Reading between the Rings
A cross section of a tree shows much more than its age! Diameter growth is particularly sensitive to fluctuations in the environment: moisture in the soil and air, temperature, and sunlight. Very broad rings generally indicate a good growing year. The tree apparently received everything it needed.
The growth rate of a tree can be compared to the growth of a child. A young sapling grows much faster than an adult tree. A cross section of an older tree shows rings that are quite broad at the beginning of its life (in the centre) but that become progressively smaller. An old tree produces very narrow rings and its diameter and height growth are considerably slower.
Click on a picture in the window at the left for an explanation of what may have caused the cross section.
Narrow rings do not only signify a lack of sun or water. A forest fire may have damaged the tree's crown and slowed its growth. Defoliation by insects or fungi can have the same effect.
After several years, the tree gained strength and returned to normal growth.
This tree had a rough time during its first ten years! Maybe someone helped it by cutting the large trees around it to give it more light.
Trees don't all have their heart in the right place! This tree shows off-centre growth. If the tree was in a location exposed to high winds, its wood would grow faster (wider rings) on the side away from the wind than on the side facing the wind.
This cross section may also come from a tree that was leaning. The tree formed reaction wood (compression wood) that enabled it to straighten up. The wider rings are on the underside of the leaning trunk because growth was faster there.
Do you see waves? Look at the outer bark. Wasn't there a branch here?
Here are two games to test your knowledge:
