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Natural Time Machine: Tree Rings

Studying a double major in biology and geography, I have done more then my fair share of tree coring but as a woodworker, nothing makes or breaks a wood marvel as much as the grain of the wood used.

What are tree rings?

They are produced by the plant’s cells over a one year period and usually leave a distinctively wider lighter white band followed by a narrower darker one to indicate different growing conditions over an annual basis. Many people think tree rings only show the age of the plant but in fact, they are a treasure trove of information. Tree rings show a biologist a number of things such as:


Every few years, there are some tree ring bands that are exceptionally wide, demonstrating very good growing seasons full of nutrients, sun and rain allowing the tree to grow much faster then otherwise. Other times, the bands can be very narrow, indicating drought or other environmental conditions that where tough on the tree.

Local Species

Although rare, sometimes seeds and even rock fragments get stuck in the tree which can later be extracted to learn more about other local plant species


I noticed this especially while coring a stand of small trees at the top of the Rocky Mountains. These cedars where roughly 4 feet tall but where 20 years old, heavy snow cover, dry summer on a rock ledge and tough environmental conditions stunted their growth. Just about every tree in the stand that I researched had more growth on one side of the tree more then the other, the reason? Avalanches of snow and rock would hit the tree several times a year on only one side, causing damage, further stunting localized growth and the other side also had more sun exposure due to the rock cliff. The result was tree rings that looked more of an oval shape then round with deep grooves (damage).


Although dendrochronology is a big word, all it means is that once you have a good representation of the tree stand you are studying, you can use the information you have gathered about the past to make predictions about that localized environment in the future. For instance, if you notice for the past 200 years that there has been a major drought roughly every 35 years, then you can predict that this will also hold true for the next few hundred years. Uncertainty increases the further you project but this is useful to help manage a sustainable forest ecosystem.

The infernal borer

Now that we know what tree rings are and just a glimpse of what they can show, we now need to deal with the tool of the trade, the borer. This is an infernal contraption that acts like an auger but with a hollow tip. You have to screw this into a tree as horizontal as possible regardless of the terrain then, using an internal rod, extract the core that you have just made once you “think” you got to the heart of the tree. Why is this an infernal contraption? Well, after a few hours, your hands will become raw and as the screwing action isn’t very natural to humans, sore all over. To add insult to injury, this cannot be done by a machine as a slow, deliberate twisting action must be taken in order to not damage the core you are extracting. A borer is also very fragile, too much pressure or hitting an embedded rock and this tool, worth up to 500$ is junk!

Why should YOU care about tree rings?

An important piece of climatological data comes from studying past ecosystems and a vital piece of that puzzle is tree ring data. I have bored into waterlogged bogs, trees, rocks and even shoveled my way to bedrock for some research, it’s grueling work when you can be assured that all the local black flies and mosquito come join in the party. The study of tree rings by researchers around the world helped lend credence to the fact that global warming is a true phenomenon and also plays a vitally important roll in managing forest resources.

The Bottom Line

Tree rings are like wedding rings, they require lots of sacrifice to acquire.

Research Institute of Caspian Ecosystems