Effect Of Plant Roots On Soil Prefrential Flow In The Hilly Region Of Red Soil

Soil preferential flow not only plays an important role in water resource conservation of forest,but also has a certain negative impact on groundwater pollution,landslides and mudslides,It is getting more and more attention from all walks of life.The research takes three kinds of forest in Yuelu Mountain(arboreal forest,mixed forest and shrub forest)as object.Using excavation method to investigate the spatial distribution of forest roots,Combining with dye tracing methods and laboratory analysis,in order to analyze the relationship between root characteristics and soil preferential flow.the result show that:(1)The results of the distribution of root characteristics are as follows:The distribution of different diameter(d)size of root in a same forest with soil depth are as follows:in terms of root length,The length of fine root(d?1mm)and small root(1<d?3mm)decreases with the increasing of soil depth in the arboreal forest and the shrub forest,the length of medium root(3<d<5mm)reaches a maximum in 20-30 cm soil layer.In the shrub forest,the length of fine root decreases with the increasing of soil depth,but the length of small root decreases in the "S" type,the length of medium root reaches a maximum in the 10-20 cm soil layer;The distribution of root volume,root surface area and root biomass with soil depth are similar to that of root length.The vertical distribution characteristics of root ecological niches of three forest(d?5mm)indicate:The vertical distribution of the roots belong to the type where the roots are concentrate in upper soil layer.According to the distribution of the root niche by diameter,the arboreal forest and shrub forest are anti-U type(mostly 1<d?3mm),and the mixed forests are anti-J type(mostly d?1mm).Combining the two distribution characteristics,we can see that the root system of three forest(d?5mm)was generally fine root-shallow root type.(2)The results of the preferential flow characteristics for the three forest types are as follows:The vertical and horizontal profiles of the arboreal forest and shrub forest show that the ratio of the dyeing area decreases as the soil depth increases.the preferential flow occurs mainly in the soil surface.The surface layer of the mixed forest is obviously stained.in the 20-25cm area,the region with the peak area of dyeing reappears at 20-25cm soil layer,and there is an obvious preferential flow phenomenon.According to the coefficient of variation(C.V),the development degree of preferential flow in the vertical direction of the three forest is:the mixed forest>the arboreal forest>the shrub forest,according to the ratio of the dyeing areas of different soil layers in the three forest,the development degree of the preferential flow in the horizontal direction is:the mixed forest>the shrub forest>the arboreal forest.(3)The quantitative relationship between the characteristics of plant root and soil preferential flow is as follows:According to the linear regression results between the root characteristics of the arboreal forest and the shrubs and the ratio of preferential flow areas,we can see that roots with d?3mm in the arbor and shrub forests promotes preferential flow,while relatively thick root(3<d?5mm)has no significant effect on preferential flow.However,the mixed forest is a case in point,root characteristics of different diameters and ratio of the dyeing area are inconsistent with changes in soil depth.Therefore,there is no absolute relationship between the root system and the ratio of dyeing area.Soil internal factors and other factors can also cause differences in results.The study of the relationship between forest root systems and preferential soil flow is conducive to the efficient management of surface water and groundwater.lt has guiding significance for prevention of soil erosion,water pollution,soil erosion,and landslides in mountainous areas.Because the temporal relationship only studied three plant types of winter plant roots,lack of root system exploration on the time scale.And only for the study of the effect of the root stream with d ? 5mm on the preferential flow,and the relationship between the coarse root with d>5mm and the soil preferential flow is not analyzed.The mechanism of the forest root system's influence on the preferential flow in the soil is still only preliminary and needs to be further strengthened.