HomeMy WebLinkAboutWildfire in the Taiga of Alaka Leslie ViereckWILDFIRE. IN THE TAIGA OF ALASKA
leslie A. Viereck
Principal Plant Ecologist
Pacific Northwest Forest and Range Experiment Station
Institute of Northern Forestry
USDA Forest Service
Fairbanks, Alaska 99701
I. INTRODUCTION
The ecological effects of fire in the taiga of Alaska v1ere studied
by Harold Lutz in the early 1950's and reported in his much used and
quoted paper, 11 Ecological effects of forest fires in the interior ~f
Alaska 11 (!..utz 1956). His work has been used as a 11 bible" by resource
managers, and very little effort has been put into continuing fire effects
studies. Recently, there has been renewed interest in the effect~ of fire
in Alaska. A bibliography on fire in far northern regions was compjled
by lar~cn in 1969. In 1971, the Alask~ Forest Fire Council and the
Society of American Foresters sponsored a symposium, 11 Fire in the Northern
~nvironment 11 (Slaughter et a1. 19i1), ~hich brought together a number of
research and management personnel and summarized the current status of
research and management r2lated to fire in Alaska and parts of northern
Canada. My paper drav:s heavily on the symposium in determining the
present statu~ of knowledge o~ fire effect~ in the Alaskan taiga. I
k 1 d . . . . • ~ -• 1 t . . u so~ ac now e ge 1:tie ass1s:Z:.n~e 01 ~'::·:era! or my col eagues a. r.nr:: ,..,
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Forest Service, Institute of Northern Forestry, who prepared sections.
of this paper--specifically Dr. Charles T. Cushwa, Program Leader, the
wildlife section; Dr. John C. Zasada, Silviculturist, the autecology
section; Roy Beckwith, Principal Entomologist, the section on insects;
and Richard J. Barney, Principal Fire Control Scientist, the section on
fire history. In addition to a review of the literature, I have included
unpublished data and information gathered in several years of research
in the Alaskan taiga by the staff of the Institute of Northern Forestry.
A. Vegetation
The northern boreal forest of Alaska is primarily open, slow-
growing spruce interspersed with occasional dense, well-developed forest
stands and treeless bogs. This type of regional vegetation is referred
to by the Russian term 11 taiga 11 to differentiate it from the closed, fast-
growing forests of the more southerly region of the boreal forest zone .
. In Alask~ the taiga extends from the south slope (Fig. 1) of the Brooks
Range southward to its border with the coastal forests, eastward to the
border 'tlith Canada, and westward to a maritime tree line very closQ to
the Bering and Chukchi Seas. Within this area of 138,510~000 hect~res,
approximately 32% (43,000,000 hectares) is forested, but only about 7%
(9,000,000 hectares) is classified as commercial forest land (Hutchison
1967). The unforested land consists of extensive bogs, brush thickets,
grasslands, sedge meadows, and some alpine tundra.
On the warmest, well-drained sites, the forests consist of closed
spruce-hardwood stands; white spruce (Picea qlauca [Moench] Voss),
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paper birch (Betula papyrifera Marsh.), and aspen (Populus tremuloides
Michx.). On poorly drained sites, including those underlain by permafrost
and on n0~~h facing slopes, the dominant forest species is black spruce .
(Picea mariana [Mill.] B.S.P.). In the wettest sites associated with
black spruce is the tamarack (Larix laricina [Du Roi] K. Koch). Balsam
poplar (Pooulus balsamifera L.) and its subspecies, black cottonwood
(f.. balsamifera ssp. tri.:hocarpa [Torr. & Gray] Brayshaw), form extensive
stands o~ the floodplains of the major rivers.
On the broad expanses of the foothills and upland areas are exT.E.nsive
areas of open stands of white spruce and black spruce with willows, resin
birch (Betul_~ glandulosa) ~1ichx.), ericaceous shrubs, Cladonia lichens,
feather mosses, and sphagnum mosses. Throughout th~ taiga, the forest
stands are interspersed with bogs of many types. These bogs vary from
the rich grass and sedge types to the 0ligotrophic sphagnum bogs. Of
great extent is a tussock sedge type with sphagnum mosses, low ericaceous
shfubs (especially Ledum groenlandicu~ Oeder and Chamaedaphne calyrr•lata
[L.) Moench). The widely scattered black spruce and tamarack are
commonly referred to as "muskeg 11 (see Drury 1956 for ail extensive dis-
cussion of the bog types in interior Alaska). Also interspersed
throughout the bogs and other low lying areas are numerous small lakes
and ponds in various stages of hydrarch succession.
Shrub thickets are common, especially near altitudinal and
latitudinal limits of the trees. These are dominated by alder (Alnus
cri~ [Ait.] Pursh and~ .. tenuifolia Nutt.), Salix spp., and resin
birch. This latter species may form nearly pure stands of extensive
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areas at tree line.
Grasslands are not common; but in some areas, especially in the
foothills, Calamagrostis canadensis (Michx.) Beauv. and Festuca altaica
Trin. occur on windy sites. Areas repeatedly burned at lower elevations
also sometimes develop into meadows dominated by~-canadensis, Rosa
acicularis Lindl., several species of·carex, and many herbaceous species.
The distribution of ~:he various forest, bog, and shrub types is
closely related to altitude, slope and drainage, presence or absence of
permafrost, and to the past history of forest fires, which apparent1y
have been prevalent throughout the history of the development of the
taiga in Alaska.
The forests of interior Alaska represent a nearly natural situation.
Before 1900, there was virtually no utilization or disturbance of the
resource except by the aboriginal people. With the coming of the gold
seekers was the first use of the interior Alaska forest for saw logs and
for fuel to heat and run power plants, steamboats, and mining equipn.ent.
However, because of the very limited transportation system, this utili-.
zation was limited to areas adjacent to the major r1vers and to major
. '
centers of population and was of short duration in most areas. Since
that time, there has been no major development of a forest industry in
the taiga of Alaska, and at present, forest utilization is limited to
local sawmills that provide only a small percentage of the timber needs
of the inhabitants. If one considers fire primarily as a natural phenomenon,
then, most of the vegetation of the taiga of Alaska remains relatively
undisturbed by.man.
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B. Environmental Factors
1. Climate
Most of the taiga of Alaska lies within a zone dominated by
continental climatic influences (Watson 1959}, characterized by extremes
of temperatures and low precipitation. Large fluctuations from the mean
are common. Funsch (1964) summarized growing season precipitation and
temperature data for weather stations within the taiga. At Fort Yukon
in the center of the Yukon Basin, temperature extremes varied from -59°C
to +37°C. Within the taiga region, daylight varies from 20-24 hours in
the summer months to 0-4 hours during the winter. Mean annua 1 tempei·atures
range from -l0°C in the northern portions to +2°C in the southwestern
regions. Pr~cipitation over most of the area is light, ranging from
165 mm at Fort Yukon in the interior to 750 mm at Illiamna, in the wet
south\'lest portion. The ground is covered by snm'l from mid-October to
mid-or late May, but snO\'Ifall accumulation is relatively light, ranging
from 75 em in the Yukon Basin to as murh as 250 em in the coastal areas.
Patrie and Black (1968} summarized the climatic data for Alaska according
to Thornthwaite's (1931) evapotranspiration system and found that ~ost of
the taiga fell within zones having a potential evapotranspiration of 14-18
inches {356-457 mm), with a "typical" interior Alaska climate of 0 c•2 dc'2;
i.e., semi~arid, warm microthermal, little or no rainfall surplus, tempera-
ture efficiency normal to warm microthermal. Trigg (1971) calculated
values of precipitation effectiveness index (PEI) and temperature
effectiveness index (TEI) for the main part of Alaska and combined them
into 16 subclasses which he found to be useful for fire weather forecasting.
6
Regions ranging from hot-arid to warm-dry in his classification scheme
are areas of high fire frequency. The growing season over most of the
region is short, ranging from 90 days in the interior to 125 frost-free
days in the southern cqastal' area. However, because of the long days,
,.·
warming is rapid and growing degree days [annual sum of daily mean
temperatures above 6°C ·(43°F)] vary from 940°C (l694°F) for Fairbanks
to 620°C (lll7°F) for Illiamna at the southwest extreme of the taiga
forests (Funsch 1964). High summer temperatures with little night
cooling, long periods with little or no precipitation, and frequent
lightning storms are three factors tha: contribute to the high frequency
of forest fires.
2. Soils
The soils of the taiga of Alaska have been described in a
general way by Kellogg and Nygard (1951) and Lutz (1956). Specific ~reas
in the taiga region have been mapped and the soils described in detail
by Rieger {1963) and Rieger et al. (1963). Forest soil types of the
Tanana 3nd Yukon valleys have been cla:~ified and described by Wilde and
Krause (1960). In general, the forest soils are shallow and profi1es .
only poorly developed. Bedrock is primarily a mic~ceous schist; and
most is overlain by loess, sand, outwash, and moraine formed during the
Pleistocene, by organic deposits formed in bogs or combined with redeposited
loess, or by newly formed river alluvium. Distinct Podzols have developed
1n the wetter areas south.of the Alaska Range, and a Subarctic Brown
forest soil is predominant north of the Alaska Range to the latitudinal
tree line. Bog soils or Half Bog soils (Wilde and Krause 1960) predominate
7
on wet sites over most of the lowland, and a highmoor peat is common on
upland north-facing slopes.
Loess is widespread in a broad banG north of the Alaska Range
(Pewe' 1968) and, consequentl'y, soils are highly erodible when stripped
of protective cover. .Much of the loess has been transported to lower
elevations and mixed wi.th organic material and frozen (Pewel957).
Permafrost, or permanently frozen ground, is a unique feature of the
soils of much of the taiga of Alaska. In the southern sections of the
taiga, permafrost is sporadic, found only in the coldest sites and
usually only in bogs or on north slopes under thick organic layers.
North of the Alaska Range, permafrost is discontinuous, occurring in
most of the sites, but lacking on south-facing slopes and in freshly
deposited alluvium. In much of the frozen layer, water has been incor-
porated as wedges or lenses of pure ice. In some soils, this may amount
to as much as 50% of the substrate by volume. In other areas, usually
in the coarser soils, permafrost contains little or no ice.
