| Heihe River Basin is one of the most active for research and practice for land planning and sustainable development in China. With the continuous development of oasis in the middle of Heihe River Basin, water conflicts have become more and more serious each day, which has posed a severe test to the development of the oasis in downstream areas of Heihe River, especially with the unreasonable exploitation of artificial oasis in the middle of Heihe River Basin, the function of the oasis ecological barrier has come down day by day in Heihe River basin, and even it has become an important source of dust storms. In order to analysis the driving mechanism for the change of oasis, govern the local ecological environment problem, and prevent and control desertification, the changes of the oasis are researched in the region.In this paper resorting to all sorts of research tools such as remote sensing, GIS, GPS, adopting the research methods of visual interpretation and reconstruction of literature, the oasis in the middle of Heihe River Basin were reconstructed. Firstly, in this study, interpretation of signs or characteristics of surface features of different data types are established or determined through the field investigation, survey visits and refers to gathered relevant information from local libraries, archives and government.; then, the oasis are reconstructed by manually digitized in early liberation,1957,1963,1968,1973,1975 and 1977. Finally, the spatial distributed location, scopes and areas of oasis are determined by computing function and spatial analysis method of GIS, the changes of the oasis are compared during the adjacent years, and causes of changes are briefly analyzed. The Conclusions are as follows:1. Quantitatively, the expansion of oasis is main trend in the middle of Heihe River. Eyes from the the trend of changes, the oasis showed a trend of "two rise and one fall" in the middle of Heihe River basin, with a main trend of rise. The areas of oasis have a trend of decrease from 1957 to 1963, while the areas of oasis have a trend of increase in other periods. Quantitatively, the areas of oasis are 150510.82hm2, which are smaller in Liberation; the areas of oasis have a larger increase in 1957, which are 319497.76 hm2 and average annual growth 18776.33 hm2; and then the areas of oasis decrease in 1963, which are 292835.80 hm2, and average annual growth 4443.66 hm2; and after 1963. the areas of oasis have a trend of increase, but the growth is relatively slow, the area of oasis reach to 353498.10hm2 in 1977.2. From the spatial distribution point of view, the oasis of Heihe River Basin is mainly distributed on both sides of Heihe River, river banks of its cross-strait, around the old trunk, and scopes of oasis have been expanding outward along the river and canal sides. Even during the shrinking oasis, the area of reduced oasis is also cultivated land which was previously developed and abandoned cultivated for some reason, over time, gradually developed and utilized again. From the distribution of each county point of view, the changes of oasis are not fully consistent, the oasis has more dramatic changes in each county, regardless of expansion or shrinks, the changes of oasis are erratic changeableness, and the paths of oasis relatively broken. They are mainly distributed in south of Gaotai county, in the central of Linze county, in northwest and in the central of Ganzhou, in north and the center Minle, in the centerl of Shandan county, and Minhua in Sunan county.3. From the process point of view, the development of oasis has been gradually transited from the state of unstable to the state of stable in the middle of Heihe River basin. From 1949 to 1963, the areas of oasis have a large growth and then large reduction in this region, indicating that the oasis is an unstable state. After 1963, the growth of oasis relatively slow, the change of oasis is also more stable. However, the oasis and desertification are always exist, only the area of oasis is larger than the area of desertification so the overall trend become expansion of oasis, which is the case of the relatively steady total areas of oasis.4. The changes of oasis are largely caused by social factors in the middle of Heihe River basin, but in some stage, natural factors also play a crucial impact. From the Liberation to 1957, with the rapid growth of population, rapid development of productive forces, area of oasis are expanded rapidly. However, from 1958 to 1963, due to the failures of agricultural policy and frequent natural disasters, massive population exodus or die of hunger, population decline significantly, a large number of cultivated land had been abandoned, which made the area of artificial oasis substantially reduced. After 1963, the population is still in the high birth rate, low deathrate and high growth stage, in addition, because of the "food for the center" underthe guidance of the one-sided policy, a large of land were promoted to develop and utilize. After 1966, because of suitable climate, more precipitation, less disastrous weather, so they provide a more favorable condition for expansion of oasis. On the other hand, population under control, but the total population is still increasing, at the time due to the requirements to agricultural policy are carry out farmland capital construction, land reclamation and supporting projects for canal system in field, improvement of water conditions, the land exploitation is steadily developed in this region.
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