The Alaska Vegetation Classification - Alaska Geobotany Center ...

A well-developed tall shrub layer, consisting primarily of Befula glandulosa and Ahuscrispa, is characteristically present. A low shrub layer occupies the spaces betweenthe tall shnrbs and trees. Common low shrubs include Vaccinium uliginosum, V.vifis-idaea, Emperrum nigrum, and Ledurn groenlandicum. The herb layer is sparseand consists predominantly of Calamagrosfis canadensis and Carex bigelowii. Acontinuous or nearly continuous layer of mosses is dominated by Pleuroziumschreberi, Hylocomium splendens, and Polyfrichumspp. Foliose and fruticose lichenssuch as Cladonia spp., Cladina spp., Cetraria spp., and Peltigera spp. contribute asubstantial amount of cover to the moss layer.Distribution and site characteristics-Black spruce-white spruce woodlands arefound near tree line in interior, western, and south-central Alaska. Near Fairbanks,they are reported on east- and west-facing slopes above 700 meters (2,300 it). Theyoften occupy the coldest sites capable of supporting forest vegetation. The poorlydeveloped, stony, mesic to dry soils are shallow and may lie directly on fracturedbedrock. A 0- to 3-centimeter-thick (0- to 12-in-thick) organic layer covers the soilsurface. Permafrost is absent or fairly deep.Successional status-These woodlands appear to be climax but probably are in avery delicate balance with climate. A series of warm, moist summers might allowmany seedlings to establish, which would lead to a more closed canopy in a fewdecades. On the other hand, some catastrophically distutbed stands may not returnto a forested condition at all.Closely related types-Densely treed stands resemble open black spruce-whitespruce forest but have less than 25 percent tree cover. Very open stands grade intoopen low mesic shrub birch-ericaceous shrub scrub communities with scatteredspruce. Depending on the relative proportions of the two spruce species present,these communities may resemble either black spruce woodland or white sprucewoodland but have significant cover of both species.Photographs-Foote 1983, figure 13.Primary references-Foote 1983, Viereck and others 1983.Communities-Picea mariana-P. glauca/Befulag/andulosalfeathermosses (Viereck1979). Picea glauca-P. marianallichens (Foote 1983). Picea mariana-P. g/auca/Alnuscrispa-Betula glandulosa/Pleurozium schreberi (Jorgenson and others 1986, Viereckand others 1983). Picea mariana-P. glauca/Rubus chamaemorus-Ledum decumbens-Vacciniumspp. (Craighead and others 1988)./.E. Broadleaf ForestBroadleaf forest communities have at least 75 percent of tree canopy coveragecontributed by broadleaf tree species. Alaska broadleaf tree species are Alnusrubra, Befula papyrifera, Populus frichocarpa, P. balsamifera, and P. fremuloides.83