In most areas of the taiga, permafrost and vegetation are in a
delicate equilibrium. The distribution of vegetation is largely related .
to the permafrost, or lack of it, and to some extent the distribution of
~ermafrost is related to the presence of vegetation. If the overlying
insulating layer of vegetation is disturbed, the permafrost may begin
to melt and the active layer (the annua1 layer of thaw) to thicken. If
there are large masses of ice within the permafrost, when these melt,
the released water may form ponds, which tend to melt the permafrost
along the edges, creating 11 tha\'l ponds,11 a coTPmon feature of lm'l lying
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wet areas in the taiga of Alaska. Another important aspect of terrain
underlain by permafrost is thermokarst. If permafrost, heavily laden
with ice, is thawed, the surface will subside in a pattern related to
the underlying ice, cr~ating a system of deep holes, polygonal trenches, ,,
'~ .
and rounded mounds, a.~.tnique landscape termed 11 thermokarst.11
An important influence of permafrost in Alaska is that of holding
ground water near the SL1rface. The permafrost forms an impervious layer,
preventing percolation through the soils of surface runoff from precipi-
tation. Thus, the presence of many bogs and extensive wet areas in a
region with low precipitation is due, 111 large part, to the underlying
permafrost. However, the statement sometimes encountered that the interior
of Alaska would be a desert if it were not for the permafrost is untrue.
The best sites for tree growth are on south-facing slopes or on coarse
river alluvium where there is no permafrost.
Aspect and slope are of special i~portance in the distribution of
vegetation and soils in interior Alaska. Krause et al. (1959) compur·ed
the vegetation and soil on two adjace~~ stands on north-and south-facing
slopes near Fairbanks. They found that with similar parent materials
loess over schist, a Subarctic Brown soil had developed on the south-
facing slope, whereas on the north-facing slope, there was a Half Bog
soil underlain by permafrost. On the south-facing slope v1as a well-
developed white spruce stand (diameters of 25-35 em) with a moss layer
of Hylocomium splendens (Hedw.) B.S.G. On the north-facing slope,
there \·las an open black spruce stand with 8-cm diameter trees and a
moss layer of predominantly Sohaqnum spp. Both stands were 115-130
years old and were probably established after the same fire. Sharp
contrasts in vegetation and soils such as this, related to topqgraphy
rather than fire history, are common in the taiga of Alaska.
C. Fire
1. History of Past Fires
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Limited evidence indicates that aboriginal man was an
important cause of wildfires in the northern regions (Lutz 1959). He
used fire in camping, hunting, signa1ing, and combating insects. With
the appea~dnce of contemporary man in the northern areas, fire activity
increased, especially during the gold rush years at the turn of the
century. Fire used for land clearing, as well as from accidental causes,
burned considerable acreages during this period.
In the 1940's, with the advent of formal fire control records, more
precise measur~s of the occurrence and magnitude of fires in the taiga
became available. Before that, report~ were of a more general nature.
From 189~ to 1937, 19 fires were reported to have burned in excess of
2,470,000 hectares (6,100,000 acres)(Lutz 1956). During the period of
1898-1940~ an estimated 405,000 hectares (l million acres) of the taiga
were burned annually (Lutz 1953). Recently, however, it has been suggested
that this early estimate was too low a~d that an average of from 0.6 to
1.0 million hectares (1.5 to 2.5 million acres) were burned each year
between 1900 and 1940 (Barney l97la).
Based on the compiled wildfire statistics for the period 1940-69,
the average annual burn is approximately 400,000 hectares (1 million acres)
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(Hardy and Franks 1963; Barney 1969, l97lb). During this 30-year period,
over 70% of the fires were man-caused; the rest were caused by lightning.
Although m~n caused the most fires, lightning was responsible for 78%
of the acreage burned. Barney (197la) summarizes the fire records for
the 1940-69 period:
During the decade of the 1940's, 1,138 fires burned 12.4 million
acres in the interior of Alaska. The decade of the 1950's saw an
increase in the nu~~er of fires to 2,583, but burned acreage was
reduced to approxim2~ely 10.7 million acres. The 10-year fire
total for the 1960's was generally similar to the preceding
decade with 2,380 fires recorded. Acreage burned during this
most recent decade, however, took a significant drop to about
6.4 million acres. This acreage-burned figure was about half
of the reported burn of the 1940's. There has also been a
decrease in the average size per fire by decade with the 1940's
recording 10,906 acres per fire; 1950's, 4,137; and the 1960's,
2,674 • , ••
2. Buildup, Weather, Frequencv
. . -I.
In general, the fire season in interior Alaska is defiiled as
April 1-September 30. This time span covers the period of occurrence of
the majority of fires. Generally the months of May, June, and July ::i·e
the most active, coinciding with the major periods of high temperatures
and low humidities and precipitation. ·Precipitation during these 3
months ranges from 1.7 to 107 mm (0.07 to 4.23 inches) at Fairbanks
(Hardy and Franks 1963). Longer daylight hours and higher winds also
contribute to the increase in fire danger conditions. Buildup indexes
generally peak the latter part of June or the first part of July (Barney
1967). The buildup index is essentially a cumulative drying factor and
might be compared to a drought index. Periods of severe burning conditions
extend for about 4-5 \'leeks. During this time, the daily fire spread
indexes also reach their maximums (Barney 1968). Fires, however, can
occur whenever fuels are not covered with snow and are exposed to
several hours of warm ~emoeratures and drying winds. Fire and fire
danger records have not been kept long enough to ascertain if any
cycle exists in fire activity and burning conditions. However, from
limited available research, one might infer that a 12-to 17-year fire
pattern exists. Certainly, drought situations correlate with general
fire activity.
3. Areas and Types Burned
For fire control purposes, the vegetative types of taiga
11
have been broken into five general categories: conifer, conifer-broadle~f,
broadleaf, tundra, and other (mostly brush). Although more detailed
classes are available, the above classification allows pooling of
several sources of data to arrive at some estimate of percentages of
cover type burned. Essentially, there are about 90 million hectare~
{221.6 million acres) classed as potentially burnable in the interior of
Alaska. ~lith the exception of a few isolated stands, the vast majority
of interior Alaska has been estimated to have been burned over in the
last 200-250 years (Barney l97la). On the basis of recent statistics
and the assumption that 25% of the burning is actually reburn and that
0.6 million hectares (1.5 million acres) has burned each year, we can
estimate that 22 million hectares (54 million acres or 1/4 the total
area), essentially virgin forest has burned since the turn of the
century. Table 1 gives an estimate of the area of vegetation types
Table 1.--Estimated areas of vegetation types burned in the taiga
of Alaska from 1900 to present (based on Barney, l97la).
Area Percent
(millions of of total
Type hectares) burn
Conifer 7.9 35.9
Conifer-broad leaf 3.3 15.0
Broad leaf 0.4 1.8
Tundra 9.4 42.7
Other types 1.0 4.6
Total 22.0 l 00.0
----·-· ----
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burned since 1900. The special significance of these figures is that,
of the total estimate of 22 million hectares burned, 47.3% are in the
two treeiess classification groups. In a review of cover types burned
in fires between 1957 and 1961 (unpubl1shed office report (1964) on .. · ..
file at Pacific Northwest Forest and Range Experiment Station, Juneau),
it was determined that of the 5.9 million acres burned, 3.1 million
were forested and 2.8 mi1lion, non-forested. In the same detailed
study of 26 areas burned within that same period, it was found that
less than 0.5% of the cover burned could be classified as "commercial"
forest i~nc capable of producing at least 1.4 cubic meters of wood per
hectare (20 cubic feet per acre) per year. In summarizing the fires
on National Forest land in Alaska for the period 1956 to 1967, Noste
(1969) found that for the Kenai District of the Chugach National
Forest, the only district within the Alaska Taiga Zone, the only large
acreage burned \'ras in the non-commercial black spruce type. One fire
in this type accounted for more than 60% of all the acreage burned in
coastal Aiaska during the 11-year period. Thus, it is obvious from
these figures that fires in Ala~ka are primarily in tundra, bog, and
non-commercial forest sites and that very little timber of commercial
value or land capable of producing commercial timber has been burned.
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·Man-caused fire activity is centered around population centers. The
lightning fires are scattered throughout the taiga. Virtually every
acre of vegetation has been touched by fire in the interior, with the
possible exception of some floodplain locations, especially islands.
The majority of man-caused fires occur in the lower elevations, but
14
more lightning fires occur at higher elevations. The southerly exposures
account for the greatest amount of fire activity.
Org~nized fire control activities began in Alaska in 1939 with the
Alaska Fite Control Service,(Robinson 1960). This initial effort was .
soon strengthened, providing additional men and equipment. In 1959,
smoke jumpers were used to combat fires in the interior. Aircraft
using retardants to 11 boml:>11 fires came into use about th'at same time.
Since the 1950's, fire central capabilities have improved. With the
advent of increased civilian helicopter use came an increased mobility for
the fire fighting organization. Better communications, improved fire
detection, fire weather forecasts, new retardants, water dropping,
and helitack crews all combine to make a stronger and more effective
fire control organization.
In recent ye~rs, then, man has made a much greater effort to
control fires and is now coming closer to excluding fire completely
from the taiga. Statistics show a downward trend in acreage burned,
but the number of reported fires increased. The latter is partly
because of improved detection; however, fire control efforts are muking
a considerable impact in reducing the ~creage burned. Initial trials
are now in progress to seed clouds for both the suppression of
lightning and the increase of precipitation in an attempt to lower the
hazard as well as extinguish some fires. Obviously, man is ever
increasing his ability to get ahead of nature in the control of
wildfire.
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II. ECOLOGICAL EFFECTS ON VEGETAI.ION
A. Successional Sequence and Relationships
The successional sequence following fire in the Alaska taiGt is
complex and related to a number of parameters, the most important of
which are slope and exposure, presence or absence of permafrost, available
seed source, severity of burn, and the autecological relationships of
species. Although there are some elements of chance in the successional
patterns after an individual forest fire, general patterns recur
throughout the Alaska Taiga Zone. The~~ patterns are similar to those
found in more temperate regions during early stages of succession; but
with later stages, the complexities of permafrost-vegetation relationships
create conditions somewhat different from those found in more southern
climates. Also, there seems to be more of a tendency for a burned
plant community to replace itself directly after fire without going
through several intermediate stages. Because of the high frequency and
extent in the past of fires, successic~al stages often burn before a
stable situation is reached. It is very d~fficult to find old,
uneven-aged forest stands that one could definitely consider to be climax.
