Birch

From Wikipedia, the free encyclopedia - View original article

Birch
Betula pendula 001.jpg
Silver Birch
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Rosids
Order:Fagales
Family:Betulaceae
Genus:Betula
L.
Species

Many species;
see text and classification

 
Jump to: navigation, search
For other uses, see Birch (disambiguation).
Birch
Betula pendula 001.jpg
Silver Birch
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Rosids
Order:Fagales
Family:Betulaceae
Genus:Betula
L.
Species

Many species;
see text and classification

Birch is a broadleaved deciduous hardwood tree of the genus Betula (/ˈbɛtjʊlə/),[1] in the family Betulaceae, which also includes alders, hazels, and hornbeams, and is closely related to the beech/oak family, Fagaceae. The genus Betula contains 30 to 60 known taxa of which 11 are on the IUCN 2011 Red List of Threatened Species. They are typically rather short-lived pioneer species widespread in the Northern Hemisphere, particularly in northern temperate and boreal climates. This tree is sometimes called "The Watchful Tree" because of eye-like impressions on the bark.

Etymology[edit]

The common name birch comes from Old English birce, bierce, from Proto-Germanic *berk-jōn (cf. German Birke, West Frisian bjirk), an adjectival formation from *berkōn (cf. Dutch berk, Low German Bark, Norwegian bjørk), itself from the Proto-Indo-European root *bʰerHǵ- ~ bʰrHǵ-, which also gave Lithuanian béržas, Ukrainian beréza, Albanian bredh ‘fir’, Ossetian bærz(æ), Sanskrit bhurja, Latin fraxinus ‘ash (tree)’. This root is presumably derived from *bʰreh₁ǵ- ‘to shine’, in reference to the birch's white bark. The Proto-Germanic rune berkanan is named after the birch.

The generic name betula is from Latin, which is a diminutive borrowed from Gaulish betua (cf. Old Irish bethe, Welsh bedw).

Description[edit]

The front and rear sides of a piece of birch bark

Birch species are generally small to medium-sized trees or shrubs, mostly of temperate climates. The simple leaves are alternate, singly or doubly serrate, feather-veined, petiolate and stipulate. They often appear in pairs, but these pairs are really borne on spur-like, two-leaved, lateral branchlets.[2] The fruit is a small samara, although the wings may be obscure in some species. They differ from the alders (Alnus, other genus in the family) in that the female catkins are not woody and disintegrate at maturity, falling apart to release the seeds, unlike the woody, cone-like female alder catkins.

The bark of all birches is characteristically marked with long, horizontal lenticels, and often separates into thin, papery plates, especially upon the paper birch. It is resistant to decay, due to the resinous oil it contains. Its decided color gives the common names gray, white, black, silver and yellow birch to different species.

The buds form early and are full grown by midsummer, all are lateral, no terminal bud is formed; the branch is prolonged by the upper lateral bud. The wood of all the species is close-grained with satiny texture, and capable of taking a fine polish; its fuel value is fair.

Flower and fruit[edit]

The flowers are monoecious, opening with or before the leaves and borne once fully grown these leaves are usually 3–6 millimetres (0.12–0.24 in) long on three-flowered clusters in the axils of the scales of drooping or erect catkins or aments. Staminate aments are pendulous, clustered or solitary in the axils of the last leaves of the branch of the year or near the ends of the short lateral branchlets of the year. They form in early autumn and remain rigid during the winter. The scales of the staminate aments when mature are broadly ovate, rounded, yellow or orange color below the middle, dark chestnut brown at apex. Each scale bears two bractlets and three sterile flowers, each flower consisting of a sessile, membranaceous, usually two-lobed, calyx. Each calyx bears four short filaments with one-celled anthers or strictly, two filaments divided into two branches, each bearing a half-anther. Anther cells open longitudinally. The pistillate aments are erect or pendulous, solitary; terminal on the two-leaved lateral spur-like branchlets of the year. The pistillate scales are oblong-ovate, three-lobed, pale yellow green often tinged with red, becoming brown at maturity. These scales bear two or three fertile flowers, each flower consisting of a naked ovary. The ovary is compressed, two-celled, and crowned with two slender styles; the ovule is solitary.

Ecology[edit]

Birch trees near stream in Hankasalmi, Finland
A stand of birch trees

Birches often form even-aged stands on light, well-drained, particularly acidic soils. They are regarded as pioneer species, rapidly colonising open ground especially in secondary successional sequences following a disturbance or fire. Birches are early tree species to establish in primary successions, and can become a threat to heathland if the seedlings and saplings are not suppressed by grazing or periodic burning. Birches are generally lowland species, but some species, such as Betula nana, have a montane distribution. In the British Isles, there is some difference between the environments of Betula pendula and Betula pubescens, and some hybridization, though both are "opportunists in steady-state woodland systems". Mycorrhizal fungi, including sheathing (ecto)myccorhizas, are found in some cases to be beneficial to tree growth.[3]

Birch foliage is used as a food plant by the larvae of a large number of lepidopteran (butterflies and moths) species.

