| Ecological destruction in Bashang area is one of the main sand sources of sandstorm damage in Beijing-Tianjin area.The area is arid and windy,and the land is severely sandy,affecting the ecosystem balance of the area.Natural factors and human activities affect the structure and function of the ecosystem.And directly affect the ability to provide ecosystem services,which in turn leads to the deterioration of the ecological environment in the dam area,so it is necessary to explore the evolution trend of land desertification and ecosystem services in the area.In this study,the three counties of Zhangbei,Guyuan and Fengning in Bashang were used as research areas,and the quaternary dichotomous model was used to estimate the vegetation coverage based on MODIS-NDVI from 2000 to 2018.The sandification existed frequency method and Sen trend analysis method were used to land.The degree of desertification and its temporal and spatial evolution trends were analyzed,and the land use data was used to analyze and verify the extracted desertified land.On the basis of this,the value of ecosystem service value in the Bashang area was evaluated using the land ecosystem service value estimation model.The relationship between different degrees of desertification and the value of individual ecosystem services was discussed,and the natural and anthropogenic drivers of land desertification were analyzed,and solutions were proposed.The specific results are as follows:(1)Based on the probability of desertification,the degree of desertification is divided into five grades:non-sandification,mild desertification,moderately sandy,severely sandy,and extremely severe desertification.Among them,unsalted and light desertification has the widest distribution range,and unsalted land is mainly distributed in the southwestern part of Fengning County.The moderate and severe desertification is interspersed in the light desertification area,and the extremely severe desertification is scattered.From the current situation of the degree of desertification in 2000 and 2018,the overall ecological status of the Bashang has improved in the past 20 years,with 38.5%of desertified land showing an improvement trend,and only 3.65%of the land showing a deteriorating trend.The overall desertification evolution trend in the Bashang area is dominated by no significant change trend,with a significant decline and weakly significant decline in the total area of 4,759.16 km2,accounting for 26.67%of the monitored area;while the area of significant decline and weakly significant decline only accounted for 0.06%..(2)The value of ecosystem services in the Bashang area is generally "west-low east high".The low-value area is mainly located in the western part of Zhangbei,while the high-value area is mainly located in the Yanshan forest area in the south of Fengning.From 2000 to 2015,the value of 85.92%of regional ecosystem services in the Bashang area increased,the total value of ecosystem services increased by 33.48 billion yuan,and the contribution rate of grassland and forest ecosystem services was over 68%.The regional ecological services are mainly based on regulating services.Among the individual services in the past 15 years,the value of climate regulation services has increased the most,increasing by 9.044 billion yuan.Soil conservation,hydrological regulation,and water supply value have increased first and then decreased.(3)There is a negative correlation between ecosystem services and land desertification.With the intensification of land desertification,gas regulation,climate regulation,and purification of environmental services in regulating services are declining with the degree of desertification,and supply services are generally increased first and then decreased.Trends,maintenance services maintained a slight decline in nutrient cycling,biodiversity services increased first and then decreased,while soil conservation services declined significantly as the degree of desertification increased.(4)The correlation between desertification and ecosystem services and various factors is:average annual precipitation>growing season vegetation coverage>annual average temperature>population>human interference>annual average vegetation coverage>GDP.Precipitation affects the water level in the upper dam area and plays an important role in improving the ecological environment.The vegetation plays a role in water conservation,wind protection and sand fixation.The poor changes in natural conditions such as climate and vegetation conditions are the sandification and ecosystem services in the Bashang area.The main reason for the change in function is that human activities are the inducing factors that affect the desertification of the land and the changes in ecosystem functions.In this study,the temporal and spatial evolution trend of desertification land was extracted and analyzed by sanding frequency method and Sen trend analysis method,and the value of ecosystem service in the Bashang area was evaluated by the equivalent factor method,and the degree of desertification and the individual ecosystem services were analyzed.The relationship between desertification dynamics and regional ecosystem vulnerability and desertification drivers are discussed.This will help to provide a theoretical basis for effective measures to improve the ecosystem services of desertification areas,and also provide a scientific basis for preventing land desertification and achieving regional sustainability in the Bashang area. |
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