We know that in looking at a tree slice, we can count the rings to tell the age, but did you know that we can learn a LOT more than just age from the rings?

What are Tree Rings?

When you cut a slice of tree, you are left with what’s called a Tree Cookie. This slice can tell us a lot about the tree’s life history! Each ring not only tells the age of a tree in total, but also tells us things like the climate each year, if there were any bugs or fires, and the direction the tree grew.

First, you can count the total number of rings in the cookie. Each year, the tree will add a new ring, so one ring corresponds to one year of age. Second, The wider the space is between each ring, the better the climate of the growing season. If there was good water, sunlight, and nutrients that year, the more girth the tree can put on. If the climate was poor that year, then the tree allocates resources elsewhere and doesn’t put on as much girth. 

Tree Cookie Damage

Then, you can examine the tree cookie for fire damage. This might look like a small section of blackened wood cells. Because the inner cells are dead, they cannot repair the damage caused by the fire, so evidence of the damage will remain even decades later. Many trees are adapted to withstand fires, and in fact, some trees require fires to allow their seeds to germinate! These trees have thick, dark colored bark and often are rather resinous. The resin keeps seeds “locked” or gummed up, then melts when exposed to the heat of the fire. When the resin melts away, the seed can then germinate.

Next, examine the slice for insect damage. Holes, tunnels, and pock marks can be evidence of boring insect presence. The presence of insects usually indicates that the tree was stressed out to begin with, and the insects were attracted to the weaker wood.

Looking to see if the tree was leaning can be a good indication of if the tree was getting the sunlight it needed. If it wasn’t getting the light or nutrients it needed, then the tree can become stressed. A tree will lean to reach for the light and you will be able to see this lean in the cookie slice. When a tree leans, the rings will be all bunched together on one side. The rings will look asymmetrical. While a tree will usually lean in order to reach for light, there can be external pressures applied to cause the lean. For example, a neighboring tree may fall on the primary tree and sit on it for a long time, which can cause the living tree to lean. The pressure and weight of ice can also cause a tree to lean. 

Practice Your Tree Ring Interpretation

Take a look at the tree cookies and rings below! What can you learn about the tree’s life from examining the rings?

Extra Tree Cookie Goodness

Article about Climate Change Future Predictions using Past Tree Cookies