The wildfires that burned large portions of Colorado this year will bring a benefit to individuals who enjoy the state’s golden beauty every fall. Colorado State University researchers studying the Rocky Mountain National Park area have discovered that fire helps to regenerate more stands of aspen.
Margot Kaye, doctorate researcher at Colorado State, and Tom Stohlgren, United States Geological Survey scientist at the Fort Collins Science Center and senior research scientist with the Natural Resources Ecology Laboratory at Colorado State, studied areas in Rocky Mountain National Park this year and found that aspen populations are far more prevalent than imagined even with changes in the climate and the high elk population.
When the study began, researchers thought that elk may be the primary cause of reducing aspen stands. But the researchers found that, while aspen at the low elevations are affected by elk, aspen stands at all elevations are being invaded by conifers. The study found that two-thirds of aspen stands were being overtaken by conifers.
"Fire suppression has played a role in lessening aspen regeneration and conifers have taken over aspen stands, but aspen are still numerous at this point and will be more so when fire returns to the area," said Stohlgren. "Aspen is well poised for regeneration after the fires of this year and in areas of future fires – which are not matters of if, but when."
The conifer invasion will be a long-range issue because that invasion has been happening across the central Rocky Mountains since the late 1800s. Old aspen stands are being replaced by conifers because aspen are shade intolerant and conifers are shade tolerant. In addition, aspen live 150-200 years, whereas conifers live 300-600 years and aspen are unable to establish under conifers.
With fire suppression, Kaye questions whether the remaining 40 percent of aspen stands not yet invaded by conifers could follow the same path as the invaded aspen stands.
Aspen need fire to move into new areas and grow very quickly into open spaces that have been burned. Without fire, the aspen are unable to start new stands.
"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," said Kaye. "In Yellowstone, for example, a lot of aspen have come into burned areas."
Before the 1994 fire in Pingree Park, north of the Arapahoe-Roosevelt National Forest, the area was a conifer forest. The fire that burned through the park was a high-intensity fire, destroying all trees in the area. Aspen currently are thriving in many of the park’s burned areas.