Tree rings are perhaps most commonly understood as the indicators of the tree’s age. Each ring, for the most part, represents a year’s growth. But there’s a lot more to tree rings than just telling us the age of a tree.
Tree rings and climate
Tree rings can also give us detailed information about past climate conditions and how they compare to the current climate. Scientists are able to see climate change in the colors of the rings. The annual growth rings can vary a great deal in color, from light to darker and also in width, all representative of the climate conditions for the period of time that the ring was set in place.
If the growing conditions are more favourable, the rings tend to be wider than those set down in place under more adverse conditions. Ring color can be associated with the levels of nutrients available and/or stresses that the tree endured during a specific period. The rings are considered to be accurate to the point that predictions on future climate conditions can be made based on historic climate fluctuation patterns.
Armed with this biological time reference many artefacts have been dated using the information that tree rings have provided. In the 1970’s the field of archaeology and environmental science realized that tree rings provide an 8,600 – 12,500 years of past climate events.
What trees have the most reliable rings?
Oak is considered to be the most reliable species to calculate chronology from tree rings, as there has not ever been a case that the Oak has skipped putting down a ring. Birch, Alder and Willow on the other hand are not used as they present tremendously erratic growth patterns, often missing or doubling up on ring development.
Radiocarbon dating is directly linked to tree ring development. The highly reliable ring development is compared to the amount of carbon present in the article that is to be dated. The equipment is actually calibrated against tree ring development which then provides an accurate date with a small margin of error (+- 30 years).
Scientists lean towards dendrochronology with a particular emphasis on what our climate could be like after a devastating shift in temperature. Climate conditions in North America were unusually odd for several hundreds of years affecting the growth habits of trees and other plant forms. The record stands clear from the paleo-wood that has been found in eastern North America that these disruptions in climate happened at a specific time and with this, models can be generated to predict future climate situations.
Tree rings can help protect us
Forecasts for areas that are frequent to flooding have been developed using the growth patterns of trees within the flood prone regions. During periods of high water, the growth rings are naturally affected and using the metrics that Mother Nature has provided, patterns regarding flooding can be measured. This information is vital to flood prone regions so as to allow the local governments and landowners to take the appropriate and necessary measures. Studying the rings of dead but not decayed trees as well as the mummified remains found high in the Canadian Arctic are used to decode earth’s past climates.
This information is of vital importance from an archaeological reference as well as climatologic. The information rendered enables scientists to model accurate predictions of what can occur as well as enhance our understanding of the changes our world has undergone. I have had the personal privilege of seeing the mummified remains of ancient trees within 200Km of the North Pole.
This collection of trees and shrubs still had visible rings which allowed them to be dated and identified. Remarkably, the genus of this find varied from Oak, Maple, Beech and a host of Carolinian genus, unusual you say? Indeed, they grew in what is now a frozen habitat devoid of all trees.
Like the Enz in J.R. Tolkien’s popular literature ‘Lord of the Rings’, trees provide a wealth of knowledge as well as being stalwart protectors of the environment. There is much yet to learn from our trees about our collective pasts and what may lie ahead of us in the future.