''Alnus alnobetula'' is a common tree widespread across much of

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

, and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

.Kew World Checklist of Selected Plant Families
/ref> Many sources refer to it as ''Alnus viridis'', the green alder, but botanically this is considered an illegitimate name synonymous with ''Alnus alnobetula'' subsp. ''fruticosa''.

Description

It is a large

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

or small

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

tall with smooth grey bark even in old age. The

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

are shiny green with light green undersurfaces, ovoid, long and 2–6 cm broad. The

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s are

catkin A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind- pollinated ( anemophilous) but sometimes insect-pollinated (as in '' Salix''). It contains many, usually unisexual flowers, arra ...

s, appearing late in spring after the leaves emerge (unlike other alders which flower before leafing out); the male catkins are pendulous, 4–8 cm long, the female catkins 1 cm long and 0.7 cm broad when mature in late autumn, in clusters of 3–10 on a branched stem. The

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

s are small, long, light brown with a narrow encircling wing. The roots of ''Alnus viridis subsp. sinuata'' have

nitrogen-fixing Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

nodules. A study in Alaska showed that Sitka alder seedlings were able to invade coal mine spoils and can be used for

revegetation Revegetation is the process of replanting and rebuilding the soil of disturbed land. This may be a natural process produced by plant colonization and succession, manmade rewilding projects, accelerated process designed to repair damage to a la ...

and stripmine reclamation.

Distribution

There are four to six

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

, some treated as separate species by some authors: *''Alnus viridis'' subsp. ''viridis'' – Central

*''Alnus viridis'' subsp. ''suaveolens'' –

Corsica Corsica ( , , ; ; ) is an island in the Mediterranean Sea and one of the Regions of France, 18 regions of France. It is the List of islands in the Mediterranean#By area, fourth-largest island in the Mediterranean and lies southeast of the Metro ...

(endemic) *''Alnus viridis'' subsp. ''fruticosa'' – Northeast Europe, northern

, northwestern

*''Alnus viridis'' subsp. ''maximowiczii'' (''A. maximowiczii'') –

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

*''Alnus viridis'' subsp. ''crispa'' (''A. crispa'', mountain alder) – northeastern North America,

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

*''Alnus viridis'' subsp. ''sinuata'' (''A. sinuata'', Sitka alder or slide alder) – western North America, far northeastern Siberia ''Alnus viridis'' is classed as an environmental weed in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

Ecology

''Alnus viridis'' has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers. ''Alnus viridis'' is a light-demanding, fast-growing shrub that grows well on poorer soils. In many areas, it is a highly characteristic colonist of

avalanche An avalanche is a rapid flow of snow down a Grade (slope), slope, such as a hill or mountain. Avalanches can be triggered spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, othe ...

chutes in

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...

s, where potentially competing larger trees are killed by regular avalanche damage. ''A. viridis'' survives the avalanches through its ability to re-grow from the roots and broken stumps. Unlike some other alders, it does require moist soil, and is a colonist of

scree Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. The term ''scree'' is ap ...

s and shallow stony slopes. It also commonly grows on subarctic river gravels, particularly in northern

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

and

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, occupying areas similarly disrupted by ice floes during spring river ice breakup; in this habitat it commonly occurs mixed with shrubby

willow Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...

Uses

It is sometimes used for

afforestation Afforestation is the establishment of a forest or stand of trees in an area where there was no recent tree cover. There are three types of afforestation: natural Regeneration (biology), regeneration, agroforestry and Tree plantation, tree plan ...

on infertile soils which it enriches by means of its nitrogen-fixing nodules, while not growing large enough to compete with the intended timber crop. ''A. sinuata'' can add 20 kg of nitrogen per acre (50kg/hectare) per year to the soil. ''Alnus viridis'' leaves have been used in the traditional Austrian medicine externally or internally as tea for treatment of infections and fever.

References

External links

''Alnus viridis''
- information, genetic conservation units and related resources. European Forest Genetic Resources Programme (EUFORGEN) {{Taxonbar, from1=Q20720096, from2=Q163978 alnobetula Trees of Northern America Trees of Europe Trees of Asia Flora of the Alps Flora of the Carpathians Flora of Alaska Flora of Corsica