Index of Species Information
SPECIES: Thuja plicata
Introductory
SPECIES: Thuja plicata
AUTHORSHIP AND CITATION :
Tesky, Julie L. 1992. Thuja plicata. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station,
Fire Sciences Laboratory (Producer). Available:
https://www.fs.usda.gov/database/feis/plants/tree/thupli/all.html [].
ABBREVIATION :
THUPLI
SYNONYMS :
NO-ENTRY
SCS PLANT CODE :
THPL
COMMON NAMES :
western redcedar
western red-cedar
Pacific redcedar
giant redcedar
arborvitae
canoe-cedar
shinglewood
giant arborvitae
TAXONOMY :
The currently accepted scientific name for western redcedar is Thuja
plicata Donn ex D. Don [8,50,51,57]. It is a member of the Cypress
family (Cupressaceae). Western redcedar hybridizes with Thuja
standishii. Hybrids are resistant to the leaf blight caused by
Didymascella thujina [50]. There are no recognized subspecies,
varieties, or forms.
LIFE FORM :
Tree
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
NO-ENTRY
DISTRIBUTION AND OCCURRENCE
SPECIES: Thuja plicata
GENERAL DISTRIBUTION :
Western redcedar occurs along the Pacific Coast from the southern part
of the Alaska Panhandle through British Columbia, western Washington,
and western Oregon, reaching into the coastal redwood forest of northern
California [8,50,54,57]. Inland from the coast it occupies a contiguous
band east of the Cascade Range from central Oregon to southern British
Columbia [54]. Much farther inland a disjunct population occurs along
the west slopes of the Rocky Mountains from Prince George, British
Columbia, to northeastern Washington, northern Idaho, and western
Montana [50,54,57].
ECOSYSTEMS :
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES23 Fir - spruce
FRES24 Hemlock - Sitka spruce
FRES25 Larch
FRES26 Lodgepole pine
FRES27 Redwood
FRES28 Western hardwoods
STATES :
AK CA HI ID MT OR WA AB BC
BLM PHYSIOGRAPHIC REGIONS :
1 Northern Pacific Border
2 Cascade Mountains
5 Columbia Plateau
8 Northern Rocky Mountains
KUCHLER PLANT ASSOCIATIONS :
K001 Spruce - cedar - hemlock forest
K002 Cedar - hemlock - Douglas-fir forest
K003 Silver fir - Douglas-fir forest
K004 Fir - hemlock forest
K005 Mixed conifer forest
K006 Redwood forest
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K014 Grand fir - Douglas-fir forest
K015 Western spruce - fir forest
SAF COVER TYPES :
210 Interior Douglas-fir
212 Western larch
213 Grand fir
215 Western white pine
218 Lodgepole pine
221 Red alder
222 Black cottonwood - willow
223 Sitka spruce
224 Western hemlock
225 Western hemlock - Sitka spruce
226 Coastal true fir - hemlock
227 Western redcedar - western hemlock
228 Western redcedar
229 Pacific Douglas-fir
230 Douglas-fir - western hemlock
231 Port-Orford-cedar
232 Redwood
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
HABITAT TYPES AND PLANT COMMUNITIES :
Western redcedar commonly occurs as a dominant or codominant on
low-elevation moist sites. In Montana, the western redcedar habitat
type series described by Pfister and others [60] occurs most extensively
in the Swan Valley and Mission Range, extends eastward locally to
Missoula, and forms small riparian stringers along major streams in the
Bitterroot Range west of Hamilton. Western redcedar occurs as a
riparian dominance type on toe-slope seepages, moist benches, and wet
bottoms adjacent to streams [35]. Daubenmire and Daubenmire [16]
recognized three western redcedar communities in northern Idaho.
Western redcedar/pachistima (Pachistima myrsinites) is an upland
community, while western redcedar/Devil's club (Oplopanax horridus) and
western redcedar/ladyfern (Athyrium filix-femina) occur on bottomlands.
