Red alder: part of the streamside forest

Red Alder (Alnus rubra) is a common hardwood species that can be found growing along the west coast from Southern California to Northeast Alaska.

It does well in wet areas--it can even tolerate some flooding--and most commonly grows along the borders of steams or lakes. While this species can be found in pure stands, especially after a disturbance, it is more often a component of mixed forests, associated with trees such as Douglas-fir, black cottonwood, willow, Pacific dogwood, and redwood.

Red alder is a pioneer species, some might call it a weed, growing rapidly in disturbed areas such as clearcuts, burns, or along road cuts--anywhere with full sunlight and exposed soil.

After a disturbance, red alder quickly colonizes a site through its many wind-dispersed seeds. The trees are extremely intolerant of shade so only those that can stay above the canopy and retain access to sunlight survive. This prevents younger alder seedlings from becoming established, resulting in even-aged stands. In about 25 years, however, slower-growing conifers such as Douglas-fir begin to overtop the alders until few remain after 60 years.

One of the more intriguing attributes of red alder is its ability to fix atmospheric nitrogen through root nodules that contain a symbiotic nitrogen-fixing bacteria. This trait helps the tree grow in disturbed areas where it puts nitrogen back in the soil. A relatively short-lived tree, red alder prepares the soil for the next seral stage. In fact, it has been suggested that alder be planted as a rotation crop before growing conifers since conifers that come in under a red alder canopy show an increased growth rate. Douglas-fir grown with red alder also exhibits greater heights and diameters than those grown without.

Red alder is used for erosion control because of its ability to grow quickly and stabilize the soil on exposed sites while rehabilitating the soil through its dense litter layer and nitrogen fixation.

While its commercial value remains lower than that of conifers, red alder has a lot to recommend it. Wood from the tree is fine-grained, moderately dense, and uniform in color. It is valued in the production of furniture, cabinets, veneer and used in other wood products such as pallets, plywood, and paper. It is also an important firewood species.

Native Americans used the inner bark of red alder to produce a red dye used to dye fish nets, making them invisible to fish. The tree also contains medicinal properties including salicin, a chemical closely related to the active ingredient in aspirin. And, it is considered the best wood for smoking salmon.