Final answer:
Each ring of growth in tree rings represents one year of growth, comprising both earlywood and latewood. Dendrochronology uses these rings to determine a tree's age and past climate conditions.
Step-by-step explanation:
In tree rings, each ring of growth represents one year of growth. This is evident as each tree ring consists of a wider light-colored portion known as earlywood, which forms during the winter and early spring when trees grow at their fastest rate. Conversely, a narrow dark-colored portion called latewood forms in late summer as the growth rate slows down in anticipation of the dormant season. Thus, a combination of earlywood and latewood constitutes a single annual ring. Through dendrochronology, the scientific study of tree rings, researchers are able to assess the age of a tree and infer past climatic conditions based on the thickness and characteristics of these rings.