Bigtooth Aspen

bigtooth aspen
largetooth aspen
aspen

More info for the term: cover

Bigtooth aspen provides cover for ruffed grouse. The best cover is
provided by 5- to 25-year-old sapling stands with 3,000 to 8,000 stems
per acre (7,000-20,000 stems/ha) [20].

More info for the terms: capsule, dioecious, forest, fruit, tree

Bigtooth aspen is a native, short-lived, dioecious, medium-sized
deciduous tree with a straight trunk and gently ascending branches. It
is distinguished from quaking aspen by slightly larger leaves and large
irregular teeth on the leaf edges. The fruit is a two-valved capsule
[12,43].

Bigtooth aspen is a rapidly growing tree. At maturity, it attains
heights of 60 to 80 feet (18-24 m) and diameters at breast height of 8
to 10 inches (20-25 cm). Stands begin to deteriorate after 50 to 70
years on good sites, but individuals may live as long as 100 years [29].

Bigtooth aspen is a clonal species. Clones resemble small groves
consisting of many individual stems [7].

The roots of bigtooth aspen are shallow and wide spreading; the lateral
root spread of a tree in a forest may be 33 to 66 feet (10-20 m).
Generally, four to five lateral roots originate from the tree and then
branch within 2 feet (0.6 m). Vertical, penetrating roots near the base
anchor the tree [29].

The bark of young trees is smooth, but after three or more decades, it
becomes rough and develops grooves [7].

Bigtooth aspen primarily occurs in the northeastern United States,
southeastern Canada, and the Great Lakes Region. Its range extends from
Virginia north to Maine and Cape Breton Island, Nova Scotia; west to
southeastern Manitoba and Minnesota; south through Iowa to extreme
northeastern Missouri; and east through Illinois, Indiana, Ohio, and
West Virginia. Disjunct populations are found in Kentucky, Tennessee,
North Carolina, and South Carolina [29,30].

More info for the terms: climax, competition, fire interval, fire regime, fire suppression, forest, fuel, grassland, litter, natural, seed, tree

Although bigtooth aspen is easily top-killed by fire, extensive
vegetative reproduction, prolific off-site seed production, and the
tenacity and lateral extent of its roots enable bigtooth aspen to
perpetuate after fire [44,56]. Removal of the overstory and heating of
the soil stimulate the sprouting of aspen roots [43,44,48]. Fire also
creates a suitable seedbed and reduces competition [56].

Aspen almost always retains or extends its range following fire [15].
The extensive aspen root system allows it to dominate the postfire
forest, even if aspen was only a minor component of the prefire stand
[13,44]. Aspen roots persist an undetermined length of time in the
absence of canopy aspen, making it possible for aspen to regenerate in a
stand in which aspen was not even represented in the prefire overstory
[44].

Aspen-dominated forests do not readily burn, especially when young and
healthy [15,27,44]. Slow burning, low-severity surface fires are
typical [15,25,27,48]. Decadent aspen stands contain more fuel and are
more likely to burn than younger stands [15,44]. An understory of
conifer species increases the flammability of aspen stands [24].
However, aspen is generally incapable of supporting a severe fire [25].
Crown fires in the surrounding forest generally drop into surface and
ground fuels when they enter aspen stands [15].

Fire every 150 years may be necessary to maintain aspen [56].
Presettlement fires in aspen stands probably occurred most often in the
fall when fuels are dry and leaf litter is deep [31]. The presettlement
fire interval of aspen-birch-fir forests in the Great Lakes Region is
estimated to have been about 80 years for very large [greater than
10,000 acre (4,000 ha)] fires [24].

Aspen-birch forests may have burned at intervals of 50 years or less
[23]. Fahey and Reiners [71] estimated that aspen-birch forests in
Maine had a 100-year fire interval during the 50-year period from 1909
to 1959. However, this estimate may be high because fires were
declining during this time period due to fire suppression.

Heinselman [24] suggested that aspen parklands had fire intervals of 10
years for large [1,001 to 10,000 acre (400-4,000 ha)] fires.
Although quaking aspen is the principal tree in aspen parklands [24],
bigtooth aspen occurs in the prairie-forest edge in Minnesota [19].

Historically, bigtooth aspen frequently occurred in vegetational
patterns that are associated with fire. For instance, bigtooth aspen
occurred with oak and quaking aspen along the west side of the Big Woods
in Minnesota. These fire-tolerant species served as a firebreak between
the frequently burned prairie and the fire-sensitive climax forest of
the Big Woods. Aspen served as a fire break because grassland fires
normally did not travel far into aspen stands due to low flammability.
However, fuel would build up in the aging aspen stands and eventually an
intense fire would destroy the aboveground biomass, rejuvenate the
aspen, and eliminate the less fire-tolerant species. At the same time,
frequent fire in the prairie prevented aspen expansion [19].

Another example of a fire-influenced vegetational pattern is in the
Boundary Waters Canoe Area in Minnesota. Aspen commonly occurs in areas
that frequently burn, such as large uplands areas distant from water and
upwind of natural fire breaks such as lakes [23].

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 terms: density, duff, fuel, fuel loading, hardwood, litter, low-severity fire, moderate-severity fire, wildfire

Prescribed fire is used as a management tool to regenerate aspen stands
[41]. Moderate-severity fire which kills all remaining canopy stems and
removes duff is recommended following harvest to maximize the number of
suckers [25]. A low-severity fire does not always induce sufficiently
dense and vigorous suckers to regenerate an aspen stand [25].

Soil nutrient concentrations increased after wildfire on both clearcut
and wholetree harvested sites that had formerly supported adjacent
northern red oak-bigtooth aspen forests [73].

