06 July 2010

Breath of the Earth: Cycling carbon through terrestrial ecosystems

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New data on photosynthesis and respiration will improve models, researchers say

Two recent international studies are poised to change the way scientists view the crucial relationship between Earth's climate and the carbon cycle. These reports explore the global photosynthesis and respiration rates—the planet's deep "breaths" of carbon dioxide, in and out—and researchers say that the new findings will be used to update and improve upon traditional models that couple together climate and carbon.

The two reports will be published online by the journal Science at the Science Express Web site at 6 p.m., US ET, Monday, 5 July. Science is published by AAAS, the nonprofit science society.

Christian Beer from the Max Planck Institute for Biogeochemistry in Jena, Germany, along with colleagues from 10 other countries around the world, first take a look at Earth's Gross Primary Production, or GPP, which represents the total amount of carbon dioxide that terrestrial plants breathe in through photosynthesis each year. With a novel combination of observations and modeling, they estimate the total amount of carbon dioxide that the world's plant life inhales annually is 123 billion tons.

Then, Miguel Mahecha, also from the Max Planck Institute for Biogeochemistry, and another international team of researchers settle a long-standing debate over the effects of short-term variations in air temperature on ecosystem respiration, or the Earth's exhalation of carbon dioxide back into the atmosphere. They show that the sensitivity of ecosystem respiration to short-term variations in temperature is similar around the world. The researchers also suggest that factors other than temperature, such as the slow, ongoing transformations of carbon in the soil and water availability, appear to play crucial roles in long-term ecosystem carbon balances.

Together, these findings shed more light on the global cycle of carbon into and out of the atmosphere and how those processes are coupled with Earth's ever-changing climate. The researchers analyzed vast amounts of climate and carbon data from around the world, and they say their results should help to improve the validity of predictive models and help resolve how climate change might affect the carbon cycle—and our world—in the future.

(EurekAlert!)

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