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Poster De Conférence Année : 2022

Response of riparian vegetation to the restoration of lateral connectivity: the case of the dismantling of old groyne fields on the Rhône River

Résumé

On some of its reaches, the Rhône River was a braided river with a bed of several kilometers wide before major corrections. As a result of two important correction phases, namely rectification and derivation, the geometry of the river has been stabilized into a single channel and the flow of water and sediment has been profoundly altered. To restore the hydrogeomorphological processes, as well as the ecological functioning of some sections of the “old channel” of this large river, the dismantling of several hundred of meters of groyne fields has been implemented. The work consisted of dismantling the old infrastructures and redesigning the banks to promote contrasting topographic profiles and allow erosion. To assess the effects of these works on riparian vegetation, a monitoring program of four restored sites was initiated in 2017. By following the temporal variations in several environmental parameters and in the cover and richness of plant species sampled in quadrats, changes in the structure and dynamics of riparian communities were characterized. The restored sites were quickly recolonized by a large diversity of plants, especially during the first year after restoration by many annual species, sometimes exotic. Over time, the plant communities showed a progressive and coherent structuring along the recreated topographic profiles, including significant variations in species composition. While the ecological gains of this restoration appear undeniable in the short term, the unfolding of the ecological succession should quickly lead to the development of competitive native and exotic species with high cover that could induce a certain homogenization of the communities. This case study illustrates the complexity of the restoration of highly anthropized systems and invites the deployment of more process-based restoration, including the reactivation of the river erosive capacities and channel mobility, associated with bedload transport.

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Dates et versions

hal-04145887 , version 1 (30-06-2023)

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Paternité - Pas d'utilisation commerciale - Pas de modification

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  • HAL Id : hal-04145887 , version 1

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Philippe Janssen, Hervé Piégay, André Evette. Response of riparian vegetation to the restoration of lateral connectivity: the case of the dismantling of old groyne fields on the Rhône River. First International Conference on Riparian Ecosystems Science and Management, Apr 2022, Bratislava, Slovakia. ⟨hal-04145887⟩
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