Effects Of Different Grazing Intensity On Soil Physical And Chemical Properties And Runoff Sediment In Typical Grassland Of Xilamuren

Under the influence of human grazing activities and natural factors,vegetation degradation,soil degradation,soil erosion,and soil physical and chemical properties spatial distribution variation of ecological function are easily caused.For the study of typical grassland grazing intensity spatial distribution of soil physical and chemical properties difference and the influence of nutrient loss,this paper takes sheila MuRen grassland as the research object,setting up heavy grazing,moderate grazing,light grazing and no grazing four village,under the condition of grazing in the field control experiment,using field soil survey sampling,runoff plot runoff collecting,indoor test and analysis method of combining the,combining ArcGis software and statistical theory,explore the grazing control test area spatial distribution characteristics and influencing factors of soil physical and chemical properties,clarify grazing experimental zone characteristics of sediment particle distribution,the nutrient content of the response of the grazing intensity,The correlation between the soil surface and the distribution of sediment particles and nutrient characteristics was revealed.The results show that:(1)The Dv value of the surface soil in the test area decreased with the increase of grazing intensity,which resulted in the decrease of the content of clayey powder and the increase of sand in the surface soil.The Dv value gradually increased from the slope up to the slope down,and the variation law of Dv value in the slope up and in the slope was consistent with the general variation law of the test area.Except for the non-grazing plots,the Dv value in the slope down area all showed a gradual increase with the increase of grazing intensity,and the fine sand particle content in the severe and non-grazing plots was significantly higher than that in the moderate and mild plots.Under the dual action of grazing and topography,the clay particles,powder particles and fine sand particles in each grazing plot migrated from the slope to the slope,and the content of sand particles in the soil on the slope increased significantly.Grazing intensity was negatively correlated with the contents of clay and silt in surface soil,positively correlated with sand,and significantly negatively correlated with Dv.(2)Geostatistical analysis showed that grazing activities had an impact on the spatial distribution of soil nutrient contents,and the organic matter,total nitrogen,total potassium and total phosphorus in the test area were well fitted under the linear model,gaussian model and exponential model respectively,and were in the moderate spatial autocorrelation.(3)In the horizontal direction,the nutrients in the test area showed a trend of non-uniform increase from northwest to northeast,southwest and southeast.The nutrient migration on the slope led to the nutrient enrichment in the area under the slope,and the distribution of nutrients in different depths was consistent with that of the test area as a whole.In the vertical section,the organic matter and total nitrogen change rules are consistent,and the content increases first and then decreases in the severe and moderate grazing plots,while the content decreases gradually in the mild and non-grazing plots.Although total phosphorus and total potassium showed some regularity,the variability was small.The contents of different nutrients in surface soil were significantly higher than that in deep soil,and the variation range of deep soil was smaller.The difference of topsoil nutrient was caused by grazing and topographic factors,while the difference of deep soil nutrient was mainly affected by natural factors.(4)With the increase of grazing intensity,the nutrient contents of the four species all showed a decreasing trend.Due to the influence of topography,nutrients were transported from the slope up to the slope down,and the enrichment was found in the soil 0~10cm below the slope,and the most obvious was in the heavily grazed areas.Grazing intensity was negatively correlated with soil organic matter,total nitrogen and total phosphorus,but had little effect on total potassium.(5)With the increase of grazing intensity,the content of fine sand particles,nutrient content and enrichment ratio of runoff sediment in the runoff area gradually increased,and nutrient loss was serious under the situation of short duration and high intensity rainfall.There was a significant or very significant positive correlation between grazing intensity and the viscosity,powder,Dv value,organic matter,total nitrogen and total phosphorus in runoff sediment,and a very significant negative correlation between grazing intensity and sand.(6)With the increase of grazing intensity,the soil quality index of the test area decreased,and the soil quality index of the lightly grazing area and the non-grazing control area was similar.In general,grazing will lead to the loss and decline of soil fine particles and nutrient content,so the appropriate grazing intensity and grazing method should be selected according to the actual situation.