The Study Of The Characteristics Of Soil Erosion Based On ¹³⁷Cs Tracing Technique

Distribution of purple soil in our country is broad which is up to 22 million hm²,and mainly distributed in 16 provinces and autonomous regions,especially Sichuan,Chongqing and Yunnan Province,which reach to 74.56%.Purple soil is rich in capillary porosity and good permeability, high soil fertility and it is our country's precious agricultural soils resources which has been developed in wide range.But the structure of purple soil parent material is loose and easy to efflorescent,anti-erodibility;and also serious soil erosion in the region because of the topography, rainfall and human factors,.In our country,purple soil erosion area and the intensity is only inerior to the loess in the North.Therefore,many scholars in China studied on the purple soil erosion, erosion mechanism and influence factors such as the field and has made great progress.In this paper,I use the ¹³⁷Cs tracer technique to analyse and evaluate parts of the physiognomy and land use types of soil erosion and deposition conditions of small drainage daijiagou.Daijiagou small watershed is located in the Three Gorges reservoir area in Changling town Wanzhou district Chongqing city,and belong to the Wuqiao river watershed tributaries.Base on research of soil erosion in daijigou small watershed,analysis of soil erosion sources,discussion of different parts of the physiognomy and land use types of soil erosion intensity differences it can provide the basis of the Three Gorges reservoir area for small watershed management.The main conclusions of the study as follows:1.Annual average erosion modulus of Daijiagou watershed is 897.37t/km²Â·a,and which belongs to a Micro-erosion degrees areas.The erosion modulus of Uncovered Rock is 9240 t/km2·a and farmland erosion modulus reach to 1056.43t/km2·a,reasonable farming and control Uncovered Rock area is the key problem of Effective control watershed erosion.Erosion characteristics of watershed are closely related with land-use types.Erosion of agricultural land is most serious except the uncovered Rock,There is a significant difference between the erosion characteristics of different parts of the slope in the watershed,as follows:mid-slope>top of slope> base of slope.2.It shows that mountain land use and landscape position of the combined effects the physical and chemical properties of soil base on analysis of small watershed in the soil physical and chemical properties.The distribution pattern of soil nutrients mainly depends on differences land use and Geomorphological sites,and the main reason for intensity the difference is the impact of human activities.Physical properties of different land use types figures out that the Uncovered Rock desertificates most serious,and the physical properties of masson pine forest is better because of less human disturbances, From different parts of the physical properties of topography,the mid-slope is the most serious parts,and the soil on the base is Clayey and strong structural.Forest land has highest soil nutrient of all kinds of land-use types,followed by farmland,Uncovered Rock for next.The chemical nutrients assemble at the foot of the slope according to the study of the soil chemical properties of different parts of the topography,The nutrient content of the foot of the slope is higher than the top of slope and the mid-slope,and the mid-slope is the worst.3.Statistical analysis showed that:the value of the relevant department of soil erosion modulus and 137Cs area activity is-0.43.The modulus of soil erosion and soil physical and chemical properties low or moderate correlate except of total nitrogen and available phosphorus.