Have you ever tried to count the rings of a tree? Did you know that we can use the tree’s rings to find out its age? Dendrochronology, or tree-ring dating, is the method that helps us date wooden object by counting the tree rings present in that wooden object.
What is dendrochronology or tree-ring dating?
When looking at a cross-section of a tree, we can observe a lot of rings. These rings go all the way from the tree center to the very edge of the tree. The innermost rings are the oldest rings, while the rings on the edge, right next to the tree bark, are the newest ones.
Each of these rings represents one year in the tree's life. So by counting the rings, we can find out how old the tree is. And we don’t need to cut down the tree to count its rings. We can use an increment borer to collect a core sample from the tree and count the rings on that core sample.
The oldest tree in the world, at the time when it was cut, was about 4900 years old. But we can actually date wood further back—to about 12000 years by using databases of tree ring patterns. The tree-ring data banks contain information about hundreds of types of trees of various ages from all over the world. If we can find correlations between the young rings of one tree and the old rings of another tree, we can move back in time by thousands of years, just by cross-referencing samples with similar ring patterns.
You can see how this cross-referencing works in the above example. Here, the edge region of the first wood matches the center region of the second wood, then the edge of the second one matches the center of the third one, and the edge of the third one matches the center of the fourth, and so on. This is how we can go back in time thousands of years—by searching for similar patterns between the old part of one tree and the new part of another. And when we have an undated wooden object, we can date it using these tree ring databanks.
You’re probably wondering now why do we have differences in tree ring patterns? It’s because the environmental conditions have a strong influence on the tree growth, and we can see this by analyzing the shape of the tree rings. The narrow rings represent years of drought that hinder the growth of a tree, while the wider rings represent years of more favorable conditions for the tree growth. And there’s more! The tree ring fingerprint also shows the times the tree went through forest fires and the post-fire regeneration. And we can also see signs of insect attacks or the influence of strong winds on the tree growth. So, you see, the trees hold an abundance of information about their history.
Applications of dendrochronology
The applications of dendrochronology vary from climate studies to helping with the radiocarbon dating calibration to art and archaeology. In cultural heritage, we can use dendrochronology to date heritage objects that are made of wood. Case studies where dendrochronology was successfully applied on these types of cultural heritage objects include paintings on wood panels, musical instruments such as the famous Messiah violin of Antonio Stradivari, and shipwrecks such as that of the Mary Rose.