The Alaska Vegetation Classification - Alaska Geobotany Center ...

Closely related types-Sedge-birch tundra is similar to wet sedge meadow tundraand mesic sedge-grass tundra but has a substantial dwarf birch component. At theother extreme, some shrubby stands may be similar to birch-sedge fens (not yetreported from northern Alaska) or birch and ericaceous shrub tundra but have lessthan 25 percent shrub cover.Photographs-tiettinger and Janz 1974, plate 11A.Primary references-Hettinger and Janz 1974.Communities-Carex bigelowii-C. aquatilis-Betula nana (Hettinger and Janz 1974).ill.A.2.j. Sedge-Dryas TundraDescription-Sedge-dryas tundra communities are dominated by sedges (mostcommonly Carex aquafilis or C. bigelowii but Eriophorum angustifolium andKobresia simpliciuscula also are included) and have a substantial component ofDryas integrifolia or D. ocfopefala. Total shrub cover (including dryas) is less than25 percent. Willows and ericaceous shrubs may be minor components of thevegetation. Nonsphagnaceous mosses (often including Drepanocladus spp. andTomenfhypnum nitens) are common: lichens usually are scarce. Canopy height isless than 30 centimeters (12 in) and commonly lower. Cover may be open tocomplete.Distribution and site characteristics-Sedge-dryas tundra is common on protectedmesic alpine slopes and calcareous tundra lowlands throughout the State exceptsoutheastern Alaska. In lowland wet to mesic areas (terraces, flats, polygon rims), itis more or less restricted to calcareous substrates with circumneutral soil reaction. Inalpine areas, it is found on both calcareous and acidic parent materials. Sometimesthese communities occur in a mosaic pattern with other communities. An examplewould be low-center polygons with wet sedge meadow tundra in the centers andsedge-dryas tundra on the rims.Lowland soils supporting these communities include Pergelic Cryaquepts and PergelicCryaquolls. An organic mat a few centimeters thick usually is present at the surface.Solifluction lobes are common in Communities on slopes. Permafrost has beenreported at depths of 25 to 30 centimeters (10 to 12 in) at sites on the arctic coastalplain: the active layer is probably thicker at alpine sites.Successional status-Successional relations of sedge-dryas tundra are unknown.Drying trends probably would favor the dryas; trends toward increasing moisture or(in the lowlands at least) increasing acidity probably would favor the sedges.Closely related types-Some sedge-dryas communities are similar to mesic sedgeherbtundra communities but have a greater cover of dryas. At the other extreme,stands with abundant dryas are similar to dryas-sedge tundra (open dwarf scrub) buthave less than 25 percent of dryas cover.Photographs-Drew and Shanks 1965, figure 12; Johnson and others 1966, figures5 and 9; Webber and Walker 1975, p. 85.Primary references-Drew and Shanks 1965, Johnson and others 1966, Webberand Walker 1975, Webber and others 1978.175