Black alder ( Alnus glutinosa ), immature catkins and old fruit clusters
The alder ( Alnus ) constitute a genus within the family of birch family (Betulaceae). The approximately 41 species are, with one exception, widespread in the northern hemisphere . There are three species native to Central Europe : the green , gray and black alder .
Alder species are deciduous, i.e. deciduous trees or shrubs . Depending on the alder species, a bark is formed or they are classified as periderm tree species; For example, the black alder ( Alnus glutinosa ) forms a deeply fissured, gray-black bark and the gray alder ( Alnus incana ) forms a gray-shiny peridermal surface.
Like all birch plants, the alder species are single-sexed ( monoecious ); the inflorescences of both sexes, called catkins , are formed on one specimen . There are only female or male flowers in the catkins. The male flowers sit in pairs and the female flowers in threes in the armpits of bracts . The alder species are the only deciduous trees in which the female catkins lignify and are consequently referred to as cones . Solitary winged or wingless nut fruits are formed.
Alder species form root nodules at their roots, symbiotically with nitrogen-fixing actinomycetes ( Frankia alni ), similar to the symbiosis of nodule bacteria and legumes . This symbiosis allows alders to live in places that are poor in nutrients. Alder trees can therefore afford to shed their leaves green; alder trees are often pioneer plants in locations that are without vegetation due to natural or human influence (for example, green alders are often pioneer plants after avalanches). They prepare the soil for other plants.
Gray and black alder ( Alnus incana and Alnus glutinosa ) grow mainly on the edges of waters or in wetlands. Very humid locations are often poor in nutrients; At these locations, the nitrogen fixation of the nitrogen- binding root nodules is the decisive reason why only alders thrive there. It is reported that up to 100 kg N / ha and year are added to the soil through the fallen leaves of the alder alone . The gray and black alders often act as bank protection against washout and are considered to be ecologically valuable.
Systematics and distribution
The genus Alnus was established in 1754 by the English botanist Philip Miller in The Gardeners Dictionary ... Abridged ... , 4th edition, Volume 1. Betula alnus var. Glutinosa L. was established as the lectotype taxon in 1958 by JJ Swart. Alnus Hill is a homonym . Synonyms for Alnus Mill. Are Betula-alnus Marshall , Semidopsis Zumagl. nom. superflat., Alnobetula (WDJKoch) Schur nom. superflat., Cremastogyne (HJPWinkl.) Czerep. , Duschkia Opiz , Alnaster Spach , Clethropsis Spach .
The approximately 41 species of alder, with the exception of the Andean alder ( Alnus acuminata ), which is native to the Andes of South America , occur exclusively in the northern hemisphere in Eurasia and North America . East of the 115th degree of longitude, however, no tree-like alders can be found in North America. Several species are native to East Asia.
The alder genus distinguishes around 35 species, which are divided into three sub-genera:
- Subgenus Alnobetula (WDJKoch) Peterm. : It contains species from North America and Eurasia .
- Subgenus Alnus : It contains species from Europe, East Asia and the New World.
- Subgenus Clethropsis (Spach) rule : It contains species from East Asia and the USA.
Here is the complete list of accepted species and natural hybrids according to the World Checklist of Selected Plant Families of the Royal Botanic Gardens in Kew :
- Alnus acuminata Kunth : One of the three subspecies occurs only in Mexico and the other two are distributed from Mexico to northern Argentina .
- Green alder ( Alnus alnobetula (Ehrh.) K. Koch , Syn .: Alnus viridis (Chaix) DC. ): The five subspecies thrive in the temperate and subarctic regions of the northern hemisphere.
- Alnus betulifolia G.Y.Li, ZHChen & DDMa : The species first described in 2019 occurs in the Chinese province of Zhejiang.
- Heart-leaved alder ( Alnus cordata (Loisel.) Duby ): It occurs only in southern Italy and northeastern Corsica .
- Alnus cremastogyne Burkill : It occurs in the Chinese provinces of Sichuan , Gansu , Guizhou , Shaanxi and Zhejiang .
- Alnus djavanshirii H.Zare : It wasfirst describedin 2012 from northern Iran .
- Alnus dolichocarpa H.Zare, Amini & Assadi : It was first described in 2012 from northern Iran.
- Alnus × elliptica Req. = Alnus cordata × Alnus glutinosa . It occurs in Italy.
- Alnus × fallacina Callier = Alnus incana subsp. rugosa × Alnus serrulata . It occurs in the northeastern United States.
- Alnus fauriei H.Lév. & Vaniot : It occurs in northern and central Honshu .
- Alnus ferdinandi-coburgii C.K. Schneid. : It occurs in the Chinese provinces of Yunnan , Guizhou and Sichuan.
- Alnus company Siebold & Zucc. : This endemic occurs only on the Japanese island of Kyushu .
- Alnus formosana (Burkill) Makino : It is only found in Taiwan .
- Black alder ( Alnus glutinosa (L.) Gaertn. ): The four subspecies occur from Europe to western Siberia and Iran.
- Alnus glutipes (Jarm. Ex Czerpek) Vorosch. : It occurs in Siberia.
