Relationship Between Soil Type And Gully Morphology In Yuanmou Dry-hot Valley

Soil erosion causes great harm to natural ecology and human living environment.The formation of soil erosion is closely related to soil erosion.The result of soil erosion is the development of erosion gullies of different forms.In Yuanmou dry-hot valley area,the valleys are vertical and horizontal,the surface is fragmented,the number of erosion gullies is large and the scale is large,which poses a serious threat to regional economic and regional ecological security.Therefore,soil erosion is one of the environmental problems that seriously affect human survival and development.Soil properties play an important role in the factors affecting the development of erosion gullies.On the regional scale,clarifying the relationship between soil types and erosion gully morphology will not only help to reveal the mechanism of erosion gully development,but also provide scientific basis for soil and water conservation projects.In this study,Yuanmou dry-hot valley area was taken as an object of study.Based on the methods of soil type map vectorization and visual interpretation of erosion gullies,field soil sample collection and experimental analysis,mathematical statistics,the classification of erosion gullies,extraction of morphological parameters of erosion gullies and gully systems,the basic characteristics of soil types and erosion gullies in the study area were recognized,the relationship between soil types and erosion gully systems was clarified,and the soil properties were revealed.The effect of quality on erosion gully morphology.The main conclusions are as follows:(1)There are 9 soil types,14 subspecies,25 soil genera and 51 soil species in Yuanmou County.In 9 soil types,they are brown soil,yellow brown soil,red soil,dry red soil,purple soil,lime soil,alluvial soil,paddy soil and salt soil.Yuanmou County covers an area of 2022 km ~2,of which 85%is natural soil and 15%is agricultural soil.In Yuanmou dry-hot valley,there are 24271 erosion gully.The length of erosion gully ranges from 100 m to 400 m with an average of 232.52 M.The average density of erosion gully in the whole area is 0.225 km/km ~2.There are 24271 gullies in Yuanmou,but 20309 gullies are formed,807 gully systems.There are six grades of gully system in Yuanmou area,most of which are between 2 and 4 grades.The length of main gully is between 500 and 600 m,accounting for 14.88%.The longer main gully system is mainly distributed in the eroded area.The main branch gully coefficients in Yuanmou area are all between 0.00065 and 0.64,of which the most is between 0.001 and 0.183,with a total of 459.On the whole,the gully system belongs to the semi-main gully type,indicating that the development of the gully system will be very active for a long time in the future.The branching ratio of the gully system in Yuanmou County ranges from 1 to 8,with a large variation range,with an average branching ratio of 3.26;the average length ratio is 2.05 and the average fractal dimension is 1.64,which indicates that the erosion stage in this area is in the middle age,and the value is small,indicating that the gully system in this area is in the middle age,but the time is not long.The morphological characteristics of erosion gully under different soil types in Yuanmou are different,especially under different soil and topographic conditions.The reason is that the development of erosion gully is different due to different soil properties and different topographic slope conditions.Erosion gully and gully systems in Yuanmou area are mostly distributed in Dongshan and Xishan areas.Erosion gully mostly exist in the form of single gully on images.Erosion gully forming gully systems are only a part of them.Longer erosion gully are mostly located in mountainous areas with easily eroded soil types,and denser erosion gully are mostly distributed in Dongshan and Xishan areas of Yuanmou.Although the scale of gully system development varies greatly,the number of most gullies is in an interval,the number of large gullies is small,and the number of gullies varies greatly,but the length of most gullies is small.In Yuanmou Basin,the number of erosion gully is small,the density is small,the length of erosion gully is short,the number of gully systems is small,and the scale of gully systems is small,which is different from that of mountain areas.(2)There are 61 erosion gullies in brown soil area,the total length is 2.24km,the average length is 291.33 m,and the density is 0.183km/km~2.There are 753 erosion gully in yellow brown soil area,the total length is 18.69 km,the average length is248.26m,and the density is 0.145km/km~2.There are 6335 erosion gullies in red soil area,the total length is 141.50km,the average length is 223.37m,and the density is0.36km/km~2.There are 6103erosion gully in dry laterite area,the total length is 124.07km,the average length is 203.29 m,and the density is 0.3 km/km~2.There are 10756erosion gully in purple soil area,the total length is 272.82 km,the average length is253.24 m,and the density is 0.33km/km~2.There are 243 erosion gullies in paddy soil area,the total length is 4.96 km,the average length is 204.03 m,and the density is 0.034km/km~2.There are only two erosion gullies in saline soil,but no obvious gullies are found in limestone and alluvial soil areas.Erosion gully are widely distributed in erodible soil areas,especially in dry red soil,purple soil and red soil areas.Soil area is significantly correlated with the number of erosion gully and the length of erosion gully.In Yuanmou area,dry red soil,purple soil and red soil are the main types,In brown soil area and paddy soil area,the number of erosion gully is less.Because of its small area,the density is not small.There are 9,26,134,323,279 and 36;gully coefficients in brown soil area,yellow brown soil area,red soil area,dry red red soil area,purple soil area,paddy soil area.The length of erosion gully is 2.24,18.69,141.50,124.07,272.82,4.96km;Channel density is 0.183,0.145,0.36,0.3,0.33 and 0.034 m/km~2,respectively.The average main branch gully coefficients were 0.014,0.02,0.02,0.05,0.07 and 0.05,and the average fractal dimensions were 1.31,1.22,1.68,1.41,1.76 and 1.46.The gully grades were mostly below six levels.(3)SPSS was used to analyze the correlation between soil physical and chemical properties and erosion gully morphology.The total potassium in soil nutrients is correlated with the morphological parameters of erosion gully,and the number of erosion gully is significantly correlated with soil nutrients.The more nutrient content,the less erosion gully development degree.After analyzing the soil particle size influence on erosion gully density,the main composition of soil particle size in Yuanmou dry-hot valley is silt and sand grains.The higher the silt content in soil texture,the higher the density of erosion gully.Especially dry laterite and purple soil have higher silt content and larger erosion gully density.Because of its unique physical and chemical properties,the density of red soil reaches its maximum.The morphological parameters of erosion ditches are affected to a certain extent by the physical and chemical properties of soil.Soil nutrients have an effect on the scale of erosion ditches,but have little effect on the morphology of erosion ditches.Purple soil,red soil and dry laterite are characterized by large number and density of erosion ditches and strong development of erosion ditches in three regions under special climatic conditions because of their low nutrient content and high silt content.