Trees are the most common life forms spread far across the planet, from the coldest Arctic to the hottest savannas. They are the planet’s respiratory system, taking in atmospheric carbon dioxide and expanding the oxygen on which our survival depends. Trees can survive for decades and longer, if not centuries. A tree’s longevity can expose it to a wide range of environmental variations, including rainy season, parched years, frozen decades, steamy months, forest fires, and more.

Green Leaf Plant on Brown Wooden Stump
Green Leaf Plant on Brown Wooden Stump | Image Credit – Joey Kyber

Suppose experts can establish the timeline and periods of tree growth rings. In that case, scientists can apply the science of Dendrochronology to guesstimate when a tree was knocked down or perished of natural causes. Dendrochronology is the deconstruction of the growth of tree rings, and it can enlighten us with a lot more than just their age. 

Experts can construct a timeline of organic archaeological contents and generate a chronological history against each artifact. We can take a lesson about past climates. These patterns on tree trunks inform bizarre season-long weather patterns or durations of climate change that impact tree growth and suggestions on how they may influence our environment in the coming years.

In the 1900s, A E Douglass, a United States astronomer with a deep passion for climate research, devised the method of Dendrochronology. He hypothesized that tree rings might be used as proxy data to go back through history, further than humankind has ever imagined. 

It was later proven that he was correct, and the more trees they studied, the experts could approximate a larger volume of the records and develop a more realistic view of our historic climate system. It wasn’t until the 1970s that archaeologists acknowledged the value of using tree ring data within their profession.

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How exactly can we calculate a tree’s age?

How exactly can we calculate a tree's age
How exactly can we calculate a tree’s age | Image Credit – Faye Cornish

You must have observed that the crown of a tree trunk has a circular pattern of overlapping circles. Such tree rings can reveal how ancient it is and the climate for every year of its lifespan

Tree rings are generated throughout the annual growing season, the precise time determined by the tree’s geographical position and the habitat in which it grows. As the vegetative season draws to a close, the tree’s pace of development diminishes. Compared to prior progress, the cells generated are smaller and have thicker walls.

A coring instrument is often used to gather samples of tree rings without hurting the specimen. The coring instrument is a long tubular structure drilled into the tree’s trunk at right angles until it touches its core. The instrument and a long, narrow rod of tree tissue are then extracted from the trunk. The growth rings formed throughout the tree’s life will be visible in the tissue sample.

Experts can apply this insight in several scenarios. Dendrochronology is frequently used by researchers investigating contemporary ecosystems to scrutinize the impact of current meteorological conditions on vegetation development. On the other hand, Dendrochronology can determine historical weather trends in older trees, both petrified and still alive. Below are some of the most widespread applications of tree rings!

Age of the tree

Trees generate bands as they mature, consisting of a circle of light wood formed in the spring (earlywood) and a ring of dark wood developed later in the summer (latewood). This means that we may use one band of light and dark wood to quantify the amount of timber created in a year. Considering the number of bands from the outer bark to the tree’s center would show us how ancient or young a tree is and can be used to date past events throughout the tree’s lifecycle.

Incidence of fire

When a piece of the trunk’s spreading section, referred to as the cambium, is injured by fire, the tree strives to repair the injury with new growth, resulting in fire scars. Certain fire scars heal entirely, while others stay unresolved due to numerous fires or severe decomposition of the charred wood. Hence, this gives the researchers an idea of the extent of a forest fire.

Quality of wood fiber

Quality of wood fiber
Quality of wood fiber | Image Credit – Aleksandar Radovanovic

Thickness, noise absorbency, hardness, and elasticity are significant features of wood that affect its viability for various products or end applications, ranging from violins to structural wood merchandise and fibers used in textile industries. Microscopic studies of tree rings, particularly when the specimen is magnified 57 times its original size, can reveal abnormalities in tissues and layers produced by water tension, storm, or ice deformation. These flaws can make timber stiff, brittle, or resistive to surface preparation, limiting its usefulness for specific applications.

Timber management units can make better economic choices regarding what commodities can be manufactured from the trees grown in a particular area and what species are most suited to sow for subsequent years. This, however, can only be possible if they can detect the wood fiber properties of trees before they are harvested.

Glimpsing the Human History

Archeologists have utilized the ring formations in architectural materials to determine the development of many of the world’s most iconic structures. For instance, the 1,000-year-old cliff dwellings at Mesa Verde National Park and 1,500 years old Bethlehem’s Church of the Nativity.

