Alnus viridis

Taxobox
name = Green Alder


image_width = 240px
image_caption = Green Alder "Alnus viridis" (foreground foliage)
regnum = Plantae
divisio = Magnoliophyta
classis = Magnoliopsida
ordo = Fagales
familia = Betulaceae
genus = "Alnus"
subgenus = "Alnobetula"
species = "A. viridis"
binomial = "Alnus viridis"
binomial_authority = (Chaix.) D.C.

"Alnus viridis" (Green Alder) is an alder with a wide range across the cooler parts of the Northern Hemisphere.

Description

It is a large shrub or small tree 3-12 m tall with smooth grey bark even in old age. The leaves are shiny green, ovoid, 3-8 cm long and 2-6 cm broad. The flowers are catkins, 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 seeds are small, 1-2 mm long, light brown with a narrow encircling wing.

Distribution

There are four to six subspecies, some treated as separate species by some authors:
*"Alnus viridis" subsp. "viridis". Central Europe.
*"Alnus viridis" subsp. "suaveolens". Corsica (endemic).
*"Alnus viridis" subsp. "fruticosa". Northeast Europe, northern Asia, northwestern North America.
*"Alnus viridis" subsp. "maximowiczii" ("A. maximowiczii"). Japan.
*"Alnus viridis" subsp. "crispa" ("A. crispa", Mountain Alder). Northeastern North America, Greenland.
*"Alnus viridis" subsp. "sinuata" ("A. sinuata", Sitka Alder or Slide Alder). Western North America, far northeastern Siberia.

Ecology

"A. viridis" has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers.

"A. 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 chutes in mountains, 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 not require moist soil, and is a colonist of screes and shallow stony slopes. It also commonly grows on subarctic river gravels, particularly in northern Siberia, Alaska and Canada, occupying areas similarly disrupted by ice floes during spring river ice breakup; in this habitat it commonly occurs mixed with shrubby willows.

Uses

It is sometimes used for afforestation 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 55 lbs of nitrogen per acre per year to the soil. [Ewing, Susan. The Great Alaska Nature Factbook. Portland: Alaska Northwest Books, 1996.]

Notes

References

* [http://rbg-web2.rbge.org.uk/cgi-bin/nph-readbtree.pl/feout?FAMILY_XREF=&GENUS_XREF=Alnus&SPECIES_XREF=viridis&TAXON_NAME_XREF=&RANK= Flora Europaea: "Alnus viridis"]
* [http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500041 Flora of North America: "Alnus viridis"]