Downy birch ( Betula pubescens )
The bog birch ( Betula pubescens ), also called hair birch , broom birch , glass birch or hairy birch , is a species of the birch family (Betulaceae). It is a characteristic tree ( phanerophyte ) of the bog and swamp forests as well as drier areas in rain bog complexes . As a pioneer tree species , it is able to quickly colonize newly created habitats .
The downy birch grows as a deciduous tree or shrub, i.e. a deciduous tree or shrub, with one or more trunks, and can reach heights of up to 30 meters. Single copies can be around 120 years old. The bark is initially dark reddish-brown, later light reddish-brown to tan or brown and finally greyish-white; it is smooth and not fielded in diamond-shaped panels like that of the silver birch and peeled off later in paper-thin panels. The bark of the stiffly upright or horizontally protruding branches is initially downy hairy, later reddish brown. The horizontal lenticels are initially light, later they enlarge and become dark. The terminal buds of the bog birch are pointed ovoid and slightly curved. The bud scales are gray to gray-brown or greenish-gray. They are rounded at the end and ciliate white on the edges.
Young leaves smell aromatic and are also downy hairy, especially along the leaf veins . The alternate leaves are arranged in a petiole and a leaf blade. The egg-shaped or rhombic-egg-shaped, heart-shaped leaf blade is 3 to 5 inches long and doubly serrate.
Like all birches, the bog birch is single-sexed ( monoecious ). The male inflorescences (catkins) are elongated, cylindrical. The female inflorescences are about 2 to 4 inches long, cylindrical, later drooping. The middle lobes of the three-lobed fruit scales are clearly drawn out and protrude beyond the upwardly curved side lobes. The approximately 3 millimeter large seeds ( nuts or nuts) are broadly winged for better spreading by the wind. One kitten contains around 450 seeds. The bog birch blooms from April to May and the fruits ripen from August.
The number of chromosomes is 2n = 56.
The bog birch occurs in the temperate climatic zones of Europe and Asia from Iceland via Scandinavia , Russia to the east to the Yenisei region and south to northern Italy and the Balkan region to the Caucasus . Downy birches form the subarctic tree line north of the boreal coniferous forests (taiga) . Their elevation ranges from the lowlands (Kollin) to the tree line (subalpine). In the Alpine region, birch trees rise to around 2000 meters above sea level. In the Allgäu Alps, the bog birch rises up to 1700 meters above sea level.
It settles damp to waterlogged, lime-free, low to moderate base supplied , acidic peat and Anmoorböden (to about pH <5) with low to very low supply of nutrients ( oligotrophic to mesotrophic ). It grows in bog and swamp forests in the mountains as well as in drained rain bogs and on the slopes of intact raised bogs. In their centers, however, due to the poor supply of nutrients, it usually only develops a shrub-like habit. It also grows in fens , floodplain forests and damp hedges . In foggy and rainy climates, it can also exist in drier locations. The propagation biology of the bog birch is specifically geared towards the primary stages of a succession . Only in Scandinavia and the tundras of Northern Europe and on special locations such as moors does it form natural climax societies .
The downy birch is a characteristic species of the downy birch and pine-spruce break forests (Molinio-Betuletalia pubescentis). These swamp forests are often rich in berry bushes such as bog berries ( Vaccinium uliginosum ) and peat mosses such as swamp peat moss ( Sphagnum palustre ) and fringed peat moss ( Sphagnum fimbriatum ). The forests are mostly sparse, sparse and species-poor. The downy birch also forms species-poor secondary "moor forests" on drained raised bog locations, mostly with the cotton grass and peat moss in the herb and moss layer . Furthermore, the bog birch grows in deciduous forests and bushes in damp to drier locations together with the silver birch ( Betula pendula ), the ash ( Fraxinus excelsior ), the rowanberry ( Sorbus aucuparia ) and the quivering aspen ( Populus tremula ).
The bog birch is a type of light wood, which means that it grows preferentially in full light, but can tolerate shading within limits. Their ecological focus is on well-humid to often soaked, air-poor, acidic to very acidic soils. It is also a pioneer tree species.