Western redcedar is sometimes found as a codominant with western hemlock
(Tsuga heterophylla) [16,35,60]. Published classifications identifying
western redcedar as a dominant or codominant are as follows:
Old-growth forests of the Canadian Rocky Mountains National Parks [3].
Preliminary plant associations of the southern Oregon Cascade Mountain
Province [11].
Classification and management of riparian and wetland sites in
northwestern Montana [13].
Forest habitat types of northern Idaho: a second approximation [15].
Forest Vegetation of eastern Washington and northern Idaho [16].
Fire ecology of Lolo National Forest habitat types [17].
Preliminary forest plant association management guide. Ketchikan area,
Tongass National Forest [18].
Fire ecology of western Montana forest habitat types [21].
A guide to the interior cedar-hemlock zone, northwestern transitional
subzone (ICHg), in the Prince Rupert Forest Region, British Columbia
[33].
Riparian dominance types of Montana [35].
Classification and management of riparian sites in southwest Montana
[36].
Soil classification as an aid to identifying forest habitat types in
northern Idaho [54].
Forest habitat types of Montana [60].
Reference material Daubenmire habitat types [77].
Preliminary forest plant associations of the Stikine area, Tongass
National Forest [78].
A study of the Vegetation of southeastern Washington and adjacent Idaho
[81].
MANAGEMENT CONSIDERATIONS
SPECIES: Thuja plicata
WOOD PRODUCTS VALUE :
Western redcedar is an important commercial species throughout much of
its natural range [80]. In the Rocky Mountains, western redcedar
occupies some of the most productive sites, often producing stands with
high volume [26]. The wood is low in strength and soft but is very
resistant to decay, making it best suited for use as exposed building
material such as shingles, shakes, and exterior siding [57,69].
Hand-split western redcedar shakes sell for several times the price of
asphalt shingles but will last 100 years on a roof [8]. The wood is
fine and straight grained, which makes it suitable for interior
finishing [57]. Western redcedar wood is also used for utility poles,
fence posts, light construction pulp, clothes closets and chests, boats,
canoes, fish trap floats, caskets, crates, and boxes [50,80].
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Black-tailed deer browse western redcedar seedlings and saplings all
year long in British Columbia, and Roosevelt elk feed on them during the
fall, winter, and spring. Western redcedar constitutes one of the most
important conifer foods of black-tailed deer in the Coastal forest
region of southern Vancouver Island [51]. Western redcedar was more
severely browsed than Douglas-fir (Pseudotsuga menziesii), western
hemlock, or Pacific silver fir (Abies amabilis) on the Olympic
Peninsula. Western redcedar is a major winter food for big game in the
northern Rocky Mountains [51]. An analysis of 69 stomach samples
collected from elk harvested along the Lochsa and lower Selway rivers
between January 1 and April 1 from 1960 through 1970 showed that western
redcedar leaves made up 5 percent of the total winter diet by weight
[72]. In western Washington, black bears remove western redcedar bark
and feed on the exposed sapwood [50].
Cattle browse western redcedar in preference to Douglas-fir in
northwestern Oregon, and sheep damaged western redcedar reproduction
more than that of other trees in northern Idaho [51]. Seeds of this
conifer were only occasionally taken by field mice in caged tests [52].
Old-growth stands of western redcedar provide hiding and thermal cover
for several wildlife species. Bears, raccoons, skunks, and other
animals use cavities in western redcedar for dens [8]. In the southern
Selkirk Mountains of northern Idaho, northeastern Washington, and
adjacent British Columbia, grizzly bears have been known to use heavily
timbered western redcedar and western hemlock forests [44]. Western
redcedar is used as nest trees by cavity nesting bird species such as
yellow-bellied sapsuckers, hairy woodpeckers, tree swallows, chestnut
backed chickadees, and Vaux's swifts [45,49].
PALATABILITY :
NO-ENTRY
NUTRITIONAL VALUE :
Relatively high concentrations of calcium and low concentrations of
nitrogen are nearly always present in western redcedar foliage.
Phosphorous concentrations are usually low [51].