A mature aspen stand that is clearcut will generally have enough slash
for fire to kill any residual standing trees. Fuel loadings of at least
10 tons per acre (22 t/ha) of slash less than 3 inches (8 cm)
in diameter are recommended [41]. Refer to Beyerhelm and Sando [72] for
fuel loading estimation techniques for aspen-northern hardwood stands.

The recommended weather conditions needed to burn a harvested aspen site
are reported for those stands with less than 25 percent conifers,
greater than 25 percent conifers, and with little slash [41].

In northern lower Michigan, Scheiner and others [52] studied the
vegetational response to clearcutting followed 1 year later by burning.
Prior to cutting, bigtooth aspen dominated the site with 153 stems per
acre (378 stems/ha). One year postcut, but prefire, the vegetation was
dominated by red maple, northern red oak, and paper birch (Betula
papyrifera) sprouts. However, in postfire year 1, bigtooth aspen was
again the most abundant species with 9,911 sucker stems per acre (24,481
stems/ha). Although declining in number, bigtooth aspen continued to
dominate the site for the duration of the study (5 years).

Weber [64] studied the response of a quaking aspen and bigtooth aspen
stand to four different treatments: surface burning before and after
spring leaf flush and clearcutting before and after leaf flush. Three
years after treatment, the preflush cut had the greatest stem density,
average height, and basal diameter. Both cut treatments had greater
stem densities than the burn treatments. The preflush cut treatment
probably had more stems than the postflush cut treatment because
carbohydrate root reserves were not depleted.

One reason for low rates of suckering after prescribed burning was that
the fires did not completely kill the overstory. The existing trees
survived one to two postfire growing seasons and continued to show
apical dominance, thereby preventing sucker development. The postflush
fire resulted in more suckers than the preflush fire, probably because
it was a hotter fire and killed more overstory trees [64].

Simard and others [55] developed equations for using postfire
observations to predict fire-caused injury to and mortality in aspen.

The National Fire-Danger Rating System uses the total ash and
silica-free ash content of fuels as one of its variables. Ash is a
noncombustible constituent of organic material and reduces the
combustion rate of fuel. In a study in Michigan, the total ash content
of dead bigtooth aspen litter fuels was 3.7 percent in the fall, 5.4
percent in the spring, and 6.2 percent in early summer. The silica-free
ash content was 2.0, 2.8, and 3.5 percent for fall, spring, and early
summer, respectively [31].

Ambrosia beetle (Xyleborus saxesceni) attacks fire-damaged bigtooth
aspen [58].

Because of its low flammability, bigtooth aspen has been recommended for
use in fire breaks, especially on droughty, sandy sites [27].

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More info for the term: phanerophyte

Phanerophyte

Bigtooth aspen most commonly occur on floodplains, gently rolling
terrain, and the lower slopes of uplands. Large stands grow on sands,
loamy sands, and light sandy loams. However, minor amounts of bigtooth
aspen are found growing on almost any type of soil [29,41]. Bigtooth
aspen has a lower soil pH limit of 4.0 [63].

Bigtooth aspen tolerates drier conditions than quaking aspen [2,17,47].
It has been classified as a subxeric species [10]. However, for good
growth on upland sites the water table must be at least 2 feet (0.6 m),
but not more than 5 feet (1.5 m), below the ground surface. The soil
must be moist but well aerated for good growth [29].

Bigtooth aspen ranges in elevation from sea level to over 3,000 feet (915
m) in North Carolina [29].

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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
14 Northern pin oak
15 Red pine
16 Aspen
17 Pin cherry
18 Paper birch
19 Gray birch - red maple
21 Eastern white pine
25 Sugar maple - beech - yellow birch
32 Red spruce
33 Red spruce - balsam fir
35 Paper birch - red spruce - balsam fir
37 Northern white-cedar
43 Bear oak
46 Eastern redcedar
55 Northern red oak
60 Beech - sugar maple
108 Red maple

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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
FRES15 Oak - hickory
FRES18 Maple - beech - birch
FRES19 Aspen - birch

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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 term: forest

K095 Great Lakes pine forest
K096 Northeastern spruce - fir forest
K103 Mixed mesophytic forest
K104 Appalachian oak forest
K106 Northern hardwoods
K107 Northern hardwoods - fir forest
K108 Northern hardwoods - spruce forest

More info for the terms: fuel, low-severity fire, severity

Bigtooth aspen trees are very susceptible to fire, although bigtooth
aspen roots are very fire resistant. Bigtooth aspen bark is thin and
does not protect the cambium from heat damage [29]. If there is
sufficient fuel in a young sapling stand for a fire to burn, the fire
will kill the saplings [44]. An average scorch height of 0.6 feet (0.2
m) will kill most aspen stems smaller than 6 inches (15 cm) in dbh [55].

Since most fires in aspen are of low severity, mature trees do not
always succumb to fire. However, basal wounds caused by low-severity
fire serve as entry points for disease organisms [29,44].

Prolonged drought and large amounts of slash are required to raise the
soil temperature high enough to kill the roots of aspen [25]. Bigtooth
aspen roots are deeper in the soil than quaking aspen roots, making root
damage from fire highly unlikely in bigtooth aspen [40].

More info for the terms: cover, forest, hardwood

Bigtooth aspen provides food and cover for wildlife. Moose and
white-tailed deer browse bigtooth aspen [3,60]. Beaver eat bark,
leaves, twigs, and branches [29].

Aspen provides the basic habitat for ruffed grouse over much of its
range. Ruffed grouse feed on the leaves in the summer, staminate flower
buds in the winter, and catkins prior to the breeding season. In
feeding, ruffed grouse prefer quaking aspen to bigtooth aspen [20].

