Pinus albicaulis (whitebark pine) description

Pinus albicaulis

Engelmann 1863

Common names

Whitebark pine, whitestem, alpine whitebark, pitch, scrub or creeping pine (Peattie 1950); white pine (Little 1980); pine à blanche écorce (Kral 1993).

Taxonomic notes

Syn: Apinus albicaulis (Engelmann) Rydberg. Belongs to subsection Cembra, the stone pines, so called for their large, wingless seeds.

Description

"Trees to 21 m tall; trunk to 1.5 m diam., straight to twisted and contorted; crown conic, becoming rounded to irregularly spreading. Bark pale gray, from a distance appearing whitish to light gray and smooth, in age separating into thin plates. Branches spreading to ascending, often persistent to trunk base; twigs stout, pale red-brown, with light brown, often glandular pubescence, somewhat roughened by elevated scars, aging gray to pale gray-brown. Buds ovoid, light red-brown, 0.8-1 cm; scale margins entire. Leaves 5 per fascicle, mostly ascending and upcurved, persisting 5-8 years, 3-7 cm x 1-1.5(-2) mm, mostly connivent, deep yellow-green, abaxial surface less so, adaxial surface conspicuously whitened by stomata, margins rounded, minutely serrulate distally, apex conic-acute; sheath 0.8-1.2 cm, shed early. Pollen cones cylindro-ovoid, ca. 10-15 mm, scarlet. Seed cones remaining on tree (unless dislodged by animals), not opening naturally but through animal agency, spreading, symmetric, broadly ovoid to depressed-ovoid or nearly globose, 4-8 cm, dull gray- to black-purple, sessile to short-stalked; scales thin-based and easily broken off; apophyses much thickened, strongly cross-keeled, tip upcurved, brown; umbo terminal, short, incurved, broadly triangular, tip acute. Seeds obovoid; body 7-11 mm, chestnut brown, wingless, edible. 2n=24" (Kral 1993).

Foliage has sweetish taste and odor when crushed (Little 1980).

In the absence of cones, whitebark pine strongly resembles P. flexilis. However, limber pine twigs become roughened at a smaller size (usually <10 cm diameter, vs. > 10 cm diameter in P. albicaulis. On older trees (>30 cm dbh), limber pine bark is usually composed of longitudinal reddish-brown plates with intervening fissures, while whitebark pine bark becomes light brown and thinly platy without conspicuous fissures. When in flower, whitebark pollen cones are a striking red color, while limber pine pollen cones are reddish or yellow. Saplings are very difficult to distinguish; Kral (1993) contends that bud scale margins are entire in whitebark pine, whereas lower bud scales have ciliolate margins in limber pine; I have not tested this assertion in the field.

Range

US and Canada: At montane to timberline elevations (1300 to 3700 m) in the Rocky Mountains of Alberta, British Columbia, Montana, Idaho and Wyoming; in the Coast Mountains of British Columbia; in the Cascade Mountains of Washington and Oregon; and in certain isolated intermountain ranges of eastern California and Nevada (Little 1980, Kral 1993). See also Thompson et al. (1999).

Although two reliable dendrologists, G.B. Sudworth (1917) and N.T. Mirov (1967), include Utah in the distribution of Pinus albicaulis, more recent workers have not found it to occur there (Kral 1993).

Big tree

Diameter 268 cm, height 21.0 m, crown spread 14 m, in Sawtooth National Recreation Area, Idaho (American Forests 1996). Also, height 27.4 m, dbh 119 cm, in Alpine Lakes Wilderness, WA (Van Pelt 1998).

Oldest

Tree RRR15 collected in central Idaho had a crossdated age of 1267 years (Perkins and Swetnam 1996, cited by RMTRR 2006). Brian Luckman has a crossdated age of 882 years for a tree in the Rockies of Alberta. Luckman (2006) also cites a "Youngblut 1999" (no details) as having found a 1060 year old tree in Saskatchewan. I sampled a stand in the Independence Mountains of Nevada that probably contained comparably-aged trees, and I suspect that other arid mountain ranges of the Great Basin also contain trees exceeding 1000 years.

Dendrochronology

The species has not proven particularly useful because of poor latewood definition and low interannual ringwidth variation, and so has not been extensively sampled except for ecological research.

Ethnobotany

Interior Salish peoples harvested the seeds by removing the cones and roasting them overnight. The seeds were crushed to make a flour. The fibrous roots were used to sew bark together and to weave watertight containers. The western world values whitebark pine for its aesthetic qualities and for its value as wildlife habitat (Parish et al. 1996).

Observations

Have found particularly fine stands atop the Little Belt Mountains of Montana, at elevations above 1500m in the eastern Cascade Range of Washington, and near timberline in the Independence and Jarbidge Mountains of Nevada. It is particularly interesting to see in the Ruby Mountains of Nevada, where in Lamoille Canyon and Thomas Canyon (both easily accessible by popular hiking trails), it grows with the limber pine, P. flexilis, affording a fine opportunity to observe how these two rather similar white pines compete to achieve stand dominance on different slopes and substrates, and at slightly different elevations. Similarly, stands in the Little Belt Mountains and the Wind River Mountains of Wyoming provide the opportunity to observe the successional relationships between P. albicaulis, Abies lasiocarpa, and Picea engelmannii.

Remarks

Whitebark pine, like other stone pines, has coevolved with nutcrackers (in this case, Nucifraga columbiana). The nutcrackers rely on stone pine seeds as their principal food source "for at least 9 months of the year and for raising the young. In addition to special adaptations on gathering, transporting, caching, and finding again the hoarded seeds, the whole annual cycle of the nutcracker's life (time of breeding and moulting), its mating system, and its habitat use are adjusted to the use of pine seeds" (Tomback et al. 1990). Moreover, since the whitebark pine's cones do not open, seed hoarding and caching by the nutcracker and related corvids (e.g., jays) constitute the only reproductive mechanism available to this pine (Tomback et al. 1990). The natural history of the stone pine/corvid mutualism is explored at length by Ron Lanner in his very engaging book Made for Each Other: A Symbiosis of Birds and Pines (1996).

The seeds are also an important food source for certain mammals: "Whitebark pine seeds are an important high-quality food for bear populations that occupy ecosystems with continental climates south of the United States - Canada border. Availability of pine seeds affects human-bear conflict and bear mortality. In most areas bears acquire whitebark pine seeds by excavating red squirrel (Tamasciurus hudsonicus) food caches... Bear use of pine seeds is restricted to stands >100 years old, and can persist for an additional 200 to 300 years" (Mattson and Reinhart 1994).

White pine blister rust (Cronartium ribicola), an introduced fungal disease, has decimated formerly extensive stands of this and certain other white pines. Mortality has been especially severe in portions of the range north of 45° latitude or west of 120° longitude (Hoff et al. 1994).

This species is one of the primary hosts to the dwarf mistletoe Arceuthobium cyanocarpum (Hawksworth and Wiens 1996).

Citations

Luckman, B.H. 2006. Current research. http://geography.uwo.ca/facilities/dendro/tree-ring-research.pdf, accessed 2007.10.22.

Perkins, D., and T. W. Swetnam. 1996. A dendroecological assessment of whitebark pine (Pinus albicaulis) in the Sawtooth-Salmon River region of Idaho. Canadian Journal of Forest Research 26:2123-2133.