COVER VALUE :
NO-ENTRY
VALUE FOR REHABILITATION OF DISTURBED SITES :
Western redcedar can be planted on disturbed sites within its natural
range. The erosion-control potential and long-term revegetation
potential of western redcedar have been rated as medium [13]. Western
redcedar may be the species of choice for reforesting high, brush-risk
areas near the coast [50]. It is suitable for planting on slightly dry
to wet nutrient-poor to nutrient-rich sites [commonly with Douglas-fir,
Sitka spruce (Picea sitchensis), Alaska-cedar (Chamaecyparis
nootkatensis), or western hemlock]. Western redcedar does best when
planted in mineral soils on upland sites and in well-decomposed organic
material on lowland sites [38]. Containerized western redcedar appears
to perform somewhat better than bareroot stock [26]. Direct seeding is
practical and effective where a mineral soil seedbed is available.
Methods for collecting, storing, and planting western redcedar seeds and
seedlings have been detailed [50,51,69].
OTHER USES AND VALUES :
Perfumes, insecticides, medicinal preparations, veterinary soaps, shoe
polishes, and deodorants are made from western redcedar leaf oil.
Western redcedar extractives and residues are used in lead refining,
boiler-water additives, and glue extenders [50]. Western redcedar was
an extremely valuable tree to the Indians of the Northwest Coast,
providing materials for their shelters, clothing, dugout canoes, and
fishing nets [8,76]. Northwest Coast Indians shredded the inner layer
of bark so finely that it could be used for diapers and cradle padding
[8].
Western redcedar's drooping branches, thin fibrous bark, and flat sprays
of scalelike leaves make it an attractive ornamental. When properly
trimmed western redcedar is an excellent hedge [8,41].
OTHER MANAGEMENT CONSIDERATIONS :
Insects and disease: Western redcedar is a host for several
economically important insect species. One of the most important is the
gall midge (Mayetiola thujae), which sometimes seriously damages western
redcedar seeds in Oregon, Washington, and British Columbia [50].
Seedlings are occasionally damaged by weevils (Steremnius carenatus) in
British Columbia, and large trees are killed by bark beetles
(Phloeosinus sequoiae) on poor sites in southeastern Alaska. The
western redcedar borer (Trachykele blondeli) causes degradation
resulting in cull of sawtimber [50].
More than 200 fungi are found on western redcedar. A leaf blight
(Didymascella thujina) infects second- and third-year nursery seedlings.
As much as 97 percent of the natural western redcedar regeneration may
be killed when this blight reaches epidemic proportions. The most
important fungi attacking western redcedar are root butt and trunk rots.
Poria asiatiaa and P. albipellucida are the most important trunk rots
near the coast; P. asiatioa and Phellinus weiri are the most important
in the interior range. Rots are most evident in old stands [50].
Animal damage: Seedlings and saplings are often severely browsed by
deer, elk, and rodents. Browse damage may be one of the most important
stand establishment problems [50]. Grazing by cattle in burned stands
in the western redcedar/queencup beadlily (Clintonia uniflora) habitat
type in southwestern Montana retards establishment of western redcedar
[36].
Other damaging agents: Western redcedar is often windthrown in wet
environments, but it is windfirm on dry sites [50,51]. Western redcedar
is damaged by salt spray [50]. It is also sensitive to atmospheric
pollution. Clay dust from a brick works in British Columbia produced a
columnar form in nearby western redcedars [51].
Silvicultural considerations: Care must be exercised when logging sites
dominated by western redcedar due to the high water table. Bottomland
sites should not be disturbed other than to salvage high-value trees or
to remove high-risk trees. If harvested some dead and down logs should
be left to serve as a seedbed for western redcedar and western hemlock
regeneration. Extensive disturbance of these sites could cause
irreparable damage [13].
Western redcedar should be grown in pure stands when saw-timber,
shingles, or shakes are the desired products. Even-aged mixtures of
western redcedar and other conifers will be harvested either too early
for the western redcedar sawtimber or too late for the other conifers
when mixed-species, even-aged stands are clearcut. Western redcedar can
be grown in mixed stands when poles are to be produced under even-aged
management regimes. A nearly closed canopy should be maintained at all
times. Open-grown western redcedar tend to develop poor form, excessive
limbs, and multiple tops [51]. Western redcedar is perhaps the most
valuable species for which uneven-aged systems are applicable in the
highly productive western redcedar and western hemlock habitat types of
the Inland West [26].
