Introductory
SPECIES: Picea glauca | White Spruce 



ABBREVIATION : 
PICGLA

SYNONYMS : 
NO-ENTRY


SCS PLANT CODE : 
   PIGL


COMMON NAMES : 
   white spruce
   Canadian spruce
   western white spruce
   Alberta spruce
   Black Hills spruce
   skunk spruce
   cat spruce
   Alberta white spruce
   Porsild spruce


TAXONOMY : 
 The currently accepted scientific name of white spruce is Picea glauca
(Moench) Voss [40].  The genus Picea consists of about 30 species of
evergreen trees found in cool, temperate regions of the northern
hemisphere.  Seven species of Picea, including white spruce, are native
to North America.  White spruce is widely distributed across northern
North America and exhibits considerable geographic variation.  However,
Little [40] thinks it unnecessary to distinguish varieties, although up
to four have been recognized by various other authorities.

Natural hybridization between species of Picea is common.  Engelmann
spruce (P. engelmannii) x white spruce hybrids are common where the
ranges of these species overlap.  Natural crosses between these species
occur from central British Columbia as far south as eastern Washington
and Yellowstone National Park [15].  Within this area trees at low
elevations closely resemble pure white spruce, while pure Engelmann
spruce tends to dominate at higher elevations.  Hybrids between the
species are concentrated on intervening slopes.  Sitka spruce (P.
sitchensis) and white spruce are sympatric in northwestern British
Columbia and southwestern Alaska.  Hybrids occur in this area of
sympatry, and have been classified as Picea X lutzi Little.  Hybrids
between black spruce (P. mariana) and white spruce are relatively rare
[45].


LIFE FORM : 
Tree

FEDERAL LEGAL STATUS : 
No special status

OTHER STATUS : 
NO-ENTRY


COMPILED BY AND DATE : 
Ronald Uchytil/April 1991


LAST REVISED BY AND DATE : 
NO-ENTRY


AUTHORSHIP AND CITATION : 
Uchytil, Ronald J. 1991. Picea glauca. In: Remainder of Citation

DISTRIBUTION AND OCCURRENCE
SPECIES: Picea glauca | White Spruce 



GENERAL DISTRIBUTION : 
White spruce has a transcontinental distribution.  It grows from
Newfoundland, Labrador, and northern Quebec west across Canada along the
northern limit of trees to northwestern Alaska, south to southwestern
Alaska, southern British Columbia, southern Alberta, and northwestern
Montana, and east to southern Manitoba, central Minnesota, central
Michigan, southern Ontario, northern New York, and Maine.  An isolated
population also occurs in the Black Hills of South Dakota and Wyoming
[45].


ECOSYSTEMS : 
   FRES10  White - red - jack pine
   FRES11  Spruce - fir
   FRES18  Maple - beech - birch
   FRES19  Aspen - birch
   FRES20  Douglas-fir
   FRES23  Fir - spruce
   FRES28  Western hardwoods


STATES : 
     AK  ME  MI  MN  MT  NH  NY  SD  VT  WI
     WY  AB  BC  LB  MB  NB  NF  NS  NT  ON
     PE  PQ  SK  YT


ADMINISTRATIVE UNITS : 
     ACAD  ALPO  APIS  DENA  GLAC  ISRO
     LACL  MORR  MORU  PIRO  PIPE  SLBE
     VOYA  WRST  YELL  YUCH


BLM PHYSIOGRAPHIC REGIONS : 
    8  Northern Rocky Mountains
   15  Black Hills Uplift


KUCHLER PLANT ASSOCIATIONS : 
   K012  Douglas-fir forest
   K093  Great Lakes spruce - fir forest
   K095  Great Lakes pine forest
   K096  Northeastern spruce -fir forest
   K102  Beach - maple forest
   K106  Northern hardwoods
   K107  Northern hardwoods - fir forest


SAF COVER TYPES : 
     1  Jack pine
     5  Balsam fir
    12  Black spruce
    15  Red pine
    16  Aspen
    18  Paper birch
    21  Eastern white pine
    24  Hemlock - yellow birch
    25  Sugar maple - beech - yellow birch
    27  Sugar maple
    30  Red spruce - yellow birch
    31  Red spruce - sugar maple - beech
    32  Red spruce
    33  Red spruce - balsam fir
    37  Northern white cedar
    38  Tamarack
    39  Black ash - American elm - red maple
   107  White spruce
   201  White spruce
   202  White spruce - paper birch
   203  Balsam poplar
   204  Black spruce
   206  Engelmann spruce - subalpine fir
   217  Aspen
   218  Lodgepole pine
   251  White spruce - aspen
   252  Paper birch
   253  Black spruce - white spruce
   254  Black spruce - paper birch