'
There are two general types of succession that occur in the taiga
of Alaska, and each will be described in some detail. They relate in
large degree to the presence or absence of permafrost or at least to the
presence or absence of poorly drained soils.
1. Dry Sites
On dry sites such as south-facing slopes or coarse river
alluvium, the usual forest vegetation is white spruce, paper birch, aspen,
16
balsam poplar, or some combination of these species. Depending upon
the severity of the fire, the usual succession is re-invasion by light
seeded species such as Eoilobium and willow shrubs, especially Sali~~
scouleriana Barratt and~· bebbiana Sarg., and an almost immediate
replacement by tree species. Both aspen and birch will regenerate from
the original trees by sprouting or root suckers. The herbaceous or shrub
stages last only until they are overtopped by the tree species. If a
seed source is available, white spruce will also invade within a year or
two of the fire, as is evidenced by mar'J even-aged spruce stands. However,
in most extensive fires seed is not available; also, white spruce may
produce abundant seeds only once in 12 years. Aspen and birch stands
dominate most of the south-oriented uplands in the interior of Alaska.
Aspen occurs on the driest, warmest sites; these are generally south-
southwest facing slopes (Lutz and Capm·aso 1958, Gregory and Haack 1965).
Balsam poplar and black cottonwood also occur on these sites, but they are
primarily found adjacent to rivers (Hu~shison 1967, Viereck 1970). The
paper birch type occurs on cooler, moister sites than aspen. The aspects
upon which this site predominates are those from southeast to northeast
and southwest to northwest (Gregory and Haack 1965).
Eventually these stands are replaced by spruce, but the process is
usually a slow one. Spruce seed is often limited, distribution is not
great over large areas, and seedbed conditions are not optimum for white
spruce regeneration. Also, Gregory (1966) has shown that it is difficult
for seedlings to become established because of the smothering effect of
the birch litter. On the south-facing slopes, aspen is gradually replaced
by white spruce--few aspen.stands are over 100 years old and these
usually have an understory of white spruce. Paper birch is replaced by
either black spruce or white spruce. Mixed stands of birch and spruce
of up to 150 years of age are common in the uplands.
Because of the frequency of fire in the uplands, what happens to
the older spruce stands is not entirely known. Older white spruce
17
stands exist only on the islands of floodplains where they are protected
from fire by the river. Here, 350-year-old white spruce stands have been
found. i!1ese river bottom spruce stands may persist as a result of
flooding that periodically eliminates t;ie moss layer, preventing the
development of permafrost layers (Viereck 1971). Normally on the floodplain,
the successional sequence is from white spruce to black spruce and bog as
the permafrost layer develops in the spruce stands (Drury 1956, Viereck
1971). It has been suggested that, even on the upland, old white spruce
stands may be replaced by black spruce and bog. Wilde and Krause (1960)
have stated, "The poor regeneration of white spruce on these moss-covered
soils casts doubt on the climax nature of this species in the subarctic
environment. A wide opening in the canopy is likely to cause invasion .
by Sphagnum spp. and black spruce, an association which would preclude
the regeneration of white spruce." This is in contrast to more southern
areas of the boreal forest where it is considered that white spruce would
be the prevailing vegetation if it were not for repeated forest fires
(Raup and Denny 1950, Rowe 1971).
Occasionally, where black spruce stands have developed on coarse
alluvium or outwash, or on thin rocky soils, a severe fire may result
18
in the replacement of black spruce stands by aspen which are established
as seedlings or by root suckers. Often in these stands, black sprace may
reseed at the same time as the aspen; but because of the rapid growth .
of aspen and the slow growth of black spruce, these stands develop into
dense aspen stands with a low understory of black spruce. Thus, black
spruce may occur on these temporarily dry sites, but v1i th the deve 1 opment
of the black spruce and moss and an impervious frozen layer, these sites
will revert to more mesic conditions.
2. Wet Sites
The forest succession on wet sites, poorly drained sites,
and permafrost sites follows a somewhat different sequence. These sites,
occupied primarily by black spruce stands, muskegs, and bogs, are the
most widespread in interior Alaska and are the most frequently burned.
Because of the presence of a permafrost layer close to the surface of
the grouno, fire does not penetrate deeply, even though it is hot enough
to kill the trees. Recovery is ra~id in these stands and occurs
mostly fr~~ vegetative reproduction of the shrubs, sedges, and grasses
that existed in the stands before the fire. Thus, within 3 or 5 years
after the fire, the burned areas may have a nea~ly continuous cover of
Eriophorum spp. and grasses, primarily Calamagrostis and Arctagrostis.
At the same time, shoots from the roots of Salix spp., Vaccinium uliginosum
L., and L~dum spp. develop rapidly. If Betula papyrifera was growing in
the original stand, it often will develop from stump sprouts. Recovery
of mosses, especially the sphagnum mosses, is slower, and pioneer mosses
and liverworts such as Polytrichum spp., Ceratodon purpureus (Hedw.) Brid.,
19
and Marchantia polymorpha L. may dominate the moss layers for many years.
Recovery of the lichen layer, especially that of the climax species
of Cladonia, is very slow; and estimates of 50-150 years for recovery of
the full lichen mat following fire are common in the literature. llowever, ... ·; :·~
few data actually exist to document the time required for lichen recovery
after fire in Alaska. ·
Because of the sem~··serotinous cones on the black spruce, tremendous
quantities of spruce seed drop to the ground during the first and second
summer after a fire. These quickly germinate and the pattern is t~at of
rapid replacement of the black spruce type by another very dense black
spruce stand. This is the most common pattern seen in the fire succession
in the forests of Alaska. In later stages of black spruce development,
if fire is not repeated, there is often a development of a thick sphagnum
mat, paludification of the site, and eventually the development of open
black spruce/sphagnum stands or, in some cases, open bogs with scattered
black spruce, tamarack, and birch, the locally termed 11 muskeg.11
If fire is repeated on the same ~~te, a nearly permanent grassland
of Calamaqrostis canadensis and herbaceous species such as Epilcbium .
angustifolium L. and Delphinium glaucum S. Wats. may result on drier
sites. Near tree line, and in some of the wetter sites, repeated fires
may result in a shrub thicket of Alnus ~rispa, Salix spp., and Betula
glandulosa.
Figure 2, modified from Lutz (1956), indicates the successional
sequence usually followed after a fire in Alaska.
•.·
~l
;
' ..
•·-t{ ' ' ~
I>RY -WARM WET -COLD
I
21
B. Present Mosaic of Vegetation
The successional sequence described in the above section and
the relative frequency of fires in th~ last 200 years have resulted in
#
a mosaic of vegetatio~;in the interior of Alaska that is closely related.
to past fire history •. ~Old fire boundaries are apparent when scanning
the hillsides or when studying aerial photographs. Ne~rly all of the
stands are less than lSC years old, and most represent earlier stages
of fire succession. Thus, paper birch and aspen cover large areas of the
drier sit~s in the upland, whereas dense young stands of black sprue~
are commor. in poorly drained upland sites and in the lowlands. At
present, there are no accurate figures as to the relative percentage of
area covered by each of the major types within the taiga. According to
Hutchison (1967), of the 43 million hectares of forested land within the
taiga, 79% is of non-commercial forests, primarily black spruce and apen
white spruce stands near tree line. Of the area classified as commercial,
which tc~:ls 10.5 million hectares, white spruce accounts for 57%; paper
birch, 23%; aspen, 11%; and balsam poplar and cottonwood, 9%.
Although the distribution and abundance of these types are related .
in some degree to chance following fire, much is owed to the autecology
of the individual species, especially to their regenerative capabilities
and their site requirements.
C. Autecological Relationships
The revegetation of a burn in the Alaskan taiga is related to
two basic sets of variables. First, the site will set limitations on
22
the plant community and thus the potential number of species available
to colonize an area. Second, the success of the species to colonize an
area is dependent upon its reproductive characteristics.
Reproduction of tbe tree species and associated shrubs and herbs
.~
~~~
is complex owing to the many factors which control this variable, so we
will consider seed and ·vegetative reproduction separately.
1. Seed Repruduction
Obviously, seed supply is of basic importance and, where
environmental conditions do not limit germination and seedling grov!th,
it is the factor controlli~g this type of reproduction. The sourc& c1n
be either seed dispersed onto the burned seed bed or seed stored in the
seed bed which is not burned nor rendered nonviable by the temperatures
created by the fire.
In the taiga of Alaska, information exists only for seed dispersed
into the burn. Zasada (1971) summarized the information for tree species.
The most important aspects of his paper and the limited information
available on other vmody species are summarized below.
(a) M~st wildfires occur during the months of June and .
July. This is approximately at the time (mid-June) of· seed ripening and
dispersal of aspen and balsam poplar seed, but definitely before ripening
of the white spruce seed, and well before the occurrence of significant
amounts of paper birch seed. Thus, immediately after a fire, a seed
source for aspen and balsam poplar may exist on both living and dead
trees within the burn and on trees in adjacent, unburned stands. White
spruce and paper birch seed must come from living trees within the burn
or stands adjacent to the burn. It is not likely that seeds in cones
or catkins would mature after death of the parent tree by fire. Fires
also occur prior to black spruce seed maturation. However, because of
the semi-serotinous cones of black spruce, there are always some seed
available after the burn except in a few exceptional cases, where the
23
burn is hot enough to destroy the cone and its seed. In central Alaska,
in one heavily burned black spruce stand with a densicy of 909 dead trees
per hectare, based on the seed remaining in 16 trees, it was estimated
that the ~esidual seed numbered 8,200,000 per hectare. Germination
percentages of this seed for each tree ranged from 8.3 to 75.8 with an
average of 41% for 6,400 seed, which meant that there were approximately
3,400,000 viable seeds per hectare left on the trees following a heavy ourn.
(b) The periodicity and quantity of seed crops vary
significantly between hardwood and coniferous species. Birch, which
depends heavily on seed as a means of reproduction (Gregory and Haack 1965),
produces vast quantities of viable seed at least once every 4 years
(Zasada and Gregory 1972). Although no·information is available for
aspen and balsam poplar, the quantity and periodicity of seed crops .
appear similar to birch. The interval between good white spruce seed
crops appears to be 10-12 years, and the quantity of seed produced in
these good seed years is 10-20% of that produced by birch (Zasada and
Viereck 1970). Periodicity of seed crops in black spruce is less impor-
tant than in other species because some seed is always available in the
semi-serotinous cones; however, intervals between good crops are probably
roughlyJthe same as for white spruce. At present, no data exist on seed
24
production in black spruce in Alaska.
