Science Diaries: Tree Rings Got rings?

Science Diaries: Tree Rings Got rings?

Ambience: Dawn chorus

JM: We’ve all heard that you can tell the age of a tree by counting the number of tree rings it has. Well, it turns out that not all trees have easily recognizable tree rings. Welcome to Pulse of the Planet’s Science Diaries, a glimpse of the world of science from the inside.

EC: The science of dendrochronology, of course, is based on the principle that trees put on discrete identifiable annual rings each year. That isn’t the case everywhere in the world. There are trees growing in the tropics that have put on no discernable annual ring. They simply grow, and there’s nothing to tell the trees to stop growing, because it’s always warm, there’s always a lot of sunshine, there’s always perhaps a lot of moisture. And therefore the trees have nothing to tell them to stop growing each year, and therefore to produce an annual ring.

JM: Edward Cook is director of the Tree Ring Laboratory at Lamont Doherty Earth Observatory in Palisades, New York, where trees do grow a new ring each year.

EC: Because the seasons are so well defined in temperate latitudes, the trees, in effect, know when to stop growing. And that defines the boundary of an annual ring, because they’ll stop growing, and then in the next spring, they’ll start growing again. And there’s a clear separation in the growth boundaries between the previous annual ring and the one that’s formed the next year. So the very first thing that we need to have are trees that put on well defined, very clearly defined annual rings. If they don’t do that, then we can’t work with them. Beyond that, almost any tree that puts on annual rings can be of some value for us.

JM: Edward Cook’s laboratory uses tree rings to study a variety of natural phenomena, including shifts in climate. We’ll hear more in future programs. Please check out our website at pulseplanet.com. Pulse of the Planet’s Science Diaries are made possible by the National Science Foundation. I’m Jim Metzner.

Science Diaries: Tree Rings Got rings?

In regions without clearly defined seasons, a tree's rings are not easily identifiable.
Air Date:05/29/2012
Scientist:
Transcript:

Science Diaries: Tree Rings Got rings?

Ambience: Dawn chorus

JM: We've all heard that you can tell the age of a tree by counting the number of tree rings it has. Well, it turns out that not all trees have easily recognizable tree rings. Welcome to Pulse of the Planet's Science Diaries, a glimpse of the world of science from the inside.

EC: The science of dendrochronology, of course, is based on the principle that trees put on discrete identifiable annual rings each year. That isn't the case everywhere in the world. There are trees growing in the tropics that have put on no discernable annual ring. They simply grow, and there's nothing to tell the trees to stop growing, because it's always warm, there's always a lot of sunshine, there's always perhaps a lot of moisture. And therefore the trees have nothing to tell them to stop growing each year, and therefore to produce an annual ring.

JM: Edward Cook is director of the Tree Ring Laboratory at Lamont Doherty Earth Observatory in Palisades, New York, where trees do grow a new ring each year.

EC: Because the seasons are so well defined in temperate latitudes, the trees, in effect, know when to stop growing. And that defines the boundary of an annual ring, because they'll stop growing, and then in the next spring, they'll start growing again. And there's a clear separation in the growth boundaries between the previous annual ring and the one that's formed the next year. So the very first thing that we need to have are trees that put on well defined, very clearly defined annual rings. If they don't do that, then we can't work with them. Beyond that, almost any tree that puts on annual rings can be of some value for us.

JM: Edward Cook's laboratory uses tree rings to study a variety of natural phenomena, including shifts in climate. We'll hear more in future programs. Please check out our website at pulseplanet.com. Pulse of the Planet's Science Diaries are made possible by the National Science Foundation. I'm Jim Metzner.