Following quantitative sampling of riparian and forest plant communities bordering on Lac des Deux-Montagnes, a classification and a plant community pattern analysis were made. First a community classification was established by using an hierarchic agglomeration cluster analysis technique. These communities were mapped at a 1:10 000 scale. Second, by superimposing on this map, soil and topographic maps of the same region, a systematic sampling of the maps was done. The variables considered were elevation, drainage, aspect, slope, soil great groups, soil series, deposit, soil texture, stoniness, parent rock, and topography. The discrimination potential of these abiotic variables over the classification was investigated by means of information theory. The variables which most controlled the plant community pattern distribution in the studied area were soil texture, slope, elevation, and aspect. To study relationships among the abiotic variables and their relation to the plant communities, contingency tables, based on the map sampling, were prepared. By analysing each box of these tables it was possible to characterize each of the plant communities and establish the toposequence for nine communities. These communities were dominated respectively by Acer saccharum, A. saccharinum – Cephalanthus occidentalis, A. saccharinum – Fraxinus pennsylvanica, A. saccharinum – Matteuccia struthiopteris, A. saccharinum – Phalaris arundinacea, Pinus strobus, Quercus bicolor, Q. rubra, and Salix sp.