Betula papyrifera

paper birch

Betulaceae

The Basics

USFS Plant Database

Flora of North America

Paper birch is a short-lived, shade-intolerant, pioneer species. It rapidly colonizes open disturbed sites created by wildfire, windthrow, or avalanche but lasts only one generation before it is replaced by shade-tolerant conifers or northern hardwoods. Paper birch seeds-i aggressively after wildfire, often forming large, essentially pure stands. (Plant Database)

A decoction has been used to treat dysentery, various diseases of the blood, induce sweating, and to ensure an adequate supply of milk in nursing mothers. Birch gum could have been medicinal for some stone-age gathers. The chewable gum contains zylitol, a disinfectant, and some terpenes, which could give the chewier a mild buzz. (Plant Guide)

The currently accepted scientific name of paper birch is Betula papyrifera Marsh. It is wide ranging and exhibits considerable ecotypic variation.

In boreal spruce ecosystems, paper birch forms nearly pure, pioneer communities on disturbed sites. It is rare in late successional or climax forests and generally restricted to openings. It is a principal component of boreal mixedwoods in Canada because its pioneering habit is favored by the relatively frequent 50- to 125-year fire return interval. Codominants in mixedwoods include trembling aspen (Populus tremuloides), black spruce (Picea mariana), white spruce (P. glauca), jack pine (Pinus banksiana), and balsam fir (Abies balsamifera). In the Northern Great Plains, paper birch forms climax woodland communities on moist, north- or east-facing slopes. (Plant Database)

Identification

Paper birch is a medium-sized, single- or multiple-stemmed, deciduous tree. In forests it typically has a slender trunk with a narrow crown, but in openings it has a wider crown spreading out from near the base. Multiple-stemmed trees are relatively common as a result of browsing by moose and snowshoe hares. Throughout much of its range, mature trees are 21-24 m tall and 25-30 cm in trunk diameter, but sometimes grow up to 75 cm in diameter. Paper birch is short-lived. Height growth ceases at about 60 to 70 years of age; few trees live more than 140 years. Paper birch is shallow-rooted with few roots found deeper than 60 cm below the soil surface. The bark is reddish-brown on saplings. On mature trees bark is thin, white, and smooth, often separating into papery strips, and is easily peeled off in sheets. (Plant Database)

Trees , to 30 m, usually 20 m or shorter; trunks often single, sometimes 2 or more, mature crowns narrowly round. Bark of young trunks and branches dark reddish brown, smooth, in maturity creamy to chalky white or pale to (infrequently) dark brown, readily exfoliating in paper-thin sheets; lenticels pale, horizontal, in maturity dark, much expanded, horizontal. Twigs without strong odor and taste of wintergreen, slightly to moderately pubescent, infrequently with scattered, small, resinous glands. Leaf blade ovate with 9 or fewer pairs of lateral veins, 5--9(--12) × 4--7 cm, base rounded, cuneate, or truncate, margins sharply to coarsely or irregularly doubly serrate or serrate-dentate, apex acute to short-acuminate; surfaces abaxially sparsely to moderately pubescent, often velutinous along major veins and in vein axils, covered with minute, resinous glands. Infructescences pendulous, cylindric, 2.5--5 × 0.6--1.2 cm, readily shattering with fruits in late fall; scales pubescent to glabrous, lobes diverging at or proximal to middle, central lobe narrowly elongate, obtuse, lateral lobes about equal in length to central lobe but several times broader, strongly divergent, held nearly at right angles to axis. Samaras with wings as broad as or slightly broader than body, extended nearly beyond body apically. 2 n = 56, 70, 84. (Flora of North America)

Threats

The bronze birch borer is the most serious insect pest of paper birch. It attacks and can kill injured, overmature, or decadent trees. There are numerous defoliators of paper birch, but they seldom cause mortality of healthy trees...Bacteria or decay fungi enter paper birch boles through wounds and branch stubs, and roots which come in contact with the roots of other trees infected with root-rotting fungi. Trees in Alaska are very susceptible to decay, but elsewhere tend to contain little defect. Most diseases can be identified by observing external signs.

As a forest type, paper birch stands are one of the least flammable. The canopy often has a high moisture content and the understory is lush...Fire generally kills or top-kills most paper birch trees; the thin, flammable bark makes the bole highly susceptible to girdling even by light surface fires. Although the bark of older trees is thicker, it is also more flammable once it begins to exfoliate...Paper birch seeds on the ground are destroyed by fire. Summer fires do not necessarily consume the catkins, but immature seeds will not ripen on killed or top-killed trees...Paper birch is well adapted to fire, recovering quickly by means of seedling establishment and vegetative regeneration. Seedling establishment is the most significant method of postfire recovery. Paper birch is a prolific producer of lightweight seeds that are easily dispersed by wind and readily germinate on fire-prepared seedbeds. Young trees sprout from the root collar following top-kill, but sprouting ability decreases after about 40 to 60 years of age.

