The Alaska Vegetation Classification - Alaska Geobotany Center ...

Distribution and site characteristics-Western hemlock-Alaska-cedar communitiesoccur at all elevations below the subalpine zone in southeastern Alaska. They primarilyare found on stable mountain slopes, hillslopes, and footslopes where drainageor root growth are impeded. Erosive surface or subsurface waterflow does notoccur. Microtopography is sometimes characterized by mounds and depressions.Lysichiton americanurn is usually restricted to depressions.Soils are mineral and may be either deep and somewhat poorly drained or shallowand well drained. The most common restricting layers of shallow soils are bedrock,compact till, and compact ash. Soils of localized depressions generally have a thickorganic horizon.Successlonal status-These communities are thought to be climax. When sitessupporting these communities are logged, they tend to come back to Vacciniurn spp.and Menziesia ferruginea if the soil is not seriously disturbed, and to Alms sinuataand Rubus spectabilis if the soil has been seriously disturbed.Closely related types-Closed western hemlock-Alaska-cedar communities aresimilar to some western hemlock stands but have more yellow-cedar. They alsomay be similar to some open mixed conifer stands but have slightly greater treecover and fewer dominant tree species.Primary referenceMartin and others 1985.Communities-Tsuga heterophylla-Chamaecyparis nootkatensis/Vacciniurn spp.(Martin and others 1985). Tsuga heterophylla-Chamaecyparis nootkatensidVaccinium spp./Lysichiton arneficanurn (Martin and others 1985). Tsugaheterophylla-Chamaecyparis nootkatensis/Vaccinirn spp./Oplopanax horridus(DeMeo and others 1989).LA. i.f. Closed Mountain Hemlock ForestDescrlption4ountain hemlock (Tsuga mertensiana) dominates the overstory(fig. 6). Sitka spruce may be present but occupies less than 10 percent of the overstory.Western hemlock may occur in the transition zone at the lower elevationalextent of these communities. Overstory cover is greater than 60 percent, usuallynearer 70 or 75 percent. Mature mountain hemlock trees range from 18 to 25 meters(55 to 75 ft) tall and from 38 to 50 centimeters (15 to 20 in) d.b.h.A well-developed shrub layer about 1 meter (3 ft) high and providing about 65 percentcover is dominated by Vacciniurn spp. Common herbs and ferns include Cornuscanadensis, Rubus pedatus, Coptis aspleniifolia, Blechnum spicant, and Faufiacrista-galli.Dlstrlbution and site characteristics-Mountain hemlock communities occurmost often on upper mountain slopes. They also occur to a minor extent at lowerelevations in frost pockets and on steep, norlh-facing mountain slopes. Typicalelevations range from 400 to 500 meters (1,300 to 1,600 ft). Slope gradients aresteep (on the order of 45 to 60 percent). Soils generally are shallow, poorly to welldrained, and weakly to well developed." .