Accelerated succession in novel riparian ecosystems with long-term impact legacies, evidence from cross-comparison with a reference site

International audienceWorldwide, riparian forests have been impacted by regulation and artificialization processes. Restoration of riparian habitats has yet become a major issue. To evaluate the potential added-value of restoration operations, it is thus of great concern to compare current trajectories of degraded rivers to historical trajectories of reference rivers. We assessed whether ecological and functional trajectories varied with forest age between the constrained Rhône River and the unconstrained Drôme River. Results showed that the shift in functional traits was accelerated along the Rhône River and that patterns of trait divergence with forest age were more pronounced along the Drôme River. Also, forest composition and structure strongly diverged between the two rivers. This was mostly due to the greatest abundance of exotic species and of large diameter trees within the riparian forests of the Rhône River. Overall, we found profound differences in ecological successions between the Rhône and the Drôme rivers, highlighting rapid and irreversible divergences in trajectories