Insect Outbreak

Defoliation, which implies the shredding of a tree’s foliage or spines by pests like the forest tent caterpillar, is exhausting to the tree and causes a significant reduction in the rate of development, as evidenced by the dull annual growth ring on one such irregular aspen core

The “white ring” is likewise denser than the timber generated by the tree before defoliation and after healing. Investigators can comprehend more about the marks of tent caterpillar occurrences on aspen forest profitability, how predatory insects evolve, and how organisms adapt to such disturbances. And it is only possible by analyzing the emergence of white rings in trees.

Climatic conditions

Climatic conditions affect tree rings
Climatic conditions affect tree rings | Image Credit – Flickr

Trees that receive proper sunshine, moisture, and warmth evolve better and have broader growth rings than stressed trees. Dehydration, sickness, extremely hot or cold conditions, and shadowing or congestion by other trees can inhibit tree development and result in thin rings. 

Researchers can learn more about how the world is changing and altering forest ecosystems by studying rings from various trees across the terrain. Tree growth statistics are compared to local weather databases by climate experts. The ring thicknesses can determine previous temperature or moisture across the tree’s lifespan in regions with a strong statistical connection between tree growth and climate or rainfall during the overlapping timeframe. 

Trees can offer a climate chronology for hundreds of years in various places around the globe, with some going back 1,000 years or more. The derived climatic reconstructions improve our understanding of natural weather patterns while also providing a benchmark against the human-caused climate change that we can measure.

Tree Ring Labs are for real!

Tree Ring Labs are for real
Tree Ring Labs are for real | Image Credit – Simon Berger

AE Douglass, who resorted to trees to best investigate the interactions between sunlight and climate, established a magnificent lab to study and research tree rings at the University of Arizona. The facility has aided in establishing other research labs across the planet, resulting in an exponential growth in the number of trees investigated. 

There are now about a dozen big labs worldwide, collecting statistics from 4,000 locations on every continent except Antarctica. The statistical information is kept in the International Tree Ring Data Bank, an open-access repository for all academics. A far clearer perspective of the interplay of previous climate, ecology, and human culture emerges as more tree information becomes accessible.

Here are the three primary disciplines of tree ring research that sound a bit confusing, dendroclimatology is the examination of tree rings for previous temperature data; dendroarchaeology is the study of tree rings to comprehend how past climate influenced human cultures, and dendroecology recreates past forest ecosystems. On a fast-warming planet, this glimpse into the ancient climate history is critical for demonstrating how the climate of the previous half-century deviates significantly from historical averages dating back thousands of years.

What about accuracy?

Tree rings may be a minefield of facts. Nevertheless, numbering backward from the outermost layer isn’t always sufficient to certify the facts. Annual tree growth rings are no exception to the rule that ecology is seldom as precise as we would want it to be. 

Although trees typically produce one ring every year, they may miss one or have uneven gains that appear to be an extra full ring, commonly referred to as a false ring during the vegetative stage. Furthermore, tracing backward is impossible with dead trees since the year correlating to the outer rings, which is the year the tree perished, is unclear.

Dendrochronologists employ cross-dating to solve the problem of abnormal rings and predate the growth rings of deadwood, which enables them to explore even further backward in history. Crossdating is a cross-referencing process that uses tree rings as a reference point. To grasp cross-referencing, consider tree rings as a QR code: and each one has a sequence of thin and thick bands that indicate climate change on a broad scale.

To Conclude

Tree rings can assist us to lessen the ambiguity
Tree rings can assist us to lessen the ambiguity | Image Credit – Johann Siemens

Tree rings can assist us to lessen the ambiguity in how much we can claim about how toasty it is now compared to when the dinosaurs roamed the planet (well, maybe not so far unless a tree chunk is stored in ambers!). And, now that we understand that there’s a lot more information contained in the annual tree ring, I am sure that none of us can keep ourselves from counting a tree’s age if we ever find a treepie!

(Last Updated on May 4, 2022 by Sadrish Dabadi)

Shradha Bhatta holds a Bachelors’s Degree in Social Work along with a Post-graduate degree in Project Management from Georgian College in Canada. Shradha enjoys writing on a variety of topics and takes pleasure in discovering new ideas. She likes traveling and spending time with nature. She is a very people-person who loves talking about climate change and alerting people to go green!