Betula nana

Dwarf Birch (Betula nana )

The dwarf birch (Betula nana ), also called Polar birch, is a up to one meter high dwarf shrub of the birch family ( Betulaceae ).

Features

The deciduous, branchy dwarf shrub ( Nanophanerophyten ) has horizontal or ascending branches and reaches into stormy cold layers in buschartigem growth only heights between 0.2 m ( lying on the ground ) to 0.5 m, in sheltered areas mostly as single or in small groups standing trees 0.5 to about 1.0 meters. The bark is dark gray. The branches are at first tomentose, later glabrous and colored dark brown.

The short- stalked leaves are alternate and almost circular with a diameter of about 1 centimeter. You are bald, roughly notched the top being dark green. Under hand, they are brighter and network annoying. After the expulsion of these are a bit sticky, highly colored golden yellow to deep crimson in autumn.

They are monoecious getrenntgeschlechtig ( monoecious ). The flowers are grouped in upright spherical to elongated kitten. The male catkins are 0.5 to 1.5 cm long with yellow stamens. The female catkins are light brown and are 7-10 mm long.

The flowering period is from April to May

Dissemination

The dwarf birch is used in two subspecies on the northern hemisphere arctic - alpine. In the arctic tundra their range extends as far as the 80th degree of latitude, the closed circulation area ranges ranging from Scotland ( there usually was forming) and Scandinavia Svalbard east to Siberia, west via Iceland and Greenland to the Baffin Island in northern Canada. As Glazialrelikt she has occasionally survived in bogs of more southerly regions temperate zone. While the subspecies Betula nana ssp. nana is spreading eastward across the Atlantic to Central Siberia to Betula nana ssp limited. exilis on the Asian and North American regions of West Siberia to Canada.

In Central Europe it is isolated in the North German lowlands, in the Harz Mountains, the Bohemian Forest and the Ore Mountains, and in the foothills. In Austria it is also very rare in Lower Austria, Styria, Carinthia, Tyrol and Salzburg encountered. In Vorarlberg and Upper Austria it was extinct, but has settled from the Salzburg part of Ibmer Moores again.

The locations are in Central Europe waterlogged peat soils of high and low marshes, but also bog meadows and edges of alder swamps preferred.

Endangering

This species is protected in Austria and Germany and is listed in the Red List of Threatened Species. In Austria it is threatened in the western Alps and the northern Alpine foreland of extinction.

Others

Prior to the post-glacial reforestation of Central Europe developed between the Nordic ice stage and the European high mountains, a wide belt as dwarf birch on the tundra. Later, this area of ​​distribution has split into sub- areas.