Abies bifolia

A. Murray 1863

Common names

Rocky Mountain alpine fir, Rocky Mountain subalpine fir, corkbark fir (Hunt 1993).

Taxonomic notes

Syn: Abies subalpina Engelmann. Since the 1920's, nearly all of the literature includes Abies bifolia in synonymy under A. lasiocarpa. However, Abies bifolia is distinct from A. lasiocarpa in chemical tests on wood, lack of crystals in the ray parenchyma, lack of lasiocarpenonol, and distinct terpene patterns. Abies bifolia also tends to have slightly shorter and fewer prominently notched leaves than A. lasiocarpa. The two are clearly separated by the color of their periderm and by the shape of their basal bud scales. These firs may be more distinct than the pairs A. balsamea-A. fraseri and A. procera-A. magnifica. As with these other pairs, introgression occurs in the zone of range overlap. A north-south transect from south central Yukon to northern Washington contains introgressed trees having characteristics of both A. lasiocarpa and A. bifolia. These trees could be called interior subalpine fir, i.e., A. bifolia × lasiocarpa. Both A. lasiocarpa and A. bifolia warrant comparative morphologic and genetic studies to clarify the relationship between the two species (Hunt 1993).

"Isolated southern populations of Abies bifolia may also have unique characteristics. The taxonomy of corkbark fir, treated by some as A. lasiocarpa var. arizonica (Merriam) Lemmon, is uncertain. This taxon should probably be a segregate of A. bifolia, not A. lasiocarpa, a disposition that requires a thorough morphologic and chemical reappraisal, especially since the work of E.Zavarin et al. (1970) suggested that populations south of Wyoming may have unique terpene patterns. In north central Alberta, A. bifolia introgresses with A. balsamea (Hunt and von Rudloff 1974; Moss 1953)" (Hunt 1993).

Description

Tree: Up to 30 m tall and 45 cm dbh with a spire-like crown (Hunt 1993).
Bark: Gray, thin, smooth, becoming furrowed and scaly with age. Towards the southern end of the range, the 'corkbark fir' has thickened, 'corky' bark that may be dark grey, deeply furrowed (Hunt 1993).
Branches: Diverge from the trunk at right angles (Hunt 1993).
Shoots: Twigs stout, stiff, opposite to whorled, grayish with sparse light brown pubescence; fresh leaf scars expose a light brown periderm (Hunt 1993).
Leaves: Spiraled and turned upward, flexible, apex slightly notched to rounded, 11-25 × 1.25-1.5 mm; cross section flat with an adaxial groove; odor similar to camphor; lower surface with 3-5 lines of stomata on each side of midrib; upper surface light green to bluish green, usually glaucous, with 3-6 rows of stomata at midleaf; stomatal rows are usually continuous to leaf base and are more numerous toward leaf apex; resin canals are large, ± medial. Buds are exposed, brown, globose, small, resinous, with a rounded apex; basal scales are long, narrow, triangular to spathulate, and glabrous, margins are entire to rarely crenate with a sharp-pointed or rounded apex. Cotyledons 3-6 (Hunt 1993).
Cones: Cylindric with a rounded apex, sessile, 5-10 × 3-3.5 cm, dark purple-blue to grayish purple (Hunt 1993).
Cone scales: Densely pubescent; ca. 1.5 × 2.5 cm, with included bracts (Hunt 1993).
Pollen cones: Purplish at time of pollination (Hunt 1993).
Seeds: Brown, 5-7 × 2-3 mm, with a grayish brown wing about 1.5 times as long as the nut (Hunt 1993).

Range

Canada: in southern Yukon Territory, the Northwest Territories, the Rocky Mountains of Alberta, and the interior plateaus and Rockies of British Columbia. USA: Washington, Oregon, Idaho, Montana, Wyoming, Colorado, New Mexico, Arizona, Utah and Nevada at 600-3700 m in continental subalpine conifer forests of the Rocky Mountain area, the Intermountain Ranges, and the Wallowas of eastern OR (Peattie 1950, Hunt 1993). It is found growing to the alpine treeline in most of its range. In most of the Rocky Mountains, it forms a major forest type with Picea engelmannii (Little 1980).

Big tree

Oldest

Sampled one tree in the Medicine Bow Mountains, WY, aged 494 years with over 90% of the age verified by cross-dating (Earle 1993).

Dendrochronology

Numerous studies of forest age structure have been conducted, some of which (e.g., Earle (1993)) have used dendrochronological methods.

Ethnobotany

Observations

Remarks

Citations

See also

Burns & Honkala 1990 (as A. lasiocarpa).