Approximately 116 nongame bird species breed in aspen-birch (Betula
spp.) forests [5].

Cavity nesters use bigtooth aspen [21,65]. In a mixed hardwood forest
in central New York, bigtooth aspen accounted for 25 percent of the
trees with cavities although it made up only 12 percent of the potential
cavity trees sampled [65].

More info for the terms: association, codominant, fern, hardwood, shrub, tree

Bigtooth aspen usually grows in even-aged mixed stands, most commonly
with quaking aspen [29,43]. It is a codominant tree in both hardwood
and conifer forests [13]. Bigtooth aspen does not occur as a subdominant
species because of its extreme shade intolerance [38].

Quaking aspen is the predominant species in aspen stands in the
Northeast and Great Lakes Region, but bigtooth aspen dominates
on the drier upland sites [13,17]. Aspen stands dominated by bigtooth
aspen are generally more open than those dominated by quaking aspen
[17].

Overstory associates not previously mentioned in DISTRIBUTION AND
OCCURRENCE include balsam poplar (Populus balsamifera), bur oak (Quercus
macrocarpa), white oak (Q. alba), basswood (Tilia americana), black
cherry (Prunus serotina), and sassafras (Sassafras albidum) [29].

A tall shrub layer is an important component of aspen forests [35].
Shrub associates include chokecherry (Prunus virginiana), downy
serviceberry (Amelanchier arborea), dogwood (Cornus spp.), willow (Salix
spp.), beaked hazel (Corylus cornuta), speckled alder (Alnus rugosa),
American hazel (Corylus americana), and sweetfern (Comptonia peregrina)
[13,29].

Bracken fern (Pteridium aquilinum) and dwarf bush-honeysuckle (Diervilla
lonicera) are frequent subdominant understory species in bigtooth aspen
stands [17,29,56].

Bigtooth aspen is listed as a dominant or codominant species in the
following publications:

1. Wilderness Ecology: virgin plant communities of the Boundary Waters
Canoe Area [35]
2. Aspen association in northern lower Michigan [17]

More info for the term: tree

Tree

More info for the terms: basal area, density

In the literature, the management of bigtooth aspen is rarely
distinguished from that of quaking aspen.

In order to regenerate a well-stocked vigorous aspen stand, the
overstory must be removed [29,41]. Removing apical dominance stimulates
aspen suckering [41,64]. If the parent stand is not harvested, it can
be removed by shearing, chainsaw felling, girdling, treating with
herbicide, or prescribed burning [41,42]. Discing and roller chipping
are not recommended because these techniques damage the roots [41].

For optimum sucker density the parent aspen stand must have had at
least 20 square feet basal area per acre (4.6 sq m/ha). At age two, an
adequately stocked sucker stand exceeds 4,000 to 5,000 stems per acre
(10,000-12,000 stems/ha) [41].

Although aspen groves thin naturally, additional thinning improves
growth [29]. When thinning, bigtooth aspen should be favored over
quaking aspen because of its superior growth and resistance to disease
and insects, especially on dry sites [2,41]. Clones with superior
growth and stem form should also be favored. Yields differ as much as
200 percent between clones on the same site [41]. Barnes [7] has
developed a list of characteristics to use when distinguishing between
clones in any given season.

Only one thinning is recommended for aspen forests managed for pulp.
The stand should be thinned at age 30, leaving 240 trees per acre (590
trees/ha). Two thinnings are recommended if sawtimber is desired, one
at age 10 leaving 550 trees per acre (1,360 trees/ha) and one at age 30
leaving 200 trees per acre (490 trees/ha). The final cut should be
delayed for as long as the stand is healthy [41].

Repeated harvest of aspen on a site, especially by the whole-tree
method, may reduce long-term productivity [2]. Short-term rotation
management also reduces a stand's long-term health. Repeated
short-rotation aspen harvest increases the colonization rate of
Armillaria root rot (Armillaria mellea) [57].

Regeneration failure of aspen occurs if roots have been damaged by
harvesting equipment. Aspen harvested on flat or gently rolling sites
early in the summer may also have regeneration problems because of
saturated soils [8].

Genetic improvement research on aspen has been conducted in the past two
decades because of the increasing importance of aspen as a source of raw
material for the pulp and paper industries. However, most recent work
has concentrated on quaking aspen [4].

Bigtooth aspen responded to fertilizer (nitrogen, phosphorus, and lime
in various combinations) with increased height, diameter, and volume
growth during the 10-year period following the treatments. However,
mortality of quaking aspen fertilized with nitrogen suggests further
study is necessary before utilizing widespread fertilizer application in
bigtooth aspen stands [49].

Herbicides control bigtooth aspen [34,66].

Bigtooth aspen is more disease resistant than quaking aspen. The most
serious disease of bigtooth aspen is Hypoxylon canker (Hypoxylon
mammatum) [29,68]. Other rots, fungi, and root decay affect this
species [29]. Bigtooth aspen is a preferred host of gypsy moth. Death
occurs when nearly complete defoliation by gypsy moth is followed by a
fungal infection by Armillaria spp. [22].

By cutting trees and damming waterways, beaver destroy large aspen
stands [29].

Biomass estimates have been reported for bigtooth aspen [36,39].

Dry-weight bigtooth aspen browse averages 5.0 percent protein, 3.4
percent ether extract, 14.8 percent crude fiber, and 26.6 percent
nitrogen-free extract [61]. The simulation of animal use by clipping did
not alter the nutritional quality of bigtooth aspen browse [11].

Other normal foliar nutrient levels have been reported [9].

CT DE IL IN IA KY ME MD MA MI
MN MO NH NJ NY NC OH PA RI SC
TN VT VA WV WI MB NB NS ON PE
PQ

Bigtooth aspen leaves are highly palatable to ruffed grouse [20].

