In the recent past, the white bark pine, limber pine and bristlecone pine, of the five needle pine family, have become of greater interest to foresters in southwest Colorado.
Gretchen Fitzgerald, forester at the Dolores Ranger District, explained that white bark pine is important for wildlife in the region. In Montana, for instance, with a larger population of grizzly bear, white bark pine is an important food source for the bear, providing it with protein, oil and the big seeds the bears need in order to store enough energy for hibernation. Other high elevation species, such as the Clark’s nutcracker, also use the white bark pine.
Fitzgerald explained the Clark’s nutcracker will store up a cache of these large seeds on a high, open and windy ridge. This is because it is easier to find in the wintertime. However, the bird doesn’t normally collect all the seeds, and thus helps to replant the tree by the seeds left behind.
Presently, white pine blister rust is posing a big threat to the five needle pines and is already attacking trees in Montana, Wyoming and northern Colorado.
“Blister rust is a fungus that attacks the bark causing it eventually to blister,” Fitzgerald explained. After this fungus blisters, it girdles the tree and kills it.
Right now, blister rust is not prominent in our area of southwest Colorado, however, this may not stay this way. Both limber pine and bristlecone pine are vulnerable to blister rust.
White pine blister rust is a nonnative pathogen that was introduced to North America in 1910.
“It’s been spreading ever since,” Anna Schoettle, research scientist for the Rocky Mountain Research Institute in Fort Collins said. Now, the forests of Colorado are on the front line, facing potential infection.
In an effort to protect the area’s population of these tree species and keep them resilient, different seeds from bristlecone and limber pine have been collected and sent to Colorado State University.
Also, Fitzgerald led a crew of Forest Service employees, interns and Mountain Studies Institute researchers and interns this past summer in mapping the location of the most prominent five needle pine in the San Juan National Forest — limber pine or southwestern white pine. Seeds will be planted, grown and studied to see what the genotypic and phenotypic difference is in separate geographic areas.
Schoettle said that the habitat and climatic conditions of southern Colorado can support blister rust and that it is expected that the disease will continue to enter Colorado.
Schoettle, with the help of MSI, has been gathering seeds of five needle pines in southern Colorado for the past seven years. These have been stored in freezers at a research station for genetic conservation and are now being used to study pine’s resistant to the disease.
Schoettle explained that none of the pines evolved with disease, yet each species of five needle pine have some type of resistance to the disease. However, as of now, it is unclear if the resistance is at a high enough frequency that a viable population will remain after the disease has come to the region.
Schoettle said there seemed to be a reasonably high frequency of resistance in limber pine, but noted this resistance is not geographically consistent.
Seeds collected from the high-resistant pine will be planted in greenhouses at the Rocky Mountain Institute. There, they will be grown to seedlings, tested, exposed to drought conditions, all in order to test if the tree can grow with the same frequency of resistance to white pine blister rust as in its natural location. If it can, the limber pine seeds can be grown to seedlings in the greenhouses, then planted in areas where the five needle pine populations have been impacted by blister rust.
Also, during this testing period, Schoettle said she and other researchers will be studying the differences of limber and southwestern white pine in the San Juan National Forest.
Fitzgerald also noted that an interesting observation has been made during this study over the last summer. “Our tree looks like southwestern white pine, especially in the lower elevation,” Fitzgerald said. However, when studied, this tree has more characteristics of limber pine than southwestern white. There is a question of whether or not there has been a hybridization of the two species.
Schoettle and other researchers at the RMI in Fort Collins will study the genetics of the seeds brought from San Juan Forest region and also study their growth patterns. In this way, they should be able to tell which species the tree is, or if it is a hybridization.
Schoettle said this study should take a total of 10 months.
“This is a fantastic thing the San Juan Forest is doing, to be proactive,” Schoettle said. “This is an important species to wildlife, for the watershed and for recreation.”
Schoettle and Fitzgerald both thanked MSI for help in mapping the pines and in seed collection.
Fitzgerald is hoping that the study may also result in finding a tree that could be replanted in areas where replanting Engelmann spruce has been troublesome.