Leslie A. Viereck and William F. Johnston
Black spruce (Picea mariana), also called bog spruce, swamp spruce, and shortleaf black spruce, is a wide-ranging, abundant conifer of the northern parts of North America. Its wood is yellow-white in color, relatively light in weight, and strong. Black spruce is the most important pulpwood species of Canada and is also commercially important in the Lake States, especially Minnesota.
Picea mariana, generally called black spruce but also known as bog spruce, swamp spruce, and shortleaf black spruce, is a wide-ranging, abundant small to medium-sized conifer tree of northern and boreal North America. It is the most important pulpwood species of Canada and is also commercially important in the Lake States, especially Minnesota.
Black spruce ranges in a broad band from northern Massachusetts to northern Labrador on the Atlantic coast, west across Canada to the west coast of Alaska. Its southern limits consist of isolated patches in northern New Jersey, western Connecticut, Pennsylvania, southern Michigan, southern Wisconsin, southern Minnesota, and southern Manitoba; west across south-central Saskatchewan, Alberta, and central British Columbia. Its northern limit across Canada and Alaska is about that of the northern tree line, although it alternates with white spruce (Picea glauca), tamarack (Larix laricina), and balsam poplar (Populus balsamifera) as the tree-line species at different points.
Black spruce is found from sea level in eastern and northern Canada and western Alaska to 1830 m (6,000 ft) in northern Alberta. It is considered to be a tree of interior lowlands, however, and usually grows at between 150 and 760 m (500 and 2,500 ft). In the mountains of Alaska, Yukon Territory, and Northwest Territories, it is often the tree line species at elevations of 300 to 1220 m (1,000 to 4,000 ft). Local topography and drainage seem to be more important than elevation in determining the range of black spruce.
Black spruce is often a post-fire pioneer on both uplands and peatlands, and fire usually results in the immediate reestablishment of black spruce as long as a seed source is available. Black spruce often dominates fire-prone areas, such as upland ridges, because it produces seed at an early age. It also becomes dominant on poor peatland (bog) sites where it has little competition. Tamarack and black spruce are the first trees to invade the sedge mat in filled-lake bogs.
The principal commercial use of black spruce both in Canada and the United States is for making high quality pulp with balanced strength properties, but it is commercially harvested only in a small portion of its geographical range. Black spruce has a strong, relatively light-weight, yellow-white wood that is also used for lumber and other products. Black spruce Christmas trees were harvested in considerable numbers from natural stands until fairly recently, especially on poor sites in Minnesota. Historically, black spruce has provided some highly specialized products, a few of which are still used occasionally: healing salves from spruce gum (the exuded resin); beverages from twigs and needles; aromatic distillations from needles; and binding material ("wattape")—from long, split roots—for birchbark canoes.
Black spruce is a primary source of food and cover for the spruce grouse, and provides habitat for high-density summer populations of birds including the ruby-crowned kinglet, magnolia warbler, Cape May warbler, and ovenbird. Birds such as the pine grosbeak, pine siskin, and crossbills commonly feed on black spruce seeds.
Excerpted and edited from Viereck and Johnston 1990.
Picea mariana var. semiprostrata (Peck) Teeri
Synonym: Picea mariana forma semiprostrata (Peck) Blake
General: Trees to 25 meters tall (often shrub-like near tree-line), the crown narrowly conic to spire-like or “irregularly subcylindric;” branches short and drooping, frequently layering; twigs not pendent, slender, yellow-brown, hairy; bark gray-brown. Needles evergreen, 0.6-1.5(-2) cm long, 4-angled, stiff and blunt-tipped, waxy and pale blue-green. Seed cones 1.5-2.5(-3.5) cm long, fusiform, purple-brown at maturity; cone scales fan-shaped, broadest near apex, 8-12 mm long, rigid, margin at apex irregularly toothed. Native. The common name refers to the dark (blackish) foliage.
Variation within the species: Black spruce shows north-south clinal variation in photoperiodism, productivity, and other traits, and discrete variants are not recognized at present, except for one. Fernald (1950) recognized “depressed” and “trailing” alpine forms at the rank of forma, but Roland and Smith (1969) and Rouleau and Lamoureux (1992) have treated them as var. semiprostrata. These occur in Keewatin, Quebec, Newfoundland, and Nova Scotia:
However, these are of little significance to NRCS and conservation personnel in the United States.
Black spruce hybridizes with red spruce (Picea rubens) on disturbed sites in eastern Canada and with white spruce in a few places. Reports of natural hybrids between black spruce and white spruce apparently remain unverified.
Distribution: Black spruce occurs across the northern range of North America, from Alaska, Yukon, and British Columbia eastward to Nova Scotia, Newfoundland, New Brunswick, and Québec. It also occurs in the northeastern United States and sporadically in Minnesota, Wisconsin, and Michigan. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.
Bog spruce, swamp spruce, shortleaf black spruce
Regularity: Regularly occurring
Regularity: Regularly occurring
Occurrence in North America
RI VT WI AB BC LB MB NB NF NT
NS ON PE PQ SK YT
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 .
Black spruce occurs in isolated patches along the southern portion of
its range in southern Wisconsin, southern Michigan, Pennsylvania, and
New Jersey .