Response to release: Because western redcedar is shade tolerant, it
should be treated to minimize shock from release through slow or timely
thinning treatments. Western redcedar's ability to respond to release
varies with tree, stand, and site conditions. An 80-year-old western
redcedar stand, with the overstory removed and thinned, responded with
increased growth rates up to 5 years after treatment. However, 5 to 10
years after release, growth rates slowed, and root diseases became
apparent [26]. Releasing western redcedar saplings slowly over a 17
year period had good results. The saplings responded favorably to
release with increased growth rates and a gradual increase in vigor.
Thinning western redcedar stands should occur prior to age 30. Spacing
of 1 foot by 1 foot (0.3 by 0.3 m) is appropriate for most young stands.
This density provides good tree and stand development and retains the
options for future intermediate treatments [25,26].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Thuja plicata
GENERAL BOTANICAL CHARACTERISTICS :
Western redcedar is a large, native, long-lived, evergreen tree
[8,50,57,80]. At maturity it is generally 70 to 100 feet (21-30 m)
tall, sometimes 130 feet (40 m), with a tapering trunk 2 to 4 feet
(0.6-1.2 m) in diameter, sometimes 6 feet (1.8 m) or more. On some
sites west of the Cascades, old-growth western redcedar often attains
basal diameters of 8 to 10 feet (2.4-3 m) and heights of 200 feet (61
m). The largest known western redcedars are believed to be 1,000 years
old or more [8].
Western redcedar has a swollen or buttressed base, pointed conical
crown, and horizontal branches curving upward at the tips [80]. The
leaves are scalelike, flattened and 0.05 to 0.1 inches (1.5-3 mm) long.
The twigs are flattened, in fanlike sprays and slightly drooping. The
bark is thin, fibrous and stringy or shreddy. Thickness varies from 0.5
to 1 inch (1.3-2.5 cm) [51]. The cones are
clustered near the ends of
twigs and become turned up on short stalks [80]. Western redcedar
retains its lower limbs except when in densely crowded stands [8].
Western redcedar roots are extensive. Tap roots are poorly defined or
nonexistent, but fine roots develop a profuse, dense network. Root
systems tend to be shallower and less extensive on wet soils than on
deep, moderately dry soils. When a thick duff layer is present, many
western redcedar roots lie in the duff rather than in the underlying
soil [50,51].
RAUNKIAER LIFE FORM :
Phanerophyte
REGENERATION PROCESSES :
Seed production and dissemination: Western redcedar reproduces from
seeds more readily in open, disturbed areas, such as clearcuts, than in
undisturbed stands [19]. Seed production normally begins when trees are
20 to 30 years old [73]. However, open-grown trees may produce seed by
age 10 [19,50]. Cones average about three to six seeds, but cones are
often numerous and heavy seed crops are common. Average annual seed
crops vary from 100,000 to 1,000,000 seeds per acre
(247,000-2,470,000/ha) in coastal forests and from 22,000 to 111,000 per
acre (54,000-274,000/ha) in the interior [50]. Pure stands of western
redcedar may yield 60,704,168 seeds per acre (150,000,000/ha). Poor
cone crops are rare [19]. Large seed crops occur every 3 to 4 years
[19,51].
Western redcedar seeds are small, 203,000 to 592,000 seeds per pound
(448,000-1,305/Kg) [8,50]. The seeds are dispersed primarily by wind.
However, the seeds have small wings and are not carried more than 400
feet (122 m) from the parent tree [8,48,50].
Germination: Germination is epigeal. Western redcedar seeds germinate
well without stratification and remain viable for at least 7 years
stored dry (5 to 8 percent moisture) at 0 degrees Fahrenheit (-18 deg C)
[50]. Stratification may improve the germination of some dormant seed
lots. However, in others it may lower the germination capacity [51].
