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Restoring Fire to the Sequoias

CoverImage_

By BRUCE KILGORE
Originally published in National Parks & Conservation Magazine, Vol. 44, No. 277, Oct. 1970: 16-22

A crowd was gathered around the information desk at Grant Grove visitor center when the young man arrived. He walked quickly across the room and with a determined effort edged his way to the counter."Ranger," he interrupted, "I was just down at the Redwood Mountain overlook. We saw a lot of smoke coming out of that sequoia grove. There must be a fire."

Ranger Hefti glanced at his watch. A little after noon. "Pete's right on time," he thought to himself. But to the young tourist he said, "We appreciate your telling us about any fires you see in the parks, sir. But in this particular case, we know about the fire - you see, we started it."

Then, while a sizeable group of park visitors gathered arorrund, Ranger Hefti told a story about sequoias and fire - a story that rangers and naturalists at Sequoia, Kings Canyon, and Yosemite National Park have begun to learn by heart.

The rangers' reeducation of visitors to the importance of periodic, controlled fires is an outgrowth of the National Park Service's own reevaluation of how best to preserve sequoia groves. For, like the park visitors, most of whom are now conscientious followers of Smokey the Bear's admonitions to prevent fire, early park officials were dedicated to a policy of total fire suppression in order to preserve the forests as they found them. In 1865, just one year after Yosemite was set aside as a state park, Frederick Law Olmsted was worried about the damage caused by fires sweeping upon the Mariposa Grove of sequoias each year from adjoining country. And early administrators wanted to construct fuel breaks to stop fire from entering the grove.

The logic of this early policy is easy to understand. The administrators were charged with preserving a forest, and so they stopped forest fires. These first custodians can be forgiven if they did not realize the living, moving nature of the sequoia groves. One's initial impression of them is of immensity, timelessness, changelessness. But sequoias are changing, living things. Through the aeons they had known fire and had learned to live with it. There are huge, charred scars on the trunks of many mature sequoias, evidence of past fires, but few large sequoias appear to have been killed by fire. Research has shown, in fact, that periodic light fires have played an important role in the life of the forest.

Careful observers have pointed out the importance of distinguishing among various types of fires and their effects. Early descriptions of the Sierra Nevada by John Muir, Galen Clark, and others lead to the conclusion that these forests apparently were subject to frequent ground fires that made them practically immune to crown fires. The low ground fires tended to rid the forest floor of thickets of small trees and the accumulation of branches, cones, needles, and humus. By clearing away these high fuels, ground fires also lessened the likelihood of huge sheets of fire that could kill mature trees by destroying the top foliage, or crown. While on his famous trip through most of the sequoia groves in 1875, John Muir saw a fire approach and enter a grove of giant sequoias in September, the driest time of year:

"The fire came racing up the steep chaparral-covered slopes... in a broad cataract of flames.... But as soon as the deep forest was reached, the ungovernable flood became calm like a torrent entering a lake, creeping and spreading beneath the trees.... There was no danger of being chased and hemmed in, for in the main forest belt of the Sierra, even when swift winds are blowing, fires seldom or never sweep over the trees in broad all-embracing sheets as they do in the dense Rocky Mountain woods and in those of the Cascade Mountains of Oregon and Washington. Here they creep from tree to tree... allowing close observation...."

Early superintendents at Sequoia National Park recognized the growing fire hazard resulting from fire suppression, and a few attempted to remedy the situation. One area was lightly burned over in 1904 to remove "coniferous rubbish." In 1918, more than 100 acres of the main groves were cleared of inflammable fallen trees, stumps, and brush.

These early attempts to preserve the fire process, however, were cut down by critics who said, "You don't know enough to make sound decisions on this type of management, and stopping all fires is less expensive anyway." As a result, total suppression of fires became National Park Service policy for nearly 40 years.

Sporadic criticism of this policy had little effect until 1955, when a disastrous wildfire swept up from the McGee ranch west of Grant Grove. Within a short time the McGee fire had devastated more than 13,000 acres of brush and forest and had threatened the Grant Grove sequoias. Soon thereafter, studies and publications by Dr. Harold H. Biswell, Dr. Richard J. Hartesveldt, and others began to point up the threat to mature sequoias posed by continued fire suppression. The document of greatest significance to Park Service policy was the Leopold Report of 1963 (National Parks Magazine, April 1963) which pointed out that "much of the west slope [of the Sierra] is a dog-hair thicket of young pines, white fir, incense-cedar, and mature brush a direct function of over-protection from natural ground fires." The report suggested that "A reasonable illusion of primitive America could be recreated, using the utmost in still, judgment, and ecologic sensitivity." This report has been largely adopted as Park Service policy, bringing about a major reorientation in attitudes toward fire suppression.

