| Ecological environment is related to the sustainable development of society,economy and nature,and is the core and foundation of human survival and sustainable development.Qaidam Basin is the only plateau basin on the first step among the four major basins in China.Due to the impact of climatic conditions,severe desertification and salinization,the ecological environment is fragile.In the 90s,as the result of excessive exploitation of coal mine,petroleum and trees,the drought in the basin has been further intensified,thus the ecological environment has been deteriorating.Therefore,it is of great significance to evaluate and analyze the ecological environment of Qaidam Basin.Based on the Landsat5 TM remote sensing image data of 1990,2000,2010 and the Landsat8 OLI remote sensing image data of 2018,the image of each period is preprocessed respectively.And the every five indexes,namely,greenness index,humidity index,heat index,salinization index and desertification index,are selected and combined and subjected to principal component analysis to finally obtain the Remote Sensing Ecology Index model(RSEI),which is optimal for the evaluation of the eco-environment quality of Qaidam Basin.With the help of this model,the eco-environmental quality of Qaidam Basin from 1990 to 2018 was analyzed comprehensively,and the landscape pattern of RSEI after grading was analyzed by Fragstats software.The main conclusions of this thesis are as follows:1.The RSEI values four phases of Qaidam Basin by processing the remote sensing images,and the average values were 0.37,0.40,0.38,and 0.43,respectively.The results show that from 1990 to 2018,the overall quality of the ecological environment in Qaidam Basin has shown a trend of decreasing first and then increasing in the past 30 years,and the overall quality of the eco-environment has generally shown a trend of developing in a good direction.2.In order to better understand the ecological environment quality of Qaidam Basin,this study analyzed the RSEI from the patch type level and landscape type level.According to the patch type,the number of"medium"patches in RSEI of Qaidam Basin is the largest,and the overall number of patches is decreasing;the proportion of average patch area of"poor"level is the largest from 1990 to 2018,and the average sub-dimension values in the study area are small,the landscape shape is relatively simple.As for the landscape type,the landscape fragmentation degree of Qaidam Basin is gradually lower,the connectivity between patches is gradually forming,indicating that the overall quality of the eco-environment in Qaidam Basin presents a better trend,which is conducive to the restoration of eco-environment in the study area.3.Taking each city and county as the research unit,and classifying the change range of RSEI index value of each city and county.The results show that in the past30 years,the improvement of the eco-environment quality in Mangya city is the most obvious,with an area of 16604.58 km2,accounting for 35.88%;the second is Golmud city,with an area of 23416.41km2,accounting for 32.9%;Dulan county ranked third,with an area of 14167.27 km~2,accounting for 30.32%,The improvement area is mainly located in the east of Dulan County;The degradation of eco-environment quality is most obvious in Delingha city,Wulan county,Dulan county. |
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