The Alaska Vegetation Classification - Alaska Geobotany Center ...

Communltles-Picea marianaMyrica gale-Ledum decumbens/Trichophorumcaespitosumfeathermosses-Sphagnum spp. (Hogan and Tande 1983). Piceamariana/Ledum decumbens-Vaccinium vifis-idaea/Rubus chamaemorus/Sphagnumspp. (Luken and Billings 1983). Picea marianaEriophorum vaginafum (Craigheadand others 1988).ll.A.2.b. Open Mountain Hemlock Dwarf Tree ScrubDescrlptlon-These communities are dominated by mountain hemlock growingless than 3 meters (10 ft) tall. Total cover of dwarf trees is 25 to 60 percent andtotal cover 01 trees taller than 3 meters (10 ft) is less than 10 percent. Other treespecies are absent or unimportant, although the tall shrub, Sitka mountain-ash(Sorbus sitchensis), is sometimes present. Important low shrubs that have beenreported include Cladothamnuspyfolaeflorus, Menziesia fefruginea, and Vacciniumovalifolium. The dwarf shrub Empefrum nigrum also is common. Common herbsinclude Calamagrosfis canadensis, Cornus canadensis. and Fauria crista-galli.Dominant mosses are Pleurozium schreberi, Hylocomium splendens, Rhyfidiadelphusloreus, and Ptilium crista-casfrensis.Distrlbutlon and Site characterlstlcs-Open mountain hemlock dwarf tree scrubcommunities have been reported as copses or islands of low trees within peatlandsin southeastern Alaska. These sites are slightly elevated above the general levelof the peatlands and, though wet, are substantially better drained than are thepeatlands themselves. These communities also may be present on exposedsubalpine ridges.Successional status-Successional relations are unknown, but these communitiesprobably persist for substantial periods and may be climax or near-climax on thespecialized sites where they occur.Closely related types-Open mountain hemlock dwarf tree scrub communitiesresemble closed mountain hemlock dwarf tree scrub but have a more open canopy.They also are similar to open mountain hemlock forest but are composed of treesless than 3 meters (10 ft) tall.Primary reference-Worley 1977.Communities-Tsuga me~ensiana/Cladothamnuspyrolaeflorus/€mpefrm nigrum-Calamagrosfis canadensis (Worley 1977).ll.A.3. Dwarf Tree Scrub WoodlandThese communities are composed of dwarf trees (tree species less than 3 meters[lo ft] tall) with a cover of 10 to 25 percent. If shrubs, herbaceous vegetation, andbryoid vegetation are lacking, dwarf tree cover can be as low as 2 percent. Treesover 3 meters (10 ft) tall provide less than 10 percent cover. Shrubs may be absentor abundant but usually are common.