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Dendrochronologists at MU use tree rings to reveal answers from the past

Monday, September 28, 2009 | 2:35 p.m. CDT; updated 11:15 a.m. CDT, Tuesday, September 29, 2009
Michael Stambaugh prepares a tree sample from Medicine Creek, Mo. at the Missouri Tree-Ring Laboratory where he works as a research associate. Stambaugh is a dendrochronologist who has learned how to measure tree rings to determine climate changes or cultural influences that occurred during a particular time and in a particular region.

COLUMBIA — There's almost no end to what Mike Stambaugh can do with tree rings. He can tell you how old a building is, about the culture of a region or even when wildfires, volcanic eruptions or meteor impacts happened or are likely to happen again.

Stambaugh is a dendrochronologist and research associate in the MU forestry department. He and his colleagues do research not only in Missouri but also around the United States and — in Stambaugh’s case — even around the world. Stambaugh’s expertise has taken him to Costa Rica and Poland.

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Dendrochronologists can use tree rings to determine climate changes or cultural influences that occurred during a particular time and in a particular region. They can determine the stability of the land and the rate of erosion by examining where rocks hit trees. Stambaugh said they have the ability to use the cell structure and anatomy of a tree ring to distinguish between injuries caused by fires, frost or floods.

“We think of trees as clocks,” Stambaugh said.

Dendrochronologists need at least 100 rings on a piece of wood to do their work. Tree rings typically have two portions: a lighter-colored early wood ring indicating spring and a darker latewood ring indicating summer. The two bands together make up one year. In Missouri, the light band coincides with April and May and the dark band with June through August. The two colors allow scientists to calculate nearly the exact month an incident occurred.

MU research specialist Joe Marschall and graduate student Adam Bale use tree rings to do fire analyses. Bale is using Rocky Mountain junipers to verify the history of wildfires in North Dakota’s Teddy Roosevelt National Park. Marschall is dating 45 pieces of wood from Wisconsin in hopes of determining how frequently wildfires have occurred there.

“I really enjoy the hands-on history of tree rings,” Marschall said.

Folks in Wisconsin worry they might be overdue for a wildfire because many forests have not burned there in about 100 years. In an effort to help, Marschall is trying to calculate not only how often wildfires happen there but also whether they occurred in times of droughts or as a result of other human factors. If he succeeds, he will be able to predict when another wildfire might break out.

The process of dating trees starts by obtaining samples, which are organized and sanded down so that every cell is clear and ready for measurement. Next, they’re put under a microscope so that scientists can use a specialized computer system to measure them precisely, down to one one-hundredth of a millimeter.

If the age of the wood is unknown, Stambaugh or the others can match the ring-width patterns to masters developed from old and live trees.

Research assistant Erin Abadir is helping with an ancient wood project in which scientists are analyzing wood found in Missouri’s buried forests or taken from rivers. They hope to reconstruct the history of climate changes spanning thousands of years and to create the longest tree-ring record in North America, spanning 14,000 years. These records are the basis for radiocarbon and archaeological dating and for placing historic events such as volcanic eruptions and meteor impacts.

“I really like this job because you can go out in the field and then come back and uncover history,” Abadir said. “It’s always interesting to me.”

The MU laboratory has collection trees from North America that range from 200 to more than 20,000 years old. Trees that are at least 5,000 years old are put in a walk-in refrigerator after they have been analyzed. The refrigerator is kept at about 39 degrees, and the samples are wrapped and vacuum-sealed. This retains the wood’s moisture and prevents shrinking. Other wood is stored off-campus.

Stambaugh said one can’t learn dendrochronology solely from books; one must learn from someone. For Stambaugh, that person was MU research professor Richard Guyette.

 “I felt like it was an old-style apprenticeship, where the student works with and learns from the master,” Stambaugh said. “The problem is there are a few people with this expertise. It’s not every day you meet a dendrochronologist.”

Guyette has been working with tree rings for 32 years and feels dendrochronologists have a unique role in forestry because they recognize a tree’s intricate ability to record history and how to extract information to the benefit of forest and ecosystem management.

“In a sense tree rings are an informational science,” Guyette said. “They provide information about growth, plants, humans and climates. Our work involves reading the trees and extracting this special information.”


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Comments

Christopher Foote September 29, 2009 | 10:16 a.m.

I'd be interested to know how they infer temperature data from the tree rings.

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