SRM (RANGELAND) COVER TYPES : 
NO-ENTRY


HABITAT TYPES AND PLANT COMMUNITIES : 
Climax white spruce forests are widespread across Alaska and
northwestern Canada.  They consist almost entirely of white spruce, but
may have scattered black spruce, paper birch (Betula papyrifera), aspen
(Populus tremuloides), and balsam poplar (P. balsamifera) present [41].
Climax stands are often broken up by extensive seral communities
resulting from forest fires.

In eastern Canada and the northeastern United States, white spruce
occurs as a climax species in pure or mixed stands.  Within the fog belt
of Quebec and Labrador, white spruce forms pure stands near the seaboard
[22].  At climax, it often codominates or forms a significant part of
the vegetation in mixed stands with red spruce (Picea rubens), balsam
fir (Abies balsamea), and black spruce.

In the Black Hills, white spruce habitat types occur at high elevations
and in cool canyon bottoms [33].  

Published classifications listing white spruce as an indicator species
or dominant part of the vegetation in habitat types (hts), community
types (cts), or ecosystem associations (eas) are presented below:

        Area                Classification          Authority

AK                         general veg. cts     Viereck & Dyrness 1980
nw AK                      general veg. cts     Hanson 1953
interior AK                postfire cts         Foote 1983
SD, WY: Black Hills        forest hts           Hoffman & Alexander 1987

AB                         general veg. cts     Moss 1955
w-c AB                     forest cts           Corns 1983
                           general veg. eas     Corns & Annas 1986
BC: Prince Rupert Forest
     Region, Interior
     Cedar-Hemlock Zone    general veg. eas     Haeussler & others 1985
    Prince Rupert Forest
     Region, Subboreal
     Spruce Zone           general veg. eas     Pojar & others 1984 

PQ: Gaspe Peninsula        forest veg. cts      Zoladeski 1988
ON                         forest eas           Jones & others 1983

VALUE AND USE
SPECIES: Picea glauca | White Spruce 



WOOD PRODUCTS VALUE : 
White spruce wood is light, straight-grained, and resilient.  It is an
important commercial tree harvested primarily for pulpwood and lumber
for general construction [45].  Logs are used extensively for cabin
construction [60].  It has also been used for specialty items such as
sounding boards, paddles and oars, cabinets, boxes, and food containers
[44,60].


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Browse:  Livestock and wild ungulates rarely eat white spruce.  Snowshoe
hares sometimes feed heavily on white spruce saplings and seedlings.  On
a cut-over site in northern Alberta, 40 percent of 2- and 3-year-old
white spruce seedlings were browsed by hares [62].  In Alaska, white
spruce needles, bark, and twigs comprise a major portion of the snowshoe
hare's winter diet.  During this time of the year, snow covers many
other foods, leaving only trees and shrubs above snowline available for
hares to browse [64].  Mice and voles eat spruce seedlings [62].  Red
squirrels clip twigs and feed on vegetative and reproductive buds in the
spring [9].  Consumption of leaders and the ends of upper branches by
red squirrels tends to be greatest during poor cone crop years.  Spruce
grouse feed entirely on spruce needles during winter [20].

Seed:  Numerous seed-eating birds and mammals feed on white spruce seed.
White spruce seed is a primary food of red squirrels [9].  White spruce
habitats are favored by red squirrels because of the highly palatable
seeds; squirrel density is much greater in white spruce stands than
black spruce stands [9].  Red squirrels are so dependent on this food
source that population density is directly related to the periodicity of
good seed crops [69].  Mice, voles, shrews, and chipmunks consume large
quantities of white spruce seeds off the ground [45].  Chickadees,
nuthatches, crossbills, and the pine siskin extract seeds from open
spruce cones and eat seeds off the groud [29].


