Commercial timbers

H. G. Richter and M. J. Dallwitz


Betula spp. (Birke, birch)

Nomenclature etc. BETULACEAE. B. verrucosa = B. pendula. Trade and local names: es werden "schwere", "mäßig schwere" und "leichte" Gruppen unterschieden; "schwer": z.B. B. alleghaniensis - Yellow Birch, B. lenta - sweet birch, black birch, B. schmidtii - Japanische Hartbirke (onoore); "mäßig schwer": z.B. B. maximowicziana - Ostasiatische Birke (saibada), B. pubescens - Moorbirke, B. verrucosa - Gemeine Birke, Weißbirke, Sandbirke (D), European birch, common birch (GB), Berken (NL), Bouleau (F), Abedul (E); "leicht": z.B. B. papyrifera - paper birch, B. populifera - gray birch, wire birch, B. alnoides - Indische Birke (layang) commercially three types of birch timbers are distinguished: "heavy" includes B. alleghaniensis - yellow birch, B. lenta - sweet birch, black birch, B. schmidtii - Japanese hard birch (onoore); "moderately heavy": B. maximowicziana - Eastasian birch (saibada) and European species such as B. pubescens, B. verrucosa - European birch, common birch (GB), Berken (NL), Bouleau (F), Abedul (E); "light": B. papyrifera - paper birch, B. populifera - gray birch, wire birch, B. alnoides - Indian birch (layang). Status of protection under CITES regulations: not protected.

Tree. Geographic distribution: Europe, excl. Mediterranean, North America, temperate Asia, and India, Pakistan, Sri Lanka.

General. Growth ring boundaries distinct. Heartwood basically yellow to white or grey to red brown (heavier timbers yellowish brown to brown). Sapwood colour similar to heartwood colour. Basic specific gravity 0.46–0.61–0.8 g/cm³ (average weight "heavy": 0.70, "moderately heavy": 0.60, "light": 0.55).

Vessels. Vessels present. Wood diffuse-porous. Vessels in multiples, commonly short (2–3 vessels) radial rows (occasionally also in radial chains of 4–6). Average tangential vessel diameter 30–90–130 µm. Average number of vessels/mm² 40–60. Perforation plates scalariform, with (6–)10–20(–25) bars. Intervessel pits alternate, average diameter (vertical) 3–4 µm. Vessel-ray pits with distinct borders, similar to intervessel pits. Helical thickenings absent.

Tracheids and fibres. Fibres of medium wall thickness. Average fibre length 300–1000–1700 µm. Fibre pits mainly restricted to radial walls, distinctly bordered. Fibres non-septate.

Axial parenchyma. Axial parenchyma banded. Axial parenchyma bands marginal (or seemingly marginal), fine, up to three cells wide. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 6–8–10.

Rays. Rays 10–17–20 per tangential mm, multiseriate, also if only few, 1–4 cells wide. Rays composed of a single cell type. Homocellular ray cells procumbent.

Mineral inclusions. Crystals not observed. Silica not observed.

Miscellaneous. • Wood surface. • Transverse section. Betula alba. • Tangential section. Betula alba. • Radial section. Betula alba. (insert: SEM foto depicts twin scalariform perforation plates).


Cite this publication as: H. G. Richter and M. J. Dallwitz (2000 onwards). 'Commercial timbers: descriptions, illustrations, identification, and information retrieval.' In English, French, German, and Spanish. Version: 4th May 2000. http://biodiversity.uno.edu/delta/.

Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993 onwards, 1995 onwards, 1998) should also be cited (see General references).

Index