American Larch

Disjunct Alaskan populations of Larix laricina , originally described as Larix alaskensis on the basis of narrower cone scales and bracts, are indistinguishable from other populations of the species.

The wood of tamarack is used for railway ties, pilings, and posts; it formerly was used for boat construction. Slow-growing trees develop wood with high resin content, making it decay resistant but limiting its value for pulpwood. The bark contains a tannin, which has been used for tanning leather. Although tamarack is the most rapidly growing boreal conifer under favorable conditions, it is of little commercial interest because of insect and disease problems and its poor pulping properties. Plants of this species are often stunted in the far north and on mountain slopes.

Trees to 20m; trunk to 0.6m diam.; crown narrow, branches sparse. Bark of young trees gray, smooth, becoming reddish brown and scaly, inner layer red-purple. Branches horizontal or slightly ascending; twigs orange-brown, glabrous. Buds dark red, subtended by ring of hairlike bracts, glabrous. Leaves of short shoots 1--2cm × 0.5--0.8mm, 0.3--0.5mm thick, keeled abaxially, rounded adaxially, pale blue-green; resin canals 10--20µm from margins. Seed cones 1--2 × 0.5--1cm, usually on curved stalks 2--5 × 2--2.5mm, sometimes sessile on long shoots; scales 10--30, margins entire, brown-strigose to -tomentose at base; bracts mucronate or tipped by awn to 1mm, hidden by mature scales, at first dark red to violet, later turning yellow-brown. Pollen 53--65µm diam. Seeds with bodies 2--3mm, wings 4--6mm. 2 n =24.

Boreal forests in wet, poorly drained sphagnum bogs and muskegs, also on moist upland mineral soils; 0--1200m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Conn., Ill., Ind., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., Ohio, Pa., R.I., Vt., W.Va., Wis.

Pinus laricina DuRoi, Diss. Observ. Bot., 49. 1771; Larix alaskensis W.Wight; L. laricina var. alaskensis (W.Wight) Raup

tamarack
Eastern larch
Alaskan larch
American larch
tamarack larch
hackmatack

More info for the term: cover

Tamarack is probably of limited value as cover for mammals and birds
because it sheds its needles in the winter and often occurs in rather
open stands. In northern Minnesota, ospreys prefer to nest in dead
tamarack trees. Bald eagles occasionally nest in tamarack [35].

More info for the term: tree

Tamarack is a native, deciduous, coniferous, small- to medium-sized
upright tree. It has a straight bole with a narrow pyramidal crown.
Tamarack is a good self-pruner and by 25 to 30 years of age, trees are
generally clear of branches for one-half to two-thirds of their bole
[26]. Trees generally reach 50 to 75 feet (15-23 m) in height and 14 to
20 inches (46-51 cm) d.b.h. but are occasionally larger. In Alaska,
trees are often stunted, reaching heights of only 10 feet (3 m) and
diameters of 3 inches (8 cm), but on good sites mature trees are
generally 30 to 60 feet (9-18 m) tall and 4 to 10 inches (10-25 cm)
d.b.h. [26,49]. The maximum age for tamarack is about 180 years,
although older trees have been found [26].

Tamarack has 1-inch-long (2.5 cm) needles that occur in clusters of 10
to 20 on dwarf twigs [22] and turn yellow in the fall before they are
shed. Erect mature cones are about 0.5 to 0.75 inch (1.3-1.9 cm) long
[26]. Tamarack bark is smooth when young but becomes rough and scaley
on older trees. The bark is thin, only about 0.25 to 0.5 inch (0.6-1.2
cm) thick on mature trees [28]. The root system is typically shallow
and wide spreading. Rooting depth rarely exceeds 1.5 feet (46 cm), but
the roots commonly spread over areas greater in radius than the tree
height [7]. On wet and very wet peatlands in Alberta, roots are
generally restricted to the upper 8 inches (20 cm) of soil on hummocky
positions [31].

Tamarack is distributed across most of northern North America. It
occurs from Newfoundland and Labrador northwest across northern Canada
to the northern Yukon Territory, south to northeastern British Columbia
and central Alberta, southeast to southern Minnesota, Wisconsin, and
northeastern Illinois, and east to New England [32]. A major disjunct
population occurs in the interior of Alaska between the Brooks Range to
the north and Alaska Range to the south [26]. It also occurs locally in
the mountains of West Virginia and western Maryland.

More info for the terms: fire regime, seed

Tamarack trees are easily killed by fire. The species relies on seed
from surviving trees to revegetate burned areas. Generally found in
boggy and swampy habitats, pockets of tamarack trees often escape
burning due to local topography or extremely wet conditions. These
trees provide seeds for postfire recovery. Because seed is dispersed
over short distances, tamarack is not well adapted to rapid reseeding of
large burns.

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the term: shrubs

Tamarack establishes readily on sites where logging slash is burned but
poorly on sites where slash is untreated. On peatlands in Minnesota,
tamarack seedlings were abundant 6 years following broadcast burning of
black spruce-tamarack slash in clearcuts [24]. However, pure tamarack
slash is difficult to broadcast burn. Therefore, when cutting pure
tamarack stands, piling and burning slash is the option that best favors
tamarack reproduction [25].

In Wisconsin, prescribed burning has been conducted in conifer swamps
and muskegs to improve wildlife habitat. Prescribed burning killed
tamarack and other conifers in swamps, and improved feeding and nesting
habitat for game birds by converting these areas to swamps dominated by
sedges (Carex spp.) and ericaceous shrubs [50].

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More info for the term: phanerophyte

Phanerophyte

More info for the terms: bog, minerotrophic, organic soils, peat, peatland, permafrost, shrub, shrubs, swamp, tree

Tamarack is most commonly found on cold, wet to moist, poorly drained
sites such as swamps, bogs, and muskegs [22,26,44]. It is also found
along streams, lakes, swamp borders, and occasionally on upland sites.
It becomes more common on drier sites in the northern portion of its
range where it is found on ridges and benches and other upland locations
[26]. In British Columbia, it grows as an upland tree on cool, moist
north slopes as well as on wet organic sites [26]. In interior Alaska,
tamarack is generally restricted to wet and cold sites underlain by
shallow permafrost but occasionally grows in warmer, well-drained
floodplains and upland forests dominated by white spruce (Picea glauca)
[4].

Soils: Tamarack can tolerate a wide range of soil conditions but most
commonly grows on wet to moist organic soils, such as sphagnum or woody
peat, and is especially common on nutrient-poor, acid peatlands [9,26].
In Minnesota, tamarack occurs on a wide variety of peatland types, from
rich swamps to raised bogs, and is an indicator of weakly minerotrophic
sites (pH 4.3-5.8, Ca 3-10 ppm, Ca + Mg 5-13 ppm) [21]. In
Saskatchewan, tamarack grows on peatland sites with a wide range of
fertility and moisture regimes; it is most common on those with a pH
between 6.0 and 6.9 [23]. Although most commonly occurring on
peatlands, tamarack actually grows best on well-drained loamy soils
along streams, lakes, and seeps, and on mineral soils with a shallow
surface layer of organic matter [26]. However, tamarack is uncommon on
these sites in the southern portion of its range because it is easily
outcompeted by other trees. It is more common on mineral soil in the
north.

Stand characteristics and associated trees: Because the species is
intolerant of shade, tamarack stands are usually even-aged [13]. They
occur on wetter sites than black spruce stands. Across tamarack's range
black spruce is its most common associate. These two species often form
mixed stands on peatlands. Throughout much of boreal Canada, other
associates include balsam fir (Abies balsamea), white spruce, paper
birch (Betula papyrifera), and quaking aspen (Populus tremuloides)
[22,26]. In the Lake States and New England, common associates include
northern white-cedar (Thuja occidentalis), balsam fir, eastern white
pine (Pinus strobus), red pine (P. resinosa), quaking aspen, black ash
(Fraxinus nigra), white spruce, and red maple (Acer rubrum) [7,44]. In
Alaska, tamarack is usually found with black spruce and paper birch but
almost never with aspen [26].

