An Unexpected Loss of Soil Carbon Storage Caused by Elevated CO2 Concentration

Summary

It is widely recognized that elevated atmospheric CO₂ concentration increases tree photosynthesis and growth. Because of this, it is generally assumed that elevated CO₂ concentration will increase the carbon content of forest soil because tree photosynthesis is the source of forest soil carbon. This is the assumption of present global climate models. After 11 years of experimental study, however, the carbon content of surface-soil (top 20 cm) was significantly smaller in aspen tree stands exposed to elevated CO₂ concentration compared to aspen stands growing in the ambient atmosphere (normal CO₂ concentration). This result from a novel long-term DOE field experiment may require a re-assessment of how the carbon cycle is represented in global climate models.