Populus tremuloides

Quaking Aspen

Quaking Aspen
Photo courtesy Wisconsin State Herbarium
and Kenneth J. Sytsma

Flora, fauna, earth, and sky...
The natural history of the northwoods

Name:
  • Populus, from the Latin for poplar
  • tremuloides, from the Latin, tremulus, "shaking, trembling, quivering"
  • Common Name, from the movement of the leaves in the wind
  • Other common names include Trembling Aspen, Peuplier faux-tremble (Qué), Asp (Swe), Ösp (Is), Critheann (Gaelic), Amerikanische Espe (Ger)

Taxonomy:
  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Magnoliopsida, the Dicotyledons
      • Subclass Dilleniidae
        • Order Salicales
          • Family Salicaceae, the Willows, with aspen and poplars
            • Genus Populus, the Poplars
  • Taxonomic Serial Number: 195773
  • Also known as Populus aurea, Populus cercidiphylla, Populus tremula ssp. tremuloides, Populus vancouveriana
  • Readily hybridizes with Bigtooth Aspen (Populus grandidentata), European Aspen (Populus tremula), White Poplar (Populus alba), Curly Poplar (Populus canescens), Narrowleaf Cottonwood (Populus angustifolia), Balsam Poplar (Populus balsamifera), Eastern Cottonwood (Populus deltoides).

Description:
  • A native, upright, deciduous tree from 20'-100'
  • Leaves simple, alternate, and heart-shaped to nearly round, 1"-3" long; dark green and shiny above, pale green below, with small, rounded teeth on the margins. Leaf stem flattened. Noted for its brilliant fall colors, leaves turn bright yellow, yellow-orange, gold, or reddish after the first frosts.
  • Stem
    • Trunk straight, 4"-36" in diameter.
    • Branches generally spreading, forming a rounded crown.
    • Twigs smooth, slender; reddish-brown often with a gray waxy film; becoming grayish-brown to grayish-orange by the third year of growth. Many, but not all, are self-pruning, with numerous small twigs dropping in the fall, ridding the tree of excess foliage and returning nutrients to the soil.
    • Buds conical, reddish-brown; terminal bud ¼" long, often slightly resinous.
    • Bark typically smooth, creamy yellowish-white to very light green, becoming furrowed with age, 1"-2" thick on older trees.
  • Root system extensive, and may encompass large areas, even when aboveground vegetation is relatively sparse. Lateral roots may extend more than 100' into adjacent open areas. Lateral roots occur in the top 2'-3' of soil where vertical sinker roots may extend to depths of 5' or more.
  • Flowers dioecious, male and female 1"-3" hanging catkins.
  • Fruit two-valved, light green to brown capsules.
  • Seeds light, pear-shaped, and tufted with a long silky seed hair for efficient wind dispersal.

Identification:
  • Identifiable as an Aspen by its characteristic aspen leaf.
  • Distinguished from Bigtooth Aspen (Populus grandidentata) by having slightly smaller leaves with finely toothed leaf edges. Bigtooth Aspen has larger leaves with large irregular teeth on the leaf edges.
  • Field Marks

Distribution:
  • Alaska to Newfoundland, south to Minnesota, Iowa, Illinois, Indiana, Ohio, Pennsylvania, and New Jersey in the East; south throughout the western states to the mountains of northern Mexico.
  • The most widely distributed tree in North America.