Haig [34] reported germination rates of 73 percent, and Schopmeyer [69]
reported germination rates of 34 to 90 percent.
Mineral soil has been found to be a better seedbed in many environments
than moss or duff, which may dry out rapidly [19,21,50]. Heavily shaded
seedbeds have been associated with the best germination of western
redcedar in British Columbia [19]. Rotten wood that is in contact with
the soil is the preferred seedbed in old western redcedar groves [50].
Graham [26] found that germination was best on burned surfaces.
Seedling development: Western redcedar seedling survival is low [8,50].
Drought and high soil temperatures damage seedlings grown in full
sunlight [8,40]. Fungi, birds, insects, and smothering by fallen leaves
of deciduous shrubs are some other causes for the high mortality of
western redcedar seedlings [8,19]. Seedlings grow best in partial
shade, although they may fail on heavily shaded sites due to poor root
penetration [19]. Seedlings show high resistance to root flooding [47]
and respond well to removal of competition [57]. In one study, removal
of shrubs resulted in an increase in height growth of western redcedar
compared to unreleased trees [26].
Of all conifers in the northern Rocky Mountains, western redcedar and
western hemlock seedlings grow the slowest. Annual height growth of
western redcedar seedlings is highly variable, from less than 0.39
inches (1 cm) in dense stands to over 7.5 inches (19 cm) in thinned
stands [26].
Vegetative reproduction: Communities with closed canopies favor
vegetative reproduction over sexual reproduction [32]. Western redcedar
generally relies on vegetative reproduction in climax old-growth stands
with high soil moisture throughout the growing season [21,27]. The
frequent absence of adequate moisture in the upper soil layers of
well-drained sites often is responsible for western redcedar's reduced
ability to vegetatively reproduce on upland sites [28]. Three natural
types of vegetative reproduction occur: (1) layering, (2) rooting of
fallen, living branches that have been torn off by wind or snow and have
fallen on wet soil; and (3) rooting along the trunks of fallen, living
trees [19,32,58].
SITE CHARACTERISTICS :
Western redcedar grows best in maritime climates with cool, cloudy
summers and wet, mild winters. In drier areas west of the Cascades,
western redcedar becomes abundant only on wet sites such as ravines,
along streams, or on poorly drained bottomlands. Near its range limits
in the drier mountains east of the Cascade crest, western redcedar grows
almost exclusively in narrow canyons, where its roots are irrigated all
summer by a mountain stream [8]. In Glacier National Park and the
Selway-Bitterroot Wilderness in Idaho and Montana, western redcedar is
dominant in wet ravines and poorly drained depressions [50].
Precipitation and temperature: Western redcedar occurs on sites that
receive from 35 inches (890 mm) of annual precipitation to more than 260
inches (6,600 mm), mostly as winter rainfall [50]. Western redcedar is
not resistant to frost and is sometimes damaged by freezing temperatures
in late spring or early autumn. When sufficient precipitation is
present, low temperatures appear to limit western redcedar's range. The
northern limits of western redcedar lie between the 52 and 53 degree
Fahrenheit (11.1-11.7 deg C) mean summer temperature isotherms in
southeastern Alaska [50]. Bottomland frost pockets in northern Idaho
are commonly occupied by subalpine fir (Abies lasiocarpa) rather than
western redcedar [51].
Soils: Western redcedar can tolerate a wide range of soil. It is found
on all soil textures and parent materials on Vancouver Island. Coarse
sandy soils are not well suited to the establishment and growth of
western redcedar in northern Idaho and northeast Washington, but rocky
slopes with limited soil development support western redcedars in
southeastern Alaska. Poorly drained organic soils support redcedar
south of Petersburg, Alaska. It grows well on shallow soils over chalk
and can tolerate both acid and alkaline soils conditions. It is able to
survive and grow on soils that are low in nutrients and is found on such
soils over much of its natural range. However, productivity may be
improved by fertilization [50].
