BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Populus balsamifera ssp. balsamifera | Balsam Poplar 



GENERAL BOTANICAL CHARACTERISTICS : 
Balsam poplar is a medium to large native deciduous tree.  Heights of
mature trees range from 30 to 100 feet (9-30 m) and trunk diameters from
4 inches to 2 feet (10-60 cm) [101].  The trunk of balsam poplar is
straight and cylindrical with an open crown of a few stout ascending
branches [63].  The bark is smooth and light gray to grayish brown but
furrows with age [22].

Winter buds are 1 inch long (2.5 cm) with sticky resin and a pungent
balsam odor in the spring [101].  Drooping pistillate and staminate
catkins occur on separate trees.  Leaves are ovate or broadly
lanceolate, 2.25 to 4.5 inches long (6-11 cm) and 1.5 to 3 inches wide
(4-7.5 cm) [101].  Leaves are shiny green above and pale green below
with finely toothed margins [22].

Roots are shallow, especially on wet soil types or shallow permafrost
[36].  


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


REGENERATION PROCESSES : 
Balsam poplar reproduces both sexually and vegetatively.

Seed production and dispersal:  Balsam poplar flower production begins
at about 8 years of age, with a good seed crop produced every year [36].
Most seeds are wind dispersed and fall within 650 feet (200 m) of the
parent tree [36].  Seeds remain viable for 2 to 4 weeks [57,63] but will
germinate immediately following arrival on a suitable seedbed of
exposed, moist mineral soil [57].  A 98 to 100 percent germination rate
was obtained in 2 to 3 days at temperatures ranging from 41 to 77
degrees F (5-25 degrees C) in a greenhouse study [110].  Seedlings
require 1 month of abundant moisture to survive [36].

Vegetative reproduction:  Balsam poplar is capable of regenerating from
root suckers, stump sprouts, stem sprouts, and buried branches [36,57].
Root suckering is thought to be primarily a means of expansion rather
than a means of recovery following clearcutting or fire [57].  Once
established on more mesic sites, balsam poplar will expand onto drier,
sandier sites adjacent to river floodplains through vegetative expansion
[57].  Most root suckers grow from roots about 0.4 inches (1 cm) in
diameter within the top 0.8 inches (2 cm) of soil [36].  Suckering is
most common when the organic layer has been removed, exposing mineral
soil [36].  Root suckering activity may increase when soil is disturbed
or when the overstory is removed, thus allowing warmer soil temperatures
[36].  Balsam poplar suckers are larger than those of eastern and
narrowleaf cottonwood and are more vigorous than aspen suckers [88].

Cut stumps produce sprouts from callus tissue and from dormant buds
[36].  Branches must be well buried to produce aerial shoots [36].  Stem
sprouting effectively aids recovery after destructive flooding in which
the main stem is broken or bent over [57].  Plant fragments washed
downstream may be a means of colonization for balsam poplar [57].  In
such cases sprouts can form on either root or shoot segments, leading to
the formation of new roots and establishment of a new plant.

Stands of balsam poplar are often polyclonal, with several genotypes and
their sprouts making up a stand [41].


SITE CHARACTERISTICS : 
Balsam poplar generally occurs on moist sites, such as river
floodplains, stream and lake shores, moist depressions, and swamps, but
will also grow on drier sites [9,22,63,111].  It commonly grows in moist
forests, such as white and black spruce (Picea mariana) forests of the
boreal zone, and is found in the forest-tundra transition zone in Canada
[63,68].  Balsam poplar can be found growing beyond the coniferous tree
line along rivers and on southern slopes having less permafrost than the
surroundings [63,97].

Common associated species of balsam poplar include the following:

Canada and Alaska: white spruce, black spruce, blue spruce (Picea
pungens), lodgepole pine (Pinus contorta), jack pine (P. banksiana),
subalpine fir (Abies lasiocarpa), tamarack (Larix laricina), black
cottonwood, paper birch, aspen, alders (Alnus spp.), willows (Salix
spp.), currant, (Ribes spp.), red-osier dogwood (Cornus sericea), and
prickly rose (Rosa acicularis) [16,19,36,55,56,63,74,77,80,99].

