Study On The Temporal And Spatial Changes Of Soil Erosion And Driving Factors In The Middle Reaches Of The Yellow River Basin

With the acceleration of urbanization,while achieving rapid economic growth,it also brings harm to the ecological environment on which people rely for survival.As a key area for high-quality development in the country,the Yellow River Basin currently faces a series of ecological problems such as riverbed siltation and blockage,threats to downstream flood control safety,and soil erosion.The middle section of its watershed is almost entirely located in the Loess Plateau region,making it one of the main ecologically fragile areas in China.Under the interference of human activities and climate environment,the inland vegetation transformation in the watershed is frequent,and the vegetation coverage has also undergone significant changes in spatiotemporal distribution.These factors are closely related to the construction of regional ecological civilization,and need to be taken seriously.A series of ecological improvement measures should be taken to protect the ecological environment of the research area.This article takes the middle section of the Yellow River Basin as the research area,and uses three phases of land use data,vegetation cover data from 2000 to 2020,and DEM data to comprehensively analyze the spatiotemporal distribution characteristics of land use and vegetation cover in the research area from 2000 to 2020 using methods such as land use dynamic degree model and transfer matrix.Based on the modified equivalent factor method of Xie Gaodi and the actual situation of the middle reaches of the Yellow River Basin,the ecosystem service value of the basin was estimated,and the characteristics of changes in ecological service value within the basin were analyzed.On the basis of the aforementioned research,the contribution rate model was used to explore the impact of land use and vegetation cover changes in the middle reaches of the Yellow River Basin on the ecosystem service value,which can be used for scientific evaluation of the ecological environment of the basin,The delineation of ecological functional zones and the calculation of ecological and economic values provide important basis and reference,as well as scientific basis for the rational use of land resources,ecological environment protection,and better utilization of ecosystem service functions in the research area.The results are as follows:(1)From 2000 to 2020,the land type in the middle section of the Yellow River Basin was mainly cultivated land and grassland,and the long-term land use mode of agriculture and animal husbandry was maintained.The evolution pattern of various regions over the past twenty years shows a trend of increasing forest,grassland,and construction land,while decreasing cultivated land,water bodies,and unused land;In terms of land transfer,the main focus is on converting cultivated land into forest land and construction land,as well as converting forest land into grassland and construction land;Under the influence of terrain characteristics,cultivated land and forest grassland are mainly distributed within the altitude range of 1000-1500 meters,cultivated land is mainly concentrated with in the 8～15°slope range,and forest grassland is mainly concentrated within the 15～25°slope range.(2)From 2000 to 2020,the overall vegetation coverage in the study area showed a fluctuating upward trend,with a spatial distribution pattern of high in the southeast and low in the northwest.The overall evolution shows a trend of "increasing slowly increasing",with the increase mainly concentrated between 2000 and 2010.In terms of the impact of land use transformation on vegetation cover,the increase response of types such as "grass to plow","plow to grass","plow to forest","not converted to grass",and "not unchanged" is 0.97 or above,which is the main type of land use transfer that leads to an increase in vegetation cover in the study area.(3)From 2000 to 2020,the value of ecosystem services in the study area showed a trend of first increasing and then decreasing,with an increase in the value of cultural services and support services,and a decrease in the functions of regulatory and supply services.In terms of spatial distribution,the areas with high ecosystem service value mainly include the Qinling Mountains in Shaanxi,the central part of Yan’an City,and the vicinity of Lvliang Mountain in Shanxi.These areas have a large area of forest and grass,and well-developed water systems;The low value is mainly distributed in areas with rapid development of urban construction such as Xi’an,Weinan,and Tianshui.(4)This article quantitatively evaluates the value of ecological assets in the middle reaches of the Yellow River Basin from an economic perspective.It is found that the value of ecological assets in the basin has slightly decreased.In terms of land use,the main factor leading to the loss of ecosystem service value in the study area is the reduction of arable landarea,with a contribution rate of 44.31%.In terms of different types of vegetation coverage,the contribution rates of lower vegetation coverage and middle vegetation coverage to the changes in ecological assets in the basin are 46.95% and 23.21%,respectively,due to large area fluctuations and wide distribution,which are the main driving forces for the decline in ecosystem service value in the study area.