Pinus albicaulis


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Pinus albicaulis
Species Authority: Engelm.
Common Name(s):
English Whitebark Pine, Scrub Pine
Taxonomic Notes: Whitebark Pine is considered to be one of five stone pines worldwide, comprising subsection Cembrae within the section Strobus. Whitebark Pine is the only stone pine occurring in North America.

Assessment Information [top]

Red List Category & Criteria: Endangered A4ace ver 3.1
Year Published: 2013
Date Assessed: 2011-04-26
Assessor(s): Mahalovich, M. & Stritch, L.
Reviewer(s): Thomas, P. & Farjon, A.

Whitebark Pine (Pinus albicaulis) is experiencing serious decline due to White Pine Blister Rust (WPBR) and Mountain Pine Beetle (MPB).  In areas where WPBR and MPB are both present the decline in population numbers and population resilience is such that population sustainability in the long-term is predicted to decrease. Work is being conducted to identify seed trees that exhibit some degree of resistance to WPBR. This work is being complicated where populations are also under attack from MPB. Additional research needs to be initiated into the affects of WPBR and MPB on the mutualism between corvids and Whitebark Pine in regard to seed dispersal. Initial research indicates that when seed-producing trees decline in number, a point is reached where Clark’s Nutcracker does not visit the site. Without the caching of seed by Clark’s Nutcracker recruitment of seedlings will not occur and local population extirpation is expected. Although concrete figures cannot be given for the entire range of the species, a decline rate of 50% as a minimum figure, incorporating both past decline (past 100 years) and suspected future decline (next 80 years), is reasonable and therefore qualifies the species for Endangered under criterion A4.

2008 Vulnerable
1998 Vulnerable (Oldfield et al. 1998)
1998 Vulnerable

Geographic Range [top]

Range Description:

Whitebark Pine is distributed from 37° to 55°N latitude and from 128° to 107°W longitude (Arno and Hoff 1990).  The total global extent of occurrence has been estimated to be 337,067 km2 with an estimated 190,067 km2 in Canada and the remaining 147,000 km2 in the U.S.A. (COSEWIC 2010). The global area of occupancy has not been calculated but would be in excess of 2,000 km2.

Its distribution is split into two broad sections, one following the British Columbia Coast Ranges, the Cascade Range, and the Sierra Nevada.  The Rocky Mountain distribution extends along the high ranges in eastern British Columbia and western Alberta, and southward at high elevations to the Wind River and Salt River Ranges in west-central Wyoming.  The species occurs as high as 3,050 to 3,660 m in the Sierra Nevada and northwestern Wyoming, 2,590 to 3,200 m in western Wyoming and as low as 900 m in the northern limits of its range in British Columbia.

In the USA, outlying populations of Whitebark Pine are found atop the Sweetgrass Hills in north-central Montana 145 km east of the nearest stands in the Rocky Mountains across the Great Plains grassland, in outlier stands in the Blue and Wallowa Mountains of northeastern Oregon and in small, isolated ranges in northeastern California, south-central Oregon, and northern Nevada (Arno and Hoff 1990).

The oldest known whitebark pine tree is found in central Idaho on the Sawtooth National Forest (Perkins and Sweetnam 1996) exhibiting homozygosity for 13 isozyme loci (12 for common alleles and one for a rare allele) (Mahalovich and Hipkins in press).
Canada (Alberta, British Columbia); United States (California, Idaho, Montana, Nevada, Oregon, Washington, Wyoming)
Range Map: Click here to open the map viewer and explore range.

Population [top]


Over 90 percent of Wwhitebark Pine forests occur on public lands in the U.S. and Canada. 

In the U.S.A. Whitebark Pine occurs on 5,085,904 acres (20.06% of the total) on 12 National Forests in northern Idaho and Montana:  2,773,620 of those acres (54.5%) are within wilderness or inventoried roadless areas and another 40,661 acres are designated or proposed research natural areas (Shelly et al. 2010).  Another 427,000 acres of Whitebark Pine occur in three National Parks in Montana and northwestern Wyoming (from NPS websites). Acreages for other areas not available.

