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Exotic plant species of the St Lawrence River wetlands: a spatial and historical analysis
LAVOIE Claude ; JEAN Martin ; DELISLE Fanny ; ...
Aim To evaluate the importance (number of species, plant cover) of the exotic flora in seven well-defined sectors of one of the most important transportation waterways in North America. To determine the impact of exotic species on wetland plant diversity and reconstruct the spread of some invasive species. Location St Lawrence River, southern Québec. Methods The exotic flora (vascular plants) of wetlands bordering the St Lawrence River was studied using 713 sampling stations (25 m2) along a 560-km long corridor. Results Exotic species represent 13.7% of the vascular flora of the St Lawrence wetlands. The relative plant cover occupied by exotic species is high in some of the fluvial sectors (42-44%), but low (6-10%) in the estuarine sectors. Wetlands (marshes) surrounding islands were particularly susceptible to invasion by exotic plants. Historical, abiotic and landscape factors may explain the differences observed between sites. Purple loosestrife (Lythrum salicaria L.) is the most common exotic species of the St Lawrence wetlands, but other species, namely flowering-rush (Butomus umbellatus L.) and reed canary grass (Phalaris arundinacea L.) are much more invasive. There is no linear relationship between the exotic species cover and the diversity of wetland plants; low diversity sites can be dominated by either exotic or native plant species. In the other sites, exotic species generally have little impact on plant communities and can contribute to increase diversity.
ISSN : 0305-0270 CODEN : JBIODN
Journal of biogeography A. 2003, vol. 30, n° 4, pp. 537-549 [13 pages] [bibl. : 1 p.3/4]
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