The country's largest lakeside stands of whitebark pine trees, at Crater Lake National Park, are being assaulted by a duo of forces that are slowly decreasing the numbers of these majestic and beneficial pines, according to a new study.
Already there have been reports on how mountain pine beetles are attacking whitebark pines in Grand Teton, Yellowstone and Glacier national parks. Concern for the future of these trees prompted the U.S. Fish and Wildlife Service back in July to announce that the agency will take a longer, more extensive look at whether whitebark pine trees, a key food source for some grizzly bear populations as well as birds and squirrels, need protection under the Endangered Species Act.
Whitebark pines are a member of the "stone" pine family. The sheer stature of the tree can help maintain watersheds. In winter its bulk serves as natural snow fences, and in spring that same bulk helps shield the resulting snowbanks from the sun, thus allowing for a relatively slow and even snow melt.
Scientists regard the tree as a “foundation species” because it creates the conditions necessary for other plants and animals to get established in harsh alpine ecosystems. But the tree is in danger these days from non-native diseases, such as blister rust, and insects such as the mountain pine beetle, which are beginning to flourish in the trees' habitat thanks to climate change.
At Crater Lake these beetles and blister rust are infecting some stands of whitebark pine, the report contained in the fall issue of Park Science notes.
The cover photo of the article portrays "a grove of whitebark pine trees ... being decimated by blister rust and mountain pine beetles at the North Junction area of Crater Lake National Park."
"Natural resistance to blister rust among whitebark pine may be lower than 1 percent. Ongoing epidemics of the native mountain pine beetle appear unprecedented in extent in addition to common stress from fire, dwarf mistletoe, and ips beetles," notes the article by Michael Murray, who was the park's terrestrial ecologist from 2002 to 2008 and currently works for the British Columbia Ministry of Forests and Range.
Blister rust originated in Asia and moved to Europe, where it infected white pine seedlings that were shipped to North America around 1900, according to an article in [url=http://www.plantmanagementnetwork.org/pub/php/management/whitepine/Plant Health Progress[/url]. The fungus kills by girdling branches on infected trees, the article notes.
Mountain pine beetles, meanwhile, evolved here in the United States alongside lodgepole pines. Whitebark pines had been beyond reach of the beetles, due to the harsh environments they inhabited in the upper reaches of the Rockies and Sierra and other western mountain ranges. However, scientists say the warming climate has enabled these beetles to move higher in elevation and infest whitebark pines, which have no natural defenses against the rice-grain-sized beetles.
In his article Dr. Murray points out the value of whitebark pine stands.
Many sites where whitebark pine resides are too climatically harsh for other tree species. Thus, whitebark pine forests thrive where otherwise only meadow, talus, or other sparse natural communities would. Showy wildflowers such as heart-leafed arnica (Arnica cordifolia) and verdant tufts of smooth woodrush (Luzula hitchcockii) prefer the filtered sunlight afforded by groves of whitebark pine. This pine species also stabilizes soil on steep slopes and shades patches of snow, providing continuous flow of meltwater well into summer. As the producer of the largest tree seeds in the subalpine zone, whitebark pine supports more than two dozen species of foraging mammals and birds, including grizzly bear (Ursus arctos horribilis) and Clark’s nutcracker (Nucifraga columbiana). The value of whitebark pine to wildlife simply cannot be overstated.
According to the article, in Crater Lake "some of the oldest trees in the park garnish the margins of the 33-mile-long Rim Drive and Rim Village, enjoyed by nearly 500,000 visitors every year." Unfortunately, blister rust and the pine beetles are producing an annual decline of about 1 percent of the park's whitebark pine trees standing higher than breast level, it says.
With hopes of slowing the demise, Crater Lake technicians are using packets of synthetic hormones to drive pine beetles away from healthy trees.