The response of soil CO2 efflux under trees grown in elevated atmospheric CO2: A literature review

As elevated atmospheric CO2 concentrations typically result in larger root systems and increased litter production, also soil CO2 efflux is expected t o be enhanced in elevated CO2. In a review of the related literature we did find a mean stimulation of soil CO2 efflux of 37 %, but large differences occurred among different experiments. In some experiments, soil respiration was not or even negatively affected, despite significant increases in root biomass. We hypothesize that the lack of response of soil CO2 efflux to in creased CO2 concentrations in those experiments was due to a retardation of soil organic matter and possibly also litter decomposition.