Fig 1.
(a) Overview map of China and Sichuan province showing the broader regional context. (b) Detailed map of the study area in Sichuan province, with the sampling area marked by a red pentagram. The map was created using QGIS, and includes a north arrow and scale bar.
Fig 2.
Schematic diagram and overview of the artificial rainfall simulation system.
(a) Soil flume containing the experimental soil. (b) The central control equipment for the rainfall simulation experiment, including controllor, water pump and water tank. (c) Rainfall simulator. (d) Runoff collection flumes. The “V-shaped” trough was used to collect the surface flow and sediment, and the outlet at the bottom of the soil flume was used to collect interflow. (e) A photograph of the entire experimental process in operation.
Table 1.
The characteristics of runoff under different rainfall intensities and slopes.
Table 2.
Basic physicochemical properties of the tested soil.
Fig 3.
The effect of rainfall intensity and slope on the runoff processes.
Hydrographs showing the surface runoff rate and interflow rate over time for rainfall intensities of 60, 90, and 120 mm/h and slope gradients of 5°, 15°, and 25°. Data are presented as mean ± SD (n=3).
Table 3.
The DOC concentrations in the surface flow and interflow for different rainfall intensities and slope gradients.
Fig 4.
Changes in DOC concentration in the surface flow and interflow for different rainfall intensities and slopes.
Temporal changes in DOC concentration for surface flow and interflow under rainfall intensities of 60, 90, and 120 mm/h on slopes of 5°, 15°, and 25°. Data are presented as mean ± SD (n=3).
Table 4.
The DOC loss fluxes in the surface flow and interflow for different rainfall intensities and slope gradients.
Table 5.
Two-way anova of DOC loss characteristics.
Fig 5.
Distribution of DOC loss fluxes via surface flow and interflow.
Figures display the ratios of surface flow and interflow DOC loss fluxes to the total DOC loss fluxes under rainfall intensities of 60, 90, and 120 mm/h on slopes of 5°, 15°, and 25°. The ratios of interflow DOC loss fluxes to the total DOC loss fluxes gradually decreased with the increase of rainfall intensity and slope gradient.
Table 6.
Regression equations for slope gradients (S), rainfall intensities, (I) and DOC loss in the surface flow and interflow.
Table 7.
Correlation analysis of slope, rainfall intensity and runoff with DOC loss in surface flow and interflow.
Fig 6.
Distribution of surface flow and interflow volume.
Figures display the ratios of surface flow and interflow loss to the total runoff loss under rainfall intensities of 60, 90, and 120 mm/h on slopes of 5°, 15°, and 25°. The ratios of interflow loss to the total runoff loss gradually decreased with the increase of rainfall intensity and slope gradient.
Fig 7.
Runoff-associated DOC loss as a function of surface flow (a) and interflow volum (b) under different rainfall intensities and slope gradients.
Scatter plots show the linear relationship between DOC loss fluxes and (a) surface runoff volume (R2 = 0.93) and (b) interflow volume (R2 = 0.99). The dotted lines represent the linear regression fits for each flow pathway.