In Canada the total population is estimated to be around 200 million trees (COSEWIC 2010).

Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology:

 Whitebark Pine is a keystone species of the upper and subalpine ecosystems. It is also a foundation species for protecting watersheds as it tolerates harsh, wind-swept sites that other conifers cannot, the shade of its canopy regulates snowmelt runoff and soil erosion, and its roots stabilize rocky and poorly developed soils (Tomback and Kendall 2001). Whitebark Pines may live in excess of 1,000 years. While Whitebark Pine can begin to produce cones at 30-50 years, sizeable cone production usually begins at 60-80 years (COSEWIC 2010). An average generation length of 60 years is used in this assessment.

In upper subalpine sites Whitebark Pine is a major seral species that is often replaced by the shade-tolerant Subalpine Fir (Abies lasiocarpa), Spruce (Picea engelmannii), or Mountain Hemlock (Tsuga mertensiana) (Arno and Weaver 1990).  The shade intolerant tree species Lodgepole Pine (Pinus contorta) is also found with Whitebark Pine seral sites. Other minor species sometimes found with Whitebark Pine are Douglas-fir (Pseudotsuga menziesii), lLmber Pine (Pinus flexilis), Alpine Larch (Larix lyalli) (Pfister and others 1977), and Western Wwhite Pine (Pinus monticola).  Climax Whitebark Pine sites are found at high elevations, particularly harsh sites in the upper subalpine forests and at treeline on relatively dry, cold slopes, where trees often occur in elfin forests, clusters, groves or tree islands (Arno and Weaver 1990; Steele et al. 1983).

 Most Whitebark Pine forests have low diversity in vascular plants (Forcella 1977) with the majority of undergrowth plant cover being composed of Grouse Whortleberry (Vaccinium scoparium), Blue Huckleberry (V. globulare), Black Huckleberry (V. membrenaceum), False Azalea (Menziesia ferruginea), Woodrush (Luzula hitchcockii), and Beargrass (Xerophyllum tenax) (Pfister et al. 1977, Arno and Weaver 1990). Other plants that may be occasional dominants include Idaho fescue (Festuca idahoensis), Parry’s rush (Juncus parryi Engelm.), Wheeler Bluegrass (Poa nervosa (Hook.) Vasey), Buffaloberry (Sheperdia spp. Nutt.), Kinnikinnick (Arctostaphylos uva-ursi (L.) Spreng), and Pipsissewa (Chimaphila umbellata (L.) W.Bartram) (Arno and Weaver 1990, Aubry et al. 2008). High elevation climax stands of Whitebark Pine can contain many unique alpine, subalpine, and montane undergrowth species assemblages, some of which are only found in association with Whitebark Pine (Forcella 1977, Tomback and Kendall 2001). Forcella and Weaver (1977) found that Whitebark Pine forests had unexpectedly high biomass but low productivity.

 The large, energy-rich wingless seeds of Whitebark Pine (Lanner 1982, Lanner and Gilbert 1994, Tomback 1983) are a food source in the fall and spring diets of 20 wildlife species (Lorenz and others 2008). When there are at least 40 cones produced per Whitebark Pine tree, pine nuts provided 97% of the annual nourishment for Yellowstone National Park’s grizzly bears (Robbins et al. 2006).  Female grizzly bears in the Greater Yellowstone Ecosystem derive 40-50% of their fall nutrition from Whitebark Pine nuts (Felicetti et al. 2003).  Female bears that have fattened during the previous fall on good pine nut crops typically produce litters of three cubs compared to twins or singletons after falls of few nuts; the link between increased cub production and great pine nut years occurs because fatter females produce more cubs that are born earlier in the winter den and grow faster because mom produces more milk (Robbins et al. 2006).

