Effects Of Grazing Intensity On Soil Infiltration And Runoff Sediment Production In Xilamuren Grassland

Xilamuren grassland belongs to the mixed erosion area of feng shui,and the soil erosion is severe.Studying the soil infiltration process and the dynamic characteristics of slope water erosion with different grazing intensities has important guiding significance for analyzing the soil infiltration characteristics,the mechanism of slope runoff and sediment production,and the establishment of prediction models in this area.In order to explore the characteristics of soil infiltration and runoff hydrological process under different grazing intensities,the hydrodynamic parameters and their relationship with the characteristics of runoff erosion were analyzed.In this experiment,four grazing intensity plots were set up in Sumueheiwusu Gacha,Xilamuren Town as research objects,namely light grazing plot(LG,0.15sheep/(hm~2·month)),moderate grazing plot(MG,0.30 sheep/(hm~2·month)),heavy grazing plot(HG,0.45 sheep/(hm~2·month))and no grazing plot(CK,0 sheep/(hm~2·month)).To study the changes of soil infiltration,runoff process and hydrodynamic parameters under different grazing intensities in Xilamuren typical steppe area.Research indicates:(1)Soil infiltration capacity is disturbed by grazing activities.With the increase of grazing intensity,the initial rate of soil infiltration and the rate of stable infiltration decrease,and the duration of reaching stable infiltration is shortened.Light grazing can enhance the performance of soil infiltration.The initial infiltration rate(5.12 mm/min),stable infiltration rate(1.93 mm/min),and 2 h cumulative infiltration volume(213.42 mm)of LG were all good,and the period from rapid infiltration to stable infiltration was prolonged.Under different grazing intensities,grazing intensity was significantly negatively correlated with soil initial infiltration rate,soil stable infiltration rate,and soil cumulative infiltration.Vegetation coverage,sand volume percentage and soil porosity were all positively correlated with soil infiltration rate,while soil bulk density was the opposite.Soil bulk density,soil total porosity and soil capillary porosity significantly affected the changes of soil infiltration rate and soil cumulative infiltration.Moderate grazing can improve soil characteristic parameters and vegetation growth,and improve soil infiltration performance.Through the analysis of soil infiltration model,Horton model has the best fitting effect on soil infiltration rate and soil cumulative infiltration.(2)With the increase of scouring intensity,the overall runoff time sequence is LG>CK>MG>HG.Under different grazing intensities,the overall flow and sediment reduction benefits were LG>CK>MG>HG,and the scour intensity had a positive exponential relationship with the runoff rate.The soil denudation rate of each grazing intensity showed an increasing trend with the increase of the scour intensity.The relationship between the LG soil denudation rate and the scour intensity conformed to the exponential function change,and the CK,MG and HG conformed to the power function change respectively.The fitting equations of grazing intensity(G)and scouring intensity(Q)to runoff rate(RR)and soil erosion rate(Dr)respectively are RR=0.048G+1.045^Q-1.27,Dr=0.001G+1.001^Q-1.005.(3)There is a significant positive correlation between the scouring intensity and the water flow shear force,water flow power and Reynolds number.Under different grazing intensities,the overall mean value of each hydraulic parameter was HG>MG>CK>LG,and the water flow state was in a laminar flow state.LG has a significant weakening effect on water flow shear force,water flow power and Reynolds number to a certain degree of scouring,and the weakening effect on water flow shear force decreases at 20 L/min.(4)Under different grazing intensities,the water flow shear force,water flow power,and Reynolds number had a very significant positive correlation with the runoff rate and soil erosion rate.The order of fitting degree was water flow power>Reynolds number>water flow shear force.The fitting formula of runoff rate and hydraulic parameters conforms to a linear function(y=kx+b).When the soil erosion rate is fitted with the shear force of water flow and the Reynolds number as fitting parameters,the fitting equations conform to the power function(y=ax^b+c).The fitting equation of soil erosion rate and water flow power is shown as follows:CK and LG conform to a power function(y=ax^b+c),and MG and HG conform to a logarithmic function(y=aln(x)+b).(5)After analysis,the water flow shear force,water flow power and Reynolds number are all suitable as the three fitting parameters of the prediction model,and the soil erosion prediction models of CK,LG,MG and HG are respectively Dr=7.505?^-0.612?^2.5750.989^Re,Dr=?^1.68?^-0.434ln(1.264Re+0.991),Dr=0.035?^0.535?^0.3970.995^Re,Dr=1.563?^-0.582?^1.9050.993^Re.