Considering both sexual and clonal reproduction could help loosen the conflict of use over Robinia pseudoacacia

Abstract

Black locust (Robinia pseudocacacia) is a widely planted tree for wood production; however, it is a very problematic invasive species through Europe. At local scale, this tree is able to invades adjacent ecosystems owing to its strong ability of asexual reproduction through root suckers. Due to this phenomenon, the role of sexual reproduction has been quite neglected at local scale. Here, we propose a double approach (i) to evaluate the ability of the species to develop under forest cover using French national forest inventory data (ii) to quantify the role of sexual and asexual reproduction at local scale using a simple visual assessment method. We evidenced that juvenile black locust regenerates in broadleaved forests where R. pseudoacacia did not contribute to the adult canopy; moreover, a significant higher presence in riparian forests relatively to non-riparian ones was demonstrated using national forest inventory data. Regeneration from sexual reproduction mode significantly contributes to local scale invasion (38% of the up-rooted juvenile plants) with a significantly higher ratio of sexual reproduction within oak dominated forests compared to pine dominated ones. We conclude that black locust forestry should consider that both reproduction modes contribute to the species natural regeneration and that both modes can occur under both coniferous and broadleaved forest cover. Thus, we propose to set up safety buffers around sensitive ecosystems such as natural reserves or riparian areas, to maintain black locust cultivation while minimising undesired invasions in natural areas.