Systems: Terrestrial

Use and Trade [top]

Use and Trade:

Between 1860 to 1940, billions of board feet of Whitebark Pine were cut to support the Montana mining industry; the wood was used for fuelwood in smelters and to heat miner‘s homes; now less than 1,000 acres in the United States are harvested each year, typically within a timber sale for Lodgepole Pine (Losensky 1990).

Threats [top]

Major Threat(s):

The initial reduction in Whitebark Pine is attributed to the exotic pathogen, White Pine Blister Rust (Cronartium ribicola) introduced in Whitebark Pine cover types ca. 1925 (McDonald and Hoff 2001).  Mean blister rust mortality is 35% (range of 8-58%) and mean infection of 66% (range of 17-89%) in stands sampled throughout the northwestern United States and southwestern Canada (Kendall and Keane 2001). Whitebark Pine does possess documented rust resistance. Artificial inoculation trials of the open-pollinated, phenotypically rust resistant trees in the Northern Rockies indicate rust resistance ranges from 30% (Hoff and others 1980) to 47.4% (Mahalovich et al. 2006). In the Cascade Range, the percent of canker-free seedlings in 26.3% (Sniezko et al. 2007).

The more recent mortality can be attributed to wildfire and a native pest, Mountain Pine Beetle (Dendroctonus ponderosae Hopkins). The likelihood of continuing mortality due to these disturbance agents is very much linked to the future cyclic pattern of warm weather and drought at higher elevations where whitebark pine is abundant (Logan and Powell 2001).   There have been three outbreaks of mountain pine beetle during this time. The first one in the 1920s-30s killed significant areas of Whitebark Pine and left many “Ghost Forests”.  The second outbreak was in the 1970s-80s.  The third one began in 2001 and has been killing significant areas of Whitebark Pine over the last few years (Shelly et al. 2010). 

Approximately 60 years of fire suppression have resulted in seral replacement of Whitebark Pine to Subalpine Fir (Abies lasiocarpa (Hook) Nutt.), Engelmann Spruce (Picea engelmannii Parry ex Engelm.), Mountain Hemlock (Tsuga mertensiana (Bong.) Carrière) (Keane and Arno 1993), and Lodgepole Pine (Pinus contorta Douglas ex Louden).

Due to Whitebark Pine’s range in the upper subalpine and alpine forests, it is presumed the impacts of warming temperatures will result in a decline in suitable habitat, increase mountain pine beetle activity, an increase in the number, intensity, and extent of wildfires (Aubry et al. 2008). A Random Forests multiple regression tree was used to generate a bioclimate model for Whitebark Pine based on the Hadley and Canadian General Circulation Model (1% increase GGa/yr) to estimate the climate of each pixel; by 2090, Warwell et al.(2007) predict Whitebark Pine is projected to diminish to an area equivalent to less than 3% of its current distribution.  Koteen (1999) predicts climate change will probably affect the Whitebark Pine distribution, especially forests at the lowest elevational range.

Conservation Actions [top]

Conservation Actions:

Current/Ongoing Actions: 

Identification, harnessing and deploying (tree planting) rust resistant Whitebark Pine in the Whitebark Pine genetics program (Mahalovich and Dickerson 2004, Mahalovich et al.2006, McCaughey et al. 2009). 

Ex situ gene conservation including seed and pollen in cold storage, clone banks, and seed orchards; in situ gene conservation including phenotypically, blister rust resistant Whitebark Pine and long-term genetic tests (Mahalovich 2000, Mahalovich and Dickerson 2004).

Prescribed fire is used for site preparation for artificial regeneration of rust-resistant seedlings, to enhance natural regeneration, and for release to favour Whitebark Pine (Keane and Parson 2010). 

Tree protection against Mountain Beetle include verbenone (anti-aggregate pheromone) (Kegley and Gibson 2004) and carbaryl applications (Gibson and Bennett 1985).

Citation: Mahalovich, M. & Stritch, L. 2013. Pinus albicaulis. The IUCN Red List of Threatened Species. Version 2014.2. <>. Downloaded on 28 July 2014.
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