Their reproductive biology is specifically geared towards the conditions of propagation on raw soil and open spaces. Characteristic is their high seed production, which contributes to the rapid settlement of bald areas. A free-standing, old bog birch produces up to four kilograms of seeds. If these were placed next to each other, a distance of 60 kilometers or an area of 180 square meters would result. The seed density in nature can be up to 50,000 pieces per square meter. There are approximately five million pollen grains in a male kitten. The pollen can fly up to 2,000 kilometers.
The birch's unpretentious nature with regard to the supply of nutrients and its rapid growth make it a pioneer plant , which quickly colonizes suitable light-favored areas such as clearcuts , clearings and burned areas . Especially in bogs, where other woody plants do not find suitable growing conditions due to the high acid content of the bog soils , it has a competitive advantage and can form bushes with few species. It is even less demanding than the silver birch ( Betula pendula ), which is also a pioneer in many areas.
Bog birches are insensitive to winter frosts. At temperatures below −40 ° C they convert starch into oil in the twigs , releasing heat. The leaves only freeze to death from −6 ° C. When it is cold, the ventilation cracks ("cork warts") that appear in the area of the white bark are closed and thus increase the frost resistance. The downy birch is considered the northernmost tree species in Europe. A winter temperature of -33 ° C on average does not cause any loss of vitality. The frost hardness remains stable throughout the winter despite the intermittent warming (up to +18 ° C).
In Northern Europe, the white coloring effect of the bark ingredient betulin protects the thin bark from bark burn . Due to the low sun in spring and the reflection from snow surfaces, dark bark would overheat and the cell division tissue would be damaged.
The downy birch has a flat-rooted heart- root system . Strongly developed horizontal roots are missing; Instead of one main root, several vertically growing roots of different strengths are formed on the rhizome with several side roots up to 20 meters long. Shallow-rooters are primarily geared towards absorbing seeping rainwater. The downy birch has a high water flow rate. A fully grown birch tree can draw up to 500 liters of water from the ground on a hot summer day. The fine roots are surrounded by a dense network of symbiotic fungi ( mycorrhiza ), which greatly favors the supply of nutrients.
The bog birch plays a decisive role for many phytophagous insects. For example, some species of cicadas only suckle (2nd degree monophag) on both downy birch and silver birch. These are mainly species of the genus Oncopsis within the family of masked cicadas (Macropsinae).
Some authors distinguish three subspecies of Betula pubescens Ehrh .:
- Carpathian birch ( Betula pubescens subsp. Carpatica ( Waldst. Et Kit. Ex. Willd. ) Asch. Et Graebn. ); Syn .: Betula carpatica Waldst. et kit. ex. Willd. , Betula pubescens subsp. glutinosa Berher
- Betula pubescens subsp. pubescens ; Syn . : Betula alba L.
- Fjellbirke ( Betula pubescens subsp. Tortuosa ( Ledeb. ) NIOrlova Nyman ); Syn . : Betula czerepanovii N.I. Orlova , Betula pubescens subsp. czerepanovii ( NIOrlova ) Hämet-Ahti , Betula tortuosa Ledeb.
According to R. Govaerts, Betula pubescens Ehrh. differentiated the following varieties:
- Betula pubescens var. Fragrans Ashburner & McAll. : It occurs in Scotland.
- Betula pubescens var. Golitsinii (VNVassil.) Tzvelev , Novosti Sist. Vyssh. Rest. 34: 61 (2002): It occurs in European Russia.
- Betula pubescens nothovar. kusmisscheffii (rule) Gürke = Betula pubescens var. pubescens × Betula pubescens var. pumila : It occurs in Finland and northern Russia.
- Betula pubescens var. Litwinowii (Doluch.) Ashburner & McAll. : It occurs from northern and eastern Turkey to northern Iran.