PALATABILITY : 
White spruce is not a preferred browse.  Its palatability is low for
moose, elk, white-tailed deer, and mule deer, but it may be moderately
palatable to bighorn sheep [11,21].  Red squirrels prefer white spruce
seed over black spruce seed [9].


NUTRITIONAL VALUE : 
White spruce seeds are nutritious and are a good energy source for red
squirrels which can survive the winter on a diet consisting entirely of
white spruce seeds.  In Alaska, white spruce seeds averaged 6,615 cal/g
[9].

Data from a nutritional study of white spruce needles collected in the
winter on the Kenai Peninsula, Alaska, are presented below [20]:

             (percent chemical composition and caloric content)
                               range           mean
       
protein                      5.5 - 8.1         6.32
fat                          2.8 - 4.1         3.34
crude fiber                 21.0 - 25.9       23.5
ash                          2.6 - 4.4         3.27
nitrogen free extract       61.4 - 65.0       63.51

Kilogram calories/100 g       486 - 506        494.8



COVER VALUE : 
White spruce provides good wildlife cover.  It may be particularly
important as winter shelter [45,52], especially to caribou which use it
for protection from strong winter winds [30].


VALUE FOR REHABILITATION OF DISTURBED SITES : 
White spruce is useful for long-term revegetation of coal mine
overburden.  In Alberta, it is considered one of the best conifers for
this purpose [63].  White spruce x Engelmann spruce hybrids have been
observed naturally invading coal mine spoils at high elevations in
west-central Alberta [51].  White spruce has also naturally invaded coal
mine overburden in south-central Alaska.  At this location, the
overburden had a clay content of 42 to 44 percent, and was redeposited
on the mined area and graded back to the original contour [18].  On
anthracite strip mine spoils, however, survival of planted white spruce
seedlings was poor to adequate after 5 years [63].

Results of direct seeding of white spruce onto logged-over areas and
abandoned farmland has been variable [53].  The fact that it naturally
invades mine spoils indicates, however, that direct seeding may be
useful on some disturbed sites.  White spruce seed remains viable for up
to 10 years when stored in sealed containers in a cool, dry environment
[53].  The seed requires moist, cool stratification for 60 to 90 days to
break dormancy [53].  Seed from Alberta is an exception, and requires no
presowing treatment.

Two-year-old or older white spruce nursery stock has been planted in
disturbed areas with relatively good success.  Bareroot stock is
recommended for harsh subalpine sites in Alberta where frost heaving may
occur [63].  It is not recommended for planting on steep slopes subject
to erosion.  In northeastern Alberta, overwinter survival of
container-grown and transplanted white spruce seedlings was satisfactory
on amended oil sand tailings [23].

White spruce can be readily propagated by rooted cuttings [45].  Methods
for collecting, processing, storing, and planting white spruce seed have
been described [52].


OTHER USES AND VALUES : 
White spruce can be planted as an ornamental and used in shelterbelt
plantings [45].

White spruce was important to native peoples of interior Alaska [45].
Poles were used to construct dwellings, and bark was used as roofing
material.  Thin, straight, pliable roots were used as rope.  Pitch,
watery sap, and extracts from boiled needles were used for various
medicinal purposes.  Boughs were used for bedding, and rotten wood for
smoking moose hides [34,45]].


MANAGEMENT CONSIDERATIONS : 
Regeneration following timber harvest:  Natural regeneration of white
spruce following timber harvest is unreliable [53].  Spruce seedlings
are, therefore, commonly planted following timber harvest.  For adequate
natural regeneration mineral soil seedbeds are required.  Mechanical
treatments or broadcast burning may be used to expose mineral soils.
Following timber harvest in Alaska, white spruce seedling density was 10
times greater, frequency 2 times greater, and cover 4 times greater on
scalped versus unscalped surfaces [67].  White spruce seedlings die when
shrub competition becomes severe [17].

Pests and diseases:  The most common insect pests and diseases of white
spruce include needle and stem rusts, root diseases, trunk rots,
mistletoe (Arceuthobium pusillum), bark beetles, wood-boring insects,
weevils, the spruce budworm, and the yellowheaded spruce sawfly, all of
which have been discussed in detail [45,53].  

BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Picea glauca | White Spruce 



GENERAL BOTANICAL CHARACTERISTICS : 
White spruce is a native, coniferous, evergreen tree.  It typically
grows as a medium-sized upright tree with a long, straight trunk, and
narrow, spirelike crown.  Because of poor growing conditions at the
northern portion of its range, it may grow as a short, single-trunked
tree, or assume a mat or krummholz form [60].  In Alaska, white spruce
is typically 40 to 70 feet (12-21 m) tall and 6 to 18 inches (15-42 cm)
in diameter [60].  Throughout much of Canada, white spruce's average
height is about 80 feet (24 m) [36].  On good sites throughout the range
of white spruce, individual trees may grow to a height of 100 feet (30
m) or more and attain diameters of 24 to 36 inches (60-90 cm) [45].

The bluish-green needles are 0.75-inch-long (1.9 cm), stiff, and
four-sided [36].  Bark on mature trees is thin, usually less than 0.3
inch (8 mm) thick [53], scaly or smooth, and light-grayish brown.  White
spruce is shallow-rooted.  Rooting depth is commonly between 36 and 48
inches (90-120 cm), but taproots and sinker roots may descend to 10 feet
(3 m) [45].  On northern sites, large roots are usually concentrated
within 6 inches (15 cm) of the organic-mineral soil interface [45].
Trees often retain lower branches, but in dense stands lower branches
are gradually shed, so that eventually the crown occupies about one-half
of the tree's height [36].  Light-brown cones are about 2 inches (5 cm)
long and hang from the branches of the upper crown [36].


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Phanerophyte (mesophanerophyte)
   Burned or Clipped State:  Therophyte


REGENERATION PROCESSES : 
Cone and seed production:  Plants can begin producing seed at 4 years of
age but generally do not produce seed in quantity until they are 30
years of age or older [44].  Good to excellent seed crops occur every 2
to 6 years on good sites [45], but in many areas, good seed crops are
produced only every 10 to 12 years [46,65].  In natural stands cone
production occurs primarily on dominant and codominant trees, with
sporadic production from intermediate and suppressed trees [45].  Seeds
are about 0.12 inch (3 mm) long, with a 0.25- to 0.33-inch-long (6-9 mm)
wing [53].  There are approximately 226,000 seeds per pound [52].

Cone and seed predation:  Red squirrels can reduce cone crops
significantly.  In interior Alaska, they have harvested as much as 90
percent of a cone crop [45].  Their impact on cone and seed production
is greatest during poor or medium cone crop years [69].  Numerous
insects also reduce seed yields.  The spruce cone maggot, the fir cone
worm, and the spruce seed moth are responsible for most loss.  Following
dispersal, small mammals consume considerable amounts of seed off the
ground [45].

Dispersal:  The winged-seeds are dispersed by wind and travel primarily
in the direction of prevailing winds.  Most seed falls within about 300
feet (91 m) of a source, but seeds have been found as far as 1,300 feet
(400 m) from a seed source [6,66].  Seeds found considerable distances
from a source probably travel over crusted snow.  A study in Alaska
found that 50 percent of seed fell within 90 feet (27 m), and 90 percent
of seed fell within 210 feet (64 m) of a 60-foot-tall tree [65].  Red
squirrels disperse seeds also.  White spruce reproduction is common at
squirrel middens [62].

Viability and germination:  White spruce seeds remain viable for only
about 1 to 2 years.  Under natural conditions, seeds overwinter under
snow and germinate in the spring or summer when there is adequate
moisture and soil temperatures have warmed [45].  In Alaska seeds do not
begin germinating until temperatures become favorable, usually in
mid-May [69].  If June is a rainy month, most seeds will germinate.  If
June precipitation is low and seedbeds dry out, germination is delayed
until it rains in July and August [69].  Germanitive capacity is 50 to
70 percent [52].

Seedling establishment:  Seedling establishment is best on mineral soil.
White spruce may also establish on shallow organic seedbeds, but rarely
establish where organic layers are thicker than 2 to 3 inches (5-8 cm)
[55].  Seedlings are frequently found on rotten wood.

Growth:  Seedlings grow best in full sunlight, but are tolerant of low
light, and can withstand many years of suppression [6].  First-year
seedlings are normally less than 1 inch ( 2.5 cm) tall.  After 4 to 6
years, seedlings are less than 20 inches ( 50 cm) tall [45].