Understory: Tamarack stands tend to cast light shade and have a dense
undergrowth of shrubs. Tall shrubs associated with tamarack include bog
birch (Betula glandulosa), swamp birch (B. pumila), speckled alder
(Alnus incana ssp. rugosa), willows (Salix spp.), and red-osier dogwood
(Cornus stolonifera). Low shrub associates include Labrador-tea (Ledum
groenlandicum), bog-rosemary (Andromeda glaucophylla), leatherleaf
(Chamaedaphne calyculata), and blueberries and huckleberries (Vaccinium
spp.). The ground is usually covered with sphagnum and other mosses
[26].

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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
33 Red spruce - balsam fir
37 Northern white cedar
38 Tamarack
39 Black ash - American elm - red maple
107 White spruce
201 White spruce
203 Balsam poplar
204 Black spruce
253 Black spruce - white spruce
254 Black spruce - paper birch

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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
FRES17 Elm - ash - cottonwood

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: bog, forest

K093 Great Lakes spruce - fir forest
K094 Conifer bog
K095 Great Lakes pine forest
K096 Northeastern spruce - fir forest

More info for the terms: muskeg, seed, surface fire

Tamarack is easily killed by fire because it has thin bark and shallow
roots. On peatlands it is usually killed by all but very light surface
fires [26]. Tamarack seeds have no endosperm to protect them from high
temperatures; therefore, seeds on the ground are usually destroyed by
fire. Cones are not necessarily destroyed by summer fires, but immature
seeds will not ripen on fire-killed trees [52]. If summer fires kill
tamarack trees over extensive areas, no seed will be available to
revegetate the burned area.

Following a fire in a northern Wisconsin muskeg all tamaracks died
(trees were 1 to 5 inches [2.5-12.5 cm] d.b.h.) [50]. In interior
Alaska, all tamarack trees died following a low-intensity surface fire
that burned only 2 to 4 inches (5-10 cm) into the organic mat [20].
These trees were 49 to 79 years old and 1.5 to 3 inches (3-6 cm) in
diameter.

More info for the term: seed

Browse: Tamarack is an important dietary component of very few wildlife
species. It is browsed by some animals but generally to a limited
extent. Snowshoe hares feed on twigs and bark, and porcupines feed on
the inner bark [16]. Moose and white-tailed deer generally avoid
tamarack [6,16]. Spruce, blue, and sharp-tailed grouse readily consume
the needles and buds [34,51]. A study in north-central Canada found
that caribou consume small amounts of tamarack; needles were frequently
found in caribou rumens, but always in small amounts [36].

Seed: Red squirrels cut and cache tamarack cones. The pine siskin,
crossbills, and probably other seed eating birds eat tamarack seeds
[19]. Mice, voles, and shrews consume large numbers of tamarack seeds
off the ground [11].

More info for the terms: bog, forest, permafrost, tree

In northern Minnesota and throughout much of Canada, tamarack forms
extensive pure stands. Throughout the rest of its range in the United
States it forms isolated pure stands or is a minor component of other
forest types [26]. In the northeastern United States, tamarack is
characteristically found in open and forested bogs, but it seldom
dominates in forested bog communities [9]. Throughout its range, black
spruce (Picea mariana) is usually associated with tamarack. In Alaska,
black spruce and tamarack may codominate wet, lowland sites with shallow
permafrost [48].

Tamarack is sometimes a dominant tree in seral lowland communities. It
has been listed as a community type (cts) dominant in the following
classifications:

Area Classification Authority

AK general veg. cts Viereck & Dyrness 1980

AB general veg. cts Moss 1955
PQ: ST. Lawrence general veg. pas, cts Dansereau 1959
Valley

More info for the term: tree

Tree

Silviculture: Tamarack seeds germinate and establish best in the open.
Seedlings require nearly full sunlight to survive and grow well.
Consequently, even-age silviculture is best for perpetuating larch on a
site [2,27].

Insects and diseases: Larch sawfly is the most destructive pest of
tamarck. Epidemics occur periodically in tamarack stands across the
northern United States and Canada. This insect is capable of
defoliating stands over large areas and killing many trees. Trees die
after 6 to 9 years of heavy defoliation [26]. Outbreaks of the larch
casebearer have also caused extensive mortality in some areas. The
spruce budworm, larch bud moth, spruce spider mite, larch shoot moth,
and several bark beetles also infest tamarack but seldom cause serious
injury [26]. Tamarack is generally resistant to rusts and other
diseases [26].

Flooding: Tamarack is susceptible to damage from flooding and
disruptions in 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 [26].

AK CT IL IN ME MD MA MI MN NH
NJ NY OH PA VT WV WI AB BC LB
MB NB NF NS ON PE PQ SK YT

In Alaska, young tamarack stems are used for dogsled runners, boat ribs,
and fishtraps. In northern Alberta, duck and goose decoys are made from
tamarack branches. Indians used the roots for cordage, the wood for
arrow shafts, and the bark for medicine. Early Americans used the soft
needles for stuffing pillows and mattresses and used the roots of large
trees for ship building [26,28].

The palatability of tamarack for white-tailed deer and moose is low.
Tamarack is more palatable to snowshoe hare than white spruce (Picea
glauca) is [4].

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More info for the term: seed

Minnesota: Buds begin to swell from early to late April. Needles begin
to emerge from about mid-April to mid-May. Needles are shed from
mid-September to mid-October. Flowering occurs from late April to early
May. Seedfall begins in early September and is nearly complete by late
October [11,16,26].

Wisconsin: Tamarack begins to leaf out in the early spring before the
ground has thawed. It takes 4 to 6 weeks for the needles to develop
fully. The needles turn yellow in late September or early October and
are shed shortly thereafter [7].

Upper Peninsula of Michigan: Needles begin to emerge in mid-April to
mid-May. Needles begin to turn yellow in early September and are shed
from mid-September to mid-October. Flowering occurs in early May, and
cones are ripe by late August [16,26].

Alaska: Seed dispersal begins in early September and is mostly
completed by late October [4].

New York: Height growth begins in late May and ends by late August [5].

More info for the terms: seed, swamp, tree

Following fire, tamarack reestablishes via wind-dispersed seeds from
surviving trees in protected pockets or adjacent unburned areas. Burned
organic surfaces favor seedling establishment. Within a few years
tamarack reproduction is often localized and centered around areas of
surviving trees [37].

In northeastern British Columbia, tamarack seeded onto burned areas over
several years. Most seedlings established within 10 years after fire,
but additional establishment continued until 20 years after fire [41].
Postfire tamarack seedlings grow rapidly. Twenty-one years after a fire
in a tamarack-black spruce swamp in northeastern British Columbia,
tamarack seedlings were more than 2 times taller than black spruce
seedlings. Tamarack seedlings that established soon after the fire
averaged 7.9 feet (2.4 m) tall, while black spruce seedlings that
established at the same time were only 3.6 feet (1.1 m) tall [40].

Tamarack seedlings were abundant 6 years after clearcutting and
broadcast burning in mixed black spruce-tamarack stands in northern
Minnesota. Tamarack seedlings made up 43 percent of tree seedlings 66
feet (20 m) downwind from the uncut border, even though tamarack made up
only 27 percent of the seed trees (55 per acre [136/ha]). On this site,
4,200 tamarack seedlings averaging 21 inches (53 cm) in height were
established per acre (10,400/ha). On another cut where there were only
12 tamarack seed trees per acre (30/ha) at the uncut border, 4,400
seedlings averaging 39 inches in height (1 m) were established per acre
(10,900/ha) [24].

More info for the term: seed

off-site colonizer; seed carried by wind; postfire years 1 and 2

More info for the terms: cone, layering, litter, seed, tree, tussock

Cone and seed production: Cone production begins at about 15 years of
age for open-grown trees and 35 to 40 years of age for trees in
well-stocked stands [11]. Large quantities of seed are usually not
produced until trees are at least 40 years old. Fifty- to 150-year-old
open-grown trees produce the best cone crops, with individual trees
sometimes producing as many as 20,000 cones in a good year [11]. Good
seed crops are produced every 3 to 6 years, with some seed produced in
intervening years. Tamarack seeds are about 0.12 inch (3 mm) long and
have a wing about 0.25 inch (6 mm) long [26].

