Microorganisms in the soil produce about seven times more carbon dioxide (CO2) every year than all human sources combined. Ideally, the release of CO2 from soils is balanced by CO2 consumed by plants. Very little is known about soil microbes or how they will respond to climate and environmental changes.

A project led by Cornell researchers to better understand soil microbes and their role in the carbon cycle has received a three-year, $3.59 million grant from the U.S. Department of Energy.

“Since soil microbes produce so much CO2, even a small increase or decrease in their activity could have major implications in the fate of our planet,” said Dan Buckley, associate professor of soil and crop sciences and the project’s principal investigator (PI). “Our project seeks to understand the role of microbes in the soil carbon cycle so that we can better predict how their activities might respond to environmental change.”

Both temperature and precipitation, two factors affected by climate change, have large effects on how much carbon soil microbes convert to carbon dioxide, which becomes a greenhouse gas in the atmosphere. But we don’t know much about different species of microbes in soils, how they interact with each other, and how they will respond in future climate scenarios, Buckley said.

Computer models predict the global carbon cycle, its role in climate change and impact on the planet. “We can model fairly well how the oceans and atmosphere are going to behave, but most models vary dramatically in predicting how soil is going to behave in the future. And that largely relates to the fact that we don’t understand what microorganisms are doing to carbon in the soil,” Buckley said.

To identify microbes and study their roles, Buckley and his team will use stable carbon isotopes with signatures that can be tracked. Researchers will add isotopically labeled carbon to soil, and they will analyze microbe DNA, protein and metabolites to track which organisms are using the added carbon. Then they will perform experiments under different environmental conditions to see how carbon is exchanged between organisms, how much is released as CO2 and how the microbes operate.

Co-principal investigators include Trent Northen at Lawrence Berkeley National Laboratory, Mary Lipton at Pacific Northwest National Laboratory, Will Wieder at the University of Colorado, Boulder, and Johannes Lehmann, Cornell professor of soil and crop sciences.