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Spring is that time of year when the flowers bloom, the birds return, and the trees sprout new, green leaves once again. While they’re growing leaves, trees are also growing new branches and roots, and the roots and branches they already have grown larger over the spring and summer. Even the trunk grows. And as the branches and roots are reaching out further and further, the entire tree (root, trunk, and branches) is also growing bigger around, getting thicker. This seasonal thickening grows a ring around every part of the tree every year. You may have heard of tree rings before, how if you cut down a tree you can count them to see how old the tree is. Did you know, though, that the branches have rings, too? You can figure out the ages of each branch by counting their rings, and you can learn some other things as well.
Materials:
- A few tree branches
- A saw (No kids allowed!)
- An adult (For the saw.)
- A magnifying glass (optional)
Process:
- First you need to find a tree that’s lost a few branches. That shouldn’t be too hard, either in your backyard or at the park or on a nature walk. Grab a few of them of different thicknesses.
- Have your adult cleanly saw both ends of each branch so you can easily observe the rings inside.
- Count the rings and compare them. How many rings do thick branches have vs. thin ones? What about on a single branch? Does the skinny end have fewer than the wide end? Are there some branches with the same amount of rings but different thicknesses?
- Observe closely the rings themselves (use a magnifying glass here, if you have one). Are some thicker than others? Do you see anything odd, like a knot with its rings, or some damage to some of the rings? All of these details can help you to learn about the tree and its history.
Summary
The study of tree rings through time is called dendrochronology. The roots of the word come from Ancient Greek. “Dendron” means “tree branch,” “chronos” means “time,” and “-logia” means “the study of,” so we put them together and get dendrochronology: “The study of tree branch time.” Dendrochronologists don’t chop down trees to look at their rings, though; they like to preserve the trees, so they take small cylindrical samples called “cores” that show all of a tree’s rings without having to cut down the tree.
Dendrochronology can be used for a lot more than just figuring out how old a tree (or one of its branches) is. You can learn a lot about the history of the area the tree lives by looking at its rings. For example, in a good year with lots of water and a long growing season, a tree will produce a wide, healthy ring. In a drought year or a year that was abnormally cold, the tree will produce a much thinner ring. Maybe the tree survived a fire one year. Those marks will be in the rings. Dendrochronologists can look at the rings, find the burn scar, and figure out when the fire happened.
Because dendrochronology has been around for a long time, dendrochronologists have been able to match up similar rings on multiple trees for certain regions of the world and have a record of overlapping tree rings going back thousands of years. If an archaeologist in England unearths a wooden structure, he or she can take a sample of the wood and match its ring pattern to England’s oak chronology, its record of oak tree rings, to figure out how old the building is. As long as it’s less than about 7,000 years old, the oak chronology can help provide an answer.
The branches you found probably weren’t more than a few years old at most, but with just a little knowledge you can speculate about what their short life has been like.
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