Species[edit]

Birch leaves
Birches native to Europe and Asia include

Note: many American texts have B. pendula and B. pubescens confused, though they are distinct species with different chromosome numbers.

Birches native to North America include

Uses[edit]

Birch plywood
Unfinished birch
Finished birch

Due to the hardness of Birch, it is better to shape it with power tools, as it is quite difficult to work it with hand tools.[4]

Medical[edit]

Paper[edit]

A birch bark inscription excavated from Novgorod, circa 1240–1260

Wood pulp made from birch gives relatively long and slender fibres for a hardwood. The thin walls cause the fibre to collapse upon drying, giving a paper with low bulk and low opacity. The birch fibres are, however, easily fibrillated and give about 75% of the tensile strength of softwood[clarification needed].[11] The low opacity makes it suitable for making glassine.

In India, the birch (Sanskrit: भुर्ज, bhurja) holds great historical significance in the culture of North India, where the thin bark coming off in winter was extensively used as writing paper. Birch paper (Sanskrit: भुर्ज पत्र, bhurja patra) is exceptionally durable and was the material used for many ancient Indian texts.[12][13] The Roman period Vindolanda tablets also use Birch as a material on which to write and Birch bark was used widely in ancient Russia as note paper (beresta) and for decorative purposes and even making footwear.

Tonewood[edit]

Baltic birch is among the most sought-after wood in the manufacture of speaker cabinets. Birch has a natural resonance that peaks in the high and low frequencies, which are also the hardest for speakers to reproduce. This resonance compensates for the roll-off of low and high frequencies in the speakers, and evens the tone. Birch is known for having "natural EQ".[citation needed]

Drums are often made from birch. Prior to the 1970s, it was one of the most popular drum woods. Because of the need for greater volume and midrange clarity, drums were made almost entirely from maple until recently[clarification needed], when advances in live sound reinforcement and drum microphones have allowed the use of birch in high-volume situations. Birch drums have a natural boost in the high and low frequencies, which allows the drums to sound fuller.

Birch wood is sometimes used as a tonewood for semiacoustic and acoustic guitar bodies, and occasionally for solid-body guitar bodies. It is also a common material used in mallets for keyboard percussion.

Culture[edit]

See also[edit]

References[edit]

  1. ^ Sunset Western Garden Book, 1995:606–607
  2. ^ Keeler, Harriet L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scriber's Sons. pp. 295–297. 
  3. ^ Birches. (A Symposium, Royal Botanic Garden, Edinburgh 24–26 September 1982. Proceedings of the Royal Society of Edinburgh, 85B, 1–11, 1984.
  4. ^ "Birch". Wood Magazine. Retrieved December 1, 2013. 
  5. ^ "Birch Tar – How to collect it". Archived from the original on February 27, 2008. 
  6. ^ Prakel, David (August 1979). "BBC's Home Service", Hi-Fi Answers, pp67–9 (Courtesy link)
  7. ^ Joyce, Daniel. "Birch Seed Leaves". reapermini.com. 
  8. ^ Grygus, Andrew. "Alokon". Clove Garden. 
  9. ^ White Birch – American Cancer Society (cancer.org)
  10. ^ William Arthur Clark (January 1, 1937). "History of Fracture Treatment Up to the Sixteenth Century". The Journal of Bone & Joint Surgery (Needham, MA, USA: The Journal of Bone & Joint Surgery, Inc.) 19 (1): 61–62. "Another method cited was that of splints made of birch bark soaked in water until quite soft. They were then carefully fitted to the limb and tied with bark thongs. On drying, they became stiff and firm. There is no record of the use of extension, but, nevertheless, very few crippled and deformed Indians were to be seen." 
  11. ^ Nanko, Hiroki; Button, Alan; Hillman, Dave (2005). The World of Market Pulp. USA: WOMP, LLC. pp. 192–195. ISBN 0-615-13013-5. 
  12. ^ Sanjukta Gupta, "Lakṣmī Tantra: A Pāñcarātra Text", Brill Archive, 1972, ISBN 90-04-03419-6. Snippet:... the text recommends that the bark of the Himalayan birch tree (bhurja-patra) should be used for scribbling mantras ...
  13. ^ Amalananda Ghosh, "An Encyclopaedia of Indian Archaeology", BRILL, 1990, ISBN 90-04-09264-1. Snippet:... Bhurja-patra, the inner bark on the birch tree grown in the Himalayan region, was a very common writing material ...
  14. ^ "Traditional celebrations in Novosej". RASP. Retrieved August 28, 2013. 

External links[edit]