PORTLAND, Ore. March 9, 2006. A recently
published study in the Canadian Journal of Forest Research indicates
that fuel reduction treatments should simultaneously take place
in the overstory, understory, and on the ground to adequately reduce
fire severity. Thinning trees without treating surface fuels does
not reduce mortality adequately because mortality can occur from
hot fires on the ground, as well as fires that burn through the
The study, “Fuel Treatments Alter the Effects of Wildfire
in a Mixed-Evergreen Forest, Oregon, USA,” is co-authored
by Crystal Raymond, University of Washington and David L. Peterson,
Pacific Northwest Research Station/USDA Forest Service.
The 2002 Biscuit Fire in southwestern Oregon impacted forest
resources, threatened lives, and costs millions of dollars to suppress.
also provided a rare opportunity to study previous fuel treatments
(thinning of forest stands and underburning of surface fuels) to
see which projects actually reduced tree damage when the Biscuit
Fire burned through.
The research team measured the effects of fuel
treatments in a Douglas-fir—tanoak forest. Scientists were
fortunate to have data collected before the Biscuit Fire with
which to directly quantify
the relationship between forest structure and fire severity. The
effectiveness of two fuel treatments at reducing tree damage and
mortality was measured by comparing treated and untreated forests
that burned in the fire.
The number of trees killed in the Biscuit Fire was highest in the
thinned areas we studied, most likely due to slash left after the
thinning treatment,” Raymond explains. “Overstory tree
mortality was lowest in sites that were thinned and then underburned,
and moderate in sites that were not treated prior to the Biscuit
Fire. Thinning ladder fuels is just the first step in effective
fuel treatment for most forests.” Ladder fuels are the small
trees that carry fire from the ground to the overstory tree crowns.
Fuel treatments intended to minimize damage to the overstory are
more effective if fine fuels on the ground are reduced following
removal of understory trees. “We have known this in principle
for many years,” says Peterson, a research biologist at the
Station, “and the Biscuit Fire gave us a chance to validate
the effectiveness of on-the-ground fuel treatments.”
agencies are mandated to reduce fuel accumulations in dry forests
throughout the West. However, studies like the one conducted
by Raymond and Peterson that validate the effectiveness of fuel
treatments are rare. “Data from the Biscuit Fire provide
new scientific evidence that will help improve techniques for treating
fuels. As more wildfires burn through treated areas, we will have
additional opportunities to document how well those treatments
are working,” adds Peterson.
To read the entire journal article, visit http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_abst_e?cjfr_x05-206_35_ns_nf_cjfr12-05.