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Flowering in bigtooth aspen occurs in April or May, depending on air
temperature. The seeds mature in May or June. Seeds disperse before
the leaves are fully expanded. Bigtooth aspen flowers, foliates, and
disperses seeds about 1 to 3 weeks later than quaking aspen in the same
location [1,14,29].

More info for the terms: competition, density, duff, fire severity, hardwood, low-severity fire, moderate-severity fire, severity, shrub, tree

A fire-killed aspen stand regenerates from surviving roots [25,29,44],
which are stimulated to produce suckers when apical dominance is removed
[44,64].

Roots must have a high cytokinin to auxin ratio to initiate sucker
growth. If a low-intensity fire girdles aspen such that the downward
movement of auxin in the phloem is interrupted but the upward movement
of cytokinin continues in the xylem, the tree may survive for several
years. Since the cytokinin continues to move out of the roots, it does
not accumulate, and suckers do not develop [64].

Roots are stimulated to sprout if the soil is heated [25,29]. The soil
is heated not only by the fire, but also by blackening of the soil
surface and removal of overstory and duff [48].

The density and growth of suckers is dependent in part on fire severity.
A low-severity fire that does not kill all of the overstory does not
result in suckers as dense or vigorous as those produced after a
moderate-severity fire [25].

Fire also prepares a favorable seedbed for bigtooth aspen. Seeds from
off-site sources may blow onto burned sites and establish if there is
sufficient moisture and if the competition is not severe [14,56].

Most shrub species in the understory of aspen forests are able to sprout
after fire [13], as are many hardwood associates [38].

More info for the term: root sucker

Tree with adventitious-bud root crown/soboliferous species root sucker
Initial-offsite colonizer (off-site, initial community)

More info for the terms: basal area, competition, density, forest, fruit, phenology, seed, tree

Bigtooth aspen regenerates by seed and vegetative reproduction.

Bigtooth aspen is a prolific seed producer; a single tree may produce
more than 1.5 million seeds [29]. Bigtooth aspen generally has good or
better crops (greater than 61% of a full crop) 2 out of every 3 years
[18]. The light seeds are dispersed long distances by wind [29].
Germination rates are high [14,29]. Seeds germinate under a wide range
of temperatures as long as there is sufficient moisture. They will even
germinate when submerged in water [14]. Despite high seed production
and high germination rates, seedling establishment is uncommon. Few
seedlings reach more than a few inches in height. Bare moist soil free
of competition is necessary for seedling establishment. Short seed
viability (2-3 weeks) also limits establishment. A seedling may grow 6
to 8 inches (15-20 cm) the first year [14,29].

Most bigtooth aspen forests regenerate vegetatively. When the parent
tree is killed or the soil is heated, suckers develop from extensive,
shallow lateral roots. Bigtooth aspen roots that produce suckers are
generally less than 1 inch (2.5 cm) in diameter and about 3 to 7 inches
(7.5-17.8 cm) deep. A sucker grows 3 to 6 feet (0.9-1.8 m) the first
year, considerably more than a seedling. After a mature aspen stand is
destroyed by fire or logging, roots may produce 3,200 to 24,000 suckers
per acre (8,000-60,000/ha) [29]. Root suckers are initially dependent
on the parent roots for water and nutrients. Their dependence decreases
with time but is still substantial after 25 years. By age 25, the
parent roots contribute the nutrient requirements for approximately half
the yearly growth [68].

Multiple suckers result in a clone, a multistemmed vegetatively
reproduced individual. Interclonal differences can be substantial,
especially in sprouting ability [7,36]. Within a stand, clones are
distinguished by sex, phenology, leaf morphology, disease resistance,
bark and stem differences, branching habits, and other characteristics
[7].

Sakai and Sharik [51] investigated the hypothesis that female bigtooth
aspen clones would invest energy in fruit production at the expense of
vegetative growth. They found no significant differences (P>0.05) in
mean dbh or basal area density (basal area per unit clonal area) between
male and female clones.

The roots of bigtooth aspen may remain alive in a forest long after the
last tree has died. The longevity of bigtooth aspen roots has not been
documented. However, the roots of quaking aspen are known to persist in
the absence of an aspen canopy. The roots are sustained by transient
suckers that survive only a few years [54].

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More info for the terms: forest, mesic, root crown, succession

Bigtooth aspen is very shade intolerant [6,29,38]. It is a pioneer
species on disturbed sites [13]. It persists in seral communities until
senescence. Because of the tenacity and lateral extensiveness of its
roots, aspen is able to regenerate and dominate disturbed sites that
only had a minor aspen component in the original stand [13,44].

Palik and Pregitzer [38] reported no evidence of past suppression nor
release of bigtooth aspen in a mature aspen forest. They suggest that
most suppressed bigtooth aspen stems die.

The rapid height growth of bigtooth aspen suckers allows it to
outcompete other sprouting species such as northern red oak (Quercus
rubra) and red maple (Acer rubrum) on many sites. Another reason for
bigtooth aspen's propensity to dominate a site after disturbance is the
large amount of space its lateral roots occupy. Oaks (Quercus spp.) and
maples (Acer spp.) are generally limited to stump and root crown sprouts
[38].

In the absence of disturbance, bigtooth aspen is replaced by conifers
and hardwoods. On dry sites aspen is replaced by red pine (Pinus
resinosa), oak, and red maple; on intermediate sites by eastern white
pine (Pinus strobus); and on mesic sites by northern hardwoods, spruce
(Picea spp.), and fir (Abies spp.) [13,37,56].