Vegetative reproduction:  At the northern treeline in Alaska and much of
Canada, white spruce reproduces almost exclusively by layering [19,45].
In these far north habitats, seed viability is at best low, and
seedlings are rare or absent [19].  Layering may also occur further
south when the lower branches touch the ground and become covered with
moss, litter, or soil.


SITE CHARACTERISTICS : 
White spruce occupies boreal forests.  It is largely confined to
well-drained uplands or river terraces and floodplains.  In interior
Alaska and the Northwest Territories, white spruce forests are usually
found on stream bottoms, river terraces and lake margins, and on warm,
well-drained, south-facing slopes within 5 miles (8 km) of major river
valleys [24,45].  Seral stands of white spruce and aspen, and white
spruce and birch, are common on relatively dry slopes with a south or
southwest exposure, and on dry, excessively drained outwash or deltaic
soils [41].  Across northern Alaska, white spruce grows at the northern
limit of tree growth where it forms open communities on dry exposed
sites [57].  At arctic timberline, white spruce grows in well-drained
soils, often along streams where permafrost has been melted away by
flowing water [73].  In British Columbia and Alberta, white spruce is
widely distributed, occupying floodplains, foothills, and mountains from
2,500 to 5,000 feet (762-1,524 m) in elevation [43,45].  In northeastern
Alberta, open, parklike white spruce forests occur on high ridges, stony
beaches, and dune habitats [43].  In eastern Canada, the Lake States,
and the northeastern United States, white spruce occurs in many
coniferous and mixed coniferous-hardwood forests.  Pure stands or mixed
stands where it is dominant are not widespead.  Conifers, including
white spruce, tend to occupy shallow outwash soils on upper slopes and
flats, while hardwoods or mixtures of hardwoods and spruce are found on
deep glacial till soils of lower slopes [72].

Associated trees:  Alaska associates include paper birch, quaking aspen,
black spruce, and balsam poplar.  In western Canada, associates include
subalpine fir (Abies lasiocarpa), balsam fir, Douglas-fir (Pseudotsuga
menziesii), jack pine (Pinus banksiana), and lodgepole pine (P.
contorta).  In eastern Canada and the northeastern United States
associates include black spruce, paper birch, quaking aspen, red spruce,
balsam fir, northern white-cedar (Thuja occidentalis), yellow birch
(Betula alleghaniensis), and sugar maple (Acer saccharum) [22,45].  In
Wisconsin, white spruce commonly grows with balsam fir [14], and in
Maine, with red spruce [22].

Understory:  In Alaska and across much of western Canada, climax stands
have understories dominated by a well-developed layer of feather mosses.
The total depth of the live moss-organic mat is frequently 10 to 18
inches (25-46 cm) or more [45].  Mixed stands of white spruce and seral
hardwoods have shallower moss layers.  Understory shrubs include green
alder (Alnus viridis ssp. crispa), willows (Salix spp.), mountain
cranberry (Vaccinium vitis-idaea), prickly rose (Rosa acicularis),
highbush cranberry (Viburnum edule), bog birch (Betula glandulosa),
twinflower (Linnaea borealis), black crowberry (Empetrum nigrum),
bearberry (Arctostaphylos uva-ursi), and soapberry (Shepherdia
canadensis) [22,45].  In the Prairie Provinces, common understory shrubs
include snowberry (Symphoricarpos albus), red-osier dogwood (Cornus
stolonifera), serviceberry (Amelanchier alnifolia), and western
chokecherry (Prunus virginiana) [45].

Stand characteristics:  In Alaska and western Canada, climax stands are
usually closed, except near treeline [22].  White spruce stands can be
either even-aged or uneven-aged.  Even-aged stands result from rapid
invasion of white spruce into burned areas.  Uneven-aged stands result
from the slow invasion of spruce seedlings into seral birch or aspen
stands [41].

Soil:  White spruce grows on a wide variety of soils of glacial,
lacustrine, marine, or alluvial origin.  It grows well on loams, silt
loams, and clays, but rather poorly on sandy soils [22].  It is somewhat
site demanding, and often restricted to sites with well-drained, basic
mineral soils.  White spruce grows poorly on sites with high water
tables and is intolerant of permafrost [22].  In the Lake States and
northeastern United States, it grows mostly on acid Spodosols,
Inceptisols, or Alfisols, with a pH ranging from 4.0 to 5.5 [72].  In
the Northeast, it grows well on calcareous and well-drained soils but is
also found extensively on acidic rocky and sandy sites, and in some fen
peatlands in coastal areas [22].


