SOS Forests

The Mystery of the Older Cohort

When I began SOS Forests in Sept. 2005, this is one of the first photos I posted:

It is not a particularly artistic shot, but it is illustrative of the mystery of the older cohort. The picture is of the East Fork of the Hood River about 6 or 7 miles south of the community of Mt. Hood. The forest pictured is typical of the slopes in the upper watershed.

If you look carefully, you will notice there are two distinct cohorts. The older trees are ponderosa pines ranging from 150 to 350+ years old. They are taller and their tops are often broken. Up close they are much bigger in diameter than the younger cohort trees, which are mostly Douglas-fir, grand fir, and western larch. The younger trees range from 25 to 100 years old.

That presents a mystery: why was this forest dominated by ponderosa pine for 200+ years with very few of the other species present? Is it because the other species wouldn’t grow there due to climate or soils?

No, the soils and climate are just the same as they were. The other species grow just fine there. In fact, they out-compete the ponderosa pine in the younger cohort. After a stand-replacing fire, all the species germinate, but the pines are soon overtopped by the others. They get spindly and die in dense thickets.

But for some mysterious reason, there are few if any Douglas-fir, grand fir, and western larch in the older cohort. The older trees are almost pure ponderosa pine. Look carefully and you will see that. If you can’t see it, take my word for it; that’s the situation. The ponderosa dominate the older cohort, but not the younger one.

Here is a clue to help you solve the mystery. The Hood River Valley has been home to human beings for at least 9,000 years and probably longer. Behind the pictured ridge is Dog River. An ancient trail winds up Dog River and over the top into the Fifteen Mile Creek watershed. Fifteen Mile Creek flows east and then north, entering the Columbia just west of the Deschutes confluence. The Dog River trail was a major transportation/summer migration route from the Lower Hood River Valley into the higher Deschutes country.

There are Indian signs everywhere: the ancient trail, cedar groves, arrowheads, circles of rocks obviously placed by humans, rock pinnacles with pictographs, and rock outcrops on the ridgetop that were undoubtedly used as vantage points if not sacred prayer sites. Nine thousand years is a long time, plenty of time for people to have combed over every inch of that ridge and those rivers.

Did the Indians have anything to do with the ponderosa pine dominance? Surely they must have. The only way (without chainsaws) to create a pure ponderosa pine forest in that place is to burn it regularly. The burning had to be seasonal, frequent, and annual, or close to it.

That kind of fire could only have been anthropogenic (human-set). Lightning didn’t do it. Lightning is too irregular, infrequent, and occurs in the summer when the most destruction from fires happens. Lightning strikes the ridgetops anyway, not the canyon bottoms where the pine cohort is also dominant (the only places where pine does not dominate the older cohort is in the pocket groves of western red cedar along the rivers and creeks).

So that is the answer to the mystery. Indian burning provided the driver that gave rise to a nearly pure ponderosa pine forest in a habitat where otherwise Douglas-fir, grand fir, and western larch would have dominated.

Why did the Indians burn those hills? Ethno-ecologists have conjectured dozens of reasons: to promote ponderosa pine, a food plant with sweet cambium and edible nuts, to promote the grasses and berries below as food for themselves and for game, to prevent the catastrophic fires that arise from dense thickets of firs, to clear the land of obscuring vegetation so they might see their enemies, to drive game, to improve their chances of shooting game with arrows, to promote root crops like bitterroot and edible greens like lomatiums, to promote useful shoots and fibers for basketry, to protect the cedar groves from catastrophic fires, cedar providing their most valued fibers, building materials, canoes, art materials, utensils, and other uses, and etc.

It was the humans that engendered the old-growth. Without the Indian burning on a frequent schedule, thickets of firs arise. When those thickets burn, the fires kill all the trees. Brush results, not forest. Infrequent fires lead to short-lived trees, not old-growth.

Look at the picture. The only old-growth trees are the ponderosa pines. The Douglas-firs, grand firs, and western larches will never survive to old ages. There are no old Douglas-firs, grand firs, and western larches there now; there is no reason to believe that those species will ever be components of an old-growth forest in that environment.

Just to be clear about it, the hillside in the picture has never been logged. If it had been logged, the old pines would have been the first to go. A 150 years ago when the Euro-American pioneers entered Hood River Valley, they did log. They logged yellow pine. There were few Douglas-firs of decent size to log. That has changed, and plenty of Douglas-firs, grand firs, and western larches have been logged in the Hood River Valley and surrounding hills over the last 50 years.

The hillside in the picture was too difficult to get to compared to easier spots, so it was left. Now it is preserved in the View Corridor. Preserved is not the right word, because it actually is primed to burn in a catastrophic fire someday. That fire will kill the older cohort pines, which are dying out now anyway from the moisture competition the thicket of other species inflicts.

If we want to truly protect and preserve old-growth, we are going to have to replicate some of the Indian practices. But first we need to rid the hillside of most of the Douglas-firs, grand firs, and western larches. We need to open that forest up, select for ponderosa pines, and burn it on a regular, seasonal basis.

While we’re at it, we might as well restore the ancient trails, cedar groves, and historical use sites. Much of the old trail has been eradicated by a mountain bike trail established by the USFS. It is a travesty, a vandalism of history, in my opinion.

Restoration forestry is necessary to save the old-growth and to preserve an ancient history of 9,000+ years vintage. There is no other way. Current uses and the abuses of un-management are killing the old trees and erasing the history from the landscape. Surely we can do better than that.