In the Great Lakes Region at the turn of the century, many mature pine
forests were logged and burned. Bigtooth aspen and quaking aspen
frequently dominated the postdisturbance forests [17,27,37,50,56].
Without fire or other disturbance, these forests are being replaced by
later successional, shade-tolerant species [37,50].

In a study of forest succession in northern Michigan, bigtooth aspen,
which dominated the postfire forest, was replaced by red maple and
eastern white pine within 53 years [53].

On fine till soils in central New Hampshire, early successional species
including aspen dominate postdisturbance stands. These species are
replaced by sugar maple (Acer saccharum) and American beech (Fagus
grandifolia) [69].

In the absence of fire, aspen-birch forests in Maine are succeeded by
spruce [70].

The currently accepted scientific name for bigtooth aspen is Populus
grandidentata Michx. (Salicaceae) [29,30]. Bigtooth aspen, along with five
other aspen species, has been assigned to the subsection Trepidae of
the section Leuce in the genus Populus. Because of their similarities,
these six species are sometimes considered a single super species [44].
Bigtooth aspen and quaking aspen (P. tremuloides) are the only two North
American aspen species.

In literature concerning areas where both North American aspen species
occur, many authors do not distinguish between bigtooth aspen and
quaking aspen. The information is reported about "aspen" in general.
In this review, "aspen" is used when citing studies in which both
species are discussed collectively.

Bigtooth aspen naturally hybridizes with the following species [29,30]:

x P. tremuloides: P. xsmithii Boivin
x P. alba (white poplar): P. xrouleauiana Boivin

More info for the term: seed

Bigtooth aspen is of limited importance for revegetating coal mine
spoils. Bigtooth aspen has been planted on mine spoils in Ohio and West
Virginia [63].

Bigtooth aspen naturally regenerated on acidic sites in Pennsylvania,
especially on sites where the soil had been ameliorated [26].

Bigtooth aspen regenerated naturally on barren, acidic,
metal-contaminated soil near Sudbury, Ontario. The soil, contaminated
by smelter fallout, had been treated with a surface application of
limestone. Bigtooth aspen apparently colonized the site from off-site
seed [67].

More info for the term: fuel

Bigtooth aspen wood is light colored, straight grained, finely textured,
and soft. It is primarily used for pulp, but is also used to make
particle board and structural panels. Minor uses include log homes,
pallets, boxes, match splints, chopsticks, hockey stick components, and
ladders [33,43].

Bigtooth aspen bark is pelletized for fuel and supplemental cattle feed
[29].

Bigtooth aspen is found in pure aspen forest covers either singly or in various combinations with quaking aspen and balsam poplar (Populus balsamifera). Balsam poplar is a minor component of this combination on the dry-mesic sites and bigtooth aspen is a minor component on the wet-mesic sites (4).

The species is a major component of the forest cover type Aspen (Society of American Foresters Type 16) and is a minor component in the following types (8):

1 Jack Pine
5 Balsam Fir
14 Northern Pin Oak
15 Red Pine
17 Pin Cherry
18 Paper Birch
19 Gray Birch-Red Maple
21 Eastern White Pine
25 Sugar Maple-Beech-Yellow Birch
32 Red Spruce
33 Red Spruce-Balsam Fir
35 Paper Birch-Red Spruce-Balsam Fir
37 Northern White-Cedar
43 Bear Oak
46 Eastern Redcedar
60 Beech-Sugar Maple
108 Red Maple

In the northern part of its range, common tree associates are quaking aspen, balsam poplar, balsam fir (Abies balsamea), paper birch (Betula papyrifera) gray birch (B. populifolia), jack pine (Pinus banksiana), red pine (P resinosa), red maple (Acer rubrum), and white spruce (Picea glauca). To the south and east, common tree associates are sugar maple (Acer saccharum), northern red oak Quercus rubra), bur oak (Q. macrocarpa), northern pin oak (Q. ellipsoidalis), white oak (Q. alba), eastern white pine (Pinus strobus), basswood (Tilia americana), pin cherry (Prunus pensylvanica), black cherry (P serotina), and sassafras (Sassafras albidum).

Common shrub associates are chokeberry (Prunus virginiana), downy serviceberry (Amelanchier arborea), dogwood (Cornus spp.), willow (Salix spp.), beaked hazel (Corylus cornuta), speckled alder (Alnus rugosa), highbush cranberry (Viburnum trilobum), American hazel (Corylus americana), and sweetfern (Comptonia peregrina). Common ground flora are blueberry (Vaccinium spp.), teaberry (Gaultheria procumbens), bracken (Pteridium aquilinum var. latiusculum), fly honeysuckle (Lonicera canadensis), smooth sumac (Rhus glabra), dwarf bushhoneysuckle (Diervilla lonicera), and strawberry (Fragaria spp.) (4,7,8).

Bigtooth aspen spans a range of climatic conditions from the marine climate along the Atlantic coast to the continental climate of Minnesota and southwestern Ontario. Summers are humid and moisture is adequate at all seasons (4,7).

Mean annual precipitation ranges from a low of 510 mm (20 in) on the prairie border in Manitoba to a high of 1520 mm. (60 in) in the Maritime Provinces. North to south mean annual precipitation ranges from 510 to 1270 mm (20 to 50 in) with one-half or more occurring during the growing season. Mean annual snowfall exceeds 127 cm (50 in) where bigtooth aspen is most abundant and of best form. Mean annual snowfall exceeds 250 cm (100 in) in the Upper Peninsula of Michigan and the Northeast and reaches a maximum of 300 cm (120 in) in Nova Scotia (7). Areas near Lake Superior in the Upper Peninsula of Michigan often receive more than 500 cm (200 in) of snowfall.

