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Wildlife, Animals, and Plants
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Introductory
SPECIES: Picea mariana | Black Spruce
ABBREVIATION :
PICMAR
SYNONYMS :
Picea mariana var. brevifolia (Peck)
SCS PLANT CODE :
PIMA
COMMON NAMES :
black spruce
bog spruce
swamp spruce
shortleaf black spruce
TAXONOMY :
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 black spruce, are native to North America. The
currently accepted scientific name of black spruce is Picea mariana
(Mill.) B.S.P. [41].
Natural hybridization between species of Picea is common. Natural
hybrids between black and red spruce (P. rubens) are common where the
ranges of these two species overlap in Nova Scotia, New Brunswick, and
Quebec [65]. Although rare, natural hybrids between black and white
spruce (P. glauca) have been found in Minnesota and other areas [65].
LIFE FORM :
Tree, Shrub
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
NO-ENTRY
COMPILED BY AND DATE :
Ronald Uchytil/May 1991
LAST REVISED BY AND DATE :
NO-ENTRY
AUTHORSHIP AND CITATION :
Uchytil, Ronald J. 1991. Picea mariana. In: Remainder of Citation
DISTRIBUTION AND OCCURRENCE
SPECIES: Picea mariana | Black Spruce
GENERAL DISTRIBUTION :
Black spruce is a wide-ranging and abundant tree. It is distributed
transcontinentally across northern North America. It grows from
Newfoundland and northern Quebec, west across northern Canada to the
west coast of Alaska, south to central British Columbia, south and east
to central Minnesota, and east to Rhode Island and Massachusetts [41].
Black spruce occurs in isolated patches along the southern portion of
its range in southern Wisconsin, southern Michigan, Pennsylvania, and
New Jersey [65].
ECOSYSTEMS :
FRES10 White - red - jack pine
FRES11 Spruce - fir
FRES18 Maple - beech - birch
FRES19 Aspen - birch
FRES23 Fir - spruce
STATES :
AK CT ME MA MI MN NH NJ NY PA
RI VT WI AB BC LB MB NB NF NT
NS ON PE PQ SK YT
ADMINISTRATIVE UNITS :
ACAD APIS DEWA DENA ISRO LACL
PIRO SLBE VOYA WRST YUCH
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
SAF COVER TYPES :
1 Jack pine
5 Balsam fir
12 Black spruce
13 Black spruce - tamarack
16 Aspen
18 Paper 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
107 White spruce
201 White spruce
202 White spruce - paper birch
203 Balsam poplar
204 Black spruce
217 Aspen
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 black spruce forests are widespread across boreal North America.
Six generalized climax types have been outlined [22]. These are:
(1) Black spruce-feather moss - These are well-stocked to dense spruce
stands with a well-developed carpet of feather mosses (Pleurozium
schreberi, Hylocomium splendens, Ptilium crista-castrensis). This type
is most common at the southern and central portion of black spruce's
range.
(2) Black spruce-lichen - These are open woodlands with a
well-developed carpet of reindeer lichens (Cladina spp.). This type
occurs along the northern portion of black spruce's range in the
forest-tundra transition. It remains an open woodland due to the
unfavorable climate.
(3) Black spruce-dwarf shrub - These are closed black spruce stands
with a well-developed ericaceous dwarf shrub layer, and forest floor
dominated by mosses and reindeer lichens. This type occurs in the
central and southern boreal forests.
(4) Black spruce-sphagnum - this type is made up of open to closed
pure black spruce stands on organic or wet mineral soils with
well-developed ericaceous dwarf shrub cover and sphagnum mosses
(Sphagnum spp.) dominating the forest floor. This type occurs
throughout the range of black spruce.
(5) Black spruce-speckled alder (Alnus rugosa) - These are pure or
mixed stands on areas where the watertable is near the surface during
the growing season. Stands have well-developed tall shrub and
herbaceous layers.
(6) Black spruce-sedge - These are very open stands of stunted trees
on wet sites with the ground dominated by sedges and grasses and
well-developed moss layers (but little or no sphagnum mosses). This
type is widely distributed througout boreal regions.
Published classifications listing black spruce as an indicator or
dominant part of the vegetation in community types (cts) or ecosystem
associations (eas) are presented below:
Area Classification Authority
AK general veg. cts Viereck & Dyrness 1980
interior AK postfire cts Foote 1983
MN: Boundary Waters
Conoe Area general veg. cts Ohman & Ream 1971
AB general veg. cts Moss 1955
w-c AB forest cts Corns 1983
w-c AB forest eas Corns & Annas 1986
BC: Prince Rupert Forest
Region, Interior
Cedar-Hemlock Zone general veg. eas Haeussler & others 1984
Prince Rupert Forest
Region, Subboreal
Spruce Zone general veg. eas Pojar & others 1984
ON forest eas Jones & others 1983
VALUE AND USE
SPECIES: Picea mariana | Black Spruce
WOOD PRODUCTS VALUE :
The principal commercial value of black spruce is pulpwood. It is the
most important pulpwood species in Canada, and is commercially important
in the Lake States. It is also used occasionally for lumber and a
variety of other specialty items. The wood is relatively light-weight
but strong [65].
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Browse: Livestock and wild ungulates rarely eat black spruce. Moose
occasionally browse saplings, but white-tailed deer eat it only under
starvation conditions [27]. Spruce grouse feed entirely on spruce
needles during winter. In Alaska, spruce grouse subsist on a diet of
spruce needles from early November through March [21]. Black spruce is
a major food of snowshoe hares, especially in winter. One study found
that consumption of black spruce by hares in interior Alaska varied
seasonally as follows [69]:
Dec-March April May June-Sept Oct-Nov
(percent composition in diet)
needles 38.5 27.6 12.4 12.3 26.0
bark and twigs 17.0 10.0 2.7 1.9 7.8
Seed: Numerous seed-eating birds and small mammals feed on black spruce
seed. Red squirrels consume seed from harvested cones [42]. Mice,
voles, shrews, and chipmunks consume seeds off the ground. Chickadees,
nuthatches, crossbills, grosbeaks, and the pine siskin extract seeds
from open spruce cones and eat seeds off the ground [31,38].
