Green Horizons

How do you determine whether an historical cabin still has original building materials from the early 1800s or whether completely new materials were used when it was reinforced more than a century later?

Mike Stambaugh shows the collection at the MU Tree Ring Laboratory. The lab houses wood samples of all different types and ages from around the country. One sample (larch tree) collected from northern Missouri dates back 22,500 years.

Well, if you’re Rich Guyette and Mike Stambaugh of the University of Missouri department of forestry, you’d look no further than the logs holding the cabin together. Guyette, forestry research professor, and Stambaugh, forestry research associate, are experts in dendrochronology, or tree-ring dating, and perform analysis, along with three technicians and a group of students, on log samples from across the country in their MU lab.

The case of the Hickam House at Rock Bridge State Park is one that hits close to home. Stambaugh and his wife were married at the cabin in 1999. Ten years later, the question of the age of the cabin’s pieces was raised. The deteriorating condition of the cabin will soon make it unsafe for visitors, and park officials plan to tear it down if the testing shows no historical materials are still present. Although the building materials are in question, it is believed the cabin rests on the original 1830s site.

Stambaugh had a professional – and personal – interest in clarifying the dates.

So one drizzly day in October, Stambaugh and Guyette took samples from a range of logs at the Hickam House, both inside and outside the one-room structure. They used an archaeological drill bit to procure cigar-sized cores, drilling to the middle-most ring, or pith, to get the best sample. In some spots they were able to take cross-sections from the ends of logs.

Mike Stambaugh drills outside the Hickam House to obtain a core sample.

Stambaugh places a core sample into a bag with Rich Guyette’s help.

Stambaugh looks at a cross-section taken from the house in the MU Tree Ring Laboratory.

“A cross-section is better than a core,” Guyette said. “There might be markers on rings that don’t go all the way around.” Cores contain only a small part of each ring.

Next up, back at the lab – Stambaugh and colleagues mounted and sanded each piece of wood, then measured each ring. Patterns will be run against a master tree-ring chronology pattern, compiled after surveying many logs from the same area.

“We look at the number of rings and how they vary,” Guyette said. Climate influences tree growth – in a wet year, a tree will make a fatter ring. In a drought, the year’s ring will be narrow.

The outside-most ring, of course, tells when the tree was cut.

“Tree rings can only fit one pattern in time,” Stambaugh said. “There’s really no error in it – if it’s not obvious, we won’t date it.” A certain number of rings – at least 60 or 70 – is necessary to definitively establish a tree’s place in time.

So far, Stambaugh said, he can tell all of the logs he sampled at the Hickam House were cut the same year – probably from the same forest. He is hoping a frost ring found about six years into the trees’ life will make the samples dateable.

Stay tuned!

The MU Tree Ring Lab works on five to 10 projects at any given time, Stambaugh said. They can help forest managers see how much injury burning does to a tree – how much “product” they are losing by participating in a burn program. They study climate change and climate cycles. They can tell how long a tree can last after being cut down – and it’s much longer if it falls in water rather than on the forest floor. They can see when mass erosions occurred by looking at rock injuries to trees. They can date archaeological pieces in historical buildings, as with the Hickam House.

“Anything that influences a tree – if it leaves a mark – we can date it,” Stambaugh said.

To learn more about MU’s Tree Ring Laboratory, including projects, publications and a slide show, visit their Web site at http://web.missouri.edu/~guyetter/

The MU Tree Ring Laboratory is in the news frequently. Some links and information about recent projects: A WATERY CARBON BANK This study about the carbon storage of oak in streams was published in the journal Ecosystems; news articles highlighting the research were published by Nature (http://www.nature.com/nature/journal/v454/n7201/index.html) and other online news sources. MYSTERY OF INFAMOUS ‘NEW ENGLAND DARK DAY’ SOLVED BY TREE RINGS This study was initially published in the International Journal of Wildland Fire, (http://www.publish.csiro.au/nid/115/issue/3790.htm). Later a news feature was done by wired.com (http://www.wired.com/science/discoveries/news/2008/05/dayintech_0519). Since then it has been picked up by many news sources including Discovery Channel, Science, NASA and Yahoo News. PERFECTLY PRESERVED LOG CABIN DISCOVERED NEAR WILDCAT DEN This project involved dating of an Iowa cabin in Muscatine County that received local (http://www.muscatinejournal.com/articles/2008/05/23/news/doc483798f65a662647261830.txt) and national press. The logs had scars that will provide some of the first information about Iowa historic fire frequency.