Abstract: Soil preferential flow affects slope runoff and water cycle in watershed. Understanding the characteristics and influencing factors of preferential flow are helpful for uncovering the mechanism of preferential flow in different vegetations. In this study, we investigated the spatial heterogeneity of soil preferential flow in a mixed broadleaf-conifer forest, coniferous forest, and shrubland in Guandi Mountain by using bright blue tracer and image analysis, and analyzed the impactsof soil physical and chemical properties. The results showed that: (1) Soil preferential flow under the mixed broadleaf-conifer forest and shrubland was in an order of upper slope > lower slope > middle slope, while the preferential flow in the coniferous forest decreased with increasing slope position. (2) The horizontal dyeing pathway in the coniferous forest and shrubland was mainly >10 mm. The total number of dyeing pathway in the coniferous forest was firstly increased and then decreased with increasing slope position, while that in the shrubland decreased with increasing slope position. (3) Electrical conductivity, organic matter content, slope position, and clay content were the main factors affecting the vertical dyeing characteristics of preferential flow, while organic matter content, sand content, silt content, and slope position were the main factors affecting the horizontal dyeing characteristics of preferential flow. Our results indicated that slope position and vegetation types had important impacts on the occurrence and development of preferential flow, improving the understanding of the effects and underlying mechanism of slope position on the preferential flow.

Key words:  slope position, preferential flow, dyeing tracer, dyeing characteristics.