Old trees may not grow taller every year, but they do keep bulking up—like a human bodybuilder. That's the summary of recent research into the life of trees. An article on NPR recently summarized this recent research into the life of trees:

Once trees reach a certain height, they do stop getting taller. So many foresters figured that tree growth—and girth—also slowed with age. "What we found was the exact opposite," says Nate Stephenson, a forest ecologist. "Tree growth rate increases continuously as trees get bigger and bigger," Stephenson says.

Stephenson got together with 37 scientists from 16 nations to answer the question on a global scale. They examined nearly 700,000 trees that have been the subject of long-term studies. Here's their conclusion: While trees did stop getting taller, they continued to get wider—packing on more and more mass the older they got. And we're not talking about the tree-equivalent of an aging crowd with beer guts—old trees are more like active, healthy bodybuilders.

"It's as if, on your favorite sports team, you find out the star players are a bunch of 90-year-olds," Stephenson says. "They're the most active. They're the ones scoring the most points. That's an important thing to know."