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What Tree Rings Tell Us Besides Age

top view of rings on oak tree stump
Triff/Shutterstock

Counting rings can tell you how old a tree is—each ring usually represents a year in a tree’s life. But those rings can also tell you so much more if you look a little closer.

Tree and the Seasons

Places on the planet with distinct seasons may see more tree growth and broader rings when the seasons are favorable. Spring is the season when trees see the most rapid growth. An area with little to no spring weather will most likelysee smaller trees.

Environmental History Through Tree Rings

This logbook within tree trunks is used to learn about weather patterns by scientists. Yes, the rings of a tree tell you far more than just the possible age of a tree.

There’s even a name for the science behind reading the story within a tree trunk. Dendrochronology is the science of dating trees by their rings and discovering what climate conditions and other environmental factors have affected trees and the areas in which they grow. Through studying the trunks of trees, scientists can determine when there were significant weather events and more—it;’s tree chronology!

It’s common for a single tree to have varying ring sizes. Each ring tells a story about the environment the tree is growing in. Because the growth of a tree is directly affected by the weather, it makes sense that you’d be able to tell when a tree experienced a bad year.

Larger rings indicate that the tree had a prosperous year of growth. Meaning, the year had suitable temperatures and plenty of rain. A good year for a tree may mean a nice thick ring. Subsequent bad years will be visible via smaller rings. How small those rings are for each tree depends on how bad the weather was.

Too much cold weather will lead to smaller rings, as can flooding. Maybe there was a drought, a forest fire, or the tree suffered from an injury of some kind. If the tree survives the bad weather or fire, it will continue to grow, and can even have larger rings again in the future when the weather is conducive.

Bark Injuries and Tree Growth

Bark injuries can also affect the growth of a tree, inhibiting new layers that grow around the damaged area. Injuries can make it so that rings vary in size during the same year of growth. Injuries can happen due to weather or bugs, or depending on where the tree is growing. Trees growing through a fence or into the side of a building will have abnormal ring growth.

Bugs Can Affect Tree Rings, Too

European spruce bark beetle under bark of tree
HHelene/Shutterstock

Insects are another factor outside of general weather that can affect the growth of a tree and how the rings look. Insect infestations can make rings grow smaller. Even in a year with good weather, bugs can affect the growth of a tree significantly.

Depending on the insects that have invaded the trees, you may find holes bored into certain parts of the tree rings, showing at what ages bugs and beetles ravaged the tree. You’ll generally be able to find signs that bugs caused the issue.

How Tree Rings Are Helping Science

The National Weather Service has scientists who track weather. They’ve been doing this since the late 1800s. There are trees alive today that have stood for hundreds and even thousands of years, enabling scientists to look the rings and study weather patterns for thousands of years before our time.

Patterns found in tree trunks may also be able to tell scientists about potential weather patterns that may happen in the future. It’s not a perfect way to predict the weather, but it does help with understanding how the environment works.

Yvonne Glasgow Yvonne Glasgow
Yvonne Glasgow has been a professional writer for almost two decades. Yvonne has worked for nutritionists, start-ups, dating companies, SEO firms, newspapers, board game companies, and much more as a writer and editor. She's also a published poet and a short story writer. Read Full Bio »