PALATABILITY :
The palatability of black spruce to big game and livestock is low to
nil.
NUTRITIONAL VALUE :
Data from a nutritional study of black spruce needles collected in the
winter on the Kenai Peninsula of Alaska are presented below [21]:
(percent chemical composition and caloric content)
range mean
protein 4.4 - 6.5 5.7
fat 5.5 - 7.1 6.2
crude fiber 21.7 - 23.5 22.47
ash 1.9 - 2.8 2.33
Kilogram calories/100 g 502 - 517 508.9
In this study black spruce had a higher fat and caloric content than
white spruce, but a lower ash content.
Black spruce seeds are not as nutritious as white spruce seeds. In
Alaska, black spruce seeds averaged 6,053 cal/g, about 9 percent less
than white spruce seeds [11].
COVER VALUE :
Black spruce provides good cover for moose. It often grows in dense
stands and on moist substrates, conditions which provide cool bedding
areas for moose [3]. Black spruce also provides good cover for spruce
grouse [37]. In the Lake States, spruce grouse are dependent upon black
spruce stands for much of their habitat needs. The ruby-crowned
kinglet, magnolia warbler, Cape May warbler, and ovenbird commonly nest
in black spruce [38].
VALUE FOR REHABILITATION OF DISTURBED SITES :
Black spruce is recommended for revegetating disturbed sites in boreal
regions. It may be useful for revegetating seismic lines, borrow pits,
abandoned roads, and construction and well sites [10]. In southeastern
Canada, Maine, and Minnesota, black spruce naturally invades
well-drained raised surfaces in abandoned mined peatlands [23]. It can
be established on disturbed sites by direct seeding or by transplanting
nursery-grown seedlings.
Special procedures have been developed for removing black spruce seed
from the semi-serotinous cones [55]. Seeds retain their viability for
several years when stored in sealed containers in a cool, dry
environment [55]. Seeds require no stratification prior to sowing.
They should be sown soon after snowmelt [10]. On peatland sites,
seedling establishment is best when surface organic layers are exposed
by burning or machine scarification. On upland sites, exposing mineral
soils before sowing is essential [38].
On well-drained soils 8- to 12-inch-tall (20-43 cm) bareroot transplants
show good growth and survival when planted directly into organic layers
[4]. Thus, site preparation which removes organic layers should not be
undertaken when transplanting black spruce on uplands. Transplant
survival and growth are generally better following summer than spring
outplanting [4]. In northeastern Alberta, overwinter survival of
container-grown and transplanted black spruce seedlings was satisfactory
on amended oil sand tailings [24].
Black spruce can be readily propagated by root cuttings [4].
OTHER USES AND VALUES :
Black spruce is still harvested for Christmas trees, but recently the
amount harvested from natural stands has declined [65]. In the past,
specialty items made from black spruce included healing salves from the
gum, antiscorbutic and diuretic beverages from twigs and needles, and
rope from the roots [55].
MANAGEMENT CONSIDERATIONS :
Timber harvest: Clearcutting in strips or patches is generally
considered to be the best silvicultural system for managing black spruce
[38,65]. Most sites are broadcast burned and seeded naturally from
nearby uncut stands [6]. Direct seeding has been used on large
clearcuts in Minnesota. On these cuts, seeding rates were 4 ounces (112
grams) per acre (approx. 100,000 seeds) to achieve 60 percent stocking,
but 2 to 3 ounces (56-84 grams) were adequate on well-prepared sites
[37]. On brushy sites, aerial spraying herbicides has been used to
release black spruce [38].
Pests and diseases: Eastern dwarf mistletoe (Arceuthobium pusillum) is
the most serious disease of black spruce in the Lake States and eastern
Canada. It is less frequent in the West, and completely absent in
northwestern Canada and Alaska. Infection results in reduced vigor,
witches brooms, deformed trees, and death. Control is possible through
silvicultural management [27,65]. Black spruce is susceptible to
numerous needle rusts and fungi which result in defoliation and reduced
vigor. These diseases usually remain at low levels but may become
epidemic [65]. Wind breakage is caused by butt and heart rots which are
common in 70- to 100-year-old stands on upland sites and 100- to
130-year-old stands on organic sites [27,37]. The spruce budworm
defoliates black spruce; however, black spruce is less susceptible than
white spruce, red spruce, or balsam fir (Abies balsamea). Black spruce
trees most likely to be attacked are those growing with balsam fir and
white spruce [27]. Numerous other insects attack black spruce but only
occasionally cause serious damage [27,65].
Flooding: Black spruce is susceptible to damage from flooding and
disruptions in normal groundwater movements. Trees have been killed
over large areas where newly constructed roads impede water movements
and where beavers dam drainage ditches or small streams [27].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Picea mariana | Black Spruce
GENERAL BOTANICAL CHARACTERISTICS :
Black spruce is a native, coniferous, slow-growing, small upright tree
or dwarf shrub. Trees have a straight bole with little taper, and a
narrow, pointed crown made up of short, compact, drooping branches with
upturned ends [35]. Throughout much of its range, trees average 30 to
50 feet (9-15 m) in height and 6 to 10 inches (15-25 cm) in diameter at
maturity [35]. In Alaska, black spruce is occasionally found as a
medium-sized tree up to 60 feet (18 m) tall and 9 inches (23 cm) in
diameter, but it is usually only 15 to 30 feet (4.5-9 m) tall and 3 to 6
inches (7.6-15.2 cm) in diameter [66]. Growth is quite variable
depending upon site conditions. In swamps in northeastern Minnesota,
black spruce showed progressively slower growth rates from the border
toward the center of swamps. Eighty-year-old trees at a swamp border
were, on average, 60 feet (18 m) tall, but only 120 feet (37 m) away at
the center of the swamp trees were only 20 feet (6 m) tall [40].
