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The Influence of Fire in Coast Redwood Forests 1
Stephen D. Veirs, Jr. 2
Abstract.--In its northern range redwood vegetation is
influenced by fires of differing intensity. Relatively hot
fires appear essential for the establishment of Douglas-fir
(Psuedotenga menziesii) trees as discrete age classes. Coast
redwood (SeJGoia sem ervirens) and several lesser associates
are success 1 with or wit out fires. The effects of two
fires are described.
INTRODUCTION
frequency and intensity is low. Greater fire
frequency and intensity along with difficulties
of seedling establishment appear to limit the
inland development of redwood. Other lesser
associates of redwood and Douglas-fir occurring
in these forests; western hemlock (Tsuga
heterokhylla), grand fir (Abies grandiSf, and
tan oa (Lithocarpus densiflorus) all, like
redwood, appear to be successfUl in the presence
or absence of fire.
The influence of natural fire in old growth
redwood forest is poorly understood. Redwood
(Sequoia sempervirens) stands have been described
as even-aged, (Cooper, 1965), and all-aged (Fritz,
1929), a climax species (Weaver and Clements,
1929) and as a subclimax, fire dependent species
(Cooper, 1965, Stone et.al. 1969). Roy (1966)
described fire as the worst enemy of redwood. A
better understanding of the role of natural fire
in redwood forest vegetation is necessary to guide
long-term management of old grm'lth redl'lood forests
now largely confined to parklands. Restoration or
perpetuation of the natural processes which dominate this and related vegetation types, or artificial management to mimic these processes depends
upon a better information base than is now available. Research has been carried out in and near
Redwood National Park to gain needed information
for management of this superlative natural ecosystem. The results of part of this work (Veirs,
1979) suggest that redwood maintains its dominant
status in the northern portion of its range with
or without the influence of fire. On the other
hand, Douglas-fir (Psuedotsuga menziesii), the
major canopy associate of redwood, appears to
occur only as discrete age classes of trees
(Table 1.) established following fires.
Here I examine the relative impact of two
fires on old grol'lth redwood vegetation and
subsequent tree establishment.
METHODS
Stand histories have been developed (Veirs,
1972, 1979) for several hectare plots by sampling
before and after timber harvest. Tree species,
density and ages were obtained directly and fire
scars dated by growth ring counts. Data from one
stand with a well-defined low intensity fire which
occurred about 1880 is compared with data from
stand burned in October, 1974. Mortality and
establishment was determined by counting overstory
trees and oy systematic sampling of seedlings.
Tree ages on the latter site are inferred from data
available from a logged area nearby and from
sections removed from fallen trees.
In moist low elevation sites the return
interval for fires which open the redwood canopy
enough to allow Douglas-fir seedling establishment
and survival may be as long as 500-600 years, on
intermediate sites from 150-200 years, and on high
elevation interior sites 33-50 year intervals.
Redwood stands are best developed where fire
DESCRIPTION OF THE STUDY SITES
The 1880 fire site was located east of
Crescent City, California in the Mill Creek basin.
The area sampled (2.47 acres) was a moist westfacing slope, elevation 250-350 feet. The overstory was largely redwood with a few Douglas-fir
and there was a dense understory of western
hemlock with few plants in the herb layer. This
fire may have been intentionally set by a
prospecting landowner to expose the soil surface,
or it may have occurred naturally.
1Paper presented at the Fire History Workshop,
(Laboratory of Tree Ring Research, University of
Arizona, Tucson, Arizona, October 20-24, 1980).
2stephen D. Veirs, Jr. is Research Scientist,
National Park Service, Redwood National Park,
Arcata, CA.
93
Table
Location
1.~-Age classes of Douglas-fir occurring in
coastal redwood vegetation, Humboldt and
Del Norte counties, California.
Distance from
Pacific Coast Elevation
(miles)
Near Klamath River
Near Klamath River
High Prairie Creek
Mill Creek
Redwood Creek
Redwood Creek
Redwood Creek
Eel River (Fritz,l929)
1.2
1.9
2.8
3.0
5,0
5.4
5,9
(feet)
800
300-500
1300-1500
250-350
600-800
600-800
700-900
Aspect
(Drection
slope faces)
Ridgetop
N
sw
WSW
ssw
WNW
w
Age Classes
Years
250
250
50,75,100,190
575
200,275,350,450,575
400,550
300,400,500
150,300
two Douglas-firs by burning up rifts and resin on
the bark, but damage to living pDTtions appeared
limited. No crowning occurred. In spite of an
extremely dry summer, low wind conditions and a
slight inversion combined to yield a fire of
relatively low intensity. Rain a few days later
put out any smoldering materials including the
aerial fires in stems.
At the time of sampling the overstory redwoods
ranged in age from 400 to 1200 years, all the
Douglas-fir were approximately 550 years old. The
understory hemlocks comprised two distinct groups;
a few older trees 180-220 years and many young
trees all less than 93 years of age.
The 1974 fire site was located east of Orick,
California in the Redwood Creek basin. The area
burned was 6.0 acres on a moderately dry slope
between 600-800 feet in elevation. The overstory
was largely redwood with a few Douglas-fir; the
redwoods ranging broadly in age from a few to
1450 years. The Douglas-fir are thought to be in
two age classes between 200 and 400 years of age.