Habitat:
  • Disease: With thin, soft, living bark, is susceptible to a wide range of diseases and insect infestations.
    • Rot-producing fungi enter through wounds and are most common in overmature stands. Some diseases such as Shoestring Root (Armillaria) spread through the interconnected root system. Common stem and root rots include Aspen Trunk Rot (Phellinus tremulae), Peniophora polygonia, White Mottled Rot (Ganoderma applanatum), Shoestring Root Disease (Armillaria mellea), and Flammulina velutipes.
    • Cankers often affect aspen and a few are capable of causing significant mortality. Black Canker (Ceratocystis fimbriata) is widely distributed but rarely kills the trees. Sooty Bark Canker (Cenangium singulare) however, is one of the most serious causes of mortality; mortality caused by Hypoxylon Canker (Hypoxylon mammatum) also reported.
  • Insects: Poplar Borer, Western Tent Caterpillar, leaf rollers, Leaf Miner Beetle, Roundheaded and Flathead Woodborer, all attack Aspen
  • Occurs as a dominant, often in pure stands, or as scattered individuals in communities dominated by other trees with spruce (Picea spp.), pine (Pinus spp.), and birch (Betula spp.).
  • Tolerant of cold, but not of high temperatures.
  • Soils from shallow and rocky, to deep, heavy clays, including: infertile dry sands, rich loams, waterlogged mineral soils and peats. Growth generally best on rich, moist, loams, or on well-drained silt or clay loams with an abundant supply of calcium.
  • Leaves decay relatively rapidly, returning nutrients to the soil. A characteristic "aspen soil" develops on sites which have supported aspen for a number of generations, with a pH generally higher than on soils where conifers dominate.
  • More rapid growth generally occurs on these soils where the water table is 18"-60" deep. A higher water table may be detrimental to growth.
  • Extremely intolerant of shade; nearly full sunlight is necessary for good growth and survival. More intolerant of shade than any other important tree in the Lake States.
  • A succession species which is replaced by a variety of conifers or hardwoods. On dry sites most often replaced by Red Pine (Pinus resinosa), Red Maple (Acer rubrum), or Oaks (Quercus spp.). Replaced by White Pine (Pinus strobus) on moist sites, and by Balsam Fir (Abies balsamea), Black Spruce (Picea mariana), Black Ash (Fraxinus nigra), or White Cedar (Thuja occidentalis) on wetter sites. A variety of northern hardwoods, White Spruce (Picea glauca), or Balsam Fir (Abies balsamea), are climax species on many of the most fertile aspen sites in the Lake States. Soil moisture and fertility greatly influence the rate of succession, most rapid on better sites, and where associated species are aggressive, shade-tolerant, and fast-growing.

Fire:
  • Highly competitive on burned sites. Even where a minor component of prefire vegetation, it often dominates a site after fire. Quaking aspen has adapted to fire in the following ways.
  • 1. The thin bark has little heat resistance, and quaking aspen is easily top-killed by fire.
  • 2. Root systems of top-killed stems send up a profusion of sprouts for several years after fire.
  • 3. Sprouts grow rapidly by extracting water, nutrients, and photosynthate from an extant root system, and may outcompete other woody vegetation.
  • 4. Following a fire, a new, even-aged quaking aspen stand can develop within a decade.
  • 5. In contrast to most trees, quaking aspen is self-thinning. Without intervention, a mature forest of healthy trees can develop from dense sprouts.
  • Fire releases sprout primorida on roots from hormonally controlled growth inhibition; removes canopy shade; and blackens the soil surface, increasing heat absorption. Increased soil temperatures aid sprout production. On cold sites, quaking aspen may be unable to sprout until soil temperatures rise after fire.
  • Fuels are usually more moist in quaking aspen stands than in surrounding forest. Crown fires in coniferous forests often drop to the surface in quaking aspen, or may extinguish after burning into quaking aspen only a few meters. Quaking aspen stands often act as natural fuelbreaks during wildfires, and fires sometimes bypass quaking aspen stands surrounded by conifers.
  • Small-diameter quaking aspen is usually top-killed by low-severity surface fire.As dbh increases beyond 6 inches (15 cm), quaking aspen becomes increasingly resistant to fire mortality. Large quaking aspen may survive low-severity surface fire, but usually shows fire damage. Moderate-severity surface fire top-kills most quaking aspen, although large-stemmed trees may survive. Some charred stems that survived low- or moderate-severity fire initially have been observed to die within 3 or 4 postfire years. Severe fire top-kills quaking aspen of all size classes.
  • Moderate-severity fire does not damage quaking aspen roots insulated by soil. Severe fire may kill roots near the soil surface or damage meristematic tissue on shallow roots so that they cannot sprout. Deeper roots are not damaged by severe fire and retain the ability to sucker.
  • Mortality does not always occur immediatedly after fire. Sometimes buds in the crown will survive and leaf out prior to the death of the tree. Even when quaking aspen is not killed outright by fire, the bole may be sufficiently damaged to permit the entrance of wood-rotting fungi. Basal scars which lead to destructive heart rot can be made on even good-sized aspen by "the lightest of fires." Basal fire scars may also permit entry of borers and other insects which can further weaken the tree.
  • The position of an individual tree on a slope, or within a stand, can influence the degree of damage caused by fire. Even when damaged, trees located near the boundaries of a fire can often maintain a live crown. These peripheral trees may receive food supplies from the roots of unburned neighbors.
  • Quaking aspen sprouts from the roots and establishes from off-site, wind-blown seed after fire. It is the classic soboliferous species described by Stickney [157]: a plant that sprouts from carbohydrate-storing lateral roots (sobols).
  • Sprouting: Quaking aspen generally sprouts vigorously after fire. Long-term growth and survival of quaking aspen sprouts depend on a variety of factors including prefire carbohydrate levels in roots, sprouting ability of the clone(s), fire severity, and season of fire. Moderate-severity fire generally results in dense sprouting. Fewer sprouts may be produced after severe fire. Since quaking aspen is self-thinning, however, sprouting densities are generally similar several years after moderate and severe fire. A low-severity surface fire may leave standing live trees that locally supress sprouting, resulting in an uneven-aged stand.
  • Fire exposes mineral soil, which is an excellent seedbed for quaking aspen.

