The Alaska Vegetation Classification - Alaska Geobotany Center ...

Figure 460pen low mesic shrubbirch-ericaceous shrub tundra withBetula glandulosa, Ledurn decurnbens.Vaccinium uliginosum, and Vaacciniumviris-idaea near tree line in the AlaskaRange in interior AlaskaDistribution and slte characteristics-Mesic shrub birch-ericaceous shrub communitiesoccupy extensive areas of mesic slopes in the Alaska Range, in alpine areas ofinterior and south-central Alaska, and in northern and western Alaska. These communitiescan develop on sites with a wide variety of moisture, temperature, and edaphicconditions. The soil is generally mineral with a well-decomposed organic layer 5 to30 centimeters (2 to 12) thick. Much mineral material is admixed into the base of theorganic layer. Silt loams or stony silt loams are common. Soil reaction is usuallysomewhat acidic; pH 4.5 to 6.0 is fairly typical. Permafrost is generally present butusually at least 50 centimeters (20 in) below the surface.Successlonal status-Many of these communities appear to be stable and tochange little over time. Some may develop on burned-over spruce forests andwoodlands near tree line (Pegau 1972); these stands may be slowly reverting toforest. Mesic shrub birch-ericaceous communities tend to grade into shrub-tussockcommunities as moisture increases, into shrub birch-ericaceous shrub bogs asmoisture increases on thick peat deposits, and into dwarf shrub (mat and cushion)fellfield communities as moisture decreases and wind exposure increases.Closely related types-Mesic shrub birch-ericaceous shrub communities are similarto shrub birch-ericaceous bog communities, but lack hydrophytic sedges (such asCarex aquafilis, C. pluriflofa. and Eriophorum angusfifolium) and Sphagnum spp.Fesfuca altaica, present in many of the mesic communities is absent from the bogcommunities. Mesic birch-ericaceous communities also are similar to some mixedshrub-sedge tussock communities but lack tussock-forming sedges. At the otherextreme, some communities resemble dwalf shrub (mat and cushion) communitiesbut have abundant birch and usually are not as windswept and unproductive. Theyalso are similar to open tall birch shrub communities but are dominated by lowshrubs (generally 0.2 to 1.5 meters [E in to 5 ft] tall). They are similar to closed lowshrub birch communities but have an open canopy (25 to 75 percent cover) andfrequently a more diverse understory. Some white spruce woodlands are similar tomesic birch-ericaceous shrub communities but have at least 10 percent tree cover.Some ericaceous dwarf shrub and dryas dwarf shrub communities are similar lomesic shrub birch-ericaceous shrub communities but lack significant cover of shrubbirch.Photographs-Viereck 1966, figure 7; figure 46, this publication.132.