People are fascinated by big trees – New Hampshire, like many states, has a citizen-science-ish program devoted to finding them – and we usually assume that the ares are wicked old as well as wicked big.
Not necessarily, as I learned from a study published in Tree Care Industry, a magazine put out by the U.S. Forest Services. (You can see a PDF of the article right here.) The conditions that makes trees grow fast are too variable for size to be used as a measure of age, as you’ll see in this chart:
In fact, the paper notes, age and size can be inversely related to growth:
In larger trees with full crowns, declining ring width may simply be an expression that stem growth is geometric rather than linear. Adding one inch of a diameter to a 1-foot DBH stem adds about 20 square inches of wood at breast height. Adding that same inch to a 2-foot DBH stem adds about 38 square inches of wood.
That’s the trouble with biology: It’s so darn complicated.