Aging is generally associated with slowing down. But scientists have found that trees actually grow faster as they get older, making them star players in a forest’s carbon storage. In fact, one old tree can fix as much carbon in a year as the total amount of carbon in a “middle-aged” tree.
Researchers measured 673,046 trees from 403 species around the world, from tropical to temperate forests. Trees with a trunk diameter of 100 centimeters grew by an average of 103 kilograms per year, about three times as fast as trees of the same species with a 50-centimeter trunk. Some of the biggest trees grew by more than 600 kilograms annually. Large old trees make up only six percent of the old-growth forests in the western U.S., but they account for about one-third of the forests’ growth every year.
Old trees grow faster because they have more leaves, the team says. For example, if a tree’s diameter increases tenfold, its leaf area jumps by a factor of 50 to 100 times.
—Roberta Kwok
Stephenson, N.L. et al. 2014. Nature doi:10.1038/nature12914.
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