When the city arborist cut down the ailing sugar maple tree in our hell strip, they left us a cookie as a souvenir. It’s been leaning against the wall next to me for two years. I always thought we might turn it into a small coffee table or tray.
The wood cookie I saw in Tucson could probably provide flooring for a tiny home. It was ten feet across and came from a tree that was around 1700 years old. It blew down in a storm in Sequoia National Park in 1915 and today it’s on display in the lobby of the University of Arizona’s Laboratory of Tree Ring Research.
A series of historic annotations are projected on the giant sequoia’s rings. When the tree was a dozen years old, Buddhism entered China. Five hundred years into this tree’s life, gunpowder was invented. Over a thousand years into this tree’s life, Isaac Newton first described gravity.
While humans have long understood that rings on a stump correspond to the age of the tree, the founder of Tucson’s Laboratory of Tree Ring Research, Andrew E. Douglass, realized that there was a lot more information in those rings. Douglass started out as an astronomer and was especially interested in sunspots and solar variability but he hit a wall in his research when he ran out of historical weather data. Somehow he thought to take a closer look at tree rings and Douglass realized that the thickness of a ring corresponded to precipitation and other environmental factors.
As he became more adept at reading tree rings, Douglass discovered that the weather data he was pulling from these trees could be used to date logs used in ancient construction. By comparing trees in a region, he could identify similar weather patterns and place trees (and the associated ancient ruins) in a timeline.
The study of tree rings is called dendrochronology and as the Laboratory of Tree Ring Research’s website explains there are three objectives:
to put the present in proper historical context
to better understand current environmental processes and conditions
to improve understanding of possible future environmental issues
Upon returning to Pittsburgh, I took another look at the comparatively humble cookie from our sugar maple. Based on historical photographs of the house, I can see that the tree was already growing in the hell strip in the 1950s and potentially even in the 1930s. I wonder about the things that this sugar maple has witnessed.
On close inspection, the tree rings look so different from one another. Some are barely visible at all. Was that a drought year? I wonder if a trained dendrochronologist could see Pittsburgh’s declining pollution in these rings. Or the years that the Pirates won the World Series? Is this tree’s cause of death written in this slab of wood?
Do you have an old tree growing in your yard? Or have you ever counted a tree’s rings? I’d love to hear about it.
And one more thing: We’re experiencing some oddly warm weather in Pittsburgh this winter and last week I noticed some snow drops emerging in our backyard.
I’ll start watching for crocuses next. Stay tuned.
Fascinating!
This is so cool.
We had an old tree taken down last year, and I was sad about it and really hoping to acquire a cookie from it and be able to count its rings. But it turned out that it was almost completely hollow inside because of ants. That was disappointing although it did make me feel better about our taking it down.