The impacts of vegetation restoration on loess gully morphology

Background Ecological restoration featured with revegetation plays effective role on mitigating soil erosion in this area. It significantly reduced the surface runoff and sediment generation, enhanced the soil resistance to shear forces and eventually reshaped the morphology of gullies. This study focused on the morphological traits of gullies in the loess hillslope, aimed to reveal the impact of vegetation restoration on soil conservation and reflects the effectiveness of ecological restoration. Methods A agricultural hillslope and a revegetated hillslope with gully system occurred were selected to conduct the comparative analysis. High-precision 3D models, RGB images, and point cloud data were obtained using drone-based LiDAR scanning and photogrammetry. The zonation of gully systems was implemented based on slope gradient variation. The Shreve stream ordering method was applied to classify the gully channel network. Subsequently, cross-sectional of the point cloud data at gully heads, tributaries, and main gullies were extracted for gully morphology analysis. and the roughness of gully bed was quantified based on the high-resolution digital elevation model. Results The results indicate that ecological restoration resulted in noticeable difference in gully morphology between agricultural hillslope and revegetated hillslope. In the revegetated hillslope, gully heads were steeper compared to those on the agricultural hillslope. The higher the gully network order, the more diminished the morphological difference in cross-sectional profiles between the gullies on the two hillslopes. The roughness of gully bed was higher on the revegetated hillslope than on the agricultural hillslope, with bed of tributary gullies exhibiting greater roughness than that of main gullies. Conclusion Through the comparative analysis of gully morphology and gully bed roughness, this study highlighted the critical role of vegetation restoration played in soil and water conservation and demonstrated the effectiveness of ecological restoration in mediating gully morphological traits. The findings provide scientific evidence for assessing the effectiveness of ecological restoration on the Loess Plateau.