Vegetation Pattern and Diversity in S.E. Labrador, Canada: Betula Papyrifera (Birch) Forest Development in Relation to Fire History and Physiography

Publisher Website
Google Scholar
Abstract
(1) The Betula papyrifera (paper birch) forest of the wilderness of southeastern Labrador is described. (2) B. papyrifera forests range in size from less than 1 ha to several km2, display sharp borders with adjoining conifer forests and are restricted to steep slopes that have burned in the previous 110 years. (3) Floristically, the B. papyrifera community is distinguished from conifer forests by the presence of fourteen differential species, by the scarcity of terrestrial cryptogams and by the development of a diverse understorey of vascular plants. (4) Three minimum conditions are necessary for B. papyrifera forest development: (i) moist and well-drained soils, (ii) a nearby seed source, and (iii) an open site. (5) The nearly exclusive restriction of B. papyrifera forest to areas that have burned in the last 110 years indicates that the open-site conditions necessary for stand initiation are largely created by lightning fires. (6) Age-structure analysis demonstrates that, following fire, regeneration by B. paprifera is rapid and results in the formation of an even-aged overstory. Gradual invasion of canopy openings by Picea mariana and Abies balsamea results in the progressive conversion to conifer forest. (7) Fire maintains B. papyrifera and other early post-fire communities in a mosaic pattern and increases regional vegetation diversity. The pattern is not random, but is controlled by species autecologies, the pattern of fires and physiography. The vegetation of south-eastern Labrador is in a state of dynamic equilibrium.