Importance of grass stolons in mitigating runoff and sediment yield under simulated rainstorms

Abstract

The influence of grass cover on surface runoff and erosion processes on hillslopes differs with plant morphology and grass components (e.g., leaves, stems and roots). However, the importance of grass components, especially stolons, in reducing runoff and sediment yield is not fully understood. Thirty field simulation experiments with rainfall intensities of 90 mm h−1 were performed to study the effects of three grass species (Trifolium repens, Cynodon dactylon and Eremochloa ophiuroides) and their aboveground and belowground components on runoff, hydrodynamic parameters and sediment reductions during rainstorms. To examine the effects of different grass components on soil erosion, three management treatments, intact grass plants (IG), grass stems and roots (SR) and only grass roots (OR), were applied to each grass species. The results showed that the three grass species effectively reduced runoff and soil erosion, and the erosion reduction was greater than the runoff reduction. The highest reduction in runoff (78.2%) and sediment yield (97.9%) was observed for E. ophiuroides, followed by the T. repens and C. dactylon plots. The overland flow velocity and runoff energy increased with the sequential removal of grass aboveground components and led to increasing runoff and erosion. The effects of grass components on runoff and erosion reduction varied with grass species and plant morphology. The aboveground components had a greater impact on runoff reduction, and the roots primarily contributed to sediment reduction in T. repens and C. dactylon, which have erect stems. However, the contribution rates of grass stems to runoff and erosion reduction were highest for E. ophiuroides with well-developed stolons at 41.51% and 61.04%, respectively, which were much higher than the leaves and roots. This finding indicated that grass stolons played an important role in reducing runoff and sediment with efficiencies of 32.44% and 59.79%, respectively. These results help guide the selection of grass species with the best traits for erosion control and highlight the importance of grass stolons in preventing water erosion caused by extreme rainstorms.