January temperatures average -18° C (0° F) in the North and 2° C (35° F) in the South. Temperatures of -46° C (- 50° F) have been recorded at the northern limit of bigtooth aspen.

Average July temperatures range from 16° C (60° F) in the North to 26° C (78° F) in the South. Temperatures higher than 38° C (100° F) have been recorded throughout its range.

Bigtooth aspen is subject to a number of agents that cause damage and mortality. Fire can easily kill these thin-barked trees or reduce their growth and provide entry points for disease organisms. Hailstorms may defoliate trees and severely scar stems and provide similar entry points. Heavy thinning may subject the residual stems to sunscalding. Windthrow is not a problem but wind breakage is common at cankered and borer-infested portions of the stem.

Hypoxylon canker (Hypoxylon mammatum) is the most serious disease of the aspens. Trees often are girdled or subjected to wind breakage, but bigtooth aspen is much more resistant to Hypoxylon canker than quaking aspen. Heart rot (Phellinus tremulae) can cause serious volume loss and stand deterioration when stands are held beyond rotation age. Ganoderma applanatum and Armillaria mellea can cause extensive root decay. Shepherd's crook (Venturia macularis) may repeatedly kill new terminal growth in young stands (2,4,7,9). Clones vary greatly in resistance to disease attack and damage.

The forest tent caterpillar (Malacosoma disstria) and the large aspen tortrix (Choristoneura conflictana) have periodically defoliated extensive areas of aspen. Populations of these insects usually persist for 2 or 3 years and then suddenly collapse. Growth loss can be substantial but few trees are killed (2,4,7,9).

The poplar borer (Saperda calcarata) is the most serious wood borer in aspen. Extensive boring degrades large trees and subjects stems to wind breakage. Wood borers of several species can provide infection points for Hypoxylon canker and other fungi. In turn, defoliating insects may cause an increase in populations of wood borers (2,4,7,9).

When their populations are high, deer and hare can heavily browse young stands. This is seldom a problem in dense stands, however, because browsing helps thin these stands. Beaver can kill large portions of stands both by flooding and by cutting trees (2,5,9).

Bigtooth aspen is normally dioecious; flowering begins at about age 10. Flowers are borne in drooping catkins, 5 to 7.5 cm (2 to 3 in) long, that are tan-colored at maturity. Bracts have 5 to 7 clefts and capsules are narrow and cone-shaped. Flowering precedes foliation and seed is dispersed before leaves are fully expanded. Female receptivity tends to begin before male pollen shed and lasts longer, but the mean dates of peak receptivity and pollen shed are closely allied. The timing of receptivity or pollen shed varies little intraclonally but varies significantly interclonally, The duration of active flowering is shorter for bigtooth aspen than for quaking aspen (3,4,7,9).

Air temperature seems to be the principal factor affecting the time and duration of flowering. In southern Ontario flowering occurs in late April; in southeastern lower Michigan flowering time is late April to early May; and in northern lower Michigan and northern Minnesota flowers appear in early to mid-May. Dehiscence of the capsule and seed dispersal take place about 4 weeks after flowering. Bigtooth aspen flowers, foliates, and disperses seeds about 10 days later than quaking aspen (3,4,7).

Population Differences Recognizing the inter- and intraspecific clonal variation in aspen stands can lead to definite upgrading of the quality of aspen in growth, form, and disease resistance. In mixed stands of bigtooth aspen and quaking aspen on dry exposed sites, bigtooth aspen clones have superior growth and disease resistance (5,6). The interclonal variation in rootability should be recognized when stands are established from stem and root cuttings.

Hybrids Natural hybrids of bigtooth aspen and quaking aspen do occur, but less frequently than might be expected, because of differences in time of flowering. When hybridization occurs, it is most likely to be between male quaking aspen and female bigtooth aspen (3,4,9).

The best known interspecific hybrid is Populus alba x P. grandidentata (P. x rouleauiana Boivin). Growth is superior to native bigtooth aspen on dry, sandy soils, but its development is maximized on fertile, moist loamy soils. Seed production and suckering are generally low and branchiness and form are poor. P. x canescens x P. grandidentata has shown good growth but poor rootability. P. x canescens x P. alba x P. grandidentata has shown both good growth and good rootability. Additional crosses with bigtooth aspen have been made but are generally of lower quality.

Intraspecific crosses of bigtooth aspen have been difficult to establish in plantings and have slow early growth. Bigtooth aspen has 19 pairs of chromosomes (2n=38).

Normally, mature bigtooth aspen trees are 18 to 24 m (60 to 80 ft) tall and 20 to 25 cm (8 to 10 in) in d.b.h. On the best sites, bigtooth aspen can attain a height of 30 in (100 ft) at 50 to 60 years of age (3,4,5). Height growth is rapid for the first 30 years and slows markedly thereafter. Quaking aspen tends to have slower height growth initially but maintains this growth longer. Stand basal area seldom exceeds 34.4 m²/ha (150 ft²/acre).

Empirical yields for 50-year-old bigtooth aspen in northern lower Michigan range from 100.8 m³/ha (1,440 ft³/acre) on site index 15 in (50 ft) sites to 296.8 m³/ha (4,240 ft³/acre) on site index 24 m (80 ft) sites (table 1) (5). For bigtooth aspen, site index is determined at base age 50 years. Stands begin to deteriorate from rot fungi at 40 to 45 years of age on the poor sites and at 50 to 70 years of age on the better sites. Large single cull trees more than 100 years old are found. Bigtooth aspen appears to be more resistant to disease than quaking aspen.

