Analysis Of Solute Migration Rules And Influencing Factors In Lime Soil In Karst Forestland Under Artificial Rainfall Condition

In order to explore the effects of forest land on the soil erosion process and nutrient migration in different hydrological paths in karst areas,this study selected typical karst forest as the research object,took the lime soil under the forest as the test soil,simulated the site conditions of forest land in the laboratory,and adopted artificial simulated rainfall experiment.The characteristics of soil erosion in karst forest soil under different terrain and underground pore（crack）degree were comprehensively investigated.The law of soil solute transport and nutrient transport and the influence degree of influencing factors were analyzed according to the three types of hydrological paths under the forest surface,in the soil and underground.Therefore,through the study of soil solute migration process in karst forest,it is necessary to understand the erosion degree of soil ecosystem in karst region,solve the problems of soil scarcity,vegetation restoration,agricultural production development and so on,and objectively evaluate the ecological stability degree of karst rocky desertification region from the perspective of soil solute.The response of forest land to soil solute transport in karst rocky desertification area is of great significance.The main results are as follows:（1）With the increase of slope,surface runoff intensity and sediment yield gradually increased,subsurface runoff intensity and sediment yield gradually decreased,and mid-soil runoff intensity gradually increased.There is a significant positive correlation between the total runoff yield and the total sediment yield under different gradient gradients.Slope was positively correlated with total nutrient loss in surface runoff,negatively correlated with available nutrient loss in surface runoff,and positively correlated with nutrient loss in underground runoff.（2）With the increase of pore gap,surface runoff intensity and sediment yield gradually decreased,subsurface runoff intensity and sediment yield gradually increased,and mid-soil runoff intensity gradually decreased.There is a significant positive correlation between the total runoff yield and the total sediment yield at surface and underground.The pore gap was negatively correlated with TN,TK and TOC loss in surface runoff,positively correlated with NH⁴⁺-N and NO₃^--N loss in surface runoff,and positively correlated with nutrient loss in underground runoff.（3）With the increase of soil depth,the runoff intensity of subsurface flow in different slopes showed the following pattern:subsurface flow C>subsurface flow A>subsurface flow B.The results showed that the runoff intensity of subsurface flow was C>B>A.Slope had positive correlation with soil nutrient loss,pore gap had negative correlation with soil NH⁴⁺-N and AP loss,and had positive correlation with TN,TK,TP,TOC and NO₃^--N loss.There was a positive correlation between the loss of nutrients in each slope and pore gap gradient.（4）Slope was significantly positively correlated with surface runoff TK,TOC,middle soil TK,underground runoff TN,TK migration（P<0.01）,and significantly negative correlation with surface NH⁴⁺-N migration（P<0.05）.The pore（fissure）gap was significantly positively correlated with the surface TP,NH⁴⁺-N,TP in the soil,underground TP,NO₃^--N,NH⁴⁺-N,ap ap migration（P<0.01）,and was negatively correlated with the surface TN,TOC,TN,TOC,TK in the soil,and the migration of underground TN,TP and TOC.（5）Redundancy analysis and prospective selection analysis showed that with the increase of pore gap,TN,TK,TOC loss decreased gradually,TP,AP,NH⁴⁺-N,NO₃^--N increased gradually,NH⁴⁺-N,AP decreased gradually,TP,TK,TN,NO₃^--N,TOC loss increased gradually.The nutrient loss of underground runoff increases gradually.There was a positive correlation between the nutrients of different pore（crack）degrees.（6）According to the curve estimation of nutrient loss in slope and pore（crack）gradient runoff.According to the parameters of the fitting effect of nutrient loss model is set up for E_i（n）=（α_nS+β_nS²+γ_n）*（δ_nL+ε_nL²+ε_n）.