Paper birch is a short-lived, shade-intolerant, pioneer species. It rapidly colonizes open disturbed sites created by wildfire, windthrow, or avalanche but lasts only one generation before it is replaced by shade-tolerant conifers or northern hardwoods. Paper birch seeds-in aggressively after wildfire, often forming large, essentially pure stands. Depending on the recovery of other species following fire, paper birch may also occur in mixed postfire stands with spruces, aspen, and other hardwoods. (Plant Database)

Reproduction

Seed production: Paper birch is a prolific seed producer. Seed production begins at about age 15, with optimum production at 40 to 70 years of age. Trees produce good seed crops about every other year. Seed production over a 3-year period in Maine ranged from 2.4 to 9.8 million seeds/acre (5.9-24.2/ha) in a paper birch stand with 149 seed trees per acre (368/ha). In undisturbed paper birch stands in Alaska, seed production varied between 2.2 and 294 million seeds/acre (5.4-728 million/ha).

Dispersal: The small, double-winged seeds are dispersed primarily by wind. Most seeds fall 100 to 200 feet (30-61 m) from the parent tree. Seedfall at a clearcut edge was 60 percent of that within the uncut stand, and at 328 feet (100 m) into the cut seedfall was 10 percent of that within the stand. Seed may travel great distances when blown across crusted snow. Nearly all the seed (about 90 to 95 percent) is shed from September through November.

Seed quality and dormancy: Discolored and empty seeds make up 14 to 47 percent of a crop. Seed viability is highest during heavy seed crop years and lowest during light seed crop years. In Maine, germination was 77 percent during a heavy seed year, but only 13 and 24 percent during 2 normal years. Seeds dispersed early have lower germination rates than those dispersed later. A small percentage of the seeds can remain viable on the forest floor for several years.

Germination and seedling establishment: Germination normally takes place in the spring following dispersal. Germination is generally best on disturbed mineral or mixed mineral-organic soil seedbeds. The small seeds are sensitive to soil moisture and temperature. Thus shade usually favors germination and initial establishment by preventing seedbeds from drying out and reaching excessively high temperatures. South or southwest aspects, excessively drained soils, insufficient rainfall, competing vegetation, and unshaded and undisturbed seedbeds deter establishment [51]. Seedlings will not grow on soils with a pH less than 5.0. Although germination and early survival are often best on mineral soils, seedling growth is best on humus seedbeds in moderate or full sunlight. First year seedlings are about 2 to 5 inches (5-12 cm) tall.

Vegetative reproduction: Paper birch sprouts following cutting or fire. Sprouts typically arise from the stump base or root collar. Prolific sprouting is common in young trees, with some individuals producing up to 100 sprouts. Sprout growth is rapid, sometimes up to 24 inches (60 cm) in the first growing season. Sprouting vigor decreases with age. Forty to fifty percent of 100- to 125-year-old trees produced stump sprouts within 1 year after cutting, while 80 to 90 percent of 40- to 50-year-old trees produced sprouts. (Plant Database)

Species Distribution

Paper birch has a transcontinental distribution across northern North America. It grows from Newfoundland and Labrador west along the northern limit of tree growth across Canada to northwestern Alaska, south to Washington, east and north in the mountains to western Montana and southwestern Alberta, east across the Prairie Provinces to Manitoba, and south and east through the Lake States to New England. Scattered outlying populations occur in the Great Plains of Montana and North Dakota, the Black Hills, the Appalachian Mountains from central New York to western North Carolina, and the Front Range of Colorado. Paper birch is cultivated in Hawaii. (Plant Database)

Citation

USDA Plant Database http://plants.usda.gov/characteristics.html USDA, NRCS. 2016. The PLANTS Database (http://plants.usda.gov, 4 February 2016). National Plant Data Team, Greensboro, NC 27401-4901 USA.

Flora of North America http://www.efloras.org/flora_page.aspx?flora_id=1 Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+ vols. New York and Oxford.

Silvics of North America Burns, R.M., and B.H. Honkala. 1990. Silvics of North America (Volume 1: Conifers, Volume 2: Hardwoods). USDA Forest Service Agricultural Handbook 654.

Intermountain Herbarium http://intermountainbiota.org/portal/collections/harvestparams.php Consortium of Intermountain Herbaria. 2016. http//:intermountainbiota.org/portal/index.php. Accessed on February 04.

Burke Museum Plant Image Collection The plant image collection at the Burke Museum, University of Washington.

Jepson Manual http://ucjeps.berkeley.edu/eflora/ The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA., hardcover; 1600 pages. ISBN-13: 978-0520253124.

USGS Plant Species Range Maps http://esp.cr.usgs.gov/data/little/ Critchfield, W.B., and Little, E.L., Jr., 1966, Geographic distribution of the pines of the world: U.S. Department of Agriculture Miscellaneous Publication 991, p. 1-97. Little, E.L., Jr., 1971-1978, Atlas of United States trees, volume 1,3,13,17, conifers and important hardwoods: U.S. Department of Agriculture Miscellaneous Publications.