Microbes in soil pose global-warming challenge

Fri, 01/11/2013

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Brendan Lynch
KU News Service
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LAWRENCE — A grim hazard of climate change is that “positive feedbacks” will augment the warming induced by human activities.

One such a positive feedback loop that could spiral out of control lies directly underfoot. When microorganisms in the soil break down organic matter like dead plants, they also emit heat-trapping gases into the atmosphere. The warmer the world gets, the busier the microorganisms in many places could become, producing relatively more greenhouse gases.

“There is great concern that with human-induced climate change in the coming century, warmer temperatures will increase the rates at which microbial activity in the soil occurs, and that in turn will drive increased fluxes of greenhouse gases into the atmosphere,” said Sharon Billings, associate professor of ecology and evolutionary biology at the University of Kansas.

Microbial activity in the soil generates carbon dioxide, nitrous oxide and methane, all of which add to global warming. Indeed, emissions from soil-dwelling microorganisms worldwide constitute a “huge governing factor in the Earth’s climate,” according to the KU researcher.

Thus, with a hotter climate, increased emissions by soil biota could contribute severely to yet more global warming in the coming decades — at levels akin to other major systems that threaten positive feedback loops in response to a warming planet, such as melting reflective sea ice or methane-rich Siberian permafrost.

But according to Billings, who also works at the Kansas Biological Survey, scientists who forecast the Earth’s changing climate urgently require a better grasp on these microorganisms’ role in global warming and the reasons behind any change in their behavior with warming.

“Our work highlights what we really need to study – and model – to understand what is going to happen in the future,” Billings said. “We already know that if you warm soils, you’re going to get more CO2 in most cases. The question is how much, and why.”

Billings stressed that scientists must understand the specific means by which warming boosts microbial respiration in soil – a key process that produces CO2.

“When you warm soils in the field or warm soils in the lab and you measure how much CO2 comes off, that CO2 is the end result of many different processes prior to cells’ respiration,” she said. “There’s a big effort in my lab to try to parse those different processes out and find out what the temperature influence is on each of them.”

Billings and her team are researching several possible mechanisms behind increased greenhouse-gas production from soil microbes. “You have to ask, ‘Is the microbial population increasing in size? Is that a feature driving warmer soils to emit more CO2?’” she said. “Or, are the microbes changing what they’re going after? Are they going after cellulose instead of sugar, or going after lignin instead of cellulose? We don’t know the answer to those questions, and that’s really where we need to go.”

With such an understanding, a more finely tuned estimation of the microbial influence on Earth’s warming climate is possible, taking into account precipitation and regional climate differences as well.

There might be little that humankind can do to change the rates at which microorganisms break down organic matter in soil around the planet. “We have very little control of that relative to human-driven processes,” Billings said. “These ecosystems are going to function in response to environmental features like temperature and precipitation. And human activities are changing those patterns.”



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Poet offers insights to Jayhawk experience through wordplay "Welcome to KU. Where questions rest, in stacks of answers from the past. …" Listen to Topher Enneking, a spoken word poet and former KU football player, as he weaves the experience of KU and its traditions through this storytelling and wordplay performance. Learn more about KU traditions at http://www.ku.edu/about/traditions/. Welcome to KU. Where questions rest in stacks of answers from the past. Where dreams crawl out of bed And learn to walk Uphill both ways. Where freshmen stand on stilts And hang from the rafters, While the wheat waves In a fieldhouse Where the Phog rolls in Helping us to see Through the past into the future. Haunting hosts giving handouts in a heritage Too heavy to grasp til you add to it. So it may be born anew, Allowing our boots to stand in the ash of oppression’s hate But shine bright as the sun While war cries of warriors past Ring in our ears long after their battles are won. Memorials telling time, “you don’t have to stand still.” Because the top of the world Is just up that Hill. Where our natural history is an awe-struck echo Of world’s fair and equal Past, present and future, prelude and sequel. Where our flags fly above planes. Where we build in chalks that can’t be erased. Stone edifices made to last So you would walk Past their doors, down their halls And let your voice fill their room. Because only in empty silence can destruction loom. So stand tall. Wrap your arms around this crowd Sing our alma mater and sing it out loud. Let your voice sing in chorus and reach other nations Beckoning new Jayhawks to spark new collaborations Because you are the mortar that will hold these walls upright. Your future Your dreams are why Jayhawks did fight For the tradition before you Was merely prelude For what will come next now that you’re at KU.


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