Research led by an Indiana University biologist has found Elevated levels of atmospheric carbon dioxide accelerate carbon cycling and soil carbon loss in forests. Elevated levels of atmospheric carbon means that carbon stored in soil is not as stable as previously thought due to an increase in decomposition: “It’s been suggested that as trees take up more carbon dioxide from the atmosphere, a greater amount of carbon will go to roots and fungi to acquire nutrients, but our results show that little of this carbon accumulates in soil because the decomposition of root and fungal detritus is also increased”, Richard P. Phillips, lead author on the paper and an assistant professor of biology in the IU College of Arts and Sciences, said.
Forests remove a substantial amount of carbon dioxide from the atmosphere and much of the carbon is being stored in living woody biomass rather than as dead organic matter in soils. The research was conducted at the Duke Forest Free Air Carbon Dioxide Enrichment site in North Carolina. The authors also reported that nitrogen cycled faster in this forest as the demand for nutrients by trees and microbes became greater under elevated CO2.
“The growth of trees is limited by the availability of nitrogen at this site, so it makes sense that trees are using the ‘extra’ carbon taken up under elevated CO2 to prime microbes to release nitrogen bound up in organic matter,” Phillips said. “What is surprising is that the trees seem to be getting much of their nitrogen by decomposing root and fungal detritus that is less than a year old.”
“Most ecosystem models have limited representations of roots, and none of them include processes such as priming. Our results demonstrate that interactions between roots and soil microbes play an underappreciated role in determining how much carbon is stored and how fast nitrogen is cycled. So including these processes in models should lead to improved projections of long-term carbon storage in forests in response to global environmental change'” he said.
Reference: Richard P. Phillips,Ina C. Meier, Emily S. Bernhardt, A. Stuart Grandy, Kyle Wickings, Adrien C. Finzi. Roots and fungi accelerate carbon and nitrogen cycling in forests exposed to elevated CO2. Ecology Letters. 8 July 2012.