The Alaska Vegetation Classification - Alaska Geobotany Center ...

III.C.1.6. Dly BryophyteFigure ? L A dry bryophyte community of Rhacomifriumlanuginosum on coarse gravel outwash in a coastal areaof south-central Alaska.Description-These are communities dominated by bryophytes, usually mossessuch as Rhacomitrium spp., Grimmia apocarpum, and Andreaea rupesfris (fig. 74).Lichens may be common. Vascular plants are rare or absent. Cover usually is sparse.Distribution and site characteristics-Dry bryophyte communities are fairly rareand have been reported primarily from the Aleutian Islands, though they probably aremore widespread. They are most common on windswept coarse mineral substrates,including sand dunes and gravelly slopes. These are sparsely vegetated types withmuch exposed substrate.Moss mound communities also are included within this unit. These well-vegetatedmicrocommunities occupy a substrate of dead mosses. Some mounds consist ofmosses throughout, others have rock cores. Substrates are generally acidic (pH 5to 7).Successional status-The windswept barren dry bryophyte communities are anearly successional stage but may persist indefinitely because of wind deflation of soilmaterials. Moss mounds are temporary features; eventually growth ceases and themounds start to break apart, finally becoming indistinguishable from the surroundingvegetation.Closely related types-Dry bryophyte communities are similar to wet bryophytecommunities but are dominated by different species and occupy drier sites. The drywindswept bryophyte types also are similar to some lichen communities but aredcminated by bryophytes instead of lichens. Both resemble some of the mostsparsely vegetated open dwarf shrub (mat and cushion) communities, but the latterhave more vascular plants, particularly shrubs or subshrubs.Photographs-Shacklette and others 1969, figure 10; figure 74, this publication.Primary reference-Shacklette and others 1969.Communities-Rhacomifrium lanuginosum-Dicranum spp. (Shacklette and others1969). Rhacomifrium lanuginosum-Grimmia apocarpa-Ulofa phyllanfha (Shackletteand others 1969). Andreaea rupesfris-Grimmia apocarpa-Rhacomifrium lanuginosum(Shacklette and others 1969).201