What does the graph of volume versus age typically illustrate?

• A. The change in bark thickness over time.
• B. The effect of soil nutrients on trunk diameter.
• C. The relationship between tree age and the volume of wood produced.
• D. The rate of leaf drop with age.

Answer: (C)

The graph of volume versus age shows how the amount of wood a tree produces accumulates as the tree gets older. As trees grow, diameter and height increase, so volume rises—often more quickly in early life and then more slowly as the tree matures. This relationship is what foresters use to estimate timber yield over time and to decide when to harvest (rotation age). Other ideas don’t fit the typical concept of a volume‑versus‑age curve: bark thickness changes with age but isn’t the standard measure plotted, soil nutrients affect growth but aren’t depicted as a direct volume‑over‑age curve, and leaf drop rate isn’t a primary measure of accumulated timber volume.