Red Alder: Young Forest Community Members

Red alder (Alnus rubra) is a deciduous tree that grows abundantly in the Pacific Northwest. Their range spans between California and Alaska, and they grow particularly well in British Columbia’s climate. In the past this species was thought of as being over abundant, but recently people have begun to realize their value.

Photo by Rob Underhill: St. John Point Test Alders

Red alders grow in less desirable sites, such as areas with nutrient poor soils that other species would not be able to tolerate. They are considered a pioneer species because of their ability to grow in recently disturbed sites. Pioneer species, sometimes referred to as early seral stage species, typically grow and reproduce quickly, thriving in full sun and loose soils. Disturbed sites that have been cleared by natural processes such as flooding, landslide, fire, or by human disturbances such as logging, are excellent habitat for red alder.

Photo by Andrew Bluhm, Oregon State University: A stand of red alder trees in the Oregon Coast Range

Red alders improve and build soils, preparing the way for other native species. They are nitrogen fixers, meaning they can convert nitrogen from the atmosphere into a form available to plants. They can’t do this on their own, but have developed a partnership with a type of bacteria that does it for them. Because red alders are fast growing, and shoot up their canopies quickly, they provide shelter from extreme conditions for young slower growing conifers and prevent sun-loving exotic species from gaining a foothold.

Red alder is a relatively short-lived species. As the trees die and begin rotting, they provide excellent nesting habitat for birds. When eventually they fall and decompose on the forest floor, they contribute soil for healthy forests. The use of red alder in restoration projects is helping restore forest ecosystems back to healthy levels and paving the way for improved forest growth and diversity!

Photo by Rob Underhill: St. John Point Restoration Site

References

  1. Green Timbers Heritage Society. (n.d.). Red Alder – Fagales Betulaceae Alnus rubra. Retrieved from https://www.greentimbers.ca/vegetation-wildlife/vegetation/deciduous-trees/red-alder/
  2. Forest Stewardship Notes. (2018). Retrieved from https://foreststewardshipnotes.wordpress.com/2018/10/15/tree-profile-red-alder/

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