Fire as an Agent of Change
In 1994, Crater Lake National Park experienced 44 forest fires. These fires occurred throughout the park, from the Boundary Springs area to Sharp Peak and Annie Creek. Contrary to the widely held belief that fire in the forest is devastating and destructive, the fires at Crater Lake were beneficial products of a natural process eons old.
The vast majority of these fires during the 1994 fire season were under one tenth of an acre. A few grew to an acre or two, but less than five surpassed ten acres. One event, known as the Agee fire, was particularly interesting. This fire took nearly a week to find as the lookouts kept losing sight of the furtive smoke. Rugged topography south of the lookouts at Watchman and Mount Scott prevented a clear pinpointing of the smoke. It would pop up in the afternoon for a short time and then disappear, laying down in the tree canopy. When the smoke could be seen, it seemed to be on the southwest flank of Crater Peak.
A team of two firefighters were sent to locate the source of the elusive smoke. After four hours of climbing up and down the steep slopes, pushing through thick stands of snowbrush, Ceanothus velutinus, and sliding down scree, they stopped for lunch. In casually scanning the northern skyline, they saw something that made the drop their sandwiches and pick up their binoculars. They found the smoke, but it was not on Crater Peak. Although in line with the lookout tower on Watchman, the fire was on a ridge above the East Fork Annie Creek–over a mile and a half away! Since a deep canyon lay between them and the fire, they ate while hiking out. This turned into a near run so that they could get back to East Rim Drive and revealed itself, less than one and a half mile from headquarters. In an ironic twist, this fire turned out to be one of the closest to home.
Locating this fire on the park map is easy. Place your finger at Park Headquarters and follow East Rim Drive until it crosses the east fork of Annie Creek. Turn south and go about three quarters of a mile. On the west side of the creek, a steep slope runs up from the canyon bottom to the 6,000 foot level. You will see a ridge dividing the middle and east forks of Annie Creek. Along this ridge the fire burned slow but steady through a mature forest consisting of Mountain hemlock. Tsuga mertensiana, and Shasta red firAbies magnifica-procera. Upon discovery, the fire covered less than half an acre. The decomposing layer of needles and twigs smoldered and smoked heavily. Occasionally the crackling of burning live needles broke the quiet. Small seedlings, with their branches near the ground, were torching. This sent flames up as high as three or four feet, dying out as quick as they started.
There have been fires around what is now Crater Lake National Park for many thousands of years. Chances are, however, that what became known as the Agee Fire was the first in this part of the forest for quite some time. Far from being static and seniscent, the forest is constantly changing. Agents of change such as wind, precipitation, and fire alter species composition and stand density in the forest. These processes occur with varying frequency, depending on the type of forest. The frequency of fire in a given locale can be averaged to obtain its Fire Return Interval. This number can vary greatly throughout a forested area depending on the species makeup, altitude, aspect, topography, and prevailing weather patterns.
The forest where the Agee fire burned has a mean fire return interval of approximately 40 to 50 years. This means that the fire was burning on land that probably had not burned in the last 50 years or more. The variability among fire return intervals is usually very broad. For example, one researcher may find evidence of fires within the last decade, while another might find that a similar area had not burned for 120 years. The accuracy of these numbers usually depends on the extent of the survey.
The Agee fire burned for about eight weeks before being extinguished by snowfall in early November. During this time, firefighters made efforts to contain the fire within a fixed perimeter. With many other fires burning throughout the park at the same time, people and equipment were stretched thin. The weather remained hot and dry for several weeks after the fire started. Temperatures in the 80’s and humidity as low as 13 percent pointed to conditions normally associated with high fire danger. For the most part, however, the fire burned slowly through the underbrush and duff layer.
To study the effects this fire would have on the forest, plots were established in the path of the spreading flames to measure various components of the stand structure. These plots quantified the amount of burnable material, or fuel, and the quantity and density of live trees and shrubs. By reading the plots before and after the fire the change caused by the fire could be measured.
The results of these measurements point to the fact that fire is rarely a devastating event. Even the massive fires at Yellowstone in 1988 were agents of change that led to massive regeneration of the forest. The Agee fire, burning through a period of high fire danger, altered the forest in ways that were not as dramatic as all-consuming fire storms. This fire killed just 13 percent of the trees over ten feet tall, and only 41 percent of the trees under ten feet tall. The fire thinned out the young trees, providing better conditions for the growth of those that remained. What few large trees that were killed now allow for more sunlight to reach the forest floor where grasses and shrubs will sprout next year. During the fire many signs of elk were present an should be again once the forage returns. The large dead trees will also provide valuable habitat for birds, bats and insects. In topping out at 30 acres, the Agee fire left a forest changed but far from devastated.
Another change documented at the Agee fire involved deduction of the fuel load. This is composed of dead and down sticks and logs, as well as duff and needles. From a pre-burn level of 17.96 tons per acre, the fire consumed 14.53 tons per acre of fuel. This 81 percent reduction accomplished several things. Stored nutrients were released, making them available for future plant growth. In addition, such reduction can prevent the unnatural build up of fuels (which can lead to high intensity fires) that results from overzealous suppression of all fires.
Suppression of all fire at Crater Lake National Park was practiced for roughly 75 years. During that time much natural change in the forest has been stymied. When the snow began to fall in early November, there was still heat in the Agee Fire. By this time the fire crews were long gone and the fire cache was closed for the year. Snow fell gently and the temperature hovered around 30 degrees. Standing in the midst of the burn, I warmed my hands over embers in a slowly burning log. I thought about the regrowth, elk, and more fires in the summer of 1995.
James K. Agee, Fire Ecology of the Pacific Northwest Forests. Washington, D.C.: Island Press, 1993.
C.B. Chappell, Fire Ecology and Seedling Establishment in Shasta Red Fir Forests of Crater Lake National Park. M.S. thesis, University of Washington, Seattle, 1991.
Doug Lowthian is a seasonal firefighter at Crater Lake National Park.