ADAM HART-DAVIS / SCIENCE PHOTO LIBRARY ADAM HART-DAVIS / SCIENCE PHOTO LIBRARY
Tree growth rings. Cross-section of a tree trunk showing the circular bands of growth rings. Each of the growth rings represents a year of growth for the tree. Counting these rings reveals the tree's age at felling. The rings can also give information on environmental conditions at the time of growth. Thick rings, for instance, indicate excellent growth conditions for the tree.
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