The commercial range of black spruce is considerably less than its geographic range.
- The native range of black spruce.
In muskegs, bogs, bottomlands, and relatively dry peatlands; at 0-1500 meters. Black spruce usually grows on wet organic soils but productive stands also grow over deep humus, clays, loams, sands, coarse till, and shallow soil mantles. It is often a postfire pioneer on both uplands and peatlands. In fire-prone areas, such as upland ridges, fire usually results in the immediate reestablishment and eventual dominance of black spruce, because it produces seed at an early age.
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 . 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 . 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 . 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 .
Needles are 0.5-inch-long (1.2 cm), stiff, four-sided, dark bluish green
. 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 . 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 .
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 . In these extreme environments, needles and cones
may be only one-half of their normal size . Black spruce may form
krummholz in the far north; here plant height equals the average snow
Habitat and Ecology
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 . 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
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 . 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) . 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) . Jack pine is an
especially common associate on dry, sandy and rocky sites . 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) . In northern New England and
southeastern Canada, black spruce is sometimes associated with red
spruce . In western Canada, it may be found with lodgepole pine
(Pinus contorta), subalpine fir (Abies lasiocarpa), and white spruce
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 red-osier 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 .
Forest floor temperatures are typically lower and moisture content
higher in black spruce forests than in white spruce, paper birch,
quaking aspen, or balsam fir forests .
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 . 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) . 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 . On mineral
soil sites in northern Minnesota and adjacent Ontario, black spruce
occurs on gravelly and bouldery loams and shallow soils over bedrock
. 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 . In New Brunswick, Nova Scotia, and parts of
Quebec, it occurs on sandy and gravelly outwash plains, river terraces,
eskers, and related landforms . In Alaska, black spruce stands
underlain by permafrost tend to have shallow, mineral soil profiles
. Permafrost tables under black spruce stands in Alaska are often
as shallow as 12 inches (30 cm) .
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) .
Key Plant Community Associations
Climax black spruce forests are widespread across boreal North America.
Six generalized climax types have been outlined . 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
(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
(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 water table is near the surface during
the growing season. Stands have well-developed tall shrub and
(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 throughout 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
Cedar-Hemlock Zone general veg. eas Haeussler & others 1984
Prince Rupert Forest
Spruce Zone general veg. eas Pojar & others 1984
ON forest eas Jones & others 1983
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
1 Jack pine
5 Balsam fir
12 Black spruce
13 Black spruce - tamarack
18 Paper birch
32 Red spruce
33 Red spruce - balsam fir
35 Paper birch - red spruce - balsam fir
37 Northern white cedar
39 Black ash - American elm - red maple
107 White spruce
201 White spruce
202 White spruce - paper birch
203 Balsam poplar
204 Black spruce
251 White spruce - aspen
252 Paper birch
253 Black spruce - white spruce
254 Black spruce - paper birch
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K093 Great Lakes spruce - fir forest
K094 Conifer bog
K095 Great Lakes pine forest
K096 Northeastern spruce - fir forest
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES10 White - red - jack pine
FRES11 Spruce - fir
FRES18 Maple - beech - birch
FRES19 Aspen - birch
FRES23 Fir - spruce
Soils and Topography
In central Canada, upland stands tend to be of higher quality than the lowland peat stands. Here, podzolic soils of the order Spodosols and gley soils of the order Inceptisols are common on gentle slopes underlain by clay-loam or clays that have been derived from glacial tills. Many of these clay soils are derived from calcareous materials and are neutral to slightly alkaline in the B or C horizons. The most productive black spruce stands are found on the better drained sites such as sandy glacial deposits, river terraces, and outwash plains of the order Entisols, usually in association with hardwood species.
In the north, black spruce sites are commonly underlain by permafrost (perennially frozen soils). Black spruce seems to be the tree species best adapted to growing on permafrost soils because of its shallow rooting habit. Often the annual thaw depth (active zone) may be as little as 40 cm (16 in). In northwestern Canada, black spruce often grows in alternating organic and mineral soil layers, on hummock-like mounds that overlie the permafrost (57). In central Alaska, black spruce is found on permafrost sites of shallow wind-deposited loess and on old river terraces. At tree line, it is often found on shallow, poorly developed mineral soils. On most black spruce sites on permafrost, wildfire results in a temporary increase in the thaw depth.
Black spruce is found from sea level in eastern and northern Canada and western Alaska to 1830 m (6,000 ft) in northern Alberta. It is considered to be a tree of interior lowlands, however, and usually grows at between 150 and 760 m (500 and 2,500 ft). In the mountains of Alaska, Yukon Territory, and Northwest Territories, it is often the tree line species at elevations of 300 to 1220 m (1,000 to 4,000 ft). Local topography and drainage seem to be more important than elevation in determining the range of black spruce.
Annual precipitation decreases from east to west. In the maritime provinces, it may be as high as 1520 mm (60 in) and in western Alaska as low as 150 mm (6 in), but annual precipitation ranges from 380 to 760 mm (15 to 30 in) in most of the black spruce range. Much of the precipitation is snowfall-from 500 cm (200 in) in eastern Canada to 100 cm (40 in) in western Canada and central Alaska. Mean snow depths are 50 to 75 cm (20 to 30 in) over most of the range but may be more than 100 cm (40 in) in parts of Quebec and Labrador, where snow may persist into late May or early June.
