Benefits Of Prescribed Burning Illustrated By Colorado State University Researcher's Study Of Boulder's Open Space
Friday, April 18, 1997
FORT COLLINS--Burning dead and dying timber in parts of
Boulder's Open Space and Mountain Parks area increased plant
species and pruned dense ponderosa pine forests that pose a
serious wildfire threat to nearby homes, a Colorado State
University study found.
The two-year study, led by forest sciences professor Rick
Laven, focused on the effects of prescribed burning--the
intentional setting of small fires to help clear overstocked
forests of debris--on two open space parcels where ponderosa pine
forests border grasslands.
The study found that prescribed burns in these two specific
areas thinned out dominant plants so that other plant species
could emerge, resulting in a healthier and more diverse
ecosystem. It also proved a useful method in thinning out forest
debris that has accumulated after years of fire suppression.
"Fire triggers a thinning and rejuvenating process in
ecosystems, and also maintains a border between ecosystems,"
Laven said. "Without fire or thinning forests by mechanical
means, a wildfire is likely to be much more intense and harder to
control. This is especially a concern for Colorado's Front Range,
where so many people have built homes in these areas within
grassland and ponderosa pine ecosystems."
Operating under a $50,000 grant from the City of Boulder's
Open Space and Mountain Parks Department, Laven and graduate
research assistant Sarah Gallup measured tree densities and
inventoried plant species before and after prescribed burns in
the two areas. Unburned areas were used for comparison.
The two burns behaved differently, one creeping through
grass at low intensity and the second burning at a much higher
intensity. A year after the plot was burned by intense fire,
researchers documented an increase in plant species compared with
other plots, while grasses decreased. The area with less intense
fire showed a decrease in plants that reproduced only by seed.
Laven said historical photographs of Boulder's open space
show that prior to human settlement, similar areas were
apparently thinned out naturally with low-intensity surface fires
that may have occurred as frequently as every 40 years.
As urban populations increased and fire was continually
suppressed, the ponderosa pine ecosystems became increasingly
dense and began to encroach on native grasslands. That changed
the number of native plants and other plant species present in
the two ecosystems, Laven said.
Laven pointed out that suppressing fire in lower-elevation
ponderosa pine forests, such as those in the study, posed more of
a wildfire threat than suppressing fire in higher elevation
forests marked by species such as lodgepole pine or spruce.
"At higher elevations, hundreds of years often pass between
forest fires because there's greater moisture and the climate is
less conducive to frequent burns," Laven said. "At lower
elevations, we suspect that fuel build-up on the forest floor
occurs much faster. By suppressing fire, more woody debris is
available to act as a fuel source."
Laven's study dovetails with a recent debate in Congress
over President Clinton's proposal to burn as many as 1.3 million
acres in national forests to weed out areas overloaded with
fallen timber. The U.S. Forest Service suggested that low-
intensity fires will help reduce the threat of wildfires that
quickly grow out of control.
Laven cautioned that his study focused solely on the effects
of prescribed burning in two specific areas within Boulder's open
space, and cannot be used to reach a general conclusion about the
use of fire.
"The effects of fire are not easy to generalize. Each fire
behaves differently and conditions are different, which makes
replicating fires for experiments extremely difficult," Laven
said. "We hope this study adds to our limited knowledge of the
ecological consequences of prescribed fire and helps managers
choose the most appropriate land management options."
Laven has studied the use of fire and forest ecology for
more than 20 years and is co-author of "Introduction to Wildland
Fire," a book covering all aspects of prescribed burning and its
ecological effects.
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