Variations in erosive rainfall threshold and sediment production between karst and non-karst slopes

Abstract

Soil erosion often manifests a dual erosion mechanism of surface erosion and underground leakage on karst slopes with well-developed dual hydrological structures, leading to different erosive rainfall thresholds and sediment production from non-karst slopes. A lack of recognition of this differentiation significantly hampers the development of soil erosion control technologies and the scientific assessment of desertification control benefits. This study aims to reveal the difference of erosive rainfall thresholds and sediment yield between karst and non-karst slopes. To achieve the aims, continuous rainfall-runoff-sediment events were monitored for up to eight years from 2014 to 2021 year on karst and non-karst slope plots located at the Mahuangtian and Sangushui soil and water conservation monitoring stations of Guizhou Province, China, respectively. We found that compared to non-karst slopes, the erosive rainfall in karst slopes more commonly conforms to short duration and high intensity, while long-duration, low-intensity rainfall contributes minimally to karst slopes. The erosive rainfall threshold for karst slopes ranges from 35.4 to 45.6 mm (I₃₀: 31.2–36.2 mm·h⁻¹), non-karst slopes range from 11.8 to 18.8 mm (I₃₀: 10.07–13.1 mm·h⁻¹), and significant differences (P < 0.01) is found between the two slopes. The soil and water conservation measures notably elevate the erosive rainfall threshold. In non-karst slopes, the erosive rainfall threshold is conventional tillage < no tillage < artificial forest, karst slopes are artificial forest (no terrace) < artificial forest (terrace) < natural recovery. There is a significant (P < 0.01) difference in sediment yield between karst and non-karst slopes, where non-karst slopes exhibiting sediment yields far higher than karst slopes (approximately 42 times). There is a positive correlation between rainfall amount, I₃₀ and soil erosion, both of them are the primary rainfall characteristics influencing erosion. Specifically, soil loss in karst slopes is more closely related to I₃₀, while it is more related to rainfall duration on non-karst slopes.