Maximum length of days during the growing season varies from continuous north of the Arctic Circle to about 16 hours near the southern limits of the range. The frost-free period varies from 140 days in the southeastern portions of the range to 60 days or less near tree line.
Habitat & Distribution
Black spruce may produce a few cones as early as 10 years of age, but maximum production occurs between 100 and 200 years. Heavy seed years occur at intervals of 2-6 years and peak crops every 4 years over most of the range. Fires open the cones and accelerate seed release for periods of 60 days to 2-3 years, depending on fire intensity. Viable seed may be dispersed from a cone for up to 25 years, providing a seed supply after fires occur.
Sphagnum mosses can provide a continuously moist seedbed for black spruce, but growth of seedling growth may be slow here because of inadequate nutrients. Feathermosses may provide a suitable seedbed during wet years but may dry out before penetration by the seedling root. Moist mineral soils usually provide good seedbeds, but exposed mineral soil may be too waterlogged or subject to frost heaving in some low-lying areas. Fires that completely remove the surface organic layer usually provide good seedbeds. Seedling mortality seems to be highest on burned duff and lowest on moss and mineral soil surfaces with adequate moisture. Seedlings develop in as little as 10% of full light intensity, but survival and growth are much better in the open.
Layering is an important means of reproduction in black spruce on some sites, especially where rapidly growing mosses cover lower branches. Such layering develops most abundantly in the more open-grown stands and less frequently in dense stands with higher wood volume. It also is common at tree line, probably as a result of depression of the lower branches by snow, and accounts for the presence of "candelabrum" spruce, a circular clump originating from one individual with the tallest tree in the center.
The average maximum age for black spruce is about 200 years, but ages up to 300 years have been reported.
Associated Forest Cover
Because of its broad distribution and varying ecological site characteristics, the Black Spruce forest cover type (Society of American Foresters Type 12, eastern, and 204, western) (11) has been divided into six subtypes: (a) black spruce-feathermoss, most common in the southern and central boreal forest; (b) black spruce-lichen, most abundant near the northern limit of the boreal forest; (c) black spruce-dwarf shrub, in the southern and central portions of the boreal forest; (d) black spruce-sphagnum, on wet soils; (e) black spruce-speckled alder (Alnus rugosa), on waterlogged soils with standing or slowly flowing water; and (f) black spruce-sedge, on peatlands with minerally enriched moving water. Black spruce is also a major component of cover types Black Spruce-Tamarack (Type 13); Black Spruce-White Spruce (Type 253); and Black Spruce-Paper Birch (Type 254).
One of the most conspicuous aspects of many black spruce stands is a nearly continuous ground cover of feathermosses (Hylocomium splendens, Pleurozium schreberi, and Ptilium crista-castrensis) and sphagnum mosses (Sphagnum spp.). On some sites, the moss layer is replaced by nearly continuous mats of lichens, primarily species of Cladonia; this is especially typical of open stands in northern areas where the open lichen woodland is a common vegetation type.
The shrubs associated with black spruce change gradually from east to west. Dominant shrubs in the eastern range include mountain maple (Acer spicatum), beaked hazel (Corylus cornuta), speckled alder, red-osier dogwood (Cornus stolonifera), and red raspberry (Rubus idaeus) on better sites; and low birch (Betula pumila), bog birch (B. glandulosa), bog-rosemary (Andromeda glaucophylla), lambkill (Kalmia angustifolia), Labrador-tea (Ledum groenlandicum), leatherleaf (Chamaedaphne calyculata), and bog-laurel (Kalmia polifolia) on the less productive peatlands. In the western part of the range, littletree willow (Salix arbusculoides), grayleaf willow (S. glauca), Bebb willow (S. bebbiana), prickly rose (Rosa acicularis), American green alder (Alnus crispa), Labrador-tea, bog blueberry (Vaccinium uliginosum), and mountain cranberry (Vaccinium vitis-idaea) are the most important shrubs. The most important herbs, found over most of the range, are panicle bluebells (Mertensia paniculata), fireweed (Epilobium angustifolium), one-sided pyrola (Pyrola secunda), twinflower (Linnaea borealis), bunchberry (Cornus canadensis), wild sarsaparilla (Aralia nudicaulis), false lily-of-the-valley (Maianthemum canadense), starflower (Trientalis borealis), bluejoint reedgrass (Calamagrostis canadensis), and sheathed cottonsedge (Eriophorum vaginatum).
Diseases and Parasites
Several rusts of the genus Chrysomyxa infect both the buds and needles of black spruce. The infection usually remains at low levels but occasionally becomes epidemic and causes defoliation, reduced vigor, and even death of seedlings, saplings, and trees. The cone rust (Chrysomyxa pirolata) often results in greatly reduced seed production but does not kill the tree.
Other diseases of black spruce include a needle cast fungus (Lophodermium spp.), which may cause defoliation and death in local areas; a yellow rust witches' broom (Chrysomyxa arctostaphyli); and a snow blight (Lophophacidium hyperboreum), which may cause extensive damage to black spruce growing in nurseries or young regeneration in the field.
