Consequences of fluvial maintenance operations on the biodiversity and landscape in the Mareau-aux-Prés islands (National Reserve of Saint-Mesmin, Loire River, France)

The Mareau-aux-Prés islands, along the Loire river are characterized by a multiple channel pattern, where natural limestone riffles influence the morphology and spatial distribution of vegetated islands and secondary channels. Within these islands, in september 2012, fluvial management operations (FMO) were launched. The vegetation of the central sandy-gravelly bar (3 ha area) was uprooted and the bar level lowered in order to maintain the flow capacity of the river. The FMO are equivalent to a natural important flood : a new bare mineral substrate has appeared and since spring 2013 followed the succession of geomorphic, pioneer and biogeomorphic phases in interactions between hydro-morphodynamics and Salicaceae vegetation.This sandy-gravelly bar is an ideal field support for studying long-term ecological issues. A multi-disciplinary research programme ('BioMareau' project) is currently being conducted from 2012 to 2019, focusing on interactions and feedbacks between biotic and abiotic components and, since 2017, on landscape evolution and perception.