The Alaska Vegetation Classification - Alaska Geobotany Center ...

Communltles-Salix planifolia (Craighead and others 1988). Salixplanifolia-Vaccinium spp./Arcfagrosfis lafifolia (Craighead and others 1988). Salix planifolia-S.lanafa-Myrica gale/Calamagrostis canadensis (Craighead and others 1988). Salixplanifolia/Equisefum arvense (Webber and others 1978). Salix glauca-8 planifolia-S.lanafa/Equisefum arvense (Craighead and others 1988; Pegau 1968; Racine 1977;Racine and Anderson 1979; Viereck 1962, 1963). Salix glaucaPefasifes frigidus(Churchill 1955). Salix /anafa/Carexspp. (Craighead and others 1988). Salixlanafa/Equisefumspp. (Craighead and others 1988). Salix lanata/Carex aquafilis-Equisetum arvense (Scott 1974a). Salix spp./Fesfuca rubra (Crow 1968). Salixspp./€quisetum prafense (Crow 1968).II.C.1.c.Closed Low Shrub Birch-Willow ShrubDescription-These communities have atleast 75 percent cover by shrubs at least20 centimeters (8 in) tall (fig. 45). Treesprovide less than 10 percent cover andshrubs over 1.5 meters (5 ft) tall provideless than 25 percent cover. The shrubcanopy is dominated by shrub birch(Betula glandulosa or 6. nana) andwillows (commonly Salix planifolia andS. lanafa). The herb layer is usuallysparse. Mosses, such as Hylocomium sppand Aulacomniumspp., form a mat underthe shrubs.Distrlbutlon and Sitecharacterlstics-closed low shrubbirch-willow shrub is uncommon vegetationthat has been reported from thenorthern foothills of the Brooks Range,Figure 45-Closed low mixed birch and willowshrub of Betula glandulosa Salix lanata subsp.richardsonii. S. alauca. and Salix danifoliasubsp. pulchrah scattered whiie spruce on ariver terrace in the Alaska Range.where it occupies colluvial deposits near valley bottoms. Soils are generally PergelicCryaquepts or Histic Pergelic Cryaquepts. Microrelief patterns are absent. Permafrostis present, but thickness of the active layer is unknown.Successional status-Shrub birch-willow shrub often is replaced by shrub-tussocktundra or wet sedge meadow, depending on soil moisture. This probably takes a longtime, and it may be better to consider these communities as topoedaphic climaxes.Closely related types-Closed low shrub birch-willow shrub is similar lo closedtall shrub birch-willow shrub and open low shrub birch-willow shrub but has at least75 percent shrub cover and less than 25 percent tall shrub cover. It also is similar toclosed low shrub birch shrub and closed low willow shrub but has a dominant componentof both shrub birch and willow.Photographs-Figure 45, this publication.Prlmary referencdorgenson 1984.