SPECIES:  Thuja occidentalis

Introductory
SPECIES: Thuja occidentalis
AUTHORSHIP AND CITATION : 
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. 
U.S. Department of Agriculture, Forest Service, 
Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). 
Available: http://www.fs.fed.us/database/feis/ [].


ABBREVIATION : 
THUOCC

SYNONYMS : 
None


SCS PLANT CODE : 
   THOC2


COMMON NAMES : 
   northern whitecedar
   northern white-cedar
   white-cedar
   white cedar
   eastern white-cedar
   eastern arborvitae
   arborvitae
   arbor vitae
   swamp-cedar


TAXONOMY : 
The currently accepted scientific name for northern whitecedar is Thuja
occidentalis L. [33].


LIFE FORM : 
Tree

FEDERAL LEGAL STATUS : 
No special status

OTHER STATUS : 
NO-ENTRY

DISTRIBUTION AND OCCURRENCE
SPECIES: Thuja occidentalis



GENERAL DISTRIBUTION : 
Northern whitecedar occurs in southeastern Canada and the adjacent
northern United States.  It is distributed from southwestern Nova
Scotia, Prince Edward Island, New Brunswick, the Gaspe Peninsula in
Quebec, and Anticosti Island in the Gulf of Saint Lawrence; west to
northern Ontario and southeastern Manitoba; south to southeastern
Minnesota and northern Illinois; and east through extreme northwestern
Indiana, Michigan, and the New England states.  Island populations occur
in the Appalachian Mountains in western Pennsylvania, West Virginia,
Virginia, and eastern Tennessee.  Local populations also occur in
west-central Manitoba, Wisconsin, Minnesota, Illinois, and Ohio [26,33].
Historical evidence indicates that northern whitecedar is native to
North Carolina as well, but no known native population occurs there now
[10].


ECOSYSTEMS : 
   FRES10  White - red - jack pine
   FRES11  Spruce - fir
   FRES17  Elm - ash - cottonwood
   FRES18  Maple - beech - birch


STATES : 
     CT  HI  IL  IN  ME  MD  MA  MI  MN  NH
     NY  OH  PA  RI  TN  VT  VA  WV  WI  MB
     NB  NS  ON  PE  PQ



BLM PHYSIOGRAPHIC REGIONS : 
NO-ENTRY


KUCHLER PLANT ASSOCIATIONS : 
   K093  Great Lakes spruce - fir forest
   K094  Conifer bog
   K095  Great Lakes pine forest
   K096  Northeastern spruce - fir forest
   K101  Elm - ash forest


SAF COVER TYPES : 
     5  Balsam fir
    12  Black spruce
    13  Black spruce - tamarack
    21  Eastern white pine
    23  Eastern hemlock
    24  Hemlock - yellow birch
    30  Red spruce - yellow birch
    32  Red spruce
    33  Red spruce - balsam fir
    35  Paper birch - red spruce - balsam fir
    37  Northern white-cedar
    38  Tamarack
    39  Black ash - American elm - red maple
   108  Red maple


SRM (RANGELAND) COVER TYPES : 
NO-ENTRY


HABITAT TYPES AND PLANT COMMUNITIES : 
Northern whitecedar is an important species in the wet-mesic coniferous
forests of the northern lowlands [14].  It is often present in the
ecotone between sphagnum bog and upland hardwood communities [15].  It
may dominate rich swamp forests, poor swamp forests, and the cedar
string bog and fen complex [24].

The following published classifications list northern whitecedar as
dominant or codominant:

The vegetation of Wisconsin [14]
Virgin plant communities of the Boundary Waters Canoe Area [37]
Plant communities of Voyageurs National Park, Minnesota, U.S.A. [30]
Habitat classification system for Upper Peninsula of Michigan and
  northeast Wisconsin [11]
Classification and gradient analysis of forest vegetation of Cape
  Enrage, Bic Park, Quebec [49]
The principal plant associations of the Saint Lawrence Valley [16]

MANAGEMENT CONSIDERATIONS
SPECIES: Thuja occidentalis



WOOD PRODUCTS VALUE : 
The wood of northern whitecedar is resistant to decay.  It is used for
products that come in contact with water and soil, such as fence posts,
shingles, paneling, and boats [25,26].  Northern whitecedar logs are
especially popular to use for log cabins because the wood has good
insulating qualities [31].  It is also used for kraft pulp and particle
board [26].


