Pinus albicaulis Engelm.
Whitebark pine is a medium-sized tree growing in the high mountains. It grows scattered but becomes increasingly abundant towards the south of its range. It is confined to dry, exposed sites at timberline. In British Columbia, it usually grows in even-aged, pure or mixed-species stands. With increasing elevation, the trees grow more scattered and in islands. Whitebark pine is valued for watershed protection and aesthetics (Klinka et al. 2000). Its seeds are fairly large and are an important food for wildlife. Due to the effects of fire suppression, introduced fungal disease (white pine blister rust – Cronartium ribicola) and mountain pine beetle (Dendroctonus ponderosae), population densities of whitebark pine have decreased drastically in the Northern Rocky Mountains (Tomback et al. 1995), and in the southern part of British Columbia local extirpation of the species may be possible.
The range of whitebark pine covers the central and south of the Pacific and central and south of the Cordilleran region (Little 1971). Less than half of the species’ range is inside British Columbia.
Distribution and Protected Areas – from Hamann et.al. 2005
Conservation Status Summary – from Chourmouzis et.al. 2009
No in situ conservation concerns are identified for this species.
Ex situ collections
A small trial plantation of first-generation wind-pollinated seedlings from resistant whitebark pine parents was established at Marks Butte near Clarkia, Idaho, in 1979 (Hoff 1980).
Cone crops are irregular and sometimes large, and seed predation is intense. Germination rates under field conditions are low (8-14%), due to developmental factors (McCaughey and Schmidt 1990). In B.C. the species appears to be well represented in protected areas. However, it is severely at risk in the United States.
Clark’s nutcrackers (Nucifraga columbiana) play an essential role in whitebark pine reproduction. They hide seeds for winter food, and often, cached seeds are from the same maternal parent. As a result, caches of seeds that germinate result in clumps of closely related trees (Furnier et al. 1987; Rogers et al. 1999). The resulting level of inbreeding is fairly high, but within the range of other bird-dispersed stone and piñon pines (Krakowski 2001). Inbreeding is substantial, resulting primarily from self-pollination but also from some consanguineous mating, with an estimated outcrossing rate of around 70 % (Krakowski 2001). The majority of genetic variability occurs within populations (Jorgensen and Hamrick 1997; Bruederle et al. 1998; Krakowski 2001). Populations in British Columbia are only moderately differentiated (Krakowski 2001). Insights from historical seed movement may provide a basis for recovery plans for this threatened species (Richardson et al. 2002).
Resource management and seed transfer
There is a need for screening for blister rust resistance and for reintroducing wildfires to avoid successional replacement of whitebark pine by fir and spruce. Whitebark pine is extremely susceptible to blister rust (Bingham 1972). Yet, genetically resistant trees have been found (Hoff and Hagle 1990). Four different defense mechanisms were observed in resistant plants (Hoff and Hagle 1990). Many attempts have been made to cross whitebark pine with the other four, more blister rust resistant white pine species in its subsection Cembrae and with most species in subsection Strobi. Almost all have ended either in failure or with inconclusive results (Bingham et al. 1972). Thus, hybridization does not offer much potential for creating more rust-resistant genotypes. No putative hybrids of whitebark pine have been identified in natural stands.