Dispersal: Seeds are dispersed in the fall over a relatively short time
period. In a Minnesota study, dispersal began about September 1, and by
October 31 about 98 percent of seed had fallen [11]. The remaining seed
fell throughout the winter. In interior Alaska, 95 percent of tamarack
seeds are shed by November [4]. Tamarack seeds are primarily wind
dispersed, but red squirrels disperse some seed. Most wind-dispersed
seeds fall within a distance of two tree heights, but a small percentage
travels greater distances [4,11].

Seed destruction and predation: In Minnesota, small mammals, presumably
mice, voles, and shrews, consume large quantities of tamarack seed off
the ground and can destroy up to one-half of a tamarack seed crop [11].
Also, seeds on the ground are susceptible to infections from bacteria
and fungi. Consequently, only about 4 or 5 percent of tamarack seed
that reaches the ground germinates [26]. In tamarack stands in New
Brunswick, insects destroyed between 25 and 88 percent of seed produced.
Larvae of the spruce budworm and the cone maggot were responsible for
greatest loss [53].

Viability: Tamarack seed remains viable for only about 1 year after
dispersal [11]. Typically a large percentage of tamarack seed is
unfilled. In Minnesota about one-third, and in northern Ontario about
one-half of seed had undeveloped embryo and endosperm [11,15]. At the
northern portion of the species range in the Northwest Territories,
tamarack produced a limited amount of seed, but none was viable [12].

Germination and establishment: Germinative capacity ranges from about
30 to 60 percent [11]. Neither light nor pH appear to influence
germination appreciably [11,15]. Tamarack seeds require a moist but
unsaturated substrate for germination. The best seedbed is warm, moist
mineral or organic soil free from competing vegetation [26].
Slow-growing sphagnum mosses also provide a good seedbed, as they have a
tendency to remain moist. In open swampy habitats, tamarack seedlings
are often found on sphagnum mosses [1,7]. Feather mosses are usually
poor seedbeds because they tend to dry out, but if they remain moist,
they can provide a favorable seedbed [4]. On poorly drained river
terraces in interior Alaska, tamarack seedlings are more abundant on
sphagnum and feather mosses than on sedge tussock tops, troughs between
the tussocks, or litter-covered sites; on well-drained river terraces,
seedlings are primarily restricted to mineral soil [4]. Tamarack
seedlings are intolerant of shade and flooding. Seedlings may survive a
few years in shade, but most will die unless released. Partial water
submersion for 1 to 3 weeks kills 1st-year seedlings [11]. In full
sunlight seedlings grow relatively rapidly, reaching heights of 7 to 9
inches (18-23 cm) after one growing season, and 18 to 25 inches (46-51
cm) tall after three [26]. Roots of seedlings growing in nearly full
sunlight may reach depths of 2.5 to 3.5 inches (5-11 cm) after one
growing season, while over the same time period roots of seedlings
growing in shade reach depths of only about 1 inch (2.5 cm) [11].

Vegetative reproduction: Layering is a dominant mode of reproduction at
the northern limit of the species' range. In the southern part of its
range, layering is uncommon but does occur when lower branches become
covered with litter or fast-growing mosses [26]. Curtis [7] reported
that tamarack has the unusual ability to produce root sprouts up to 30
feet (9 m) away from a mother tree.

More info on this topic.

More info for the terms: peat, shrub, swamp, tree

Tamarack is a pioneer or early seral species. It is often the first
tree to invade open bogs and burned peatlands [26]. In open bogs and
swamps, tamarack is the first tree to pioneer the sphagnum moss mat
floating over water [7]. This invasion toward the center or wettest
portion of a swamp is common [1,18]. It may invade bogs during sedge
mat, sphagnum moss, or ericaceous shrub stages. Tamarack is extremely
intolerant of shade, however, and eventually, as the peat becomes
consolidated and firm, other conifers replace it. It is replaced by
black spruce on poorly drained acid peatlands. In nutrient-rich swamps
it is replaced first by black spruce, and later by northern white-cedar,
balsam fir, and eventually swamp hardwoods [16].

Larix laricina var. alaskensis (W.F. Wright) Raup

More info for the terms: cone, natural

The currently accepted scientific name of tamarack is Larix laricina (Du
Roi) K. Koch [32]. The genus Larix consists of 10 species of deciduous,
coniferous trees found in cool, temperate regions of the northern
hemisphere. Three species of Larix, including tamarack, are native to
North America.

Tamarack is a widely distributed species that exhibits considerable
genetic variation. At one time, plants from Alaska were considered as
either a distinct species or as a variety of tamarack. Recent research
shows that although Alaskan plants exhibit some variation in cone and
needle characteristics, the variation is insufficient to warrant
recognition as a separate species or variety [39]. Across tamarack's
range the pattern of variation is gradual, and no varieties or ecotypes
are currently recognized [26].

Natural hybridization between tamarack and other larches has not been
documented. Tamarack has been artificially crossed with Japanese larch
(L. leptolepis) and European larch (L. decidua) [26].

More info for the term: seed

Tamarack may be useful for revegetating disturbed peatlands. In
southeastern Canada, Maine, and Minnesota, tamarack naturally invades
well-drained, raised surfaces in abandoned mined peatlands [14].
Tamarack should not be planted with fast-growing trees because of its
low tolerance for shade.

On amended sand tailings in northern Alberta, tamarack survival varied
from 0 to 60 percent [51]. When planted on coal mine spoils it
performed quite well. It grew faster than black spruce and added needed
organic matter to the spoil [51].

Tamarack can be established on disturbed sites by direct seeding or by
transplanting seedlings. Tamarack seed does not exhibit dormancy and
can be planted in the spring or fall. Seed should be sown at a depth of
about 0.25 inch (0.6 cm). Seed remains viable for 4 years when kept in
sealed containers at 18 to 22 degrees F (-8 to -6 C) and a seed moisture
content of 2 to 5 percent [45]. Tamarack is easily propagated from
cuttings taken from young trees [26,54].

Tamarack is not a major commercial timber species. In the United
States, it is primarily used for pulpwood. Because the wood is heavy,
durable, and decay-resistant, it is also used for posts, poles, mine
timbers, and railroad ties. It is used less commonly for rough lumber,
fuelwood, boxes, crates, and pails [28].

Tamarack forms extensive pure stands in the boreal region of Canada and in northern Minnesota. In the rest of its United States range and in the Maritime Provinces tamarack is found locally in both pure and mixed stands. It is a major component in the forest cover types Tamarack (Society of American Foresters Type 38) and Black Spruce-Tamarack (Type 13) and is a minor component in the following types (11):

1 Jack Pine 5 Balsam Fir 12 Black Spruce 33 Red Spruce-Balsam Fir 37 Northern White Cedar 39 Black Ash-American Elm-Red Maple 107 White Spruce 203 Balsam Poplar 204 Black Spruce 253 Black Spruce-White Spruce 254 Black Spruce-Paper Birch Black spruce (Picea mariana) is usually tamarack's main associate in mixed stands on all sites. The other most common associates include balsam fir (Abies balsamea), white spruce (Picea glauca), and quaking aspen (Populus tremuloides) in the boreal region, and northern white-cedar (Thuja occidentalis), balsam fir, black ash (Fraxinus nigra), and red maple (Acer rubrum) on the better organic-soil (swamp) sites in the northern forest region (11). In Alaska, quaking aspen and tamarack are almost never found together (50). Additional common associates are American elm (Ulmus americana), balsam poplar (Populus balsamifera), jack pine (Pinus banksiana), paper birch (Betula papyrifera), Kenai birch (B. papyrifera var. kenaica), and yellow birch (B. alleghaniensis).