Needles are 0.5-inch-long (1.2 cm), stiff, four-sided, dark bluish green
[35]. The bark is thin, scaly, and grayish brown. The root system is
shallow and wide spreading. Black spruce is very susceptible to
windthrow except in the densest stands. Most roots are found in the
upper 8 inches (20 cm) of the organic soil horizons [65]. Cones occur
in dense clusters in the upper part of the crown. They are 0.6- to
1.25-inch-long (1.5-3.2 cm), nearly round or egg shaped, dull gray or
blackish, and remain on the tree for several years [66].
In the extreme northern portion of its range, trees may be only 10 to 20
feet (3-6 m) tall and 1 to 2 inches (2.5-5 cm) in diameter when 100 to
200 years old [27]. In these extreme environments, needles and cones
may be only one-half of their normal size [35]. Black spruce may form
krumholz in the far north; here plant height equals the average snow
coverage [20].
RAUNKIAER LIFE FORM :
Undisturbed State: Phanerophyte (megaphanerophyte)
Undisturbed State: Phanerophyte (microphanerophyte)
Undisturbed State: Phanerophyte (nanophanerophyte)
Burned or Clipped State: Therophyte
REGENERATION PROCESSES :
Cone and seed production: Black spruce has the smallest seeds of North
American spruces, averaging 404,000 per pound (890,000/kg) [55]. Trees
can begin producing seed when as young as 10 years old but generally do
not produce seed in quantity until they are 30 years old or older [65].
Some seed is produced every year, and bumper crops are produced about
every 4 years [65]. Since seed crops seldom fail and the
semi-serotinous cones release seeds over a period of several years,
stands that are 40 years old or older nearly always have a continuous
supply of seeds. Annual seedfall in mature black spruce stands has been
reported at [29,65]:
200,000 seeds/acre (494,000/ha) in Minnesota
990,000-1,692,000 seeds/acre (2.45-4.2 million/ha) in Ontario
404,000-1,900,000 seeds/acre (1.0-4.9 million/ha) in ne Ontario
240,000-528,000 seeds/acre (590,000-1,300,000/ha) near Inuvik, NWT
344,000 seeds/acre (850,000/ha) in central Alaska
Dispersal: Black spruce cones are semi-serotinous. They remain
partially closed and disperse seed over a period of several years. In
Minnesota, cones release about 50 percent of their seeds within 1 year
after ripening, and about 85 percent within 5 years [68]. In
northeastern Ontario, cones contained about one-half of their seeds
after 5 years [29]; however, another study in Ontario found that after 3
years, cones retained only about 2 percent of their seeds [65]. Some of
this variation is probably related to weather, as cones tend to open in
warm, dry weather but remain closed in cold, wet weather [29].
Dispersal occurs throughout the year but is greatest in the winter and
spring and lowest in the fall [65]. In northeastern Ontario, 58 percent
of annual seedfall is dispersed in March, April, and May [29]. In
Minnesota, annual seedfall was: 9 percent in August, 19 percent in
September, 38 percent from October through April, 13 percent in May, 14
percent in June, and 7 percent in July [27]. Most seed is dispersed
within about 264 feet (80 m) of a source [36].
Viability: Germinative capacity of recently ripened seed is high, about
88 percent [55]. Viability decreases with age. In northeastern
Ontario viability of filled seed averaged 53 percent for 1- to
5-year-old seed, 20 percent for 6- to 10-year-old seed, and 5 percent
for 11- to 15-year-old seed [29].
Germination and seedling establishment: Black spruce seeds will
germinate and establish on numerous substrates if the seedbed remains
moist but not saturated, and free of competing vegetation [37].
Seedling establishment is best on mineral soils, sphagnum mosses, and
rotten wood [16,65]. Seeds readily germinate on sphagnum mosses,
probably because they are continually moist; however, seedlings are
often overtopped and engulfed by the fast-growing sphagnums [27].
Feather mosses provide a poor seedbed because they have a tendency to
dry out, but black spruce can establish in feather moss during wet
years.
Growth: Seedlings are shade tolerant, but growth is fastest in full
sunlight [37]. Seedlings rarely grow more than 1 inch (2.5 cm) in their
first growing season. Three-year-old seedlings are commonly 3 to 5
inches tall [27]. Roots of 1st-year seedlings may penetrate to 2 inches
(5 cm) on upland soils, but when growing in mosses roots rarely reach
depths of 1.5 inches (3.8 cm) after two growing seasons [27].
Vegetative reproduction: Layering occurs when black spruce's lower
branches become covered with mosses or litter. It is particularly common
in swamps, bogs, and muskegs. At the northern limit of trees across
Alaska and northern Canada, black spruce reproduces almost entirely
through layering [19]. Seeds may be produced, but few if any are
viable.
SITE CHARACTERISTICS :
Black spruce grows on both lowland and upland sites. At the southern
portion of its range it is found primarily on wet organic soils, but
farther north its abundance on uplands increases. In the Lake States
and in New England, black spruce is most abundant in peat bogs and
swamps, but is also common on transitional sites between peatlands and
uplands. In these areas it is rare on uplands, except in isolated areas
of northern Minnesota and the Upper Peninsula of Michigan [36]. In
Alaska, black spruce occupies poorly drained areas, such as cold wet
flats, muskegs, and bogs, but is also common on north-facing slopes
within 5 miles (8 km) of major rivers, and on upland slopes of all
exposures more than 5 miles away from major rivers where white spruce is
absent [25,66]. It often dominates sites in Alaska that are underlain
by permafrost.
