Comparison of the effects of litter decomposition process on soil erosion under simulated rainfall

Overland flow parameters play a pivotal role in soil erosion, which are affected by litter cover in forests. In this study, the litter layer of Pinus massoniana (Masson pine) was divided into non-decomposed and semi-decomposed layers. Seven litter coverage mass gradients, two slopes (5° and 10°), and two rainfall intensities (60 and 120 mm·h−1) were used for a systematic study of the effects of litter layer changes on overland flow dynamic characteristics. The objectives of this study were to explore the soil erosion process in litter different decomposition stages; to explore various relationships between hydraulic variables and litter characteristics. In the process of litter decomposition, overland flow patterns changed from transitional flow to laminar flow and from rapid flow to slow flow. The semi-decomposed layer’s Reynold’s number (Re), resistance coefficient (f), and soil separation rate ($${D}_{r}$$ D r ) were lower than that of the non-decomposed layer under the same conditions. Litter coverage, runoff and the diameter of the litter were major parameters that affected the Re, f, Fr, and Dr. Shrubs with wide leaves should be selected for understory vegetation replanting. The results of this study are helpful to understand the mechanisms of litter influencing erosion processes in different decomposition stages.