Betula pubescens
Downy birch (Betula pubescens)
The downy birch (Betula pubescens), also hair - birch, broom - called birch, downy birch or Hairy Birch, is a plant belonging to the birch family ( Betulaceae ). It is distinctive tree ( Phanerophyt ) of marsh and swamp forests and drier areas in rain bog complexes. As a pioneer species to colonize it is able to rapidly newly created habitats.
- 6.1 Medicinal plant
- 6.2 timber industry
- 8.1 Literature
- 9.1 Notes and references
Description
The downy birch grows as a deciduous, so deciduous tree or shrub with one or more strains, and can reach heights of growth of up to 30 meters. Single copies may be about 120 years old. The bark is dark reddish- brown at first, later light reddish brown to tan or brown and finally greyish - white; it is smooth and not checkered in rhombic plates like those of silver birch and peels off late into paper-thin sheets. The bark of the straight upright or protruding horizontally growing branches is initially hairy fluffy, later reddish brown. The horizontal lenticels are initially bright, later they enlarge and become dark. The terminal buds of downy birch are pointed egg-shaped and slightly curved. The bud scales are gray to gray-brown or greenish gray. They are rounded at the end and ciliated white at the edges.
Young leaves are aromatic scented and are also hairy fluffy, especially along the leaf veins. The alternate arranged leaves are divided into petiole and leaf blade. The ovate or rhombic- ovate, heart-shaped leaf blade is cut 3 to 5 inches long and double.
Like all birches is the downy birch monoecious getrenntgeschlechtig ( monoecious ). The male inflorescences ( catkins ) are elongate cylindrical. The female inflorescences are about 2 to 4 inches long, cylindrical, later suspended. The middle lobe of the three-lobed fruit scales are clearly preferred and tower above the upwardly curved side tabs. The approximately 3 millimeters large seed (nut fruits or nutlets ) are broadly winged to better spread by the wind. A kitten contains about 450 seeds. The downy birch flowers from April to May and the fruits ripen in August.
Fruit stand of downy birch; left fruit dandruff, right winged fruit
Image of a bud in winter, note the hairy stems
Pubescence of the downy birch; young branch left, right underside of a young leaf, right down bud
Occurrence
The downy birch comes in the temperate climates of Europe and Asia from Iceland across Scandinavia, Russia to the east to the Jenisseigebiet and south to northern Italy and the Balkans to the Caucasus front. Bog birch form the subarctic treeline north of the boreal coniferous forest (taiga ). Your altitudinal distribution ranges from the lowlands ( colline ) up to the tree line ( subalpine ). In the Alpine region birches rise to about 2000 meters above sea level.
They settled moist to waterlogged, low in calcium, low base supplied to moderate acidic bog and Anmoorböden ( to about pH < 5) with low to very low nutrient ( oligotrophic to mesotrophic ). It grows in bog and swamp forests both in the mountains and in drained bogs and rain in Randgehänge intact raised bogs. However, in the centers of which it forms due to poor nutrient supply usually only a shrubby growth form from. It also grows in fens, water meadows and damp hedgerows. In fog and rainy climates, it may also exist on drier sites. The reproduction biology of downy birch is specifically geared to the primary stages of succession. Only in Scandinavia and the tundra of northern Europe as well as on special locations such as bogs it forms natural Klimaxgesellschaften.
Socialization
The downy birch is a characteristic species of bog birch and pine - spruce swamp forests ( Molinio - Betuletalia pubescentis ). These swamp forests are often rich in berry bushes such as the bog bilberry (Vaccinium uliginosum ) and peat moss as the marsh peat moss (Sphagnum palustre ) and the fringed bog moss (Sphagnum fimbriatum ). The forests are usually slow-growing, sparse and species-poor. The Downy Birch also forms on drained peat bog sites species-poor secondary " bog woodland " usually with the vaginal cotton grass and sphagnum moss in the herb and moss layer. Furthermore, the downy birch grows in deciduous forests and thickets moist to drier sites, together with the silver birch (Betula pendula), the ash (Fraxinus excelsior), rowan (Sorbus aucuparia ) and aspen (Populus tremula ).
Ecology
The downy birch is a Lichtholzart, that is, it grows preferably in full light, but bear in borders shading. Your ecological focus is on thoroughly moistened to often soaked, airless, acidic to very acidic soils .. It is also a pioneer tree species.
Survival strategies
They reproduce Biology is specifically geared to the propagation conditions on raw soils and open spaces. It is characterized by its high seed production, which contributes to a rapid colonization of barren areas. A free-standing, old downy birch produces up to four kg seeds. If these were put next to each other, a distance of 60 kilometers or an area of 180 square meters would result. The seed density can be in nature up to 50,000 pieces per square meter. In a male kitten there are approximately five million pollen grains. The pollen can fly up to 2,000 kilometers.
The modesty of the birch in relation to the supply of nutrients and their rapid growth make it a pioneer plant, which colonized suitable light- favored areas such as clearcuts, forest clearings and burnt areas quickly. Especially in bogs, where other trees do not find the suitable growth conditions due to the high acidity of the peat soils, it is the competitive advantage and can form species-poor bushes. It is still less demanding than the silver birch (Betula pendula ), which also spreads to many areas as a pioneer.