Site index² and age (yr) Mean height³ Mean d.b.h. Basal area Merchantable volume* m cm m²/ha m³/ha Sl 15 m         30 13.7 13 16.1 28 40 14.6 17 20.4 84 0 50 15.2 18 20.7 100 8 60 15.5 19 19.7 100.8 Sl 18 m         30 16.2 15 20.7 78.4 40 17.7 19 24.6 140 50 18.3 20 24.8 156.8 60 18.6 21 23.2 151.2 Sl 21 m         30 18.9 17 25.3 140 40 20.4 20 29.2 207.2 50 21.3 22 28.2 218.4 60 21.6 23 25.7 207.2 Sl 24 m         30 21.6 19 31.9 224 40 23.5 22 34.9 296 . 8 50 24.4 25 32.1 296.8 60 24.7 27 28.9 274.4    ft  in ft²/acre  ft³/acre  Sl 50 ft         30 45 5.1 70 400 40 48 6.6 89 1,200 50 50 7.1 90 1,440 60 51 7.3 86 1,440 Sl 60 ft         30 53 5.9 90 1,120 40 58 7.3 107 2,000 50 60 8 108 2,240 60 61 8.2 101 2,160 Sl 70 ft         30 62 6.6 110 2,000 40 67 8 127 2,960 50 70 8.8 123 3,120 60 71 9.2 112 2,960 Sl 80 ft         30 71 7.4 139 3,200 40 77 8.8 152 4,240 50 80 9.8 140 4,240 60 81 10.5 126 3,920 ¹All trees 1.5 cm(0.6 in) and larger in d.b.h.
²Height of dominants and codominants at 50 years.
³Dominants and codominants
*Gross inside bark volume to a 10 cm (4.0 in) diameter inside bark.

Bigtooth aspen is classed as very intolerant of shade. It cannot successfully reproduce under its own shade (3,7), and seedlings must be kept free of competing brush and grasses. However, sucker growth is rapid enough to outgrow its competition. Leaving as little as 5.7 to 8.0 m²/ha (25 to 35 ft²/acre) basal area in the residual overstory can severely limit sucker initiation and growth. Severing all stems 5.0 cm (2.0 in) and larger is recommended for producing well-stocked vigorous sucker stands (5).

Mortality is very high in young sucker stands, but this acts as a natural thinning agent. Trees begin to express dominance at 7 to 10 years, and potential crop trees can often be identified by age 10. Trees die throughout the life of the stand until 620 to 1,235 stems per hectare (250 to 500/acre) remain at the end of the rotation.

Bigtooth aspen responds well to thinning for producing small saw-log and veneer material. Only well-formed, disease-resistant clones on site index 21 in (70 ft) or better areas should be considered for producing sawtimber and veneer (5).

Clearcutting is the best method for harvesting stands because the completeness of the overstory removal determines the establishment and vigor of the new stand. Rotation lengths are 30 to 40 years on the poorest sites, and 50 to 60 years on the best sites because stands deteriorate rapidly when held to greater ages. With proper harvesting and site preparation bigtooth aspen can continually occupy a site. Otherwise, it will be succeeded by the more shade-tolerant hardwood and coniferous species (3).

Suckers remain connected to parent roots even after they develop their own root system. Adventitious roots develop at the basal part of the sucker or on the parent root near the sucker base. Cordlike root connections between the sucker and parent root remain alive until one of the two trees dies (4).

Bigtooth aspen's root system is shallow and wide spreading. Strong, vertical, and penetrating roots near the base of the tree, and sinker roots developing from the lateral roots, provide good anchorage. Four to five well-developed lateral roots originate from the base of the tree and branch within 0.6 in (2 ft). The lateral spread of roots is usually 10 to 20 in (33 to 66 ft) under forested conditions. Bigtooth aspen's root system tends to be deeper, to be less branched, and to have fewer adventitious roots than quaking aspen's root system (4,9).

Seeds are pear-shaped, with a tuft of long silky hair attached to the narrow end. Good seed crops are produced every 2 or 3 years, but light seed crops are produced annually. Seeds are very light averaging approximately 5.6 million/kg (2.54 million/lb) with hair and are dispersed by wind for long distances from the parent tree (4). A single tree may produce more than 1.5 million seeds (3).

Seedlings do not commonly occur in nature, in spite of extremely high production and high seed viability (more than 80 percent germination under laboratory conditions) (3,4). The uncommon occurrence has various causes: competition from other plants, short seed viability (2 or 3 weeks), the presence of a germination and growth inhibitor in the seed hairs, lack of moisture, high seedbed temperatures, susceptibility to fungal attack, and the chemical nature of some soils.

Germination is epigeal. Bare, moist soil is essentially for seed germination and seedling establishment. If ground moisture is adequate, seeds usually germinate in 1 to 2 days. When the seed coat is ready to rupture, a typical time table for seedling development is as follows (4):

24 h Radical emerges from seed and contacts soil; fine hairs develop at junction of radical and hypocotyl.
48 h Hypocotyl elongates and raises cotyledons above ground.
144 h Cotyledons expand and shed testa; radical penetrates soil about 10 mm (0.4 in).
1 yr Seedling is 15 to 20 em (6 to 8 in) tall; root spread is about 15 to 25 cm (6 to 10 in) deep and as much as 40 em (16 in) wide.
2 yr Seedling is 30 to 60 cm (12 to 24 in) tall.
3 yr Seedling is 90 to 120 cm (36 to 48 in) tall.

Abundant moisture can greatly increase the first year's height growth, but competition from brush and weeds can easily eliminate 1-year-old seedlings.