Tamarack stands cast light shade and so usually have a dense undergrowth of shrubs and herbs. Because the tree has an extensive range, a great variety of shrubs is associated with it. Dominant tall shrubs include dwarf (resin) and low (swamp) birch (Betula glandulosa and B. pumila), willows (Salix spp.), speckled alder (Alnus rugosa), and red-osier dogwood (Cornus stolonifera); low shrubs include Labrador-tea (Ledum groenlandicum), bog-rosemary (Andromeda glaucophylla), leatherleaf (Chamaedaphne calyculata), and small cranberry (Vaccinium oxycoccos) (see 12 for a more complete list). Characteristically the herbaceous cover includes sedges (Carex spp.), cottongrass (Eriophorum spp.), false Solomonseal (Smilacina trifolia), marsh cinquefoil (Potentilla palustris), marsh-marigold (Caltha palustris), and bogbean (Menyanthes trifoliata). Ground cover is usually composed of sphagnum moss (Sphagnum spp.) and other mosses (11).

Because of its wide distribution, tamarack grows under extremely varied climatic conditions. Average January temperatures range from -30° to -1° C (-22° to 30° F) and those of July from 13° to 24° C (55° to 75° F). The lowest recorded temperatures range from -29° to -62° C (-20° to -79° F); the highest, from 29° to 43° C (85° to 110° F).

Annual precipitation within the range of tamarack is also extremely variable. It ranges from 180 mm (7 in) at Fort Yukon, AK, to 1400 mm (55 in) in eastern Canada. Of this, 75 to 355 mm (3 to 14 in) is in June, July, and August. Snowfall has a similarly wide variation, from about 100 cm (40 in) in the District of Mackenzie in northwestern Canada to 510 cm (200 in) near the Atlantic coast in Labrador and Quebec.

The average frost-free period for tamarack ranges from probably less than 75 days over much of its range to 120 days in interior Alaska and 180 days along its southern limits. The generally shorter growing season in the northern latitudes is counterbalanced by longer periods of daylight (12).

Because its bark is thin, tamarack is highly susceptible to fire damage, except perhaps in older, upland stands; and because its roots are shallow, it is usually killed on peatlands by all but very light burns. However, the habitat of tamarack-especially south of the boreal forest-is normally wet enough to protect the tree from fire (6). In the boreal forest the tamarack type apparently has a high surface-fire hazard in spring but a low crown-fire hazard in pure stands (35).

Abnormally high water levels often kill tamarack stands, and those that survive under such conditions usually grow very slowly. Other effects of high water include dieback and the development of adventitious roots and shoots (8). Wetland road crossings and beaver damming are the primary causes of flooding. Road-caused flooding has killed tamarack or reduced its growth on thousands of hectares in northern Minnesota (40); natural gas and petroleum pipelines will probably have similar effects unless cross drainage is provided (3).

Strong winds can uproot large tamarack trees growing in swamps or other wet sites where rooting is shallow. Compared with black spruce, however, tamarack seems to be fairly windfirm.

The larch sawfly is the most destructive insect enemy of tamarack. Epidemics occur periodically across Canada and the northern United States and have caused tremendous losses of merchantable tamarack throughout most of the tree's range. Indications are that radial increment declines markedly after 4 to 6 years of outbreak and trees die after 6 to 9 years of moderate to heavy defoliation (9). In southeastern Manitoba and northern Minnesota, however, imported parasites of the sawfly (especially Olesicampe benefactor) have become established and should reduce the frequency and duration of future outbreaks (42).

The larch casebearer (Coleophora laricella) is also a serious defoliator of tamarack. A native of Europe, it is now widely distributed in eastern North America westward to southeastern Manitoba and the Lake States. The larch casebearer attacks tamarack of all ages, and several severe outbreaks have caused extensive mortality in some areas (49). Outbreak severity has lessened in recent years, however, probably because imported parasites of the casebearer have also become widely established (34).

Only a few other insects and related organisms (such as mites) that feed on tamarack are known to sometimes cause serious injury. During an outbreak the spruce budworm (Choristoneura fumiferana) can severely damage tamarack where it grows along with balsam fir and white spruce-the preferred hosts. The larch bud moth (Zeiraphera improbana) has had occasional short epidemics, and the spruce spider mite (Oligonychus ununguis) is occasionally found in large numbers on tamarack. The larch shoot moth (Argyresthia laricella) is widely distributed but serious injury is unusual. One of the most common bark beetles attacking tamarack is the eastern larch beetle (Dendroctonus simplex), but it feeds mainly on weakened, dying, or dead trees. Warren's collar weevil (Hylobius warreni), common in Canada, has killed pole-sized tamarack in Michigan's Upper Peninsula (34,49).

Several insects feed on tamarack cones and seeds, but little is known about their importance. Those that feed inside cones include the spruce coneworm (Dioryctria reniculelloides) and a seed chalcid (Megastigmus laricis). Two defoliators that sometimes feed on tender young cones during epidemics are the spruce budworm and the larch bud moth (16,34). Cones were still being produced after 3 to 4 years' defoliation by the larch sawfly in Canada and after 8 years of attack in northern Minnesota (12).

Tamarack is host to many pathogens, but none causes disease serious enough to have an economic impact on its culture. The only common foliage diseases are rusts, such as the leaf rust of poplar (Populus spp.) and larch (Larix spp.) in eastern and central North America. However, this rust, caused by the fungus Melampsora medusae, and other rusts do little damage to tamarack (19,37). The needle-cast fungus Hypodermella laricis has attacked tamarack in Ontario and has the potential for local damage.

Tamarack is essentially free of stem diseases. Eastern dwarf mistletoe (Arceuthobium pusillum) is occasionally found on the tree (29), but its witches' brooms are small on tamarack and occur only where the tree is growing in mixture with infected black spruce (19).

The root- and butt-rot fungi reported on tamarack include Armillaria (or shoestring) root rot (Armillaria mellea), Scytinostroma galactinum, red-brown butt rot (Phaeolus schweinitzii), and the false velvet top fungus (Inonotus tomentosus) (19,47). They are not aggressive killers on tamarack; however, flood-damaged trees are particularly susceptible to attack by fungi such as Armillaria root rot (8), and pole-sized trees have been killed by the false velvet top fungus.

The principal heart-rot fungi of tamarack are brown trunk rot (Fomitopsis officinalis) and red ring rot (Phellinus pini). Climacocystis borealis causes a white mottled rot of tamarack in Canada (19).

Snowshoe hares kill many tamarack seedlings in some areas of the Lake States, Alberta, and Alaska (50). White-tailed deer and moose apparently browse seedlings or saplings to a lesser extent. Porcupines commonly feed on the inner bark and deform the stem or kill the tree. Many tamarack stands have been damaged by this pest in the Lake States, Maine, and eastern Canada (27). It can be especially damaging in plantations (48). Red squirrels often cut cone-bearing branchlets, and birds such as the red crossbill occasionally eat the seeds (12).

Tamarack is monoecious; male and female flowers are small, solitary, and appear with the needles. Male flowers are yellow, globose, and are borne mainly on 1- or 2-year-old branchlets. Female flowers are reddish, subglobose, and are borne most commonly on 2- to 4-year-old branchlets, but also on branchlets 5 to 10 or more years old, or on 1-year-old twigs of young trees. Cones usually are produced on young growth of vigorous trees. On open-grown trees, cones are borne on all parts of the crown. Ripe cones are brown, oblong-ovoid, and 13 to 19 mm (0.50 to 0.75 in) long.

General dates for tamarack flowering in Ontario and the Lake States are April to May (36), especially from late April to early May (1,12). In interior Alaska tamarack generally flowers from mid- to late May (50). General dates for cone ripening in Ontario and the Lake States are August to September.

Population Differences and Races Tamarack shows much genetic variation. Growth responses to photoperiod were found to differ between northern seed sources and a southern source (45). Differences in germination patterns due to photoperiod and length of cold stratification have been shown between seed from interior Alaska and seed from southern sources (4).

Growth responses would seem to indicate that photoperiodic ecotypes exist in tamarack (45). The species is considered to have a clinal pattern of variation, however, and no races or ecotypes are presently recognized. For example, tamarack's gene pool in Wisconsin is highly variable but unsegmented, with a clinal pattern of variation evident among the State's major geographic subdivisions (31).

Tamarack seed sources differed significantly in survival, height, and d.b.h. 10 years after planting in north-central Wisconsin. The following sources grew best on a high-yield site and are recommended for north-central Wisconsin (32): Somerset County, ME; Eau Claire, La Crosse, and Oneida Counties, WI; and Annapolis County, NS.

