Circumpolar Arctic Vegetation Unit B2

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Hierarchy of Geobotanical Vegetation Map Units (Walker DA 2002)

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B2. Cryptogam barren complex (bedrock)

Areas of exposed rock and lichens interspersed with lakes and more vegetated areas, as found on the Canadian Shield. Subzones C and D.

Detailed Description

Bedrock covered with lichens, usually mixed with many lakes and the zonal vegetation. The largest areas are on Precambrian granite and gneiss bedrock of the Canadian Shield, but also in the high elevation areas of Siberia, northeast Asia, Alaska, and Greenland, which are mapped as part of the mountain complex (Unit B3 and Unit B4). Areas between bedrock outcrops commonly have dwarf shrubs and fruticose lichens. Found in Subzones C and D.
Area: 372 x 1000 km².

Representative Syntaxa

Communities of the class Rhizocarpetea geographici Wirth 1980 (Canada, on granite bedrock).

Dominant Plants

Saxicolous lichens cover the rock surfaces. Other plants, the grass Hierochloe alpina, and terricolous lichens grow between the bedrock outcrops.

1. 1. Saxicolous lichens: Lecidia; Lecanora; Buellia; Porpidia; Rhizocarpon; Umbilicaria; Parmelia; Xanthoriaⁿ; Caloplacaⁿ; Aspiciliaⁿ;
   2. Tree/shrub: Betula; Ledum palustre spp. decumbens; Arctous alpina; Cassiope tetragona; Vaccinium;
   3. Grass: Hierochloe alpina;
   4. Terricolous lichens: Cladonia; Cladina; Flavocetraria; Masonhalea richardsonii; Stereocaulon; Bryocaulon divergens; Alectoria ochroleuca;

^a=acidic, ⁿ=non-acidic