Subzone 1: Cushion-forb

Characterized by the absence of woody plants and sedges and the dominance of herbaceous dicots, grasses, rushes, and bryophytes. Equivalent to the Russian polar desert region. It is restricted to the low-lying northern Queen Elizabeth Islands and the northern and western most edges of Ellesmere and Axel Hieberg Islands. This region is primarily within the permanent polar ice pack and has frequent summer fogs, reducing insolation and summer temperatures. Average vegetation cover is < 5 % but regions with suitable substrate can have up to 100% cover. Mean July temperatures range from 0-3°C.

Subzone 2: Prostrate dwarf-shrub

Restricted to the Arctic islands and characterized by prostrate dwarf-shrub vegetation including Salix arctica on more acidic sites and S. arctica and Dryas integrifolia (Carici-Dyradetum integrifoliae) on nonacidic sites. There are large areas with scant vegetation cover on the strongly calcareous substrates of Cornwallis, Devon, Somerset, and parts of Baffin Island. The sedge Carex aquatilis var. stans occurs in wet areas. The mesic-zonal vegetation is similar throughout both subzone 2 and 3 on the strongly calcareous substrates found in the Canadian Arctic but variation does occur in the wet, riparian, and snowbed habitats. Vegetation cover averages 5-50%. Mean July temperatures range from 3-5°C.

Subzone 3: Hemiprostrate dwarf-shrub

Found on the Arctic islands in eastern and western Canada and on the mainland west of the Foxe Basin. Characterized by the presence of dwarf-shrub heath vegetation with Cassiope tetragona on mesic acidic substrates, Salix arctica and Dryas integrifolia (Carici-Dyradetum integrifoliae) on nonacidic zonal sites with Salicetio-Cassiopetum tetragonae dominated snowbeds on nonacidic substrates, a higher diversity of sedges in the wetlands than in subzone 2, and increased presence of Epilobium latifolium communities in the riparian areas. Vegetation cover averages 50-80% and mean July temperatures range from 5-7°C.

Subzone 4: Erect dwarf-shrub

Found on the Arctic islands in the west and on the mainland of eastern Canada. Dry sites on nonacidic coarse textured soils are dominated by Salix arctica and Dryas integrifolia. Mesic (zonal) sites are characterized by the presence of Salix lanata ssp. richardsonii. Zonal vegetation on the more acidic mainland is dominated by Ledum decumbens and Betula glandulosa. Low shrub vegetation can be found along sheltered streambanks. Vegetation cover is continuous on mesic and wet sites and discontinuous on knolls and ridges. Mean July temperatures range from 7-9°C.

Subzone 5: Low-shrub

Found entirely on the mainland in Canada and characterized by low-shrub vegetation on the zonal sites, primarily Betula glandulosa on acidic sites and Salix glauca on nonacidic sites. Eriophorum vaginatum tussock tundra can be dominant on acidic substrates in the western portion of this subzone in Canada. Boreal floristic elements are common (Yurtsev 1994). A variety of tall shrubs are found in riparian and sheltered areas. Wetlands show considerable peat development. Vegetation cover is continuous except on exposed ridges and areas of the Canadian shield with minimal surficial deposits. Mean July temperatures range from 9-12°C.