Alnus

Alder forest in Helsinki.

Alnus is a genus of trees in the family Betulaceae. It contains thirty species of monoecious trees and shrubs (very few of which reach great size), called alders, distributed throughout the world. They have ovate leaves with a toothed or serrated edge. The flowers are in the form of catkins, the male elongated and the female short, both on the same plant.

Taxonomy

The genus was described by Philip Miller and published in The Gardeners Dictionary...Abridged...fourth edition vol. 1. 1754. The type species is: Alnus glutinosa (L.) Gaertner

Etymology

Alnus: Classical Latin generic name for this genus.

Classification

The genre is divided into three subgenres:

Subgenus Alnus. Trees. Male and female catkins produced in the fall, but remain closed through the winter, pollinating in late winter or early spring. About 15-25 species, including:

• Alnus acuminata Humb., Bonpl. & Kunth. Cordillera de los Andes, South America.
• Alnus cordata Desf. Italy
• Alnus cremastogyne Burk.
• Alnus signs Sieb fakeZucc; "Yashabushi". Kyūshū (Japan)
• Alnus glutinosa (L.) Gaertner; Common Aliso, Black Aliso, Aliso par excellence in Europe, Alisa. European species.
• Alnus incana (L.) Moench; Grey Aliso. Eurasia. There is a variety especially appreciated for the gardens for their yellow foliage, the Alnus incana 'Aurea'Gold Aliso.
  • Alnus hirsuta (A. Incana subsp. hirsuta). Northeast Asia, and Central Asia in the mountains.
  • Alnus oblongifolia (A. Incana subsp. oblongifolia). Southwest of North America.
  • Alnus roar (A. Incana subsp. roaring). Northeast America.
  • Alnus tenuifolia (A. Incana subsp. tenuifolia). Northwest of America.
• Alnus japonica (Thunb.) Steud. Japan
• Alnus jorullensis Humb., Bonpl. & Kunth. Mexico, Guatemala.
• Alnus mandshurica (Call.) Hand. Far East Russian, China, Korean Peninsula.
• Alnus matsumurae Call.; "Yahazu-han-no-ki." Honshū, Japan.
• Alnus nepalensis D. Don. Eastern Himalaya, southwest of China.
• Alnus orientalis Decaisne. South Turkey, northwest of Syria, Cyprus.
• Alnus pendula Matsumura: "Himeyashabushi". Japan, Korean peninsula.
• Alnus rhombifolia Nutt; White Aliso. West American interior.
• Alnus rubra Bong; Red Aliso. West coast of North America.
• Alnus serrulata (Aiton) Willd. East of America.
• Alnus sieboldiana Matsum. Honshū, Japan.
• Alnus subcordata C. A. Meyer. Caucasus, Iran.
• Alnus trabeculosa Handel-Mazzet "Sakuraba-hannoki". China, Japan.

Subgenus Clethropsis. Trees or shrubs. Male and female catkins produced in autumn, expanding and pollinating then. Three species:

• Alnus formosana Mak.
• Alnus maritima Nutt. East coast of North America, plus an isolated population in Oklahoma.
• Alnus nitida (Spach) Endl. Western Himalayas.

Subgenus Alnobetula. Shrubs. Male and female catkins produced in late spring (after leaves appear) and expand and pollinate then. From one to four species:

• Alnus viridis DC; Green Aliso. Subspecies:
  • Alnus viridis subsp. viridis. Eurasia.
  • Alnus viridis subsp. maximowiczii (A. maximowiczii). Japan.
  • Alnus viridis subsp. crispa (A. crispa). North America.
  • Alnus viridis subsp. sinuata (A. sinuata). West America, northeast Siberia.

Ecology

Alders are often found near streams, rivers, and wetlands. Sometimes, where the prevalence of alders is particularly prominent, they are referred to as alders. In the Pacific Northwest of North America, the white alder (Alnus rhombifolia), unlike other northwestern alders, has an affinity for hot, dry climates, where it grows along watercourses, such as in lower rivers. Columbia, east of the Cascades, and the Snake River, including Hells Canyon.

