Posted: Tue Jan 29, 2013 8:34 am
by KoutaR

The Goat Marsh stand is stated by many authors as the most massive stand outside the redwoods. E.g. Forest Giants of the Pacific Coast by Van Pelt, p. 94: "Southwest of the mountain [Mt. St. Helens]... is another beautiful grove, which not only contains the tallest known living Abies, but also has the Pacific Northwest biomass record... excluding coast redwood stands."

Why are the coastal forests not as biomass-dense as some forests in the Cascades? There are better members in this forum to answer. I think one reason is that stand-replacing fires are very rare near coast due to the humid conditions. Consequently, dense Douglas-fir stands are much more rare and the main shade-tolerant species, western hemlock (Tsuga heterophylla) that is much smaller tree, occupies high proportions of the forests. Shrub cover is much denser, too, and may prevent dense stands of large species from being established. Note that Douglas-fir and noble fir (Abies procera) are long-lived pioneers; dense stands of these species are often even-aged and regenerated after stand-replacing disturbances. The dominant noble firs and Douglas-firs in the Goat Marsh stand have regenerated in approx. 1630-1655.

Another reason could be the commonness of tree falling winds along the coast.

Van Pelt tells about a dense 350-year-old Douglas-fir grove in the Olympics, called "Miracle Acre". It may be more massive than the Middle Santiam RNA stand but I haven't found any numbers.