Phytosociological description of the forest vegetation of southeastern Labrador

Abstract

A floristic analysis of the forest vegetation of southeastern Labrador was conducted using the phytosociological methods of Braun-Blanquet and a phytosociological table was constructed with the FORTRAN program TWINSPAN, which produces hierarchical classifications by two-way indicator species analysis. A total of 88 relevés incorporating 77 species are grouped into five major assemblages: birch, fir – spruce – feather moss, spruce–fir, spruce–Pleurozium, and spruce – Sphagnum fuscum communities. The five communities, as arranged from birch to spruce – Sphagnum fuscum, display decreasing trends in productivity, site quality, and richness of vascular flora, and increasing prominence of oligotrophic species, primarily cryptogams and ericaceous shrubs. Black spruce and balsam fir comprise more than 95% of the forest canopy in this region, whereas paper birch is restricted to moist and well-drained slopes, and white spruce, aspen, and balsam poplar are rare. Factors suggested as responsible for the limited productivity and depauperate vascular flora of the forests in this region include: semipermanently frozen soil, short growing season, nutrient-deficient mineral substratum, and intensive root competition in the poorly aerated soil. The low incidence of fire in this maritime climate is responsible for the old and uneven age structure of the conifer forests and the development of a thick bryophyte cover and deep organic humus that limit stand productivity.