Occurrence, spatial distribution and succession of plants in contaminated sediments in urban stormwater basins
Détermination, distribution spatiale et évolution dans le temps des plantes sur des sédiments contaminés de bassins d’infiltration urbains
Résumé
We identified over a decade the evolution of species richness of flora and its abundance on two types of vegetated basins: Minervewherethe vegetation was originally planted, and the other naturally colonized (called Django). In Minerve, we observed a gradient from upstream (near the water entry) to downstream (farthest from this water entry) for parameters like organiccontent, height oflayer and trace element contents. In Django, the distribution is less clear, but we also observed zones with contrasting contents in organic matter and heavy metal. The regression of helophytes communities on Minerve for the benefit of ruderals pioneer species marks the evolution of the site. Since 1999, over 93% of implanted species have disappeared, but the diversity of helophytes seems to have stabilized since 2008withonly 12.5% of variation for the number of such species. On the basin of Django, the number of species remained stable since 2008. But, the decrease of almost 50% of macrophytes recovery rate, reduced to Phalaris arundinacea, Typha latifoliaand Schoenoplectus tabernamontanii, emphasizes a change in entering water flow rates. The dominant flora found in infiltration basins evolves over time with euryece species of pseudo-metallophytes macrophyte group (Typha latifolia, Phragmites australis, Iris pseudacorus, Phalaris arundincea), ruderal species typical of dry grasslands (Asteraceae, Poaceae, Brassicaceae) and wetland species (Rumex sp.). But before all, these plants are mainly divided/distributed in theses basins according to hydrological factors, i.e. water availability among others
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