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Title: Contrasting warming and ozone effects on denitrifiers dominate soil N2O emissions

Author
item QUI, YUNPENG - Nanjing Agricultural University
item JIANG, YU - Nanjing Agricultural University
item GUO, LINJIN - North Carolina State University
item Burkey, Kent
item ZOBEL, RICHARD - North Carolina State University
item SHEW, DAVID - North Carolina State University
item HU, SHUIJIN - North Carolina State University

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2018
Publication Date: 8/29/2018
Citation: Qui, Y., Jiang, Y., Guo, L., Burkey, K.O., Zobel, R., Shew, D., Hu, S. 2018. Contrasting warming and ozone effects on denitrifiers dominate soil N2O emissions. Environmental Science and Technology. 52:10956-10966.

Interpretive Summary: Nitrous oxide is a potent greenhouse gas with a global warming potential 300 times greater than that of carbon dioxide, and is a factor in the depletion of the stratospheric ozone that shields the earth from ultraviolet light. Globally, agricultural soils are a major source of nitrous oxide from microbial processes associated with the use of manure and chemical fertilizers. A team of scientists from Nanjing Agricultural University (China), North Carolina State University, and USDA-ARS showed that climate change factors impact nitrous oxide production through effects on the soil microbes. In a field study with soybean, season-long elevated temperature treatment stimulated nitrous oxide emission and the soil microbes associated with nitrous oxide production. In contrast, elevated ozone had no significant effect on nitrous oxide production. Together, these findings show that climate change may alter nitrous oxide production from agricultural systems.

Technical Abstract: Nitrous oxide (N2O) in the atmosphere is a major greenhouse gas and is primarily originated from two microbial N transformation processes, i.e., nitrification and denitrification. Climate change factors such as warming and elevated ozone (eO3) affect N2O fluxes, but the direction and magnitude of these effects are uncertain and the underlying mechanisms remain unclear. We examined the impact of simulated warming (control + 3.6 C) and eO3 (control + 45 ppb) on soil N2O fluxes in a soybean agroecosystem. Results obtained showed that warming significantly increased soil labile C, microbial biomass carbon (MBC), and the rate and the sum of N2O emissions. In contrast, eO3 reduced soil labile C and MBC, and had no significant effect on N2O. More interestingly, warming and eO3 differentially affected the abundances of key genes responsible for nitrification (amoA of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA)), and denitrification (N2O production genes nirS and nirK, and N2O consumption gene nosZ). In particular, warming enhanced the two N2O production genes (nirS and nirK), but eO3 significantly reduced all three denitrification-related genes. In addition, N2O emissions were positively correlated to the abundances of denitrifiers. Together, these findings show that climate change factors may induce rapid shifts in the abundances and composition of N2O-producing microbes, thereby altering N2O production.