Stand characteristics and associated trees: Because fires occur at
frequent intervals in black spruce forests, most stands are even-aged
[see Plant Adaptations to Fire]. Black spruce commonly grows in pure
stands on organic soils and in mixed stands on mineral soils [65]. On
loamy or clayey moist uplands throughout the boreal region, associates
include white spruce, quaking aspen (Populus tremuloides), balsam fir,
paper birch (Betula papyrifera), and tamarack (Larix laricina) [27]. On
organic sites in the Lake States and New England, black spruce mainly
grows in pure stands, but it is also found in mixed conifer swamps with
tamarack, northern white-cedar (Thuja occidentalis), balsam fir, and
eastern white pine (Pinus strobus) [17,36]. Associated trees on mineral
soil sites in this region include quaking aspen, paper birch, white
spruce, and jack pine (Pinus banksiana) [36]. Jack pine is an
especially common associate on dry, sandy and rocky sites [38]. Other
common associates in the Lake States, especially in transitional areas
between organic soil lowlands and mineral soil uplands, include black
ash (Fraxinus nigra), red maple (Acer rubrum), American elm (Ulmus
americana), balsam poplar (Populus balsamifera), eastern white pine, and
red pine (Pinus resinosa) [36]. In northern New England and
southeastern Canada, black spruce is sometimes associated with red
spruce [38]. In western Canada, it may be found with lodgepole pine
(Pinus contorta), subalpine fir (Abies lasiocarpa), and white spruce
[27].
Understory: A conspicuous characteristic of black spruce stands is a
nearly continuous ground cover of feather mosses, sphagnum mosses,
and/or reindeer lichens. Reindeer lichens tend to dominate the ground
cover in northern open black spruce woodlands. Associated shrubs in
bogs and swamps include Labrador-tea (Ledum groenlandicum), leatherleaf
(Chamaedaphne calyculata), kalmia (Kalmia spp.), downy andromeda
(Andromeda glaucophylia), bog blueberry (Vaccinium uliginosum), mountain
cranberry (V. vitis-idaea), shrub birches (Betula glandulosa, B.
pumila), and creeping snowberry (Gaultheria hispidula). In the Lake
States, speckled alder and redosier dogwood (Cornus sericea) are the
principal shrubs in some black spruce swamps. Upland shrubs in the East
include mountain maple (Acer spicatum), beaked hazel (Corylus cornuta),
alders (Alnus spp.), and red raspberry (Rubus idaeus) [27,36,65].
Forest floor: Stands in Alaska typically have a thick organic mat.
Live moss-organic matter may be up to 20 inches (50 cm) thick [60].
Forest floor temperatures are typically lower and moisture content
higher in black spruce forests than in white spruce, paper birch,
quaking aspen, or blasam fir forests [59].
Soils and landforms: Black spruce is tolerant of nutrient-poor soils.
It is commonly found on poorly drained acidic peatlands [17,20]. On
peatlands in Minnesota, black spruce grows best on dark brown to
blackish, moderately decomposed peat that contains much partially
decomposed wood [27]. Poor growth occurs on muskegs with thick
accumulations of poorly decomposed yellowish-brown sphagnum peat. In
the northeastern United States, black spruce commonly grows on peat
soils that are deeper than 12 inches (30 cm) [6]. On the Laurentian
Shield in Minnesota, black spruce is frequently found on 10 feet (3 m)
of peat, and sometimes on peat 60 feet (18 m) deep [27]. On mineral
soil sites in northern Minnesota and adjacent Ontario, black spruce
occurs on gravelly and bouldery loams and shallow soils over bedrock
[27]. Throughout much of Canada, upland black spruce stands tend to
occur on moist to somewhat wet clay loams and clays on long gentle
slopes and lowlands [27]. In New Brunswick, Nova Scotia, and parts of
Quebec, it occurs on sandy and gravelly outwash plains, river terraces,
eskers, and related landforms [27]. In Alaska, black spruce stands
underlain by permafrost tend to have shallow, mineral soil profiles
[59]. Permafrost tables under black spruce stands in Alaska are often
as shallow as 12 inches (30 cm) [18].
Elevation: Black spruce is a tree of northern interior lowlands.
Throughout its range it is generally found at elevations between 500 and
2,500 feet (152-762 m) [27].
SUCCESSIONAL STATUS :
Black spruce is considered a climax species over most of its range.
However, some ecologists question whether black spruce forests truly
attain climax because fires in this forest type usually occur at 50- to
150-year intervals, while "stable" conditions may not be attained for
several hundred years [61].
The frequent fire return interval in black spruce forests perpetuates
numerous seral communities. Throughout boreal North America, paper
birch and quaking aspen are seral hardwoods that frequently invade burns
in black spruce types [61]. Black spruce typically seeds in promptly
after fire, and with the continued absence of fire, will eventually
dominate the hardwoods. Throughout much of Alaska, aspen and paper
birch often dominate seral stands until they begin to break up at about
90 years, at which time black spruce attains dominance [25]. Since
fires occur at 100-year or more frequent intervals, seral communities
codominated by aspen and black spruce or paper birch and black spruce
are common and widespread throughout Alaska.
In southeastern Canada and the northeastern United States, balsam fir
and northern white-cedar are more shade tolerant than black spruce and
tend to replace it on "productive" sites [6]. Black spruce is a pioneer
that invades the sedge mat in filled-lake bogs, but it may be preceded
slightly by tamarack. In time black spruce and tamarack may form a
stable forest cover type in swamps. However, as the peat soil is
gradually elevated by the accumulation of organic matter, and the
fertility of the site improves, balsam fir and northern white-cedar will
eventually replace black spruce and tamarack [27,40].
Black spruce tends to replace jack pine and lodgepole pine on relatively
dry sites in western Canada [27].
SEASONAL DEVELOPMENT :
Black spruce flowers in late May or early June in the southern portion
of its range and 1 to 2 weeks later in the northern portion. Female
conelets develop rapidly and contain mature seeds by about 3 months
after pollination (late August or early September). The cones release
seeds gradually over a period of years [65].
Beginning and ending of height growth is generally as follows [27]:
Area Height growth begins Height growth ends
Lake States June 8-20 August 1-10
Maine late May-early June mid to late August
Alberta June 1 August 2
FIRE ECOLOGY
SPECIES: Picea mariana | Black Spruce
FIRE ECOLOGY OR ADAPTATIONS :
Plant adaptations to fire: Black spruce produces seed at an early age,
produces good seed crops regularly, and has persistent, semi-serotinous
cones that release seed slowly over a period of years. Thus, trees
older than 30 years virtually always contain large amounts of seed.