Minnesota:  balsam fir (Abies balsamea), black ash (Fraxinus nigra),
American elm (Ulmus americana), red maple (Acer rubrum), aspen, and
bitter cherry (Prunus emarginata) [14].

Glacial moraines in the northern boreal forest commonly support stands
of balsam poplars.  Permafrost may occur discontinuously in these areas
[66].  Typical soils where balsam poplar is found are those of alluvial
floodplains, including gravel, deep sand, clay loam, silt, and silty
loam [24,36].  Abundant soil moisture is needed, but stagnant brackish
water is intolerable to this tree [36].  Balsam poplar has high nutrient
requirements; it needs a good supply of calcium and magnesium.  It does
not tolerate acidic deep peats and humic soils in which nutrients are
released slowly [36].

Climates in which balsam poplars grow range from arctic to temperate
but most commonly are boreal.  Average temperatures in British Columbia
boreal forests are below 26 degrees F (-3 degrees C) in the coolest
month and around 50 degrees F (10 degrees C) in the warmest month [36].
Mean annual precipitation is 177 inches (452 cm); about one-third is in
the form of snow [65].

Elevational ranges for balsam poplar are reported as follows:

                        feet          meters      reference

Alaska               0 -  3500        0 - 1067     [101]
British Columbia     0 -  5400        0 - 1650     [36]
Colorado          6000 - 12000     1800 - 3700     [24]
Wyoming           3500 -  9000     1067 - 2740     [24]
Montana                   5500            1675     [24]
Utah                      4300            1310     [24]



SUCCESSIONAL STATUS : 
Balsam poplar is a pioneer species which invades disturbed wet sites by
seeding or suckering [22].  It is among the fastest growing trees in
temperate latitudes [22,101].  Rapid early growth allows it to establish
and dominate for up to 100 years; it has lived up to 200 years in Alaska
[36,75] but is considered more short-lived in southern areas.

Balsam poplar is highly flood tolerant [36] and is able to form
adventitious roots within a few days of a flood [58].  It showed no
noticeable injury from 2 months of flooding in several different areas
of Minnesota [1].  Balsam poplar is a seral species, eventually shaded
out by other hardwoods or by conifers [14,22].  In Minnesota it is
commonly found in transition zones between prairie and conifer forest
[14], and it is found in the transition zone between boreal forest and
tundra in far northern latitudes [63].

Balsam poplar occurs on both dry and wet sites, with different factors
controlling succession on these different sites.  Dry sites such as
south slopes or coarse alluvium supporting balsam poplar are affected to
a great degree by fire [75,96,97].  Fire is a major factor controlling
succession in northern montane boreal forests [78].  Repeated wildfires
have led to the development of balsam poplar- and aspen-dominated stands
within white spruce forests [78] and retards white spruce replacement
[63].  Fire will stimulate balsam poplar to root sucker and increase in
density where it is present in any succcessional stage [36].  This tree
has an explosive recovery rate after even severe fires [53].

Fire is uncommon [40,77] and plays no apparent role in succession of
alluvial floodplain sites in boreal forests [75].  Flood or other soil
disturbances allow colonization by willows, alders, and balsam poplars,
with balsam poplar eventually overtopping the other species and
dominating for up to 100 years [10,76,99].  Eventually white spruce
overtops the poplar and matures as an even-aged white spruce forest.
Conversion from balsam poplar to white spruce usually occurs within 120
to 150 years unless an inadequate white spruce seed source exists or
severe flooding recurs [97].  These white spruce stands eventually
become uneven-aged and permafrost may develop due to a lack of sunlight
penetrating through to the soil.  Permafrost development will lead to
replacement by black spruce and tamarack.  Balsam poplar is occasionally
reported to occur in black spruce forests [17,48,49] but does not
persist.


SEASONAL DEVELOPMENT : 
Balsam poplar flowers bloom and seeds disperse before leaves completely
emerge [36,101].  Bloom and seed dispersal dates in several geographic
areas are as follows:

                         flowers bloom    seeds disperse

Alaska [57,101]           May-June          June         

British Columbia [36]     April-June        May-June     

CO, MT, ND [24]           April-May

Lake States, Maine &      April-May         May-July
  Nebraska [32]

Related categories for Species: Populus balsamifera ssp. balsamifera | Balsam Poplar