The Alaska Vegetation Classification - Alaska Geobotany Center ...

Figure lS0pen needleleaf forest ofwhite spruce with a shrub layer ofAhus crisp, A. tenuiiolia, and Rosaacicularis; the low subshrub Vacciniumvitis-idaea on the forest floor; and athick ieathermoss layer an the floodplain of the Tanana River in interiorAlaska.Phases-On moist lowland sites in the Yukon Flats, willows (particularly Salixbebbiana) may replace Betula glandulosa as the dominant shrub. The groundcover may be dominated by foliose lichens such as Parmelia spp. and Pelfigeraspp. Feathermosses are important associates.Sphagnum replaces feathermosses in the ground layer on many sites in southwesternAlaska because of the abundant precipitation and poor soil drainage.Distribution and site characteristics-Open white spruce communities arecommon on well-drained timberline sites and occasionally occur on certainsomewhat poorly drained to well-drained lowland sites. They are found throughoutinterior, northwest, southwest, and south-central Alaska. Soils are commonlyCryaquepts, Cryochrepts, or Cryofluvents and range from somewhat acid to almostbasic. Permafrost may be present or absent; but if present, it is generally deeperthan 70 centimeters (30 in). Brooks Range tree-line stands commonly are on streamand river terraces or alluvial fans where silts overlie alluvial gravels.Successional status-Most stands appear to be stable and some are very old(up to 250 years). Tree-line stands, in particular, are probably climax. Successionalsequences after disturbance are unknown. Some tree-line stands would remainunforested for long periods of time if severely disturbed.Closely related types-These communities are similar to closed white spruce andwhite spruce woodland Communities but differ in the amount of tree cover present(25 to 60 percent for open white spruce communities). Some stands may be similarto open black spruce-white spruce or open white spruce-paper birch communities,but have less black spruce or paper birch. Some stands are similar to certain scrubcommunities but have at least 25 percent tree cover.Photographs-Figure 15, this publication.Primary references-Viereck 1970b, 1979; Yarie 1983.73