| Oasis,as an biogeographical landscape with natural and human characteristics in arid and semi-arid areas,is the main natural carrier for the survival,activities and development of people in arid areas.With the continuous development of social economy,the oasis in our country has undergone remarkable changes and the scale of oasis is expanding.This paper takes Hotan oasis as the research area.Based on Landsat remote sensing images,to make a study on the scale,pattern and center of gravity transfer of Hotan oasis using normalized vegetation index,pixel dichotomy model and center of gravity transfer model.At the same time,this paper discusses the relationship between oasis development and oasis vegetation cover and urban expansion through the research on Hotan oasis vegetation cover and the scale,pattern and center of gravity migration change of oasis town,and analyzes the influence of oasis vegetation cover and urban expansion on oasis development.The purpose of this paper is to summarize the relevant laws of oasis development by discussing the relationship between oasis development,oasis vegetation coverage and urban expansion,which provides scientific theoretical reference and reasonable suggestions for the ecological security and sustainable development of Hotan oasis in the future.The results showed:(1)The expansion of oasis from 1994 to 2016 was mainly carried out by means of external expansion and internal filling.The area of oasis increased.in 23 years.The increase of cultivated land area is the main contributor to the change of Hotan oasis The reclamation area.of Pishan-Moyu Located in the west of Hotan oasis and the villages and towns in the southeast of the oasis,it is the most obvious area of oasis expansion.At the same time,the expansion of arable land in the middle of the Yulong kashi river and Karakash river is also more obvious.Under the state transfer matrix of different land use types,the transfer of grassland and unused land is the most obvious,both of which show that the transfer is farmland.(2)The high vegetation coverage areas of Hotan oasis are mainly concentrated in the centralpart of the oasis and are distributed in a large area;Middle and low vegetation cover areas are mainly distributed in the periphery of the oasis,with small patch area and high degree of fragmentation.From 1994 to 2016,both the total vegetation coverage area and the high vegetation coverage area of the oasis showed a significant increase trend,and the high vegetation contributed greatly to the increase of the oasis area.In different grades of vegetation cover transfer,bare land and low vegetation cover mainly transfer to medium vegetation cover,while medium vegetation cover and high vegetation cover show a trend of mutual transfer.(3)In the change of urban area,the urban area of Hotan city not only changes greatly,but also has the largest urban area.The urban area of Moyu county and Luopu county also changes greatly,but the change range is smaller than that of Hotan city.During the study period,the urban area of Hotan city,Moyu county and Luopu county all showed an increasing trend,and Hotan city and Moyu county expanded to the vicinity of Yulong kashi river and Karakash river respectively,and Luopu county expanded to the direction of Hotan city.(4)in the relationship of the oasis space-time evolution,the oasis vegetation coverage and urban space and time change,the oasis vegetation changes directly determines the change of the oasis space boundary,the expansion of the core towns on the space and the border of oasis direct contact is not obvious,and the change of the small towns surrounding the oasis has important influence to the change of the oasis boundary.(5)The development of Hotan Oasis should pay more attention to the ecological and environmental benefits while paying attention to social and economic benefits.In the process of continuously promoting oasis and urbanization,we must pay attention to the protection of natural ecological barrier forests and grasslands,ensure the ecological use of natural forests and grasslands,and ensure the long-term,rational,effective and sustainable development of oasis in the future. |
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