Flora of the Canadian Arctic Archipelago
English: Arctic dwarf birch,
French: Bouleau nain.
Betulaceae, Birch family.
Published in Sp. Pl. 983. 1753.
Vegetative morphology. Plants 10–30 cm high (on Arctic islands); shrubs; forming colonies by layering; glandular viscid (small glands), or not glandular viscid. Aerial stems decumbent, or prostrate. Branches grey-brown, or brownish (differentiated into short and long shoots); covered with few inconspicuous sessile glands; glabrescent, or hairy (sparsely to densely so, seen at 10×). Branchlets grey-brown; hairy (at the tips of twigs). Leaves present; distributed along the stems; alternate (2-ranked); dying annually and non-persistent (deciduous). Petioles 0.5–2 mm long; glabrous, or hairy (sparsely). Juvenile leaves glabrous. Leaf blade bases obtuse, or cuneate. Blades 8–15 mm long, 6–10(–20) mm wide, obovate (broadly orbiculate), flat, veins pinnate (with 2–6 pairs of prominent lateral veins). Blade adaxial surface fresh green (dark) or shiny, glabrous. Blade abaxial surface glabrous or hairy (sparsely; occasionally with a few small resinous glands). Blades not lobed. Blade margins crenate (deeply), with teeth toward the apex, with teeth per cm 2–8; apices obtuse, or rounded.
Reproductive morphology. Plants monoecious. Flowering stems with leaves (on short shoots). Inflorescences catkins; dense; cylindrical (erect). Pedicels absent. Catkins flowering as leaves emerge (the catkins are produced the season before flowering but retained in buds during winter). Female catkins 5–15 mm long; 3.5–4.5(–10) mm wide; sub-globose; peduncles 1–3 mm long; borne on a flowering branchlet. Floral bracts green (or a calyx in the male flowers with red tips, turning brown with age, central lobe elongate, rarely preserved in herbarium specimens); 0.5–1.5(–2.5) mm long; 0.8–2 mm wide; apices divided into 3-lobes. Flowers unisexual. Staminate flowers inconspicuous (staminate catkins mostly terminal on branchlets, rarely preserved). Sepals absent (female flowers), or conventional (male flowers). Petals absent. Stamens present (male flowers), or absent (female flowers); (1–)2–3(–4). Ovary inferior; carpels 2; syncarpous. Styles 2; free. Ovules per ovary 1. Fruit dry; a samara (broadest near the centre, with definite wings that are much narrower than the body and not extended beyond it at the apex). Seeds 1.
Chromosome information. 2n = 28.
2n (4x) = 28. For the collective species, Zhukova et al. (1973, northeastern Asia); Krogulevich (1976a, northern Siberia).
Ploidy levels recorded 4x.
Ecology and habitat. Substrates: tundra; rocks (barrens).
North American distribution. Nunavut Islands. Range in the Canadian Arctic Archipelago limited. Low Arctic. Arctic islands: Baffin.
Northern hemisphere distribution. Amphi-Atlantic. Northern Iceland, Northern Fennoscandian, KaninPechora, Polar Ural Novaya Zemlya, YamalGydan, Taimyr Severnaya Zemlya, Central Canada, Labrador Hudson Bay, West Greenland, East Greenland.
General notes. Furlow (1997) distinguishes subsp. nana as having young pubescent twigs, not covered with a conspicuous resinous layer. This is the taxon that occurs in the Canadian Arctic Archipelago. Plant with twigs glabrous or only puberulent, and covered with a thick resinous coating, are B. nana subsp. exilis (Sukaczev) Hultén. This subspecies occurs in the Yukon, Alaska, and Northern Asia.
Betula nana subsp. nana occurs in both eastern and western Greenland at latitudes north of 63°N. In northern Europe, the range of this subspecies extends across the subarctic zone and southward in the Alps and other ranges.
There seems to be some agreement that there are three major geographic races, the very widely amphi-Atlantic subsp. nana, the Russian-Siberian subsp. tundrarum, and the widely amphi-Beringian subsp. exilis (Elven et al. 2003).
Illustrations. • Habitat. Plant growing in mine tailings. Most of the leaves turn orange-brown in the fall. Norway, Roros. Aiken. No voucher. • Close-up of stem. White arrow points to a catkin. Black arrow points to a conspicuous gland on the stem. Norway, Roros. Aiken. No voucher. • Arctic Island Distribution.
This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.
Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.
Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa..