Researchers have understood, and have been concerned for some time, that warmer temperatures will speed up the rate of decomposition of stored organic matter in soils, a process that ordinarily is slow. This faster rate of decomposition, in turn, could further increase carbon released to the atmosphere and cause even greater global warming.
"This feedback loop is one of our biggest worries with global warming, simply because the amount of carbon stored in soil is so huge," Harmon said. "Increased release of that soil carbon could offset much of what we're trying to accomplish with increased growth of live vegetation in forests. And this is a special concern in northern latitudes."
In the past, estimates of that process were usually based on average temperature increases that were expected, Harmon said. But in the real world, temperatures vary greatly, from day to night, season to season, through heat waves and cold spells. And that variability, researchers say, changes the biological equation considerably and can make averages misleading.
"If the response of soil respiration to temperature was a straight line, then temperature variability would not be important," Harmon said. "However, the response is curved, which means that as temperature variability increases, so does the average response. This general phenomenon is known as Jensen's inequality, but it had not previously been applied to soil respiration."
In simple terms, less variability will equate to less soil carbon release. In the new analysis, considering the effects of variability, scientists
|Contact: Mark Harmon|
Oregon State University