The Alaska Vegetation Classification - Alaska Geobotany Center ...

Primary referencecHanson 1951; Pegau 1972; Steigers and others 1983; Viereck1963, 1966, 1983.Communities-Betula glandulosalVaccinium uliginosum-Empetrum nigrum-Ledumdecumbens’iichens (Anderson 1974, Batten 1977, Hanson 1953, Hettinger andJanz 1974, Hulten 1966, Jorgenson 1984, Kessel and Shaller 1960, Pegau 1968,Steigers and others 1983, Webber and others 1978, Young and Racine 1978).Betula glandulosalfesfuca alfaica-Vaccinium spp./feathermosses-lichens (Hanson1951, Hettinger and Janz 1974, Pegau 1972, Viereck 1963). BefulaglandulosaIFesfuca alfaica4eathermosses (Batten and others 1979; Viereck 1962, 1966).Betula glandulosa-Vaccinium spp.-Carex bigelowii (Churchill 1955, Hanson 1950).Befula glandulosa-Ledum decumbens-Vaccinium vifis-idaea-Arcfagrostis lafifolia(Churchill 1955). Befulaglandulosa-Salix spp./Carex bigelowii-Ledum decumbens/feathermosses-lichens (Hanson 1951. Scott 1972). Betula nana-Rubus chamaemorus-Ledum decumbens-Vaccinium spp. (Craighead and others 1988).ll.C.2.d. Open Low Shrub Birch-Ericaceous Shrub BogDescription-These communities have 25 to 75 percent cover by shrubs at least20 centimeters (8 in) tall. Trees overtopping the shrub canopy provide less than10 percent cover and tall shrubs (over 1.5 meters or 5 ft) provide less than 25 percentcover. Common dominants include Befula glandulosa, 6. nana, Vacciniumuliginosum, V. vifis-idaea, Ledum decumbens, Empefrum nigrurn, and Andromedapolifolia. Other locally common shrubs include Myrica gale, Pofenfilla fruticosa, Salixplanifolia, and S. reticulafa. Small stunted spruce trees are scattered in some stands,usually black spruce in interior and south-central Alaska lowlands and white spurcenear tree line. A wide variety of sedges and other herbs may be present. Somecommon species include Rubus chamaemorus, Eriphorurn angustifolium, Carexaquafilis, C. limosa, C. pauciflora, C. rotundafa, and C. magellanica. OccasionalEriophorum vaginafum or Carex bigelowii tussocks may be present, and Equisetumfluviafile sotlletimes is abundant. Sphagnum spp. are abundant at most sites but alsocan be absent. Feathermosses, Dicranum spp. and Polyfrichum spp., are locallycommon. Common lichens include Cetraria islandica, C. cucullafa, Cladonia spp.,and Cladina spp.Distribution and site characteristics-Shrub birch-ericaceous bog communitiesare common on wet, peaty substrates in south-central, interior, western, and tosome extent northern Alaska. In many cases, these communities occupy the ridgesof string bogs but they also occupy unpatterned wetlands. The substrate is peat,usually if not always composed at least partially of sphagnum mosses. The peat isat least 20 centimeters (8 in) thick, and accumulations greater than 4 meters (13 ft)thick have been reported (Hogan and Tande 1983). Microrelief is usually present,consisting of hummocks or narrow elongated ridges. The peat usually is acid with apH of about 4.5 to 5.5. Permafrost is present at depths of 30 to 100 centimeters(12 to 40 in) at most sites but is absent from many of the southernmost stands.Successional status-These communities may develop in some cases from sedgemeadows or bog meadows as peat accumulates and the upper part of the peatbecomes hummocky and drier, thereby enabling shrub invasion. They also maydevelop from shrub-tussock bogs if peat accumulates and overruns the tussocks. Ifgrowing-season warmth is adequate and the peat is not too wet, trees (primarilyblack spruce) may invade these sites and eventually transform them to woodlandsor dwarf tree woodland scrub.133