Name:
Larix occidentalis / Vaccinium caespitosum / Clintonia uniflora Forest
Reference:
Western Ecology Working Group of...
Description:
This mesic, small- to large-patch forested community is a minor type found from northwestern Montana (west of the Continental Divide) westward across northern Idaho to northeastern Washington as far west as the Okanogan Plateau; it southern extent is central Idaho's Seven Devils and southern Batholith regions. In both northeastern Washington and western Montana, it is found at elevations predominantly between 915 to 1220 m (3000-4000 feet) with extremes from 680 to 1400 m (2230-4590 feet); at its southern extent it is found between 1400 and 1675 m (4600-5500 feet). This association typically is found on lower elevation benchlands and gentle lower slopes of low gradient, areas that would be expected to be frosty or where cold-air ponding occurs with a relatively high frequency. Daytime temperatures are warm, which results in a strong diurnal contrast that is apparently limiting to tree species that potentially are climax dominants. Sites are confined to well-drained glacial till and outwash deposits or similarly derived relatively coarse-textured sediments (mostly fine sandy loams to loams in texture) that frequently have an appreciable gravel content. Soil reactions vary from acidic to very acidic.The upper canopy is relatively open (ranging from 40 to 70% canopy cover with extremes to 20%) and dominated by Larix occidentalis with minor contributions of Pinus contorta and Pseudotsuga menziesii. Pseudotsuga characteristically has the greatest understory cover, followed by Abies lasiocarpa, Picea engelmannii, or Picea engelmannii X glauca hybrids. With the exception of Amelanchier alnifolia, tall shrubs are not represented, and while a diversity of short shrubs (Shepherdia canadensis, Spiraea betulifolia, Lonicera utahensis, Paxistima myrsinites, Vaccinium membranaceum) are consistently present, their aggregate cover does not often exceed 20%. Besides containing two of the three undergrowth indicator species, Vaccinium caespitosum and Arctostaphylos uva-ursi, the dwarf-shrub layer in combination with consistently high Calamagrostis rubescens cover (in excess of 30%) gives modal stands their prevailing aspect of nearly continuous cover; other dwarf-shrubs of moderate to high constancy and highly variable cover include Linnaea borealis, Mahonia repens or Mahonia aquifolium (depending on locality), Chimaphila umbellata, Vaccinium scoparium, and Vaccinium myrtillus. Of two forbs, Clintonia uniflora and Cornus canadensis, indicative of this association's relatively mesic status (as compared to say Larix occidentalis / Vaccinium caespitosum) only Clintonia is also 100% constant and used as an indicator. Forbs are usually a negligible component with only Arnica cordifolia, Fragaria spp., Orthilia secunda (= Pyrola secunda), Lupinus sericeus or Lupinus argenteus (depending on locality), Hieracium albiflorum, and Maianthemum racemosum exhibiting moderate to high constancy and a combined cover seldom exceeding 10%.
Accession Code:
VB.CC.28080.LARIXOCCIDENTAL
Plot-observations of this Community Concept:
0
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