years. Water resources utilization was the prerequisite condition of oasis expansion, demographic factors and the government policy were the major driving factor acts, and oasis change were co-effected by immigrate, economic development, scientific and technological advance and related factors. |
PDF Full Text Request