Ольха чёрная: описание и свойства

Species of flowering plant in the birch family Betulaceae

Alnus glutinosa, the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium sized, short lived tree growing to a height of up to 30 metres (98 feet). It has short stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone like and the seeds are dispersed by wind and water. The common alder provides food and shelter for wildlife, with a number of insects, lichens and fungi being completely dependent on the tree. It is a pioneer species, colonising vacant land and forming mixed forests as other trees appear in its wake. Eventually common alder dies out of woodlands because the seedlings need more light than is available on the forest floor. Its more usual habitat is forest edges, swamps and riverside corridors. The timber has been used in underwater foundations and for manufacture of paper and fibreboard, for smoking foods, for joinery, turnery and carving. Products of the tree have been used in ethnobotany, providing folk remedies for various ailments, and research has shown that extracts of the seeds are active against pathogenic bacteria.

A. glutinosa is a tree that thrives in moist soils, and grows under favourable circumstances to a height of and exceptionally up to Young trees have an upright habit of growth with a main axial stem but older trees develop an arched crown with crooked branches. The base of the trunk produces adventitious roots which grow down to the soil and may appear to be propping the trunk up. The bark of young trees is smooth, glossy and greenish brown while in older trees it is dark grey and fissured. The branches are smooth and somewhat sticky, being scattered with resinous warts. The buds are purplish brown and have short stalks. Both male and female catkins form in the autumn and remain dormant during the winter. The leaves of the common alder are short stalked, rounded, up to long with a slightly wedge shaped base and a wavy, serrated margin. They have a glossy dark green upper surface and paler green underside with rusty brown hairs in the angles of the veins. As with some other trees growing near water, the common alder keeps its leaves longer than do trees in drier situations, and the leaves remain green late into the autumn. As the Latin name glutinosa implies, the buds and young leaves are sticky with a resinous gum. The species is monoecious and the flowers are wind pollinated; the slender cylindrical male catkins are pendulous, reddish in colour and long; the female flowers are upright, broad and green, with short stalks. During the autumn they become dark brown to black in colour, hard, somewhat woody, and superficially similar to small conifer cones. They last through the winter and the small winged seeds are mostly scattered the following spring. The seeds are flattened reddish brown nuts edged with webbing filled with pockets of air. This enables them to float for about a month which allows the seed to disperse widely.

The common alder is native to almost the whole of continental Europe (except for both the extreme north and south) as well as the United Kingdom and Ireland. In Asia its range includes Turkey, Iran and Kazakhstan, and in Africa it is found in Tunisia, Algeria and Morocco. It is naturalised in the Azores. It has been introduced, either by accident or by intent, to Canada, the United States, Chile, South Africa, Australia and New Zealand. European alder does not usually grow in areas where the average daily temperature is above freezing for longer than six months; its range is mainly restricted in Scandinavia, but it also habitats other regions. The common alder is susceptible to Phytophthora alni, a recently evolved species of oomycete plant pathogen probably of hybrid origin. This is the causal agent of phytophthora disease of alder which is causing extensive mortality of the trees in some parts of Europe. The symptoms of this infection include the death of roots and of patches of bark, dark spots near the base of the trunk, yellowing of leaves and in subsequent years, the death of branches and sometimes the whole tree. Taphrina alni is a fungal plant pathogen that causes alder tongue gall, a chemically induced distortion of female catkins. The gall develops on the maturing fruits and produces spores which are carried by the wind to other trees. This gall is believed to be harmless to the tree. Another, also harmless, gall is caused by a midge, Eriophyes inangulis, which sucks sap from the leaves forming pustules. and is associated with over 140 species of plant eating insect. Some 47 species of mycorrhizal fungi have been found growing in symbiosis with the common alder, both partners benefiting from an exchange of nutrients. As well as several species of Naucoria, these symbionts include Russula alnetorum, the milkcaps Lactarius obscuratus and Lactarius cyathula, and the alder roll rim Paxillus filamentosus, all of which grow nowhere else except in association with alders. In spring, the catkin cup Ciboria amentacea grows on fallen alder catkins.

Pollen from the common alder, along with that from birch and hazel, is one of the many sources of tree pollen allergy. As the pollen is often present in the atmosphere at the same time as that of birch, hazel, hornbeam and oak, and they have similar physicochemical properties, it is difficult to separate out their individual effects. In central Europe, these tree pollens are the second most common cause of allergic conditions after grass pollen.

The common alder is used as a pioneer species and to stabilise river banks, to assist in flood control, to purify water in waterlogged soils and to moderate the temperature and nutrient status of water bodies. It can be grown by itself or in mixed species plantations, and the nitrogen rich leaves falling to the ground enrich the soil and increase the production of such trees as walnut, Douglas fir and poplar on poor quality soils. Although the tree can live for up to 160 years, it is best felled for timber at 60 to 70 years before heart rot sets in. On marshy ground it is important as coppice wood, being cut near the base to encourage the production of straight poles. It is capable of enduring clipping as well as marine climatic conditions and may be cultivated as a fast growing windbreak. In woodland natural regeneration is not possible as the seeds need sufficient nutrients, water and light to germinate. Such conditions are rarely found at the forest floor and as the forest matures, the alder trees in it die out. The species is cultivated as a specimen tree in parks and gardens, and the cultivar 'Imperialis' has gained the Royal Horticultural Society's Award of Garden Merit.

The wood is soft, white when first cut, turning to pale red; the knots are attractively mottled. The timber is not used where strength is required in the construction industry, but is used for paper making, the manufacture of fibreboard and the production of energy. The wood is used in joinery, both as solid timber and as veneer, where its grain and colour are appreciated, and it takes dye well. As the wood is soft, flexible and somewhat light, it can be easily worked as well as split. It is also valued in turnery, carving, furniture making, window frames, clogs, toys, blocks, pencils and bowls. It exhibits a balanced, even tone with a good mid midrange projection making it suitable for a wide variety of musical applications. It's relatively lightweight, easy to work and sand, accepts glue, stain, paint and finish very well and is inexpensive. All this has made it a favourite of large factories mass producing instruments. Fender has been continuously and uninterruptedly using Alder to make electric guitars since 1956. Depending on the mordant and the methods used, various shades of brown, fawn, and yellowish orange hues can be imparted to wool, cotton and silk. Alder bark can also be used with iron sulphate to create a black dye which can substitute for the use of sumach or galls. The Laplanders are said to chew the bark and use their saliva to dye leather. The shoots of the common alder produce a yellowish or cinnamon coloured dye if cut early in the year. Other parts of the tree are also used in dyeing; the catkins can yield a green colour and the fresh cut wood a pinkish fawn colour.

It is also the traditional wood that is burnt to produce smoked fish and other smoked foods, though in some areas other woods are now more often used. It supplies high quality charcoal. rhododendrin {3 (4 hydroxyphenyl) l methylpropyl β D glucopyranoside} and (penta 2,3 dienedioic acid). Alnus glutinosa is planted on semi coke dumps as part of environmental restoration projects because it encourages other plants to grow.