Following fire this large seed supply is released onto burned areas,
allowing rapid seedling establishment. Black spruce seeds are usually
not destroyed by fire because the cones are located in the upper part of
the crown where they are least likely to burn. Thus, even when trees
are killed by fire, cones usually retain viable seed. Furthermore, the
cones are small and occur in tightly compacted clusters, so that some
seeds usually remain viable even after intense crown fires [71].
Immediately following fire large quantities of seeds are released. In
fact, striking recently fire-killed black spruce trees with an axe
causes seeds to fall from scorched cones [40]. Within 60 days of a fire
in an upland black spruce stand in Newfoundland which had an average
tree height of 40 feet (12 m) and basal area of 188 square feet,
1,500,000 seeds per acre (3,705,000/ha) fell [68].
Delayed seedfall and delayed germination are additional postfire
adaptations which ensure that some seed is always available to germinate
and establish during postfire years with favorable growing conditions
[57]. Although large amounts of seed do fall within the 1st postfire
year, small amounts of seed will continue to be released for several
years after fire. Seedfall continued for 8 years following fire in a
70-year-old black spruce stand in interior Alaska [61]. Not all seed
released immediately after fire germinates during the 1st postfire year.
In New Brunswick, only 19 percent of black spruce seed artifically sown
on burned areas germinated in the 1st postfire year, while 25 percent
germinated in the 2nd postfire year [57].
Fire regime: Wildfires are frequent and extensive in black spruce
forests and usually prevent the development of uneven-aged stands [65].
Throughout much of the boreal region of Canada, spruce stands burn at
50- to 150-year intervals [34]. In interior Alaska, most black spruce
stands burn before reaching 100 years in age [25]. Open black spruce
woodlands (also called subarctic woodlands, open boreal forests, or
lichen woodlands) in the Northwest Territories and in northern Quebec
have fire intervals of 100 years or less [9,44,50]. Moving away from
the relatively dry continental boreal forests toward the Atlantic
seaboard, fire intervals become longer. The longest fire-free intervals
for spruce stands probably occur in southern Labrador, where the fire
rotation for black spruce forests is estimated at 500 years [26]. Black
spruce stands occurring in bogs and muskegs experience longer fire-free
intervals than those in nearby upland stands do, and sometimes become
uneven-aged [65].
POSTFIRE REGENERATION STRATEGY :
crown-stored residual colonizer; long-viability seed in on-site cones
FIRE EFFECTS
SPECIES: Picea mariana | Black Spruce
IMMEDIATE FIRE EFFECT ON PLANT :
Black spruce is easily killed by fire because it has thin bark and
shallow roots. Trees are often killed even by low-intensity surface
fires. Crowning is common in black spruce stands because low-growing,
lichen-draped branches are easily ignited by ground fires. Crown fires
typically result in extensive mortality.
In interior Alaska, most fires in black spruce stands are a combination
of ground and crown fires that usually kill all black spruce [25].
Hanson [32] found that all black spruce trees were killed following a
low-intensity surface burn (the top 2 to 4 inches [5-10 cm] of the 6 to
14 inch [15-35 cm] organic mat was consumed) in an open black
spruce-tamarack community in interior Alaska. This site contained 81 to
162 trees per acre (200-400/ha) that ranged from 40 to 178 years old and
1.5 to 3 inches (4-7 cm) in diameter.
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
NO-ENTRY
PLANT RESPONSE TO FIRE :
Closed boreal forests: Following fire, fire-killed black spruce trees
release large quantities of seeds over a period of 1 to 5 years,
resulting in abundant seedling establishment. Numerous authors report
that in boreal forests black spruce seeds in promptly following fire.
[25,42,50,63,68]. In interior Alaska, Foote [25] observed an average of
17,954 black spruce seedlings per acre (44,346/ha) on black spruce sites
which had burned 1 to 5 years earlier. By 50 years after fire, black
spruce stands had naturally thinned to 2,595 stems per acre (6,402/ha);
trees in these stands averaged 2.1 inches (5.4 cm) d.b.h. and were 16.4
to 23 feet (5-7 m) tall.
Open woodlands: In open black spruce woodlands in the Northwest
Territories, black spruce seed production peaks when stand age reaches
100 to 200 years. Fires occurring within this time frame have little
effect on black spruce, as it quickly regenerates from seed. Burning
prepares good seedbeds by removing duff and competing vegetation, and by
altering the thermal regime of the soil, which favors germination
[9,10]. In open woodlands in northern Quebec, black spruce tends to
regenerate quickly after fire, regaining or exceeding prefire density
within 30years [56]. Moving northward from open woodlands to arctic
treeline, the likelihood of successful black spruce seedling
establishment following fire progressively diminishes.
Forest-tundra ecotone: In the forest-tundra ecotone north of open
spruce woodlands in the Northwest Territories, black spruce seed
production is poor, and generally little or no seed is available for
postfire regeneration. Where sparse seed production does occur,
short-term climatic changes over a period of only 1 to 10 years could
exhaust the seed population before a fire, or prevent seed germination
after a fire. Near arctic treeline in the Northwest Territories, black
spruce stands do not regenerate following fire [9,10]. At treeline in
northern Quebec, fires destroy or severely reduce black spruce and cause
a shift toward arctic tundra. Here, black spruce seedlings are only
occasionally found after fire and are usually in depressions at the edge
of burned areas where nearby living trees contain viable seeds [50].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
Following fire, black spruce establishes best where severe burning
exposes mineral soils on upland sites or moist peat on lowland sites
[40,72]. Unburned or partially burned sphagnum mosses are also good
seedbeds, but unburned or partially burned feather mosses are poor
seedbeds [2]. In southern Ontario, feather mosses are not wholly
consumed by fire, but rotting logs under the feather mosses are often
exposed and provide excellent seedbeds [45].
After an experimental burn on black spruce/feather moss sites in
interior Alaska, naturally and artifically sown seeds germinated only
where fire had removed part or all of the organic matter. No seedlings
were found on unburned surfaces or on scorched or charred feather
mosses. In general, exposed mineral soils provided the best seedbeds.