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Northern whitecedar provides food and shelter for wildlife.
White-tailed deer, snowshoe hares, and porcupines heavily browse the
foliage [26].  Northern whitecedar is one of the best winter browse
species for white-tailed deer in the northern Lake States, and it is
often overbrowsed [2].  Moose browse northern whitecedar only when
other food is scarce.  In a study on Isle Royale in Michigan, northern
whitecedar constituted only 0.7 percent of the moose diet, but 5.8
percent of the available food [3].

Pileated woodpeckers feed on carpenter ants that, in turn, nest in and
feed on the heartwood of northern whitecedar [13].  Other birds that
are especially abundant in northern whitecedar forests include
white-throated sparrows, golden-crowned kinglets, yellow-bellied
flycatchers, ovenbirds, northern parulas, winter wrens, Swainson's
thrushes, and numerous warblers.  Blackburnian warblers, Cape May
warblers, ovenbirds, and golden-crowned kinglets breed in the densest
stands [18].


PALATABILITY : 
Northern whitecedar browse is highly palatable to white-tailed deer
[2].


NUTRITIONAL VALUE : 
Northern whitecedar browse is, on average by wet weight, 2.7 percent
protein, 5.2 percent fat, 27.5 percent carbohydrates, and 13.9 percent
crude fiber [44].  It is high in calcium [29].  The browse is considered
highly nutritious [2] and is more digestible to white-tailed deer than
bigtooth aspen (Populus grandidentata) browse [44].


COVER VALUE : 
Stands of northern whitecedar provide thermal cover for white-tailed
deer, moose, and black bear [4,9,39].


VALUE FOR REHABILITATION OF DISTURBED SITES : 
NO-ENTRY


OTHER USES AND VALUES : 
Northern whitecedar is widely planted as an ornamental.  Northern
whitecedar leaf oil is distilled from boughs and used for perfume and
medicines.  The foliage is rich in vitamin C; Native Americans and early
European explorers used it to treat scurvy [26].

Because of its long life span, northern whitecedar is a valuable
species for dendroclimatic research [5].


OTHER MANAGEMENT CONSIDERATIONS : 
There is interest in regenerating northern whitecedar after harvest
because of its forage value to white-tailed deer and because of the
popularity of northern whitecedar log cabins.  In the past, forest
managers have not successfully regenerated this species.  Northern
whitecedar is a slow-growing species, and seedlings are frequently
damaged by heavy browsing.  Many former northern whitecedar stands are
now dominated by balsam fir (Abies balsamea), spruce (Picea spp.), aspen
(Populus spp.), or speckled alder (Alnus rugosa) [31].

A combination of clearcut and shelterwood strips is currently
recommended for harvesting mature stands of northern whitecedar and
reproducing new ones, although other possible methods should be
investigated [27].  If there are less than 10 northern whitecedar
advance regeneration stems per miliacre (2.5 stems/sq m), a prescribed
fire after clearcutting is recommended to eliminate heavy slash, set
back competition, and prepare a seedbed [27,31,46].  See FIRE EFFECTS for
further details on the influence of fire on regeneration.

Sapling stands provide the most browse for deer [26].  Overbrowsing can
retard the growth and even kill a tree if it is less than 7 feet (2.1 m)
tall [2].  A high browse line is frequently evident on larger trees [9].
Fifteen to twenty percent annual usage of foliage might maintain a
constant food supply and still permit a suitable growth rate for
saplings [2].  Thinning of stands improves deer habitat and timber
quality [18].

Northern whitecedar is relatively free of serious insect injury.  The
principal pests are arborvitae leafminer (Argyresthia thuiella) and
black and red carpenter ants (Camponotus pennsylvanicus and C.
ferrugineus).  Northern whitecedar is affected by few serious diseases
[26].