White pocket rots of roots and stems, most commonly Inonotus tomentosus, occur in black spruce and may cause significant damage in some upland stands (4,54).
The spruce budworm (Choristoneura fumiferana) is one of the insects most damaging to black spruce, even though black spruce is less susceptible than red spruce (Picea rubens), white spruce, and balsam fir. Budworm defoliation for several years in succession may result in moderate to severe mortality. The budworm and several other insects often cause serious damage to the flowers or cones, resulting in reduced seed crops (50).
The European spruce sawfly (Diprion hercyniae) is an important pest in eastern Canada but has not invaded western portions of the range. The yellowheaded spruce sawfly (Pikonema alaskensis) and greenheaded spruce sawfly (P. dimmockii) occasionally defoliate black spruce but seldom cause serious damage over large areas. Occasionally, a buildup in populations of the spruce beetle (Dendroctonus rufipennis) in white spruce leads to invasion and death of black spruce, usually where the two species are growing together. The spruce bud midge (Rhabdophaga swainei) may affect height growth in black spruce under some conditions (7). Monochamus wood borers have been known to kill considerable numbers of trees in areas adjacent to strip cuts as a result of initial buildup of populations in logging slash (50).
Snowshoe hare may cause extensive damage to seedlings and saplings when populations of hare are high. Red squirrels gather cones in large quantities and give a peculiar clumped appearance to the top of the tree. Squirrels and microtines may consume a large percentage of the seed supply in some areas during poor seed years.
Black spruce tops are often broken at a height of 3 to 6 m (10 to 20 ft) by snow and ice. In Alaska, one storm in 1967-68 broke 28 percent of the stems in a 160-year-old black spruce stand (46). Windthrow and breakage are two of the principal causes of mortality in black spruce stands in the Lake States; they must be considered when planning for harvesting black spruce stands.
Black spruce is easily killed by both ground and crown fires. It generally rates high in fire hazard, although many peatland stands have a low risk except during very dry periods (26).
Black spruce growing in peatlands is especially susceptible to changes in the water table, which sometimes occur naturally as the result of damming of small streams by beavers, but also result from increased or impeded drainage caused by road construction.
Broad-scale Impacts of Plant Response to Fire
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 . 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 .
Experimental prescribed fires in a black spruce/feather moss stand in
interior Alaska burned at varying fire severities, creating a mosaic
pattern similar to that created by wildfire. Moisture content of the
forest floor was critical in determining fire severity. Black spruce
was expected to regenerate succesfully after these fires . See the Research Project Summary of this study for further information.
After an experimental burn on black spruce/feather moss sites in
interior Alaska, naturally and artificially 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 . 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. 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 . See the Research Project Summary of this study for further information.
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 ( less than 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) .
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 . Black spruce
is very shade tolerant and can survive in this suppressed condition for
more than 100 years  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 .
Fire Management Considerations
Fire behavior: In Alaska, Lutz  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 . 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 . Late
summer fires, however, sometimes consume the entire organic layer and
expose extensive areas of mineral soil . 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 .
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 . 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 . Aksamit and Irving  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 
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 .
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 . 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 .
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  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 . 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 .
Immediate Effect of Fire
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 .
Hanson  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.
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 .
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 . 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 .
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
. 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 . Not all seed
released immediately after fire germinates during the 1st postfire year.
In New Brunswick, only 19 percent of black spruce seed artificially sown
on burned areas germinated in the 1st postfire year, while 25 percent
germinated in the 2nd postfire year .
Fire regime: Wildfires are frequent and extensive in black spruce
forests and usually prevent the development of uneven-aged stands .
Throughout much of the boreal region of Canada, spruce stands burn at
50- to 150-year intervals . In interior Alaska, most black spruce
stands burn before reaching 100 years in age . 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 . Black
spruce stands occurring in bogs and muskegs experience longer fire-free
intervals than those in nearby upland stands do, and sometimes become
More info for the terms: climax, cover, peat
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 .
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 . 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 . 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 . 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 .
Cone and seed production: Black spruce has the smallest seeds of North
American spruces, averaging 404,000 per pound (890,000/kg) . 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 .
Some seed is produced every year, and bumper crops are produced about
every 4 years . 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 . In
northeastern Ontario, cones contained about one-half of their seeds
after 5 years ; however, another study in Ontario found that after 3
years, cones retained only about 2 percent of their seeds . 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 .
Dispersal occurs throughout the year but is greatest in the winter and
spring and lowest in the fall . In northeastern Ontario, 58 percent
of annual seedfall is dispersed in March, April, and May . 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 . Most seed is dispersed
within about 264 feet (80 m) of a source .
Viability: Germinative capacity of recently ripened seed is high, about
88 percent . 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 .
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 .
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 .
Feather mosses provide a poor seedbed because they have a tendency to
dry out, but black spruce can establish in feather moss during wet
Growth: Seedlings are shade tolerant, but growth is fastest in full
sunlight . 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 . 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 .
