Carbon feedback from forest soils will accelerate global warming, study finds

After 26 years, the world's longest-running experiment to discover how warming temperatures affect forest soils has revealed a surprising, cyclical response: Soil warming stimulates periods of abundant carbon release from the soil to the atmosphere, alternating with periods of no detectable loss in soil carbon stores. Overall, the results indicate that in a warming world, a self-reinforcing and perhaps uncontrollable carbon feedback will occur between forest soils and the climate system, adding to the buildup of atmospheric carbon dioxide caused by burning fossil fuels and accelerating global warming. The study , led by Jerry Melillo , distinguished scientist at the Marine Biological Laboratory , appears in the Oct. 6 issue of Science. Melillo and colleagues began this pioneering experiment in 1991 in a deciduous forest stand at the Harvard Forest in Massachusetts. They buried electrical cables in a set of plots and heated the soil five degrees Celsius above the ambient temperature of control plots. Over the course of the 26-year experiment, which is still ongoing, the warmed plots lost 17 percent of the carbon that had been stored in organic matter in the top 60 centimeters of soil.