The Alaska Vegetation Classification - Alaska Geobotany Center ...

ll.B.2.c. Open Tall Shrub Birch ShrubDescription-These communities are dominated by shrub birch averaging 1.5 meters(5 ft) or more in height with 25 to 75 percent tall shrub cover. Communities of shrubbirch 1 to 2 meters (3 to 6 It) tall have been reported (Batten and others 1979) butare classed with open low shrub birch communities rather than dividing the communitiesinto low and high phases.Distribution and site characteristics-These communities are not nearly ascommon as low shrub birch communities but may exist near tree line in theAlaska Range.Communities-Undescribed.ll.B.2.d. Open Tall Alder-Willow ShrubDescription-These communities have an opencanopy (25 to 75 percent cover) of tall shrubs(1.5 meters [5 ft] or taller) codominated byalder and willow (fig. 42). Common dominantsinclude Alnus crispa, A. sinuafa, Salk lanata,S. glauca, S. planifolia, and S. barclayi. Atsites below tree line, occasional trees mightovertop the shrub canopy, but these provideless than 10 percent cover. Low shrubs, suchas Betula glandulosa, Ledum decumbens,and Vaccinium uliginosum, are common.Calamagrostis canadensis may be abundant.Carex bigelowii may be abundant at tree linesites, and Sphagnum spp. may dominate theground layer on cold, moist sites.Distribution and site characteristics-Opentall alder-willow shrub communities have beenreported from flood plains, gentle slopes, andFigure 4 24pen fall alder-willow shrub ofAlnus tenuiiolia, Salix alaxensis, S. interior,and S. brachycarpa on a river flood plain ininterior Alaskasteep north slopes near and above tree line in interior, northern, and southwesternAlaska. Soils may be moderately well-drained loams on lowland sites or stonylithosols with thick organic mats on alpine north slopes. Permafrost may be presentat some sites.Successional status-In the generally forested part of ihe State, many of thesestands will be replaced by forest vegetation. Above and beyond the trees, thesecommunities may be a topoedaphic climax on terrace edges and steep slopes.Elsewhere they may become progressively shorter amd more open, eventuallyto be replaced by dwarf shrub-tussock tundra or wet sedge meadow.Closely related types-These communities resemble closed tall alder-willow andopen low alder-willow communities but have less than 75 percent cover and anaverage canopy height of 1.5 meters (5 ft) or more. They also resemble some opentall shrub swamp Communities but are drier, without standing water.Photographs-Figure 42, this publication.Primary references-Viereck 1963, Wibbenmeyer and others 1982121