- Betula pubescens var. Pubescens (Syn .: Betula pubescens var. Glabrata Wahlenb. , Betula carpatica Waldst. & Kit. Ex Willd. , Betula pubescens subsp. Carpatica (Waldst. & Kit. Ex Willd.) Asch. & Graebn. ): The common bog birch. It includes the Carpathian birch . It occurs from Europe to Russia's Far East.
- Betula pubescens var. Pumila (L.) Govaerts , World Checklist Seed Pl. 2 (1): 10 (1996) (Syn .: Betula tortuosa Ledeb. , Betula pubescens subsp. Tortuosa (Ledeb.) Nyman , Betula pubescens subsp. Czerepanovii (NIOrlova) Hämet-Ahti ): The fell birch . It occurs from Northern Europe to Siberia and from Newfoundland to Greenland.
The Carpathian Birch
The fell birch
In the boreal north of Europe, the mountain birch forms its own forest belt. The variable and taxonomically elusive plant family used to be mostly Betula pubescens subsp. tortuosa (Ledeb.) called Nyman , this name is only used today for a clan widespread in the Altai . The most used name of the clan is Betula pubescens Ehrh. subsp. czerepanovii (NIOrlova) Hämet-Ahti . It is then considered a subspecies of the downy birch ( Betula pubescens ). The Fjell birch differs from the typical subspecies of the downy birch in various features (e.g. leaf shape), the mostly crooked, twisted trunks and the often multi-stemmed growth are striking. The origin of the mountain birch is now mostly interpreted as an introgressive hybridization with the dwarf birch ( Betula nana ). Primary hybrids are triploid and rarely occur. Backcrossing with bog birch creates diverse hybrid swarms, in which the silver birch also participates as a partner . This mechanism (which is quite widespread in the plant kingdom) can be used to cross characteristics of the dwarf birch into bog birch populations and thus explain the diverse, ecologically plastic Nordic populations .
In the north, the fell birch forms its own forest belt and various natural forest communities (overview in). In Scandinavia they form the natural tree line , which in central Norway is at altitudes of around 1,200 meters and near the coast at around 600 meters. It is the only forest-forming tree species in Iceland . To the east, under more continental climatic influence, the mountain birch forests are replaced by conifer forests. Mountain birch forests, especially in their lichen-rich formation, are important grazing grounds for the reindeer herds of the Sami people . For some time, an advance of the forests northwards and uphill has been registered, which can amount to a few hundred meters in altitude. This can convincingly be interpreted as the effect of climate change, so that these previously often still primeval forest-like, economically inferior stocks are now also subject to increased human influence.
Finds of this subspecies are also reported from the Alps. The actual status of these populations and their relationship to the Nordic Fjell Birch still require clarification.
Some of the birch wood is almost white and has no grain. It can be smoothed very well, which is why it is a popular wood for furniture construction. It is only used indoors, as it decomposes very quickly under putrefactive conditions. Birch wood is the only wood that burns when it is damp, which is why it is a very popular firewood. The firewood should be split to dry as the bark is impermeable to water.
The leaves of the downy birch as well as the silver birch contain up to three percent flavonoids, in particular hyperoside , quercetin , quercitrin and myricetingalactoside , but also vitamin C , saponins and essential oils . The birch buds contain fat-soluble flavone methyl ether . Teas and pressed juices made from birch leaves cause increased salt and water excretion. They are therefore used for flushing therapy of the kidneys, for inflammation of the lower urinary tract and kidney gravel . Birch leaves are traditionally used because of their uric acid lowering effect in gout and rheumatic complaints or as an additive to so-called blood cleansing teas . The very young, fresh leaves can be eaten in spring salads. Hair lotions made from birch leaf extracts are said to work against hair loss and dandruff.
Preferred uses in the wood industry are veneers in furniture construction and interior design. Also for imitating precious woods such as walnut and cherry for period furniture . The wood is also used for turning and carving work, as well as for sports equipment, musical instruments, brush and brush handles and as industrial wood for chipboard and fiberboard. In Scandinavia it is of great importance for plywood panels .
Sources and further reading
- John J. Furlow: Betulaceae. In: Flora of North America , Volume 3, 1997 ( Betula pubescens , efloras.org, section description and systematics).
