Not All Soil CO2 Effluxes Are Created Equal: Root-Derived Contributions in Prairie and Corn Biofuel Systems.

Soil CO2 efflux can be attributed to two main sources: soil-derived and live root-derived. The former includes microbial decomposition of soil organic matter, while the latter includes root respiration and rhizo-microbial decomposition of root-derived exudates. Plant respiration and decomposition of live-plant derived exudates includes carbon that was recently taken out of the air through photosynthesis. Just as human respiration is not considered a GHG emission, this plant respiration represents a closed loop with no net addition of CO2 to the atmosphere; thus plant respired CO2 is not a GHG. Studies which report soil CO2 effluxes of cropping systems without distinguishing between soil and plant-derived sources can therefore be misleading. To gain a better understanding of GHG emissions of potential biofuel cropping systems, we separated soil CO2 efflux into soil- and live root-derived sources throughout the season using a shading method.