Final answer:
From the observation of four thick rings and four narrow, denser rings, we can conclude that the tree is eight years old as each pair of an earlywood ring and a latewood ring represents one year of growth.
Step-by-step explanation:
While examining the stump of a recently cut tree, you count four thick rings alternating with four rings that are much narrower and appear denser. From this observation, you should conclude that the tree is eight years old. Each tree ring represents one year of growth, consisting of both an earlywood and a latewood ring. The earlywood is formed during the period of rapid growth in the spring, while the latewood forms in the late summer when the tree's growth slows down.
Counting annual rings is a technique known as dendrochronology, which is used to determine the age of a tree as well as past climatic conditions. Since one full year's growth includes both a light, earlywood ring and a dark, latewood ring together, this tree, showing alternating patterns of four thicker and four denser narrow rings, documents eight years of growth and life.
The tissue scientists examine when using dendrochronology is the secondary xylem. This part of the tree adds a new layer of xylem each year, which forms the visible rings that we can count to determine the tree's age. These rings can also indicate the climatic conditions during each growing season, providing valuable historical climate data.