Local names:
English (Western slider,red alder,Pacific coast alder,Oregon alder,alder), French (aune rouge), German (Rot-Erle), Italian (ontano rosso), Spanish (aliso colorado), Trade name (red alder)
Alnus rubra is a medium-sized tree to 16-20 m, but may reach 40 m tall and DBH up to 1 m; bark smooth, gray; crown pyramidal, branches pendulous. It grows multi-stemmed in riparian thickets, and single-stemmed in pure or forest stands. It forms an extensive root system. Leaves short petioled, alternate, ovate. Inflorescence a catkin. Staminate catkins occur in pendulous clumps, 2-3 cm when young and green in colour, turning to reddish brown and 7-8 cm when mature. Pistillate catkins are borne upright, 5-8 mm long and reddish green when receptive. Fruit a small hard cone. Seed a small winged nut, borne in pairs on the bracts of woody conelike strobili. Strobili 11-32 mm long, 8-15 mm wide. ‘Alnus’ is the classical Latin name of alder. The specific name ‘rubra’ means red.
Ecology
Red alder is a temperate species confined to the lowland Pacific coast region of North America from Alaska to central California, where it is the most common broadleaf tree. It occurs in humid to super humid temperate climates and tolerates wide fluctuations in temperature, ranging from a minimum of -18 to a maximum of approximately 38 deg C. Relatively shortlived, the species is an aggressive pioneer on disturbed sites.
Native range
Canada, United States of America
Tree management
A. rubra is a pioneer species intolerant of competition but capable of rapid juvenile growth. Young trees coppice vigorously from the stump especially if the timing of the cut is optimal. For short coppice and pulp-log rotations, estimated total stem yields are 17-21 cu m/ha/yr. Thinning to 4-5 m x 4-5 m ensures tree lean is minimized. A. rubra tends to become weedy in disturbed sites, inoculation with the fungus Nectria ditissima has been employed to control this tendency. The tree self-prunes.
Seed storage behaviour is orthodox. There is no loss in viability after 10 years hermitic air-dry storage at 2-5 deg C. A. rubra is a prolific and consistent producer of seed. Moderate seed crops are produced almost annually and large crops occur every 3-5 years. The seeds are very light, numbering 800 000-3 000 000/kg.
Red alder is a temperate species confined to the lowland Pacific coast region of North America from Alaska to central California, where it is the most common broadleaf tree. It occurs in humid to super humid temperate climates and tolerates wide fluctuations in temperature, ranging from a minimum of -18 to a maximum of approximately 38 deg C. Relatively shortlived, the species is an aggressive pioneer on disturbed sites.
A. rubra is most often propagated by natural regeneration or potted seedlings. Clear cutting and large group selection are feasible regeneration methods. Green wood cuttings from young trees can be readily rooted. It can also be propagated by layering.
The tree is used to rehabilitate infertile and industrially disturbed sites such as coal mine spoils in the USA, and areas of poor drainage.
Erosion control: It is used in stabilization of ditch banks.
The tree is used for firewood and has been considered for fuel to generate electricity. The wood has a calorific value of 4 600 kcal/kg and makes good charcoal.
Fibre: The wood is used in the production of fibre based products such as tissues and writing paper.
Timber: Wood moderately dense (specific gravity 0.33-0.48), fine and even textured; it is easy to work and stain. The wood is used for furniture, panelling and pulp.
Shade or shelter: A. rubra is planted as a wind and fire break.
Medicine: The methanol extract of the bark of A. rubra has shown antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Bacillus subtilis. Diarylheptanoid and its glycoside (oregonin) have been identified as the active ingredients.
Nitrogen fixing: The red alder has root nodules containing Actinomycetes that fix nitrogen, thus improving soils fertility.
Ornamental: Red alder is planted as an ornamental in Europe.
Soil improver: Its roots and leaf litter are high in nutrients and on decaying enhance soil structure and builds up organic fraction.