Anot~er factor to be considered in relation to fire and periodicity
of seed crop in white spruce is that of a correlation between bad fire
years and increased se~d crop the following year. Zasada and Gregory
(1969) have shown that one factor of importance in initiation of flower
buds in white spruce is a vJarm, dry period in June and the first half of
July. These same conditions also create high fire danger potential.
For the brief period of record (1957-71) of seed production, 1958 and 1970
were the best seed years, whereas 1957 and 1969 were the most destructive
fire years. A similar correlation has been noted for Pinus sylvestris L.
by Uggla (1958), v1ho stated, 11 There exists a tendency toward a coincidence
of hot summers, good seed years, and years with many forest fires." Of
course, there are many factors i nvo i ved, but the corre 1 ati on betvteen
severe fire years fo 11 ov1ed by heavy seed product ion needs to be investi-
gated in more detail.
Another aspect of seed crop periodicity which has been documented
for white spruce and may also be important for other species is the
production of good cone crops containing poor seed. Apparently the seed
fail to mature because of climatic conditions. ]n interior Alaska in
i970, stands above 370-430 meters in elevation had excellent cone crops
but very low percentages of ~iable seed (Zasada, unpublished data on
file at Institute of Northern Forestry, Fairbanks, Alaska).
(c) Tree seed dispersal in the taiga is accomplished
primarily by wind; unknm'in and perhaps significant quantities are dis-
persed over snm'l and by water, mammals, and birds. Aspen and ba 1 sam
25
poplar are dispersed the greatest distance, followed by paper birch,
white spruce, and black spruce. The relationship of the number of seeds
reaching a given location in a disturbed area and the quantity of see~
produced is importantand has been considered in detail for birch by
:~··
Bjorkbom (1971).
Thus, the size and shape of the fire may be important factors in
determining the invadins tree species. Small burned areas could be
colonized by white spruce dispersed from trees around the edge of the
fire, whereas invasion of white spruce into large burned areas is ar.
extremely slow process unless pockets of unburned white spruce remain
within the burned areas. In a study in the Caribou-Poker Creeks Research
Watershed near Fairbanks, Quirk and Sykes (1971) suggested that stringers
of mature white spruce are less susceptible to fire than the surrounding
successional stands and thus may remain as a seed source when the
surrounding stands are burned. Effective dispersal distance for white
spruce has been determined to be approximately two tree heights (45-hQ m).
Extensive fire areas are easily recolonized by black spruce from residual
seed, and by aspen, balsam poplar, and birch from long distance tran~port .
of seed and from vegetative reproduction. Although Rowe (1971) considers
white spruce in Alaska to be a fire-adapted tree, it seems to have no
reproductive behavior that is adapted to invasion of large burned areas.
The above discussion has considered only tree seed. No information
is available concerning seed production, survival, dispersal, and mobility
for shrub and herbaceous species.
Salix is one of the most important groups of shrubs to invade burned
26
areas. Some Salix species, such as Salix alaxensis (Anderss.) Cov. and
and s. scouleriana, produce ripe seed as early as the end of May, whereas
others, su;h as Salix glauca L., disperse ripe seed from late July until
the end of August. Salix seed, as with aspen and balsam poplar, are viable
only for a few weeks (USDA Forest Service 1948). Therefore, the time of
burn may be important in determining which species of willow will colonize
the burn the first year.
The second possible source of seed for regeneration following fire
is organic matter and soil; longevity of seed stored there and whether
or not it is rendered nonviable by the temperatures generated by the fire
will determine the availability of this seed. There seem to be two
general categories of seed.
Tree, tall shrub (alder, willow), and certain small shrub (e.g.,
Vaccinium spp.) seeds occupy one categcry. The longevity of these seeds
is generally short under natural conditions, lasting from a few weeks
(willow) to probably no more than several years (white spruce). In
addition, the physical characteristics of these seeds, e.g., thin, soft
seed coats and little or no endosperm,,seem to provide_ very little pro-
tection to the embryo from high temperatures.
In contrast, the second general category of seeds -has relatively
thick, hard seed coats and more endosperm surrounding the embryo than
short-liv~d seeds. The longevity of long-lived seeds is not known,
but the thick seed coat suggests an impervious nature and perhaps longer
period of viability under natural conditions. Although no data are
available for Alaska for the effect of fire on seed germination, seeds
27
from elsewhere with simila·r characteristics are knmvn to be fire
resistant; and, in some species, their germination is stimulated by
fire (Cushwa et al. 1968). Among othc~s, genera included are Viburnum,
Rosa, Cornus, Geocaulon, Corydalis, and Shepherdia. In one burn studied
in Alaska, Corydalis semoervirens (L.) Pers. seed germinated within a
few weeks after a burn, apparently from residual seed in the burned
organic layers.
The environmental factors which regulate temperature and moisture
and which affect seed germination and seedling establishment are the
next important aspect of seed reproduction. Mineral soil appears to be
the most suitable seed bed for germination of all species of Alaska taiga
trees and most of the shrubs. Organic seed beds can provide excellent
conditions if they remain wet throughout the critical period; however,
this probably rarely occurs on most burned sites:in Alaska. When seed
beds are dry, temperatures as high as 70°C have been recorded at the
surface ··f the unburned moss-organic matter on south slopes. The maximum
thickness of organic seed beds which can be tolerated is determined in
part by the ability of the radicle to penetrate to a more stable moisture
supply such as exists in the mineral soil; general observations show that
thicknesses greater than 5-8 em will prevent rapid establishment of white
spruce ~nd most likely all tree species.
Lutz (1956) observed considerable variation in seed bed conditions
in burned areas. He reported that an average of 35% of burned areas had
exposed mineral soil. However, the variation was extreme (0-100%) and
would appear to indicate that each burn must be considered as a separate
28
case. With regard to seed bed conditions, it is probably more realistic
to consider the organic matter thickness in the unburned stands. In
mature hardwood stands, organic matter thickness averages 7-10 em. In
white spruce stands, moss-organic matter is generally 20-30 em thick;
in black spruce, up to 50 em or more thick. This, in conjunction with
those factors which affect drying of these layers, helps to explain the
variation in the amount of mineral soil exposed and observed by Lutz.
They also complicate the patterns of revegetation within each burn.
2. Vegetative Reproduction
Vegetative reproduction is important for the follovting
reasons:
(a) The great variability in destruction of the organic
layers sets limitations on reproduction by seed.
(b) Reproductive material with an established root system
and available supply of stored food is immediately available and not
depend~nt on dispersal into the burned area.
(c) There is a low success ratio of sexual reproduction
by some species coupled with an ability to reproduce vegetatively. Aspen .
stands are mostly the result of vegetative reproduction (Gregory and
Haack 1965). Balsam poplar and black cotton\~ood are known to reproduce
vegetatively; however, the importance in stand formation is not known.
Birch also reproduces by stump shoots; but although stands with several
stems originating from old s~umps are not uncommon, most trees appear
to be of seed origin. Vegetative reproduction following fire is of little
importance to the spruces. Most of the shrub and herbaceous species
29
sprout or sucker vigorously following fire. On a 1971 fire at ~ickersham
Dome in interior Alaska, revegetation is being studied in detail by the
Institut~ of Northern Forestry. Populus tremuloides, Betula papyrifera,
Salix scouleriana, and Alnus crispa were observed to produce shoots up
· ... ·
to 40 em long the same' summer as the fire, and there were numerous smaller
sprouts of Ledum groenlandicum, Rosa acicularis, and Vaccinium uliginosum.
The occurrence of the propagating plant parts within the organic
-matter-soil system is im~ortant in vegetative reproduction. This, as
with organic matter, varies between sites and with species. In the
aspen stands, most of the propagating roots occur within 5-15 em of the
soil surface. In white and black spruce forests, the roots and rhizomes
of many of the shrub and herbaceous species occur within 2-5 em of the
mineral soil-organic matter interface. Thus, the intensity and depth
of burn may encourage sprouting and suckering under some conditions and
prohibit them under others.
30
III. EFFECTS ON SOIL
A. Permafrost
0ne of the most important effects of forest fires and the
resultant burning of the organic layer in the taiga of Alaska is the
increase in the depth of the annual thaw (active layer) of permafrost
soils. The thick moss layer of black and white spruce stands acts as
an efficient insulator during the summer months, limiting thaw of the
soils to depths of 1 meter or less. In a typical black spruce stand on
permafrost in interior Alaska, maximtrm tha\'1 is from 40-75 em. Bliss and
Wein (1971) report active layer thicknesses of 30-48 em for various
vegetation types, including some shrub types, on the north slope of the
Brooks Range.
Few data are available for thickness of the active layer under
natural veyetation or after burns in the forested stands in Alaska, but it
is generally known that the active layer is thicker in the successional
stages following fire than it is in unhurned black spruce forests (Lutz
1956). In the Mackenzie Delta at Inuvik, Heginbottom (1971) reported
that by the second SUmmer after a fire in the black Spruce type, t;1aW
.
was 9 em deeper in burned than in unburned stands and 35 em greater on
the firelines where the organic layer had been completely removed. For
the same fire and area, Mackay (1970) reported a 42% increase in active
layer thickness 2 years after the burn. In an extensive fire in eastern
Alaska, Lotspeich et al. {1970) found no significant difference in thaw
depth 1 year after the fire. Both burned and unburned stands had thawed
to about 70 em by the end of the first summer following the fire.
In some low alpine tuhdra of Eriophorum tussocks in the taiga of
Alaska, Wein (1971) reported a 30-50% increase in the active layer in
early summer following a fire the previous year, but only a 15-20% .
difference by the time of maximum thaw in the fall. The increased
thawing depth was most significant during the short growing season of
the Eriophorum tussocks.