Higher than normal water levels will reduce growth and eventually kill
trees.  Beaver damming and road construction are often responsible for
impeded drainage [26,27].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Thuja occidentalis



GENERAL BOTANICAL CHARACTERISTICS : 
Northern whitecedar is a monoecious, native, evergreen tree with a
narrow, almost columnar crown.  Branches on open-grown trees extend to
the ground.  The trunk is often divided into two or more secondary
trunks of equal size.  Northern whitecedar has scalelike foliage and
fibrous, sometimes shredding bark [25,26].

At maturity northern whitecedar is 40 to 50 feet (12-15 m) tall and 12
to 24 inches (30-60 cm) in d.b.h.  Infrequently it reaches heights of 70
to 80 feet (21-24 m) and diameters of 48 to 60 inches (120-150 cm) [26].
This species is extremely slow growing; after 50 years, it might reach
40 feet (12 m) in height on good sites, but only 15 feet (4.6 m) or less
on poor sites [27].

Northern whitecedar reaches ages in excess of 800 years [5,32].  Two
trees on the Niagara Escarpment in southern Ontario were dated at 935
and 1,032 years [32].

Seedlings develop deep roots in well-drained soil and shallow roots in
saturated soil.  With age, northern whitecedar develops a widespreading
root system which is well adapted to secure water and nutrients from
cracks in rocks [26].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual reproduction:  Northern whitecedar begins producing cones as
young as 6 years of age and begins producing large quantities by age 30.
The best production occurs after age 75.  Good crops occur at 2- to
5-year intervals with intervening years having fair to medium crops.
Seeds have lateral wings and are disseminated by wind.  Seeds are
dispersed a distance of 150 to 200 feet (45-60 m) from the source tree
[13,14,26].

Germination occurs when daytime temperatures reach about 84 degrees
Fahrenheit (29 deg C) [21].  Northern whitecedar germinates on a
variety of substrates including both mineral and organic soils, but
seedling establishment is limited to sites with a constant moisture
supply [26].  Drought is a major cause of seedling mortality [14].
Seedlings that germinate on old stumps are likely to die when the stumps
dry out in late summer, and seedlings that germinate in fast-growing
sphagnum moss (Sphagnum spp.) may be smothered [13].  Seedlings prosper
on recently burned sites [26].

Seedling growth is slow.  Annual height growth averages 3 inches (8 cm)
in the first few years.  Partial light is needed for continued seedling
growth [26].  

Vegetative reproduction:  Under favorable moisture conditions, northern
whitecedar reproduces vegetatively by layering.  Seedlings may
reproduce by layering at age 5 or earlier.  Layering accounts for a
considerable amount of northern whitecedar reproduction.  It is common
in swamp forests where trees often fall or tip slowly.  Trees
established on logs and stumps may fall as their weight increases and
the substrate rots [13,14,26].

Branches on a fallen tree that still has functional roots may begin
growing vertically.  Eventually, with the increased weight of new
growth, the stem will contact the soil and put out adventitious roots
[13].


SITE CHARACTERISTICS : 
Northern whitecedar grows on both uplands and lowlands.  The uplands
are primarily seepage areas, old fields, and limestone cliffs and
boulder fields.  The lowland sites include swamps, streambanks, and
lakeshores.  Northern whitecedar occurs from near sea level to more
than 2,000 feet (600 m) in elevation.  It grows up to 4,270 feet (1,300
m) in the Adirondack Mountains in New York on sites where water is
flowing over rocks [26].

On lowland sites, northern whitecedar generally grows where there is a
strong flow of moderately mineral-rich soil water of near neutral pH
(minerotrophic and weakly minerotrophic swamps) and where the organic
peat is moderately to well decomposed.  The peat is ususally 1 to 6 feet
(0.3-1.8 m) thick and contains rotten wood.  Northern whitecedar grows
best where soils are neutral to moderately alkaline [19,24,26].

On upland sites, northern whitecedar grows primarily in calcareous
soils including calcareous clays and shallow loam overlying broken
limestone [26].

