What do annual rings in a tree trunk represent?

Annual rings in a tree trunk represent one year's growth. Each ring is formed by the growth increments of the tree, displaying how much the tree has grown during a specific year. This growth is influenced by various environmental factors such as water availability, temperature, and soil nutrients, leading to variations in ring thickness.

The rings can also provide valuable information about the tree's age, as the number of complete rings corresponds to the number of years the tree has lived. In temperate regions, where the seasons are distinct, each year typically produces two rings: a light-colored ring formed during the rapid growth in spring and a darker ring formed in the slower growth during late summer and fall.

Other choices do not accurately reflect the function of annual rings. The thickness of the bark does not relate to the age of the tree but rather its protective function, while the number of roots pertains to the root system rather than trunk growth. The type of tree can affect the ring structure but is not represented by the rings themselves. Therefore, understanding annual rings is fundamental in dendrochronology, the study of tree age and growth patterns.