Response Of Typical Soil Detachment Process To Moisture Content In Mountain And Hilly Areas Of Central And Southern Shandong Province

Soil erosion is one of the most important environmental problems facing mankind.It can cause soil degradation,land productivity decline;and runoff sediment also leases to river plug and carrying pollutants will deteriorate the ecological environment,which bring serious problems to human production and social development.Because of the steep slopes of the mountains,loose soil particles and poor water storage capacity,the hilly area in central-southern Shandong is the most serious area of soil erosion in Shandong Province.Soil detachment is the initial stage of soil erosion process,which provides material preparation for erosion and sediment yield.It has important practical and theoretical significance to accurately simulate the process of its occurrence and development.In this paper,the typical soils in hilly area of central-southern Shandong Province:Cinnamon and Brown soil,were selected to simulate soil detachment by flume scouring test in laboratory.The effects of soil moisture content on soil detachment ability,soil erodibility and critical shear stress were studied.Based on the soil texture,moisture content and dynamic parameters,the simulation equations of soil detachment capacity,soil erodibility and critical shear stress were established,which provides theoretical basis and data support for clarifying the hydrodynamic mechanism of soil detachment process and rational allocation of soil and water conservation measures in hilly areas of central-southern Shandong.The main conclusions of the study are as follows:(1)Under compaction treatment,the bulk density of Cinnamon and Brown soil showed good quadratic polynomial relationship with moisture content,R~2 was 0.94and 0.99,respectively.With the increase of moisture content,soil bulk density decreased first and then increased.The bulk density of Cinnamon soil is between 1.12and 1.31 g/cm~3,while the bulk density ranges from 1.27 to 1.56 g/cm~3 for Brown soil.However,the general linear model(GLM)analysis showed that the change of soil bulk density caused by moisture content had no significant effect on soil detachment ability,soil erodibility and critical shear stress.(2)The detachment ability of Cinnamon and Brown soil had no significant difference under different moisture content,but the change pattern of soil detachment ability was different with moisture content increased.The detachment ability of Cinnamon soil increased first and then decreased;For Brown soil,the detachment decreased with soil moisture content.The difference of soil detachment ability decreased,when soil moisture content was 18%,the detachment ability was almost 0.(3)The difference of soil erodibility between Cinnamon and Brown soil was not significant,and the change pattern of soil erodibility between the two soils was obviously different with moisture content increased.For Cinnamon soil,soil erodibility increased linearly with moisture content increased when moisture content was 3~15%,and soil erodibility of was the highest when moisture content was 15%(0.0682 s/cm),soil erodibility decreased sharply when moisture content was higher than 15%;For Brown soil,with moisture content increased,soil erodibility decreased.When soil moisture content was 3%,soil erodibility was the highest(0.0951 s/cm).(4)The critical shear stress of Cinnamon and Brown soil had no significant difference under different moisture content,but the change trend of critical shear stress was different with moisture content increased.For Cinnamon soil,the critical shear stress was concave with moisture content increased,and when moisture content was 7.86%the value was the smallest(1.1906 Pa).For Brown soil,the critical shear stress was convex when moisture content was 3~15%,and the maximum was 1.6294Pa at the moisture content was 6%.(5)The critical shear stress of Cinnamon soil decreased first and then increased with soil erodibility increased,and the relationship between them was quadratic function(R~2=0.78,p<0.01).For Brown soil,critical shear force increased with the increase of soil erodibility,and the fitting coefficient was R~2=0.94.