Why do trees have rings?

Trees form rings as they grow due to the seasonal variations in the production of xylem, the tissue responsible for transporting water. During the growing season, trees produce lighter, less dense wood, while darker, denser wood forms in late summer or autumn. The alternation of these layers creates visible rings. Scientists use tree rings to determine a tree’s age and study past environmental conditions like droughts, fires, and climate changes, a field known as dendrochronology.