ARCTIC Vegetation Distributions along Lichen-Dominated Slopes of Opposing Aspect in the Eastern Canadian Subarctic
ABSTRACT. Detailed vegetation surveys along two opposing slopes in the boreal forest-tundra ecotone of Quebec-labrador reveal distinct distributions and habitat preferences of prevalent lichen and shrub species. The presence or absence of a protective shrub layer was the main determinant of lichen d...
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| Format: | Text |
| Language: | English |
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1987
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.576.2054 http://pubs.aina.ucalgary.ca/arctic/Arctic40-3-221.pdf |
| Summary: | ABSTRACT. Detailed vegetation surveys along two opposing slopes in the boreal forest-tundra ecotone of Quebec-labrador reveal distinct distributions and habitat preferences of prevalent lichen and shrub species. The presence or absence of a protective shrub layer was the main determinant of lichen distributions. Generally, there was an inverse relationship between the proportional surface coverages of vascular plants and lichens. At the most exposed site, nearest the ridge top, Cetraria nivulis (L.) Ach., Alectoria ochroleucu (Hoffm.) Massal. and Cetraria nigricuns Nyl. were integrated well into the lichen mat and surrounded stoney earth circles. Increased shrub growth and protection quickly eliminated these lichens at lower elevations but allowed for more widespread growth of Cludinu rungiferinu (L.) Nyl. Cludinu stelluris (Opiz) Brodo was the most pervasive lichen and appeared to b a generalist in habitat selection. Slope aspect influenced the distributions f three lichens of limited habitat range. The northerly facing slope provides preferable conditions for their growth farther downslope, thus extending their suitable habitat range. These results suggest the possibility of defining distinct l chen habitats based on exposure or, conversely, on protection provided by the presence of a shrub-tree canopy. Key words: lichens, vegetation gradient, subarctic, topography, tundra, eastern Canadian Subarctic RkSUME. Des relevts dttaillts de la vtgttation sur deux pentes oppostes dans 1’6cotone de la toundra-for & bodale du Qutbec-Labrador, ont dvtM des distributions distinctes et des pdftrences d’habitat pour des eseces de lichens et d’arbustes @ominants. La pdsence ou I’absence d‘une couche protectrice d’arbustes ttait le facteur principal qui dtterminait la distribution des plantes vasculaires et des lichens. I1 y avait en gtntral une relation inverse entre les proportions des surfaces couvertes par les plantes vasculaires et de celles couvertes par les lichens. Au site le plus expost, p&s de la |
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