| Oasis,as a unique geographic landscape in the arid region of northwestern China,sustains the economic development and stability of arid regions.As the country's policy is tilted westward,human development and utilization of land and water resources in the oasis of the arid region has continued to increase,and the development and evolution of the oasis have shown different levels.The scale of artificial oasis continues to expand,natural oasis is shrinking,and ecological and environmental problems are rapidly highlighted.Strengthening the study of oasis,especially the development and evolution of natural oasis and artificial oasis,is conducive to fundamentally understanding and solving existing ecological and environmental problems.This study uses the Kaidu-kongqi River as the study area.Based on the long-sequence Landsat data,the maximum likelihood method,the normalized vegetation index method,and the decision tree method combining the normalized index,texture,slope,and aspect information are used.To divide the natural oasis and artificial oasis,through the study of changes in oasis patterns,changes in scale,retreats and expansions,shifts in the center of gravity,and driving factors,reveals the spatial-temporal evolution of the oasis in the Kaidu-kongqi River Basin in the past 30years.The main findings are as follows:(1)The division of natural oasis and artificial oasis:Compared with purely using the normalized vegetation index method and simply using the maximum likelihood classification method,the decision tree method based on the combination of normalized index,slope data and texture index is better.The overall accuracy of the classification was increased by 13.7%and 16.7%,respectively,and the Kappa coefficient was increased by 2.71%and 3.94%,respectively.This not only reduced the salt and pepper saltification,but also had a good consistency between the classification results and the actual distribution.(2)Temporal and spatial distribution patterns and changes of natural oasis and artificial oasis:The natural oasis in the Kaidu-kongqi River Basin is mainly distributed in the mountains of Hejing County and the Bayinbulake Grassland.The artificial oasis is mainly distributed in Heshuo County,Qiyan County and Bohu County.,Korla City,Yuli County Economic Belt and the surrounding Corps Plant.From 1995 to 2015,the natural oasis was mainly transformed into artificial oasis and other non-utilizable lands,but the transformation rate gradually decreased;the artificial oasis has shown an increasing trend,mainly from natural oasis and other unused land,and the expansion rate faster and faster.From 1995 to 2015,the area of natural oasis decreased by approximately 3822 km~2,mainly located in the northern of Bayinbulake and lower reaches of the Peacock River and northern mountainous areas;the area of artificial oasis increased by approximately 1127 km~2,and was mainly distributed around counties and cities around Bosten Lake and around Korla.Near Lop Nur in the lower reaches of the Kongqi River.From the perspective of the migration trajectory of the natural oasis and the artificial oasis,the migration direction and amplitude of the gravity center distribution of the natural oasis and artificial oasis in the Kaidu-kongqi River Basin during the past 30 years are quite different.Among them,the migration of the artificial oasis is large and there is migration to the southeast.Trend,the migration trend of natural oasis is not obvious.(3)Drivers of development and changes in natural oasis and artificial oasis:They work together for a variety of drivers.The basic factors that cause change are the natural and climatic environment of the region where it is located,which is reflected by natural factors such as temperature,precipitation,hydrological conditions,and natural disasters.Human activities are the human factors that accelerate this process,including population expansion,Implementation of water conservancy projects,formulation of policies and regulations,methods of land use,etc. |
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