Science Diaries: Tree Rings Cross dating

ambience: dawn chorus

JM: Tall, sensitive, and loaded with hundreds of rings? Sounds like the kind of tree that any dendrochronologist would just love to cross-date! Welcome to Pulse of the Planet’s Science Diaries, a glimpse of the world of science from the inside.

EC: When we extract a core of wood from a tree, one of the first things we do is to look very carefully at the core of wood and see first of all how many rings do we have in the tree. For studies of past climate, we want to have as many rings as possible so we can look at climate as far back into the past as possible. But the other thing we look for is evidence for changes in growth from year to year. In the jargon of dendrochronology that’s called sensitivity. And when we say a tree is sensitive, we’re saying that it responds to changes in its growth environment from year to year. Probably most commonly, these changes in growth from year to year are caused by changes in climate.

JM: Climate studies are central to the work of the Tree Ring Laboratory at Lamont Doherty Earth Observatory in Palisades, New York, where Edward Cook is director.

EC: If there was a drought in 1965, as there was here in the New York metropolitan area, and we see a narrow ring in 1965, we want to make sure that we assign that annual ring to the correct year when it happened. And this is done through a process called cross-dating, which is by far the single most important principle in dendrochronology. Once we’re certain that we’ve assigned the exact calendar year to the formation of each annual ring, then we can correlate the growth patterns of these trees with climate or weather records from a given area, monthly temperature and precipitation for example, and use that information to understand how climate is affecting tree growth. And that can then lead us into the next stage, which would be the possible reconstruction of climate back in the past, before the beginning of the actual weather records that we have available.

Pulse of the Planet’s Science Diaries are made possible by the National Science Foundation. I’m Jim Metzner.

Science Diaries: Tree Rings Cross dating

Before dendrochronologists attempt to interpret a tree's rings, they make sure to assign each ring to its corresponding year.
Air Date:05/17/2010
Scientist:
Transcript:

ambience: dawn chorus

JM: Tall, sensitive, and loaded with hundreds of rings? Sounds like the kind of tree that any dendrochronologist would just love to cross-date! Welcome to Pulse of the Planet's Science Diaries, a glimpse of the world of science from the inside.

EC: When we extract a core of wood from a tree, one of the first things we do is to look very carefully at the core of wood and see first of all how many rings do we have in the tree. For studies of past climate, we want to have as many rings as possible so we can look at climate as far back into the past as possible. But the other thing we look for is evidence for changes in growth from year to year. In the jargon of dendrochronology that's called sensitivity. And when we say a tree is sensitive, we're saying that it responds to changes in its growth environment from year to year. Probably most commonly, these changes in growth from year to year are caused by changes in climate.

JM: Climate studies are central to the work of the Tree Ring Laboratory at Lamont Doherty Earth Observatory in Palisades, New York, where Edward Cook is director.

EC: If there was a drought in 1965, as there was here in the New York metropolitan area, and we see a narrow ring in 1965, we want to make sure that we assign that annual ring to the correct year when it happened. And this is done through a process called cross-dating, which is by far the single most important principle in dendrochronology. Once we're certain that we've assigned the exact calendar year to the formation of each annual ring, then we can correlate the growth patterns of these trees with climate or weather records from a given area, monthly temperature and precipitation for example, and use that information to understand how climate is affecting tree growth. And that can then lead us into the next stage, which would be the possible reconstruction of climate back in the past, before the beginning of the actual weather records that we have available.

Pulse of the Planet's Science Diaries are made possible by the National Science Foundation. I'm Jim Metzner.