31
Heilman {1966) studied soil temperatures, active layer thickness,
and nutritional status in black spruce-sphagnum stands on north-facing
slopes in interior Alaska. He found t~ot the active layer ranged fro~
18-25 em in black spruce-sphagnum stands but was greater than 40 em in
adjacent birch stands. He concluded that on these sites late stages of
forest succession after fire resulted in a change from the birch stands
to black spruce-sphagnum type and eventually a sphagnum bog with scattered
black spruce. As this succession proceeded, there was a degradation of
site, brought about primarily by the thickening of the moss mat and the
resultan: lessening of the depth of th~~.
In our study on Wickersham Dome near Fairbanks, we found no signifi-
cant difference in the depth of thaw b~tween burned and unburned sites
at the end of the same summer as a late June \·lildfire. In four burned
black spruce stands, the results of probing in each stand showed an
average ~epth of 44 em, whereas in two unburned stands, the active layer
depth was 47 em. However, refreezing of the active layer the following
winter was more rapid in the unburned stands than in the burned.
At the northern limits of the forest vegetation, fire may result
first in a slight lowering of the permafrost layer, followed in a few
32
years by a significant increase. Kryuchkov (1968) reports that fire
first caused a thawing of the active layer, with a resultant release of
moisture, creating conditions which stimulate the growth of Eriophorum
cover. As a result of the insulating effects of the thicker vegetation
mat, the active layer was only 40-45 em thick a few years after the fire
whereas before the fire, it was 50-70 em. The resultant colder and wetter
soils prevented the establishment of tree seedlings ar.d caused large areas
of what Kryuchkov termed "pyrogenic tundra." It is quite likely that the
same reaction to fire may be occurring in Alaska near the latitudi~a1 and
altitudinal tree limit. Wein (1971) studied biomass production on burns
in an Eriopho~um-heath within the taiga in Alaska. He found that the
amount of regrowth was 50% on 1-year burns, 80% on 2-year burns, and
that after 4 years, the production was 110% of the control. According
to Kryuchkov's report, this increased productivity of the vegetation mat
would eventually result in a shallower thaw than before the fire.
One other effect of the lowerin~ of the permafrost table aft~r fire
is the formation of t~ermokarst. In areas heavily underlain by ice
wedges, thawing results in ~ subsidenc~ of areas over the ice wedges,
creating a polygonal mound and ditch pattern. These ditches may be 2-3
meters deep and often remain filled with water most of the sum~er.
Active t!1ermokarst, with trees tipping into the ditches and fresh cracks
in the mounds, occurs in successional stands of birch at least 40-50 years
after the fire. Eventually, with the return of black spruce, these sites
may become stabilized, or small thaw ponds may develop and continue in
an active cycle of pond and black spruce, as has been described by
Drury (1956).
B. Soil Nutrients
Lutz (1956) has summarized the data on the effects of fire on
soil nutrients in Alaska. Although, as stated in Ahlgren and Ahlgren
(1960), there is considerable variation in the effects of fire on soil
properties as related to various aspects of the site conditions and
original soil properties, some generalities may~be~made which-seem to
33
hold true for Alaska and other northern countries. Both Lutz in Alaska
and Scatter (l97la) in northern Canada have found an increase in nitrogen,
exchangeable calcium, and to a lesser degree, potassium and phosphorus,
in the surface soil layers following fire. Coupled. with this is a decr~ase
in acidity. Lotspeich et al. (1970) found no significant trends in soil
nutrients 1 year after a fire in black spruce stands in eastern Alaska
but did note a slight decrease in total cation exchange and an increase
in potassium.
Lutz (1956) explains the increase in available nutrients as resulting
from their release from the burned pcrtions of the organic layer as well
as from increased nitrification by soil organisms and by increased abundance
of plants with nitrogen-fixin~ organisms following fire. Van Cleve (1971),
on the other hand, estimated that with a uniform burn consuming the
nitrogen in the 0-5 em layer of the forest floor, 778 kg/ha and 2,026 kg/ha
of nitrogen would be lost from a 70-and 170-year-old spruce forest,
respectively. This loss would represent a potential supply of N rather
than an actual supply of available N at the time of the fire.
34
However, Heilman (1966, 1968) showed that much of the soil nitrogen,
potassium, and calcium is tied up in lower organic layers, which in
permafrost soils remain frozen the year around, and is thus unavailable
to plants. In the five stages of succession from a birch-alder stand
to a sphagnum-black spruce stand, he found that the foliar levels of
nitrogen decreased with age of the successional stqnd and that P and K
actually reached deficiency amounts as the nutrients became unavailable
in the frozen or cold organic layers. He concluded that the removal of
low density and low-nitrogen-containing layers of moss by fire and the
deeper thawing of the underlying soil results in a concentration of
available nutrients in the warmest portion of the soil profile and helps
to explain tr.e large improvement in productivity and available nitrogen
following the burning of the sphagnum-black spruce type in Alaska.
Whatever the actual cause, there does seem to be a release of
nutrients and a fertilizing effect of fire on the organic soils in
Alaska. Lutz (1956) noted that seedlings which become established
immediately after fire may grow faster than seedlings of the same aye
in nursery beds. No data exist for the amount of time that this effect
.
persists under Alaskan conditions. However, in Sweden, Uggla (i968)
found that the growth of seedlings on an area of raw humus which had been
ourned was better than growth on an. unturned area for only the first
nine years following the fire. After 21 years, tree growth on the
unburned area was 65% greater than on the burned area. In Alaska,
Heilman (1966) has shown that in the later stages of succession of the
black spruce type, the nutrients once again become limiting to tree growth.
35
IV. EFFECTS ON HYDROLOGY AND SILTAfiON
Little inforrr1ation is available on the effects of fire on hydrologic
relations in Alaska. Lotspeich et al. (1970) studied changes in streaM .
nutrients and fauna in and adjacent to a 100,000-hectare fire in eastern
Alaska. They found an increase in the chemical oxygen demand and
potassium concentration in streams of the burned area compared with
those in the unburned area, but they found no change in the benthic
fauna of the streams that could be attributed to the effects of the
fire. Lotspeich (1972) also studied the.effects of dropping 288,000
liters of fire retardant in a small watershed to control a fire at
Wickersham Dome in 1971. He found a slight increase in total phosphate
in the stream below the fire compared with that above the fire, but
nitrogen concentrations were not affected.
Increased erosion and \·Jater runoff as a result of fire seem to be
at a minimum in northern areas in contrast to temperate regions, where
fire nearly always results in increaserl runoff and flashy stream flow
(Ahlgren and Ahlgren 1960). Both Lutz (1956) and Scatter (197la,b) point
out that the low intensity of summer ra}nfall, the long periods when the
soil is frozen, the high water-holding capacity of the organic layers,
and the rapid revegetation of the partially burned organic soils result
in very little surface erosion of the burned sites.
However, this is not true of the areas on which firelines were
{Figure 3). constructed by large tracked vehicles/ Lotspeich et al. (1970) pointed
out that the fire control methods may cause more long lasting damage to
the aquatic ecosystems than does the fire. Deleonardis (1971) confirms
36
the conclusions of Lotspeich and points out that the erosion effects
of constructed f·irel ines may far outlast any effect of the burn.
This problem of erosion of firelines i: brought about by the nature
of the underlying permafrost.. These firelines have often been con-
structed along small watercourses in the valley bottoms where the
substrate consists of organic soils underlain by permafrost with large
quantities of ice. When the vegetation and organic mat are removed, the
permafrost melts. releasing large quantities of water and beginning a
series of water-filled depressions. This problem is compounded if a
nearby stream is captured by the system so that more water is available
for melting the permafrost and for eroding the surrounding silt. The
combination of melting ice wedges and water erosion may result in erosion
d . h 5 10 d (Fiqure 4 )'1 · 1 fl · · 1tc es -meters eepJ even on re at1ve y at terra1n. Revegetat1on
of these ditches is slow because of the continuous slumping and erosion--5-10
years after a fire there can still be active erosion even though the
surrounding burned area has nearly recovered from the effects of the
burn. Considerable effort is now made in Alaska to locate firelines
away from low-lying permafrost sites, and quick rehabilitation of firelines
by constructing water bars, artificial ·fertilizing, and seeding is done
whenever possible (Bolstad 197;). Still, the siltation of streams and
erosion caused by the gullying of firelines on permafrost is one of the
most long lasting and serious consequences of forest fires in Alaska
today.
37
V. EFFECTS ON WILDLIFE
There are numerous writings on the effects of fire on the habits
of wildlife in Alaska, but most ha~e rasulted from extensive studies of
large areas with little quantitative data to support general hypotheses.
No doubt, the size of the State, the diversity of wildlife habitats,
logistic problems, and cost have all contributed to the general lack of
systematic quantification of the effect of fire on wi~dlife habitat in
Alaska.
Gradually, the focus of research is sharpening on the effects of
fire on wildlife habitat in the northern forest. Scotter•s (1963, 1964,
1967, 197la, l97lb, and 1972} works in Canada are examples of hypotheses
being tested to determine quantitatively t~e effects of fire on the
habitats of some species of wildlife.
In the writings of early naturalists and explorers in Alaska, there
are numerous observations on the occurrence of fire and its effects on
the habitats and population densities of wildlife. Lutz {1956, 1959)
provides an excellent summary of these early writings on fire occurrence
and effects on wildlife in Ala~ka. ·
A. Caribou (Rangifer)
Much has been written on the effects of fire on the habitat
of caribou in North A~erica. There is general agreement that fire
destroys the lichen-rich winter range of the caribou and that recovery
of cryptogamic flora is slow, often requiring more than 100 ·y~ars to
reach pre-burn levels of production.
Palmer (u~published data on file at Fairbanks, Alaska, 1941),
Lutz {1956), Courtright (1959), Leopold and Darling (l953a, 1953b),
Buckley\ l958a and b), Sumner (1951), Hanson et al. [Hanson, H.,
R.F. Scott, R.O. Skoog, R.A~ Rausch, and W. Mitter. 1958. Caribou
-~
management studies, analysis of Nelchina caribou range. U.S. Dept.
38
Interior, Fish and Wild1. Serv. Job Completion Reports, Project W-3-R-12,
·Alaska Work Plan B, Job. No.6, Vol. 12, No. 4. Unpublished report], and
others have written on the detrimental effects of fire on caribou habitat
in Alaska. A basic assumption underlying all these writings was that
during w1nter, caribou depend heavily on the availability of lichens as
a source of food. This assumption was influenced no doubt by research
and observations from other parts of the world, especially Canada.
