Gradient analysis of Larix laricina dominated wetlands in Canada's southeastern boreal forest

With the objective of understanding how vegetation was structured in four L arix laricina (Du Roi) K. Koch dominated wetlands in north-western Quebec, 186 point-centred quarters were sampled in four stands. For each point, bot h biotic and abiotic variables were collected and species cover was recorde d. Divisive hierarchical classification analysis (Twinspan) identified nine vegetation clusters: i) Larix laricina & Spiraea alba, ii) Larix laricina & Kalmia angustifolia, iii) Larix laricina, Picea mariana & Alnus rugosa, i v) Larix laricina & Betula pumila, v) Thuja occidentalis & Trientalis borea lis, vi) Abies balsamea & Betula papyrifera, vii) Fraxinus nigra & Onoclea sensibilis, viii) Alnus rugosa, and ix) Eleocharis smallii. Results of the canonical correspondence analyses indicated that the distribution of these clusters was mainly related to (i) distance from shore, (ii) shade (canopy cover), (iii) substrate nitrate concentration (in relation to the abundance of Kalmia angustifolia and Alnus rugosa), (iv) substrate pH (in relation t o the abundance of Sphagnum spp.), and (v) substrate conductivity. Several characteristics of the water table also affected species distribution, incl uding pH, depth, and carbon concentration. Further studies should address t he effect of the presence of Kalmia angustifolia and Alnus rugosa on larch growth.