Elevation: Elevational ranges of western redcedar have been reported as
follows [19,50,51]:
Alaska - 0 to 3,000 feet (0-910 m)
British Columbia - 0 to 3,900 feet (0-1,190 m)
Oregon - 0 to 7,500 feet (0-2,290 m)
northern Rocky Mountains - 2,000 to 5,900 feet (610-1,798 m)
In coastal regions, western redcedar is commonly associated with the
following shrub and herb species: dwarf Oregon grape (Mahonia nervosa),
stink currant (Ribes bracteosum), Alaska blueberry (Vaccinium
alaskaense), box blueberry (V. ovatum), Pacific rhododendron
(Rhododendron macrophyllum), salal (Gaultheria shallon), threeleaf
anemone (Anemone deltoidea), deerfern (Blechnum spicant), slough sedge
(Carex obnupta), and evergreen violet (Viola sempervirens) [50,51].
In interior regions western redcedar is commonly associated with the
following shrub and herb species: mountain alder (Alnus incana spp.
tenuifolia), Oregon grape (Mahonia repens), common juniper (Juniperus
communis), red raspberry (Rubus idaeus), blue huckleberry (Vaccinium
globulare), Rocky Mountain honeysuckle (Lonicera utahensis), gold thread
(Coptis occidentalis), roundleaf alumroot (Heuchera cylindrica), pine
drops (Pterospora andromedea), and green pyrola (Pyrola chlorantha)
[35,50,51,61].
Common shrub and herb associates of both coastal and interior regions
are as follows: western serviceberry (Amelanchier alnifolia),
thimbleberry (Rubus parviflorus), oceanspray (Holodiscus discolor),
Devil's club, common snowberry (Symphoricarpos albus), lady fern,
western swordfern (Polystichum munitum), prince's-pine (Chimaphila
umbellata), bunchberry dogwood (Cornus canadensis), false Solomon's-seal
(Smilacina stellata), and Pacific trillium (Trillium ovatum) [50,51].
SUCCESSIONAL STATUS :
Obligate Climax Species
Western redcedar is very shade tolerant [8,21,50,51]. It is one of the
most shade tolerant species growing in cedar-hemlock ecosystems of the
northern Rocky Mountains [25]. It is usually considered a climax or
near climax species, but it can be found in all stages of forest
succession. It invades disturbed areas as widely distributed seeds but
regenerates vegetatively in undisturbed areas, tolerating competition in
both [50]. Moisture and soil conditions strongly influence the
successional status of western redcedar. It is climax on wet sites in
the Lake McDonald region of Glacier National Park and on calcium-rich
seepage habitats in British Columbia [51]. In Glacier National Park,
western redcedar enters pioneer communities. The seedlings develop
rapidly in open stands of lodgepole pine (Pinus contorta) and western
larch (Larix occidentalis)[32]. It can survive as a late-seral or
coclimax tree on western-hemlock-dominated sites [21]. In Idaho,
western white pine (P. monticola) stands are slowly replaced by a
western hemlock-western redcedar climax [51].
SEASONAL DEVELOPMENT :
The reproductive cycle of western redcedar occurs over approximately 16
months. Phenology varies between coastal and interior regions. For
trees in the middle of the coastal distribution on Vancouver Island,
pollen and seed cones develop in early June. Pollen forms in late
February or early March of the second season. Pollination occurs within
1 to 2 weeks usually in March but may begin as early as mid-February in
mild coastal areas or as late as early April at higher elevations.
Pollination in March is most common [57]. Fertilization occurs in late
May. Cones mature in October. West of the Cascade Range, cone maturity
is usually reached in 5 months, but in northern Idaho it takes 3 months.
Major seedfall occurs during October and November in both the interior
and coast range [50]. Dry warm weather can cause earlier seed release.
Some seeds may be retained in the cones and gradually shed throughout
the winter [19]. Where moisture and temperature conditions are
favorable, germination can occur in the autumn, winter, or spring [50].
Along the coast region, seeds generally germinate in either fall or
spring [8].