- Alnus hakkodensis Hayashi : This endemic occurs only on the Japanese island of Honshu .
- Alnus × hanedae Sugimo. = Alnus firm × Alnus Sieboldiana . It occurs in Japan.
- Alnus henryi C.K. Schneid. : It occurs in Taiwan.
- Dyer's alder ( Alnus hirsuta (Spach) Rupr. , Syn .: Alnus incana subsp. Hirsuta (Spach) Á.Löve & D.Löve , Alnus sibirica (Spach) Turcz. Ex Kom. ): It comes from southern Siberia to Japan in front.
- Alnus × hosoii Mizush. = Alnus maximowiczii × Alnus pendula . It occurs in Japan.
- Gray alder ( Alnus incana (L.) Moench ): The four subspecies occur from Europe to western Siberia and Turkey and also in North America.
- Japanese alder ( Alnus japonica (Thunb.) Steud. ): It occurs from Russia's Far East to eastern China, to Japan, Korea and Taiwan.
- Andean alder ( Alnus jorullensis Kunth ): It occurs in two subspecies from Mexico to Honduras .
- Alnus lanata Duthie ex Bean : It occurs in Sichuan.
- Alnus lusitanica Vít, Douda & Mandák : It was first described in 2017 and occurs in Portugal and Spain .
- Alnus mairei H.Lév. : It occurs in Yunnan.
- Alnus manschurica (Callier) Hand.-Mazz. : It occurs from Russia's Far East to Korea and northern China.
- Alnus maritima (Marshall) Muhl. ex Nutt. : It occurs in the US states of Oklahoma , Georgia , Delaware and Maryland .
- Alnus matsumurae Callier : This endemic occurs only in northern and central Honshu .
- Maximowicz's Alder ( Alnus maximowiczii Callier , Syn .: Alnus alnobetula subsp. Maximowiczii (Callier) Chery ): It occurs from Russia's Far East to Japan and Korea.
- Alnus × mayrii Callier = Alnus hirsuta × Alnus japonica . It occurs from Russia's Far East to Japan and Korea.
- Alnus nepalensis D.Don : It occurs from the Himalayas to China.
- Alnus nitida (Spach) Endl. : It occurs from northern Pakistan to the western and central Himalayas
- Alnus oblongifolia Torr. : It occurs in the US states of Arizona , New Mexico and northern Mexico.
- Turkish alder ( Alnus orientalis Decne. ): It occurs from southeastern Turkey to Israel and northern Iran and also on Cyprus .
- Alnus paniculata Nakai : It occurs in Korea.
- Alnus × peculiaris Hiyama = Alnus firma × Alnus pendula . It occurs on the Japanese island of Kyushu .
- Alnus pendula Matsum. : It occurs on the Japanese islands of Honshu and Hokkaido .
- Alnus × pubescens exchange = Alnus glutinosa × Alnus incana . It occurs in Europe.
- White alder ( Alnus rhombifolia Nutt. ): It is found in the US states of Oregon , Washington , Montana , Idaho and California and also in northern Mexico's Baja California .
- Alnus rohlenae Vít, Douda & Mandák : It wasfirst describedin 2017 from the northwestern Balkan peninsula .
- Red Alder ( Alnus rubra Bong. ): It is common in North America from Alaska to California.
- Wrinkled alder ( Alnus rugosa (Du Roi) Spreng. , Syn .: Alnus incana subsp. Rugosa (Du Roi) RTClausen ). It is usually placed as a subspecies to the gray alder ( Alnus incana ).
- Alnus serrulata (Aiton) Willd. : It is common in North America from eastern Canada to the eastern and central United States.
- Alnus serrulatoides Callier : It occurs on the Japanese islands of Shikoku and in southern Honshu.
- Alnus Sieboldiana Matsum. : It occurs on the Japanese islands of Honshu, Shikoku and the Nansei Islands .
- Caucasian alder ( Alnus subcordata C.A.Mey. ): It occurs from southeastern Transcaucasia to Iran.
- Alnus × suginoi Sugim. = Alnus hirsuta × Alnus serrulatoides . It occurs in Japan.
- Alnus trabeculosa Hand .-- Mazz. : It occurs in China and on the Japanese island of Honshu.
- Alnus vermicularis Nakai : It occurs in Korea.
A horticultural hybrid is:
- Spaeth's alder or purple alder ( Alnus × spaethii Callier ) = Alnus japonica × Alnus subcordata
Wood and use
Alder wood is one of the medium-weight types of wood and is easy to work with, hardly cracks when drying, but is only moderately weather-resistant. In the past, alder wood charcoal was used to make gunpowder. Due to its toughness and its deformation-free drying, alder wood is often used in furniture construction as a substitute for cherry, walnut or mahogany wood. Refinements by z. B. Polishing or staining are possible when processing alder wood with smooth surfaces. In addition, this type of wood is often chosen for the construction of percussion instruments (e.g. rattle), stringed or plucked musical instruments.
The black alder can be grown for the production of energy wood or for the production of valuable wood. Alder wood production is a possibility to use nutrient-rich, rewetted fen sites and is therefore also a paludiculture .
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