Alaska Arctic Plant Communities

30. Cassiope tetragona-Dryas integrifolia subtype typical

Bioclimate Subzone: D

Floristic Subprovince: Northern Alaska

Substrate Chemistry: Nonacidic

Position along mesotopographic gradient: Snowbed, early-melting

Summary of Habitat: Moist nonacidic early-melting snowbeds in subzone D

Described from: Prudhoe Bay (Walker 1985, Walker 1990)

Common plant functional types and species:

Hemiprostrate dwarf shrub: Cassiope tetragona;

Prostrate dwarf shrubs: Dryas integrifolia; Salix reticulata;

Sedge: Carex scirpoidea; Carex bigelowii;

Forb: Pedicularis capitata; Papaver macounii spp. discolor; Bistorta vivipara; Astragalus umbellatus; Parrya nudicaulis;

Moss: Tomentypnum nitens; Hylocomium splendens; Distichium capillaceum; Ditrichum flexicaule; Sanionia uncinatus; Rhytidium rugosum; Hypnum procerrimum;

Lichen: Flavocetraria nivalis; Flavocetraria cucullata; Cetraria islandica; Dactylina arctica; Masonhalea richardsonii;

General Comments:

• Snowbed sites within nonacidic portions of subzone D on the Arctic Coastal Plain were well characterized by M.D. Walker (1990) in her study of pingo vegetation on the central Arctic Coastal Plain. She divided the snowbeds into four stand types: (1) Phippsia algida-Saxifraga rivularis (very late-melting, wet snowbed sites, 4 relevés); (2) Salix rotundifolia-Dryas integrifolia (well drained snowbeds with deep late-melting snow, 36 relevés), (3) Cassiope tetragona-Dryas integrifolia (well-drained nonacidic early-melting snowbeds, 57 relevés); (4) Dryas integrifolia-Astragalus umbellatus. She further subdivided the Cassiope tetragona-Dryas integrifolia stand type into two subtypes: Vaccinium uliginosum-Salix glauca (28 relevés) which occurs in warm south-facing snowbeds of subzones D and E (and are not included in the Cassiope-Dryas vegetation type described here), and Cassiope tetragona-Dryas integrifolia (21 relevés), which occurs in colder microsites and is the type described here.

Other names from the Alaska literature:

• Stand Type U6, Moist Dryas integrifolia, Cassiope, Cetraria nivalis dwarf shrub, fruticose lichen tundra, 3 relevés (0901, 1416, 1509); Stand Type Cassiope tetragona-Dryas integrifolia, facies Cassiope tetragona-Dryas integrifolia, Prudhoe Bay, 21 relevés, M.D. Walker (1990).