Ten years of elevated CO affects soil greenhouse gas fluxes in an open top chamber experiment.

Background: The production and consumption of greenhouse gases (GHGs) in soils are largely regulated by biological processes. Increasing atmospheric CO may alter these processes, thereby affecting GHG emissions and their feedbacks to climate. Methods and aims: Here, we used an open top chamber (OTC) experiment to examine the effects of elevated CO for ten years on soil GHG fluxes in a Quercus mongolica dominated system in northeastern China. Results: Our results showed that elevated CO increased soil CO emissions, consistent with increased microbial biomass and the abundance of arbuscular mycorrhizal fungi and actinomycetes. Additionally, elevated CO increased CH uptake due to stimulated growth of methanotrophs. The seasonal mean soil NO flux was not changed by elevated CO, consistent with unchanged ammonia oxidizing bacteria, archaea and denitrifiers, which was probably due to large variations between the individual OTCs and with time. However, seasonal cumulative soil NO emissions increased by 64.7% under elevated CO. Our results also hinted that nitrification by ammonia oxidizing archaea was the major process of soil NO emissions. Conclusions: In our study elevated CO increased soil GHG emissions and the cumulative global warming potential by 27.8%, causing an important positive feedback to climate change. [ABSTRACT FROM AUTHOR]