Name:
Dryas octopetala - Carex rupestris Dwarf-shrub Herbaceous Vegetation
Reference:
Western Ecology Working Group of...
Description:
This alpine fell-field association is found throughout Colorado's Rocky Mountains, and in western and central Montana north into Alberta. This vegetation type represents the drier, mostly subxeric to submesic, occurrences of Dryas octopetala-dominated dwarf-shrublands. It occurs predominantly in alpine environments (well above treeline); actual elevations vary from 3600 to 3900 m in the Colorado alpine to between 1700 and 2400 m in northwestern Montana. Typical terrain is moderately to steeply sloping and all aspects are represented. The determining environmental parameter appears to be wind-scouring with sites blown snow-free in winter. Soils are very poorly developed and well- to rapidly drained. The association occurs on a wide variety of parent materials, though typically on residual and colluvial landforms. Where not protected by a dwarf-shrub mat, ground surfaces are comprised of 5 to 60% exposed gravel, cobble and to a much lesser degree soil; litter can only accumulate immediately under the protection of the dwarf-shrub cover. A mat of the dwarf-shrub Dryas octopetala dominates the visual aspect, with variable cover ranging from 10% to 80%. Usually mats occur in relatively evenly spaced windrows oriented perpendicular to the prevailing wind or along the edges of stepped terracettes. Other dwarf-shrubs include Salix arctica, Dasiphora fruticosa ssp. floribunda (= Pentaphylloides floribunda, = Potentilla fruticosa), Arctostaphylos uva-ursi, Juniperus communis, and Salix reticulata. Of the herbaceous component, graminoids generally have greater cover than forbs, a condition which is presumed to indicate the relatively xeric nature of the type. Carex rupestris has high constancy and occasionally is the dominant graminoid, but in Glacier National Park stands there is no one dominant graminoid, only a variable suite of xeric-adapted species, including Carex nardina, Calamagrostis purpurascens, Calamagrostis koelerioides, Festuca brachyphylla, Poa alpina, and Trisetum spicatum. Typically the forb component does not exceed 10% cover, and that of individual forbs does not exceed 5%; those with highest constancy include Minuartia obtusiloba (= Arenaria obtusiloba), Myosotis asiatica, Geum rossii, Artemisia scopulorum, Saxifraga bronchialis, Silene acaulis, Oxytropis campestris, Rhodiola rosea (= Sedum roseum), Solidago multiradiata, Potentilla diversifolia, and Smelowskia calycina. Cover of mosses and lichens is very low.
Accession Code:
VB.CC.26538.DRYASOCTOPETALA
Plot-observations of this Community Concept:
0
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