Although seedlings established in areas where the organic layer was
partially consumed, none survived past 3 years. However, on sites where
mineral soil was exposed, seedling frequency was 35 percent after 1
year, and 81 percent after 3 years, as a result of continued natural
seedfall [72]. Following broadcast burning on black spruce/feather moss
cut-overs (area thinned from 2,180 to 800 trees per acre
[5,387-1,977/ha]) in southeastern Manitoba, black spruce seedling
establishment and survival were better on moderate-severity than on
light-severity burns [15]. Five years after burning, stocking was 94
percent in areas where burning depth averaged 4 to 7 inches (10-18 cm),
70 percent in areas where burning depth averaged 2 to 3 inches (5-8 cm),
and 35 percent in unburned areas.
The Wickersham Dome Fire near Fairbanks, Alaska, burned 15,600 acres
(6,300 ha) of mainly black spruce stands ranging in age from 50 to 125
years. For 3 years after this fire, seedling establishment was quite
variable in both lightly burned areas (<50 percent of ground surface
blackened, litter depth reduced an average of 2.25 inches [5.7 cm], and
40 percent of ground vegetation alive 1 year after fire) and heavily
burned areas (>90 percent of ground surface blackened, litter depth
reduced an average of 4 inches [10.3 cm], and nearly all ground
vegetation consumed). In one heavily burned area, seedling
establishment was slow, with only 20 percent of plots containing
seedlings 3 years after the fire for a total of 1,113 seedlings per acre
(2,750/ha). Conversely, another heavily burned area contained 8,500
seedlings per acre (21,000/ha) 3 years after the fire. In
lightly burned areas, unburned and partially burned sphagnum mosses
provided a good seedbed for black spruce so that by 3 years after the
fire there were 16,200 seedlings per acre (40,000/ha) [62].
Black spruce seeds in quickly after fire on relatively dry uplands where
it occurs with jack, red, or lodgepole pine. However, the pines also
seed in aggressively and quickly overtop black spruce. A 35-year-old
burn in northern Minnesota was composed mostly of jack pine and black
spruce. The jack pine were predominantly 33 to 34 years old and 4 to 6
inches (10-15 cm) in diameter, while the black spruce were 28 to 32
years old and 1 to 3 inches (2.5-3 cm) in diameter [33]. Black spruce
is very shade tolerant and can survive in this suppressed condition for
more than 100 years [33] and, in the absence of fire, will eventually
replace the pines [8,65].
In southern Labrador, black spruce seedling establishment following fire
is slow and progressive over a period of 70 to 100 years, resulting in
uneven-aged stands. Within spruce stands in this coastal climate, fires
generally consume very little organic matter and leave only charred
humus. For the first 20 years after fire, seedling establishment is
sporadic and largely restricted to depressions, the edges of water
courses, and exposed mineral soils [26].
FIRE MANAGEMENT CONSIDERATIONS :
Fire behavior: In Alaska, Lutz [42] observed that burning in spruce
stands tends to be more intense on ridges than in valleys, and that
slopes with south or west exposures commonly have more mineral soil
exposed after fire than slopes with north or east exposures. On rocky
slopes or ridges, fires are often unusually severe.
The forest floor under most black spruce stands is made up of a thick
organic mat [18]. Most fires do not consume the entire forest floor,
but produce a mosaic of small patches of exposed mineral soil intermixed
within larger areas of partially consumed organic material [25]. Late
summer fires, however, sometimes consume the entire organic layer and
expose extensive areas of mineral soil [61]. Burning black spruce
stands in Alaska results in increased soil and forest floor temperatures
and nutrient cycling rates. This results in a warmer, more productive
site for 10 to 20 years after fire [59].
Broadcast burning following timber harvest: After clearcutting black
spruce on organic sites in the Lake States, slash is often broadcast
burned to aid natural regeneration. Burning is generally recommended if
there is heavy slash, a feather moss carpet, or abundant tall shrubs,
grasses, or sedges [37]. For natural regeneration to be successful, an
adequate seed supply is necessary, and fuels, including slash, litter,
mosses, and peat, need to be sufficiently dry to allow for reasonably
severe burns [15]. Aksamit and Irving [2] studied black spruce
regeneration on numerous broadcast burned clearcuts in northern
Minnesota. They found that where the understory was dominated by
sphagnum mosses before cutting, black spruce regenerated well regardless
of the burning treatment. In fact, adequate regeneration was obtained
even without burning. On feather-moss-dominated sites, prescribed
burning was necessary to promote black spruce regeneration. For burns
to be effective on feather moss sites, they should be conducted when
100- and 1000-hour fuel moisture is less than 25 percent. However,
burning under these conditions may lead to fire control and mop up
problems, and higher costs. Where speckled alder dominates the
understory before logging, natural regeneration of black spruce after
broadcast burning is quite variable. Low-intensity burns seem to favor
black spruce regeneration, and more severe burns tend to favor other
tall shrubs which compete fiercely with spruce seedlings. Johnston [37]
has outlined broadcast burning techniques for lowland black spruce in
the Lake States.
Eastern dwarf mistletoe control: Prescribed burning can be used to
eradicate eastern dwarf mistletoe in stands of black spruce. For
mistletoe control to be effective, burning must result in 100 percent
black spruce mortality. To ensure complete mortality, live trees can be
cut to provide slash where understories are sparse, and/or diesel oil
can be sprayed on slash when surface fuels are too thin or wet [74].
Frequent fires: Black spruce normally seeds in aggressively following
fire, but it can be eliminated from an area if a second fire occurs
before these young trees reach seed-producing age [1]. Black spruce
regenerated quickly following a 1923 fire in northern Ontario, but 8
years after a second fire in 1929 passed through the area, no black
spruce seedlings were found [46].
FIRE CASE STUDIES
SPECIES: Picea mariana | Black Spruce
CASE NAME :
Lowland Black Spruce Experimental Burns/Manitoba
SEASON/SEVERITY CLASSIFICATION :
spring/light
spring/moderate
STUDY LOCATION :
The study took place 60 miles (97 km) east-southeast of Winnipeg,
Manitoba.
