Are acts of selective planting and maintenance drivers for vegetation change in stormwater systems? A case study of two infiltration basins
Résumé
Infiltration basins have been designed to receive and infiltrate stormwater. Upstream, the stormwater runs off urban surfaces, is collected by the sewer system, and then routed to infiltration basins. Then, the suspended solids carried by stormwater accumulate at the surface and form a sedimentary layer. Plants then colonize the soil surface and shape a new ecological system, ruling at the same time water quality and quantity. In this study, we monitored the dynamics of vegetation over two decades in two infiltration basins. One of these basins was subjected to vegetation maintenance (planting and mowing once every year), whereas the other basin was left to be colonized by spontaneous vegetation. Basic maintenance (1/year) may change the species at the beginning of the operation of the basins, but the impact is short term. However, this may be sufficient to prevent the growth of some invasive species. In the long term, spontaneous vegetation and water regimes turn the original ecosystem into a new one, combining initial planted species with new species. Our results show that the water regime seems to be the main factor controlling vegetation and that dry conditions allow the establishment of grasslands with typical plant species. Vegetation maintenance and the management of water levels may help prevent the establishment of invasive species and maintain species for the optimal functioning of infiltration basins.
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