The Oak’s Trunk

The wood that makes up an oak trunk contains sapwood and heartwood. Sapwood carries water and minerals from roots to the leaves. Heartwood stores waste produced by the tree. Wrapped around the wood is inner bark, which carries food from the leaves to the rest of the tree, and dead outer bark, which protects the trunk from fire and other damage. Between the inner bark and the sapwood is a thin level of cells called the vascular cambium.

Each year, the vascular cambium produces a layer of sapwood and a layer of inner bark. In many oaks, the first sapwood produced in the spring has very wide vessels, or water-carrying tubes. These vessels carry large amounts of water from the heavy spring rains. Vessels produced in summer and fall are much narrower. This difference in the thickness of vessels creates annual, or yearly, growth rings, which we can count to learn a tree’s age.

This drawing shows the inside of an oak’s trunk.View Larger Image

Fiammetta Dogi and Studio Stalio