PREFIRE VEGETATIVE COMMUNITY :
The community was a 100-year-old black spruce stand averaging 2,180
trees per acre (5,387/ha). Hummocks and depressions were covered with a
continuous moss carpet. Feather mosses (Pleurozium schreberi,
Hylocomium splendens) comprised 88 percent of this ground cover and
sphagnum mosses (Sphagnum spp.) 12 percent. Scattered shrubs including
Labrador-tea (Ledum groenlandicum), bog birch (Betula glandulosa),
shrubby cinquefoil (Potentilla fruiticosa), and prickly rose (Rosa
acicularis) collectively made up 20 percent of the ground cover. Other
scattered shrubs and herbs included meadow horsetail (Equisetum
pratense), mountain cranberry (Vaccinium vitis-idaea), twinflower
(Linnaea borealis), creeping snowberry (Gaultheria hispidula),
bunchberry (Cornus canadensis), and coltsfoot (Petasites spp.).
The area was logged 2.5 years before the experimental burns were
conducted. The logging operation removed only merchantible timber,
leaving 800 trees per acre (1,977/ha). Slash was 10 to 25 inches deep
(25-64 cm) and covered 52 percent of the ground. Under the slash was a
litter layer of fallen needles about 3 inches (8 cm) deep. The logging
operation reduced feather moss cover from 88 to 41 percent, sphagnum
moss cover from 12 to 6 percent, and shrub cover from 20 to 10 percent,
but increased grass cover from 10 to 20 percent, and sedge cover from 10
to 30 percent.
TARGET SPECIES PHENOLOGICAL STATE :
NO-ENTRY
SITE DESCRIPTION :
The site was typical of many lowland black spruce peatlands. It was
situated on a gentle transition gradient between a well-drained upland
and a poorly drained muskeg. The ground had 10- to 18-inch-high (25-46
cm) peaty hummocks and intermittent depressions. Extending to 10 inches
(25 cm) below the depressions was the upper peat, which was mostly
comprised of fibrous undecomposed debris. Below this was 16 inches (40
cm) of well-decomoposed mucky peat over fine-textured mineral soil.
FIRE DESCRIPTION :
Two areas were burned under different fire prescriptions, resulting in a
light-severity and moderate-severity burn. Conditions before igniting
each burn were as follows:
light-severity burn moderate-severity burn
date May 17, 1967 May 29, 1967
cloud cover (%) 90 70
air temp (F/C) 72/22 75/24
relative humidity (%) 32 31
wind speed (mph/kph) 9/14 9/14
wind direction west southeast
The average flame height for both fires was 3 feet (1 m) with occasional
trees crowning up to 40 feet (12 m). In general fires destroyed slash,
surface litter, and aerial parts of vegetation including feather mosses
and some sphagnum mosses. Stumps and discarded logs were only partially
consumed.
The moderate-severity burn occurred about 2 weeks later than the
light-severity burn when fuels were drier. Peat under exposed feather
mosses was dry to a depth of 1 inch (2.5 cm) on May 17, and to a depth
of 3 inches (8 cm) on May 29. Although burning exposed 95 percent of
the peat on both burns, fire burned deeper into peat on the
moderate-severity burn. On the light-severity burn, average depth of
burning was 3 (8 cm) inches on hummocks and 2 inches (5 cm) in
depressions. On the moderate-severity burn, average depth of burning
was 7 inches (18 cm) on hummocks and 4 inches (10 cm) in depressions.
FIRE EFFECTS ON TARGET SPECIES :
Of the residual black spruce trees left after logging, all were killed
by the fire. Smaller trees were completely consumed, while larger trees
were scorched. Cones in the upper crowns of scorched trees were
unharmed and were responsible for good seedfall after the fire. Five
growing seasons after the fires, stocking was 94 percent on the
moderate-severity burn and 70 percent on the light-severity burn.
Seedling density 5 years after burning was 16,129 per acre (39,856/ha)
on the moderate-severity burn and 3,075 per acre (7,598/ha) on the
light-severity burn. On both burned areas nearly all seedlings were
found on exposed peat. A small percentage were found on sphagnum. The
average seedling height 5 years after burning was 11 inches (28 cm) on
the moderate-severity burn and 8 inches (20 cm) on the light-severity
burn.
FIRE MANAGEMENT IMPLICATIONS :
Burning following timber harvest can be used for the successful
regeneration of black spruce on lowland sites. Black spruce will
establish quickly from natural seedfall if adequate seed trees are
present and the fuels are sufficiently dry to ensure moderately deep
burning.
FIRE CASE STUDIES
SPECIES: Picea mariana | Black Spruce
CASE NAME :
Washington Creek Experimental Fires/Fairbanks, AK
SEASON/SEVERITY CLASSIFICATION :
summer/intense
STUDY LOCATION :
The study was conducted at the Washington Creek Fire Study and Training
Area, about 25 miles (40 km) north of Fairbanks, Alaska.
PREFIRE VEGETATIVE COMMUNITY :
The preburn community was a 70-year-old unevenly spaced black spruce
(Picea mariana) stand with a small amount of paper birch (Betula
papyrifera), green alder (Alnus viridis ssp. crispa), scouler willow
(Salix scouleriana), and Alaska willow (S. alaxensis) scattered
throughout. Low shrubs included mountain cranberry (Vaccinium
vitis-idaia), bog blueberry (V. uliginosum), and Labrador-tea (Ledum
groenlandicum). Moss cover ranged from 72 to 85 percent.
The study area was divided into five units, of which four were burned.
Density, height, and diameter of trees on the four burned units prior to
ignition is presented below:
Unit #
1L 2 3 4L
Density (stems/acre)
black spruce trees 1376 2214 1692 901
paper birch trees 0 300 32 47
black spruce saplings 603 790 3546 759
paper birch saplings 0 32 0 0
Avg height of black
spruce (feet/meters) 11.2/3.4 11.2/3.4 11.5/3.5 10.2/3.1
Avg diameter of
black spruce (in/cm) 1.9/4.8 1.9/4.8 2.0/5.0 1.7/4.3
TARGET SPECIES PHENOLOGICAL STATE :
NO-ENTRY
SITE DESCRIPTION :
The burned area was on a ridgetop that sloped to the southeast.