Reports by Kelsall (1968), Banfield (1952), Cowan (1951), Edwards (1954),
Cody (1964), Scatter (1964, 1967, 197la, 197lb, 1972), Bergerud (1953),
and others have commented on the detrimental effects of fire on caribou
winter range by destroying lichens throughout the caribou's range in
Canada;
Skoog (1968), in ~eviewing work done in Canada, felt that the portions .
of Canada between Hudson Bay and the Mackenzie River were considerably
different from arctic Alaska, both in physiography and vegetation. He
pointed out that in Canada the tundra merges gradually with the taig~,
mountain ranges are absent, and the terrain is generally flat and rocky
with relatively few extensive sedge meadows. The most extensively burned
sections of Alaska occurred in the lowland areas, which Skoog felt were
not co~monly used by caribou. The wide interspersion of alpine areas,
rivers, lakes, and bogs in Alaska limited both the extent and effect of
fire on the main caribou ranges.
Basically, there is no disagreement that fire eliminates much cf
the lichen forage in spruce forest for considerable periods of time,
thereby reducing the potential carrying capacity of the total range.
The main point, Skoog stresses, is that, because of the variation in
physiography, vegetation, and food habits, the effect of fire on the
total caribou habitat in Alaska has not been as pronounced as it has
39
been in other parts of the world, especially Canada. He stated that in
much of Alaska, the irregular topography and the interspersion of fire
barriers have permitted many areas containing abundant winter forage to
escape destruction by fire. This situatioi·• is in contrast to northern
Canada, where fires can sweep for miles across the continuous spruce
forest. Also, Skoog showed through examination of stomach contents that
caribou in Alaska do not require lichens, nor should the relative abundance
of the~e plants be used as the indicator to establish the carrying capacity
of Alaskan ranges. Based on examination of 91 samples of caribou stomach
contents from the Nelchina rang·e, Lensink [Lensink, C.J. 1954. Food
requirements and range use, Nelchina caribou herd: Summer food habits.
U.S. Dept. Interior Fish and Wildl. Serv. Federal Aid in Wildl. Restoration
~roj. W-3R, Quarterly Prog. Rep. Vol. 9, No. 1] found that the fall diet
consisted of 31% lichens, 23% grass and sedge, 41% woody plants, primarily
willow leaves. Skoog, in examining over 500 caribou rumina from animals
killed by hunters in the same area·, concluded that during October, November,
and December sedge-grass comprised 50% of the diet and lichens, 30%.
Later during the winter, utilization of these foods was estimated to
be equal.
40
In conclusion, Skoog believed fire has destroyed rather large
expanses of potential caribou winter range in Alaska. Theoretically, the
carrying capacity of the total caribou range in Alaska has been reduced
temporarily due to this destruction of winter forage; however, the
present population densities are much lower than the mJximums dictated
by food alone and, hence, the reduction in total range due to losses in
\'linter ra:1ge by fire becomes less meaningful as a factor 1 imiting the
caribou population density in Alaska. 01 The fact that Alaska caribou
are not dependent upon lichen growth in spruce forest and can utilize
the extensive sedge forage on the tundra, alpine meadows, bogs, and
lake shores greatly mitigates the losses due to fire 11 (Skoog 1968).
Skoog•s work points out the need to avoid sweeping generalities
applied to areas with the ecological diversity of Alaska. Each of the
six cariuou ranges in Alaska has unique features--physiographic, floristic,
etc.--and fire affects the capacity of each area to support caribou in
varying degrees, depending on many environmental factors. Unfortunately, .
we have not as yet quantified the floristic response to burning in many
of these ranges in Alaska.
Hanson et al. (1958) identified and described the natural plant
communities on the Nelchina range, including observations on succession
and factors affecting succession, maintenance, and occurrence of plant
communities. This is one of the more detailed studies of the ecology of
caribou range in Alask~.
Pegau {1972) recently resurveyed many of Hanson's plots and con-
cluded that shrubs were increasing due to a general 11 drying 11 of the
range ami overuse of lichens by caribou. He felt more work was needed
to determine the ability of ·the Nelchina herd to use forage
"
other than 1 i chens du~'i.ng winter.
Courtright (1959) ·has an excellent summary of literature on the
·genus Rangifer, includir?, information from Canada, U.S.A., Scandinavia,
U.S.S.R., and other northern countries.
41
Lichen Pr>oduction.--11 The quickened rhythm of fire has in general
favored ehtension of willow-aspen-birch and concommitantly reduced the
original stands of lichens •.•• " (Leopold and Darling l953a)4 '' ••• up to
50.or even 100 years being required for them to achieve pre-burn levels
bf production" (Leopold and Darling 1953b). These statements are
repeated numerous times in the literature on fire effects on wildlife
habitat in Alaska.
Scatter (1971a), working on the winter range of barren-ground caribou
in the taiga of Canada, found that the standing crop of lichen following
burning varied from 3;4 to 812 ·kg/ha (3 to 725 pounds/acre) from the
youngest to the oldest (1-10 to 120+ years) upland forest and that when
Mature spruce-lichen forests are burned, major forage lichens usually
take 70-100 years or more to recover their pre-burn abundance.
Cody (1964) found no significant recovery of the lichen cover 9 years
after a fire in the Mackenzie Delta.
Pegau (1970a) found that, in western Alaska, lichens, disturbed by a
number of causes (but not fire) and then protected by fences from grazing
reindeer, had not fully recovered after 33 years. He (Pegau 1968)
reported annual growth rates for Cladonia alpestris L. (Rabenh.) and
~· rangif~~L~a (L.) Wigg. of 5.0-5.3 and 4.1-4.9 mm/yr, respectively,
on the Seward Peninsula, whereas Scatter reported rates of 3-5 mm/yr
for major forage lichens in Canada.
B. Noose {Alces)
Spencer and Chatelain (1953) found, through observations of
burns in south central Alaska, that sucr.ession followed a variety of
patterns resulting in creation of useful moose winter range for from
0 to 50 years. Under average conditions, stands appeared to furnish
42
good forage for 15-20 years after the fire. They felt that the 127,600-
hectare fire in 1947 on the Kenai Peninsula induced an increase in moose
population of approximately 400% between 1950 and 1953, with significant
forage produced in 3 years follmoJing this fire, 96% of \'Jhich was aspen
sucker growth.
Leopold and Darling (1953a and b), Chatelain (1951, 1952), Spencer
and Hakala (1964), and Hakala et al. {1971) have written about the effect
of fire on moose habitat in the Copper River~ Susitna, and Kenai areas
of Alaska. General observations are that fire improved the habitat
through increased productivity and availability of deciduous woody plants
(wdllow, aspen, birch, cottonwood) and that moose populations in these
areas increased in response to improved habitat conditions. Detailed
studies continue on the Kenai to evaluate the effect of the 1947 Kenai
fire and the 1969 Swanson and Russian River fires on wildlife habitat.
Hakala et al. (1971) felt that during the next 3-5 years, moose browse
would regenerate on the Swanson and Russian burns and that browse
should continue to improve during the next 20.y~ars, thereby attracti.lg
many moose hunters, as~did the 1947 Kenai burn.
43
In general, most writers agree that moose achieve highest densities
in forest areas opened by fire or other forms of timber removal, permitting
regeneration of willow, ~irch, and aspen. The moose ~s definitely an
animal that prospers in sub-climax forest conditions.
Buckley (1958a), in summarizing the net effect of fire on wildlife
in Alaska, concluded that major disturbance of the landscape (primarily
fire) during the first half of this century had created a condition
which makes it highly unlikely that there have ever before been so
many moose present in Alaska as there are today.
C. Sheep and Goats (Ovis, Oreamnos)
Leopold and Darling (1953b) concluded that sheep and goats were
primarily associated with climax vegetation of the alpine type rather
than with tundra-taiga types and that ~ire, because of its infrequent
occurrence in this type, had little influence on the habitats of sheep
or goats iri ~aska. Hjeljord's (1971) investigation of the feeding
ecology and habitat preference of the mountain goat in southeastern
Alaska and Gross' (1963) study of sheep range on Victoria Mountain and
Mount Schwatha in Alberta did not mention the influence of fire on the
habitats of these species.
On plant succession and wildlife management, Cowan (1951) commented
that some sheep ranges and populations in the Canadian Rockies were
being reduced by the advance of the forest in areas where fire control
44
was effective. Geist (1971) felt that sheep habitats were being displaced
gradually by other pla.nt communities in response to climatic changes
' .
and that the stable climax grass communities which comprise major sheep
habitats do not vanish within a few decades as do the burned habitats of
moose. He did note exce~tions where fire has resulted_ in some grasslands
occupied by sheep.
Edwards (1954) stated that in Well~ Gray Park, B.C., goats were
unaffected by fire because their range was generally above the elevation
of fire influence (above 4,000 feet).
Stelfax (1971) stated that fire improved sheep ranges by convertiny
the undesirable coniferous forest into productive grasslands on which
sheep in the Canadian Rockies depend for forage. Sheep population ir.
these areas tripled bebteen 1916 and 1936, primarily through improved
range conditions resulting from fire.
D. Sma 11 t•1amma 1 s
Haka 1 a et a 1. (1971) cited an unpub 1 i shed report by Ellison on
file at the Kenai National Maese Range of a study of small mammals on the
1969 Swanson River burn. Hakala et al. stated, "Immediately after the
fire, dead voles were found in the smoldering ashes. But a year after
the fire, numbers of voles seemed to be nearly equal inside and outside
the burn, although numbers of shrews may have been fewer in parts of the
burn. The insectivorous diet of shrews might make them more susceptible
45
to habitat disturbance by fire ... Ellison felt that location of traps
in the burn possibly influenced results; however, there were many_islands
of unburned habitat throughout the bu!~.