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 . Seeds may be produced, but few if any are
Growth Form (according to Raunkiær Life-form classification)
Reaction to Competition
Aerial spraying of selective herbicides such as 2, 4-D usually results in effective release of black spruce in brushy stands (26,50). Released trees, however, apparently do not increase growth for about 2 years, and complete release can result in winter drying. Applying pellets of the nonselective herbicide picloram to speckled alder clumps seems to control regrowth longer than 2,4-D but can damage associated black spruce even on well-drained soils (40). Although quite expensive, recently introduced selective herbicides such as glyphosate and hexazinone are also registered for release of spruce. Directions on all herbicide labels should be followed carefully and pertinent precautions heeded.
In spruce-fir stands, mature black spruce apparently responds better to release than white spruce and subalpine fir (Abies lasiocarpa); its diameter increment increases by several times (9). Many intermediate and suppressed black spruce in swamp stands, however, die after heavy cutting (21).
Black spruce has less ability than white spruce to overcome stagnation in even-aged stands because it develops a smaller range of crown classes. Heavy thinning in dense, middle-aged stands increases diameter increment but often decreases volume increment, probably because the site is not fully utilized (47).
Black spruce is often a postfire pioneer on both uplands and peatlands, and fire usually results in the immediate reestablishment of black spruce as long as a seed source is available. Black spruce often dominates fire-prone areas, such as upland ridges, because it produces seed at an early age (20). It also becomes dominant on poor peatland (bog) sites where it has little competition. Tamarack and black spruce are the first trees to invade the sedge mat in filled-lake bogs.
Postfire stands of black spruce are generally even aged. Uneven- to all-aged stands are almost absent in virgin forests because wildfires have been frequent and extensive enough to prevent their development on most sites. Such stands are common on bogs and muskegs, however, where the average interval between fires is probably longer than on uplands. Closed stands that escape fire for more than 100 years usually become uneven aged when black spruce layerings fill the gaps created by deterioration of the overstory (17).
Black spruce grows more slowly than many of the trees and shrubs with which it is associated. Thus, it encounters substantial competition where these species are abundant, particularly when they reproduce from sprouts or suckers rather than from seed. Black spruce is fairly common as an understory tree in jack pine and lodgepole pine stands on dry sites, and succeeds the pines in the absence of fire or harvesting (12). Various mixtures of black spruce, white spruce, and balsam fir-plus northern white-cedar south of the boreal forest-eventually form the main stand on most well-drained sites supporting quaking aspen, paper birch, or balsam poplar. On the better peatland sites, black spruce is often overtopped by quaking aspen, paper birch, tamarack, black ash, or red maple for many years before it becomes dominant. Over much of its range, it is eventually succeeded by balsam fir and, to a lesser extent, northern white-cedar if undisturbed by fire (17).
Black spruce does not compete successfully with balsam fir, northern white-cedar, red maple, balsam poplar, and black ash after cutting in mixed stands on good peatland sites (12). Similarly, harvesting or other disturbances on well-drained sites often lead to high proportions of balsam fir, paper birch, quaking aspen, and balsam poplar, or shrubs (50). Speckled alder is a strong competitor following harvesting on good peatland sites. The spruce, however, is generally able to grow through the alder canopy after several years (50). In Newfoundland and parts of Quebec, there has been extensive conversion of black spruce stands to heathland, dominated by lambkill and Labrador-tea, following repeated fires.
Clearcutting in strips or patches is generally considered to be the best silvicultural system for managing black spruce (21,26,50). Satisfactory reestablishment of black spruce after clearcutting, however, requires an adequate source of reproduction and often some kind of site preparation, such as slash disposal. Uneven- or all-aged management is best applied on poor sites where stands are windfirm. and have abundant layering (27).
Life History and Behavior
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 .
Beginning and ending of height growth is generally as follows :
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
Black spruce may reproduce from shoots originating from roots (12), but this is uncommon. Cuttings from black spruce seedlings can be rooted successfully with periodic misting but without application of auxins (3).
Fires that completely remove the surface organic layer usually provide good seedbeds for black spruce. Slash removal by broadcast burning or full-tree skidding is also beneficial (8,26). Seedling mortality seems to be highest on burned duff and lowest on some moss and mineral soil surfaces with an adequate moisture regime.
Seedbed scarification increases stocking. Under optimal climatic conditions, direct seeding on these scarified surfaces results in seedlings representing 10 to 30 percent of the sown seed (25,56). A sowing of 79,000 seeds per hectare (32,000/acre) should result in at least 60 percent milacre (4.05 m² or 43.56 ft²) stocking of seedlings, which is considered satisfactory (26). Spring sowing results in the best germination and survival, and viability is drastically lowered if germination does not occur during the same year (13,56). Germination is epigeal (42).
Nursery-grown transplants (2-2) survive better, grow faster, and are more economical than seedlings (3-0) when black spruce plantations are established (34,35). Average initial height growth of black spruce seedlings varies from 2.5 cm (1 in) per year on moss to 15 cm (6 in) per year on some mineral soil substrates, but annual growth may be as low as 5 mm (0.2 in).
Seed Production and Dissemination
The cones of black spruce remain partially closed and disperse seed for several years, providing an adequate supply of seeds to reproduce the stand whenever fire occurs. Both the number and viability of the seeds decline rapidly, but some viable seeds may remain in the cones for as long as 25 years (15). In Minnesota, 1-year-old cones contained an average of 50 seeds; 7-year-old cones, 10 seeds; and 19-year-old cones, only 1 or 2 seeds (50). In Newfoundland, the number of seeds per cone was greatly reduced in 4 years (3.7 seeds per cone), but seed germination remained high (above 90 percent) for 12 years and then declined rapidly in older seeds (44).