- Christian Wagner: On the ecology of the downy birch Betula pubescens Ehrh. in raised bogs in Schleswig-Holstein with special consideration of regeneration processes in peat cuttings. Announcements of the Geobotany Working Group in Schleswig-Holstein and Hamburg, Volume 47, Kiel 1994 (also dissertation, Kiel 1992).
- M. Natkevičaitė-Ivanauskienė et al .: Lietuvos TSR flora. Volume 3, Vilnius 1961.
- Bog birch. In: FloraWeb.de.
- Bog birch . In: BiolFlor, the database of biological-ecological characteristics of the flora of Germany.
- Profile and distribution map for Bavaria . In: Botanical Information Hub of Bavaria .
- Betula pubescens Ehrh. In: Info Flora , the national data and information center for Swiss flora . Retrieved October 3, 2015.
- Distribution map worldwide
- Thomas Meyer: Data sheet with identification key and photos at Flora-de: Flora von Deutschland (old name of the website: Flowers in Swabia )
- Photo of a birch mask cicada
- German Forest Protection Association
- Jean-Denis Godet: Native trees and bushes , nature book, Augsburg 1998, ISBN 3-89440-296-2 .
- Erich Oberdorfer : Plant-sociological excursion flora for Germany and neighboring areas . 8th edition. Verlag Eugen Ulmer, Stuttgart 2001, ISBN 3-8001-3131-5 , p. 313.
- K.-H. Rechinger: Betulaceae. In: G. Hegi: Illustrated flora of Central Europe . Volume 3, Part 1. Parey, Berlin 1981, pp. 153-156.
- Erhard Dörr, Wolfgang Lippert : Flora of the Allgäu and its surroundings. Volume 1, IHW, Eching 2001, ISBN 3-930167-50-6 , p. 421.
- Heinz Ellenberg, HE Weber, R. Düll, V. Wirth, W. Werner, D. Paulißen: Pointer values of plants in Central Europe. Erich Goltze, Göttingen 1992, ISBN 3-88452-518-2 (Scripta Geobotanica 18).
- Randolf Schirmer: Birch - Multiplication Artist and Survival Strategist (PDF) lwf.bayern.de.
- Herbert Nickel: The leafhoppers and planthoppers of Germany (Hemiptera, Auchenorrhyncha): Patterns and strategies in a highly diverse group of phytophagous insects. Pensoft, Sofia / Moscow 2003, ISBN 954-642-169-3 .
- Betula pubescens in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland. Retrieved November 27, 2010.
- Rafaël Govaerts (Ed.): Betula - World Checklist of Selected Plant Families of the Royal Botanic Gardens, Kew. Last accessed on January 11, 2017.
- Moorbirke on Nature's Gate II.
- L. Haemet-Ahti: Mountain birch and mountain birch woodland in northwest Europe. In: Phytocoenologia , Vol. 15, No. 4, 1987, pp. 449-453.
- Kesara Anamthawat-Jonsson, Aegir Thor Thorsson: Natural hybridization in birch: triploid hybrids between Betula nana and B. pubescens. In: Plant Cell, Tissue and Organ Culture 75, 2003, pp. 99-107.
- Jan Wehberg: Vegetation-ecological analysis of the mountain birch forests in Northern Norway (Finnmark) - with special consideration of anthropogenic factors. Geographical Society, Hamburg 2007, ISBN 978-3-515-09104-6 (Diss. Univ. Hamburg 2006).
- Wilfried Robert Franz: Betula pubescens subsp. czerepanovii (ORLOVA) HÄMET-AHTI (= B. tortuosa auct.) in Carinthia. In: Linz biological contributions. Volume 32, Issue 2, Linz 2000, pp. 628–630.
- Max Wichtl (Ed.): Tea drugs. Wissenschaftliche Verlagsgesellschaft, Stuttgart 1989, ISBN 3-8047-1009-3 .
- Uses of local timber ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , accessed July 30, 2006.