There’s a red alder growing at the top of this hill. This one is alone. I’ve passed stands of them on the way up. A few stands have 50 or more growing together. Slender, clumped together in thickets, their smooth, gray-and-white mottled trunks stretch up into the canopy. Most of them are no bigger around than a person’s arm. They are young. Over the coming years, their numbers will be whittled down. The competition for sunlight, nutrients and space, will leave only a few where these many once stood. Anything that reaches 65-95 feet tall, will need a little elbow room.
Someone has carved initials into this lone alder, a jagged “BT”. The wound has healed. It isn’t deep. And, it doesn’t look harsher than the long, vertical gashes indicating some creature also used this alder for a scratching post. But, it makes me wonder when the infamous BT made his etching and how long this tree will bear his mark.
Alders are fast growing, and prolific, quick to take over a disturbed an area that may have been logged and once held a coniferous forest. Based on its size, I estimate this tree might be between 30 and 40 years old. At the top of this hill, I notice there also are thickets of bigleaf maples, thin ones, 8-20 inches in diameter, clustered in groups of 6-16. There aren’t many large trees here. It makes me think the hillside was cleared in recent history and these trees grew up when the area went unused.
Stand of bigleaf maples
This is one of Oregon’s oldest settled areas. The “end” of the Oregon Trail is not far from here, as well the site of a major water portage and mill operation. In fact, I walked past a cemetery holding those early pioneer decedents on my way here. They have lain there since the mid-1800s, and I suspect some of the trees below BT’s alder heard the creak of their wagons and shouts of discovery, saw the influx of loggers, farmers and tradesmen; and watched as new neighborhoods grew up around them both.
The most accurate way to determine a tree’s age is to measure its growth rings. Simply start from the center and count to the outer edge. The outermost rings are the youngest. As the tree grows in the spring, it produces larger, faster-growing cells, which have a light color. During the summer, the cells are smaller and slower growing. The difference makes the familiar alternating light and dark circles. Together, a light and dark ring represent one year of growth.
Scientists can use the width of the rings to determine whether subsequent years were “bad” or “good” for the tree. If the width is less, the tree may have experienced drought or other hardships. Looking at other trees of the same species in the same area should show a pattern. This would pinpoint a year of atmospheric climate change, which future samples can be matched to. This science is called dendrochronology. Some species work better for this study and samples of their ring history can be traced back for several thousand years.
It is possible to tell the general age of a tree without cutting it down. You will need to know a little about the tree, primarily what species it is. The first way, is to measure the circumference of the tree 4.5 feet from the ground. Then, calculate the diameter by dividing the circumference by pi. Multiply this number by the species’ average growth factor, which you will have to find online. The factor varies between 2, for say a cottonwood, to 8, for slower-growing horsechestnuts. This should give you an approximate age, accurate to within a few years. A second way, is to count the number of branch whorls that some species produce annually. Again, start at about chest high and count upward.
I happened to find a fallen tree, which had been cut with a chainsaw to clear it from the trail. It was impossible to tell when it fell. The cut was not new. The branches had long ago broken off and only a 10-foot section of the moss-covered trunk remained. I tried counting the rings. The outer rings are easy enough, with obvious variations between the light and dark sections. The lighter, harder rings also were slightly raised. As you approach the center, however, the rings are so small it becomes difficult to tell where one ends and the next begins.
After a few recounts, I came to 59. However, I also measured the diameter of the tree, which was 56 inches. Based on the nearby trees, I assume this tree is either a Douglas fir or a hemlock. If I divide the diameter by pi, then multiply it with a growth factor of 5, the tree would actually be 90 years old. Since, I can’t be sure where on the tree the cut was made or what species it is, the growth factor number may not be accurate. As you can see, there is a large variance between the age estimates. The rings provide a more accurate count.
Counting the rings can tell us other information, too. The distance between the rings on one side of the tree is much greater. There are also larger rings around the 40-year mark. This could mean that those years were more conducive to the tree’s growth and it was growing in a particular direction for sunlight. The tree, at 45 years old, may have sustained an injury or disease, indicated by a large black mar.
In the scope of this forest, BT’s alder is relatively young. Further down the hillside, there are giants: hemlocks and older bigleaf maples. White oaks are coming back where the forest thins. Occasionally you find a Pacific madrone, vine maple, spruce or other colonist in the mix.
I pass, a set of twins. These two have held on together for a long time, joined at the trunk, splitting about 4 feet from the ground. Should I call this bigleaf one tree or two? The bark is a brownish-gray of lattice work grooves, unlike its paler, smoother teens at the top of the hill. The two trunks are immense, stretching up overhead to a verdant display of green five-fingered leaves waving in the warm breeze. A jay warns me to keep my distance. You never know a human’s intention.
“Twin” bigleaf maples
I have no intention of harming these giants. I find my tape measure. It is too short. Sixty inches barely reaches half way around one trunk. If my math holds, it would make these trees more than 175 years old. Perhaps, I think, someday, BT’s children will walk here, touch these deep wrinkles and admire the years that created them.
Tip: Morning light, evening light. Those are the two best times for photography, right? But, keep in mind that a lot of things don’t “wake up” until they warm up. Several flower species, including many water lilies, open later in the afternoon when there is more light. You’ll probably also notice, on your way back, that the butterflies just decided to get out of bed.