Counting tree rings is a simple project suitable for third-grade students or older. The student counts the rings on several cross-sections of tree trunks, starting from the pith to the bark; he then compares the number he gets when counting the rings on the cross-section of a young tree trunk with the number of rings on an older tree. The young tree has fewer tree rings, which can point to the conclusion that the rings indicate the age of the tree. The student can determine the approximate age of each tree.
The student observes and measures the size of tree rings on trees from different climates and areas with various light-exposure conditions. If tree trunk cross-sections are not available, the student may use life-size pictures. Typically, rings may have a width between 0.02 and 1 inch; width is influenced by factors such as climate, the soil fertility and humidity, temperatures and exposure to light. The student may also notice that the first few rings are wider, while they become narrower with aging, as the tree produces the same number of cells, but the circumference of the tree increases.
In this experiment, the student compares three or a number of tree-trunk cross-sections belonging to different species to establish if a difference exists between the size and color of the rings. The size of the rings differs from species to species; some may be closely spaced or widely separated. Color variations exist as well. The student can take pictures or draw examples based on his findings when studying the tree rings on different tree species.
The student studies the anatomy of a tree trunk to identify the tree rings. On some trees, the student may observe both scars and rings. Fires in the forest or insect infections may have an impact on the tree to cause scars, which are visible alongside the rings. The student counts the rings and establishes the approximate year when the tree was affected by a fire or an insect infestation. If several fires are recorded, the student calculates the time between the fires.