Associates:

History:
  • During the last Ice Age, a part of the vast White Spruce forest which covered the Great Plains and eastern US, just south of the windswept tundra bordering the great ice sheets. One of the earliest species, along with spruce, to follow the retreating ice northward, reaching the Canadian border soon after the ice had passed.
  • Of commercial value in the United States since the 1890's.

Uses:
  • Wood much softer and lighter than most North American hardwoods; light in color, fairly straight-grained, of a fine, uniform texture, odorless and tasteless.
  • Resistant to splitting when nailed, accepts glue and paint well, and largely free of resinous extractives and slivers. Also of relatively low strength, only moderately shock resistant, warps readily, and susceptible to decay.
  • Used most commonly in pulp products such as book and specialty papers, newsprint, insulation board, chipboard, fiberboard, and particleboard, and is a preferred species for the manufacture of structural flakeboard. Well-suited for furniture parts, interior trim, crates, pallets, lumber core stock, and paneling. Formerly used widely for posts, poles, bridge planks, and mine timbers.
  • Also used in a variety of miscellaneous products including excelsior, animal bedding, matchsticks, toys, beehives, tongue depressors, spoons, and ice cream sticks.
  • In the past, demand for aspen was fairly low. However, the commerical value of this species has been increasing in recent years.

Reproduction:
  • Clonal species capable of producing numerous individual, but genetically identical stems from a single plant. The area of a clone may be quite large, most stands representing a mosaic of individual clones.
  • Roots able to sucker and produce new stems after fire or other disturbance.
    • Rapidly growing but relatively short-lived, in many parts of Minnesota, reaching 80' in first four decades. Deterioration typically begins by age 60 in the Lake States; as early as 35 to 45 years in some stands.
    • Although individual stems are relatively short-lived, clones are not, and may survive for hundreds or even thousands of years. (Most existing clones in the Great Basin are at least 8,000 years old. It is suggested that a very few clones may have originated in the Pliocene and survived 1,000,000 years or more by suckering!)
  • Vegetative regeneration primarily through suckering, although sprouting from root collars and stumps also occurs, providing aspen with a mechanism to survive and reproduce, even in harsh and unfavorable environments. Most suckers develop in fairly close proximity to the parent stem, the majority within 25', although some 80'-100' or more.
  • Dioecious species, generally produces an abundance of viable seed. However, the extemely restrictive conditions necessary for germination and establishment have virtually elimated sexual reproduction over much of its range, especially in the West. Reproduction through seed is more common in the boreal forest.
  • Sexual reproduction, where conditions favorable for germination and establishment prevail, can add greater genetic diversity and allow for wider dispersal than can vegetative regeneration. Aspen first flowers at approximately 10 to 20 years of age. Flowers are wind-pollinated, and evidence suggests greater abundance of male plants in natural populations. Although seed production is variable, at least some viable seed is produced annually. Large seed crops occur at 2 to 3, or 4 to 5 year intervals. An average mature tree can produce approximately 1.6 million seeds annually, shed from early May through mid-June. In many areas, seed production apparently peaks at 50 years of age.
  • SeedsMay be carried more than 1,600' under typical prevailing winds, or up to several miles with high winds. Somewhat resistant to water damage, and can be dispersed by water in wet habitats.
  • Seed viability relatively short under natural conditions, although the viability of fresh seed is usually greater than 90% soon after dispersal. Seed dried for 3 days before storage at cool temperatures retains good viability when stored for 1 1/2 years.
  • Germination and establishment require a continous supply of moisture, a favorable substrate such as exposed mineral soil, and suitable temperatures. Germination and subsequent growth may be limited by high emperatures, growth inhibitors present in the "seed hair," drought, disease, insects, heavy rains, extreme temperature fluctuations, or unfavorable soil chemistry. Germination generally begins within a few hours to a few days after moisture is received and can occur across a broad temperature range (32-98 degrees F). However, optimal germination temperatures from 59-77 degrees F. A very shallow depth of burial on exposed mineral soil apparently provides the best environment for germination. Burned or scarified sites often provide excellent seedbeds.

Propagation:
  • By seed

Cultivation:
  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Highly valued for its esthetic qualities, particularly during the fall when leaves turn briliant colors. It has been widely used in landscaping. Aspen provides good noise abatement and visual screening

Links:

Comments:

Valley Internet Company
Return to Home Page
Send Feedback to Webmaster


Last updated on 4 March, 2006