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Pinus albicaulis



Pinus albicaulis - Whitebark pine, Scrub pine, Creeping pine
  • Pinus albicaulis - Whitebark pine, Scrub pine, Creeping pine - Click to enlarge
  • Pinus albicaulis cone - Click to enlarge
  • Pinus albicaulis trees - Click to enlarge

 

Scientific name: Pinus albicaulis  Engelmann 1863

Synonyms: Apinus albicaulis (Engelm.) Rydb., Pinus cembroides Newb., Pinus flexilis var. albicaulis (Engelm.) Engelm., Pinus flexilis subsp. albicaulis (Engelm.) Engelm., Pinus shasta Carrière

Common names: Whitebark pine, Scrub pine, Creeping pine

 

Description

Tree to 20 m tall at lower elevations, progressively shortened upward and forming a spreading shrub at the alpine tree line. Multistemmed or with a single trunk to 1.5(-2.5) m in diameter. Bark pale grayish white at first (hence the scientific and common names), breaking up into small gray or light tan blocks with age. Crown oval or rounded, with numerous horizontal or upswept, slender branches. Twigs reddish brown, minutely hairy at first, becoming gray and bald during the second season. Buds loose, 5-10 mm long, not resinous. Needles in bundles of five, (3-)4-7(-9) cm long, stiff, lasting 4-8 years, dark yellowish green. Individual needles with lines of stomates on all three faces, an undivided midvein, and two to four resin canals touching the epidermis. Sheath 8-12 cm long, soon shed. Pollen cones 10-15 mm long, red. Seed cones (4-)5-8 cm long, egg-shaped to almost spherical, with (7-)30-60 scales, purplish green before maturity, ripening purplish brown to almost black, remaining closed and breaking up on the tree, often picked apart by seed-eating birds and mammals, unstalked or very short stalked. Seed scales wedge-shaped, thick, with a prominent triangular umbo at the tip. Seed body 7-11 mm long, egg-shaped, unwinged.

Mountains of western North America from central British Columbia south to east-central California, northeastern Nevada, and northwestern Wyoming. Forming sparse, pure stands or mixed with other subalpine and high montane conifers on rocky soils; (1,100-)1,500-3,500(-3,700) m.

 

Conservation Status

Red List Category & Criteria: Endangered

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.

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. 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.

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. 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. 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).  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), Limber pine (Pinus flexilis), Alpine larch (Larix lyalli), and Western white 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.

Most Whitebark pine forests have low diversity in vascular plants with the majority of undergrowth plant cover being composed of Grouse Whortleberry (Vaccinium scoparium), Blue Huckleberry (Vaccinium globulare), Black Huckleberry (Vaccinium membrenaceum), False Azalea (Menziesia ferruginea), Woodrush (Luzula hitchcockii), and Beargrass (Xerophyllum tenax). 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). 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 and Weaver (1977) found that Whitebark pine forests had unexpectedly high biomass but low productivity.

The large, energy-rich wingless seeds of Whitebark pine are a food source in the fall and spring diets of 20 wildlife species. 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.  Female grizzly bears in the Greater Yellowstone Ecosystem derive 40-50% of their fall nutrition from Whitebark pine nuts.  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.

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. 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. 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% to 47.4%. In the Cascade Range, the percent of canker-free seedlings in 26.3%.

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. 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.

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), 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. 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.

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.

Identification, harnessing and deploying (tree planting) rust resistant Whitebark pine in the Whitebark pine genetics program. 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. 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. Tree protection against Mountain Beetle include verbenone (anti-aggregate pheromone) and carbaryl applications.

 

Cultivars

Pinus albicaulis ’#1 Dwarf                                                  
Pinus albicaulis ’Algonquin Pillar’                     
Pinus albicaulis ’Dwarf Form No.1.’                 
Pinus albicaulis ’Falling Rock’                
Pinus albicaulis ’Flinck’                                     
Pinus albicaulis ’Glauca’                                  
Pinus albicaulis ’Jerry Morris # 1’                 
Pinus albicaulis ’Jerry Morris # 3’     
Pinus albicaulis ’Kostelec’                               
Pinus albicaulis ’Lake Sabrina’            
Pinus albicaulis ’Landis’                                    
Pinus albicaulis ’Nana’                                    
Pinus albicaulis ’Nobles Dwarf’               
Pinus albicaulis ’Number One Dwarf’              
Pinus albicaulis ’Rocking Rio’       
Pinus albicaulis ’Tioga Lake’   

 

References

  • Farjon, A. (2010). A Handbook of the World's Conifers. Koninklijke Brill, Leiden.
  • Eckenwalder, J.E. (2009) Conifers of the World: The Complete Reference. Timber Press, Portland.
  • IUCN Red List of Threatened Species, International Union for Conservation of Nature and Natural Resources. Cambridge, UK /Gland, Switzerland

Copyright © Aljos Farjon, James E. Eckenwalder, IUCN, Conifers Garden. All rights reserved.


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