Burning to survive

Fire might be one thing that could save white-bark pines ofMontana mountains

By ERIN DEMUTH, Special to the News Sentinel
November 3, 2003

At 7,500 feet - tree line - vegetation becomes scarce in the Rocky Mountains of the Western United States. The climate is cold, the ecosystem is fragile, and few trees can withstand the environment at this elevation.

Yet the white-bark pine grows under no other conditions.

HENRI GRISSINO-MAYER
SPECIAL TO THE NEWS SENTINEL

Alone dead white-bark pine on Morrell Mountain in Montana's Lolo National Forest is silhouetted against the sky.

If that tree perishes from this high-terrain habitat, the American West stands to lose more than one species. It may even lose an icon of the frontier - the grizzly bear.

This summer, Henri Grissino-Mayer began research on Morrell Mountain in Montana's Lolo National Forest that might help save these trees from obliteration at the hands of a pathogen, a beetle and catastrophic wildfires.

The University of Tennessee assistant professor of geography is collaborating with Lori Daniels of the University of British Columbia; Cathy Stewart, a Lolo National Forest fire ecologist; and Ward McCaughey, an expert on white-bark pines from the Rocky Mountain Research Station of the USDA Forest Service.

According to Grissino-Mayer, an exotic pine blister rust was introduced near Vancouver, British Columbia, about 1910. In just 25 years, the Eurasian pathogen spread through most of the western United States, destroying the ability of the white-bark pine to withstand damage inflicted by mountain pine beetles and fire.

"I've seen it firsthand, and it is really sad," says Grissino-Mayer. "These trees live to be over 1,000 years old. Now they're all dying."

Though it seems ironic, fire is actually crucial to sustaining the dwindling populations of these pines. Grissino-Mayer is using dendrochronology to discover how important fires have been historically to the preservation of white-bark pine stands, a subject few people know much about.

Dendrochronology is the science of tree-ring dating.

Rings inside the trunks of dead or fallen trees are an incredibly accurate history of everything that has happened to the forest within the lifetime of individual trees.

Drought, insect blight and fire information are all recorded in these rings, each of which is equivalent to one year of growth. For instance, if little rain fell during one year, a tree's growth ring for that year would probably be narrow in comparison to a year where a fair amount of rain fell.

Insects that inhibit nutrient flow or eat the leaves of trees also contribute to small rings.

Fire is no different.

When Grissino-Mayer, a member of the UT's Global Environmental Change Research Group, studies a cross section of a white-bark pine that has endured fires, the scars will be there.

Though the tree ring retains its scar forever and human burn scars fade with time, both scars can be described as callous, or toughened, tissue that was killed by the heat of fire.

The damaged and blackened tissue is more than just a chronological record of the years that fires swept through white-bark pine stands, however. Fire scars also reveal what season a fire occurred in, how frequently fires occurred, how severe fires were and the size of the area burned.

"To understand where fire is going in the future, you've got to understand where fire came from in the past," says Grissino-Mayer. "We need a trajectory to improve forest management and save this species."

Around 1920, fire suppression became a widely used and popular tool to manage forests. But preventing low-intensity fires from occurring naturally has had a negative impact on pine stands in more than one way. The lack of fire has caused a massive amount of litter to build up on the forest floor, which has reduced seed germination because certain tree species need bare soil to grow.

It has also made it more difficult to disperse seeds, since some trees, the white-bark pine included, need fire to open their sealed cones.

Most tragically, however, the absence of fire has allowed the blister rust to secure a slowly tightening chokehold on white-bark pines.

The blister rust is a type of fungus that attacks trees from the top down, restricting the flow of vital nutrients. It infests the insides of needles and stems, producing abnormal growths called cankers. The pine pathogen kills trees, but it first weakens them so that they are unable to resist other lethal agents, such as the mountain pine beetle.

The mountain pine beetle, akin to the Southeast's Southern pine beetle, restricts the flow of nutrients within the tree by burrowing into the bark. This insect is native to tree-line areas in the Rocky Mountains, and healthy white-bark pines are well-equipped to handle an attack.

In fact, the beetles normally help improve the overall health of the forest ecosystem by killing a few large, elderly pines and thus creating germination room for various species of tree seedlings.

But with so many trees weakened by the exotic disease, few are strong enough to survive the beetle. The number of dead trees keeps increasing, and the more dead pines there are, the more litter lines the forest floor.

With fire-suppression policies, natural fires have not been allowed to burn away the dead plants that have accumulated since the 1920s. With all this combustible material lying around, the prospects of a catastrophic fire that could destroy the white-bark pine stands and decimate surrounding lands and houses are much higher.

As contradictory as it may seem, fires that can devastate forests and communities are nature's way of fixing the problems created by fire suppression. They are nature's way of getting rid of excess litter, making the forest healthy again and restoring the proper equilibrium.

Grissino-Mayer and his collaborators hope their pioneering reconstruction of fire history in white-bark pine stands will enable forest managers and conservationists to reinstate fire with its natural frequency and intensity.

This way, horrendous fires may be avoided, nature's balance can be reset, and the pine can be saved, which is absolutely imperative if the Rocky Mountains are to retain the tree-line ecosystems known now.

Among the dependent animals at risk: grizzly bears, which eat white-bark pine seeds as their primary food source. The seeds are rich in proteins and full of calories that fatten the animals up and prepare them for winter hibernation.

"If the white-bark pine goes, it's not just the grizzly bears that will go," says Grissino-Mayer. "It's Clark's nutcracker, it's red squirrels, it's elk, it's moose. All of these depend on white-bark pine seeds."