Rees said his company uses Douglas fir because they provide solid, true material.
From the thenewstribune.com
White fir, Douglas fir, silver tip, cedar, pine, exotic true firs.
From the sacbee.com
True firs such as silver fir will decay far more rapidly than other species, as much as 5-6 percent a year and may be gone in 60 years or less.
From the sciencedaily.com
Favored woods, in order of rot-resistance, are White oak, Black locust, species of cedar and pine, true as well as African and Asian mahoganies, fir and spruce.