Application of Species Diversity Theory to Quantitatively Assess the Degree of Preferential Flow in Forest Ecosystems

This study mainly assesses the degree of preferential flow based on species diversity theory, which can provide a novel insight for the study of preferential flow. Three forest stands were selected for oak, pine, and bamboo forests. Field dye-tracing experiments were conducted to characterize the distribution of preferential flow paths. Diversity indices were applied to assess the spatial variability of flow paths distribution by measuring the relative dye-solution concentration. The differences between pine and oak/bamboo forests were statistically significant for dye coverage (DC) (P < 0.05) but not between oak and bamboo forests (P > 0.05). The differences in the matrix flow depth (U_niFr), preferential flow ratio (P_F-fr), and preferential flow dye coverage (DC_pf) between the three forests were significant (P < 0.05), while the differences in fractal dimension (FD) were not statistically significant (P > 0.05). The Simpson index (D_s), Shannon–Wiener index (H), and Margalef index (D_m) differed significantly between oak and pine/bamboo forests (P < 0.05) but not between pine and bamboo forests (P > 0.05). The Pielou indices (E) did not differ significantly between any of the forests (P > 0.05). Significant positive correlations were observed for DC, P_F-fr, DC_pf, and all four diversity indices (P < 0.05), whereas significant negative correlations were found between FD, U_niFr, and the indices (P < 0.05). Diversity indices were mainly influenced by the degree of preferential flow, in particular DC_pf, P_F-fr, and U_niFr.