Patterns of Community Structure and Morphology of Bryophytes and Lichens Relative to Edaphic Gradients in the Subarctic Forest-Tundra of Northwestern Canada

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Abstract
Patterns of community structure, and the distribution of acrocarpy and papillosity in mosses and fruticosity and light colour in lichens, are examined with respect to gradients of soil moisture, texture, and pH. The study is based on a collection of the terricolous bryophytes and lichens from 95 stands in the subarctic forest-tundra region of the Northwest Territories of Canada. The proportion of moss species to total bryophyte and lichen species increases with increasing soil pH and moisture and with finer soil texture; the proportion of lichens correspondingly decreases. The proportion of hepatics is not significantly correlated with any gradient. Within mosses, acrocarpous species are more numerous than pleurocarpous species throughout the region, reaching their greatest prominence on acidic, coarse-textured, dry soils, and in sites with low vascular plant species richness. The more stable, moister habitats favour a proportion of pleurocarpous moss species. Nonpapillose moss species numerically dominate in the study region, and there is no significant correlation of papillosity with either soil pH or texture. Although a significant decrease in papillosity occurs from dry to wet along the moisture gradient, it reaches a high of only 32% (dry-mesic). Most of the terricolous lichens in the region are light-coloured and fruticose; these characteristics vary litte with respect to pH, texture, and moisture. Fruticosity generally decreases with increasing soil pH and finer texture. The significance of light colour in lichens appears not to be related to the gradients investigated here.