Effects of plant traits and their divergence on runoff and sediment retention in herbaceous vegetation

Abstract

Plant species diversity impacts ecosystem processes, but its effects on runoff and soil erosion are not fully understood. Herbaceous vegetation control concentrated runoff and soil erosion through the increase of hydraulic roughness which leads to sediment retention. This study aims to investigate the effect of aboveground traits and their divergence (i.e., stem diameter and density, and leaf area and density) on hydraulic roughness and sediment retention in plant communities. Runoff experimentations were performed, using a sediment input, on three mono-specific and one multi-specific conditions composed of plant species with contrasting traits furthering hydraulic roughness and sediment retention. No effect of trait diversity was found on the hydraulic roughness and sediment retention; which would be explained by the absence of an optimal space use by the traits involved in the increase of the hydraulic roughness. The dominant effect of the community-weighted traits in the plant community drives the effects of the vegetation on the hydraulic roughness and sediment retention. This absence of positive effects of the trait diversity on hydraulic roughness and sediment retention constitutes an important knowledge to model runoff and soil erosion processes and to design herbaceous infrastructures for soil erosion control.