Study On Soil Erosion Of The Dianchi-Yizhe Small Watershed Based On Soil Magnetic Characteristics

Soil erosion is an important reason for the deterioration of ecological environment and the decline of land productivity,which has become a major global ecological environment problem hindering the sustainable development of social economy.Therefore,it is very important to control soil erosion and improve land productivity.Yizhe small watershed is located in Dianyuan Town,Panlong District,Kunming City,Yunnan Province.It is the source area of the first-class tributary of Panlong River of Dianchi river system,and also an important agricultural production area of Kunming city.However,the topography of the small watershed is complex,the mountains are high and the slopes are steep,the climate conditions are varied,and there is much rain water.Affected by the unreasonable production activities of local people,soil erosion is easy to occur,which seriously hinders the development of local agricultural production.As an important index of environmental magnetism,soil magnetic susceptibility can effectively evaluate soil erosion,which has been widely used in the field of soil science.In this paper,the Yizhe small watershed is selected as the research area.By using the research methods of field investigation and sampling and indoor experiment and analysis,the slope soil samples under four land use modes in the small watershed are collected systematically.The physical and chemical properties and soil magnetic susceptibility of the slope soil samples are measured,and the profile change characteristics of the soil physical and chemical properties and soil magnetic susceptibility are analyzed.Combined with the physical and chemical properties of the slope soil,the relationship between the soil magnetic susceptibility and the physical and chemical properties of the soil in the small watershed was discussed,and the soil erosion status in the small watershed was revealed through the change of the soil magnetic susceptibility.The main results are as follows:(1)The soil moisture content of different land use patterns in Yizhe small watershed showed the overall change trend of woodland>grassland>arable land>wasteland,while the soil bulk density of different land use patterns was 1.17-1.54g/cm~3,which shows the general change trend of wasteland>forest land>cultivated land>grassland;in terms of soil particle composition,the proportion of sand component is 0.67-4.04%,the average is 1.83%,the proportion of silt component is76.29-82.08%,the average is 79.09%%The clay component accounts for15.52-22.98%,with an average of 19.08%.That is to say,the soil in Yizhe small watershed is mainly composed of silty loam,followed by sandy loam and loam.(2)In Yizhe small watershed,the total nitrogen content of soil under different land use patterns showed the general change trend of arable land>grassland>wasteland>woodland;the total phosphorus content of soil under different land use patterns showed the general change trend of grassland>farmland>woodland>wasteland;the total potassium content of soil under different land use patterns showed the general change trend of grassland>woodland>arable land>wasteland Under different land use patterns,soil organic matter content showed a general change trend of forest land>cultivated land>grassland>wasteland.(3)There is a negative correlation between the low-frequency mass susceptibility and soil bulk density at the level of P<0.01 in Yizhe small watershed,which shows that there is a certain relationship between the low-frequency mass susceptibility and soil bulk density under different land use patterns in Yizhe small watershed,that is,the smaller the soil bulk density is,the greater the low-frequency mass susceptibility of the soil.(4)There is a certain relationship between the low-frequency mass susceptibility of soil and total nitrogen,total phosphorus,total potassium and organic matter of soil under different land use patterns in Yizhe watershed.It also shows that the lower the total nitrogen content,the higher the organic matter content,the total phosphorus content and the total potassium content,the higher the low-frequency mass susceptibility.(5)In Yizhe small watershed,the general trend of low-frequency magnetic susceptibility of soil under different land use patterns is woodland>grassland>arable land>wasteland.It can be seen from this change trend that the low-frequency mass susceptibility of wasteland is the lowest,that is,the soil erosion of wasteland is relatively serious.In addition,the soil magnetic susceptibility of different land-use patterns fluctuates on the spatial scale of the slope from the up slope to the down slope.The general trend is that the soil magnetic susceptibility of the down slope is higher than that of the up slope,indicating that the soil erosion intensity of the slope in Yizhe small watershed fluctuates from the up slope to the down slope along the altitude,and the general trend is the soil erosion intensity of the down slope sedimentary area Degree is less than the erosion intensity of the soil in the erosion area.