Submerged Ancient Oaks Help Reduce Global Warming

"If a tree is submerged in water, its carbon will be stored for an average of 2,000 years," said Richard Guyette, director of the MU Tree Ring Lab and research associate professor of forestry in the College of Agriculture, Food and Natural Resources.

"If a tree falls in a forest, that number is reduced to an average of 20 years, and in firewood, the carbon is only stored for one year," he explained.

The research team studied trees in northern Missouri, a geographically unique area with a high level of streamside, or riparian, forests. They discovered submerged oak trees that were as old as 14,000 years, potentially some of the oldest discovered in the world.

Dr. Richard Guyette goes underwater to learn more about carbon storage and release. (Photo courtesy MU Tree Ring Lab)

While a tree is alive, it has a high ability to store carbon dioxide, a greenhouse gas that is a major contributor to global warming. Then as the tree falls and begins to decay, that carbon dioxide is released back into the atmosphere.

This carbon storage process is not just ancient; it continues today as additional trees become submerged, said Dr. Guyette.

"Carbon plays a huge role in climate change and information about where it goes will be very important someday soon," said Michael Stambaugh, research associate in the MU Department of Forestry.

"The goal is to increase our knowledge of the carbon cycle, particularly its exchange between the biosphere and atmosphere," he said. "We need to know where it goes and for how long in order to know how to offset its effects."

The research team used tree-ring dating and radiocarbon dating using the naturally occurring radioisotope carbon-14 to document the distribution through time and carbon storage of oak wood in trees buried by streams and floodplains in northern Missouri.

The results showed that oak wood has been accumulating in Midwest streams continually since at least 14,000 years ago.

The median residence time of an oak bole in the study streams was 3,515 years.

More than 30 percent of sampled oak wood entered the floodplain sediments and stream waters within the last 1,000 years, and a few samples dated to the last 150 years.

"Recent human impacts on streams have altered the dynamics of oak input and sequestered carbon with unknown long-term consequences," the researchers wrote in their study.

These findings document a continuous and long-term form of carbon storage that is sensitive to changes in climate and human activities that alter patterns of flowing water.

Submerged trees could be a valuable source of income for landowners when a carbon emissions trading market becomes standard practice in the United States as it is today in Europe.

"Farmers can sell the carbon they have stored in their trees through a carbon credit stock market," Guyette said. "Companies that emit excess of carbon would be able to buy carbon credits to offset their pollution."

The study "The Temporal Distribution and Carbon Storage of Large Oak Wood in Streams and Floodplain Deposits" was published in the journal "Ecosystems."

The findings were discussed this week at the First American Dendrochronology Conference - AmeriDendro 2008 - held at the University of British Columbia in Vancouver. The primary focus of the conference is on tree-ring research in North and South America and its application in climatology, environmental sciences, archaeology, geology, resource management, and conservation.

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