Study On Key Factors Of Soil Erodibility Of Grassland In The Source Area Of The Yangtz And Yellow River In Qinghai Province

Under the background of global warming,soil erosion is becoming more and more serious due to the interference of natural and human factors.Soil erosion directly affects the balance of ecosystem and the sustainable development of social economy in Qinghai Province,where the source areas of the Yangtze River and the Yellow River are ecologically sensitive and fragile.In actual soil erosion,soil erodibility is often used to characterize the impact of soil factors on soil erosion.Based on field investigation and indoor physical and chemical properties analysis,the spatial distribution and variability characteristics of soil factors in grassland and meadow in the source area of rivers and rivers in Qinghai Province were systematically analyzed.The key factors of soil erodibility in grassland and meadow were screened and determined by correlation analysis,principal component analysis,stepwise regression and path analysis.Quantitative study on Soil Erodibility of different underlying surfaces in source areas of rivers and rivers in Hainan Province provides scientific basis.The main conclusions are as follows:?1?Spatial distribution characteristics of various soil factors:With the increase of altitude,the bulk density of grassland and meadow soil increased first and then decreased;the porosity decreases first and then increases,and reaches the maximum at 4800 m and 5000 m,respectively;the water content decreased gradually;the saturated water conductivity of grassland soil increased first and then tended to be flat.The meadow soil decreased first and then increased,reaching the minimum at 4600m altitude,and the goodness of fit with altitude was higher?R²=0.59?.Among the soil nutrient classification factors,the contents of organic matter,total nitrogen and total phosphorus in grassland soil decreased first and then increased,reaching the minimum at 4700m altitude,and the goodness of fitting with altitude was higher?R²=0.62,0.47,0.47?;The contents of organic matter,total nitrogen and total phosphorus in meadow soil decreased gradually.Among the soil particle size factors,the sand grains of grassland soil increased first and then decreased,reaching the maximum at 4800m altitude,sand content in meadow soil increased gradually and tended to stabilize above 5000 m above sea level;Grassland and meadow silt and sand showed opposite trend of change;Both clay and colloidal particles show a U-shaped trend.In the multiracial dimension,the D?q?of grassland and meadow soils showed an inverse"S"type decreasing function with the increase of Q value,indicating that the size distribution of grassland soils was more uniform.Among the soil aggregate factors,MWD,GMD and PAD_>2,PAD_>1,PAD_>0.25,WSA,fractal dimension D and elevation had lower goodness of fit.On the whole,the influence of elevation on soil erodibility was in the order of particle size factor,nutrient classification factor,pore characteristics factor and aggregate factor.?2?Spatial variability of soil factors:Among the pore characteristic factors,the bulk density,porosity and water content of grassland and meadow all belong to moderate variability,saturated hydraulic conductivity of grassland soil is moderately variable?Cv=55%?and that of meadow soil is highly variable?Cv=109%?;Soil nutrient classification factors and grain size classification factors of grassland and meadow belong to moderate variability;Among the aggregate factors,MWD,GMD PAD_>2,PAD_>1 and PAD_>0.25 in grassland and meadow belonged to moderate variability,WSA belongs to weak variability?Cv=5%,9%?and fractal dimension D belongs to weak variability?Cv=5%,7%?.It can be seen that pore characteristics,nutrient classification,particle size and aggregate factors belong to moderate and weak variability in spatial variability.?3?By analyzing the spatial variability of various soil factors in grassland and meadow,18 soil erodibility influencing factors were selected.They are:bulk density,porosity,water content,saturated hydraulic conductivity,sand,silt,clay,colloidal particles,single dimension Dv,information dimension D₁,WSA percentage content,average mass diameter MWD,geometric average diameter GMD,fractal dimension D,structural damage rate PAD_>2,structural damage rate PAD_>1,structural damage rate PAD_>0.25 and organic matter content.In the correlation analysis of soil erodibility influencing factors,grassland soil organic matter has a greater impact on pore characteristics and particle size distribution,while particle size and aggregate factors have a lower correlation.The interaction of pore characteristics,particle size,aggregates and organic matter in meadow soil further indicates that there are some common factors affecting soil erodibility.?4?Because of the strong correlation between soil erodibility factors,the key factors of soil erodibility in grassland and meadow in the source area of rivers were selected by principal component analysis,stepwise regression and path analysis.The key factors of soil erodibility in grassland were:silt,MWD,PAD_>2 and PAD_>0.25,which indicated that soil erodibility was mainly affected by soil particle size and aggregate characteristics,in which particle size distribution was the main factor and aggregate characteristics was the secondary factor;The key factors of meadow soil erodibility are:silt,clay,GMD,PAD_>1,bulk density,organic matter and saturated water conductivity,which indicate that meadow soil erodibility is affected by particle size pore distribution,organic matter,aggregate characteristics and permeability.Particle size pore distribution and organic matter are the main influencing factors,aggregate characteristics are the secondary influencing factors,and permeability is the auxiliary influencing factor.