Tamarack in Alaska was once named as a separate species (Larix alaskensis) and later reduced to a variety (L. laricina var. alaskensis), but the Alaska variety is no longer accepted (46).

Hybrids Little information is available on intraspecific hybridization in tamarack, but careful selection and breeding may result in substantial genetic improvement. Similarly, although tamarack has been little used in interspecific hybridization, it has been crossed with two other species of the Section Pauciseriales--Japanese larch (Larix leptolepis) and European larch (L. decidua). Progenies with hybrid vigor are often produced, but seed yield is very low (13). The tamarack-Japanese larch hybrid is especially promising because it combines rapid growth with adaptability to shorter growing seasons (20). Although crosses between tamarack and the remaining species of the Section-Dahurian larch (L. gmelini) and Siberian larch (L. sibirica)- seem feasible (30), apparently none has yet been produced.

Average height of mature trees is 15 to 23 m (50 to 75 ft), but occasional individuals may grow 30 to 35 m (100 to 115 ft) tall. Mature trees are usually 36 to 51 cm (14 to 20 in) in d.b.h., but a few reach 91 to 102 cm (36 to 40 in). Trees 18 to 24 m (60 to 80 ft) tall and 51 to 61 cm (20 to 24 in) in d.b.h. were once common in the Lake States. In interior Alaska mature tamaracks often are only 3 m (10 ft) tall and 8 cm (3 in) in d.b.h. (12); on good sites, however, they sometimes reach heights of 24 to 27 m (80 to 90 ft) and diameters of 30 to 38 cm (12 to 15 in) (50). Maximum age is generally 150 to 180 years, but trees 230 to 240 years old and one 335-year-old individual have been found.

The growth rate of tamarack apparently depends on both the nutrient status and moisture-aeration conditions of the site. In Minnesota, tamarack site index is positively correlated to nutrient supply and foliar nutrient concentrations (especially nitrogen and phosphorus) but negatively correlated to amount of standing water (43). On water-covered stagnant peatlands, the tree grows slowly and may be only 2 m (6 ft) tall in 55 years. In northern Ontario it grows well on 91 cm. (36 in) or more of peat if the zone of continuous saturation is at a depth of 46 cm (18 in) or more (12); drainage of tamarack-speckled alder swamps in the clay belt would probably increase site index (at 100 years) by about 5 m (16 ft) (39).

With abundant light, tamarack is one of the fastest growing conifers on uplands in the boreal (including Alaska) and northern forest regions; on peatlands it outgrows any other native conifer (6,12,50). In Alberta, good-site tamarack averages almost 0.5 m (1.5 ft) in annual height growth for 20 to 30 years, but growth apparently drops sharply when the crowns close, or after the age of 40 to 50 years.

Information on growth of natural tamarack stands is apparently available only from northern Minnesota. Limited data indicate that annual growth of poletimber stands (presumably on peatland sites) is from 1.9 to 2.5 m³/ha (0.3 to 0.4 cord/acre). In 70- to 100-year-old stands, annual periodic growth averaged 3.8 m³/ha (0.6 cord/acre) on well-stocked plots with a basal area of 21 m²/ha (93 ft²/acre) and 1.9 m³/ha (0.3 cord/acre) on poorly stocked plots with 8 m²/ha (35 ft²/acre) (12).

No yield tables are known for tamarack. Characteristics of a few 80- to 130-year-old stands on medium- to poor-peatland sites in northern Minnesota generally ranged as follows: average height, 12.2 to 15.5 m (40 to 51 ft); average d.b.h., 13.0 to 14.7 cm (5.1 to 5.8 in); number of trees, 1,370 to 1,740/ha (555 to 705/acre); and basal area, 19 to 23 m²/ha (83 to 102 ft²/acre) (41).

No doubt because of its potential for rapid juvenile growth, tamarack has been used in several planting tests on different sites in the Lake States (25,32,33) and eastern Canada (15,28). Trees grew slowly on peatland, but on other sites height averaged from 3.2 to 4.4 m (10.5 to 14.4 ft) in 8- to 10-year-old plantations where competing vegetation was initially controlled. Survival was more variable, being very poor on shallow soils over limestone.

Growth rate (particularly diameter) declines after 12 to 15 years if tamarack is planted at close spacings such as 1.5 by 1.5 m (5 by 5 ft), but it should be unimpeded for the first 25 years at wider spacings up to 2.4 by 2.4 m (8 by 8 ft). In a good plantation in eastern Ontario, height at 25 years averaged 14.9 m (49 ft), d.b.h. 17.3 cm (6.8 in), and volume 202 m³/ha (32 cords/acre). Depending on site, final harvests of 189 to 252 m³/ha (30 to 40 cords/acre) are possible at 25 years in well-managed tamarack plantations (27). Intensively cultured plantations can produce two to three times more biomass than conventionally tended stands (51).

In stands tamarack is characteristically a straight, slender tree with a narrow, pyramidal crown that occupies one-third to one-half the bole length. Trees whose tops have died back after heavy defoliation by the larch sawfly (Pristiphora erichsonii) or after prolonged flooding typically produce numerous adventitious shoots. Although these shoots no doubt help tamarack survive defoliation or flooding, they also apparently support high sawfly populations (12).

Tamarack is very intolerant of shade. Although it can tolerate some shade during the first several years (21,50), it must become dominant to survive, and when mixed with other species, it must be in the overstory. On good swamp sites in Michigan, for example, tamarack is a dominant tree in the overstory of some mixed conifer stands, but it is practically never found in the understory (2). The tree is a good self-pruner, and boles of 25- to 30-year-old trees may be clear for one-half or two-thirds their length.

Tamarack is a pioneer tree, especially on open unburned bogs and burned organic soil (11). It is generally the first forest tree to invade filled-lake bogs. In the Lake States tamarack may first appear in the sedge mat, sphagnum. moss, or not until the bog shrub stage; farther north it is the pioneer tree in the bog shrub stage (12). Tamarack is fairly well adapted to reproduce successfully on burns (35), so it is one of the usual pioneers on most sites in the boreal forest immediately after fire. The tree commonly forms stands on abandoned farmland in eastern Ontario (27) and reproduces well on sites in Alaska that were cleared and then abandoned (50).

Because tamarack is very intolerant, it does not become established in its own shade. Consequently, the more tolerant black spruce eventually succeeds tamarack on poor (bog) sites, whereas northern white-cedar, balsam fir, and swamp hardwoods succeed tamarack on good (swamp) sites (12). Recurring sawfly outbreaks throughout the range of tamarack have probably speeded the usual succession to black spruce or other associates (11).

Various tests on planting and natural reproduction indicate that competing vegetation hinders tamarack establishment. A year's delay in planting furrows on a wet lowland resulted in significantly lower first-year survival, apparently because of the rapid resurgence of grass and other herbaceous vegetation (24). On brushy peatland, 7-year survival and height were both much lower where tamarack was planted on unsprayed rather than on herbicide-sprayed areas (33). Six years after broadcast burning and natural seeding on peatland, tamaracks overtopped by surrounding vegetation were only about half as tall as those generally not overtopped (21). Tamarack does not grow well where sugar maple (Acer saccharum) reproduction is present; this seems at least partly due to the maple's root exudate (44).

The intolerance of tamarack dictates the use of even-aged management, with some adaptation of clearcutting or seed-tree cutting generally considered the best silvicultural system, because tamarack seeds apparently germinate better in the open and the seedlings require practically full light to survive and grow well. Tamarack is also usually windfirm enough for the seed-tree system to succeed. Satisfactory reestablishment of tamarack, however, often requires some kind of site preparation, such as slash disposal and herbicide spraying (22).

For successful tamarack plantations, the planting stock's roots and shoots must be well balanced and dormant; probably the best stock is begun in a greenhouse and transplanted for 1 year. Competition must also be controlled, the first 2 years after planting being critical. Because tamarack is very intolerant, the trees should be planted at wide spacings such as 2.4 by 2.4 m (8 by 8 ft) (27).

