About Tree Rings

Tree rings tell much about a tree.

Tree rings tell the life story of the tree. For each year the tree ages and grows, another ring adds itself to the inside of the trunk. Tree rings not only tell the age of the tree but also what the climate was like in its life, if it acquired any injury and if it encountered any drought conditions. Dendrochronology is the study of tree rings.

Tree Stems

Trees consist of five layers. The outer bark, phloem and cambium make up the first three layers. Xylem and heartwood are the remaining two layers. Heartwood gives the tree its strength and support, while xylem passes water to the leaves. Cambium produces new wood and tree rings. Phloem passes food from the leaves to the tree and the outer bark acts as a skin.

Conifer Tree Ring

Conifer wood describes trees and shrubbery you would most likely find in a backyard. Pine trees exist in the conifer wood category. The earlywood—or the wood grown in the spring—presents a light color. The cells remain large. Latewood, which grows in the summer seasons, grows slower. The cells, therefore, remain small and the wood takes on a darker, richer hue.

Angiosperm Tree Ring

Angiosperm wood categorizes hard woods, like beech and oak trees. Earlywood has cells with vessels large in diameter. Wood grown in the summer—the so-called latewood—has cells with small diameter vessels. Even though these types of trees differ significantly from conifer trees, the tree rings will look identical, alternating light and dark cells.

False Rings

False rings are a result of an extreme and sudden change in the weather or climate triggered within a single season. You can tell the difference between a true ring and a false ring by noting the difference in their cellular structures. Although a false ring provides valid and interesting data about the climate, it does not reflect the age of the tree.

Mini-Rings

Occasionally, you will come across a tree with a condensed growth ring or no ring at all. The lack of a growth ring is an indication of meristematic tissue, a disruption of physiological function or absolute starvation of the tree. Cambium growth is the growing part of the trunk. If a tree's cambium suffers damage, mini-rings form. They may also form in rapidly declining trees.

References

• Henri D. Grissino-Mayer's Ultimate Tree-Ring Web Pages
• Columbia University: Tree ring lab
• Arbor Day Foundation: The Life of a Tree
• University of Arizona: Tree ring basics
• Tree Ring Society: Tree-Ring Related Links on the Web

Resources

• EcoKids
• Eastern Native Tree Society: False rings and missing ring
• Warnell School of Forest Resources: Tree growth rings