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A climate change discovery in tiny bits of decomposing leaves

Jun 8, 2017

What do tiny pieces of decomposing leaves have to do with climate change? It turns out they’re nitrous oxide hot spots.

Nitrous oxide is a greenhouse gas that’s 300 times more potent than carbon dioxide.

Phil Robertson is a professor of ecosystem science at Michigan State University’s Kellogg Biological Station, and he's also with MSU's Department of Plant, Soil and Microbial Sciences.

He notes that nitrous oxide is produced naturally by microbes in soil.

“And we’ve known for a long time the nitrous oxide emissions from soil play a big role in the greenhouse gas content of the atmosphere, and we also now that human activity - especially farming - can affect nitrous oxide production by soils. But we haven’t really nailed down the microbial basis for where this happens in soil,” he says.

Until now.

Robertson, along with MSU professor Sasha Kravchenko and their team, discovered that miniscule pieces of decomposing leaves in the soil act like sponges to soak up water and provide the perfect microbial habitat for the bacteria that produce the nitrous oxide.

“The microbes just go to town. They love this high-water, carbon-rich environment,” he says.

An MRI for soil

So how did they do it? With microscopes and tomography, which Robertson says is like a small MRI unit, to examine small blocks of soil.

"We did this at the Argonne National Laboratory in Illinois, where they have a very powerful MRI scanner that's capable of penetrating soil. This is the kind of technology that we use in medicine to identify abnormalities in human physiology."

Robertson says they can use this technology to create a 3D picture of the soil particles and their moisture content. Then they used gas sampling to determine the source of the nitrous oxide that was coming off.

He says next, people can work to figure out how to control the hot spots.

“And designing farming practices to minimize these emissions is perhaps a next step,” says Robertson. “So it basically gives us another important piece of information for the agronomists to use to design more climate-friendly cropping practices.”

The study was published in the journal Nature Geoscience.