Influence Of Fine Root System And Soil Characteristic On Transport Mechanism Of Preferential Flow

Carrying out the research on preferential flow is good for understanding the impact of precipitation on the groundwater level, recognizing the formation mechanism of surface runoff and interflow, and judging the soil water conservative capacity. It also can be used to predict nutrient loss and groundwater pollution in farmland in practice provided theoretical basis for land remediation consequentley.Root system is one of the main factors which deeply influence preferential flow, especially the root hole.Both live root holes formed when the plant growth and death root holes formed after the plant death influence the formation of macropore. The soil characteristic also affect the preferential flow, such as initial soil water content, soil capillary porosity and non-capillary porosity, which affect the formation of preferential flow paths.In this study, the method of brilliant blue dye tracing was applied to explore the driving factors of preferential flow paths in Jiufeng National Forestry Park by selecting four indicators of fine plant roots and four indicators of soil characteristic.â‘ 0cm-60cm soil depth, root length density of the root system whose diameter<1mm,1mm-3mm and3mm-5mm is decreasing with the increasing depth, as well as the root biomass whose diameter <5mm.The root length density of root system whose diameter <1mm is much higher than other root system.(2)0cm-60cm soil depth, non-capillary porosity, capillary porosity and total porosity decreased with the increasing of soil depth; the content of macroaggregates decreased, and soil structure became worse with the increasing of soil depth as well; soil water characteristic curve became steeper and the capacity of the hydraulic conductivity was reduced. The soil capillary pore significantly influences the soil water holding capacity, which was positively correlation.(3) The root length density of the root system at three scale, which is root diameter <1mm,lmm-3mm,3mm-5mm, was higher in preferential flow region compared with it in soil matrix region within the same plots and depth. So was the root biomass density of the root system whose diameter<5mm and non-capillary porosity soil aggregates fractal dimension of the preferential flow area was less than the matrix flow area.Result showed that these five factors are the main factors influencing the preferential flow paths.â‘£By principal component anaysis, the main factors affecting the preferential flow path are root length density of diameter<1mm root system, root system biomass density whose diameter<5mm, non-capillary porosity, root length density of diameter<1mm root system and soil aggregates. By calculating the principal component score of preferential flow area and the matrix flow area in17micro-regions, results showed that the composite score in14plots were greater in preferential flow region than it in matrix flow area, accounting for82%of the total micro-regions, indicating that the five factors mentioned above are also the main factors influencing the preferential flow paths by the principal component analysis.