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 <i>Dryas octopetala</i>-dominated dwarf-shrublands. It occurs predominantly in alpine environments (well above treeline); actual elevations vary from 3370 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.<br><br>A mat of the dwarf-shrub <i>Dryas octopetala</i> 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 <i>Salix arctica, Dasiphora fruticosa ssp. floribunda (= Pentaphylloides floribunda, = Potentilla fruticosa), Arctostaphylos uva-ursi, Juniperus communis</i>, and <i>Salix reticulata</i>. 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. <i>Carex rupestris</i> 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 <i>Carex nardina, Calamagrostis purpurascens, Calamagrostis koelerioides, Festuca brachyphylla, Poa alpina</i>, and <i>Trisetum spicatum</i>. Typically the forb component does not exceed 10% cover, and that of individual forbs does not exceed 5%; those with highest constancy include <i>Minuartia obtusiloba (= Arenaria obtusiloba), Myosotis asiatica, Geum rossii, Artemisia scopulorum, Saxifraga bronchialis, Silene acaulis, Oxytropis campestris, Rhodiola rosea (= Sedum roseum), Solidago multiradiata, Potentilla diversifolia</i>, and <i>Smelowskia calycina</i>. Cover of mosses and lichens is very low.
Accession Code:
VB.CC.34507.CEGL001892
Plot-observations of this Community Concept:
0
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