La végétation forestière du delta de Lanoraie, Québec

Abstract

The vegetation and the soil characteristics of the sandy terraces of the Lanoraie Delta, Quebec, were sampled at 84 forest sites using the methods of Whittaker and Canada Soil Information System. The ordination results show that the soil moisture regime (xeric–hydric) and the pH (3.5–5.0) are the main factors responsible for the spatial distribution of the vegetation. When these results (ordination analysis) and those of the cluster analysis are superimposed, the relationship between the five vegetation groups studied and particular ecological conditions can be seen. Thus, two groups of vegetation dominated by conifers are found in the middle of the terraces. One of these is dominated by Tsuga canadensis and the other by Abies balsamea and Picea rubens. These two groups are found on podzolic, gleyed soils with a mounded microrelief, which are strongly acidic (pH < 3.5) and have a hydric–mesic moisture regime. The remaining three vegetation groups are dominated by deciduous species. Among these, two groups arise from human activities such as logging or farming. One of these is dominated by Fagus grandifolia, Acer saccharum, Acer rubrum, and Quercus rubra and is composed of mature trees. The other is dominated by Pinus strobus, Polulus grandidentata, Populus tremuloides, or Betula papyrifera and is composed of young trees. These two types occupy the edge of the terraces where the topography is flat and the soil podzolic with a moderately to slightly acidic pH (4.0–5.0) and a xeric–mesic moisture regime. Finally the third group, dominated by Acer rubrum, is found on medium acidic (pH = 4.0), gleyed soils with a hydric–mesic moisture regime. This study shows that Acer rubrum is the best suited species for sandy, acidic, and nutrient-poor sites of the Lanoraie Delta. Key words: Lanoraie Delta, multivariate analysis, vegetation classification, Acer rubrum.