If you were to cut down any tree more than one-year-old and look at the cross-section, you would see alternating bands of light and dark wood. The two bands together are called “the annual ring”, and they make up the amount of wood formed by the tree during a single growing season or year.
Why are the bands lighter and darker?
This is because the wood grows in a different way during the different seasons. In spring and early summer, the cells of the wood are bigger and have thinner walls. This makes them look lighter.
In late summer, the cells are smaller, have thick walls, and are closely packed together. This makes a darker band.
So What Are The Usages of Those Rings?
The age of a tree can be told by counting the annual rings. When you look at the rings of a tree, you will notice that they vary in width and in many other details. These variations are caused by the weather conditions that prevailed during the given season. A difference in the light, the amount of rain, and the minerals in the soil will produce a difference in the rings of a tree (and outside of the tree and that is bark).
That is why scientists often use the rings to obtain a clue to the weather conditions that prevailed years ago in certain parts of the world.
Who a tree grows, the wood of the tree is not the only thing that increases in size from year to year. Additions are also made to the bark of the tree. This is done by means of a thin band of living, dividing cells be- tween the wood and the bark.
This layer is called “the cambiurn”.
The new cells which are formed on the wood side of the cambium become wood. The cells formed towards the outside become bark.