Western Pine Species Loses Ground to Neglect
The moss-covered 60-foot-tall snags that were once thriving whitebark pine trees stand like ghosts in this forest now dominated by subalpine fir.
The curious pine, which grows its cones pointing skyward, once provided tons of large, nutritious seeds for at least 110 different animal species, ranging from small birds and mice to grizzly bears. Now, the few solitary, centuries-old trees that still cling to life here and in the neighboring Selway-Bitterroot Wilderness are facing local extinction.
"This is the area where the Clearwater National Forest has decided to try and save this species," said Bob Keane, an ecologist with the U.S. Forest Service's Fire Sciences Laboratory in Missoula, Mont. But the scene is being played out in many parts of the northern Rocky Mountains.
Whitebark pine, which grows along the Rocky Mountains spine from Banff in Canada to the Wind River in Wyoming, as well as the Pacific Cascade Range and parts of the Sierra Nevadas, is disappearing rapidly. In Glacier National Park, the species is down to 5 percent of its historical range. In places around Missoula, 60 percent to 80 percent of the trees have died. In the Bob Marshall Wilderness in Montana, trees also are dying quickly.
For decades, the stark gray snags crowding the ridge lines like moss-adorned slate gravestones failed to ring an alarm. Ecologists first thought the massive die-offs were part of the tree's natural cycle. Plus, timber scientists weren't interested in the slow-maturing, low-value tree that grows at inaccessible elevations. Most research funds were earmarked for more marketable timber.
The reason for the wholesale die-offs was also twofold.
In the 1930s, mountain pine beetles swarmed through the forests, a natural, cyclical phenomenon. The tiny beetles dig egg chambers in trees, running vertical to the trunks. The larvae then tunnel around the trunk. With millions of beetles invading a single tree, the larvae eventually do so much damage they can cut off the passage of nutrients into the crown.
Under typical circumstances, whitebark pine would resist the beetles. But the tree came under stress at the same time from an exotic disease from France called white pine blister rust. "Blister rust starts at the top of a tree and kills so much foliage that the tree can't meet its respiratory needs," Keane said.
Fire ecologist Steve Arno, who first noted the massive decline in the 1960s, recruited Keane to unravel the tree's ecological secrets. For four summers Keane camped in the Bob Marshall Wilderness, observing an astounding relationship between the whitebark pine, wildlife and fires , which the trees need to thrive.
Keane estimates that subalpine fir dominates 22 percent of the traditional whitebark pine habitat. Historically, the fir only grew in about 8 percent. "Without fire, fir will overtake an area in three to four decades," he said.
On Beaver Ridge, saw crews have thinned firs from some areas to stimulate growth and cone production in whitebark pine, as well as clear-cut one- to two-acre plots to create caching sites for the Clark's nutcracker, a bird on which the tree depends.
Some surviving whitebark pines that stand only about five feet tall and measure an inch in diameter are 200 years old. "We're not sure they'll ever take off," Keane said. "But some might."
After setting fires, workers will replant some areas and leave others to the nutcracker. But thinning and reseeding will prove fruitless unless wildfire is allowed to return to the ecosystem.
"The only way to perpetuate the species is to open up areas," Keane said. "That means fire, because innovative methods like thinning and clear-cutting won't always work. First of all, about 49 percent of the whitebark range is located in wilderness areas where you can't even use a chain saw."
It often takes 10 years before a burn site becomes conducive to whitebark seedling survival.
Grasses and forbs must first create enough ground cover to hold soil moisture. Then it takes an additional 20 to 40 years before seedlings become functional trees. And then 20 more years before they start producing cones.
Whitebark pine thrives in the subalpine regions of the western U.S. and Canada. The fire-tolerant pine produces an abundance of nuts, which are eaten and stashed by Clark's nutcrackers.
Nutcrackers bury caches of nuts in loose soil on the mountainside. Bears travel to the high country in the summer in search of nutcracker stashes.
Intermittent fires scorch back competing subalpine fir trees. Fires also loosen soil, which is ideal for nutcracker caches.
Nut stores, which are forgotten and undiscovered, sprout into clusters of young pine trees.
An introduced fungus, white pine blister rust, has weakened many pines to the extent that they can no longer exude enough sap to defend themselves against mountain pine beetles. Unchecked, beetle larvae can girdle a tree.
With fewer seeds available, the nutcrackers eat more of what they harvest, reducing the potential for seed germination.
Suppression of fire allows subalpine fir trees to overwhelm whitebark pine stands, crowding out slow-growing pine seedlings.
The decline in nut caches sends bears to lower altitudes, which escalates their interactions with humans.
SOURCES: USGS; J. Foott; Mark Matthews