Evolution Process Of Soil Erosion In Typical Watershed In Sandstone Region And Optimization Of Plantation Pattern

Ecological protection and high-quality development of the Yellow River Basin is an important part of the construction of ecological civilization in the new era of China.The sandstone region area is located in the concentrated source area of the Yellow River coarse sand.The climate is arid,the soil is barren,and multiple types of erosion such as hydraulic,gravity,freezing and thawing occur alternately.This leads to multiple and complex erosion types,soil erosion leads to continuous deterioration of the ecological environment,single vegetation type and relatively simple configuration mode,weak resistance to natural disasters,and the ecological environment is still very fragile.The erosion situation in the watershed is not the same,governance needs and land The usable value is also different.The study on the optimization of the spatial configuration of the plantation system in this area has important practical significance for promoting the ecological and environmental protection of the river basin and the sustainable development of the economy and society.This thesis selects the Geqiugou watershed in the exposed arsenic sandstone area as the study area,and analyzes the characteristics of land use transfer and landscape pattern changes in the small watershed in the past 30 years.On this basis,the revised general soil loss equation is used as the basis for the analysis of the watershed.Estimation of erosion status,analysis of erosion changes,and finding out the problems in the layout of planted forests,using analytic hierarchy process to determine the reasonable proportion of planted forests,judging and selecting the combination of forests and tree species with strong ecological functions,and suggesting the use of erosion control The spatial pattern of soil and water conservation vegetation in small watersheds is mainly controlled,taking into account economic and ecological benefits.The research reached the following conclusions:(1)The main problems of land use in the Geqiugou watershed at this stage.The land use structure is unreasonable and the land use efficiency is not high.The main manifestation is that the cultivated land is widely distributed in the river valley and beach area,but the utilization efficiency is not high,and the output value per unit area is relatively low.Although the forest land is widely distributed,the economic benefit per unit area is low.The bare land is scattered throughout the watershed,making it extremely difficult to manage.The dominant landscape in the Geqiugou watershed is grassland,accounting for 59.46%of the total watershed area,followed by woodland,Accounting for24.43%of the total watershed area,bare land area of 21.11km~2,accounting for9.35%of the watershed area,while the sum of water area and construction land accounted for less than 2.77%of the total watershed area.Between 1990and 2018,land use The change was a decrease of 14.16km~2of arable land,which mainly flowed to woodland and grassland.Woodland increased by34.2km~2,grassland decreased by 12.17km~2,and bare land decreased by8.13km~2.Due to the implementation of large water and soil conservation projects,bare land was transformed into grassland and woodland.(2)The intensity of water erosion in the watershed is mainly determined by rainfall,topography and land use.In the past 30 years,the degree of soil erosion in the Geqiugou watershed has eased,and the erosion intensity of each part is mainly slight erosion.Coverage gradually recovered.By 2018,the area of slight erosion in the watershed accounted for 74.09%.However,the terrain in the watershed was fragmented,ravines were densely covered,and moderate-intensity erosion was scattered and embedded in the large area of slight erosion.It was found through field investigation that,Erosion is mainly concentrated in the middle of the slope and in the channel in the watershed.The soil erosion intensity index under different land use types has been different in the past 30 years.The soil erosion intensity of bare land is the largest,followed by grassland and cultivated land,and soil erosion of woodland.The intensity index is the smallest,and the unreasonable land use method destroys the balance of the ecosystem.(3)By measuring the suitability of artificial vegetation restoration,the ultimate forest coverage rate for future forestry construction in the area is determined to be 47.37%.Based on the erosion prevention and control of the watershed and the economic and ecological needs,the water and soil conservation of the typical small watershed in the arsenic area can be established The forestry configuration mode of vegetation includes steep slope protection forest,ditch edge protection forest,ditch bottom protection forest,gentle slope economic forest and gentle slope grazing forest.The adjustment of the plantation structure of the typical small watershed in the arsenic area still focuses on the prevention and control of soil erosion.Based on the improvement of the ecological environment of the watershed,the goal of vegetation allocation has begun to focus on improving the economic and ecological benefits.The economics after the adjustment of the plantation structure Benefits occupy a position second only to erosion prevention and control.The final plantation forest structure,the structure of forest types are,in order,steep slope protection forest(0.24464),ditch protection forest(0.28697),ditch bottom protection forest(0.21660),gentle slope economic forest(0.14349),gentle slope grazing forest(0.10830).The order of the weight of tree species structure is Caragana korshinskii(0.27945)>Sea buckthorn(0.25461)>Mountain apricot(0.16495)>Pinus tabulaeformis×Seabuckthorn(0.12085)>Pinustabulaeformis×Mountain apricot(0.10615)>Pinus tabulaeformis(0.07399).