Tree rings can be counted when a recently cut tree is encountered in the forest. Trees may have been cut for harvest or thinning, or when a fallen tree is blocking a trail. 

The most obvious reason for us informal explorers to look at the rings is to get a sense of how old the trees are in that neck of the woods. Like people, the age of a tree cannot be judged simply by its size — there are too many variables. But generally, each ring (a light/dark pair) will represent one year of growth. The lighter, wider part is from the rapid warm season growth, and the dark, thinner part is from the winter.

Why would you want to know the age of a tree? Personally, I just can’t help myself. I count rings from some deep-seated curiosity, the way young kids eagerly explore what’s around the next bend in the trail. Maybe I just never grew up. 

​But the age of the trees also holds clues to the history of the forest and what stage of growth it’s in. That, in turn, is a clue to what kinds of other living things one might find in that forest. For example, if the forest is 30 or 40 years old and a fairly uniform stand of Douglas fir, it’s unlikely that a visitor will see eagles or hawks hanging out there. But you might see a barred owl. It’s also unlikely that one will find huckleberries and salal, or much of anything else alive between the trees. Note that a foot is a good way to establish the size of the log.

But if you count 80 or more rings on a recently cut tree that seems typical in that area, you’re probably also seeing various kinds of fallen, rotting wood on the ground — rotting wood that is home to a cornucopia of small animals and other life. You’ll also likely see some variation in the sizes and species of trees, and an abundance of other plants growing between the trees. If, however, you find a stand of trees 100+ years old that are also very uniform looking, then Dorothy, you’re not in the middle of the bell curve any more — you have a mystery on your hands. 

For example, I was on a tour of the Illahee Forest Preserve (Kitsap County, Washington), and the guide pointed out a tree that was over 500 years old. However, the tree was only about 6 inches in diameter, and its neighbors were bigger, but not even 50 years old. How did they know how old the tree was without cutting it down?

An auger-like corer can be screwed into the trunk of a tree to remove just a small core sample from the tree. Then the rings can be counted in this core. In the case of the small, old tree, the rings were so close together that a microscope was needed to count them.

The image above is not from the 500+ year old tree, but it is quite a bit older than the average trees found in our post-harvest lowland forests — but it’s not considered ancient.

​A third way to gauge the age of trees is to find a planning document for the forest you are in. The map below came from such a planning document and shows the ages of different stands of trees in 2015, when the map was made.

But that’s just a rough guide because in some of those stands I’ve seen recently cut trees that were considerably older than the age assigned to the stand.

from “Forest Stewardship Plan for the Ecological Restoration of Port Gamble Forest Heritage Park”, June 1, 2016

audience participation

There’s not the time or space in this article to tell the stories of all of the possible ring variations, but we’ll address some of these in future issues. In the meantime, keep your eyes peeled for extra-ordinary tree rings. If you see something remarkable, snap a photo and post it on Instagram with the #salishmag2 hashtag (Salish Magazine Issue #2). That’ll help give us fuel for future articles.