Alpine lichen-dominated communities in Alberta and the Yukon

Abstract

Alpine lichen-dominated vegetation is described with emphasis upon floristic composition, quantitative structure, and distribution of lichen communities. Macrolichens and vascular plants were quantitatively sampled using stratified random quadrats (10 cm × 40 cm) in 40 stands (30 m × 5 m) in west-central Alberta and north central Yukon Territory. Comparable acid and basic substrates, and glaciated and unglaciated sites were sampled in each region. Bray-Curtis and reciprocal averaging ordinations were used to analyze vegetation data. For both macrolichens and vascular plants, floristic similarity is greater within each region than on equivalent substrates in different regions. Three alpine macrolichen communities are described in each region which exhibit pronounced regional differences. Cetraria tilesii and Thamnolia subuliformis characterize driest sites in both regions, while Cetraria cucullata indicates mesic habitats. Cladonia spp. dominate acidic Yukon sites; Stereocaulon alpinum and Peltigera aphthosa characterize equivalent Alberta habitats. Vascular plant communities are dominated by Dryas integrifolia and D. octopetala in Alberta and Yukon areas, respectively, with dwarf willow and heath in acidic, mesic sites. Distribution of alpine communities of macrolichens and corresponding vascular plants is more strongly correlated with substate pH and moisture, than with glaciation history. Comparison with other northern studies suggests that these macrolichen communities may be found throughout the Canadian Cordillera where equivalent habitats are present.