Research On The Characteristics And Influencing Factors Of Soil Infiltration Under Typical Vegetation Cover In Loess Hilly Area

Soil and water erosin is the main ecological problem in the Loess Plateau.The vegetation recovery plays an active role in controling soil and water loss and promoting ecological construction in the Loess Plateau.Infiltration is one of the key links of water cycle,which affects the distribution of area precipitation on the surface and underground.To prevent the occurrence of dried soil layer in the process of vegetation recovery in the Loess Plateau,this paper selects the typical vegetation in the Loess Plateau(Leymus chinensis,Artemisia argyi,Periploca sepium),Two types of microhabitats(vegetation and bare land)were selected for each cultivated community based on the characteristics of soil infiltration,and explores the effects of different vegetation types on infiltration on different slope positions were discussed by combining vegetation types with slope positions(at the top of slope,at the middle of the slope,and at the bottom of the slope).At the same time,the status of preferential flow under the cover of typical vegetation was studied.Moreover,it also explores the influencing factors of preferential infiltration depth and infiltration area ratio based on the progressive regression analysis and related analysis from the perspective of soil physical and chemical properties and plant root system.In order to provide some reference for vegetation construction in the Loess Plateau and promote regional sustainable development.The results of this study are as follows.(1)The surface soil bulk density is the smallest,but with the increase of soil depth,the bulk density increases too;The surface laye contains the highest in soil water stable aggregates and soil organic matter content.and with the increase of soil depth,soil water stable aggregates and soil organic matter content decreases.The main parts of soil separate is fine sand,followed by silt and clay.with the increase of Leymus chinensis soil depth,the diameter of root system decreases continuously,while the larger the diameter of root,the smaller the proportion of root characteristic value(root length density,root surface area density)in total root characteristic value.And with the increase of Periploca sepium sample plots depth,the diameter class of the maximum root length density decreases and the diameter class of the maximum root surface area density decrease too.In subsurface and subsurface layers of Artemisia officinalis vegetation,the diameter class increased and the proportion of root length density decreased.In the bare plot of Artemisia armandii,the proportion of root surface area density of each diameter class increased at first and then decreased with the increase of diameter class.(2)when the vegetation is in the middle of slope,the soil stable infiltration rate is higher than that in the upper and lower slope;when the vegetation is in the upper slope,the initial infiltration rate is lowest,while that in the middle and lower slope is relatively higher.When Leymus chinensis is in the middle of the slope,the average infiltration rate is higher than that in the upper slope and lower slope,when Artemisia armandii is in the upper slope,the average infiltration rate is higher than that in the middle and downhill,and when Periploca sepium is in the lower slope,the average infiltration rate is higher than that in the upper slope and middle of the slpoe.Artemisia officinalis had a stronger effect on improving initial and average infiltration rates than Argyrophylla chinensis and Periploca sepium.In the middle and lower slopes,the effect of Leymus chinensis on improving soil stable infiltration rate was stronger than Artemisia argyi and Periploca sepium.The effect of Artemisia officinalis on improving soil stable infiltration rate was stronger than that of Leymus chinensis and Periploca sepium.When vegetation is in the middle of the slope,the effect of improving stable infiltration rate and average infiltration rate of bare land is stronger than that of on-slope and under-slope.When Leymus chinensis,Artemisia sinensis and Periploca sepium were located in the middle of the slope,the average infiltration rate of bare land was significantly increased.when in the upper and lower slope of bare land,only Periploca sepium increased the average infiltration rate s.(3)The Horton formula is the best model for this area because it has the highest fitting accuracy of the infiltration process of the sample plots of this area,and The Cosgakov model is better than Horton's general empirical formula in characterizing the initial infiltration rate in this region.The Horton formula can accurately characterize the variation of stable infiltration rate.And the general empirical formula can effectively characterize the difference between the initial infiltration rate and the stable infiltration rate of Leymus chinensis and Artemisia argyi,and reflect the variation range of infiltration capacity.(4)Vegetation increased the preferential infiltration depth and infiltration area ratiol,among which Periploca sepium had the best effect.Periploca sepium and Leymus chinensis can increase preferential infiltration depth and infiltration area ratio of bare underground soil.And the infiltration area ratio of vegetation sample plots is larger than that of bare plots.Correlation is significant between preferential infiltration depth and infiltration area ratio,and preferential flow develops uniformly in horizontal and vertical.(5)Correlation is significant between soil aggregate,fine sand content and infiltration depth.The infiltration depth of Leymus chinensis sample plot was mainly affected by the content of soil aggregates in subsurface layer;And the main influencing factors of infiltration depth of Artemisia argyi sample plot are the content of surface soil aggregates and fine sand grains;and the infiltration depth of Periploca sepium sample plot was mainly restricted by the content of soil aggregates in surface layer.The influence of physical and chemical properties of surface soil on preferred infiltration area ratio is greater than that of subsurface soil.Root parameters were positively correlated with preferential infiltration depth and infiltration area ratio.The main influencing factors on preferential flow of Aries chinensis and Periploca sepium are roots with diameter of 0<D<0.5mm,while the root with diameter of 0.5<D<1 mm has a larger effect on preferential flow of Artemisia sepium.Surface-level root system plays an important role in the development of preferential flow.