Evaluation Of Ecological Vulnerability In The Sanggan River

Human survival and development is based on the stability of ecological environment.The study of ecological vulnerability has become the only way to explore environmental change and achieve sustainable development,but up to now,there is no universally accepted evaluation method.Sanggan River Basin is located in the upper reaches of Yongding River,which is one of the water sources of Guanting reservoir.Its ecological environment quality has a crucial impact on the water source safety of Guanting reservoir.It is one of the three channels known as the river channel with more mud and sand and the wind and sand source of Beijing and Tianjin,which is located in the ecological fragile zone of China.In order to provide theoretical support for improving the ecological environment of Sanggan River Basin,the ecological vulnerability assessment of Sanggan River Basin was carried out.This study uses the evaluation model of "pressure state response" and "nature economy society" to construct four benchmark layers of landscape pattern,natural conditions,ecological stress and social economy,selects 16 indicators,and evaluates the ecological vulnerability of Sanggan River Basin by spatial principal component analysis based on Arc GIS software,taking 2007 and 2017 as time series It is expected to explore the characteristics of spatiotemporal evolution of ecological vulnerability,and screen out driving factors by using the comprehensive scores of principal components of each index.According to the results of ecological vulnerability assessment in 2017,combined with the main driving factors of the basin in this year,the study area is divided into three lines of defense for comprehensive management of small watershed,and the regulatory measures are proposed for the characteristics of each division.The main conclusions are as follows:(1)The ecological vulnerability of Sanggan River Basin in the time evolution results in: the ecological vulnerability of the basin has increased in the past 10 years.On the one hand,from 2007 to 2017,the EVSI value of the basin increased from 2.51 to 3.06,that is,from the moderate vulnerability level to the high vulnerability level.On the other hand,in 2007,the basin mainly suffered from moderate erosion and low-grade erosion,accounting for 49.69% and 47.35% respectively,while in 2017,the basin mainly suffered from moderate erosion and high-grade erosion,accounting for 60.08% and 22.81% respectively.(2)The results of spatial evolution of ecological vulnerability in Sanggan River Basin are as follows: in the past 10 years,the development of ecological vulnerability in all directions is relatively balanced,and the distribution of micro vulnerable areas and low vulnerable areas changes greatly.According to the calculation results of the centroid model,the ecological vulnerability centroids of the study area in 2007 and 2017 basically coincide with the central position of the basin,that is,the development of ecological vulnerability in all directions of the basin is relatively balanced.The results of spatial principal component analysis and evaluation show that in 2007,the micro vulnerable area and the low vulnerable area are mainly distributed in the border area of the basin,while in 2017,the micro vulnerable area and the low vulnerable area are greatly reduced,mainly distributed in Guangling County,Lingqiu County,Pinglu District,and Yu County,Hebei Province.(3)The main driving factors of the study area are: natural conditions and ecological stress play a leading role in the ecological vulnerability of the watershed,and the intensity of soil erosion and annual average rainfall have a great impact on the ecological vulnerability.In 2007,the impact of driving factors on ecological vulnerability was as follows: soil erosion intensity > land use type > number of days exceeding gale in the whole year > annual average rainfall > per capita GDP;in 2017,the impact was as follows: soil erosion intensity > land use type > vegetation coverage > annual average rainfall > slope.(4)The study area is divided into nine areas: low fragile ecological governance area,medium fragile ecological governance area,high fragile ecological governance area,low fragile ecological protection area,medium fragile ecological protection area,high fragile ecological protection area,low fragile ecological restoration area,medium fragile ecological restoration area and high fragile ecological restoration area.Among them,the ecological management area focuses on comprehensive management,the ecological protection area focuses on protection and supervision,and the ecological restoration area focuses on protection and natural recovery.