Tamarack typically has a shallow, spreading root system. On favorable sites roots may spread over an area greater in radius than the tree height but are only 30 to 61 cm (12 to 24 in) deep. Trees on sandy upland have a platelike rooting habit; few roots reach below a 30-cm (12-in) depth and taproots are rare. On wet sites tamarack roots are usually stringy with no branches on the terminal 15 cm (6 in). Peatland tamaracks, in particular, have wide root systems and do not form taproots. As the moss layer deepens, new roots develop on the stem above the original root collar, and growth of old roots nearly ceases. On drier sites roots of larger trees bend sharply from the trunks, forming knees (12).

Isolated trees on peatlands and trees in upland plantations begin to bear viable seed at 12 to 15 years of age or even less. In eastern Ontario viable seed has been collected from vigorous plantations as young as 4 years (27). Seed production in large quantities generally begins at about 40 years, the optimum age being about 75 years. Tamaracks on peatland in Saskatchewan and Manitoba do not bear cones in quantity, however, until they are about 50 years old (12).

Vigorous, open-grown trees 50 to 150 years old produce the best cone crops; a single tree may bear as many as 20,000 cones containing more than 300,000 full seeds in a good year. Seed production in stands is generally confined to dominant and codominant trees. Open-grown mature stands 80 years old may produce 3,700,000 to 6,200,000 full seeds per hectare (1,500,000 to 2,500,000/acre) in a good year, while closed stands the same age may produce 1,200,000 to 3,000,000 seeds per hectare (500,000 to 1,200,000/acre).

Tamarack bears good seed crops at intervals of 3 to 6 years, with some seed produced in intervening years. In Minnesota cones from mature trees averaged 26 seeds, 67 percent of which were full; cones from young trees averaged 39 seeds and 85 percent were full.

General dates for tamarack seed dispersal in Ontario, the Lake States, and interior Alaska are September to spring (36,50). A 1-year study in northeastern Minnesota revealed that 65 percent of the crop fell from September 1 to September 20, 25 percent from September 20 to October 10, and nearly all of the remaining 10 percent before October 31. Empty cones remain on the trees from 2 to 5 years (12).

Tamarack seeds are 3 mm (0.12 in) long and have light chestnut-brown wings 6 mm (0.25 in) long; cleaned seeds average about 550 000 to 710 000/kg (250,000 to 320,000/lb) (18,36). Although the seeds are small, few fall at a distance greater than twice the tree height. However, tamarack can reproduce well as far as 60 m (200 ft) from seed-bearing trees if favorable seedbeds are present (22).

Up to half the tamarack seeds that fall may be destroyed by rodents. As a result of this loss plus that by fungi or bacteria, only 4 to 5 percent of the seed may germinate (12). In nurseries, erratic and often poor germination has been a major difficulty in producing tamarack stock (27); germination can even be poor in a greenhouse (24). Recleaning the seed can substantially reduce the high percentage of empty or improperly developed seed found in many seed lots (18). Experience in Ontario shows that under optimum conditions, seed collected from vigorous stands in a good seed year has 75 to 90 percent germination (27).

Tamarack seed remains viable for 4 years or more when stored in sealed containers at 2 to 5 percent moisture content and -8° to -6° C (18° to 22° F). Internal dormancy apparently ranges from none to mild. Under forest conditions any existing dormancy is broken while the seed lies on the ground during the first winter; thus fall sowing is generally recommended. However, spring-sown seed may germinate well without any cold stratification (18,36).

Germination is epigeal, the cotyledons rising above the ground. It normally begins from late May to mid-June and reaches a peak at surface temperatures of 18° to 21° C (65° to 70° F). In laboratory experiments germination has occurred at temperatures as low as 12° C (54° F) (4) and the rate may increase with temperature up to about 24° C (75° F). Under deep shade germination occurred at 13° C (55° F). Alternating day and night temperatures of 30° and 20° C (86° and 68° F), respectively, are recommended for germination tests (36).

The best seedbed is warm, moist mineral or organic soil with no brush but a light cover of grass or other herbaceous vegetation. Hummocks of slow-growing sphagnum moss often make a good seedbed, but some sphagnum mosses may offer too much competition. In Minnesota germination beneath tamarack stands was best on fine-textured mosses (primarily Mnium, Drepanocladus, and Helodium) (12). Findings from clearcut peatlands in Minnesota show that slash-burned seedbeds favor tamarack reproduction, whereas slash hinders it (22). On uplands, tamarack apparently reproduces well on rock-raked areas after natural seeding.

For best growth tamarack seedlings need abundant light and a constant but suitable water level. In Canadian studies, full light produced the tallest seedlings and heaviest root weights (26). Under drought conditions, leader length and stem diameter were significantly reduced by soil moisture tensions of 15.2 bar (15 atm), but tensions of 1.0 and 6.1 bar (1 and 6 atm) had little effect (14). Seedlings under fully stocked stands usually grow 2 to 3 cm (1 in) the first year and do not survive beyond the sixth year. With little or no cover they may be as tall as 18 to 23 cm (7 to 9 in) the first year and 46 to 64 cm (18 to 25 in) the third year. From then on, growth is generally even more rapid if light is adequate and drainage is good (12).

Buds begin to swell 2 or 3 weeks before opening; in northeastern Minnesota this occurs from early to late April. Needles begin to emerge from about mid-April to mid-May in Minnesota, Michigan's Upper Peninsula, and Saskatchewan. On the short shoots, needles elongate rapidly and the annual stem increment- only about 1 mm (0.04 in)- is completed shortly after budbreak. On the long shoots, basal needles reach full length by mid- to late June in northern Wisconsin, whereas stem needles mature along the stem as it grows; stem elongation is completed by the end of July (5). Needles begin to turn yellow in early September in Michigan's Upper Peninsula and reach maximum color in early October in Michigan and northeastern Minnesota. Tamarack loses its needles in these same areas from about mid-September to mid-October (1,12).

Height growth apparently does not begin until the first needles are fully developed. In Michigan's Upper Peninsula height growth begins in late May and continues until mid-August (12). Diameter growth begins from early April to early June and ceases from late July to early August in northeastern Minnesota (I).

Because they are small, tamarack seedlings are easily killed during the first 6 or 8 weeks after germination. Early losses are primarily caused by damping-off; in the second and third years drought, drowning, and inadequate light sometimes cause appreciable loss. One-year-old seedlings grown in full light can survive desiccation of the upper 2 to 3 cm (1 in) of organic soils to as low as 45 to 65 percent by weight, whereas forest-grown seedlings 1 to 3 years old are fairly intolerant of drought (or flooding) (12).

Tamarack can tolerate a wide range of soil conditions but grows most commonly on wet to moist organic soils (Histosols) such as sphagnum peat and woody peat. The latter is usually better decomposed, has more nitrogen and mineral nutrients, and is less acid than sphagnum peat. Tamarack grows fairly well on extremely dry soils where these are shallow over bedrock or where the water table is low, but it can die from drought on such sites. The tree is found on mineral soils, especially Inceptisols and Entisols, that range from heavy clay to coarse sand; thus texture does not seem to be limiting. Although tamarack can grow well on calcareous soils, it is not abundant on the limestone areas of eastern Ontario (27) and is rare on those of the Gaspé Peninsula and Anticosti Island in Canada.

Because it can withstand high soil moisture, high acidity, and low soil temperature, tamarack is more abundant on peatlands than trees characteristic of surrounding uplands. It grows best, however, on more favorable sites such as moist but well-drained loamy soils along streams, lakes, and swamps; seep areas; and mineral soils with a shallow surface layer of organic matter (12). In Alaska tamarack grows well on upland sites having wind-deposited loess soils (50).

Tamarack is a characteristic tree of peatlands, especially in the southern limits of its range. It is found on the full range of peatlands from rich swamp (forested rich fen) to raised bog but is most characteristic of poor swamps where the soil water is weakly enriched with mineral nutrients (17). Farther north tamarack is still common on peatlands (38); in Alaska it occurs especially on bogs underlain by permafrost (perennially frozen soils) (50).

Tamarack often grows on much drier sites in the northern part of its range. Scattered individuals and sometimes stands are found on swamp margins, on the banks of streams and lakes, and on low ridges and benches and other upland sites. In the Hudson Bay lowlands, tamarack grows on both extensive fens (11) and beach ridges (38). In British Columbia it is often an upland tree, growing on the cool moist north slopes of mountains as well as in valley swamps.

