Fir WavesSometime around June of 2005, BobSmith noticed, in one of my photographs, a peculiar wavelike pattern of alternating bands of living and dead evergreens (spruce or fir, I wasn't sure which at the time). I also spotted it in some (but by no means all) of my other photos of New England evergreen forests.
I Googled around and discovered that the phenomenon is called "fir waves", and seems to exist only in New England, upstate New York, and Japan. You can also find proof in this album that they exist in Quebec [at least near the U.S. border]. In addition, Matthew Becker of BYU informed me by email (citing a 1999 paper in Acta Oecologica by Puigdefábregas et al.) that a similar phenomenon is present in evergreen beeches (Nothofagus) on Tierra del Fuego. Becker's own paper reviewing fir waves together with "ribbon forests" and "hedges" is now available online: Linear Forest Patterns in Subalpine Environments.
Matt Worster noticed that fir waves sometimes show up in satellite photos.
This album is dedicated to fir waves. Post your best fir wave photos here.
Note that a blowdown or stand of dead trees is not necessarily a fir wave. A wave, by definition, is a disturbance that propagates. That motion is not visible in a photo, but if you see alternating bands you're probably looking at a wave.
External LinksThis background info from an online ecology course nicely summarizes the classic 1976 paper by Sprugel about the causes of fir waves. See Linear Forest Patterns in Subalpine Environments for a review of more recent developments in the field.
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