Effect of slope position on the spatial distribution of soil preferential flow paths based on point pattern analysis

The mechanisms of soil preferential flow occurrence and development are influenced by topographic and geomorphological factors. However, the complex distribution patterns of soil preferential flow paths on different slopes remain unclear. Therefore, taking the subtropical evergreen broad-leaved forest area of Simian Mountain as the study area, this study conducted a quantitative analysis of the spatial distribution characteristics and spatial association of soil preferential flow at different slope positions (slope shoulder (SS), mid-slope (SM) and slope foot (SF)) using field staining tracer tests and spatial point pattern analysis. Results showed that the maximum infiltration depth, the depth of matrix flow, average dye coverage, preferential flow fraction and length index of the SM plot were all greater than those of the SS and SF plots. The number of preferential flow paths in different slope positions decreases with soil depth, with most preferential flow paths measuring 2.5-5.0 mm in each soil layer. The total number of preferential flow paths in SM plot was approximately twice that of the SS and SF plots, and the preferential flow paths in SM plot, regardless of pore size, were all in an aggregated distribution. These findings indicated that differences in soil physical properties and vegetation coverage at different slope positions lead to variations in the spatial distribution and association of soil preferential flow paths. Accordingly, strategies must be modified for the distribution, storage and utilisation of soil water resources. This study provides a theoretical basis for the effective management and protection of water resources in the Simian Mountain area and a scientific basis for exploring the mechanisms of the occurrence and development of the water cycle in forested watersheds.