What is your age? To answer this question, one has to know the date of birth. With the date of birth as a reference point, one can calculate age counting the years passed by them. It is not this easy to calculate the age of trees, since trees may be a lot older than many generations of people.Age of Trees

How Can We Calculate the Age Of Trees?

Trees can be thousands of years older. The oldest tree in the world is estimated to be nearly five thousand years old. So, calculating the age of trees was a challenge for scientists.

The investigation by botanists led to the discovery of rings of trees. Later Leonardo Da Vinci mentioned in his book that trees form rings annually and the thickness depends on the environmental conditions in which it grows. This gave birth to the insight of evaluating the age of trees in botanists. In the present day, this very technique has been well renown as an authentic method for determining the age of trees.

Dendrochronology

Dendrochronology is the science of determining the age of a tree by counting the tree rings which forms each year as trees grow. The basic assumption is, the physical and biological changes at an instant are directly related to the environmental condition at that instant. So, cyclic change of season gives rise to a ring.

Apart from estimating the age of trees, this technique can help scientists to predict climatic conditions of past evaluating the rings of a tree. The limiting factors like precipitation and water holding capacity of landforms play a major role in determining the size of rings.

This technique is reliable because it involves cross dating i.e. dating several similar trees and mapping the pattern to improve the precision of age. Also, its reliability can be assured by observing the fact that it can be used to calibrate carbon dating.

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How Are Tree Rings Formed?

Growth is part of nature. Each spring new conducting cells are formed on the outer part of the trunk. These cells are large and have thin walls (earlywood) while the previous summer cells are smaller, denser, darker and have thick walls (latewood). This formation of cells ceases in winter. Again new cells are formed and the cycle goes on.

The cells formed in different seasons have different texture so that the layer is completely distinct from one another. The thickness of each layer depends on the climatic conditions corresponding to the year of formation. These layers make up the tree rings and their study helps to predict the climate during its formation.

How Are Tree Rings Counted Scientifically?

Of course, the rings of trees are difficult to count if they are thousands of years older. These rings are counted carefully by using a microscope by professional dendrochronologist.

The tree rings may be somewhat doubtful to determine the age of trees because some trees may have more than one ring in a year. So, the ring count is matched with other tree rings. This could authenticate the result and improve reliability.

Calibrating Radiocarbon Dating Using Rings of Trees

Radiocarbon dating is a dating procedure on the basis of radiocarbon with half-life 5,730 years. This process relies on the assumption that the concentration of radiocarbon in the environment is constant. But, nuclear activities have significantly changed the concentration of radiocarbon over years. This resulted in radiocarbon dating to go off as high as 100 years.

In recent years, radiocarbon dating curve has been calibrated using dendrochronology. This has made radiocarbon dating more precise than before. This technology can also be used to date a tree or any other material acquired from living beings.

Hence, tree rings can play a vital role in estimating the age of trees. Other techniques involving isotopes can be used to calculate the age of trees that do not bear rings.

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Author

Ashwin Khadka is a Physics graduate from Tribhuvan University, Kathmandu, Nepal. He is a science enthusiast, researcher and writer. Apart from writing he is also a researcher, with specialization on thin films for electrodes in solar cells.

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