Black spruce seeds are dispersed throughout the year, but dispersal is highest in the spring and lowest in the fall (16). Fires open the cones and accelerate seed fall for periods of 60 days (55) to 2 to 3 years; the effect apparently varies with fire intensity.
The average annual seedfall is about 490,000/ha (200,000/acre) for Minnesota (26) and substantially higher for Ontario- 2,450,000 to 4,180,000/ha (990,000 to 1,692,000/acre) (15). A maximum of 12,720,000 seeds per hectare (5,148,000/acre) has been reported from Ontario (29). In northern areas, even near tree line, amounts of seed are within the range of those from southern areas, with annual amounts from 590,000 to 1,300,000/ha (240,000 to 528,000/acre) reported from Inuvik in Northwest Territories (6) and 850,000/ha (344,000/acre) from central Alaska (49).
Black spruce has the smallest seed produced by any spruce in North America, averaging 890,000/kg (404,000/lb). Despite their light weight and relatively large wings, the seeds are not commonly dispersed over long distances. Seed dispersal, primarily by wind, is effective up to 79 m (260 ft) from the windward edge of a mature stand (27).
Flowering and Fruiting
The flower buds formed by early August develop rapidly the following spring. Female flowers are receptive and pollen is shed in late May or early June in southern areas of the range and 1 to 2 weeks later in the north. The female conelets then develop rapidly, and at maturity the cones are 1 to 4 cm (0.4 to 1.6 in) long.
Growth and Yield
Volumes of 196 m³/ha (2,800 ft³/acre) are common in 80- to 100-year-old stands on the best peatlands and good upland sites in southern Canada and the Lake States (12). One unmanaged stand had a total volume of 492 m³/ha (7,024 ft³/acre) and a basal area of 53.5 m²/ha (233 ft²/acre) when it was slightly more than 100 years old.
Regional differences in the site index of black spruce are apparently related to climatic factors, whereas differences within regions are associated with soil moisture and nutrients. The moisture-aeration regime influences growth more than the nutrient regime (22). Within peatlands, water chemistry-as determined by water sources and movement-seems to be the principal factor influencing site quality (19).
Black spruce site index curves differ among regions and substrates. For example, the curves are lower at older ages in Newfoundland than in continental Ontario and Quebec. In Ontario, the height-growth patterns of black spruce are different for peatland and upland stands, particularly for site indexes less than 8 m (26 ft) at 50 years and stands older than 80 years (38).
Variable-density yield tables-for stands of various stocking levels-provide better estimates of black spruce growth than normal and empirical yield tables in Ontario (10). They show that both site and stocking influence tree size and volume production. Good sites can grow larger trees than poor sites, whereas stocking has an adverse effect on average d.b.h. and no effect on average height. Merchantable volume, however, increases with stocking except on poor sites (table 1). Variable-density yield tables are also available for black spruce stands in Minnesota (39).
Table 1- Merchantable yields of 120-year-old black spruce stands in Ontario for trees 10 cm (4 in) d.b.h. and larger (adapted from 10) Site index at base age 50 years
Characteristic Stocking¹ at age 30
12.5 m or 41 ft
10.7 m or 35 ft
8.2 m or 27 ft Average height, m Full 17 14 11 Half 17 14 11 Average d.b.h., cm Full 19 13 11 Half 20 15 12 Trees per hectare Full 1,520 2,480 1,490 Half 1,110 1,880 1,780 Basal area, m²/ha Full 42 35 15 Half 36 33 19 Volume, m³/ha Full 298 212 74 Half 260 202 94 Average height, ft Full 57 47 37 Half 57 47 37 Average d.b.h., in Full 7.4 5.3 4.4 Half 8.0 5.9 4.6 Trees per acre Full 615 1,005 605 Half 450 760 720 Basal area, ft²/acre Full 181 152 65 Half 158 145 83 Volume, ft³/acre Full 4,260 3,030 1,050 Half 3,710 2,880 1,350 ¹"Full" refers to a basal area- for trees 2.5 cm (1 in) in d.b.h. and larger- of 18.4 m²/ha (80 ft²/acre) on site index 12.5 m (41 ft) good site/medium site; 13.8 m²/ha (60 ft²/acre) on site index 10.7 m (35 ft); and 4.6 m²/ha (20 ft²/acre) on site index 8.2 m (27 ft) poor site. "Half" refers to one-half of the respective basal areas used for full stocking. Normal yield tables show that rotation age increases as site quality decreases. They also show that the corresponding merchantable volume and mean annual increment decrease greatly from good to poor sites. Averages for black spruce stands of three site classes in the boreal forest of Canada (5, p. 50,91,155,186) are as follows:
Good Medium Poor Rotation age, yr 95 113 132 Merchantable volume, m³/ha 218 160 101 Mean annual increment, m³/ha 2.3 1.4 0.8 Merchantable volume, ft³/acre 3,110 2,285 1,440 Mean annual increment, ft³/acre 33 20 11 Rotation age is the age at which the mean annual increment of merchantable volume culminates and hence yields the most material per unit area per annum.
