Quaking & Bigtooth Aspen
Seeing the Forest Through its Trees - Part XII
By Larry Ely
The two species of aspen found in our region, as well as paper birch, are all pioneer species that require full sun and grow on natural or man-made disturbed sites and may appear together at the same site. Open harvested areas and abandoned fields invite all three species and all grow rapidly. Aspen can grow as much as 2- to 4-feet annually after becoming established, especially when sprouting from root suckers. This fast growth provides these pioneers an early advantage over competing shade tolerant species that might eventually occupy the site.
Local loggers often call both aspen species “popple” as they are part of the Populous family that includes poplar. Quaking aspen (Populous tremuloides) and bigtooth aspen (Populous grandidentata) have a close genetic makeup and can crossbreed and hybridize, though their flowering times differ. Though it is often difficult to distinguish between the two because of their similarities, identification can be made by comparing leaves. Quaking aspen has smaller 1.5- to 3-inch oval or slightly heart shaped leaves with finely rounded teeth while bigtooth aspen’s leaves are more egg shaped and slightly larger at 3- to 4-inches. The coarse “teeth” of bigtooth aspen are also more widely spaced. Both have a short, pointed tip with leaves attached by flat stems that allow them to tremble in the wind.
While both aspen species spread via tiny wind-borne seeds, they are more likely to propagate via spreading roots that produce large clonal colonies. Clonal colonies are genetically identical trees connected by a single root system and started from a single seed. While individual aspen trees seldom live to 100 years, newer individuals can continue sprouting from the clonal roots and a stand can persist for hundreds of years.
A 106-acre colony of quaking aspen in Utah is estimated to be many thousands of years old and weighing 13 million pounds. Quaking aspen is more aggressive in its root sprouting while bigtooth is less prolific, resulting in its smaller clonal stands. Bigtooth aspen also favors richer sandy upland soils and is more shade tolerant and more likely to be found as individual trees or small clumps in a mature upland forest.
From a distance, a stand of paper birch and aspen appear similar, but up close the white peeling bark of birch with its paper-like curls easily distinguishes it from the smooth greenish or olive-green bark of the aspen. Aspen trunks also become blackened at their base as they mature and branches appear more erect, reaching to the sky unlike the drooping branches of paper birch.
Aspen fully reach maturity at 20 to 30 years and might persist another 70 or more years, attaining a height of 75 feet and 16-inch diameter. It is important to a variety of wildlife by providing critical feeding and nesting opportunities for ruffed grouse, woodcock, and warblers. It is also a favored food of beavers and provides critical winter browse for moose and deer.
Foresters manage aspen primarily for wildlife habitat as the wood is not valued as firewood in the northeast due to its low heat output and is mostly used in pulp production. Habitat improvements at the Mahoosuc Land Trust Shelburne Riverlands include dropping aspen along an old riverside field edge to stimulate the colony’s migration to the eroding riverbank’s edge. A two-acre opening along the growing aspen grove there is managed specifically for woodcock.
This is part of a continuing series looking at the life of the common trees in our Mahoosuc Mountain Region.
Photo Credits:
Young clonal stand and quaking aspen leaf photos by Larry Ely.
Bigtooth aspen leaf photo by Ayotte, Gilles, 1948- and licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
American woodcock photo by Rhododendrites and licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
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