Three years after the US Department of Energy (DOE) elected to halt a series of high-profile forestry experiments, researchers are reporting that higher atmospheric carbon dioxide levels can increase soil carbon stocks, even if nitrogen limitations curtail the overall fertilization effect.
A team led by researchers at Oak Ridge National Laboratory in Tennessee announced the results this week, suggesting that increased carbon storage in the soils could help offset rising CO2 levels. Published in Global Change Biology, the study comes as part of the final phase of a 12-year experiment at a sweetgum plantation (the experiment officially ended in 2009). After cutting down trees and boring into the ground to analyse roots and soil carbon, researchers found that elevated carbon dioxide levels seem to have enabled the trees to extend their roots deeper into the soil, thus helping enhance carbon accumulation.
The Oak Ridge site is just one of several Free-Air CO2 Enrichment (FACE) experiments that the DOE elected to close down in 2008. Although some scientists pushed for their continuation, the agency decided that more could be achieved by harvesting their results and moving on to something new. The agency is now pumping money into an investigation of permafrost in the Arctic.