by Kristen Minogue
Mysterious things happen to forests as they grow old. The passing of time alters the trees, the animals, the microbes, even how much they breathe.
Just like people, forests age. Dense rows of birch and cherry trees give way to tulip poplars. Eventually the tulip poplars vanish and more spacious oaks and hemlocks rise up in their place. But arguably the most important changes occur underground. The planet’s soils store more than three times as much carbon as the atmosphere. And—while researchers still aren’t sure exactly why—older forests seem to be better at holding onto it.