SUCCESSIONAL STATUS : 
White spruce is a long-lived climax tree that gradually replaces pine,
aspen, birch, and/or poplar on well-drained sites.  Less frequently it
occurs as an early successional species, forming pure stands or mixing
with seral hardwoods immediately after fire.  Its ability to
successfully establish following fire depends on fire severity and
intensity, and seed production during the year of the fire [see Plant
Response to Fire].

Following stand destroying fires, dense stands of aspen, birch, and/or
poplar tend to develop quickly, and these successional species are often
scattered throughout all but the oldest white spruce stands [56].  White
spruce seedlings establish under these seral hardwoods, develop and grow
slowly, and eventually replace them.  White spruce-aspen, white
spruce-birch, and white spruce-balsam poplar are common mid-successional
communities that, with the continued absence of fire, will gradually be
replaced by essentially pure stands of white spruce.  Foote [24]
outlined six postfire successional stages for sites capable of
supporting climax white spruce stands in interior Alaska:

  1.  Newly burned (0-1 year after fire) - Following stand destroying
      fires, shoots of prickly rose, highbush cranberry, willows,
      quaking aspen, and birch appear within a year.  White spruce
      seedlings are rare.

  2.  Moss-herb stage (1-5 years after fire) - Herbs cover about 30
      percent of the ground; fireweed (Epilobium angustifolium) is the
      most common.  Mosses cover about 30 percent of the ground.
      Quaking aspen and paper birch each average about 12,150 stems per
      acre (30,000 stems/ha), originating from both sucker shoots and
      seedlings.  Limited white spruce establishment occurs at this
      time.

  3.  Tall shrub-sapling stage (3-30 years after fire) - Tall shrubs or
      tree saplings dominate the overstory, with herbs, tree seedlings
      and litter below.  White spruce seedlings are often present at
      this stage, but not conspicuous.

  4.  Dense tree stage (26-45 years after fire) - Young trees, mostly
      aspen and/or birch dominate the overstory.  The understory is
      dominated by highbush cranberry, prickly rose, twinflower,
      mountain-cranberry, and Labrador-tea.  Willows and herbs decline.

  5.  Hardwood stage (46-150 years) - This stage has well developed
      stands of quaking aspen, paper birch, or mixtures of hardwoods and
      hardwood-white spruce.  As the hardwoods begin to die, codominant
      or understory white spruce form the overstory.

  6.  White spruce stage (150-300+ years) - White spruce eventually
      replaces the hardwoods to form an open to closed canopy.  Some
      hardwoods remain, but the oldest stands tend to be nearly pure
      spruce.

Following fire in upland spruce-fir stands in New England, early seral
stages are dominated by aspen and birch, sometimes pine, and
occasionally pure white spruce [6].  White spruce has invaded much
abandoned agricultural land in this region, forming essentially
even-aged stands.  In northwestern Quebec, white spruce is considered a
long-lived, shade-tolerant climax species.  However, probably due to
spruce budworm outbreaks, white spruce often declines after about 200
years, while paper birch remains abundant [7].  In Wisconsin, white
spruce commonly replaces trembling aspen and paper birch.  White spruce
and balsam fir are the major dominants of the oldest boreal forest
stands in Wisconsin [14].

White spruce is a climax species on the floodplains of large rivers of
interior Alaska and northwestern Canada.  Willows are the first to
colonize siltbars and are in turn replaced by the mid-successional
balsam poplar.  The long-lived white spruce becomes established in low
numbers early on and survives to dominate the climax stage [10,49].  The
climax type on river terraces in southeastern British Columbia is
dominated by white spruce and trembling aspen [25].

In Glacier National Park, white spruce x Engelmann spruce hybrids have
invaded ponderosa pine (Pinus ponderosa) savannas as a result of fire
exclusion [27].


SEASONAL DEVELOPMENT : 
Pollen shedding may occur in May, June, or July, with southern areas
having earlier dispersal than northern areas.  Pollen shedding is
temperature dependent and may vary yearly by as much as 4 weeks at any
given location.  Cones ripen in August or September, about 2 to 3 months
after pollen shed. Timing of seedfall varies yearly depending on
climatic conditions.  Cool, wet weather delays seedfall, but under warm
and dry conditions cones open and seeds disperse early [45,69].  In
general seedfall begins in late August or September [45].  Nienstadt and
Teich [44] reported that most seeds are shed within about 5 weeks after
cones open; however,, Zasada and others [69] reported that over several
years in interior Alaska, 90 percent of white spruce seeds were
dispersed by late December.  Following dispersal, cones remain on the
tree for 1 to 2 years.