Guthrie (1967) su~gested that the melanism found in the arctic
\ ~.
ground squirrel was due to the darker individual being favored when
burnt-over areas \·Jere invaded. Citellus undulatus osgoodi, a large
ground squirrel inhabit~rrg the Yukon Flats basin, relies on seral plants
for food. Guthrie felt that the Yukon Flats area, with 166 mm of
annual pr~cipitation, is particularly susceptible to fire and by w.or~
than coincidence is the area of highest squirrel density. He thought
fire increased the number of plants eaten by ground squirrels, but that
non-melanistic squirrels were more susceptible to predation, thereby
favoring survival of melanistic squirrels in burned areas. He concluded
that melanism in ground squirrels of the Yukon Flats appeared to be ~
polymorphic adaptation which permitted the squirrel to take advantage
of a favn~able environmental situation. However, as the burned stanns
develop or mature following fire, non-melanistic squirrels are favored,
resulting in a special case of balanced polymorphism. Guthrie's f)aper is .
the only reference found which indicated that changes in pelage may be
nssociatcd with burned forest, and that this adaptation might be a signifi-
cant survival adaptation for a species whose food is increased by altering
succession of vegetation by burning.
E. Fur bearers
Robinson {1952) stated that wildfire destroys habitats of Alaska
fur bearers and they must move into new areas or eke out an existence
near the burn. He felt "good prime pelts are obtained from unburned,
rather than burned areas."
46
Sumner (1951) commented that fur was the third largest industry in
Alaska, but 50 years of forest fires and extensive trapping resulted in
a marked decline in this resource.
Hakala (1952), in de;cribing beaver (Castor canadensis) habitat on
the Goldstream Creek and Chatanika River, mentioned that where spruce
had been burned, poplars and birches were abundant. Murray (1961)
studying beaver ecology in the upper Tanana River, commented that when
fire makes actual contact with a beaver colony, 11 damage may be immediate
and absolute." The immediate effect of fire is destruction of their
food supply; but on a long-term basis, fire renews the aspen-cottonwood
forest. He also observed that when pure spruce stands burned, new growth
of aspen and cotton\·10od increased the abundance and availability of beaver
food.
Patrie and Webb (1953) felt that the high beaver populations of
many areas in the northern forest were~ direct result of extensive
clearcutting and widespread forest fires. They dicl, however, state that
"modern fire control and intensive forest management practices are generally
reducing the area of suitable beaver•habitat, because the beaver is
adapted to the early stages of forest succession, especially post-fire
types, \'lhich include aspen and \'Jillow.11
lensink (1953) and Lensink et al. (1955) found that Cleithrionomys
and Microtus comprised 74% and 68% of the diet of marten (Martes americana
actuosa) during summer and winter and concluded marten were found in
areas dominated by climax spruce forest. The burning of climax spruce
forest eliminated fur beare~s, such as marten.
47
Edwards (1954), working in Wells Gray Park, B.C., concluded that fire
removed marten for dec~-des and found that decline in caribou restricted
the use of forested lowlands by wolverine and grizzly bear.
During a 3-year stucy (1948-51) in Ontario, DeVos (1951) found that
fisher (Martes pennanti pennanti) and marten (Martes americana americana)
were practically absent from extensive recently logged or burned ar~cts
and that stands of birch and aspen of fire origin were poor habitats. He
stated that l~te stages of succession produced more favorable habitats for
fisher and marten.
Koontz (1968), in studying small game and fur bearers of the proposed
Rampart Dam impoundment area on the Yukon River in Alaska, concluded that
the effects of fire on wildlife populations were not clearly understood
but that many people felt uncontrolled fire and certainly repeated f~res
were not beneficial to some species of !1/ildlife. He thought that fires
repeated at "long intervals" may be beneficial to most species of wildlife
by creating edge and causing reversion of vegetation into several
successive stages.
Murray (1961) stated that in the past, fires were set by Indians in
interior Alaska to drive muskrats from their dens, but that this practice
had been successfully discouraged.
F. Black Bear (Ursus americanus)
Hatler (1972), in his study of food habits of black bear in
Alaska, stated that many older burns pr·oduced excellent crops of blue-
berries, which comprised 49% of the fa11 diet of black bear in his
study.
G. Snowshoe Hares (Lepus americanus)
Grange (1965) felt that the chance for great abundance of
48
hares in northern coniferous forest was limited to very early successional
forest st3ges not long after the occurrence of fire. He stated that, in
Alaska, 9% of the total forested area burned during an 11-year period
(1940-50) and that, because of slov1er succession, fire effects may per-
sist for decades. Generally, Grange felt that fire-habitat-succession
relationship to snowshow hare population fluctuations should be studied
more thoroughly before dismissing its influence by fire.
During a peak of the hare population (estimate of 150 hares/square
km) near ;airbanks, Alaska, in the fall-winter of 1971-72, hares consumed
willow sprouts that resulted from a fire during late June of 1971.
They also consumed charred black spruce and aspen bark.
H. ~laterfov1l
Komarek's (1971) comments in a recent symposium on fire in the
northern environment adequately describe the situation: 11 No investigations
of any serious nature have been made on the effects of fires upon habitats
of the waterfowl that frequent interior Alaska."
49
Two master of science theses on waterfowl in the Minto Flats area
make no m~ntion of the effects of fire on waterfowl populations or habitats
(Rowinski 1958, Hooper 1952~. Their wcrk was on succession following
.,..
flooding. · .. y~~
'· '
Buckley (1958b) cq.mmented that fire removed insulation, lowering
permafrost depths and consequently modifying the surface, subsurface
drainage, and water-holding capacity of the soils. The lowering of the
water table, he postulated, would reduce the amount of waterfowl habitat
and thus 1educe the total population.
On the other hand, Buckley (1958b} felt that removal of woody
vegetation by fire increased the attractiveness of the area to most waterfov1l
species. He attributed a population increase in the 77,600-hectare
(192,000-acre) Selawick burn from 8.1 to 12.8 ducks/square km to the fact
that new plant growth started at least 2 weeks earlier in the burn than in
nearby unburned portions. In this prime tundra breeding area in north-
western .~.~aska, early nesting commonly results in higher productirn than
later nesting. This 2-week increase was significant in areas like Selawick,
where growing seasons were short.
I. Grouse (Canachites canadensis)
Hakala et al. (1971) cited an unpublished report by Ellison
concerning the effect of the 1969 Swanson River fire on spruce grouse.
Ellison found only 18 broods on one 10.4 square kilometer (4-square-mile)
plot in the burned:fraction (1 year after the fire), compared with 41 on
the same area in 1969 before the fire. They concluded that the fire
OS
51
VI. EFFECTS ON INSECTS
A number of insect species have been observed to be prevalent in
fire-damaged trees, especially spruce. Buprestids and cerambycids are
corrmonly seen in larg~~numbers within a fire area, possibly attracted to
the smoke and heat (Evans 1971) or by some olfactory response to volatile
materjaJs. Scolytids attack the damaged trees and the fallen logs that
have adequate phloem fo; brood production.
The wood borers rapidly degrade the logs, making salvage for lumber
impractical. They play a major role in.breaking down damaged material.
Bark beetles are of more importance on the fringe of the fire, in "islands"
of slightly scorched trees within the fire perimeter, or in the residual
stand. Dendroctonus sp., ~ spp., and Trypodendron spp. have all bP.en
found in damaged trees adjacent to burns. The first t~to genera have
the potential to increase their population in the burned material and
spread to the live trees outside the burn. Trypodendron bores directly
into the \'IOOd, causing a 11 Shot hole 11 appearance. The holes and staining
that follow degrade the wood. If the climatic conditions are favorable,
the populations of Trypodendron in adj:cent unburned stands may cdusc as
much or more damage than the original fire.
Another aspect of fire-insect relationship is that the changes in
the composition or age of the forest stands after fire are accompanied
by changes in the insect fauna. Where spruce may not have presented an
entomological problem, destructive defoliators, such as the large aspen
tortrix (Choristoneura conflictana [Wlkr.]), may become widespread in
the hardwoods (Beckwith 1968). Often the conversion of a large area to
seedlings produces a potential insect problem that does not exist prior
to the fire.
52
Insects can also add to the fire potential in an area. Large areas
of trees killed by bark beetles add to the dry fuel supply until the wood
breaks do~;m. These trees, when fallen, add to the difficulty in moving
men and equipment in fire suppression activities. Bark-beetle-killed
timber is present in large quantities in many areas of Alaska.
VII. EFFECTS ON RECREATION AND ESTHETIC VALUES
The prime value of Alaska•s taiga lies not in development of
commercial forestry, but rather in its use for all types of recreation,
such as ~unting, fishi~g, photography, hiking, and scenic viewing from .....
';:·::.
the high\'tays, trails, and \·taterways. It is essential, then, that some
53
consideration be given ·to both the positive and negative effects of fire
on recreation and esthetics in Alaska.
From the scenic lan~scape aspect, a recently burned and blackened
area is ugly to many viewers. Any form of hiking or other recreation
within the burned area is nearly impossible because of the unpleasa~tness
of the ash and charcoa1. Burned spikes of trees, brown needles, and a
blackened forest floor are the conspicuous elements of the new burn.
However, in Alaska, the area is snow-covered for 7 months of the year;
at that time and with low sun angles, it is almost impossible to
·separate burned from unburned areas. Also, within 2 or 3 years, revegetation
of the forest floor is nearly continuous, so there is an almost par~1ike
appearance to the burn, except f9r the dead spires of the trees. I~ some
areas of Alaska, tree ~rushers are now being used to rehabilitate burns;
and it has been found that with the standing spikes knocked dov1n, the
appearance of the old burns is improved (Hakala et al. 1971). Within a
few years, the burns are revegetated with shrubs and young trees.
In the Alaskan landscap~, the successional vegetation stands out in
contrast to the unburned spruce stands. The taiga would be a rather
monotonous landscape if it were not for the many vegetational patterns of
hardwood and conifer stands that have resulted from past fires.
54
The negative effects of fire on recreation also may be of rather
. .
short duration. Although the burn itself may be an unpleasant place for
hiking and hunting for a number of years because of the dead and fallen
trees, the firelines provide open avenu~::s for other types of recreation.
At the site of the 1971 Wickersham fire, the Bureau of Land Management
set up a snow machine recreational area and published maps of the firelines
for access. Reaction among snow-mobilers was positiv2, and the area
received some recreational use. As pointed out by Hakala et al. (1971},
the recreational use of a burned area for hunting will be greater 20
years aiL£r a fire than before because of the increased moose and snowshoe
hare populations. They also pointed out that a year after a fire on the
Kenai Peninsula, large numbers of people visited the burn in order to
harvest a large crop of morel mushrooms.
