Are macrophytes good candidates for evaluation of restoration success? The example of reconnected side-channels of the Rhine river.

Abstract

Restoration works in the Alsace Rhine floodplain led to reconnect former side arms of the Rhine to the main course. Aquatic plant communities are used as indicators of the success of the restoration, namely the recover of the functionality of alluvial aquatic ecosystems. To test this tool we focussed on the floristic composition of communities, biological traits of species, stocks and flows of diaspores, the explanatory variables, trophic level and hydro- morphological characteristics. This study was conducted at ninerestored sites and three reference sites never disconnected from the main course. Monitoring of these parameters shows that the restored side channels have many similarities with the reference ones, especially for the floristic composition. This is mainly related to the hydro-morphological conditions, and secondarily to the trophic level and the flow of diaspores. The analysis of biological and ecological traits provides additional indices to confirm the restoration of some ecological functions. Because of their speed of installation, their adaptive strategies developed during the recolonization and their capacity to integrate dynamics of water and nutrients, mycrophytes seem good candidates for evaluating the success of the reconnection of the side arms to the river.