Autecology
Bog birch are resistant to winter frosts. At temperatures below -40 ° C convert them to the branches in strength to oil, heat is released. The leaves freeze until -6 ° C. In cold conditions that occur in the area of white bark ventilation cracks ( " Korkwarzen " ) are sealed and thus increase the resistance to frost. The downy birch is considered the northernmost tree species in Europe. A winter average temperature of -33 ° C does not cause loss of vitality. The frost hardiness remains despite intermediate heating (up to 18 ° C) the entire winter stable.
In northern Europe, the weißfärbende effect of the beef ingredient betulin protects the thin bark bark before fire. Due to the low-lying in the spring sun and reflection from snow surfaces is dark bark would overheat and the cell division tissues are damaged.
The downy birch has a shallow rooting heart root system. There is a lack well-developed horizontal roots; instead of a main root several different degrees vertically growing roots are formed on the rhizome with several up to 20 meters long lateral roots. Shallow roots are oriented primarily to the inclusion infiltrating rainwater. The downy birch has a high water flow rate. A mature birch can draw on a hot summer day up to 500 liters of water from the soil. The fine roots are surrounded by a dense network of living symbiotic fungi ( mycorrhiza ), which strongly favors the nutrient supply.
Synecology
For a number of phytophagous insects downy birch plays a crucial role. For example, suck some cicadas species exclusively ( monophagous 2nd degree ) to both downy birch as well as on silver birch. These are mainly species of the genus within the family of Oncopsis mask cicadas ( Macropsinae ).
The Fjell- birch
In the boreal north of Europe the Fjell- birch forest belt forms its own. The variable and taxonomically elusive clan was formerly mostly Betula pubescens subsp. tortuosa ( Ledeb. ) Nyman called this name is now used only for a spread in the Altai tribe. The most widely used name of the clan is Betula pubescens Ehrh. subsp. czerepanovii ( N.I.Orlova ) Hämet - Ahti. It is then considered subspecies of downy birch (Betula pubescens). The Fjell- birch differs from the typical subspecies of downy birch in different characteristics (eg leaf shape ), striking are the most crooked, winding stems and often multi-stemmed growth. The emergence of Fjell- birch is today mostly interpreted by introgressive hybridization with the dwarf birch (Betula nana ). Primary hybrids are triploid and occur rarely. By backcrossing with bog birches are multiform hybrid swarms, where there is additionally a partner and the silver birch is involved. This mechanism (which is quite common in the plant kingdom ), features the dwarf birch are crossed in bog birch populations and thus explain the diverse, ecologically plastic Nordic populations.
The Fjell- birch forms the north its own forest belt and various natural forest communities (reviewed in ). They form the natural tree line, which is located in central Norway at altitudes of about 1,200 meters, near the coast at about 600 meters in Scandinavia. In Iceland it is the only forest -forming tree species at all. To the east, under kontinentalerem climate impact, the Fjellbirkenwälder be replaced by coniferous forests. Fjellbirkenwälder, especially in their lichen-rich education, are important feeding grounds for reindeer herds of the people of the seeds. For some time, encroachment of forests northward and uphill registered which may include several hundred meters in altitude. This can be convincingly interpreted as the impact of climate change, so that these have been often still primeval, economically low-value stocks now also subject to enhanced human influence.
Findings of this subspecies are also reported from the Alps (eg. , The actual status of these populations and their relationship to the Nordic Fjell- birch require but still to be clarified.
Use
Made of birch wood furniture is made.
Medicinal plant
The leaves of downy birch as well as the silver birch contain up to three percent flavonoids especially hyperoside, quercetin, quercitrin and Myricetingalaktosid, but also vitamin C, saponins and essential oils. The birch buds contain fat-soluble Flavonmethylether. Teas and juice from birch leaves cause an increased salt and water excretion. They are therefore used for irrigation therapy of renal, used to treat inflammation of the urinary tract and renal gravel. Traditionally birch leaves are used for their urate lowering effect in gout and rheumatic complaints or as an addition to the so-called Blutreinigungstees. The very young, fresh leaves can be eaten in spring salads. Hair lotions from extracts of birch leaves are effective against hair loss and dandruff.
Timber industry
Preferred uses in the timber industry, veneers in furniture and interior design. In addition to the imitation of precious woods such as walnut and cherry for style furniture. Furthermore, the wood for turnery and carving, as well as for sports equipment, musical instruments, brushes and brush handles and as an industrial wood for particleboard and fiberboard used. In Scandinavia, it is of great importance for plywood.
System
The species name Betula pubescens was first published in 1790 by Jakob Friedrich Ehrhart in Contributions to Natural History, 5, pp. 160.
There are three subspecies of Betula pubescens Ehrh. (Selection):
- Betula pubescens L. subsp. pubescens: syn: Betula alba L.
- Betula pubescens subsp. tortuosa ( Ledeb. ) Nyman: syn: Betula czerepanovii NIOrlova, Betula pubescens subsp. czerepanovii ( NIOrlova ) Hämet - Ahti, Betula tortuosa Ledeb.
There are four varieties:
- Betula pubescens var glabrata Wahlenb. , Fl. Carpat. Princ: 306 (1814), . Carpathian birch
- Betula pubescens var golitsinii ( VNVassil. ) Tzvelev, Novosti Sist. Vyssh. Rest. 34: 61 (2002)
- Betula pubescens L. var pubescens; Ordinary downy birch
- Betula pubescens var pumila (L.) Govaerts, World Checklist Seed Pl 2 (1): 10 (1996 )