Tamarack grows on sites with about the same elevation throughout most of its range. In eastern North America, however, the tree grows between sea level and 1220 m (4,000 ft); in the Canadian Rockies and Alaska it grows between about 180 and 520 m (600 and 1,700 ft) (12).

The principal commercial use of tamarack in the United States is for making pulp products, especially the transparent paper in window envelopes. Because of its rot resistance, tamarack is also used for posts, poles, mine timbers, and railroad ties. Other wood products include rough lumber, fuelwood, boxes, crates, and pails (23). In interior Alaska young tamarack stems are used for dogsled runners, boat ribs, and fishtraps (4); in northern Alberta the branches are used to make duck and goose decoys (50). Historically, knees from larger trees were used in wooden ship construction and Indians used the fine roots to sew birch bark, the wood for arrow shafts, and the bark for medicine (48).

Tamarack has certain wildlife values. Porcupines feed on the inner bark, snowshoe hares browse on seedlings, and red squirrels eat the seeds. Birds common in tamarack stands during the summer include the white-throated sparrow, song sparrow, veery, common yellowthroat, and Nashville warbler (7). The American osprey, a sensitive species, often nests in lowland types such as tamarack; and the great gray owl, a rare winter visitor in the northern Lake States, apparently nests there only in the tamarack peatlands of northern Minnesota.

Tamarack is esthetically appealing, especially in early autumn when its needles turn yellow. Although the tree has been infrequently planted for ornamental purposes (30), it has significant potential-even in Alaska (50)- because of its rapid growth and fall color. Tamarack is particularly valuable in suburban areas but is not suitable as a shade tree on city streets (18).

Tamarack has limited value as a watershed protector because it usually grows on gently sloping terrain, and management of the type probably has little or no effect on water yield or quality because harvesting is generally on a small scale.

Layering is apparently the dominant reproductive mode for tamarack along the northern limit of trees in Canada and Alaska (10,50), whereas farther south it is uncommon but may occur when branches are covered by fast-growing sphagnum moss or drifting sand. Roots are also known to produce shoots (12), and experience in Ontario shows that tamarack can be easily propagated from softwood cuttings taken in early July from young trees (probably less than 5 to 7 years old) (27).

Pinaceae -- Pine family

William F. Johnston

Tamarack (Larix laricina), also called eastern, American, or Alaska larch, and hackmatack, is a small- to medium-sized deciduous conifer extending from the Atlantic to central Alaska. One of the largest tamaracks recorded is in Maine and measures about 94 cm (36.9 in) in d.b.h. and 29 m (95 ft) in height. The heavy, durable wood is used principally for pulpwood, but also for posts, poles, rough lumber, and fuelwood. Wildlife use the tree for food and nesting; it is also esthetically appealing and has significant potential as an ornamental.

Tamarack has one of the widest ranges of all North American conifers. Its main range extends from Newfoundland and Labrador west along the northern limit of trees, and across the Continental Divide in northern Yukon Territory (52); then south in the Mackenzie River drainage to northeastern British Columbia and central Alberta; and east to southern Manitoba, southern Minnesota, southern Wisconsin, extreme northeastern Illinois, northern Indiana, northern Ohio, northern Pennsylvania, northern New Jersey, northern Connecticut, and Maine. It also grows locally in the mountains of northern West Virginia and adjacent western Maryland. A major disjunct area of tamarack is found in interior Alaska, in the Yukon and Kuskokwim River basins between the Brooks Range on the north and the Alaska Range on the south; three minor areas are near the Alaska-Yukon border.


- The native range of tamarack.

Tree, Deciduous, Monoecious, Habit erect, Trees without or rarely having knees, Tree with bark rough or scaly, Young shoots 3-dimensional, Buds not resinous, Leaves needle-like, Leaves alternate, Needle-like leaf margins entire (use magnification), Leaf apex acute, Leaves < 5 cm long, Leaves < 10 cm long, Leaves not blue-green, Needle-like leaves flat, Needle-like leaves not twisted, Needle-like leaf habit erect, Needle-like leaf habit drooping, Needle-like leaves per fascicle mostly 1, Needle-like leaves per fascicle > 10, Needle-like leaf sheath early deciduous, Needle-like leaf sheath persistent, Twigs glabrous, Twigs not viscid, Twigs with peg-like projections or large fascicles after needles fall, Berry-like cones orange, Woody seed cones < 5 cm long, Bracts of seed cone included, Seeds brown, Seeds yellow, Seeds winged, Seeds unequally winged, Seed wings prominent, Seed wings equal to or broader than body.

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Larix laricina, commonly known as the tamarack,^[3] hackmatack,^[3] eastern larch,^[3] black larch,^[3] red larch,^[3] or American larch,^[3] is a species of larch native to Canada, from eastern Yukon and Inuvik, Northwest Territories east to Newfoundland, and also south into the upper northeastern United States from Minnesota to Cranesville Swamp, West Virginia; there is also an isolated population in central Alaska.^[4] The word akemantak is an Algonquian name for the species and means "wood used for snowshoes".

Description

Larix laricina is a small to medium-size boreal coniferous and deciduous tree reaching 10–20 m (33–66 ft) tall, with a trunk up to 60 cm (24 in) diameter. Tamaracks and larches (Larix species) are deciduous conifers. The bark is tight and flaky, pink, but under flaking bark it can appear reddish. The leaves are needle-like, 2–3 cm (3⁄4–1+1⁄4 in) short, light blue-green, turning bright yellow before they fall in the autumn, leaving the pale pinkish-brown shoots bare until the next spring. The needles are produced spirally on long shoots and in dense clusters on long woody spur shoots. The cones are the smallest of any larch, only 1–2.3 cm (3⁄8–7⁄8 in) long, with 12-25 seed scales; they are bright red, turning brown and opening to release the seeds when mature, 4 to 6 months after pollination.^[5]

Key characteristics:^[6]

• The needles are normally borne on a short shoot in groups of 10–20 needles.
• The larch is deciduous and the needles turn yellow in autumn.
• The seed cones are small, less than 2 cm (3⁄4 in) long, with lustrous brown scales.
• Larch are commonly found in swamps, fens, bogs, and other low-land areas.

Distribution and ecology

Tamaracks are very cold tolerant, able to survive temperatures down to at least −65 °C (−85 °F), and commonly occurs at the Arctic tree line at the edge of the tundra. Trees in these severe climatic conditions are smaller than farther south, often only 5 m (15 ft) tall. They can tolerate a wide range of soil conditions but grow most commonly in swamps, bogs, or muskegs, in wet to moist organic soils such as sphagnum, peat, and woody peat. They are also found on mineral soils that range from heavy clay to coarse sand; thus texture does not seem to be limiting. Although tamarack can grow well on calcareous soils, it is not abundant on the limestone areas of eastern Ontario.

Tamarack is generally the first forest tree to grow on filled-lake bogs. In the lake states, tamarack may appear first in the sedge mat, sphagnum moss, or not until the bog shrub stage. Farther north, it is the pioneer tree in the bog shrub stage. Tamarack is fairly well adapted to reproduce successfully on burns, so it is one of the common pioneers on sites in the boreal forest immediately after a fire.^[7]

The central Alaskan population, separated from the eastern Yukon populations by a gap of about 700 kilometres (430 mi), is treated as a distinct variety Larix laricina var. alaskensis by some botanists, though others argue that it is not sufficiently distinct to be distinguished.

Associated forest cover

Tamarack forms extensive pure stands in the boreal region of Canada and in northern Minnesota. In the rest of its United States range and in the Maritime Provinces, tamarack is found locally in both pure and mixed stands. It is a major component in the Society of American Foresters (SAF) forest cover types Tamarack and black spruce–tamarack.