Little is known about the growth and yield of uneven-aged stands, but they apparently grow more slowly and have lower volumes than even-aged stands (17).
Black spruce plantations reach heights of 1.5 to 4.0 m (5 to 13 ft) 10 years after planting (2,34). A 40-year-old plantation in Minnesota, planted at a 1.2- by 1.2-m (4- by 4-ft) spacing, was 13.3 m (43.6 ft) tall and had a basal area of 32.8 m²/ha (143 ft²/acre) (43). On rich sites in New Brunswick, extensive fast-growing plantations of black spruce have been established for 45-year rotations because the species has good potential height growth and is resistant to spruce budworm.
In experimental studies, fertilization with nitrogen and phosphorus generally results in increased growth in 60- to 90-year-old stands on upland boreal sites (48). The best response to fertilization apparently occurs in stands of low vigor (33,53). For example, fertilization (with nitrogen and phosphorus combined) may convert some marginally nonproductive muskeg stands of black spruce into commercial forest stands (1). Benefits from fertilization will probably be greatest in thinned stands (51).
Drainage may increase the growth and yield of black spruce, but maximum response on peatlands and other wet sites will probably also require fertilization and (in dense stands) thinning. Full-tree harvesting will probably not reduce future productivity, except on sites of marginal fertility (52).
Molecular Biology and Genetics
Hybrids between black spruce and red spruce are common, and introgressive hybridization between the two species has been reported in Nova Scotia, New Brunswick, and Quebec (14,32).
A natural hybrid between black spruce and white spruce found in northern Minnesota has been called the Rosendahl spruce (28). Intermediate forms between black and white spruce have been reported occasionally from other areas (41), but the genetic isolation of these two species must be nearly complete.
Barcode data: Picea mariana
Statistics of barcoding coverage: Picea mariana
Public Records: 16
Specimens with Barcodes: 23
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
This spruce occurs across the North American continent in the boreal zone. Its wide distribution and large population size lead to an assessment of Least Concern.
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
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 . 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
. On brushy sites, aerial spraying herbicides has been used to
release black spruce .
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 . 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 . 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 .
Cultivars, improved and selected materials (and area of origin)
Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
Black spruce grows more slowly than many associated trees and shrubs, and mature trees in spruce-fir stands apparently respond better to release than white spruce and subalpine fir. Many intermediate and suppressed black spruce in swamp stands, however, die after heavy cutting
Clearcutting in strips or patches is generally considered to be the best silvicultural system for managing black spruce. Satisfactory reestablishment after clearcutting requires an adequate seed source and often some kind of site preparation. Uneven-aged or all-aged management is best applied on poor sites where stands are windfirm and have abundant layering.
Eastern dwarf-mistletoe causes serious problems for black spruce in the Lake States and eastern Canada. The spruce budworm and various other insects are damaging. Black spruce is easily killed by both ground and crown fires. Peatland stands have a low risk except during very dry periods
Relevance to Humans and Ecosystems
Other uses and values
Black spruce is still harvested for Christmas trees, but recently the
amount harvested from natural stands has declined . 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 .
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 . In southeastern
Canada, Maine, and Minnesota, black spruce naturally invades
well-drained raised surfaces in abandoned mined peatlands . It can
be established on disturbed sites by direct seeding or by transplanting
Special procedures have been developed for removing black spruce seed
from the semi-serotinous cones . Seeds retain their viability for
several years when stored in sealed containers in a cool, dry
environment . Seeds require no stratification prior to sowing.
They should be sown soon after snowmelt . 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 .
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
. 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 . In northeastern Alberta, overwinter survival of
container-grown and transplanted black spruce seedlings was satisfactory
on amended oil sand tailings .
Black spruce can be readily propagated by root cuttings .
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 . Black spruce also provides good cover for spruce
grouse . 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 .
winter on the Kenai Peninsula of Alaska are presented below :
(percent chemical composition and caloric content)
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 .
Importance to Livestock and Wildlife
occasionally browse saplings, but white-tailed deer eat it only under
starvation conditions . 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 . 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 :
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 . 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].
Wood Products Value
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 .
The spruce grouse depends mainly on black spruce stands for food and cover (26). Birds with relatively high densities in black spruce stands during the summer include the ruby-crowned kinglet, magnolia warbler, Cape May warbler, and ovenbird. Birds such as the pine grosbeak, pine siskin, and crossbills commonly feed on black spruce seed.
The primary use of black spruce wood is for pulp. Lumber is of secondary importance because of the relatively small size of the trees. The trees and wood also are used for fuel, Christmas trees, and other products (beverages, medical salves, aromatic distillations). Black spruce is the provincial tree of Newfoundland.
Picea mariana (black spruce) is a species of spruce native to northern North America, from Newfoundland to Alaska, and south to Pennsylvania, Minnesota and central British Columbia, in the biome known as taiga or boreal forest.
