Ecological Vulnerability Assessment Of Typical Loess Area In Fenhe River Basin

Linfen city is located in the southwest of Shanxi Province,which is a typical loess area.The Fenhe River flows through the center of Linfen City,with a drainage area of 10310 square kilometers.It is the largest river in Linfen City.This study is to study the ecological vulnerability of typical loess areas in Fenhe River basin with Linfen as the main goal,it has reference significance for ecological restoration of Fenhe River Basin.Based on the TM remote sensing image data and environmental data of Linfen City in 2013 and 2017,this paper establishes an index evaluation system based on the "sensitivity pressure" model,selects 11 evaluation indicators,and uses Arc GIS software and spatial principal component analysis method to divide Linfen into five ecological vulnerability levels: slight,mild,moderate,severe and extremely fragile.In the results,we evaluated the ecological vulnerability of Linfen City from the regional and county-level administrative regions,analyzed the temporal and spatial distribution of ecological vulnerability in the study area,and analyzed the main factors affecting the development of ecological vulnerability in Linfen City.The main results are as follows:(1)Construct an ecological vulnerability assessment system for Linfen City: adopt the “sensitivity-stress” assessment framework and select 8 indicators on the level of the sensitive layer: terrain slope,soil erosion intensity,altitude,aspect,land use type,years Average rainfall,soil type and vegetation coverage;select three indicators at the pressure level: population density,GDP per capita,and water resources per capita.Then,the spatial principal component analysis method is used todetermine the contribution rate of each main component.Finally,the vulnerability of Linfen City is comprehensively evaluated on the basis of the calculated environmental vulnerability index value.(2)Systematic evaluation of the ecological environment vulnerability of Linfen City: This paper analyzes the spatial and temporal pattern of the ecological vulnerability of Linfen City from 2013 to 2017.From 2013 to 2017,the ecological vulnerability index changed from 3.26 to 3.12,which is developing in a good trend.In addition,between 2013 and 2017,the degree of ecological vulnerability was slightly and moderately increased by 2.74% and 2.86%,respectively,and mild,severe,and extreme were in a state of decrease,with a decrease of 0.1%,3.03%,and 3.46%,respectively.The 2017 ecological vulnerability ranking results show that the ecological environment of Linfen City is mainly weak and moderately fragile,accounting for 24.98% and 25.70%,respectively,mainly distributed in the western region of Linfen City;among them,severe fragility also has a large proportion,accounting for The ratio is 22.99%,mainly distributed in the eastern part of Linfen City;slightly vulnerable and extremely vulnerable account for a relatively small proportion,10.73% and 15.61%,mainly distributed in the central region of Linfen City.(3)According to the characteristic vector and its contribution rate calculated by spatial principal component analysis,the main driving factors affecting the evolution of ecological vulnerability in Linfen are vegetation coverage,annual rainfall,slope grade and human activities.And Linfen's ecological vulnerability is mainly due to natural conditions,but human activity is the main factor of land disturbance in the later period.