Combined effects of moss colonization and rock fragment coverage on sediment losses, flow hydraulics and surface microtopography of carbonate-derived laterite from karst mountainous lands

Abstract

Moss and rock coverage play important roles in the soil erosion processes of karst mountainous lands. We conducted simulated rainfall experiments to investigate the combined effects of moss colonization and rock fragment coverage (RC) on the sediment losses, flow hydraulics and surface microtopography of karst carbonate-derived laterite. Soil slopes with moss colonization and different rock fragment coverages (0, 30 % and 60 %) were subjected to simulated rainfall with intensities of 100 mm h−1 in 50 cm × 30 cm × 15 cm flumes. Two sequential soil erosion events, E1 and E2, were induced with two rainstorm events; E2 was induced 24 h after E1. The results showed that the mean runoff rates (MR) of moss-covered slopes with 0 and 30 % RC were significantly lower than those of bare slopes (by 27.78 % and 24.06 %, respectively), and this effect gradually decreased as RC increased. Moss coverage also significantly decreased the mean flow velocity, and RC without moss coverage increased the flow velocities during rainfall. Moss-covered slopes showed significant decreases in mean sediment loss (MSL) (by 64.87 %, 78.89 % and 87.03 % for the 0, 30 % and 60 % RC in the E1 + E2 conditions, respectively) relative to bare slopes, and RC increases also decreased MSL. In addition, moss colonization significantly increased the initial slope roughness in both the horizontal (cl) and vertical (RR) directions. With moss coverage, slope roughness was less affected by slope erosion events due to protective effects. These results provide reference data for researching the mechanisms of moss and rock coverage for controlling and preventing karst slope erosion.