Global warming making soil release more CO2

Washington, March 26 (ANI): Twenty years of field studies have revealed that as the Earth has gotten warmer, plants and microbes in the soil have given off more carbon dioxide (CO2).

The scientists calculated the total amount of carbon dioxide flowing from soils, which is about 10-15 percent higher than previous measurements.

That number - about 98 petagrams of carbon a year (or 98 billion metric tons) - will help scientists build a better overall model of how carbon in its many forms cycles throughout the Earth.

Understanding soil respiration is central to understanding how the global carbon cycle affects climate.

"There's a big pulse of carbon dioxide coming off of the surface of the soil everywhere in the world," said ecologist Ben Bond-Lamberty of the Department of Energy's Pacific Northwest National Laboratory.

"We weren't sure if we'd be able to measure it going into this analysis, but we did find a response to temperature," he added.

The increase in carbon dioxide given off by soils - about 0.1 petagram (100 million metric tons) per year since 1989 - won't contribute to the greenhouse effect unless it comes from carbon that had been locked away out of the system for a long time, such as in Arctic tundra.

This analysis could not distinguish whether the carbon was coming from old stores or from vegetation growing faster due to a warmer climate.

"But other lines of evidence suggest warming is unlocking old carbon," said Bond-Lamberty, so it will be important to determine the sources of extra carbon.

The researchers turned to previous studies to see if they could quantify changes in global soil respiration.

Bond-Lamberty and his colleague Allison Thomson, working at the Joint Global Change Research Institute in College Park, Maryland, examined 439 soil respiration studies published between 1989 and 2008.

They compiled data about how much carbon dioxide has leaked from plants and microbes in soil in an openly available database.

To maintain consistency, they selected only data that scientists collected via the now-standard methods of gas chromatography and infrared gas analysis.

The duo compared 1,434 soil carbon data points from the studies with temperature and precipitation data in the geographic regions from other climate research databases.

After subjecting their comparisons to statistical analysis, the researchers found that the total amount of carbon dioxide being emitted from soil in 2008 was more than in 1989.

In addition, the rise in global temperatures correlated with the rise in global carbon flux. (ANI)