The Alaska Vegetation Classification - Alaska Geobotany Center ...

Communities-Carex aquatilis-Dryas infegrifolia (Webber and Walker 1975, Webberand others 1978). Carex bigelowii-Dryas integrifolia (Childs 1969, Hettinger and Janz1974, Webber and others 1978). Carex bigelowii-€riophorum angustifolium-Dryasintegrifolia (Drew and Shanks 1965). Carex bigelowii-Eriophorum angustifolium-Dryasoctopefala (Anderson 1974). Carex bigelowii-C. membranacea-Dryas octopetala(Hanson 1950). Carex bigelowii-Dryas octopetala (Johnson and others 1966). Carexbigelowii-Dryas ocfopetala-Salix reticulafa (Anderson 1974, Scott 1974a, Webber andothers 1978). Kobresia simpliciuscula-Dryas integrifolia (Webber and others 1978).Eriophorum angustifolium-Dryas infegrifolia (Webber and Walker 1975, Webber andothers 1978).lll.A.3. Wet Gramlnold HerbaceousCommunities dominated or codominated by graminoids and occupying wet sites areincluded here. Forbs may be codominant in some communities, and shrubs may bepresent but provide less than 25 percent cover. Soils are saturated with water or areundewater for all or most of the growing season.lll.A.3.a.Wet Sedge Meadow TundraDescription-Wet sedge meadow tundra is commonly dominated by Carex aquafilis,€riophorumangusfifolium, or both (fig. 64). Woody plants are generally absent,though sometimes prostrate willows are important. Mosses, commonly of the generaScorpidiumor Drepanocladus, may be absent or common. Sphagnum is usually notimportant but is codominant on a few sites. Lichens are rare or absent.Scorpidium scorpioides indicates circumneutral, marly soils; Sphagnum spp. indicatesacid sites; Carex chordorrhiza is characteristic of very wet, floating sedge peats.Distribution and Site characteristics-Large stands of wet sedge meadow tundraare common on arctic lowlands, and small stands are locally common in alpine areaseverywhere except southeast Alaska. They occur on drained lake basins, lakemargins, depressions, and on level to gently sloping flood plains and terraces.Soils are fine-grained and poorly drained. They may be mineral or organic, or mayconsist of a few centimeters of organic matter over mineral soil. Permafrost ispresent, usually 30 to 50 centimeters (12 to 20 in) below the surface, though possiblyup to 1 meter (3 ft) below the surface near the southern limit of this type. Soil pHranges from circumneutral (7.5) to highly acid (4.5) (Drew and Shanks 1965,Holowaychuk and Smeck 1979). The soil is generally flooded at breakup, with a fewcentimeters of standing water persisting into at least the early part of the growingseason.Successional status-Successional relations among tundra communities arecomplex (Britton 1967). It appears that wet sedge meadows may replace grassmarshes (Afctophila fulva) if sedimentation or drainage causes the water table todrop. A further decrease in moisture may enable tussock tundra to move in. A rise inthe water table may cause tussock tundra to be replaced by wet sedge meadow.176