 
Figure_1_YOSE_ConfederateGroup

Yosemite's Confederate Group in 1890 and 1959. Without fires, fir thickets have grown up that ironically may fuel a crown fire fatal to the Big Trees. Scars were left by lighter ground fires. (Mary and Bill Hood have provided a number of such before-and-after photographs of great value to research.)

In line with this modification of general Service policy, Park Superintendent John McLaughlin of Sequoia and Kings Canyon National Parks and Chief Ranger Peter Schuft outlined a program aimed at restoring natural environtmental conditions to the sequoia groves in these parks. Director George Hartzog and former Chief Scientist A. Starker Leopold fully supported this important effort. My own part in this program began in 1968 when I joined the Office of Natural Science Studies and was stationed at Sequoia and Kings Canyon. My assignment was to develop a research program to support the management needs of these Parks. First priority has been given to studying natural fire in sequoia groves and developing techniques to simulate the impact of fire and thus restore the natural environment. Our preliminary program of research and management has been based, necessarily, on certain assumptions regarding the role of fire in giant sequoia groves. These assumptions have yet to be proved conclusively, but they are gaining acceptance and include the following:

  • Fires have occurred frequently over past centuries in the virgin forests of California, including the giant sequoia groves.
  • Fires have always been an integral part of the successional mosaic we find in much of our mixed conifer forest on the west slope of the Sierra Nevada.
  • Fires performed an important function within the ecosystems in which they operated by bringing about a quick conversion to more readily available forms of nutrients tied up in trunks of trees, "down" logs, branches, and litter.
  • Periodic lightning fires reduced the amounts of ground fuels and understory vegetation in a way that decreased the chance of catastrophic fires that destroy entire plant communities and require primary successional stages to begin again. As such, fires rarely were hot enough to kill mature sequoias with their thick bark and tenacity for life. Fires removed litter and duff in a way that exposed mineral soil from time to time apparently a necessary event for germination of various seeds, including those of the sequoia.
  • The same relatively mild fires that set succession back somewhat, that gave us the mosaic of age classes and vegetation types, that favored sequoias over white fir, that exposed mineral soil for sequoia seeds, and that cleaned up forest fuels, also favored browse species for deer by stimulating sprouting shrubs and by cracking seed coats of other species.

These assumptions underlie our present management program for giant sequoias. They are not accepted by everyone as facts. Some may prove to be wrong. But they are the basis for the hypothesis on which we are now working. That hypothesis, briefly, is that:

 
Figure_2_JohnLounsbury_TestFire

Ranger John Lounsbury sets fire to a test plot.

In all probability, the giant sequoia survives today because of the role fire played in its life cycle. Fire must be restored, as nearly as possible, to that natural role if we are to continue to have giant sequoias through the next many millennia. Fire probably burned under sequoias about every 10 to 20 years. After longer periods, there is danger that the fuel build-up will allow mature trees to be killed. Until we are sure that fires that start by natural ignition will not threaten groves or human life, we will have to try a policy of prescribed burning of the understory vegetation and accumulation of down logs and litter to bring the groves back to more natural conditions. At the same time, research must determine the historical role of fire in these forests so that our management techniques can gradually be guided by additional knowledge of the natural periodicity and intensity of fire.

Our assumptions and working hypothesis result from past and current research conducted both by the Park Service and independent scholars. We have received invaluable information, for example, from the study of sequoia natural history by Dr. Hartesveldt and his colleagues at San Jose State College, California. They are giving special emphasis to cone and seed production of the species, to seedling survival under various habitat situations, to the role of chickaree squirrels in cutting cones and releasing seeds, and to the relationship of various invertebrates to the reproductive phases of the sequoia life cycle. As part of their work, these men established several small plots on reasonably level sites in the Redwood Mountain grove. Plots varied from 4 to 8 acres in size, and half of each was manipulated by felling snags, piling logs with a bulldozer, and burning. Many seedlings came in following manipulation and burning; of course, large numbers of them soon died. The progress of the survivors is being followed with great interest. Survival seems to be related to specific substrate and moisture conditions.

The place of sequoias in plant succession is important in understanding the long-term regeneration problem that results from fire suppression. Dr. Hartesveldt explains that because oldest trees are dominant by sheer size wherever they grow, the sequoia is often thought of as a climax species. But young sequoias need sunlight. Only when saplings have overtopped the rest of the canopy and have thus solved their light problem do they grow well where tree density is high. So the sequoia belongs to a subclimax stage of succession. At a 1967 fire ecology conference, Drs. Hartesveldt and H. T. Harvey stated that without fire or other kinds of disturbance sequoia seeds either do not germinate at all or seedlings do not survive if germination does occur. The problems are lack of mineral soil, inadequate soil moisture, plus low light conditions under a dense forest canopy and understory.