The subcanopy and understory was largely hemlock
with two probable age classes approximately 75
years and 200 years old. Tan oak and grand fir
also occurred as associates. This fire was
probably ignited accidently by forest workers
falling nearby timber.
RESULTS AND DISCUSSION
Following the 1880 fire, hemlock seedlings
(Table 2.) became abundantly established forming
a dense subcanopy which has limited the
reestablishment of herbs, shrubs and trees to the
present time. A few redwood also became
established but none of these occurred on the
sample site. The fire caused no significant
changes in the canopy composition and the understory of hemlock may also have been essentially
unchanged. The stand bore approximately one-half
fire scar per overstory tree with no well-defined
pattern over an average life of about 800 years.
Clearly this mesic stand has had relatively little
impact from fires during the past several hundred
years. What will happen as the understory
hemlocks mature and senesce and when overstory
redwood and Douglas-fir mortality occurs remains
to be seen.
FIRE BEHAVIOR
While the time of year the 1880 fire burned
is unknown, there is evidence to suggest that it
occurred under conditions which yielded a low
intensity fire. Hemlock, well-known for its
sensitivity to fire, was not always killed. About
five hemlock per acre survived (Table 2.). Several
of these surviving hemlock displayed evidence of
release following the fire; increased diameter
growth rates were observed on survivors. The
absence of deadfall, the presence of a largely
intact canopy of old red\t~ood and Douglas-fir
(cover approximately 90%) and the absence of a
well-defined scar record of the fire also
suggests low intensity.
The 1974 fire, in spite of its apparent low
intensity caused complete mortality among the
small and large hemlock alike, with relatively
little mortality among all other tree species
(Table 2.). Similarly, the strong establishment
of hemlock, redwood and Douglas-fir seedlings is
remarkably different from the 1880 fire. It is
possible that the very dry conditions permitted
more complete burning of duff and woody materials
in which the hemlock were rooted. Whether the
hemlock-redwood-Douglas-fir seedling establishment
was a fortuitous accident or was due to the conditions of the burn is unknown. No estimates of
light intensity have been made on the 1974 burn,
however, the relatively high light requirement for
Douglas-fir appears to have been met. Basal
sprouting by tan oak and young redwood is typical
The 1974 fire may have been ignited in the
afternoon or evening during the first week of
October and was controlled after its discovery
the following day, burning six acres. I was able
to observe spread rates of approximately 2-3 ft.
per minute down hill and slightly faster up hill
with flame lengths of 0.5 to 2 feet. Flames
reached the canopies of two or three redwoods and
94
Table 2.--Tree survival, mortality, and establishment
following two fires in redwood forest vegetation.
Species
Prefire trees/acre
greater than 12"
d.b.h.
Trees killed
by fire/acre
Surviving trees or
seedlings estab'd
following fire/acre
Trees sprouting
per acre
1880 FIRE
Redwood
Douglas-fir
Western Hemlock
20
2
5 or more
probably none
probably none
possibly many
none
none
607
0.5
446
1
does not sprout
does not sprout
1974 FIRE
Redwood
17
Douglas-fir
Grand fir
2.6
1.6
0.3
none
Westem hemlock
Tan oak
5.16
1.6
all
none
250
present but did not
occur in sample
plots.
473
none
1.5(all free stand'g
trees under 12" d.b.h.)
(1.25 sprout groups/
acre associated with
overstory trees also
sprouted again.)
does not sprout
does not sprout
does not sprout
7 (including trees
less than 12" d.b.h.)
Fritz, Emanuel. 1929, Some popular fallacies
concerning Cal if.ornia redwood. Mad rona 1 :
221 - 224.
Roy, Douglas F. 1966. Silvical characteristics
of redwood (Sequoia sempervirens (D. Don)
Endl.) U. s. Forest Service Res. Paper
PSW-28. 20 pp.
Stone, Edward C. Rudolf F. Grah and Paul J.
Zinke, 1969. An analysis of the buffers and
the watershed management required to
preserve the redwood forest and associated
streams in Redwood National Park. Prepared
for the U. S. National Park Service. 106 pp.
Veirs, Stephen D., Jr. 1972. Ecology of the
coast redwood, a progress report. Redwood
N. P. Crescent City, Cal. 6pp.
Veirs, Stephen D., Jr. 1979. The role of fire
in northern coast redwood forests, (Second
Conference on Scientific Research in the
National Parks, Nov. 28, 1979, San Francisco,
CA) unpublished, 20 pp.
Weaver, John E. and Frederick E. Clements. 1929.
"Plant Ecology", McGraw Hill Book Company,
Inc., New York. (p 443).
for this site and may be of great importance in
maintenance of these species in sites where
regeneration from seed is strongly limited by
climate conditions.
CONCLUSIONS
It is clear that much additional information
is needed in order to clarifY the role of fire in
redwood vegetation. The infrequent establishment
of the Douglas-fir component of moist site redwood
stands is for now the most interesting aspect of
the dynamics of old growth redwood vegetation.
Additional observations of fires or experimental
burning in this vegetation type, and extensive
mapping of Douglas-fir age classes and old fire
pattems is needed to clarify the natural role of
fire in redwood vegetation. Once done, this
information can be used to develop sensitive
long-term management to ensure the perpetuation
of dynamic old growth redwood forest ecosystems,
in parks, if nowhere else.
LITERATURE CITED
Cooper, D. W. 1965. The Coast Redwood and its
ecology. Agricultural Extension Service,
University of California. 20 pp.
95