Effects of elevated CO2 and O 3 on N-cycling and N 2O emissions: a short-term laboratory assessment
2012
Decock, Charlotte | Six, Johan
BACKGROUND AND AIMS: Elevated atmospheric CO2 (eCO2) and tropospheric O3 (eO3) can alter soil microbial processes, including those underlying N2O emissions, as an indirect result of changes in plant inputs. In this study, effects of eCO2 and eO3 on sources of N2O in a soybean (Glycine max (L.) Merr.) agroecosystem in Illinois (SoyFACE) were investigated. We hypothesized that increases in available C and anaerobic microhabitat under eCO2 would stimulate N2O emissions, with a proportionally larger increase in denitrification derived N2O (N2OD) compared to nitrification plus nitrifier denitrification derived N2O (N2ON+ND). We expected opposite effects under eO3. METHODS: Isotopically labeled 15NH 4 14 NO3 and 14NH 4 15 NO3 were used to evaluate mineral N transformations, N2OD, and N2ON+ND in a 12-day incubation experiment. RESULTS: We observed minimal effects of eCO2 and eO3 on N2O emissions, movement of 15 N through mineral N pools, soil moisture content and C availability. Possibly, altered C and N inputs by eCO2 and eO3 were small relative to the high soil organic C content and N-inputs via biological N2-fixation, minimizing potential effects of eCO2 and eO3 on N-cycling. CONCLUSION: We conclude that eCO2 and eO3 did not affect N2O emissions in the short term. However, it remains to be tested whether N2O emissions in SoyFACE will be unaltered by eCO2 and eO3 on a larger temporal scale under field conditions.
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