A second series of studies is aimed at finding ways to reduce the unnatural accumulation of forest fueIs in sequoia groves without damage to the environment. This project is being carried out by a group of researchers led by Dr. Biswell at the University of California in Berkeley. The work currently is being completed at Whitaker's Forest, a University-owned experimental area in the western part of the Redwood Mountain grove. In 1964, they established four 20-acre plots where they measured tree, shrub, and herbaceous vegetation and took censuses of bird and mammal popu1ations. In 1966, the research team treated two of the four plots by cutting, piling, and burning small white fir and incense-cedar between the heights of 1 and ll feet. They also cut and burned larger standing dead trees, along with part of the fallen logs, branches, and litter that had gathered during past decades of effective fire suppression. In areas of maximum fuel build-up, they burned some 22 tons per acre, including nearly 1,000 living trees and more than 500 dead trees per acre. Costs of manipulation ranged from $114 to $146 per acre. In related studies, Dr. Biswell found that 1 to 3 tons of litter per acre falls each year under the main five tree species of this forest. He also learned that fire increased seedling survival of white fir as well as of giant sequoia. The young fir, however, came in fairly strongly whether or not an area was burned, whereas establishment of sequoia seedlings usually requires a seedbed prepared by fire or other disturbance that removes the duff.

In wildlife studies, fewer deer mice were found on treated plots the first year after manipulation, but there was no apparent impact on the numbers of chickarees. Browse species for deer were favored by the program. Through repeated censuses of bird populations, I found that numbers of nesting flycatchers and robins increased following treatment, although three species of ground- feeding or ground-nesting birds disappeared. There was essentially no change in numbers of the other 25 nesting species.

The bulk of my current research effort is concentrated in three studies. Two of them involve monitoring the impact of fire used in current management efforts in a red fir forest and a giant sequoia forest. In the third, more basic study, I am looking for a more complete understanding of the historical role of fire in the mixed conifer forest.

The two immediate projects deal largely with documenting the vegetative, soil, litter, and vertebrate population changes that accompany prescribed burning in a giant sequoia (and red fir) forest. We burned in the red fir forest in 1968 to learn more about techniques of applying prescribed fire in areas of heavy down fuel and dense fir thickets but without having to face the fire hazard presently found in the giant sequoia groves. Based on this successful experience in the red fir forest, however, a burning management program was begun in 1969 on the ridge of Redwood Mountain. Study plots have been established, and part of them will be burned this year to provide objective measurements of the changes caused by fire alone with essentially no preburn preparation.

 
Figure_3_Kilgore_Sardus

Author, hatless, and Ranger Maurice Sardus measure forest litter accumulation.

My study of fire history will try to gather better information on frequency of fires in the mixed conifer forest of these parks. Some fire dates will be read from stumps of trees cut on adjacent national forest and private lands. Wherever possible, we will tie in burn scar dates on stumps with agency fire records to determine how often fires burned a given pine, fir, or incense-cedar. We expect to draw heavily on the extensive work on the physical and chemical nature of fuels and on fire behavior already completed and under way by researchers at the Forest Service fire laboratories at Riverside, California, and Missoula, Montana.

 
Figure_4_FireScars

Evidence of frequent fires of low intensity is recorded by the annular rings and fire scars in a cross section of ponderosa pine (Pinus ponderosa). This tree managed very well without man's interference, surviving, on the average, a fire every six years from 1832 until 1958.

I intend to make a special study of any lightning fires that are started during the next few years particularly in our "let-them-burn" zones at higher elevations. As the name implies, these zones include areas that we feel can be restored most efficiently by letting lightning fires burn naturally. We have followed this policy for the past 2 years at elevations above 8,000 feet in the Middle Fork of the Kings River, and we have now extended the policy to higher elevation sections of the South Fork of the Kings and the Kern River drainages. But at lower elevations, fir thickets, together with large quantities of needles, cones, and branches, seem to be too great a fire hazard even for mature sequoias. A fire that begins in the 4,000- to 7,000-foot chaparral-pine-mixed conifer zone on a dry August afternoon could kill mature sequoias as well as most other trees in the area. Such losses would be unacceptable in national parks. So we have to find other ways to return to natural conditions in the groves.

