Spatial Distribution Of Soil Physical-chemical Characteristics And Erodibility Of Desert Steppe With Different Grazing Intensities

Desert steppe of Sonid Right Banner is located in the easternmost part of Inner Mongolia desert steppe.It is an important part of Inner Mongolia steppe and the production base of animal husbandry.Grazing is one of the most important utilization methods.However,desert steppe in Sunite Right Banner is located in the source of sandstorm.The climate is arid and windy,the soil nutrient content is low,and the system stability is poor.Because of long-term overgrazing,wind erosion and desertification of grassland are serious.In order to explore the spatial distribution characteristics of soil physical and chemical properties and surface soil erodibility under different grazing intensities,the desertification steppe in Sunite Right Banner of Inner Mongolia was selected as the research object.Each group was provided with Light grazing,Moderate grazing,Heavy grazing,and Extreme grazing EG)four grazing intensities and no grazing control group(CK)five plots.The physical and chemical properties of soil and soil erodibility under different grazing intensities were measured by field sampling and laboratory testing,in order to provide scientific basis for rationally determining grazing intensities,enhancing soil erodibility,clarifying the response mechanism of soil corrosiibility K value to grazing intensity,and restoring and improving the ecological production function of desert steppe.The main results are as follows:(1)Light and moderate grazing reduces soil bulk density and was beneficial to soil nutrient accumulation.With the increase of grazing intensity,soil bulk density first decreased and then increased,and the soil bulk density was the lowest under moderate grazing condition.Soil porosity and water content increased firstly and then decreased with the increase of grazing intensity.The porosity was higher in light and moderate grazing plots,soil water content was higher in light grazing plots and lowest in very heavy grazing plots.Soil organic carbon content increased under light and heavy grazing conditions.With the increase of grazing intensity,total nitrogen content in surface soil increased,but total phosphorus content did not change significantly,K value of soil erodibility decreased firstly and then increased.The soil erodibility was the lowest in light grazing plots,and the soil erodibility was the highest in very heavy grazing plots.The variation coefficients of soil erodibility and soil erodibility were lower thanthose of control plots.The grain size composition of soil is mainly sand,followed by silt and clay.The fractal dimension of soil particles was negatively correlated with sand particles,but positively correlated with silt and clay particles(P<0.05).Under moderate grazing conditions,the correlation between soil particles and fractal dimension was the strongest.The soil particles in different grazing intensities showed different trends with the increase of grazing intensities.The soil particle composition in the middle grazing intensities and the very heavy grazing intensities was better than that in the other grazing intensities.(2)The spatial distribution of soil physical and chemical properties showed weak and moderate spatial autocorrelation,which differed among different grazing intensities and groups.The fractal dimension of soil showed an uneven increasing trend from northwest to southeast,and the high value was distributed in group 3,while the low value was concentrated in group 1.The high value of SOC was concentrated on the north-south diagonal and the northeast edge of the test area,while the low value was concentrated on the southwest and northeast grazing plots of the second area.The spatial distribution characteristics of soil total nitrogen were uniform.The low value area was concentrated in area group 1,and the high value area was concentrated in light and moderate grazing plots of area group 2 and area group 3.Soil total P increased firstly and then decreased from northeast to southwest in group 2 and Group 3.There were two high values of soil total P in group 3,and the distribution of total P in three grazing plots in southwest direction was consistent with that in group 2 and 3.In the test area,the low value K value of soil erodibility was mainly distributed in the first area,while the high value K value was concentrated in the grazing plots in the middle of the second and third areas,and the low value K value was dotted in the middle of the high value K value.(3)K value of soil erodibility was significantly negatively correlated with sand content at P<0.05,with organic carbon content at P<0.01,with silt content,with clay content,and with total nitrogen and total phosphorus content(P<0.05).The relation between K value and the volume fraction of silt v1 m and the organic carbon content(C)is as follows: K=0.012+ 0.01V_silt+ 0.005 C.The K value of soil erodibility and Gi of grazing intensity can be expressed by the linear equation K=0.006 Gi +0.021.