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Alnus rubra, the red alder,USDA Plants Profile: Alnus rubra is a deciduous broadleaf tree native to western North America (Alaska, Yukon, British Columbia, Washington, Oregon, California, Idaho and Montana). Kew World Checklist of Selected Plant Families Biota of North America Program, 2013 county distribution map
Specimens can live to about 60 years of age before being seriously afflicted by heart rot.
In moist forest areas, Alnus rubra will Pioneer species a former burn or clearcutting, often preventing the establishment of . It is a prolific seed producer, but the small, wind-dispersed seeds require an open area of mineral soil to Germination, and so skid trails and other areas disturbed by logging or fire are ideal seedbeds. Such areas may host several hundred thousand to several million seedlings per hectare in the first year after landscape disturbance.
Twigs and buds of alder are only fair browse for wildlife, but deer and red deer browse the twigs in fall and twigs and buds in the winter and spring. Beaver occasionally eat the bark, though it is not a preferred species. Several eat alder seeds, notably common redpoll and pine siskin, and as do deer mouse. often feed on the leaves, but the trees usually recover within a year.
The tree hosts the nitrogen-fixing actinomycete Frankia in nodules on roots. This association allows alder to grow in nitrogen-poor soils, and makes the species an important early colonizer of disturbed forests and riparian areas. This self-fertilizing trait allows red alder to grow rapidly, and makes it effective in covering disturbed and/or degraded land, such as Mining spoils. Imported Red Alder has been found to be able to make successful associations with Frankia strains present in the UK. Alder leaves, shed in the fall, decay readily to form a nitrogen-enriched humus making the nitrogen available to other species.
Along stream banks, it is commonly associated with ( Salix spp.), red osier dogwood ( Cornus stolonifera), Oregon ash ( Fraxinus latifolia), and bigleaf maple ( Acer macrophyllum).
To the southeast of its range it is replaced by white alder ( Alnus rhombifolia), which is a tree of similar stature, but which differs in the leaf margins not being rolled under, lack of distinct lobes, and lack of membranous wings on seed margins. In the high mountains it is replaced by the smaller and more shrub-like Sitka alder ( Alnus viridis subsp. sinuata), and east of the Cascade Mountains by Grey Alder ( Alnus incana subsp. tenuifolia).
Alnus rubra are occasionally planted as and will do well in Swales, riparian areas, or on stream banks, in light-textured soils that drain well. Red alder does not thrive in heavy, wet clay soils. If planted domestically, alders should be planted well away from drainpipes, sewage pipes, and water lines, as the roots may invade and clog the lines.
The appearance of alder lumber ranges from white through pinkish to light brown, has a relatively soft texture, minimal grain, and has medium luster. It is easily worked, glues well, and takes a good finish.
As an "aggressive pioneer" that was freely able to rapidly colonise areas to the detriment of the more valuable conifer species, it was regarded for a long time as a weed and was neglected for its timber potential, however breeding programmes to improve stem form and timber quality are now underway.
Since most forest land in the Northwest is managed for conifer production, over of timberland are sprayed with annually in Oregon alone to control red alder and other competing hardwood species.Oregon Dept of Forestry 2014 Red alder's rapid early growth can interfere with establishment of conifer plantations. Herbicide spraying of red alder over large areas of coastal Oregon and Washington has resulted in a number of lawsuits claiming it has caused health problems, including and other human health effects.
In addition to adding soil nitrogen, rotations of red alder are used to reduce laminated root rot in Douglas-fir forests. Nurse stands of red alder may also reduce spruce weevil damage in Sitka spruce stands on the Olympic Peninsula. Alder continues to attract interest as log values approach and often exceed those of Douglas-fir. This interest is limited by red alder's total stand productivity, which is significantly lower than that of Douglas-fir and western hemlock.
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