(quaking aspen)Select an option below for more information on this species
Quaking aspen is a deciduous tree species in the willow family (Salicaceae) that becomes established early in succession in plant communities on south-facing slopes, river terraces, and burned areas in the boreal belt. Growing clonally from roots, one genetic individual can dominate an entire hillside. Trees grow 6-12 m tall. The bark is smooth, yellow-green, with dark branch scars. Quaking aspen has chlorophyll in its bark, allowing it to begin photosynthesis prior to bud burst.
The small leaves (3-5 cm long) are light green with white veins, turning yellow in the fall, lighter in color below than above. Leaf shape is round-ovate with serrate margins and a short pointed tip. The flat petiole is caught by the slightest wind, causing the leaves to 'quake' or 'tremble', the source of both scientific and common names. The twigs are thin and reddish, maturing to gray, with many leaf scars. The small winter buds are 6 mm long, long-pointed, and shiny red-brown.
The species is dioecieous, with wind-pollinated male and female flowers borne on separate trees. Both kinds of flowers have reduced morphology (no petals or sepals), and the 4-6.5 cm long catkins are covered in long gray hairs. Male plants have catkins with many staminate flowers, 6-12 red stamens per flower. Female catkins have many small flowers, each having round discs beneath two fused carpels and narrow stigmas. The conic capsules mature from green to brown and dehisce along two seams. Each capsule release 5-7 tiny seeds attached to long silky hair to aid their dispersal via wind.
Quaking aspen can potentially be confused with Alaska birch (Betula neoalaskana) and balsam poplar (Populus balsamifera). Alaska birch has white, papery bark, and serrate leaf margins. Balsam poplar has larger, longer leaves that are glossy green and have a pungent smell. Quaking aspen is the only tree in central Alaska with flat petioles.
In central Alaska, aspens have been recently hard-hit by aspen leaf miners ( Phyllocnistis populiella). The larva of the moth eats through the top and bottom cell layers of aspen leaves, dramatically reducing the photosynthetic capabilities of the leaf and changing the leaf color from green to silver. High levels of seed produced in 2004 may have been induced due to the stress of the leaf miner outbreak (Rozell 2005).
Other insects that utilize P. tremuloides include, but are not limited to: leaf rollers Epinotia solandriana, large aspen tortrix (Choristoneura conflictiana), leaf beetles ( Chrysomela spp., and Eriophyid mites (Holsten et al. 2001).
There are a variety of fungal pathogens of P. tremuloides such as: shepard's crook disease (Venturia macularis, cankers (Encoelia pruinosa, and Cryptosphaeria populina, and Armillaria root rot (Armillaria spp.) (Holsten et al. 2001).
The wood is occasionally used for firewood or lumber, but is not considered choice. The Dena'ina used the inner bark to treat coughs and colds (Garibaldi 1999).
Quaking aspen is endemic to North America where it is perhaps the most widely distributed tree species. Alaska lies at the northernmost edge of its range, which covers eastern Canada and the northeastern United States, and scattered localities through all the western states, south to central Mexico. Within Alaska, quaking aspen reaches the southern foothills of the Brooks Range, and is found in uplands of interior Alaska and Southcentral. In Denali, quaking aspen occurs north of the Alaska range crest usually in south-exposed terrain and river terraces, particularly common in recently-burned sites.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
Quaking aspen is found on south slopes and in open, mixed deciduous-conifer forests on low elevation benches. Almost never found below 300 m, this species is most abundant at 300-500 m, with a few trees found at up to 1053 m. Degree of slope is not strongly correlated to the frequency of quaking aspen, though is slightly more common on steep slopes (>28 degrees). Above 28 degree slopes are the only places where this species reaches a high level of cover, in some cases forming dominant stands. This is correlated to its life history trait of disturbance tolerance; on steep slopes, soil and water movement can prevent slower-growing trees from establishing. Additionally, no matter the level of incline, quaking aspen is significantly more likely to be found on southern aspects.
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.