Study On Physical And Chemical Properties And Erodibility Of Soil Under Different Land Use Patterns In Beng River Basin

With the population growth and economic and social development,the scope and intensity of land use by human beings are continuously expanding and deepening,and the impact of mankind on the edatope is becoming increasingly profound.Artificial disturbance and destruction far exceed the self-regulation ability of soil,making the current situation of soil erosion and land degradation in all parts of the world very severe.Studying the physical and chemical properties and erodibility of soil under different land use modes is of great significance to the rational utilization of regional land resources and the protection of ecological environment.As the first tributary of Yi River system,the terrain within Beng River basin is broken,with densely distributed ravines,loose and shallow soil layer,dense population,frequent land use activities and serious soil erosion.The research on soil properties and soil erodibility in Beng River Basin is of great significance to the optimization of land use structure,the maintenance of soil quality and the comprehensive control of soil erosion in the basin.Taking the Beng River Basin as an example,this paper studies the characteristics and differences of physical and chemical factors such as soil water content,bulk density,mechanical composition,aggregate,porosity,pH value,organic matter under different soil types and land use patterns,analyzes the correlation between soil physical and chemical properties,explores the applicability of the soil erodibility estimation model for EPIC,Shirazi and Torri in Beng River Basin,analyzes the spatial differentiation characteristics of soil erodibility,and discusses the relationship between soil erodibility and soil physical and chemical properties.The main conclusions are as follows:(1)The physical and chemical properties of 0-20 cm soil of different soil types are different to some extent.The soil water content,> 0.25 mm water-stable aggregate content,GMD and organic matter content all show the trend of cinnamon soil > brown soil > coarse bone soil;the bulk density of soil is brown soil > coarse bone soil > cinnamon soil;all the three types of soils are mainly silt,and coarse bone soil and brown soil are coarser than cinnamon soil;MWD is brown soil > cinnamon soil > coarse bone soil;and the porosity and pH value are cinnamon soil > coarse bone soil > brown soil.(2)Soil physical and chemical properties have certain differences under different land use patterns.The differences of soil physical and chemical properties of different land use patterns in 0-20 cm soil layer are as follows: the water content from large to small is cultivated land,grassland,woodland and garden plot;the bulk density from large to small is garden plot,cultivated land,grassland and woodland.The mechanical composition of the four soils for land use is mainly silt,the sand content in garden plot is significantly higher than that in other land uses,but its clay content is obviously lower than that in cultivated land and woodland;the GMD,MWD and > 0.25 mm water-stable aggregate content from more to less is woodland,grassland,garden plot,cultivated land;porosity and organic matter both show the trend of woodland > grassland > cultivated land > garden plot;and the pH value from high to low is grassland,woodland,cultivated land and garden plot,and the whole soil is neutral and weakly acidic.In terms of vertical change,there is a small fluctuation change of the soil texture,which is mainly manifested by the decreasing sand particles and increasing silt clay particles.Except that the water content and pH value of grassland decrease with the increase of soil depth,the water content,bulk density and pH value of each land use soil rise with the increase of soil depth.The content of > 0.25 mm water-stable aggregates,MWD,GMD,porosity and organic matter of all land use types drop with the increase of soil depth.The content of > 0.25 mm water-stable aggregates in cultivated land reaches the highest value at 10-20 cm,while the MWD and GMD in woodland fluctuate to a certain extent at 20-30 cm soil layer.(3)There is a strong internal relationship between soil physical and chemical properties.Bulk density and sand content have negative effects on various soil properties,while clay,organic matter,porosity,> 0.25 mm water-stable aggregate content,MWD and GMD have promoting and improving effects on various soil properties.(4)The estimated values of the three soil erodibility models are smaller than the measured data of runoff plots.Uncertainty analysis shows that the modified EPIC model is more suitable for estimating the soil erodibility K value in Beng River Basin.The soil erodibility K value of 0-20 cm soil layer is cinnamon soil > brown soil > coarse bone soil;the K value of 0-20 cm soil layer from large to small is cultivated land,garden plot,grassland and woodland;in terms of vertical changes,except for certain fluctuations in woodland,the soil erodibility of each land use rises with the increase of soil depth.Semi-variance analysis reveals that spherical model is more suitable for model expression,and Kriging interpolation method is adopted to obtain the spatial distribution of watershed erodibility K value.Thus,it can be seen that the soil erodibility K value in Beng River Basin is high in the middle and southwest,and low in the northwest and southeast.(5)The relationship between soil erodibility K value and soil physical and chemical properties is different under different land use patterns.The K values of the four land use patterns are significantly positively correlated with silt and negatively correlated with sand particles and organic matter.The K value of cultivated land is also related to bulk density,> 0.25 mm water-stable aggregate content,MWD,GMD and porosity,while the K value of garden land is affected by > 0.25 mm water-stable aggregate content and GMD.Multiple regression analysis shows that soil mechanical composition and organic matter content are the most important factors affecting soil erodibility.The soil grain grades that affect soil erodibility under different land use patterns are different,but they are all affected by the content of soil organic matter.