Morphological and distribution variability of preferential flow in plantation soils on the purple sandstone hillslopes using image analysis

Preferential flow is more rapid water and solutes transport in soils, and it can control the flood process in watershed. The extent of preferential flow in different age Chinese fir (Cunninghamia lanceolata) plantation soils on purple sandstone hillslopes was investigated in ponded infiltration tests using brilliant blue dye. Veridical and horizontal infiltration patterns were photographed to assess morphological and distribution properties. Conductivity of preferential flow was 2.34-2.68 times as much as that of soil matrix flow, and thus increased the penetrability of plantation soils. Parameters `dye coverage´ (DC) and `distance to nearest point´ (DNP), obtained from computer image analysis, indicate that significant discrepancies on morphology of preferential flow exist in different age Chinese fir soils and the distribution of preferential flow is aggregative. `Pathway factor´, `root factor´ and `soil physical factor´ can explain 92% of the morphological variation by factor analysis. Plant growth and soil properties influence the formation mechanisms of preferential flow.