Abies lasiocarpa

(Hooker) Nuttall 1849

Common names

Subalpine fir, alpine fir, balsam fir, white fir, mountain balsam fir, white balsam, western balsam fir, Rocky Mountain fir, and pino real blanco de las sierras (Burns and Honkala 1990), sapin concolore (Hunt 1993). Subsp. bifolia is sometimes called the Rocky Mountain subalpine fir, although western subalpine fir would be more accurate, and var. arizonica is commonly called corkbark fir or alamo de la sierra (Burns and Honkala 1990).

Taxonomic notes

There are three distinct types of Abies lasiocarpa, which are here described as varieties. One is the the formally recognized variety A. lasiocarpa var. arizonica (Merriam) Lemmon, the corkbark fir, native to the southern Rocky Mountains. A second, native to most of the rest of the continental United States but penetrating Canada as far as the Yukon, is here called the western subalpine fir. It has been described as A. bifolia A. Murray and as A. lasiocarpa subsp. bifolia (A. Murray) Silba 2008. Most conifer biologists have chosen not to recognize the taxon as a separate species, because only very minor characters distinguish it from typical A. lasiocarpa. There is some agreement that it probably constitutes a separate variety, but has not yet been formally described as such. It is here referred to as A. lasiocarpa subsp. bifolia. The third and type variety, A. lasiocarpa var. lasiocarpa, was described from southeast Alaska and is found mainly in Alaska, Yukon, British Columbia, and Alberta, with some individuals found farther south in the northern Rockies and the Cascade and Olympic Mountains of Washington.

Subsp. bifolia is distinct from var. lasiocarpa in chemical tests on wood, lack of crystals in the ray parenchyma, lack of lasiocarpenonol, and distinct terpene patterns. Subsp. bifolia also tends to have slightly shorter and fewer prominently notched leaves than var. lasiocarpa. The two are clearly separated by the color of their periderm and by the shape of their basal bud scales. Both var. lasiocarpa and subsp. bifolia warrant comparative morphologic and genetic studies to clarify the relationship between the two taxa (Hunt 1993). Discrimination between subsp. bifolia and var. arizonica is more ambiguous, but is primarily based on the thickened, 'corky' bark of var. arizonica that may also be dark grey and deeply furrowed.

Through central British Columbia and northern Washington, the type variety introgresses with subsp. bifolia. These trees may have morphologic features resembling either taxon and may have intermediate terpene patterns; they are best classified as interior subalpine fir (Hunt 1993). In north central Alberta, subsp. bifolia introgresses with A. balsamea (Hunt and von Rudloff 1974, Moss 1953, both cited by Hunt 1993). At the southern end of its range, var. lasiocarpa possibly hybridizes with A. procera, but the taxa are normally separated by habitat and elevation. Var. lasiocarpa shares with A. procera a red periderm, crystals in the ray parenchyma, and reflexed tips of the bracts, features not shared with subsp. bifolia (Hunt 1993). A. lasiocarpa (var. lasiocarpa and subsp. bifolia) and A. amabilis, although sympatric over a wide area, are separated by many morphologic features, and no hybrids have been found (Hunt 1993).

The only unique populations of var. lasiocarpa come from coastal Alaska (Heusser 1954, Harris 1965). They are found at lower elevations (0-900 m) and appear to be isolated with no reported introgression between them and the coastal mountain populations. The population on the Prince of Wales Island has distinct terpene patterns and needs morphological and developmental studies to see if these patterns contrast with neighboring populations (Hunt 1993). These populations might warrant treatment as a distinct variety or forma.

Synonymy:

For var. lasiocarpa, Pinus lasiocarpa Hooker 1838.

For subsp. bifolia, Abies bifolia A. Murray and Abies subalpina Engelmann.

