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Doctoral candidate Jessica Bryant (left), Aimee Classen (middle), and UT undergraduate student Kelsey Richesin (right) use Li-Cor 6400, a machine that measure carbon flux from soil.Carbon dioxide is key to life on Earth, but too much of the good thing can overheat the Earth’s surface and hurt the very things it supports. Thus, understanding how carbon cycles through the atmosphere is crucial to predicting its effects.

A UT professor has received more than $880,000 from the U.S. Department of Energy to investigate often-overlooked carbon cycle players.

Aimee Classen, associate professor of ecology and evolutionary biology, and her team will examine factors that influence carbon cycling below the ground and are not included in today’s carbon-cycle models.

“We know that tiny things that live in soil, like fungi, can regulate carbon processes in forests. However, our current soil models don’t consider what role fungal and plant root activity may play in soil carbon dynamics. Our project aims to fill this knowledge gap,” said Classen.

Classen and her team will investigate when soil fungi, called mycorrhizae, are a carbon source or a carbon sink, potentially having a great impact on the amount of carbon being released from the soil into the atmosphere.

Mycorrhizal fungi have a symbiotic relationship with plants. They live among the plants’ root structures, supplying the plant with soil nutrients and moisture. In return, the fungi get a supply of carbon to grow. The consumed carbon can go into the soil and stay there or get respired back to the atmosphere. But how much carbon is eaten and how much is respired may change depending on soil type—which is not considered in most models.

“We know fungi, and the bacteria they live with, can eat soil carbon, but the amount they eat and respire back into the atmosphere can depend on warming and if they live in a tropical or temperate forest. Thus, these interactions can have great implications for the carbon cycle by adding to or reducing the supply of the greenhouse gas in the atmosphere,” said Classen.

Classen and her colleagues will manipulate the carbon-degrading activity of fungi and plant roots in tropical, temperate, and peatland ecoregions, all with different soil types, to see how the tiny organisms in soil alter the carbon budgets of forests.

The study’s results will illustrate the potential impact the underground biological community has on the carbon cycle. It will also inform current models so they can better predict carbon storage responses to environmental changes, such as global warming and nitrogen deposition.

“These microscopic soil fungi and bacteria can have a large impact on how carbon is released from soil into the atmosphere. However, we are only beginning to understand how these organisms regulate forest carbon cycling,” said Classen.

Collaborators on the project include co-principal investigator Melanie Mayes and Gangsheng Wang of Oak Ridge National Laboratory; Jessica Bryant, a doctoral student, and W. Mac Post, a research professor, both in UT’s Department of Ecology and Evolutionary Biology; and Daniel Metcalfe of Swedish University of Agricultural Sciences, Forest Ecology and Management in Sweden.

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C O N T A C T :

Whitney Heins (865-974-5460,