Secondary Seed Dispersal by Hydrochory During Surface Runoff Inside a Mediterranean Vineyard

Water circulation within agroecosystems can contribute to the distribution of plant communities by inducing seed dispersal through a process known as hydrochory. As vegetation is currently intensively managed in Mediterranean agroecosystems, relying on seed dispersal to increase vegetation cover and limit soil erosion could be a cost-effective approach. However, hydrochory has rarely been studied when it occurs during surface runoff in agroecosystems. In addition, hydrochory has been observed to be an efficient dispersal agent that plays a key role in both maintaining and enhancing biodiversity. Studying the effect of simple soil surface features on seed mobilization and dispersal by hydrochory during surface runoff is thus a way to gain insight into the influence of agricultural practices on the natural seed dispersal process. Here, we used seeds marked with a UV powder to track seed mobilization and movement during a typical Mediterranean runoff event over a ploughed and a vegetated surface within interrows. Surface roughness was the main factor limiting seed remobilization after seed deposition, and buoyancy did not appear to facilitate secondary seed dispersal by hydrochory. Vegetation and surface roughness influenced seed dispersal and thus confirmed previous studies in permanent and quasi-permanent water streams. However, a slope was not associated with seed dispersal, suggesting that a certain degree of slope is required to observe an effect of the slope on seed dispersal. Our study showed that accounting for seed morphology revealed that round seeds were more sensitive to surface features such as surface roughness and vegetation cover than hooked or plumed seeds, which had an influence on patterns of seed deposit during surface runoff. In the face of climate change, our results contribute to the development of biodiversity-based mitigation strategies in Mediterranean regions and vineyards.