FIRE ECOLOGY
SPECIES: Picea glauca | White Spruce 



FIRE ECOLOGY OR ADAPTATIONS : 
Plant adaptations to fire:  White spruce relies on wind-dispersed seeds
which readily germinate on fire-prepared seedbeds to colonize burned
sites.  However, it is not adapted to colonize large burns because (1)
most fires in boreal regions occur in the summer before white spruce
seeds are mature, and thus little or no seed is available for fall
dispersal, and (2) seeds in cones on surviving trees are dispersed over
relatively short distances [55,65].  Since fire-killed trees generally
do not contribute to seedfall, seed for colonizing burns must come from
nearby surviving trees.  Survivors include the occasional mature tree
which survives fire damage, trees escaping fire in small, unburned
pockets, and trees adjacent to burned areas [41].  Occasionally trees
that are severely injured by a summer fire will continue to develop and
disperse viable seed in the fall, even though the trees will die within
1 to 2 years [66].  Because seeds in trees are mature and ready for
dispersal by fall, white spruce can quickly invade areas after fall
burns, especially during good seed crop years [1].

Many researchers report that white spruce is not well adapted to
regenerate following fire because it has nonserotinous cones
[1,2,41,65].  Nearly all seed is dispersed in the fall or winter, but
cones remain on trees for 1 to 2 years after this peak dispersal period
[45].  However, in northern Saskatchewan, Archibold [3,4] found that
some seed remains in cones for up to 2 years and is an important factor
in postfire seedling establishment.  In these studies, an April wildfire
burned through a mixed spruce-hardwood stand containing 1,080 white
spruce trees per acre (2,667/ha) averaging 40 years old.  During the
first postfire year, fire-killed white spruce trees released 540,000
seeds per acre (1,338,000/ha).  During the 2nd postfire year, these dead
trees released 50,000 seeds per acre (123,500/ha), of which 70 percent
germinated in the labratory.

Fire regime:  Across its range, few white spruce stands are older than
200 years.  The oldest are floodplain white spruce stands, some of which
are older than 300 years [32].  Fire frequency in white spruce forest
types is generally between 60 and 200 years [45].  In Alaska, Foote [24]
observed that fire in white spruce forest types was less common than in
black spruce types.  She found numerous white spruce stands older than
100 years, but most black spruce stands sampled were less than 100 years
old.

White spruce stands typically have well-developed organic soil layers.
The depth to which this organic mat is consumed varies depending on the
type of fire.  Sometimes the organic mat is consumed, and mineral soil
exposed [24].


POSTFIRE REGENERATION STRATEGY : 
   off-site colonizer; seed carried by wind; postfire years 1 and 2

FIRE EFFECTS
SPECIES: Picea glauca | White Spruce 



IMMEDIATE FIRE EFFECT ON PLANT : 
White spruce is easily killed by fire.  Its thin bark provides little
insulation for the cambium, and the shallow roots are susceptible to
soil heating.  Surface fires can burn deep into litter and duff,
charring or sometimes consuming roots up to 8 to 9 inches (20-23 cm) in
diameter [41].  Surface fires often spread to white spruce crowns
because the highly flammable fine fuels concentrated under the trees
often produce flames that reach the low-growing, flammable,
lichen-draped branches [1,37].

White spruce seeds on the ground are usually killed by fire because they
have little or no endosperm to protect the embryo from high temperatures
[55].  Cones are not necessarily destroyed by summer fires, but immature
seeds will not ripen on fire-killed trees.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
Viereck and Schandelmeier [61] reported that most fires in spruce stands
in interior Alaska are either crown fires or ground fires intense enough
to kill overstory trees.  The needles of white spruce trees often remain
green following ground fires, but the boles are usually scorched to the
extent that most trees die [24].  In interior Alaska, 100 percent of 40-
to 140-year-old white spruce were killed by a high-severity,
low-intensity surface burn that consumed the entire organic mat,
estimated to be 1 to 5 inches (3-13 cm) thick [31].

