The Alaska Vegetation Classification - Alaska Geobotany Center ...

1984). Cassiope mertensiana-C. stelleriana-Empetrum nigrum (Fox 1983; Heusser1954, 1960; Ward 1957). Luetkea pectinata-Cassiope stelleriana-Lycopodiumalpinurn-Cladonia spp. (Hanson 1951).11.0.3. Willow Dwarf ScrubThese are dwarf scrub communities dominated by prostrate willows. Shrubs tallerthan 20 centimeters (8 in) (including normally erect willow species such as Salixplanifolia and S. brachycarpa of any height) are absent or provide less than 25percent cover.ll.D.3.a. Willow Dwarf Shrub TundraDescription-Willow dwarf shrub tundra communities are dominated by dwarf willowssuch as Salix polaris, S. reticulata, S. phlebophylla, S. rofundifolia, S. ovalifolia, andS. arctica. Other common dwarf shrubs (sometimes codominant) include Ernpetrumnigrum, Cassiope lycopodioides, Dryas spp., Vaccinium uliginosum, V. vitis-idaea,and Ledum decurnbens. Dwarf birch is absent or nearly so, as are shrubby, normallyerect willows such as Salix planifolia, S. lanafa, S. glauca, and S. brachycarpa.Common herbs include Hierochloe alpina, Minuartia spp., Carex microchaeta,C. scirpoidea, Carex spp., Saxifraga spp., Poa arctica, and Anemone spp. Mosses,including Dicranurn spp., Aulacomnium spp., Hylocomium splendens, Tomenthypnumnitens, and Rhacomitriumspp., may be common. Lichens may be common butusually do not provide much cover. Species include Dacfylina arctica, Cladoniarangiferina, C. alpestris, Sphaerophorus globosus, Thamnolia vermicularis, Cetrariacucullata, and, in rocky fell-fields, Rhizocarpon spp. and Umbilicaria spp. Trees areabsent or provide less than 10 percent cover. Shrubs taller than 20 centimeters (8 in)are absent or provide less than 25 percent cover. Plant cover ranges from verysparse to complete.Distribution and site characteristics-Willow dwarf shrub tundra communities arecommon in alpine areas and other windswept tundra settings throughout the Stateexcept for southeastern Alaska. They occupy a wide variety of habitats includingsnowbeds, wet high-alpine drainage channels, gelifluction lobes, windblown highcenterpolygon summits, stabilized sand dunes, mesic slopes, exposed slopes, andridges. Soils are generally thin and well drained but range from wet (snowbeds andsome gelifluction lobes) to dry. In moist and mesic settings, a thin organic mat maybe present at the surface. Permafrost is present 30 centimeters (12 in) or morebelow the surface at most sites, except for the Aleutian Islands where permafrostis absent.Successional status-Successional relations are unknown. Most communities seemto be stable.Closely related types-Willow dwarf shrub tundra communities are similar to manydwarf ericaceous shrub tundra communities but have greater cover by dwarf willows.They also are similar lo some open low shrub willow and birch communities but lacksignificant quantities of shrubby birches and willows. They also resemble mesicsedge-willow tundra but have more than 25 percent shrub cover, primarily of dwarfwillows.Photographs--Byrd 1984, figure 6; Shacklette and others 1969, figure 29.Primary references-Anderson 1974, Byrd 1984, Hettinger and Janz 1974, Klein1959. Shacklette and others 1969.157