Habeck [50] has suggested that northern whitecedar growing in limestone
uplands is an ecotype distinct from wet lowland northern whitecedar.
Specimens growing on cliffs tend to be deformed with multiple leaders
and twisted trunks, whereas those in wet lowlands tend to be more erect
with well-defined trunks.  However, four studies that looked at tree
morphology [8], seed morphology [7], growth patterns [36], and xylem
water potential [12] found no evidence of ecotypic variation.  There
tended to be more variation within a single site than between lowland
and upland sites.  Seedlings, from seeds collected from the two
contrasting habitats, were grown under different moisture conditions.
Xerically grown seedlings had significantly (p<0.05) more negative xylem
water potential than did seedlings grown under moist conditions,
independent of seed origin.  The seedlings acclimated to the conditions
and demonstrated that northern whitecedar has broad physiological
tolerance to habitat moisture [12].

Overstory associates not mentioned in DISTRIBUTION AND OCCURRENCE
include white spruce (Picea glauca), quaking aspen (Populus
tremuloides), balsam poplar (P. balsamifera), and bigtooth aspen.  Shrub
associates on good sites include speckled alder, mountain maple (Acer
spicatum), red-osier dogwood (Cornus stolonifera), and American fly
honeysuckle (Lonicera canadensis).  Labrador-tea ledum (ledum
groenlandicum), blueberries (Vaccinium spp.), and wintergreen
(Gaultheria procumbens) occur on poorer sites.  Creeping wintergreen (G.
hispidula) occurs on both good and poor sites [26].

Herbs that occur in swamps with northern whitecedar include dwarf red
blackberry (Rubus pubescens), Canada mayflower (Maianthemum canadense),
woodfern (Dryopteris spp.), bunchberry dogwood (Cornus canadensis),
false Solomons-seal (Smilacina spp.), and pitcherplant (Sarracenia
purpurea) [26].  Dwarf lake iris (Iris lacustris), a federally threatened
species endemic to the northern shores of Lake Michigan and Lake Huron,
is found in association with narrow beach strands of northern
whitecedar [43].

The groundcover in northern whitecedar swamp forests includes sphagnum
and other mosses, liverworts, decaying logs, and litter [26].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Although northern whitecedar is generally considered shade tolerant, it
is not as tolerant as balsam fir or sugar maple (Acer saccharum).
Seedlings may only be intermediate in shade tolerance [13,26].  They can
survive severe suppression for several years, but if not released, they
die [26].  Vegetative shoots are more tolerant than seedlings.  Although
some authors [6,30,31] consider northern whitecedar a climax species
because of its longevity and shade tolerance, it cannot reproduce by
seed under dense shade to any marked extent [13].

Northern whitecedar will invade and form even-aged stands in old
fields, openings created by windfall or cutting, and recently burned
swamp sites.  It replaces speckled alder thickets that form in swamps
after fire or after changes in water levels [19,26].  Northern
whitecedar is a pioneer on limestone cliffs and talus slopes.  The
roots grow in small pockets of organic material between rocks [49].
Northern whitecedar succeeds less tolerant, shorter lived species such
as balsam poplar, tamarack (Larix laricina), and black spruce (Picea
mariana) [26].

An uneven-aged old-growth northern whitecedar community occurs on the
Niagara Escarpment in southern Ontario.  This self-sustaining population
occurs in a 3.3 to 16.4-foot (1-5 m) wide strip on the limestone cliff
edge and face [32].  Uneven-aged stands also form on poor lowland sites
where vegetative reproduction is the primary mode of reproduction [26].

Northern white cedar is often succeeded by sugar maple and other more
shade-tolerant species [1,17].  Replacement is usually tree by tree, but
major disturbance (excluding fire) can accelerate succession by
releasing shade-tolerant species [balsam fir, sugar maple, black ash
(Fraxinus nigra)] growing in the understory [1,19].


SEASONAL DEVELOPMENT : 
Flower buds form in autumn and expand the following spring.  Pollen is
dispersed from late April to June.  Cones are full grown by mid-August,
ripen in August and September, and open 7 to 10 days after ripening.
Seeds germinate the following spring or early summer when sufficiently
high temperatures occur [26].

FIRE ECOLOGY
SPECIES: Thuja occidentalis



FIRE ECOLOGY OR ADAPTATIONS : 
Northern white cedar is highly susceptible to fire because of thin bark,
shallow roots, and high oil content [26].  In the understory of a pine,
aspen, or birch (Betula spp.) forest, northern whitecedar acts as a fuel
ladder, carrying fire into the overstory [23].