The system of careful cutting, piling, and burning of small trees and litter worked out at Whitaker's Forest was successful on small areas. The Park Service has recently used this technique on a 20-acre section of the Mariposa Grove in Yosemite. However, it seems essential that the Park Service develop less expensive and more natural means of using prescribed fire to simulate natural fire results.

 
Figure_5_Fireline_HoseLays

Firelines and hoses confine blaze to test area.

Because of the tremendous fire hazard that exists west of the Redwood Mountain Grove, management feels it cannot wait for all the research answers to come in before it begins burning. Therefore, as a first step in the restoration program, a reduced fuel zone was begun last year along the west boundary of this grove. A great deal of preburn preparation was carried out before any fires were set. Obviously no one wanted any chance of fires getting out of hand in this first major effort. So a number of 7-acre sectors were completely surrounded by hand-built fire lines. White fir and incense-cedar less than 9 inches in diameter were cut down. Snags, excepting sequoias, were felled. Jeffrey and sugar pine were limbed up to 8 feet. Hand lines were built around most sequoia trees. Fire hose was run to all sectors, and charged lines were available for use at any point along the sector perimeters. Many sequoias were wet down before burning began. In later sectors, sprinklers were used to prepare a wet line in lieu of building a fire line by hand. A total of 100 acres was burned between August and November.

During 1970, the reduced fuel zone will be extended further around the Redwood Mountain section of the Park. In time, this will take in the complete west and south boundaries of the Park, giving the front country some protection from fires that start in the lower elevations of oak woodland and chaparral zones. Once this zone is established, preliminary park management plans call for prescribed burning - without elaborate preburn preparation - in specified zones within the Redwood Mountain Grove. The program calls for some 100 acres or more to be burned each year over a period of years. The rotation time may be something like every 10 to 20 years, depending upon research results in the next few years. Some groves of sequoias will be left completely alone, letting natural force play their role. There is interest on the part of various scientists in letting the unnatural climax community develop in at least one area. For this particular small area, complete fire suppression would continue to be the policy.

The Redwood Mountain program and its extension to other parks represent our main effort in giant sequoia management and research, but we are also investigating other projects. One group of problems includes soil compaction in the areas of visitor concentration and the general deterioration of the appearance of the environment around sequoias in areas of heavy human foot traffic. In certain sites, the unnatural forest edge effect along reads has led to thickets of fir that block visitor views of mature sequoias.

A unique problem with fire overtones has been identified in recent years by a naturalist at Giant Forest. He finds what seems to be correlation between increased numbers of a small insect, the carpenter ant, and numbers of people visiting sequoia groves. Although the ant always may have been a member of the sequoia-mixed conifer forest eco- system, its role of establishing galleries in the heartwood of the sequoia has been noted only in recent years. The researcher believes that artificially high numbers of ants and consequently of ant chambers in giant sequoias have been stimulated by the special food materials provided by visitors to the groves.

The possible management significance of the chambering of these ants was made clear in August 1969 when a sequoia fell in the Hazelwood Picnic Area of Giant Forest. On close examination, it was noted that six factors probably were involved in the tree's falling one of them being extensive chambering by the carpenter ant at the point of breakage. The other five factors may have been of equal or greater significance. There is a definite possibility that fire suppression activities have played a role in allowing an abnormal build-up of carpenter ants in certain sequoia groves. The National Park Service hopes to support a study of the role of these ants in the sequoia ecosystem so that we can learn more about the ecological relationships that may exist between numbers of humans, sandwiches, carpenter ants, woodpeckers (which prey on the ants), fire suppression activities, and giant sequoias.

In dealing with all the problems that beset sequoia groves, we must approach the assignment of restoring natural environmental conditions with humility and great ecologic sensitivity. Some will feel we are arrogant when we try to second-guess the current stage of plant succession. Others may feel we are becoming gardeners instead of guardians. Our guiding principle should be the maintenance of naturalness. And whenever and wherever possible, the best way to restore a semblance of native America may be to let natural forces run their own course.

Dr. Bruce M. Kilgore, research biologist with the Park Service's Office of Natural Science Studies, is stationed at Sequoia-Kings Canyon National Parks, Three Rivers, California. He has spent several years studying the impact of controlled fire and vegetation management on breeding birds in a giant sequoia stand. Dr. Kilgore previously served as managing editor for the Sierra Club and as editor of National Parks Magazine.

Did You Know?

Speleothem, a cave formation.

Crystal Cave, a marble cavern, is a complex maze more than 3 miles long. Parts of it are open via tours. Many varieties of beautiful speleothems decorate the cave, including rarely formed "shields" and "raft cones." A number of unique species of animals live in the cave and its stream. More...