| Summary: | [Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN International audience Invasive alien species are one of the most important threats on biodiversity worldwide. The ability of exotic plants to colonize and dominate disturbed or post-disturbance areas gives them a crucial advantage. Once established they are hard to remove which can threaten the success of ecological restoration operations. Several mechanisms have been proposed to explain the success of exotic plants. In particular, biotic interactions are supposed to be involved in the containment of their development. Locally, competition for resources and space can limit the recruitment and the growth of invasive plants, both at the very early stage of propagule establishment through priority effects and also all over their growth through direct competition. Ecological restoration projects are implicitly based on these mechanisms as seeding and planting operations aim at better controlling restoration trajectories and final community composition. However it is hard to disentangle the two effects (priority and direct competition for resources) on community assemblage and particularly on resistance to invasion although they are crucial to better design restoration operations. We set up a field experiment aiming at studying the priority effect and the effect of the composition of seeding in a real restoration context. Experimental plots of 2*2m have been set along a deeply modified riverbank in the French Alps for hydraulic development purposes. We tested two densities and three seed mixes in order to study the effects of seeding composition and competition intensity. Ploughing was used to delay soil seed bank expression compared to seeding and as such to cancel its priority effects. We compared community composition and structure between treatments with a particular focus on invasive plants. Here we present the results after two growing seasons.
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