Picea mariana is a slow-growing, small upright evergreen coniferous tree (rarely a shrub), having a straight trunk with little taper, a scruffy habit, and a narrow, pointed crown of short, compact, drooping branches with upturned tips. Through much of its range it averages 5–15 m tall with a trunk 15–50 cm diameter at maturity, though occasional specimens can reach 30 m tall and 60 cm diameter. The bark is thin, scaly, and grayish brown. The leaves are needle-like, 6–15 mm long, stiff, four-sided, dark bluish green on the upper sides, paler glaucous green below. The cones are the smallest of all of the spruces, 1.5–4 cm long and 1–2 cm broad, spindle-shaped to nearly round, dark purple ripening red-brown, produced in dense clusters in the upper crown, opening at maturity but persisting for several years.
It differs from P. glauca in having a dense cover of small hairs on the bark of young branch tips, an often darker reddish-brown bark, shorter needles, smaller and rounder cones, and a preference for wetter lowland areas. Numerous differences in details of its needle and pollen morphology also exist but require careful microscopic examination to detect. From true firs, such as Abies balsamea (Balsam Fir), it differs in having pendulous cones, persistent woody leaf-bases, and four-angled needles, arranged all round the shoots.
Due to the large difference between heartwood and sapwood moisture content, it is easy to distinguish these two wood characteristics in ultrasound images, which are widely used as a nondestructive technique to assess the internal condition of the tree and avoid useless log breakdown.
Older taxonomic synonyms include Abies mariana, Picea brevifolia, Picea nigra.
Growth varies with site quality. In swamp and muskeg it shows progressively slower growth rates from the edges toward the centre. The roots are shallow and wide spreading, resulting in susceptibility to windthrow. In the northern part of its range, ice pruned asymmetric black spruce are often seen with diminished foliage on the windward side. Tilted trees colloquially called "drunken trees" are associated with thawing of permafrost.
In the southern portion of its range it is found primarily on wet organic soils, but farther north its abundance on uplands increases. In the Great Lakes States it is most abundant in peat bogs and swamps, also 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.
Most stands are even-aged due to frequent fire intervals in black spruce forests. It commonly grows in pure stands on organic soils and in mixed stands on mineral soils. It is tolerant of nutrient-poor soils, and is commonly found on poorly drained acidic peatlands. It is considered a climax species over most of its range; however, some ecologists question whether black spruce forests truly attain climax because fires usually occur at 50 to 150 year intervals, while "stable" conditions may not be attained for several hundred years.
The frequent fire return interval, a natural fire ecology, perpetuates numerous successional communities. Throughout boreal North America, Betula papyrifera (Paper Birch) and Populus tremuloides (Aspen|Quaking Aspen) are successional hardwoods that frequently invade burns in black spruce. Black spruce typically seeds in promptly after fire, and with the continued absence of fire, will eventually dominate the hardwoods.
It is a pioneer that invades the sedge mat in filled-lake bogs, though often preceded slightly by Larix laricina (Tamarack), with which it may in time form a stable forest cover 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 Thuja occidentalis (Eastern Arborvitae) will eventually replace black spruce and tamarack.
The larvae of the spruce budworm moth cause defoliation which will lead to death if it occurs several years in a row, though black spruce is less susceptible than white spruce or balsam fir. Trees most at risk are those growing with balsam fir and white spruce.
Uses and symbolism
The timber is of low value due to the small size of the trees, but it is an important source of pulpwood and the primary source of it in Canada. Fast-food chopsticks are often made from black spruce.
|Wikimedia Commons has media related to:|
- Farjon, A. (1990). Pinaceae. Drawings and Descriptions of the Genera. Koeltz Scientific Books ISBN 3-87429-298-3.
- Rushforth, K. (1987). Conifers. Helm ISBN 0-7470-2801-X.
- Gymnosperm Database: Picea mariana
- Flora of North America: Picea mariana
- Wei, Q.; Chui, Y. H.; Leblon, B.; Zhang, S. Y. (2009). "Identification of selected internal wood characteristics in computed tomography images of black spruce: A comparison study". Journal of Wood Science 55 (3): 175. doi:10.1007/s10086-008-1013-1.
- C. Michael Hogan, Black Spruce: Picea mariana, GlobalTwitcher.com, ed. Nicklas Stromberg, November, 2008
- Kokelj, S.V.; Burn, C.R. (2003). "'Drunken forest' and near-surface ground ice in Mackenzie Delta, Northwest Territories, Canada". In Marcia Phillips, Sarah Springman, Lukas Arenson. Proceedings of the 8th Int'l Conf. on Permafrost. Rotterdam: A.A. Balkema. ISBN 9058095827. Retrieved 2 April 2013.
- "Picea mariana 'Nana' AGM". Royal Horticultural Society. Retrieved 14 February 2013.
- Powers, R.F.; Adams, M.B.; Joslin, J.D.; Fisk, J.N. (2005). "Non-Boreal Coniferous Forests of North America". In Andersson, F. Coniferous Forests (1st ed.). Amsterdam [u.a].: Elsevier. p. 271. ISBN 9780444816276.
Because Picea mariana is a small tree, it has limited commercial value. Frequently it is harvested with P . glauca and used for pulp.
Black spruce ( Picea mariana ) is the provincial tree of Newfoundland.
Names and 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. .
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 . Although rare, natural hybrids between black and white
spruce (P. glauca) have been found in Minnesota and other areas .