Elevation was approximately 1,700 feet (520 m). The soil was a shallow
Fairplay silt loam with shattered bedrock and stones at a depth of 8 to
20 inches (20-50 cm). No permafrost was present. The five units, four
burn and one control, ranged in size from 0.22 to 0.37 acres (0.09-0.15
ha), each separated by a fireline several yards wide.
FIRE DESCRIPTION :
Units burned on July 22
One unit was burned on July 22, following a rainless period from July 16
to July 22. The organic layer was high in water content from heavy
rains which fell before July 16. Conditions before ignition were as
follows:
fuel stick moisture content = 6.6 percent
relative humidity = 32 percent
wind speed and direction = 0-5 mph (0-8 kph), south-southeast
temperature = 76 degrees F (24 C)
Burning in unit 2: The fire was ignited at 11:52 am. Heat developed
rapidly and the fire quickly spread to the crowns. The fire moved
across the unit in 7 minutes. The fire was hot from 0 to 10 feet (0-3
m) above the ground, but not within the forest floor. Most of the
organic layer was not consumed.
Units burned on August 26
Three units were burned in the afternoon on August 26. To measure the
effects of high intensity fire, 2 of the units (1L and 4L) were loaded
with additional fuel. Black spruce cut from the fire lines which
bordered the units was laid in rows within these units in June, 1975,
more than 1 year before burning. Unit 1L had 23,636 pounds/acre (26,500
kg/ha) of loaded fuel. Unit 4L had 13,914 pounds/acre (15,600 kg/ha) of
loaded fuel. A total of 16 mm of precipitation fell between August 1
and August 26. Conditions before ignition were as follows:
fuel stick moisture content = 6.6 percent
relative humidity = 40 percent
wind speed and direction = 6-8 mph (9.6-12.8 kph), south-southeast
temperature = 66 degrees F (19 C)
Burning in unit 1L: This unit was ignited at 12:42 pm. Fire spread to
tree crowns within 1 minute. Burning in tree crowns was spotty except
for the center of the unit. Where crowning occurred in one area, flames
reached to 52 feet (16 m). Most active burning was over within 16
minutes, but fire continued to burn in the organic layer for several
hours.
Burning in unit 4L: This unit was ignited at 2:13 pm. The fire
completed its run across the unit in 6 minutes. This fire burned the
hottest of the 4 units burned. The loaded fuel added to the spread and
intensity of the fire and to the depth in which fire burned into the
organic layer.
Burning in unit 3: This unit was ignited at 3:01 pm, and burned
primarily as a slow moving ground fire. It took 29 minutes to burn
across the unit. This was the coolest of the 4 fires.
Indicators of fire intensity and severity for all units is presented
below:
Burn Unit
1L 2 3 4L
avg. water evaporation
from 250 ml water
cans (ml) 65 5 16 107
highest temp (C) height
recorded from heat
sensitive paints at 2.75 m 66 288 66 454
different heights 2.25 m 66 288 66 454
1.75 m 66 288 121 454
1.25 m 121 288 121 660
.75 m 121 288 121 660
.25 m 288 288 288 660
6-15 cm 288 288 288 454
0-5 cm 288 121 288 454
2-3 cm in organic layer --- 43 288 121
highest temp (C) depth in
recorded by heat organic layer
sensitive pellets
surface >83 >83 >83 >83
5 cm 43 43 43 69
10 cm <43 <43 <43 <73
Effect on forest floor
Thickness before burning (cm) 21.6 19.8 23.2 22.4
Thickness after burning (cm) 11.6 14.9 7.8 7.2
Reduction in thickness (percent) 43 24 61 62
percentage of forest floor in
forest floor fire severity classes
(based on ten 1-m2 plots)
heavily burned 24.0 2.0 37.0 49.4
moderately burned 25.0 0.2 11.9 6.1
lightly burned 37.5 97.1 49.3 34.5
scorched 7.5 0.7 1.8 0
unburned 6.0 0 0 0
(based on ten 10-m-long transects)
heavily burned 34.2 2.1 36.8 58.0
moderatley burned 21.0 16.0 16.0 17.0
lightly burned 36.1 75.0 42.0 24.9
scorched 1.0 6.9 4.5 0.1
unburned 7.7 0 1.7 0
FIRE EFFECTS ON TARGET SPECIES :
Because it was difficult to tell if trees were dead or alive immediately
after the fire, damage to black spruce trees and saplings was recorded
as a percentage of needles consumed. Needle consumption by unit is
listed below:
needles consumed unit 1L unit 2 unit 3 unit 4L
(percent) (percentage of trees)
76-100 33 47 9 39
51-75 32 16 38 55
26-50 28 22 44 6
0-25 7 14 9 0
(percentage of saplings)
76-100 76 62 43 78
51-75 16 15 38 20
26-50 8 8 17 2
0-25 0 14 2 0
In general, more needles were consumed on saplings than on tall trees,
indicating that the fires were more intense under the crowns of the
trees.
The fires caused black spruce cones to open and shed seed. Seedfall
began immediately after the fires on August 26. Seedfall in unit 4L was
much lower than in the unburned control. The fire in this unit may have
been intense enough to consume many cones. In the other units, seedfall
in September and October was higher than in the unburned control.
FIRE MANAGEMENT IMPLICATIONS :
Prescribed fires can simulate moderately severe wildfires in black
spruce stands. Within these burns, aboveground vegetation was almost
completely killed, and the forest floor displayed a mosaic of different
burning severities. These four fires show that the moisture content of
forest floor materials is extremely important in controlling the
severity of burning in black spruce stands.
Black spruce seedfall begins shortly after fire. This should result in
abundant seedling establishment beginning in postfire year 1.
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Index
Related categories for Species: Picea mariana
| Black Spruce
|
 |
