Alnus incana

Alnus incana
	Leaves of speckled alder
Conservation status
	; Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Fagales
Family:	Betulaceae
Genus:	Alnus
Subgenus:	Alnus subg. Alnus
Species:	A. incana
Binomial name
	Alnus incana; (L.) Moench
	Range map

Alnus incana, the grey alder or speckled alder, is a species of tree in the birch family, with a wide range across the cooler parts of the Northern Hemisphere.

Description

It is a small- to medium-sized tree 15–20 m (49–66 ft) tall with smooth grey bark even in old age, its life span being a maximum of 60 to 100 years. The leaves are matte green, ovoid, 5–11 cm (2–4+1⁄4 in) long and 4–8 cm (1+1⁄2–3+1⁄4 in) broad. The flowers are catkins, appearing early in spring before the leaves emerge, the male catkins pendulous and 5–10 cm (2–4 in) long, the female catkins 1.5 cm (5⁄8 in) long and one cm broad when mature in late autumn. The seeds are small, 1–2 mm (0.04–0.08 in) long, and light brown with a narrow encircling wing. The grey alder has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers, especially in the northern parts of its range. The wood resembles that of the black alder (Alnus glutinosa), but is somewhat paler and of little economic value.

Subspecies

There are four to six subspecies, some treated as separate species by some authors:

Alnus incana subsp. incana; grey alder — Northern Europe and northwestern Asia, and central and southern Europe in mountains, mainly in the regions of the Alps, Carpathians and the Caucasus
Alnus incana subsp. hirsuta (Spach) Á. & D.Löve (=A. hirsuta Spach); Manchurian alder — In mountains of Northeast Asia and Central Asia
Alnus incana subsp. kolaensis (N.I.Orlova) Á. & D.Löve. — Subarctic northeast Europe
Alnus incana subsp. oblongifolia (=Alnus oblongifolia); Arizona alder — Madrean Sky Islands of southwestern North America, in Arizona, New Mexico, and Northwestern Mexico
Alnus incana subsp. rugosa (Du Roi) R.T.Clausen (=A. rugosa Du Roi); speckled alder — Much of Canada below the tree line, and the Northeastern United States
Alnus incana subsp. tenuifolia (Nutt.) Breitung (=A. tenuifolia Nutt.); mountain alder, or thinleaf alder — Western North America, including New Mexico to California and Alaska;^[3]^[4]^[5] the roots have nitrogen fixing nodules.^[6]

A. incana subsp. incana range
A. incana subsp. rugosa range
A. incana subsp. tenuifolia range

Ecology

Alnus incana is a light-demanding, fast-growing tree that grows well on poorer soils. In central Europe, it is a colonist of alluvial land alongside mountain brooks and streams, occurring at elevations up to 1,500 metres (4,900 ft). However, it does not require moist soil, and will also colonize screes and shallow stony slopes. In the northern part of its range, it is a common tree species at sea level in forests, abandoned fields and on lakeshores. Several species of Lepidoptera use grey alder as a food plant for their caterpillars. See List of Lepidoptera that feed on alders. In the boreal forest area of Canada, A. incana is often associated with black spruce in the forest type termed black spruce–speckled alder.^[7] The larvae of the alder woolly sawfly sometimes cause considerable defoliation to the grey alder.^[8]

A. rugosa provides cover for wildlife, is browsed by deer and moose, and the seeds are eaten by birds.^[9]

Chemistry

Pedunculagin is an ellagitannin found in the Manchurian alder (A. hirsuta var. microphylla).^[10]

Uses

The tree is cultivated in parks and gardens. The cultivar 'Aurea', with green-gold leaves, has gained the Royal Horticultural Society's Award of Garden Merit.^[11]

It is sometimes used for afforestation on non-fertile soils which it enriches by means of nitrogen fixing bacteria in its root nodules.

The Zuni people use the bark of the tenuifolia subspecies to dye deerskin reddish brown.^[12]

The Ho-Chunk people eat the bark of the rugosa subspecies when their stomachs are "sour" or upset.^[13]

References

^ Shaw, K.; Roy, S. & Wilson, B. (2014). "Alnus incana". The IUCN Red List of Threatened Species. 208. IUCN. e.T63517A3125479. doi:10.2305/IUCN.UK.2014-3.RLTS.T63517A3125479.en.
^ Flora of North America 2009.
^ Jepson Flora Project (ed.). "Alnus incana subsp. tenuifolia". Jepson eFlora. The Jepson Herbarium, University of California, Berkeley. Retrieved January 28, 2013.
^ "Alnus incana ssp. tenuifolia". Calflora. Berkeley, California: The Calflora Database. Retrieved January 28, 2013.
^ "Alnus incana". Plants for a Future. Retrieved January 28, 2013.
^ Patterson, Patricia A. (1985). Field Guide to the Forest Plants of Northern Idaho (PDF). United States Department of Agriculture Forest Service. p. 34.
^ Hogan 2008.
^ Forest Health Conditions in Alaska—2003. DIANE Publishing. p. 59. ISBN 978-1-4289-6595-9.
^ Little, Elbert L. (1980). The Audubon Society Field Guide to North American Trees: Eastern Region. New York: Knopf. p. 363. ISBN 0-394-50760-6.
^ Lee, O.; Choi, M.; Ha, S.; Lee, G.; Kim, J.; Park, G.; Lee, M.; Choi, Y.; Kim, M.; Oh, C. H. (2010). "Effect of pedunculagin investigated by non-invasive evaluation on atopic-like dermatitis in NC/Nga mice". Skin Research and Technology. 16 (3): 371–377. doi:10.1111/j.1600-0846.2010.00443.x. PMID 20637007. S2CID 25752299.
^ "RHS Plantfinder - Alnus incana 'Aurea'". Royal Horticultural Society. 2012. Retrieved 5 January 2018.
^ Stevenson, Matilda Coxe (1915). "Ethnobotany of the Zuni Indians". SI-BAE Annual Report. 30: 80.
^ Kindscher, Kelly (1998). "Huron Smith's Ethnobotany of the Hocąk (Winnebago)". Economic Botany. 52 (4): 361. doi:10.1007/BF02862065. S2CID 20652394.