The risk of fire on most northern whitecedar sites is low, but fires
occasionally originate on drier sites and spread into northern
whitecedar stands [34].  Forested peatlands with a moss ground cover
will not carry spring fires because of a high water table, but forested
fens with a ground cover of sedges (Carex spp.) and grasses carry fire
in the spring when the grasses and sedges are dry.  Most fires in
peatlands with a moss ground cover occur in July, August, or September.
Given sufficient winds, northern whitecedar stands can carry a crown
fire [22].

Northern whitecedar reproduces well on moist organic soils exposed by
fire if a seed source is nearby.  Many northern whitecedar forests in
the Lake States originated after fire [14].  However, if the peat burns
and the humus is destroyed, northern whitecedar may not become
established for a long time [34].

Vogl [47] classifies northern whitecedar as a fire-initiated species in
which fire simultaneously terminates and initiates a long-lived species.
Fires are infrequent and usually severe.  The longest lived specimens
occur in locations where fire is infrequent or nonexistent because of
rocky substrate, sparse ground cover, or low stand density [5].
Examples of such sites include the lakeshores and islands of Lake
Duparquet, Quebec [6] and the Niagara Escarpment in Ontario [32].
Recurring fire may be responsible for the exclusion of northern
whitecedar from some sites [6].


POSTFIRE REGENERATION STRATEGY : 
   Tree without adventitious-bud root crown
   Secondary colonizer - off-site seed

FIRE EFFECTS
SPECIES: Thuja occidentalis



IMMEDIATE FIRE EFFECT ON PLANT : 
Northern whitecedar is usually killed by surface fire.  Large trees may
survive if ground cover is sparse.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Northern whitecedar becomes established by seed on recently burned
sites if a seed source is nearby and the exposed soil is moist
[14,34,47].  Fire serves to remove competition and also removes the moss
layer that dries out in the summer and results in seedling mortality
[31].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire is recommended after northern whitecedar harvest unless
there is ample advance regeneration or if the organic soil is
unsaturated.  Fire removes the heavy slash that prevents regeneration
and also prepares a favorable seedbed [27,46].  However, deep ground
fires can start if the soil is not saturated [27].

If removing slash is the primary objective, prescribed fires are usually
conducted under the following conditions:  3 to 10 days after a rainfall
of more than 0.1 inch (0.3 cm), a minimum relative humidity of 30 to 60
percent, a maximum air temperature of 60 to 90 degrees Fahrenheit (16-32
deg C), and a maximum wind speed of 5 to 15 miles per hour (8-24 km/h).
If the objective is to remove slash and prepare a seedbed, the fire must
be hotter and is usually conducted under the following conditions:  at
least 7 days since a rainfall of more than 0.1 inch (0.3 cm), less than
45 percent relative humidity, air temperatures greater than or equal to
80 degrees Fahrenheit (27 deg C), and 5 to 15 miles per hour (8-24 km/h)
wind speed [27].

The effect of three different slash treatments on northern whitecedar
regeneration after winter clearcutting was investigated.  The treatments
were (1) a prescribed broadcast fire in August to burn the slash, (2)
skidding entire trees out of the study area and delimbing elsewhere, and
(3) leaving the slash in place.  Five growing seasons after
clearcutting, northern whitecedar less than or equal to 23.6 inches (60
cm) tall averaged 33.3 stems per miliacre (8.2 stems/sq m) on burned
plots, and 11.5 and 22.2 stems per miliacre (2.8 and 5.5 stems/sq m) on
full-tree skidded and slash-left plots, respectively.  Ten growing
seasons after clearcutting, northern whitecedar had increased to 40.2
stems per miliacre (9.9 stems/sq m) on burned plots but showed no change
on the other treatment plots [46].

Northern whitecedar slash is a fire hazard for 20 to 30 years because
of its resistance to decay [42].

Prescribed fire can be used to eliminate northern whitecedar that
invades fens in the absence of fire.  A low intensity fall fire (rarely
exceeding 70 BTU/sec/sq ft) resulted in a statistically significant
reduction in the percent cover of northern whitecedar for three
postfire growing seasons.  Annual prescribed burning is recommended for
restoring fens [40,41].

REFERENCES
SPECIES: Thuja occidentalis



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