The Alaska Vegetation Classification - Alaska Geobotany Center ...

II.D.1.b. Dryas-Sedge Dwarf ShNb TundraDescrlptlon-These communities are dominated by Dryas spp. and also have astrong sedge component. Carex scirpoidea, C. misandfa, C. bigelowii, Kobresiamyosuroides, and several other sedges can be codominant with the dryas. Otherdwarf shrubs, such as Salix reticulafa and Arcfostaphylosspp., may be common.Grasses and broad-leaved herbs may be scattered (for example, Hierochloe alpina,Hedysarum spp., Saxifraga spp.). Mosses, commonly Tomenthypnum nifens,Rhyfidium rugosum, and Hylocomium splendens, are common as are fruticoselichens such as Cladonia spp. and Cetraria spp. The dryas, associated shrubs, andmosses form a mat a few centimeters thick through which the sedges and otherherbs, if present, grow to heights of 10 to 30 centimeters (4 to 12 in). Trees areabsent, and shrubs tailer than 20 centimeters (8 in) are absent or provide less than25 percent cover. Shrub species that normally grow taller than 20 centimeters (8 in)(such as Betula glandulosa, 6. nana, Salix glauca, and S. brachycarpa) are absent orprovide less than 20 percent cover. Total plant cover ranges from open to completebut often is greater than 75 percent.Distribution and site characteristics-Dryas-sedge dwarf shrub tundra wmmunitiesare common on alpine sites throughout the northern two-thirds of the State.They occupy well-drained soils that are usually not quite as exposed and windsweptas those supporting dryas tundra communities. The permafrost table is at least50 centimeters (20 in) below the surface and usually much deeper.Successional status-Successional relations are unknown. Most of these communitiesprobably are stable and change slowly with time.Closely related types-Dryas-sedge tundra is similar to dryas tundra but has moresedges. It also is similar to dryas-lichen tundra, but sedges are more important thanlichens. It is similar to sedge-dryas (herbaceous) tundra but has more than 25 percentshrub cover, primarily dryas. Some stands may be similar to some of the dwarfericaceous scrub tundra types or dwarf willow scrub tundra types, but ericaceousshrubs and willows are less important or absent entirely. Some stands may evenresemble some mesic shrub birch-ericaceous shrub communities but lack a shrubbirch component and have only minor quantities of ericaceous shrubs.Primary references-Drew and Shanks 1965, Gjaerevoll 1954, Viereck 1963.Communities-Dryas ocfopefala-Carex scirpoidea (Gjaerevoll 1954). Dryasoctopetala-Kobresia myosuroides (Drew and Shanks 1965, Hanson 1951, Johnsonand others 1966, Spetzman 1959). Dryas ocfopefala-Kobresia simpliciuscula(Gjaerevoll 1954). Dryas ocfopefala-Vaccinium vitis-idaealuzula spp.-Carexmisandfa (Childs 1969). Dryas ocfopetala-Carex franklinii (Gjaerevoll 1954).Dryas octopefala-Salix arcfica-Carex bigelowii-mosses (Anderson 1974). Dryasintegrifolia-Salk reticulafa-Carex scirpoidea (Batten 1977, Drew and Shanks 1965,Hanson 1953, Hettinger and Janz 1974). Dryas infegrifolia-Carex misandfa-Rhyfidium148