Soil Profile Weathering Feature Research Of Eroded Weathering Granite Slope At Different Sections

Strong soil erosion affects profoundly soil development on slopes.On slopes the same in parent material,but different in erosion intensity,soil varies sharply in weathering development degree and the difference of soil pore.This study in oriented to characterize weathering development of soil profiles at different landform positions of an eroded weathering granite slope.A typical weathering granite slope was selected in Shengzhou,Zhejiang province for monitoring of soil erosion with the help of the Shengzhou Soil and Water Conservation Monitoring Station.On the slope where the station sits,three typical soil profiles(140cm in depth)were selected at sites different in erosion intensity along the slope from top to bottom.Soil profile pore features and weathering intensity as two main discussion indicators,based on stratified samples?undisturbed soil columns?analysis of basic physicochemical properties and chemical total contents in various soil layers,then calculation was done of main chemical weathering coefficients of the soil layers and total weathering intensity of the soil profiles,separately.High-density pore data acquisition of undisturbed soil columns by CT scanning,then we analyzed pore distribution characteristics and influencing factors of the three typical soil profiles in different landform positions.On the basis of above analysis,the correspondence analysis study of soil pore feature and weathering intensity in different sections,different erosion intensity and different depth.The following conclusions were drawn:(1)The soil profile as a whole is not very high in weathering intensity;The variation in weathering intensity between soil layers in the soil profile is very gentle;Chemical stratification of the soil profiles is not distinct,with all the weathering indices forming a boundary layer at about 60cm in depth;the layers above it are obviously affected by water erosion and those below mainly inherit the properties of the residual soil parent material.In terms of weathering intensity,the three soil profiles display an order of bottom profile<middle profile<top profile,which is just the reverse of that in terms of erosion intensity.(2)Weathering degree is significantly and positively related to the contents of organic matter and clay,and also to physical properties of the soil under erosion;However,the influence of organic matter content is greater than that of clay content in the soil in deposition environment.(3)The macro-pore of the three typical soil profiles are the main,the proportion of the pore size betweenl 1mm and 3mm is the largest,but pore size between 5mm and 7mm is the smallest.The sequence of the proportion of macro-pore number of the three typical soil profiles in different landform positions is:the middle>the bottom>the top.The difference between macro-porosity and total porosity is very small in the three typical soil profiles and decreases with the changing of the soil profile depth.The levels of macro-porosity which exceeds the average mainly distributes between Ocm and 30cm.The peak of the average value of micro pore is the top which is 35.18%,then is the middle which is 33.18%,the bottom is the minimum which is 30.64%.The circularity of macro-pore affects the relationship between macro-porosity and total porosity.The more the clay and silt are,the bigger the circularity is.(4)The consistency among total pore,micro pore and weathering intensity is affected by erosion,the severer the erosion,the poorer the consistency,the smaller the erosion,the better the consistency.The variation range of weathering intensity is small in the whole soil profile,the sensitivity for erosion intensity is slow,but the sensitivity of soil pore feature is above weathering intensity.(5)The soil of the profile at the site of severely eroded weathering residual granite slope is on the whole rather slow in soil developing and maturing process,and differs sharply from the typical zonal soil in further development,and severe erosion greatly hinders maturing processes of the soil:and the severer the erosion,the poorer the soil developed.The biggest weathering intensity is not at the surface,but at certain depth under the surface,the layer of the biggest weathering intensity is the biggest influence depth of water erosion.The more soil erosion is,the proportion of macro-pore is in soil profile.