Description

Trees to 50 m tall and 200 cm DBH, often much smaller due to growth in harsh environments; all varieties occur as krummholz at alpine elevations. Crown usually tall-conical, becoming somewhat flattened and irregular in old trees. Primary branches stiff, whorled at right angles to axis of a terete, monopodial trunk. Bark gray, thin, smooth, with resin blisters in young trees, becoming furrowed and scaly with age. Twigs stout, stiff, sunlit branchlets with uniform branching pattern, green-gray to light brown, sparse brown pubescence. Buds hidden by leaves or exposed, tan to dark brown, nearly globose, small, resinous, apex rounded; basal scales triangular to spathulate, glabrous or with a few trichomes at base, not resinous, margins entire dentate, apex acute to rounded. Leaves 11-31 × 1.25-2 mm, spiraled and turned upward, flexible; cross section flat, grooved on the upper surface; lower surface with 3-5 lines of stomata on each side of midrib; upper surface light green to blue-green, usually glaucous, with 3-6 rows of stomata at midleaf that are continuous to leaf base and more numerous toward leaf apex; resin canals large, ± medial; leaf apex notched to rounded. Cotyledons 3-6. Pollen cones at pollination ± purple to purple-green. Seed cones dark purple-blue to gray-purple with a rounded apex, sessile, 5-12 × 2-4 cm. Cone scales ca. 1.5 × 2.5 cm, densely pubescent; bracts included (specimens with exserted, reflexed bracts are insect infested). Seeds 5-7 × 2-3 mm, brown with a light brown wing about 1.5 times as long as the nut. 2n=24 (Hunt 1993 and pers. obs.).

The following characters serve to discriminate the varieties (Hunt 1993):

Var. lasiocarpa: Pulling off a few needles will show a red periderm on the fresh leaf scars (see photo at left). On foliar buds, the basal scales are equilaterally triangular with crenate or dentate margins. Leaves 18-31 mm × 1.5-2 mm; odor sharp (ß-phellandrene); lower surface with 4-5 stomatal rows on each side of midrib; upper surface blue-green, very glaucous, with 4-6 stomatal rows at midleaf.

Subsp. bifolia: Fresh leaf scars reveal a yellow or tan periderm. On foliar buds, the basal bud scales are long, narrow-triangular to spathulate with crenate to entire margins. Leaves 11-25 × 1.25-1.5 mm; odor similar to camphor; lower surface with 3-5 lines of stomata on each side of midrib; upper surface light green to blue-green, usually glaucous, with 3-6 rows of stomata at midleaf.

Var. arizonica: Has thickened, 'corky' bark that is white to grey and deeply furrowed, and has very glaucous foliage. In other respects it is like subsp. bifolia.

Range

Canada: Yukon, Northwest Territories, British Columbia, Alberta; United States: Washington, Oregon, California, Idaho, Montana, Wyoming, Colorado, New Mexico, Arizona, Utah and Nevada. See also Thompson et al. (1999).

Var. lasiocarpa occurs in Canada: S Yukon and the Coast Range of British Columbia; United States: The coast ranges of SE Alaska, Washington, Oregon, and California (Hunt 1993). My own observations at numerous sites in the Olympic and Cascade Mountains have indicated that nearly all of these trees are identifiable as subsp. bifolia. The most southerly trees of var. lasiocarpa that I have heard of were found at Sunrise on Mount Rainier in Washington. Typically found at 1100-2300 m elevation in coastal subalpine conifer forests (Peattie 1950), var. lasiocarpa grows to the alpine treeline in most of its range (Little 1980). Common associates include Abies amabilis, Pinus albicaulis and Tsuga mertensiana.

Subsp. bifolia occurs in Canada: S Yukon, Northwest Territories, Alberta, British Columbia; United States: Washington, Oregon, Idaho, Montana, Wyoming, Colorado, New Mexico, Arizona, Utah and Nevada at 600-3700 m in subalpine conifer forests (Peattie 1950, Hunt 1993). Although the range map shown at left identifies subsp. bifolia as exclusively an interior species, my own observations and those of professional acquaintances indicate that trees in the Cascade Mountains of Washington and Oregon, and the Olympic Mountains, are predominantly subsp. bifolia. Subsp. bifolia 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).

