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Research / Discovery

Inferno in the pines

January 12, 2010
By Paul Miller

For a layman, watching lodgepole pine burn in the name of research is an exercise in conflicting emotions. For researchers, though, it's a prime opportunity to explore the interaction between fire and mountain pine beetles, an insect about the size of pencil lead that's been killing lodgepole, ponderosa, and limber pines at a stupefying rate throughout Colorado.

Test burns explore beetles reaction to flames

National Park Service Alpine Hot Shots firefighters torch a tree killed by bark beetles in Horseshoe Park in April 2009, as a part of collaborative research between the National Park Service and CSU on fire fuels and bark beetle management.

In Rocky Mountain National Park, just such an exercise unfolded on a calm April day as researchers from Colorado State and the park gathered at Little Horseshoe Park to torch trees in the name of science.

In addition to CSU’s Monique Rocca, assistant professor of wildland fire science, and Bill Romme, professor of fire ecology, the group included some 10 firefighters and CSU students toting incendiary gear and research material. On that spring day, conditions were close to ideal for the test burn: not much wind, mild temperature, and snow on the ground.

After briefing the crew, Mike Lewelling, fire management officer for the park, told a couple of members of the Alpine Hotshots, an interagency fire organization, to ignite the torch – a thin metal rod about 7 feet long that kicks out a few million BTUs of propane-fed flame. The torch roared like a jet engine as Eric Jones, one of the hotshots, held the flame for a few seconds to the low branches of a dead lodgepole.

In moments, orange flames engulfed the dry, brown needles of the tree, and heat cascaded outward. For a casual observer, the crackling, burning sound hit a visceral nerve – a flight response was hard to contain. But Rocca, Romme, and the others were riveted on the burning tree as flames rolled upward and consumed the crown. Fifteen seconds later, the flames and heat were gone, leaving the 40-foot tree smoldering with white smoke.

Bugs in the system

This nascent research is helping to address several questions including the flammability of pine crowns, mechanisms of pine seed dispersal following beetle attack, and survival of beetle larvae following burns.

“The beetles and fi re have both been around for eons,” Romme said. “In fact, lodgepole cones are serotinous – fire is required to open them and release seeds. But what’s unknown is how the current severe beetle outbreak will impact fire behavior in beetle-killed stands.”

“People who love and recreate and live in Colorado are very interested in knowing what forests will look like 30 or 40 years from now,” Rocca said. “It may be a very different landscape. The lodgepole will come back, we believe, but we’re likely to see younger trees and perhaps a more diverse suite of species growing in the remnants of millions of acres of beetle kill.”

Many questions

Professors Bill Romme and Monique Rocca discuss research observations during a controlled burn experiment.

Many questions remain to be answered, Lewelling added.

  • What are the effects of drought on the fire regime?
  • Can dead swaths of trees be used as fire breaks?
  • How can areas in the park best be protected for the public’s interest while maintaining the natural order of bugs and fire?

“The National Park Service works to protect life and property while allowing natural processes to unfold as they always have,” Lewelling said. “But the beetle epidemic has pushed some programs into high gear. When we first mentioned the fire research projects to Monique and Bill, they showed a lot of interest and have been contributing with some great ideas.”

Last year, Rocca and Romme conducted studies on the west side of the park, where the beetle outbreak is well established, and have been returning there to continue research. Beetles have been moving north through the Kawuneeche Valley and east of the Continental Divide and are now rife in Estes Valley and the Highway 7 corridor. Outbreaks aren’t uncommon along the Front Range.

High-country firing line

The fire crew moved to other trees, all selected and tagged by Rocca and Romme. The torch flared again, and varying rates of burn were recorded by CSU students.

Dead needles on beetle-killed trees remain intact for two to five years before falling to the forest floor. An unknown factor is how fire behaves on a continuum of trees newly dead or dead for five years or more. In fact, during the test burn, some lodgepole that looked highly flammable didn’t flare up as intuitively expected.

“We’re testing different ideas,” Romme said, while a tree behind him sputtered with anemic flames. “What percentage of remaining needles makes a tree more or less flammable? Do crown fires in the winter stimulate cones to break open as they would during a summer fire? We have a ways to go before we more fully understand what’s going on.”

Tiny bugs have been chewing through forests for centuries

Behind the research lurked the tiny bugs, one of about 17 species of native bark beetles mostly unseen in the landscape of the forest.

“We’re curious about whether beetles survive if their host tree is burned,” Rocca said. “But even if they don’t survive, we wouldn’t expect fire to be a practical population control measure because we couldn’t burn enough trees to put a dent in the population.”

In a sense, Romme was almost admiring of the mountain pine beetles. After all, Dendroctonus ponderosae have been chewing through forests long before humans populated the continent.

“We may never discover all the answers to epidemics like this,” Romme said. “But nature will eventually balance things out – or at least strike a balance that we humans see as more acceptable.”

Originally published in Colorado State Magazine, Fall 2009.