FIRE ECOLOGY
SPECIES: Thuja plicata
FIRE ECOLOGY OR ADAPTATIONS :
Western redcedar fire resistance is low to moderate [21]. Its thin
bark, shallow root system, low dense branching habit, and highly
flammable foliage make it susceptible to fire damage [21,59]. However,
it often survives fire because of it large size [21]. Old western
redcedar trees are commonly fire scarred in northern Idaho [51].
Western redcedar is more severely damaged by fire than any of its
associates along the coast region but is less susceptible than Engelmann
spruce (Picea engelmannii), western hemlock, and subalpine fir in
interior regions [50].
The frequency of fire in western redcedar stands tends to be low
[13,73]. In most of the western redcedar forests from southern British
Columbia to northern California moderate to severe wildfires occur at
long intervals between 50 to 350 years [10]. In streamside and seepage
areas dominated by western redcedar the mean fire interval is greater
than 200 years. In western redcedar habitats on lower and middle slopes
the mean fire interval is 50 to 150 years [82]. In the
Selway-Bitterroot Wilderness those stands dominated by western redcedar
had the longest fire regime [29].
FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find Fire Regimes".
POSTFIRE REGENERATION STRATEGY :
Tree without adventitious-bud root crown
Secondary colonizer - off-site seed
FIRE EFFECTS
SPECIES: Thuja plicata
IMMEDIATE FIRE EFFECT ON PLANT :
Western redcedar is commonly killed by fire. Because of their large
size, however, old western redcedar trees can often survive if they are
not completely girdled by fire [21]. Shallow roots under the duff layer
are often scorched when the duff layer burns and even surface fires may
kill western redcedar [51]. Fire injury to roots can lead to fungal
infection, chronic stress, and growth losses [65]. The most common
causes of fire mortality are root charring and crown scorching [70].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
NO-ENTRY
PLANT RESPONSE TO FIRE :
After fire, western redcedar will readily establish on bare mineral soil
seedbeds via off-site wind dispersed seeds [22,26]. Although unburned
soil benefits western redcedar regeneration more than soil that has been
scorched, slash burning favors western redcedar by creating more mineral
soil surfaces in cutover areas [50].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
Hamilton's Research Papers (Hamilton 2006a, Hamilton 2006b) provide
information on prescribed fire and postfire response of plant
community species, including western redcedar, that was not available when
this species review was originally written.
FIRE MANAGEMENT CONSIDERATIONS :
Riparian stringers supporting western redcedar may act as firebreaks
because the moist duff does not readily burn [21]. Old-age western
redcedar stands have heavy fuel loads, but a large proportion of this
material is in the form of deep duff layers and downed, rotting log
material. These stands could support slow moving fires at best; once
ignited, however, such heavy fuel materials could support long-lasting
fires [29].
Fire-killed western redcedar often shows little deterioration even after
5 years. The bark usually remains intact on dead tree for 5 years.
Fire mortality produces no immediate reduction in strength of western
redcedar poles, and some large trees remain salvageable for almost 100
years after being killed by fire [51].
When slash from decadent western redcedar-western hemlock stands was
burned, a greater proportion of western redcedar than of western hemlock
slash was consumed. This was a result of greater longitudinal and
horizontal fracturing of the western redcedar. When fracturing does not
occur, western hemlock slash is at least as flammable as western
redcedar slash. Fire spreads faster in western redcedar when the slash
from both species is 1 year old. Western redcedar slash does not drop
its foliage. The slash of western redcedar is less flammable when
chipped. One study showed that the fire hazard normally associated with
cutting of western redcedar poles was reduced by skidding entire
pole-size trees to the landing, where the slash was chipped and blown
over the edge [51].
Slash from western hemlock-western redcedar-Alaska-cedar forests produce
greater nutrient losses to the atmosphere when the slash composition has
a greater proportion of Alaska-cedar and western redcedar. One can
expect smaller nutrient losses when western hemlock makes up the
majority of the slash [23]. For further details on slash burning of
western redcedar refer to the fire case study in the Alaska-cedar Fire
Effects Information System species review.
References for species: Thuja plicata
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