One aspect of fire that affects tourist and resident alike during
bad fire years is that of smoke in the atmosphere. As pointed out by
Miller (1971), the scenic attractions of Mount McKinley National Park
can be oo~cured for several wee~s at a time, thus preventing the tourist
from experiencing a high quality visit to the Park. Ho\'tever, he reported
no signif~cant decrease in visitation ~r tourist activity in 1969, even
though the mountains were obscured by smoke for several weeks. One other
effect of smoke is to close down airports. When this happens to an airport
of a major city, as it has to Fairbanks, it may result in considerable
inconvenience to tourist and resident alike.
55
VIII. DISCUSSION
Land planning in Alaska is presently in a stage of rapid transition,
due primarily to pending large shifts ~n land ownership brought about by
the Alaska Native Land:Claims Settlement Act of 1971. Consequently, we
do not know what the management plan for most areas in Alaska will be.
However, we do know that much of Alaska's taiga will be managed as State
and National Forests, Wl1derness Areas, National Parks~ Research Natural
Areas, and Wildlife Refuges. In some of these areas the management policy
will und0~btedly be to preserve the nat~ral vegetation, with the inevitable
question of how to handle the role of fire in the natural system. This
question is already being asked by those involved in our National and
State Parks (Hoffman 1971; Prasil 1971).
We do not have complete basic quantitative information regarding the
ecological effects of fire on vegetation, environment, and wildlife in
the taiga, but we can make some recommendations regarding wildfire
managemer.: based on the available information from Alaska and other
northern areas.
-Everyone working in resource management in Alaska must realize that
fire has always been a part of the taiga environment and that to exclude
fire completely will lead to the creation of unnatural conditions. It is
also necessary to orient ourselves away from the concept that the prime
utilization of the taiga will be for commercial timber production. The
main value of the interior Alaska forests may well be its wildlife and
recreational values and the best goal for land management that of keeping
large areas in successional plant com~unities. Many millions of dollars
56
are spent controlling fires in Alaska that may do more good than harm if
allowed to burn themselves out. But at present it is impossible to
recommend letting such uncontrolled fi~-es burn, for they may develop
into a fi~e of a million hectares in extent that destroys houses, threatens
villages, and burns valuable commercial timber. On the other hand. if all
fires are controlled, it can be predicted that the landscape will become
dominated by spruce and bog and the successional species of fauna will be
" reduced. Fast-growing a~pen, birch, and white spruce will be replaced by
black spruce and bog in all but the warmest and best drained sites where
white spruce will remain. Hardwoods, primarily balsam poplar, will ~~
found only on the floodplains adjacent to the rivers. Moose will not be
nearly as abundant as they are now, and there is no guarantee that caribou
will be more plentiful.
Heinselman (1971) has suggested six alternative fire policies for
the management of Wilderness Areas and parks which might also pertai11 to
the remote areas of Alaska. These are as follows:
· "1. Attempt fire exclusion and accept the slow but pervasive
changes in plant and animal communities that inevitably follow.
2. Allow "safe'' lightning-caused lires to burn; allow also for
some other wildfires that cannot be controlled, but extinguish the rest.
If this option results in less than the natural fire frequency and burned
area, so be it.
3. Allow ''safe" lightning fires to burn, allow for some other wildfires
that cannot be controlled, but prescribe enough additional controlled fires
to assure the natural fire regime.
57
4. Suppress all wildfires to the extent feasible, and duplicate the
natural fire regime with prescribed-controlled fires.
5. Allo\"1 all wildfires to burn unchecked unless life or property .
are directly threatened, and hope that a natural fire regime will result.
6. Abandon the ideal of natural ecosystems and turn to full-scale
vegetation and environmental manipulation by mechanical and chemical
means, seedling, planting, and so on. Attempt to produce desired
vegetation with the tools of applied forestry ...
Heinselman recommends either option 3 or 4 for areas where the
natural vegetation is to be preserved.
In planning for the management of the wide variety of Alaska's
resources, all of the above listed options plus others may eventually be
used. Thus, for areas managed primarily for caribou or reindeer winter
range, complete fire suppression may be the best policy whereas within
areas established primarily for moose management, it may be possible to
allow a11 wildfires to burn unless they 2ndanger life or property or
threaten to expand into areas with higher priority for fire suppression.
This latter method has worked well in the management of fire-dominated
vegetation in some high elevation forests in California (Kilgore and
Briggs 1972). In regions surrounding human developments and in those
managed for timber production, all wildfires will need to be suppressed and
prescribed-controlled fires utilized for vegetative manipulation. In the
large remote areas of Alaska, it may be possible to preserve the natural
vegetation by allowing most lightning-caused fires to burn.
The Bureau of Land Management, the fire control agency in most of
58
the Alaskan taiga, already has the beginning of such a priority system in
effect (Richardson 1971). However, the~ do not feel that it is yet
possible to allow uncontrolled fires 1~ the Alaskan taiga. They have .
found that all large uncontrolled wildfires eventually become a threat
to life, property, or military installation. Regardless of what is
burning, the smoke that drifts from them covers high-value areas and
stops aerial detection and air attacks on new fires. "We have not been
able to identify any area where fires can safely be left to burn without
serious c0nsequences and high costs" (Richardson 1971).
However, because of their priority system, in extreme fire years,
when BLr1•s resources cannot possibly cope with all fires, many fires are
left to burn uncontrolled, thus allowing for the re-establishment of
successional stands over large areas.
In high priority fire suppression areas, Richardson (1971) suggests
that prescribed fire will be the management tool needed to replace the
natural pffects of wildfire.
59
IX. RECOt-1~·1ENOATIONS FOR THE FUTURE
To provide better background information for selection of fire
suppression options, there is a need to increase the intensity of research
on all aspects of fire effects and on techniques of controlled burning. We
must build on the work of Lutz and other researchers to gather more
detailed quantitative data from the many diverse areas in the Alaskan
taiga. Specifically, we need to know:
1. The quantitative changes taking place, with time, in all aspects
of the pla~t community, including biomass and nutrient status. This can
be accomplished partially by obtaining information from a number of aged
burns, but it will also be necessary to establish permanent plots and
continue intensive observations over a period of years.
2. The autecology of the important taiga species, especially those
important to vdldlife, and how they relate to fire. ~Je have to knm'l the
regenerative capabilities and requirements of the tree, shrub, and herb
species, :he duration of seed viability, and its ability to survive the
heat of burning.
3. More detailed.information on the effects of fire on the animal
' inhabitants, not only big game species, but birds, small mammals, insects,
and aquatic life. Once the detailed plant succession sequence is deter-
mined, it will be easier to conduct specific studies relating to wildlife
habitat and fire. Of special importance in Alaska are the problems
relating to the effects of fire on caribou and moose populations and on
· waterfmvl. Alaska is one of the main nesting areas of ~tJaterfm'll in North
America, and much of these breeding grounds are within the taiga.
4. The effects of fire on stream hydrology, erosion, landslides,
and the siltation and temperature changes in streams as well as on the
aquatic populations. The wat~r and fish of Alaska are two of its most
important resources, but little is presently known of the effects of
large wildfires on stream flow or fish populations.
5. The effects of fire on soil nutrients, soil temperatures, and
permafrost, especially thE long and short term effects of fire on the
60
depth of annually thawed ground (the active layer) in the various permafrost
zones within the taiga. How does fire affect the complete nutrient cv:le
within the ecosystem?
6. The effects of fire on recreation, both of the tourist and
resident population. This will be a difficult problem in that it must
involve the esthetic values of the people and the quality of the
visitation, intangibles upon which it is impossible to put a dollar value.
The increased resident population of the state related to the oil industry
must also be considered.
7. The methods and effects of controlled burning in the taiga. If
wildfire suppression becomes completely-successful, then a means of
creating the natural ecosystems must be developed if any of the landscape
is to be kept in its natural state.
8. The role of fire in the taiga before the arrival of outsiders.
This should be studied nm·J before this history is destroyed by the
present encroachment of man into the natural ecosystems.
9. In addition to the specific research needs on the effects of
fire on the various aspects of the environment, there is an even greater
61
need to use a systems approach in determining the effects of fire on all
of the res0urce values of an area. This will enable resource managers
to not only plan a fire suppr~ssion policy, but also to use fire to their
advantage in carrying edt management plans.
X. ACTION FOR THE PRESENT
At the USDA Forest Service Institute of Northern Forestry, a new
multifunctional research work unit is ;·,ow operating \'lith the objective
of answering some, if not a11, of these questions. Coincident with the
establishment of this project was a wildfire in late June of 1971,
62
which burned 6,300 hectares conveniently located within 50 km of the
Institute. Intensive studies into many aspects of pl~nt succession,
micro-environmental changes, mammal and insect populations, nutrient
cycling, biomass, and productivity were initiated within the first year
after the fire. In addition, a vegetation soil survey is being carried
out in a number of areas burned during the past 100 years. It is hoped
and planned that a number of additional studies on the effects of wildfire
in the taiga will be initiated in the next few years. This project will
quantify proposed hypotheses, point out similarities and differences between
fire effects in the taiga and those of more southern latitudes, and
eventually lead to the basic knowledge needed to understand the role of
fire in the natural ecosystems of the Alaskan taiga.
XI. LITERATURE CITED
Ahlgren, I. F., and C. E. Ahlgren. 1960. Ecological effects of forest
fire:. Bot. Rev. 26(4): 483-533.
Banfield, A. W. F. 19~2. The Canadian barren-ground caribou
~~
investigation, p.:~T33. Proc. Third Alaskan Sci. Conf.
Barney, R. J. 1967. Buildup indexes for interior Alaska, 1956-1965.
63
USDA Forest Serv. f'ac. Northv1est Forest and Range Exp. Sta., 49 p.
1968. National fire danger rating system spread index
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-. ~·
65
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----------
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,__ . .
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; ) . 1: :. ;-.
F·J:--~ ". ~· i , .. ~ ;~'. l:
'-,.,
. ' ;
Figure 1
Figure 3
Fi !!J~·re 4
WILDFIRE IN THE TAIGA OF ALASKA
Leslie A. Viereck
Boundaries of the Taiga Zone in Alaska (based on
Viereck and Little 1972).
Patterns of forest succession following fire in Alaska
(modified from Lutz 1956)
Erosion and fl0\'1 of soil •Jnderlain by permafrost on a
fireline one month following a fire.
Gulley formed by erosion and melting of permafrost
on a fire1ine two years following a fir,e.