In Idaho, western white pine occurs almost exclusively in the Northern Rockies Eco-region. Until about 50 years ago, it was the most abundant forest type in that region.
Prior to European settlement, the landscape pattern consisted of large mosaics of many thousands of acres, major portions of which were of a similar age class, a legacy of mixed-severity and large stand-replacement fires. White pine forests of 200 or more years of age were common, but so were newly regenerated small trees and shrubs resulting from recent bums, as were forests of an intermediate age. Data from the Coeur d’Alene Basin indicates stand replacement fires occurred at a given location every 150 to 250 years on the average. Mixed severity fires that killed only part of the stand occurred at about 60 to 85 year intervals. After a long absence of fire, western red cedar, western hemlock, or grand fir-species most tolerant of shade would eventually dominate a site. Prior to fire suppression, these species rarely predominated except on the wettest sites because of their susceptibility to fire. Today, the amount of western white pine is 93 percent less than 40 years ago.
The causes of change include outbreaks of the mountain pine beetle, fire suppression and harvesting. The primary agent of change, however, is the white pine blister rust. The rust, a disease of white pines, did not formerly occur in North America until accidentally introduced into Vancouver Island, British Columbia in about 1910. By the 1940s, the disease was epidemic in Idaho. Today, a combination of blister rust, mountain pine beetle and harvesting has nearly eliminated mature western white pine stands. Remaining large western white pines now exist mostly as scattered individuals. The rust continues to kill most trees that regenerate naturally, and rust and bark beetles continue to kill remaining large trees. Rust resistant western white pine strains have been bred from wild white pines, which have shown some level of genetic resistance. Rust resistant seedlings have been planted since the mid-1970s, but the amount represents only a small part of the area previously occupied. Natural regeneration is also encouraged where possible, mainly for gene conservation.
Even though most trees will die from the rust, some will live and may carry genes for rust resistance and other traits that are important to the eventual restoration of the species. The numbers of plantings have not been adequate to offset the rate of continuing loss of larger trees and the nonresistant natural regeneration. Statewide inventory data show that mortality is greater than growth for the species. On federal lands, planting has decreased in recent years due to the decreased amount of regeneration harvesting.br> The decrease in western white pine is significant both economically and ecologically. Economically, western white pine is the most valuable of timber species, and potentially can produce greater bio-mass than its associates, especially at ages over 100 years.
In terms of the ecology of the species, western white pine achieved large size and 200 years or more of age. Thus, it was the main component of many old growth forests in the Northern Rockies Province. Western white pine is resistant to root rots that significantly affect many other tree species in this forest type.
The white pine is Idaho’s state tree, and it is a species with an interesting history. Prized as a commercial species because of a long straight trunk that runs free of branches for up to two-thirds of the tree’s length, the white pine was decimated by a disease called blister rust. Blister rust is a fungus that was imported in 1910 on French white pine ornamental shrubs. Forest geneticists have worked diligently over the years to develop a strain of western white pine that is resistant to blister rust. Today, reforestation efforts are underway throughout the tree’s historic range — northern Idaho, southern British Columbia, western Montana, and other areas — in an effort to reestablish the western white pine. The reforestation effort is hampered by the presence of firs and other trees that took over the western white pine’s range when that species died back.
With a preference for deep, porous soils and gentle slopes, the western white pine grows rapidly, attaining heights of 175 feet and trunk diameters from 5 to 8 feet. The species is easily identified by its three- to five-inch-long needles, which grow in bunches of five, and its stalked cones, which are nearly straight and grow from 5 to 15 inches long. The bark of the mature western white pine is brownish-gray, and is broken into small rectangular blocks.
The wood of the western white pine is easily worked with carpenter’s tools, and is ideally suited for applications including window and door frames, paneling, shelving, and some structural applications.
The largest western white pine in the world stands 219 feet high near Elk River, Idaho!
White pine in the American West: a vanishing species – can we save it? (pdf, 4.5mb)