Abstract

Hydrological connectivity plays a major role in shaping both the habitat conditions and the biota in floodplain ecosystems. Current restoration strategies in large river floodplains often focus on the increase in lateral connectivity of secondary channels. However, the knowledge on the effect of restoration strategies on biodiversity remains limited. In this study, a framework was constructed to assess the level of lateral connectivity in thirteen cut-off channels of two braided sectors of the Rhône River (France). The effect of restoration measures on macroinvertebrate diversity was assessed. Changes were measured within (i.e. alpha diversity) and between channels (i.e. beta diversity). The coherence of the relationships established for some of the richness and trait-based metrics demonstrated their potential for the development of invertebrate-based tools to predict and monitor river-floodplain changes associated with restoration. At the channel scale, an increase in lateral connectivity induced a significant change in macroinvertebrate composition, a decrease of total richness and functional diversity. It is recommended that floodplain-scale restorations focus on diversification of the lateral hydrological connectivity of channels, thereby, conserving a maximum of biodiversity.