Experimental Research On Prevention And Control Of Rocky Desertification In The Northern Guangxi Karst Area

Rocky desertification is one of the key concerns and focuses in karst areas.In order to reveal the soil erosion patterns in the red clay karst areas in northern Guangxi,simulation experiments were conducted to simulate the typical red clay bare slopes in the northern Guangxi karst area.The study investigated the runoff and sediment yield patterns under different rainfall intensities and bedrock porosities.Furthermore,reverse slope terraces and Vetiver grass strips were deployed to assess their capabilities in water and soil conservation.The results can provide a scientific basis for soil erosion control and ecological restoration in karst regions.The main conclusions are as follows:1.The results of simulation rainfall experiments on the bare slopes showed that the proportion of surface cumulated runoff modulus to the total runoff modulus ranged from 12.3% to 89.9%,and the proportion of surface cumulated sediment modulus to the total sediment modulus ranged from 84.5% to 99.6%.The soil and water loss pattern of red clay bare slopes in the northern Guangxi karst region is predominantly driven by surface erosion.2.Reverse slope terraces promoted the transfer of surface runoff to underground,simultaneously reducing surface sediment yield and increasing underground sediment yield.Under different rainfall intensities of 15mm/h,30mm/h,and 50mm/h,the average reduction of surface runoff was 71%,52%,and 47%,respectively,and the average increase of underground runoff was 34%,94%,and 45%,respectively.The average reduction of surface sediment yield was 70%,65%,and 54%,respectively,and the average increase of underground sediment yield was 40%,43%,and 60%,respectively.Deploying reverse slope terraces in the northern Guangxi region helps reduce soil and water loss and prevent rocky desertification.3.Stems and roots of Vetiver grass played different roles in regulating surface and underground runoff and sediment yield.The roots blocked bedrock pores and increased the soil void ratio.The stems intercepted rainwater,protected the soil surface from direct raindrop impact,and slowed down the velocity of surface runoff,which reduced the impact of surface runoff on soil,prolonged the residence time of surface runoff on the surface and promoted its infiltration and conversion into the underground runoff.The dense grass stems also helped to distribute runoff evenly on the slopes,transformed rill erosion into weaker sheet erosion,and effectively reduced surface soil loss.The reduction of surface cumulative sediment yield varied from 59% to 95%.4.The effect of Vetiver grass strips varied with different bedrock porosities.Under1% bedrock porosity,the grass strips effectively reduced underground runoff and soil loss,the reduction of underground runoff yield ranged from 70% to 100%,and that of underground sediment yield ranged from 68% to 100%.Under 3% and 5% bedrock porosities,although the grass strips promoted the transfer of surface runoff to the underground,leading to increased underground runoff and sediment yield,the underground cumulative sediment modulus was far lower than surface cumulative sediment modulus.Therefore,planting Vetiver grass strip in the red clay karst area of northern Guangxi can effectively mitigate soil and water loss.