The Alaska Vegetation Classification - Alaska Geobotany Center ...

Figure 44-Closed low willow shrub of Salixplaniiolia subsp. pulchra along a smallstream in noiihwest Alaska.1I.C.l.b. Closed Low Willow ShrubDescription-These communities have at least 75 percent cover by shrubs at least20 centimeters (8 in) tall (fig. 44). Trees provide less than 10 percent cover, andshrubs over 1.5 meters (511) tall are absent or provide less than 25 percent cover.Willows commonly dominating the shrub canopy include Salixglauca, S. planifolia,and S. lanata. Myrica gale also may be present on wet sites. Common species in theherb layer include Calamagrosfis canadensis, Equisetum spp., Sanguisorba stipulata,Lafhyrus palustris, Festuca rubra, Amemone spp., and Astragalus alpinus. Feathermosses,especially Hylocomium splendens, often are common.Distribution and site characteristics-Closed low willow communities occur inmoist protected gullies and drainageways, streambanks, and on steep scarps aroundlakes and ponds in arctic and alpine tundra of interior, northern, and western Alaska.They also are present on major river deltas in south-central Alaska and probably atthe fringes of other low-elevation wetlands in south-central and interior Alaska. Soilsare usually moist and fairly well drained. A thin organic layer may be present. Standsin topographic depressions (gullies and drainageways) are protected by a thick layerof snow during winter, which melts relatively early in the spring. Permafrost usually isabsent or at least 50 centimeters (20 in) below the surface.Successional status-Communities in depressions in tundra regions may representtopoedaphic climaxes. If they change at all, it is probably in the direction of shrubtussocktundra. Lowland communities in south-central and interior Alaska are replacedeventually by forests, but this may take a long time, especially on the wetter sites.Closely related types-Closed low willow shrub is similar to closed tall willowshrub and open low willow shrub but has less than 25 percent cover of shrubs over1.5 meters (5 ft) tall and at least 76 percent cover in shrubs 20 centimeters (8 in)and taller. Closed low shrub birch-willow is codominated by dwarf birch and willow.Photographs-Racine and Anderson 1979, figure 4; figure 44, this publication.Primary references-Churchill 1955; Crow 1968: Racine and Anderson 1979:Viereck 1962, 1963.125