Abstract:
Objective The phenomenon of preferential flow in southwest karst plantations under different infiltration volumes is needed to make sure and to clarify the influence of infiltration volume on the degree of preferential flow, which is of great significance for the conservation of local plantations.
Method Through field dyeing tracing experiment and image processing technology, the morphological characteristics of preferential flow in the vertical and horizontal directions and the variation of dyeing area ratio with soil depth were obtained, and five characteristic parameters, such as preferential flow ratio, were extracted as the preferential flow indices, and the mean square difference decision method was applied to comprehensively evaluate the degree of priority flow under different infiltration water volumes.
Result Preferential flow existed in the soils of karst plantations, with preferential flow at 25 mm infiltration mainly moved in the vertical direction, while lateral flow was active at 60 mm infiltration. The ratios of soil dyed area were 5.72% and 27.92% for infiltration of 25 mm and 60 mm, respectively, and the cubic function was able to fit well the relationship between the dyed area ratio and soil depth in karst plantations under heavy and stormy rainfall conditions. When the infiltration volumes were increased from 25 mm to 60 mm, the matrix flow depth, average maximum infiltration depth and length index were significantly increased, while the preferential flow ratio and variation coefficient of dyeing morphology were significantly reduced. The preferential flow index was 0.52 at 25 mm infiltration, higher than 0.46 at 60 mm infiltration.
Conclusion Adequate external water supply will reduce the degree of preferential flow and reduce rapid soil moisture loss under planted forests in Karst areas.
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