Mark:
I don't have any reliable source for the age of the smaller redwoods on the hillsides in Humboldt State Park, but I would guess that they are comparably long-lived. One problem would be the effect of fire. Fires have in the past, before the area was settled by Europeans, burned in the bottomland forests. Now, I am making a guess, but they may have been much more devastating to the forests on the hillsides and ridges. So, if that is the case, any studies of the ages of the trees on the hillsides may not reveal the potnetial life span of those trees, which I believe are growing in a more mixed forest that includes madrone, tanoak and maybe some douglas fir. But it has been something like 50 years since I have hiked up onto one of those hillsides, and at the time I did not make a careful note of the associated species.
Anyway, the hillsides of the redwood forests in the more coastal areas, such as Prairie Creek State Park and other places, are completely different, and support very large redwoods. Humboldt Redwoods State Park is somewhat inland away from coastal fogs, and, I am guessing again, some of the rainfall. Hence the difference between the forest on the hillsides vs the bottomlands, which are essentially floodplains.
--Gaines