Numerous butterflies and moths use the leaves and sometimes the catkins of the alder for food.

A. glutinosa and A. viridis are classified as environmental weeds in New Zealand. The leaves and especially the roots of alders are important to the ecosystem because they enrich the soil with nitrogen and other nutrients.

Nitrogen fixation and succession of forest species

Alder stands out especially for its important symbiotic relationship with Frankia alni, a filamentous, nitrogen-fixing actinomycete bacterium. This bacterium is found in root nodules, which can be as large as a human fist, with many small, light brown lobes. The bacteria absorb nitrogen from the air and make it available to the tree. The alder, in turn, provides the bacteria with sugars, which are produced by photosynthesis. As a result of this mutually beneficial relationship, alder improves the fertility of the soil where it grows and, as a pioneer species, helps provide additional nitrogen to successional species that follow.

A red alder seed is a tiny samara like all alders

Due to its abundance, red alder contributes large amounts of nitrogen to enrich forest soils. Red alder stands have been found to contribute between 130 and 320 kilograms per hectare (120 to 290 pounds per acre) of nitrogen to the soil annually. From Alaska to Oregon, Alnus viridis subsp. sinuata (A. sinuata, Sitka alder or slip alder), is characteristic of cool, gravelly places at the foot of retreating glaciers. Studies show that Sitka alder, a bushier variety of alder, adds nitrogen to the soil at an average rate of 60 kg/ha (54 lb/acre) per year, helping to convert barren glacial terrain into soil capable of support a coniferous forest. Alders are usually one of the first species to colonize areas affected by floods, gales, fires, landslides, etc. Alder forests often serve as natural fire breaks, as these broad-leaved trees are much less flammable than conifers. Their foliage and litter do not carry fire well, and their thin bark is tough enough to protect them from light surface fires. In addition, the light weight of the alder seeds -which are 1.5 million per kilo or 680,000 per pound- allows their easy dispersal by the wind. Although it outperforms coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) for the first 25 years, it is highly shade intolerant and rarely lives more than 100 years. The red alder is the largest alder in the Pacific Northwest and the most abundant and commercially important broadleaf tree on the Northwest Coast. Red alder groves 10 to 20 inches in diameter intersperse with young Douglas-fir forests west of the Cascades and reach a maximum height of 100 to 100 feet in about 60 years, after which they are affected by rot. of the heart (Heart rot). Alders contribute greatly to creating favorable conditions for the giant conifers that replace them.

Uses

Shield with alder from the town of Grossarl, Austria.

The catkins of some alder species are edible and can be high in protein. They are said to have a bitter and unpleasant taste, making them more useful for survival. The wood of some species of alder is often used to smoke various foods, including coffee, salmon, and other shellfish.

Most of the pilings that form the foundations of Venice were made from alder.

Alder bark contains salicin, an anti-inflammatory that is metabolized by the body into salicylic acid. Red alder (Alnus rubra) bark is used by some Native American cultures to treat oak poisoning, insect bites, and skin irritations. Blackfoot Indians have traditionally used an infusion of red alder bark to treat lymphatic disorders and tuberculosis. Recent clinical studies have found that red alder contains betulin and lupeol, compounds that have been shown to be effective against various tumors.

The inner bark of the alder, as well as that of the red dogwood or chokecherry, is used by some indigenous peoples of the Americas in smoking mixtures, known as kinnikinnick, to enhance the flavor of the bearberry leaf.

Alder appears on the coat of arms of the Austrian city of Grossarl.

Electric guitars, especially those made by Fender Musical Instruments Corporation, have been built with alder bodies since the 1950s. Alder is prized for its tone, which is considered firm and balanced, especially in comparison to mahogany, and has been adopted by many electric guitar manufacturers.^{[citation needed]}

As a hardwood, alder is used in the manufacture of furniture, cabinets, and other joinery products.

Alder's bark and wood (like those of oak and chestnut) contain tannin and are traditionally used to tan leather.

You can also extract a red dye from the outer bark and a yellow dye from the inner bark.