Runoff and erosion processes on bare slopes in the Karst Rocky Desertification Area

Underground pore fissure and bedrock bareness are the main factors that lead to complicated mechanisms of soil erosion in karst regions. The objectives of this study were as follows: a) to measure runoff and sediment generated from the surface and underground in the karst bare slope; and b) to analyse the impacts of underground pore fissures and bedrock bareness rates on soil erosion. To achieve these objectives, we designed an experiment in which underground pore fissure degrees and bedrock bareness rates were varied, and their impacts on soil erosion were measured. The results showed that i) runoff and sediment yields from the surface and underground increased with increasing rainfall intensity, and the surface runoff was much more easily generated when the rainfall intensity was greater; ii) surface runoff yield first increased and then decreased with increasing bedrock bareness rates, while the runoff yield in underground pore fissures increased with increasing bedrock bareness rates; thus, sediment production on the surface and in underground pore fissures showed the same pattern, i.e., first decreased and then increased; iii) the surface runoff and sediment generally decreased with increasing degrees of underground pore fissures, while that of underground pore fissures presented a different pattern; and iv) rainfall intensity, bedrock bareness rates and underground pore fissure degrees were the important factors affecting soil erosion processes in karst bare slopes because the bedrock bareness rates and underground pore fissure degrees were the main factors causing the uneven distribution of runoff and sediment on soil surfaces and underground. Therefore, soil and water loss in underground pore fissures was the special pattern and main difference in soil erosion processes in the karst region compared with other regions. These results have theoretical and practical significance for understanding soil erosion mechanisms and controlling soil and water loss in karst regions.