Following a late May-early June wildfire in Interior Alaska, Zasada
[66] observed that fire effects on white spruce varied considerably
depending upon fire intensity and severity.  This fire occurred when
white spruce flowering was complete, but fertilization was not.  Fire
effects varied as follows:  

Crowns destroyed - within the zone of the highest fire intensity, crowns
were completely destroyed by fire.

Crowns scorched - near the intense zone tree crowns were scorched by the
heat of the fire.  All these trees were killed.  Small cones did not
develop any further.

Boles scorched or girdled - where underburning consumed most of the
forest floor, tree crowns were hardly affected, but trees received so
much damage to the bole that most died by the end of the first or second
summer after the fire.  Although these trees were severely injured, the
cones and seeds continued to develop.  When seed matured, viability was
about equal to seed from adjacent unburned stands.


PLANT RESPONSE TO FIRE : 
Following fire, white spruce reestablishes via wind-dispersed seeds from
surviving trees in protected pockets or from trees in adjacent unburned
areas.  Within a few years after a fire, white spruce reproduction is
often localized and centered around areas of surviving trees.
Establishment is quite variable, depending on the proximity of surviving
cone-producing trees, seed production during the year of the fire and
immediate postfire years, and amount of mineral soil exposed by the
fire.  Under most circumstances, it can rapidly invade burned sites only
when (1) fire consumes the organic mat and exposes mineral soil and (2)
surviving trees provide a seed source.  When these conditions are met,
white spruce begins to establish seedlings 1 or 2 years after fire.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
White spruce seedling establishment is rapid following fall wildfires
that expose mineral soil but do not burn into the tree crowns.  These
hot surface fires usually kill the trees, but the mature seeds are not
harmed and soon begin dispersing onto the mineral soil.  One year
following a late-August wildfire of this type in interior Alaska, white
spruce frequency was 100 percent, and seedling density was 12,150 per
acre (30,000/ha) [31].  White spruce is less likely to regenerate
following high-severity, low-intensity surface fires in the spring or
summer, because seeds will not develop on the fire-killed trees.
However, if not all trees are killed, some seed will develop over the
summer.  This occurred on portions of a late May-early June burn in
interior Alaska.  One year following this fire, white spruce seedlings
were numerous on portions of the burn where underburning consumed most
of the forest floor, but crowning did not occur.  Although the trees
were severely injured, seeds matured within the cones, so that by fall
1,100 viable seeds were dispersed per square meter.  Seedling frequency
was 100 percent, and density 290 per square meter one growing season
after the fire [66].

In British Columbia and Alberta, in areas where white spruce or white
spruce x Engelmann spruce hybrids are abundant and lodgepole pine
scarce, spruce will establish quickly following fire if sufficient
numbers of seed trees survive or are near the burn.  If lodgepole pine
is present before burning, it usually seeds in aggressively and assumes
a dominant role, quickly overtopping any spruce seedlings [16,35].
However, because of its shade tolerance, white spruce can establish
under a developing pine canopy.  Day [16] sampled lodgepole pine-white
spruce x Engelmann spruce hybrid stands in southern Alberta that
initiated from fires that occurred 29 and 56 years before sampling.  He
found that both pine and spruce initiated large numbers of seedlings
immediately after the fire.  Pine, however, established greater numbers
of seedlings, which rapidly outgrew the spruce and formed a canopy that
was 3 to 4 times the height of the spruce.  Pine seedling establishment
ceased about 30 years after fire, but the shade-tolerant spruce
continued to establish.  Given a sufficient disturbance-free interval,
white spruce will eventually dominate sites where spruce and pine seed
in together following fire.


FIRE MANAGEMENT CONSIDERATIONS : 
Broadcast burning can be used for fuel reduction and site preparation
following logging of white spruce [68].  Survival and early growth of
planted white spruce is enhanced by burning.  Four years after
outplanting of container-grown stock in northeastern British Columbia,
leader length was 36 percent longer on burned versus unburned sites;
however, foliar nutrient content was much lower.  Improvements in growth
on burned sites have been observed for 15 years [5].

Frequent fires can eliminate white spruce from an area because it does
not produce seed in quantity until it is 30 years old or older.  

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Related categories for Species: Picea glauca | White Spruce