| For a long time,due to the rapid growth of population and the unreasonable use of natural resources and environment in the process of social development,the ecological environment has seriously exceeded its carrying capacity.The ecological environment problems such as land desertification,salinization and soil erosion have become increasingly prominent,and the ecological environment has become increasingly sensitive and fragile,which seriously hinders the healthy and sustainable development of social economy.In recent years,with the vigorous implementation of the five-in-one strategic layout and the continuous improvement of people's awareness of ecological and environmental protection,ecological geology has gradually become the focus of attention.Zhangbei area is an important ecological function core area in the capital of China,and it is also one of the main water sources and ecological barriers in Beijing.This paper takes Ertai Town,Zhangbei County,Zhangjiakou City,Hebei Province as the study area.Through 1: 50 000 ecological geological survey,the distribution status and causes of two major ecological geological problems of sandy desertification and saline-alkali desertification in the study area are basically identified.According to the results of ecological geological survey,the risk assessment of desertification in the study area is carried out.At the same time,suggestions for improvement and restoration of desertification soil in Zhangbei area are put forward.The main conclusions of this study are as follows :(1)In view of the two major ecological geological problems of sandy desertification in the eastern part of the study area and saline-alkali desertification in the western part of the study area,based on the previous work experience,the ecological quality evaluation indexes were screened.Based on the location characteristics of the study area,remote sensing information extraction and GIS spatial analysis were used to extract vegetation cover and terrain slope,rainfall and temperature interpolation calculation.Four evaluation factors,including natural geography,climate environment,soil geochemical properties and habitat quality,were selected as the first-level evaluation indexes,and 12 evaluation factors,including terrain slope,temperature and cultivated land,were selected as the second-level evaluation indexes.The index system of ecological quality evaluation in the study area was constituted together.(2)Considering the limitation of index weight assignment,the combination weighting method combining subjective weighting(analytic hierarchy process)and objective weighting(variation coefficient method)is used to determine the comprehensive weight value of evaluation index.At the same time,the ecological quality of the study area is evaluated by using the comprehensive evaluation method with the help of GIS technology,and finally the desertification risk evaluation results of the study area are obtained.(3)The evaluation results of the study area were graded according to the evaluation criteria.The study area was divided into four grades : low-risk area,medium-risk area,high-risk area and high-risk area.The accuracy of the land desertification risk evaluation results was verified by field investigation.At the same time,the model parameters were corrected and corrected according to the verification results,so as to make it conform to the actual situation of the study area to the maximum extent.(4)Through the analysis of the evaluation results,the high risk areas and high risk areas of land desertification in the study area accounted for 44.71 % of the total area of the study area,that is,nearly half of the land in the study area is facing high risk of desertification.According to the evaluation results,the causes,distribution areas and influencing factors of land desertification in the study area were further analyzed,and the suggestions for ecological protection and restoration in Zhangbei region were put forward. |
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