https://www.fs.fed.us/database/feis/plants/tree/alnrub/all.html wrote: Generally, five types of red alder communities have been described:
(1) Upland, pure even aged stands of red alder, with a dense shrub
undergrowth dominated by salmonberry (Rubus spectabilis) or
elderberry (Sambucus melanocarpa), occurring within coniferous
(2) Upland mixed stands of red alder/other deciduous trees and
shrubs/conifers within coniferous forests less than 100 years
old, with red alder occurring as a dominant or codominant.
(3) Riparian red alder communities within coniferous forests.
(4) Mixed stands within deciduous riparian forests, red alder
occurring as codominant with black cottonwood (Populus trichocarpa)
and bigleaf maple (Acer macrophyllum).
(5) In swamps often occurring with, or codominant with, western
redcedar. In this type of community, red alder appears to be a