Alder

Alder is the common name of a genus of flowering plants (Alnus) belonging to the birch family (Family Betulaceae). The genus comprises about 30 species of monoecious trees and shrubs, few reaching large size, distributed throughout the North Temperate Zone and in the Americas also along the Andes southwards to Argentina.

Description

Alder leaves are deciduous (not evergreen), alternate, simple, and serrated. The flowers are catkins with elongate male catkins on the same plant as shorter female catkins, often before leaves appear; they are mainly wind-pollinated, but also visited by bees to a small extent. They differ from the birches (Betula, the other genus in the family) in that the female catkins are woody and do not disintegrate at maturity, opening to release the seeds in a similar manner to many conifer cones.

The largest species are Red Alder (A. rubra) on the west coast of North America and Black Alder (A. glutinosa), native to most of Europe and widely introduced elsewhere, both reaching over 30 m. By contrast, the widespread Green Alder (A. viridis) is rarely more than a 5 m tall shrub.

Ecology

Alder leaves and sometimes catkins are used as food by numerous butterflies and moths; see List of Lepidoptera that feed on alders.

A. glutinosa and A. viridis are classed as environmental weeds in New Zealand.

Nitrogen fixation

Alder is particularly noted for its important symbiotic relationship with Frankia alni, actinomycete filamentous nitrogen-fixing bacterium. This bacterium is found in root nodules which may be as large as a human fist, with many small lobes and light brown in appearance. The bacterium absorbs nitrogen from the air and makes it available to the tree. Alder, in turn, provides the bacterium with carbon, which it produces through photosynthesis. As a result of this mutually-beneficial relationship, alder improves the fertility of the soils where it grows, and as a pioneer species, it helps provide additional nitrogen for the successional species which follow.

Word origin

The common name alder is derived from an old Germanic root, also found to be the translation of the Old French "verne" for alder or copse of alders. The botanic name Alnus is the equivalent Latin name. Both the Latin and the Germanic words derive from the Proto-Indo-European root el-, meaning "red" or "brown", which is also a root for the English words elk and another tree: elm, a tree distantly related to the alders. In Celtic mythology, Bran the Blessed is associated with the alder tree "The Alder deity is considered to be Bran the Blessed, god of the Underworld. He was also known as the god of Prophecy, Arts, War and Writing. With the size of a giant, it was impossible for Bran to fit in a house or in a boat.

Fearne is also the third letter in the Ogham alphabet, meaning alder in this form of Celtic.

Use by humans

, Austria.]] Alder catkins are edible and high in protein. Although they are reported to have a bitter and unpleasant taste, they are best remembered for survival purposes. Alder wood is also commonly used to smoke various food items.

Alder bark contains the anti-inflammatory salicin which is metabolized into salicylic acid in the body. Native Americans used Red Alder bark (Alnus rubra) to treat poison oak, insect bites, and skin irritations. Blackfeet Indians used an infusion made from the bark of Red Alder to treat lymphatic disorders and tuberculosis. Recent clinical studies have verified that red alder contains betulin and lupeol, compounds shown to be effective against a variety of tumors.

Alder is illustrated in the coat of arms for the Austrian town of Grossarl.

Electric guitars, most notably the Fender Stratocaster and Fender Telecaster have been built with alder bodies since the 1950s. Alder is appreciated for its bright tone, and has been adopted by many electric guitar manufacturers.

Classification

The genus is divided into three subgenera:

Subgenus Alnus. Trees. Shoot buds stalked. Male and female catkins produced in autumn (fall) but staying closed over winter, pollinating in late winter or early spring. About 15-25 species, including:

Alnus acuminata — Andean Alder. Andes Mountains, South America.

Alnus cordata — Italian Alder. Italy.

Alnus cremastogyne

Alnus firma — Kyūshū (Japan)

Alnus glutinosa — Black Alder. Europe.

Alnus incana — Grey Alder. Eurasia.

*Alnus hirsuta (A. incana subsp. hirsuta) — Manchurian Alder. Northeastern Asia, and central Asia in mountains.

*Alnus oblongifolia (A. incana subsp. oblongifolia) — Arizona Alder. Southwestern North America.

*Alnus rugosa (A. incana subsp. rugosa) — Speckled Alder. Northeastern North America.

*Alnus tenuifolia (A. incana subsp. tenuifolia) — Thinleaf or Mountain Alder. Northwestern North America.

Alnus japonica — Japanese Alder. Japan.

Alnus jorullensis — Mexican Alder. Mexico, Guatemala.

Alnus mandshurica — Russian Far East, China, Korea.

Alnus matsumurae — Honshū (Japan).

Alnus nepalensis — Nepalese Alder. Eastern Himalaya, southwest China.

Alnus orientalis — Oriental Alder. Southern Turkey, northwest Syria, Cyprus.

Alnus pendula — Japan, Korea.

Alnus rhombifolia — White Alder. Interior western North America.

Alnus rubra — Red Alder. West coastal North America.

Alnus serrulata — Hazel alder, Tag Alder or Smooth alder. Eastern North America.

Alnus sieboldiana — Honshū (Japan).

Alnus subcordata — Caucasian Alder. Caucasus, Iran.

Alnus trabeculosa — China, Japan.

Subgenus Clethropsis. Trees or shrubs. Shoot buds stalked. Male and female catkins produced in autumn (fall) and expanding and pollinating then. Three species:

Alnus formosana — Formosan Alder Taiwan

Alnus maritima — Seaside Alder. East coastal North America, plus disjunct population in Oklahoma.

Alnus nitida — Himalayan Alder. Western Himalaya.

Subgenus Alnobetula. Shrubs. Shoot buds not stalked. Male and female catkins produced in late spring (after leaves appear) and expanding and pollinating then. One to four species:

Alnus viridis — Green Alder. Widespread:

*Alnus viridis subsp. viridis. Eurasia.

*Alnus viridis subsp. maximowiczii (A. maximowiczii). Japan.

*Alnus viridis subsp. crispa (A. crispa). Northern North America.

*Alnus viridis subsp. sinuata (A. sinuata, Sitka Alder or Slide Alder). Western North America, far northeastern Siberia.

References

Further reading

Chen, Zhiduan and Li, Jianhua (2004). Phylogenetics and Biogeography of Alnus (Betulaceae) Inferred from Sequences of Nuclear Ribosomal DNA ITS Region. International Journal of Plant Sciences 165: 325–335.

External links

Flora Europaea: Alnus

Flora of Bolivia: Alnus

Flora of China: Alnus

Flora of North America: Alnus

Flora of Pakistan: Alnus

Category:Betulaceae