The Alaska Vegetation Classification - Alaska Geobotany Center ...

Oxyfropis nigrescens, Hierochlog alpina, and Carex spp. but these generally providelittle cover. Mosses are commonly intertwined in the mat of ericaceous shrubs or, inthe case of Rhacomitriumspp., occur as distinct polsters. Moss species reportedinclude Dicranum spp. and Rhacomitrium lanuginosum. Tornenfhypnum nitens andHylocorniurn splendens probably also are common on many sites. Fruticose lichensmay be abundant. Common species include Cladina stellaris, C. rangiferina,C. arbuscula, Cetraria cucullafa, and Stereocaulon tornentosum. Trees generallyare absent and never provide more than 10 percent cover. Shrubs taller than20 centimeters (8 in) (and shrub species normally taller than 20 centimeters 18 in],such as Betula spp., Salixglauca, and S. planifolia) are absent or provide less than25 percent cover. The mat of shrubs, mosses, and lichens commonly provides nearlycomplete vegetative cover, although open stands are present on exposed sites.Distribution and site characteristics-Bearberry dwarf shrub tundra communitiesoccupy alpine areas of interior, northern, and western Alaska, possibly being mostcommon in the west. They occupy shallow, rocky, well-drained soils on slopes andwindswept ridges that are not as exposed as those supporting dryas tundra communities.Permafrost is at least 50 centimeters (20 in) deep and usually deeper.Successional status-Successional relations are mostly unknown. Sometimes thesecommunities occur on slopes between low scrub communities (such as mesic shrubbirch-ericaceous shrub) and dryas communities. Bearberry dwarf shwb tundra communitiesseem to be stable over long periods. There may be a trend for shrub birchto establish and become more important as soil development proceeds and asexposure to wind decreases.Closely related types-Bearberry tundra is closely related to vaccinium tundra and,in some cases, to crowberry tundra. Assigning stands to these units can becomevery arbitrary. Bearberry is more abundant in bearberry tundra than in the otherericaceous scrub tundras. Some dry windswept stands of bearberry tundra may besimilar to some of the dryas-dominated communities but have less dryas and morebearberry. Bearberry tundra also may be similar to some dwarf willow scrub tundracommunities but have more bearberry and less willow. Some bearberry stands mayresemble some open low shrub communities, such as mesic shrub birch-ericaceousshrub or open low willow, but lack significant quantities of shrub birch or erectwillows. Moist bearberry stands may resemble ericaceous scrub bogs but lacksphagnum and peat-forming sedges and generally occur on drier sites. They alsomay resemble mixed shrub-sedge tussock tundra but lack tussocks.Photographs-Racine and Anderson 1979, figure 13.Primary references-Hanson 1953, Jorgenson 1984, Racine and Anderson 1979,Webber and others 1978.Communities-Arctostaphylos alpina-Vaccinium vifis-idaea (Hanson 1953).Arctosfapbylos alpina-Rhododendron camtschaticum (Pegau 1968). Afctostapbylosrubra-Cladina stellaris (Webber and others 1978). Arctostaphylos alpina-Vacciniumspp.-Empetrum nigrum-Cassiope fefragona-lichens (Jorgenson 1984). Arctostaphylosalpina-Vaccinium uliginosum-Dicranum spp.-Rhacomitrium lanuginosum (Jorgenson1984). Arcfosfophylos alpina-Carex bigelowii (Racine and Anderson 1979).151