Study On The Mechanism Of Grazing On Dust Release And Transmission In Desert Grassland

As the main component of terrestrial ecosystem,desert grassland is a grassland ecosystem combining drought fertility and high sensitivity.Under the dual pressure of soil erosion and grazing.Therefore,it is of great significance to carry out the study of dust release and transfer of different grazing intensity in desertification grassland to clarify the influence of grassland grazing on soil erosion and nutrient composition,as well as the scientific and reasonable formulation of grazing system and grassland protection policies.In this thesis,the research grassland in Inner Mongolia,In the plots for continuous random grazing mild grazing(LG),moderate grazing(MG),heavy grazing(HG),extremely heavy grazing(EG)and non-grazing control(CK),Through 2 years of continuous sampling observation,To study the change of sediment transport rate at vertical height under different grazing intensity and the change of daily average sediment transport flux under different grazing intensity and its relationship with community characteristics;The vertical distribution characteristics of sandstorm flow particle diameter and the particle size distribution of topsoil under different grazing intensity were studied;To study the soil crust particle size and topsoil particle size distribution and nutrient composition under different grazing intensity;Study the soil etchability under different grazing intensity;To study the process of different grazing intensity.The results indicate that:(1)The sediment transport rate showed monotonically decreasing power function with increasing height under different grazing intensity,and the magnitude of sediment transport rate varies significantly between different grazing treatments.EG> HG> MG>LG> CK;When the height was below 40 cm,it decreased rapidly with the increase of height;when the height exceeded 40 cm,the change gradually leveled off.The average daily sand transport flux gradually increased with the increase of grazing intensity,which also showed EG>HG>MG>LG>CK.(2)The relationships between community height,cover and litter biomass and sand transport fluxes were all significantly negative.Among them,87% of the variance of sand transport flux could be explained by the variation of community height,86% of the variance could be explained by the variation of vegetation cover,and 94% of the variance could be explained by the variation of litter biomass.(3)The particle size composition in the sand flow gradually pered with the rising particles,and the content of particles and powder grains showed an upward trend,while the content of sand grains decreased significantly;With the increase of grazing intensity,the soil moisture content increases with the increase of soil depth under the same grazing treatment,and the water content of each soil layer decreases with the increase of grazing intensity.With increasing depth of soil layer,the difference in soil water content between the grazing treatments decreased.The total and fast-acting nutrients in the soil crust showed a trend of first increasing and then decreasing,with the maximum under the LG treatment,in which the total nutrients did not differ significantly among grazing treatments,and the fast-acting nutrients were significantly higher under the CK and LG treatments than other grazing treatments,with the C/N ratio maintaining in the range of 8.31-9.64 and gradually decreasing with the increase of grazing intensity,and the differences among grazing treatments were not significant.The differences between grazing treatments were not significant;the changes of total and fast-acting nutrients and C/N ratio in topsoil were basically the same as those in soil crust,and the C/N ratio was maintained in the range of8.31-10.11.(4)The effect of grazing intensity on soil erodibility was significant,and soil erodibility increased with increasing grazing intensity;soil erodibility was affected by soil grain size composition,organic matter content and surface roughness,of which sand content had the greatest effect on soil erodibility and surface roughness had the least effect on soil erodibility;surface fluvial sand production gradually increased with increasing grazing intensity,and community height,cover and dead fall biomass decreased with increasing grazing intensity.The increase of community height,cover and litter biomass will reduce the surface fluvial sand production.The effect of community vegetation height on surface runoff and sand production was higher than that of community cover,and the effect of litter biomass on surface runoff was higher than that of sand production.