PARENT SESSION
Contributed Oral Session 158: Invasive Species: Management, Modeling, and Dynamics
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 518 A, Level 5, Palais des congrès de Montréal

Spatio-temporal dynamics of the invasive species Phragmites australis in anthropogenic wetland corridors.

Maheu-Giroux, Mathieu^*,1, de Blois, Sylvie^{1, 2}, ¹ Macdonald Campus of McGill University, Plant Science Departement, Saint-Anne de Bellevue, Québec, Canada² McGill School of Environment, Montréal, Québec, Canada

ABSTRACT- The recent and rapid expansion of an exotic genotype of Phragmites australis, an emergent macrophyte showing invasive behavior in wetlands and agricultural lands of eastern Canada and the USA, provides a unique opportunity to relate dispersal patterns to landscape structure. Linear anthropogenic wetlands, such as roadside or agricultural ditches, may serve as corridors that facilitate species dispersal at the landscape scale and invasion of adjacent habitats. There is little quantitative evidence, however, on the structure and function of such habitats and their influence on invasion rate. Remote sensing data and a GIS approach were used to characterize the spatio-temporal dynamics of P.australis in a network of ditches for two distinct areas (1985-2002 and 1987-2002). Given the particular challenges of mapping P.australis in narrow linear wetlands, an accuracy assessment was first conducted to quantify the reliability of our distribution maps and to identify the sources of mapping errors. Preliminary results suggest an aggressive and rapid colonization of linear wetlands by P.australis, although the rate and dynamics differ for the two sites. Large, robust populations are generally formed by the coalescence of smaller patches and new patches often establish in the vicinity of older ones. Management of the linear wetlands seem to have a significant influence on colonization patterns. Interestingly, natural riparian habitats were not used as migration route and the expansion primarily occurred in linear anthropogenic wetlands in our study sites. Careful monitoring and management of anthropogenic wetland corridors is thus advocated, especially when they intersect areas of conservation or economic value.

Key words: Common reed, Landscape ecology, Invasion dynamics, Remote sensing