I’ve mentioned Dan Leen’s excellent web page before. When I was on Teredo N. with him I heard many excellent stories including how he came across a spectacular carved tree on Calvert Island, near Namu. Finally I get to see what he meant. This strikes me as the work of a trippy bush hippy (and maybe Dan himself, heh) more than a NW Coast thing, but it is fun nonetheless.
Incidentally, “Arborglyph” is a Frankenstein word melding Greek and Latin roots and should probably be replaced with “dendroglyph”, which is also easier to say.