The Alaska Vegetation Classification - Alaska Geobotany Center ...

Distribution and site characterlstlcs-Open hemlock-spruce communities arecommonly found on slopes of less than a 30-percent gradient from midelevationto lower elevations. Common landforms supporting these communities includefootslopes, mountainside benches, and concave slopes. Thick organic soils andsurface and subsurface water flow characterize sites where these communitiesare found. Sites with understories dominated by Oplopanax hofridus have a greaterwater runoff than those where Lysichiton americanum dominates. Soils are deep,poorly drained, and weakly developed and have a thick surface organic layer 0115 to 30 centimeters (6 to 12 in).Successlonal status-Successional relations are largely unknown. Coniferseedlings do not seem to grow well on the poorly drained organic soils.Closely related types-These communities are similar to closed western hemlock-Sitka spruce communities, the closed Sitka spruce-western hemlock communitiesand some closed western hemlock communities but canopy cover averages less than60 percent. They also are similar to some open mixed-conifer communities, but aremore strongly dominated by western hemlock and Sitka spruce.Photographs-Figure 12, this publication.Primary referent-Martin and others 1985.Communltles-Tsuga heterophylla-(Picea sitchensis)(see footnote 1)lOplopanaxhorridus/Lysichiton americanum (Martin and others 1985).bA.2.c. open Mountain Hemlock ForestDescrlptlon-Mountain hemlock dominates the overstoty of these forest communitiesby providing 15 to 60 percent cover (fig. 13). Overstory trees average 9 to21 meters (30 to 70 ft) in height and 25 to 50 centimeters (10 to 20 in) in d.b.h.Mountain hemlock seedlings are generally common to abundant. Other coniferspecies, particularly Sitka spruce, may occur occasionally but are not important.A well-developed shrub layer is present and is dominated by some combination ofVaccinium alaskaense, V. ovalifolium, Menziesia ferruginea, and Cladofhamnuspyfolifolia. These shrubs grow 1 to 1.5 meters (3 to 5 It) tall and provide 50 to 70percent cover. In some communities, a layer of low alpine shrubs dominated bysome combination of Cassiope mefltensiana, C. stelleriana, Phyllodoce aleutica spp.glanduliflora. and Luetkea pecrinata is present.Figure 1Mpen needleleaf forestof mountain hemlock with understoryof Vaccinium spp. and Cassiopemettensiana in southeastern Alaska.(Photcgraph munsry Jon Manin.)70