Bigtooth aspen is capable of growing on a wide range of sites but is far less adaptable than quaking aspen (Populus tremuloides). It is most abundant on sands, loamy sands, and light sandy loams, but it is found as a single tree or minor stand component on any soil, from rock outcrops to heavy clays. Bigtooth aspen develops best on moist, fertile sandy uplands where the depth to water table is no more than 1.5 m (5 ft), and site quality decreases rapidly as the depth to water table approaches 0.6 rn (2 ft). Within this zone, a stagnant water table is much more detrimental than the lateral movement of water. Stands generally are unmerchantable if located on soils with an impermeable stratum at 0.3 rn (I ft) or less or a permeable subsoil that is dry to 1.5 m (5 ft) in the summer. Good soil aeration is essential for good growth of bigtooth aspen (3,4,5,7). Soils on which bigtooth aspen most commonly grow are in the orders Spodosols, Alfisols, and Inceptisols.

Although bigtooth aspen can grow at sea level and has been found at altitudes over 915 m (3,000 ft) in North Carolina, it is most abundant and develops best on flat to gently rolling terrain of floodplains or lower slopes of the uplands between 150 to 610 m (500 to 2,000 ft) in altitude.

Typical management of aspen stands does not distinguish between bigtooth aspen and quaking aspen, and their uses are not differentiated. The aspen forests contribute significantly to maintaining other resources. It is no accident that the native range of ruffed grouse coincides with the native range of the aspens. Aspen leaves and staminate flower buds provide ruffed grouse with their most important yearlong food resource. Aspen suckers are a favored winter food of moose and are heavily browsed by white-tailed deer. Although aspen is not the most palatable browse, an abundance and wide distribution of small clearcuttings are essential for maintaining a good deer population. The bark, leaves, twigs, and branches of aspen are preferred by beaver (2,9).

Because aspen is deciduous, more snow accumulates on the ground in aspen than in coniferous stands. Thus, soils are better insulated from freezing and snowmelt enters the soil rather than running overland. Because of aspen's ability to produce abundant suckers, fire-killed stands are rapidly revegetated. Similarly, aspen can be harvested on slopes without seriously affecting erosion or water quality. Aspen often is perpetuated on areas where soil stabilization poses a problem (2).

Aspen bark has been pelletized for supplemental cattle feed and fuel. Although the vast quantity of these pellets comes from quaking aspens bark, no distinction has been made between bigtooth aspen and quaking aspen in the pelletizing process.

Suckering is the most common mode of reproduction. Suckers usually develop from shallow, cordlike lateral roots. These roots range from 0.5 to 11.4 cm. (0.2 to 4.5 in) in diameter with the greatest proportion of suckers on roots less than 2.5 cm (1.0 in) in diameter. Sucker-bearing roots lie about 7.5 cm (3.0 in) deep in the mineral soil but can be as deep as 17.8 cm. (7.0 in) (4). Sucker-bearing roots tend to be deeper for bigtooth aspen than for quaking aspen. Sprouts from stump and root collar are rare but develop more frequently in bigtooth than quaking aspen (9).

Sucker initiation is attributed to an increase in soil temperature and relief from the apical dominance effect (3,4). Almost any disturbance-tree cutting, brush removal, fire, or ground scarification-can result in some degree of suckering (2,3,5). Existing stands continually produce suckers but most of them are weak and die within a few years (4,7).

Vegetative reproduction results in the formation of male and female clones that range from a few to several trees and occupy from 0.004 to 1.5 ha (0.01 to 3.8 acres) (3,4).

Suckering ability varies significantly interclonally but no relation exists between size of clone and suckering ability. A single clone tends to exclude the invasion of other clones on a particular area, but the intermixing of "clone territories" to form a stand is common. In mixed stands of bigtooth aspen clones and quaking aspen clones, the clonal boundaries between the two species are well defined; the clonal boundaries within species are less distinct (1,3,4,9).

After a stand is logged or killed by fire, suckering normally produces from 8,000 to 60,000 stems per hectare (3,200 to 24,000/acre). Age of parent stand, residual overstory, season of cutting, intensity of fire, and amount of ground scarification affect the abundance and vigor of suckers (3,4,5,9). Suckers have been produced more than 30 in (100 ft) from the parent tree when invading open fields (2), but 10 m (33 ft) is a more likely maximum within a stand (6). Because of the existing root system, suckers grow faster than seedlings and often reach 0.9 to 1.8 in (3 to 6 ft) in height the first year.

Reproducing bigtooth aspen from stem cuttings is difficult. However, rootability can be improved if the cuttings have expanding foliar buds or are treated with indolebutyric acid (4,7). Root cuttings have a good capacity to produce suckers. Interclonal variation in rootability of cutting is large.

Salicaceae -- Willow family

Paul R. Laidly

Bigtooth aspen (Populus grandidentata), also called largetooth aspen, poplar, or popple, is medium-sized deciduous hardwood tree of north eastern North America. It is short lived but grow rapidly, especially the first 30 years, on sandy upland soils and flood plains. Easily reproduced from seed or sucker shoots, it quickly reforests disturbed site where it builds soil and protects seedlings of slower growing species. The soft, light-colored wood is us& mostly for paper pulp. Wildlife use the foliage, twigs and buds as food.

Bigtooth aspen is native to northeastern and north-central United States and southeastern Canada. Its range extends from Cape Breton Island Nova Scotia, west to southeastern Manitoba, south through Minnesota and Iowa to extreme northeastern Missouri, and east to southern Illinois, Kentucky, Virginia, and Delaware. It is also found locally in western North Carolina and northwestern Tennessee. In Canada, the greatest abundance of bigtooth aspen is in southwestern Quebec and southeastern Ontario (4).


-The native range of bigtooth aspen.

Populus grandidentata, commonly called large-tooth aspen, big-tooth aspen, American aspen, Canadian poplar, or white poplar, is a deciduous tree native to eastern North America.