Var. arizonica occurs in United States: Arizona, Colorado and New Mexico, typically at elevations of 2400-3400 m, where it commonly grows with Picea engelmannii (Burns and Honkala 1990).

The lower photo at left shows a tree clump comprised exclusively of subsp. bifolia. Tree clumps such as these are common in subalpine areas and are the common feature of a phytogeographic type, the forest-tundra parkland. Many subalpine species occur in forest-tundra parkland, but it is an especially common setting for subalpine fir (including subsp. bifolia and var. lasiocarpa). Typically such parklands form in settings where heavy winter snowfall shortens the growing season and lowers soil temperature to the point where tree seedling establishment is impeded. Isolated trees may establish in such settings during intervals of warmer and/or drier climate, or sometimes they represent trees of other species. Solar radiation reflected from the isolated trees causes the snow around them to melt earlier in the season, creating a microsite with marginally better seedling establishment conditions. Over time a forest of seedlings grows up around the pioneer tree, forming a tree clump. Such clumps may persist as discrete units on the landscape for a thousand years or more until eradicated by fire or disease, or until climate and microsite changes transform the site into forest -- or tundra. See also Arno and Hammerly (1984).

Big tree

Largest: Diameter 204 cm, height 38.1 m, crown spread 8 m in 1992, at Cream Lake in Olympic National Park, WA (Van Pelt 1996). This tree has not to my knowledge been identified as to variety and could plausibly be either lasiocarpa or bifolia.

Tallest: Diameter 107 cm, height 52 m, crown spread 7 m in 1988; on the Icicle Creek Trail in the Alpine Lakes Wilderness of WA (Van Pelt 1996). This tree has not to my knowledge been identified to var. lasiocarpa or subsp. bifolia.

Var. arizonica: The largest is 33.8 m tall, 133 cm dbh, near Ruidoso, New Mexico.

Oldest

A tree in Yukon Territory with a crossdated age of 501 rings, reported by Luckman (2003; cited by RMTRR 2006). Based on its location, this tree was probably var. lasiocarpa.

I sampled one tree of subsp. bifolia in the Medicine Bow Mountains, Wyoming, 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

I have seen var. lasiocarpa at the Mt. Washington ski area on Vancouver Island, British Columbia, where it is a very common subalpine tree in Strathcona Provinical Park. It is also reported, along with subsp. bifolia, from the Sunrise area in Mount Rainier National Park, Washington.

Subsp. bifolia is very common in the subalpine zone of mountains throughout its range. It occurrences in Olympic and Mount Rainier National Parks are particularly noteworthy, having been the subject of a numerous ecological studies of the trees' population dynamics, response to fire, habitat value, etc. (see notes and citations in Arno and Hammerly 1984). It is also very common in Glacier, Yellowstone, Grand Teton, and Rocky Mountain National Parks.

Var. arizonica is said to be common in the Sangre de Cristo and San Juan Mountains, and at Wolf Creek Pass, all locations in Colorado.

Remarks

Citations

Harris, A.S. 1965. Subalpine fir [Abies lasiocarpa (Hook.) Nutt.] on Harris Ridge near Hollis, Prince of Wales Island, Alaska. Northwest Science 39:123-128.

Heusser, C.J. 1954. Alpine fir at Taku glacier, Alaska, with notes on its post glacial migration to the territory. Bulletin of the Torrey Botanical Club 81:83-86.

Luckman, B.H. 2003. Assessment of present, past and future climate variability in the Americas from treeline environments. IAI CRN03 Annual Report 2003.

Silba, J. 2008. Journal of the International Conifer Preservation Society 15(2):42.

See also

Farjon (1990).

Lanner (1983).

Lanner (1999).

Liu 1971.

MacKinnon et al. 1992.

FEIS database.

Vidakovic 1991.

Zavarin, E., K.Snajberk, T.Reichert, and Tsien E. 1970. On the geographic variability of the monoterpenes from the cortical blister oleoresin of Abies lasiocarpa. Phytochemistry 9:377-395.