The Hot Zone

Soil critters

Posted by Alison Hawkes on April 26, 2010
Category : Climate Science and Scientists

We’ve heard a lot about methane bubbling out of the Arctic permafrost. But just as much concern over soil carbon emissions is factoring into global warming prediction models.

The idea is that higher temperatures activate the gazillions of microbes in the soil, and they hungrily chomp their way through plant debris and the like, in the process creating enzymes that respirate lots of carbon molecules into the atmosphere.

Rich soil in Alaska's boreal forest. Credit: Steven D. Allison

Rich soil in Alaska's boreal forest. Credit: Steven D. Allison

It turns out that the interplay between climate and microbes is a little more complicated than previously thought. A study published this month in Nature Geoscience showed that microbes release lots of carbon initially in response to atmospheric warming, but can overheat and taper off over time. Under higher temperatures, their “carbon-use efficiency,” a measurement standard the scientists are using to establish how well the microbes process carbon, can be affected by changes to their physiological systems. As microbe growth decreases, so does their production of carbon-releasing enzymes, according to new research.

In short, the microbes have just not adapted to the extra heat. “When we developed a model based on the actual biology of soil microbes, we found that soil carbon may not be lost to the atmosphere as the climate warms,” said Steve Allison of UC Irine and a lead author in the study, who developed a computer model to test how efficiently microbes were decomposing soil carbon after several years of experimental warming.

But that doesn’t mean that microbes won’t adapt to the higher temperatures over time, or that some new heat-insensitive species might take over and continue the breakdown of carbon. Also, the response could change in differing ecosystems. The researchers started out in Massachusetts but have begun collecting samples in Alaska, California, Maine, and Costa Rica to study.

It’s easy to overlook the teeny critters that give life to soil. But their goings-about is critical to climate science and to a warming world.

-Alison Hawkes

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