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Thousands of scientists have been working to determine the ultimate effect of carbon on our climate, but a University of Tennessee at Knoxville professor just got $880,000 to find out what it's doing in the dirt.

Look in any eighth-grade science class and you'll likely find a poster illustrating the carbon cycle. Arrows of carbon lead from cartoon trees up to a cartoon sky. The arrows swirl around in the air until finally leading back down to the surface.

What carbon does in the air -- in the form of greenhouse gas and ozone -- has been the topic of much research and debate.

But it's when carbon hits the dirt that scientists scratch their heads, according to Aimee Classen, associate professor of ecology and evolutionary biology.

Thanks to a U.S. Department of Energy grant, Classen and her students are looking for what happens to carbon in soil -- and particularly what things that live in soil, such as fungi and bacteria, do with it.

"It's clear that these little microbes have a huge impact on carbon in soils. People just haven't studied them because they are hard to look at," Classen said.

Using PVC pipe filled with dirt, Classen is isolating soil samples with various mesh webbings. Some compartments have root systems, some have mycorrhizae -- a fungus that attaches to plant roots and forms vast symbiotic colonies -- while others have different soil bacterias. The plan is to put carbon into the samples and see what happens.

One pipe is placed in the Oak Ridge National Laboratory reservation in Tennessee, another will go in a peat bog in Minnesota and a third will be studied in a lowland tropical forest in Peru.

"We know that plants can affect carbon, because they can take carbon out of the atmos-phere and put it into the soil. We don't have a good idea of how fungi and other soil bacteria impact the carbon cycle in different ecosystems," Classen said.

The research will fill a big gap in carbon models, she said. That could help climate scientists make more accurate models in the future, which will lead to more accurate climate predictions.

"The perfect result would be for us to say these things greatly impact carbon cycles and it's the same everywhere -- but I don't think that's going to happen," Classen said.

Tom Bruns, professor of fungal ecology and systematics at the University of California, Berkeley, said the research could be a great help to the field. Bruns is not connected to Classen's research or the grant.

"A large percentage of the carbon on the planet is below ground. What we know is that the fungi are sort of our pipelines for it -- for the plants. But the details of those particulars are not well known, particularly in nature," Bruns said. "For all those reasons, I think it's definitely a worthwhile project."

Contact staff writer Louie Brogdon at or at 423-757-6481.