The cartography of hydrophytes applied to the study of fluvial ecosystems: an analysis tool for the restoration of former Rhine tributaries | La cartographie des hydrophytes appliquee a l'etude des ecosystemes fluviaux: un outil d'analyse pour la restauration des anciens chenaux rhenans
1997
Klein, J.P. (Centre d'Analyses et de Recherches, Illkirch-Graffenstaden (France). Dept. d'Hydrologie et d'Environnement) | Vanderpoorten, A. | Sanchez-Perez, J.M. | Maire, G.
The aquatic macrophytes of former Rhine channels were mapped in the frame of a project of river flooding. The study site is the ancient alluvial woodland of Erstein, that covers 704 ha at 30 km South from Strasbourg. It is drained by two phreatic oligotrophic rivers disconnected from the Rhine since 1970. The forest is included in a project of flooding by the main river. The cartography of the aquatic macrophytes (34 vascular plants, 6 algae and 16 bryophytes) constitutes a reference in an attempt to assess the consequences of the polder functioning on the water quality and flora. The distribution of the aquatic macrophytes shows the current exchanges between groundwater and surface water. Hence the maps show a strong up-stream/down-stream pattern: the Characeae are restricted to the phreatic springs, the bryophytes colonize the upstream pebbly substrates, whereas the highest diversity of phanerogams is reached at the silty confluence of an eutrophic river. This pattern causes a high floristic diversity with regard to rivers still connected to the Rhine, where the floodpulse and trophic maxima due to the flooding by surface water limitate the development of the flora. Consequently it is suggested to overflood again the forest very proressively, by begining with the most silted up streams.
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