February 27, 2017

Quantifying Atmospheric Carbon With Soil Microbes

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In fall of 1991, eight men and women were sent to live in a three-acre glass and steel dome in the middle of Arizona’s scorching desert. Referred to as Biosphere II, the complex aimed to model the Earth’s biosphere — even containing a field to grow crops. The two year experiment was designed to test if humans were capable of surviving in an artificial ecosystem.

Less than a year later, the project lay abandoned. The level of oxygen dropped drastically to levels seen on Mount Everest. Despite significant debate, it was finally determined that the reason for such a drastic change was the soil. Scientists wanted to ensure that human occupants would have enough food supply, so they increased the soil’s fertility. This seemingly harmless act, though, altered microbial activities and lead to catastrophic failure.

According to Prof. Daniel H. Buckley, soil and crop sciences, the project had a few key lessons and highlighted the significance of soil in our ecosystem.

“Knowing what the soil does matters. Failing to understand how it works leads to disastrous consequence,” Buckley said.

Buckley serves as the principal investigator on a project to investigate soil-microbial interactions. Knowing how soil behaves matters even more in the age of climate change. The terrestrial biosphere — vegetation, soil etc. — holds a large fraction of global carbon and nearly 70 percent of the organic carbon in terrestrial systems is found in soil.

“The degree to which it stores carbon is good for us. The degree to which it respires is not, because it contributes to the amount of carbon found in the atmosphere,” Buckley said.

In his lab at Cornell, Buckley and his colleagues shed light on how soil responds to changing environmental conditions brought about by climate change, such as higher atmospheric carbon dioxide, higher temperature and lower precipitation. Specifically, they study the connections between microbial activity and carbon-cycle transformations, which remain poorly described.

The project is divided into three main parts. First, the team hopes to characterize the functional traits of microorganisms that help mediate the mineralization of organic matter in the soil. Second, they aim to determine the degree to which such mineralization depends on variations in microbial traits. Finally, Buckley hopes to quantify the variation in the carbon cycle due to variations in microbial-soil interactions.

To begin testing their hypothesis, the team aims to label carbon containing molecules in decomposing matter with isotopes. Upon feeding on this, microbes imbibe this carbon into their DNA. Researchers can then sequence their genome to understand the mechanisms of their interactions with molecules in the soil.

One of the greatest challenges facing such research is that microbes do not work alone. In fact, the collaborative nature of organisms makes it harder to predict how the system will respond to changes in the environment.

“It’s like how the economy works. You get a chip from China, software from somewhere else and assemble the whole thing in the U.S. The job is distributed and done by those that are most efficient at it. But that makes it really complex,” Buckley said.

While this would be an important first step in understanding how microbe-soil interactions occur, Buckley hopes to predict how these interactions may change, perhaps to even successfully recreate Biosphere II.