Fall colors ignited by wildfires
It’s another one of Mother Nature’s strange relationships, but wildfires clear spaces for aspen groves to re-sprout. In many of Colorado’s forests, aspens, which need more sunlight, are now getting crowded out by taller, heartier conifers, says Tom Stohlgren, a scientist with the U.S Geological Survey who works with Colorado State University.
“Aspen is well poised for regeneration after the fires of this year and in areas of future fires – which is not a matter of if, but when,” Stohlgren says.
Aspens live about 150 years and grow to about 60 feet. But lodgepole pines and other conifers grow about 20 feet higher and live more than twice as long. Thus, the pines can bury the aspen in shadow and prevent them from re-sprouting, Stohlgren says.
“Fire really can initiate new re-sprouts because aspens can seed into burn areas,” Stohlgren says. “Anything that opens up the canopy is good for aspens because aspens love light. That why you see it on meadow edges.”
Locally, foresters have been counting aspen groves to check if Mother Nature needs a little help in regenerating the trees that grow the valley’s most colorful leaves.
“The aspens are getting up there in age and we’re still trying to figure out if they’ll re-sprout on their own or if they need some kind of disturbance,” says Bob Currie, a forester at the Holy Cross Ranger Station in Minturn.
Early indications from surveying the forests surrounding West Vail are that the aspens are in good health, Currie says.
“My spin is they’re fine,” he says. “We’ve got a lot of aspens. What you’re seeing for color are the blocks of aspens, and those are pretty intact. We’ve got a long way to go.”
The severity of the threat that is likely to develop in coming decades is still being judged. But that threat is not being ignored, Currie says.
“It would be good to get some re-sprouting because it has been a long time since there’s been any disturbance,” Currie says. “You can walk through anywhere in the forest and the aspens are dying. In some places the aspen and conifers are neck-and-neck.”
Foresters will determine whether they need to give the aspens a push, Currie says.
“We want to see if they’re healthy and whether we need to take action or just let them grow,” he says. “You just try to pick and pluck some areas where you want them to re-sprout for wildlife or for the landscape.”
Aspens are thriving in areas of the west that have been burned by wildfires, says Margot Kaye, a former Colorado State researcher who worked with Stohlgren.
“In Yellowstone National Park, for example, a lot of aspen have come into burned areas,” Kaye says. “In areas that have burned this year, it will be interesting to see how much of those areas will be taken over by new aspen stands.”
Stohlgren’s study found that about two-thirds of the aspen stands in Rocky Mountain National Park are being invaded by conifers. But counts done in the park turned up more aspens than scientists expected, Stohlgren says.
“There are just far more aspens than we really thought there were out on the landscape,” he says. “Fire suppression has played a role in lessening aspen regeneration and conifers have taken over aspen stands, but aspens are still numerous at this point and will be more so when fire returns to the area.”
For every hectare – 100 yards by 100 yards – of forest there’s an 80 percent chance there’s one aspen stem or clone in Rocky Mountain Park, Stohlgren says.
“Fire sets back the forest a little bit, and species like aspen can regain a foothold,” Stohlgren says.
Colorado’s fall colors get a lot of oohs and ahs. But many people on the East Coast of the country, particularly in leafy New England, would argue their colors are much more spectacular.
“I’d take the Rockies any day,” Stohlgren says. “In the East, they just don’t have elk bugling in the background.”
Matt Zalaznick can be reached at 949-0555, ext. 606, or via e-mail at firstname.lastname@example.org.