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Community Field Guide

Scientific Name:
Abies lasiocarpa / Carex geyeri Forest

Common Name:
Subalpine fir / elk sedge Forest

Community Description

This is a broadly distributed large patch to matrix association occurring from eastern Washington and Oregon to southern Idaho associated with, at least in the northern portion of its range, rain shadow effects and representing the driest of Abies lasiocarpa series habitats. In most regions it evidences a 1,200 to 2,500 foot elevation range; its overall observed elevation range is from 6,500 (Montana) to 9,800 feet (southern Utah). It occurs on a wide variety of parent materials though in its core area of central Idaho, granitics, other intrusive volcanics and extrusive volcanics (rhyolite, basalt) are the predominant substrates. Abies lasiocarpa is the indicated climax dominant of this potential natural vegetation type. Important seral trees that vary by region, and that are long persisting in this habitat include Pinus contorta, Pseudotsuga menziesii, and Pinus albicaulis. The undergrowth of this association, in gross aspect, is like that of Abies lasiocarpa / Calamagrostis rubescens with a luxuriant sward of graminoids, in this case dominated by Carex geyeri and having a trace of Calamagrostis rubescens. Shrubs are very scattered, if present, and the forb cover and diversity varies by region and by phase.

Apparently through the mechanism of factor compensation, this association exhibits a shift in environmental parameters from south facing slopes at lower to mid-elevations in Montana to primarily north- and northeast-facing slopes in southern Utah. In central Idaho, where the type is most abundant, it evidences no slope aspect or inclination preferences and it exhibits its broadest elevation range, 6,200 to 9,200 feet. Though the type occurs on limestone in Montana, it appears much more extensive on igneous substrates, whether in the Pacific Northwest or in its southern distribution. It is found exclusively on rhyolite or various forms of extrusive igneous in the Centennial Range and is also reported (Steele et al. 1983, Steele et al. 1981, and Alexander et al. 1986) from volcanic substrates that weather to other than fine-textured substrates. This type often grades to Pseudotsuga menziesii / Carex geyeri or Calamagrostis rubescens on drier (lower elevation) sites, to Abies lasiocarpa / Thalictrum occidentale or Abies lasiocarpa / Arnica cordifolia forest on moister exposures, or to Abies lasiocarpa / Vaccinium scoparium and Abies lasiocarpa / Ribes montigenum on colder/moister exposures.

Sampled stands include mid-seral to late-mature and thus encompass much variability in structure and composition. Exclusive of Colorado and Utah, the lower elevation examples of this type are dominated throughout their existence by Pseudotsuga menziesii and Pinus contorta. In Utah and Colorado, Populus tremuloides is the dominant seral tree with Abies lasiocarpa and Picea engelmannii only slowly establishing. Long-lived Pinus contorta may also form nearly pure stands on this type, but it usually occurs mixed with Pseudotsuga. Stands from higher elevations often have Abies lasiocarpa establishing immediately following disturbance but Pinus contorta is still a major component. Pinus albicaulis is a major long-lived seral component at the type’s highest elevations in central Idaho and the greater Yellowstone country. Throughout the type’s occurrence Picea engelmannii is conspicuously poorly represented, even in near climax conditions. Recognizing forb-rich conditions as conveying a higher moisture status and belonging to preferentially recognized plant associations, the undergrowth conditions in an Abies lasiocarpa / Carex geyeri forest are typified by the dominance of Carex geyeri with only scattered forbs. In open stands Carex geyeri may approach a sward-like coverage. Forbs commonly present include Thalictrum occidentale, Astragalus miser, Fragaria virginiana, Symphyotrichum foliaceum (=Aster foliaceus) and Arnica cordifolia. In early- to mid-seral conditions Shepherdia canadensis and Juniperus communis are usually well represented.

This is a broadly distributed association found from eastern Washington and Oregon in the rain shadow of the Cascades and again in Montana east of the Continental Divide and extends southward to south-central Wyoming and north-central Colorado and at its southern extreme is an incidental type of southern Utah, though its greatest extent in any regional landscape is ostensibly that of central Idaho.

Abies lasiocarpa is slow to reestablish following disturbance and Picea engelmannii seldom establishes in this type. In central Idaho, at the highest elevations of the type, Pinus albicaulis is the dominant and long-persisting seral species and apparently functions as a nurse tree facilitating colonization by other tree species.

Global Rank: G5 State Rank: S3

Community References


99-11-16 / S. V. Cooper, MTNHP

Alexander 1986, Bourgeron and Engelking 1994, Driscoll et al. 1984, Hess and Alexander 1986, Johnson and Clausnitzer 1992, Johnston 1987, Komarkova 1982, Komarkova et al. 1988b, Pfister et al. 1977, Steele et al. 1981, Steele et al. 1983, Terwilliger et al. 1979a, Wasser and Hess 1982, Youngblood and Mauk 1985

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This information is from the:
Montana Natural Heritage Program
Montana State Library--Natural Resource Information System
1515 East Sixth Ave., Helena, MT 59620-1800
406 444-5354