Typical Mound Slope Soil Erosion Spatial Differentiation And Identity Of Influencing Factors In Loess Hilly Region

Mound slope which has round top and steel slope is one of the ubiquitousgeomorphological types in the Loess Plateau Hilly and Gully Region. The special geomorphiccharacteristic has very important significance to the research of the typical mound slope soilerosion spatial differentiation and wind erosion. Both the governance of Loess Plateau andstudy on the law of soil erosion have focused on water erosion region for a long time whilewind erosion research focuses on the strong desertification area, but it is weak that theresearch of mechanism of soil and water loss in wind-water erosion alternating area whichcomplex erosion by wind and water, but also the difficulties and emphases of research inrecent years. In the study, Mound slope located in wind-water erosion interlaced zone ofLoess Hilly Area （Tian Ci Wan Township, Jing Bian County, Shanxi） is regarded as researchobject. Using nuclear tracer technique, According to the¹³⁷Cs content each slope position ofdifferent aspects in a typical mound slope were determined, Analysis the spatial distributioncharacteristics of¹³⁷Cs content and spatial variation characteristics of soil erosion intensity,Further analysis the exchange of aspect and the difference of slope position, combined withcorrelation analysis of the¹³⁷Cs content and soil particle, to study typical mound slope soilerosion spatial differentiation characteristic and influencing factors. Main results andconclusions achieved are presented as follows.（1） Illustrate the aspect differential characteristics of soil erosion about mound slope, andgiving the contribution rate of wind erosion. The area activities of¹³⁷Cs mound slope in alldirections have significantly difference. Variation is from282.27¹009.26Bq/m2. The soilerosion amount in all directions is also significant differences. Here is the average erosionamount: north slope> southwest slope> northeast slope> west slope> northwest slope> southslope> southeast slope> east slope. The erosion intensity is showed as strength erosion, buterosion difference of north and south slope is contrary in loess hilly region other areas, thestudy shows that wind erosion at least should be greater than15%; Mound slope erosiondifference of all aspect different slope position is very obvious, the strongest erosion is in thelower part of slope, and follow is on the middle or top of slope. The erosion rate is fluctuatedaccording to the tendency of slope, and erosion intensity is showed as medium, strength and extremely intensity, mainly strength erosion.（2） Determination and analysis of¹³⁷Cs distribution and erosion rate of different slopeposition in the typical slope. The results showed that¹³⁷Cs activity distribution of soil profilein the different slope position of slope is had law of index decline, but every point of the¹³⁷Csactivity profile distribution have a certain degree of difference, the erosion rate is mainlyperformance for extremely intensity while someplace even reach to extremely intensity, soilerosion rate: middle slope>lower slope>upper slope.（3） Study on correlation of¹³⁷Cs content and soil profile composition in mound slope.Through analysis of soil profile composition, found the difference is not obvious which provethere is no obvious selectivity in the process of soil erosion and migration. Maximum coarsenon the top of the mound slope is4.44, the coarsening of soil texture of northwest slope andnorth slope with different slope position are large than3.85, which are stronger than the otherslopes in different directions. According to the analysis the composition of soil particles in thesurface of typical mound Slope, it is known that the erosion in upper of slope is stronger, andit is obvious that the coarsening phenomenon of surface soil in typical mound slope. In the20cm in soil layer, it is show negative relationship between the content of173Cs and the clay,silt, but the content of fine sand has direct ratio relation with the changes of content of173Csin soil, with no obvious relationship with rough sand. From the quantitative relationshipanalysis, in0¹0cm soil layer, There is a significant negative correlation between the contentof173Cs and clay in soil; in10²0cm, there is a significant negative correlation between thecontent of173Cs and silt in soil. Through stepwise regression analysis indicated that themathematical models between¹³⁷Cs content and clay from0¹0cm is: y=1636.194-91.929x1mathematical models between¹³⁷Cs content and silt from10²0cm is: y=2182.466-33.22x2.（4） Discussed preliminary soil erosion impact factors of the Loess Plateau mound slope.According to the analysis the meteorological factors showed that the wind directions havegreat effect on the soil erosion in middle and upper mound slope, the rainfall has verysignificantly influence to the soil erosion in bottom. Intensity of soil erosion and rainfall havepositive correlation in bottom; the wind directions is the main factor in the middle of northernslope; the rate of soil erosion in bottom of mound slope and wind direction have negativerelationship; hydraulic erosion is the mail impact in bottom of northern slope. From analysisfactors of topography and geomorphology known that slope directions have more impact onthe soil erosion intensity spatial distribution in the top and bottom while it is weak in middleof mound slope. It is a significantly positive correlation between soil erosion intensity andCos, the soil erosion in north slope is stronger than south slope, wind erosion is have moreimpact in north slope than south slopes; it is negative relationship between soil erosion intensity and Sin. The erosion intensity in east slope is weaker than in west slope. Theproportion of clay in soil particles is one of the dominant factors in soil erosion.