Remarkable, a fir log lying on the ground here would be unsalvageable in 3 months !Living here in Northern California relatively close to Mt. St. Helens in terms of timber distribution, I can say that the undisputed "word on the street" regarding Mt. St. Helen's windfall salvage timber is exactly as Smalser reported. It would be suitable for construction timber because it would be closed in. The current energy efficiency codes produce buildings so tight they'd probably float just fine! (A lot of new construction here is now wrapped in waterproof plastic Tyvek.) Little problem with "rot prone" timber in such applications. On the other hand, it is indisputable that the Mt. St. Helens Doug fir is of the "inland" rather than the "coastal" subspecies, and the differences in rot resistance between the two are well documented. And, as Bob said, the salvage windfall has been laying on the ground for decades now, in an area with high rain and snow fall rates and much of it was exposed to searing heat in the pyroclastic flows. Nobody seems to think it is worth much for boatbuilding timber.
On the other hand, there is reportedly some salvage harvested Alaska Yellow Cedar (now determined to actually be a true cypress) coming on the market that seems excellent. AYC is well known as a premiere planking species (very low movement, good decay resistance.) AYC is sensitive to climate change. As the climate has warmed in some areas, less snow stays on the ground. Without the snow layer to insulate the ground, the roots freeze and the trees die. (The species is not in any apparent danger of extinction, though. The forest just "moves" by reseeding in areas more favorable to its growth.) Studies done on AYC which has been standing dead for as much as 80 or 100 years shows that a remarkable percentage of this dead wood is perfectly fine for harvesting and milling. (Its age shows it wasn't because of THAT "global warming.") While the trees exhibit some deterioration on the surface, the extent being relative to the length of time they've been dead, the inner wood remains pristine.