Black spruce (Picea mariana) is usually tamarack's main associate in mixed stands on all sites. The other most common associates include balsam fir (Abies balsamea), white spruce (Picea glauca), and quaking aspen (Populus tremuloides) in the boreal region. In the better organic soil sites in the northern forest region, the most common associates are the northern white-cedar (Thuja occidentalis), balsam fir, black ash (Fraxinus nigra), and red maple (Acer rubrum). In Alaska, quaking aspen and tamarack are almost never found together. Additional common associates are American elm (Ulmus americana), balsam poplar (Populus balsamifera), jack pine (Pinus banksiana), paper birch (Betula papyrifera), Kenai birch (B. papyrifera var. kenaica), and yellow birch (B. alleghaniensis).

Tamarack stands cast light shade and so usually have a dense undergrowth of shrubs and herbs. Because the tree has an extensive range, a great variety of shrubs is associated with it. Dominant tall shrubs include dwarf and swamp birch (Betula glandulosa and Betula pumila), willows (Salix spp.), speckled alder (Alnus rugosa), and red-osier dogwood (Cornus stolonifera). Low shrubs include bog Labrador tea (Ledum groenlandicum), bog-rosemary (Andromeda glaucophylla), leather leaf (Chamaedaphne calyculata), and small cranberry (Vaccinium oxycoccos). Characteristically the herbaceous cover includes sedges (Carex spp.), cottongrass (Eriophorum spp.), three-leaved false Solomonseal (Maianthemum trifolium), marsh cinquefoil (Potentilla palustris), marsh-marigold (Caltha palustris), and bogbean (Menyanthes trifoliata). Ground cover is usually composed of sphagnum moss (Sphagnum spp.) and other mosses.

Seed cones and pollen cones

Tamarack is monoecious. Male and female cones are small, either solitary or in groups of 2 or 3, and appear with the needles. Male cones are yellow and are borne mainly on 1- or 2-year-old branchlets. Female cones resemble tiny roses. They are reddish or maroon, have needles at their base which are shorter and bluer than the other needles on the tree. They are borne most commonly on 2 to 4-year-old branchlets, but may also appear on branchlets 5 or more years old. Cones usually are produced on young growth of vigorous trees. On open-grown trees, cones are borne on all parts of the crown. Mature seed cones are brown, oblong-ovoid, and 13 to 19 mm (1⁄2 to 3⁄4 in) long.

Uses

The wood is tough and durable, but also flexible in thin strips, and was used by the Algonquian people for making snowshoes and other products where toughness was required. The natural crooks located in the stumps and roots are also preferred for creating knees in wooden boats. Currently, the wood is used principally for pulpwood, but also for posts, poles, rough lumber, and fuelwood; it is not a major commercial timber species. Tamarack wood is also used as kickboards in horse stables.^[8]Older Log homes built in the 19th century sometimes incorporated tamarack along with other species like red or white oak. The hewn logs have a coarse grainy surface texture.

It is also grown as an ornamental tree in gardens in cold regions. Several dwarf cultivars have been created that are available commercially.^[9][10] Tamarack is commonly used for bonsai.^[11]

Tamarack poles were used in corduroy roads because of their resistance to rot. Tamarack posts were used before 1917 in Alberta to mark the northeast corner of sections surveyed within townships. They were used by the surveyors because at that time the very rot-resistant wood was readily available in the bush and was light to carry. Their rot resistance was also why they were often used in early water distribution systems.

The aboriginal peoples of Canada's northwest regions used the inner bark as a poultice to treat cuts, infected wounds, frostbite, boils and hemorrhoids. The outer bark and roots are also said to have been used with another plant as a treatment for arthritis, cold and general aches and pains.^[12]

Wildlife use the tree for food and nesting. Porcupines eat the inner bark, snowshoe hares feeds on tamarack seedlings, and red squirrels eat the seeds.^[13] Birds that frequent tamaracks during the summer include the white-throated sparrow, song sparrow, veery, common yellowthroat, and Nashville warbler.^[14]

Reaction to competition

Tamarack is very intolerant of shade. Although it can tolerate some shade during the first several years, it must become dominant to survive. When mixed with other species, it must be in the over story. The tree is a good self-pruner, and boles of 25- to 30-year-old trees may be clear for one-half or two-thirds their length.

Because tamarack is very shade-intolerant, it does not become established in its own shade. Consequently, the more tolerant black spruce eventually succeeds tamarack on poor bog sites, whereas northern white-cedar, balsam fir, and swamp hardwoods succeed tamarack on good swamp sites. Recurring sawfly outbreaks throughout the range of tamarack have probably sped the usual succession to black spruce or other associates.

Various tests on planting and natural reproduction indicate that competing vegetation hinders tamarack establishment.

The shade-intolerance of tamarack dictates the use of even-aged management. Some adaptation of clear cutting or seed-tree cutting is generally considered the best silvicultural system because tamarack seeds apparently germinate better in the open, and the seedlings require practically full light to survive and grow well. Tamarack is also usually wind-firm enough for the seed-tree system to succeed. Satisfactory reestablishment of tamarack, however, often requires some kind of site preparation, such as slash disposal and herbicide spraying.

Damaging agents

The tamarack has thin bark and is therefore highly susceptible to fire damage, except perhaps in older, upland stands. However, the habitat of tamarack, especially south of the boreal forest, is normally wet enough to protect the tree from fire. The tamarack is also susceptible to high winds. Strong winds can uproot large tamarack trees growing in swamps or other wet-land sites where rooting is shallow. It has also been discovered that abnormally high water levels often kill tamarack stands. Those that survive under such conditions usually grow very slowly. Other effects of high water include dieback and the development of adventitious roots and shoots. Wetland road crossings and beaver damming are the primary causes of flooding.

Many insect species are known to be destructive to tamaracks. The non-indigenous larch sawfly is the most destructive. Epidemics occur periodically across Canada and the northern United States and have caused tremendous losses of merchantable tamarack throughout most of the tree's range. Indications are that radial increment declines markedly after 4 to 6 years of outbreak. After 6 to 9 years of moderate to heavy defoliation, the trees die. In southeastern Manitoba and northern Minnesota, however, imported parasites of the sawfly have become established and should reduce the frequency and duration of future outbreaks. Another serious defoliator is the larch casebearer Coleophora laricella. The larch casebearer attacks tamarack of all ages, and several severe outbreaks have caused extensive mortality in some areas. Outbreak severity has lessened in recent years, however, probably due to imported parasites of the casebearer that have become widely established.

Only a few other insects and related organisms (such as mites) that feed on tamarack are known to sometimes cause serious injury. During an outbreak, the spruce budworm (Choristoneura fumiferana) can severely damage tamarack. The larch-bud moth (Zeiraphera improbana) has had occasional short epidemics, and the spruce spider mite (Oligonychus ununguis) is occasionally found in large numbers on tamarack. The larch-shoot moth (Argyresthia laricella) is widely distributed, but serious injury is unusual. One of the most common bark beetles attacking tamarack is the eastern larch beetle (Dendroctonus simplex), but it feeds mainly on weakened, dying, or dead trees.

Tamarack is a host to many pathogens, but only one cause diseases serious enough to have an economic impact on its culture, the Lachnellula willkommii fungus. It is a relatively new pathogen in Canada, first recorded in 1980 and originating in Europe. The fungus cause large cankers to form and a disease known as larch canker which is particularly harmful to the tamarack larch, killing both young and mature trees.^[15] Apart from this, the only common foliage diseases are rusts, such as the leaf rust in eastern and central North America. However, this rust, caused by the fungus Melampsora medusae, and other rusts do little damage to tamarack. The needle-cast fungus Hypodermella laricis has attacked tamarack in Ontario and has the potential for local damage.

Gallery

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  Young female cone

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  Old seed cones

See also

• Larch ball

References

• https://srs.fs.usda.gov/pubs/misc/ag_654/volume_1/larix/laricina.htm

Retrieved from "https://en.wikipedia.org/w/index.php?title=Larix_laricina&oldid=1158325023"

Larix laricina, commonly known as the tamarack, hackmatack, eastern larch, black larch, red larch, or American larch, is a species of larch native to Canada, from eastern Yukon and Inuvik, Northwest Territories east to Newfoundland, and also south into the upper northeastern United States from Minnesota to Cranesville Swamp, West Virginia; there is also an isolated population in central Alaska. The word akemantak is an Algonquian name for the species and means "wood used for snowshoes".