<p>Wetlands have spatially and temporally dynamic nitrous oxide (N<sub>2</sub>O) fluxes. Understanding diurnal patterns in N<sub>2</sub>O fluxes in wetlands can reveal short-term drivers and improve process-based models. An automated chamber system was used to determine N<sub>2</sub>O flux rates every 2.5 to 4&#xa0;h in a prairie pothole wetland in North Dakota during the 2013 to 2014 growing seasons under ponded, moist, and dry soil conditions. The wetland generally emitted N<sub>2</sub>O under all conditions, although median fluxes during ponded conditions were low over the two-year study. A significant diurnal N<sub>2</sub>O pattern was observed under dry soil conditions, but not in moist soil or ponded conditions. When soils were dry, daytime (~ 10:00–14:00; 2.43 ± 0.31 ng m<sup>-2</sup> hr<sup>-1</sup>) and late-day (~ 14:00–18:00; 2.20 ± 0.16 ng m<sup>-2</sup> hr<sup>-1</sup>) average N<sub>2</sub>O fluxes were 77% and 61% greater, respectively, than other times during the 24-hr diel cycle (&lt; 1.37 ng m<sup>-2</sup> hr<sup>-1</sup>). N<sub>2</sub>O flux was positively correlated to air (<i>r</i> = 0.58) and soil (<i>r</i> = 0.49) temperatures under dry conditions, while no significant correlations to environmental factors were observed under ponded and moist conditions. Incorporating diurnal patterns in N<sub>2</sub>O fluxes in wetlands and other ecosystems can improve extrapolations from daily to annual flux calculations and constrain global N<sub>2</sub>O inventories.</p>

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Diurnal Patterns of Nitrous Oxide Fluxes from a Seasonal Prairie Wetland

  • Derek R. Faust,
  • Brian A. Tangen,
  • Sheel Bansal

摘要

Wetlands have spatially and temporally dynamic nitrous oxide (N2O) fluxes. Understanding diurnal patterns in N2O fluxes in wetlands can reveal short-term drivers and improve process-based models. An automated chamber system was used to determine N2O flux rates every 2.5 to 4 h in a prairie pothole wetland in North Dakota during the 2013 to 2014 growing seasons under ponded, moist, and dry soil conditions. The wetland generally emitted N2O under all conditions, although median fluxes during ponded conditions were low over the two-year study. A significant diurnal N2O pattern was observed under dry soil conditions, but not in moist soil or ponded conditions. When soils were dry, daytime (~ 10:00–14:00; 2.43 ± 0.31 ng m-2 hr-1) and late-day (~ 14:00–18:00; 2.20 ± 0.16 ng m-2 hr-1) average N2O fluxes were 77% and 61% greater, respectively, than other times during the 24-hr diel cycle (< 1.37 ng m-2 hr-1). N2O flux was positively correlated to air (r = 0.58) and soil (r = 0.49) temperatures under dry conditions, while no significant correlations to environmental factors were observed under ponded and moist conditions. Incorporating diurnal patterns in N2O fluxes in wetlands and other ecosystems can improve extrapolations from daily to annual flux calculations and constrain global N2O inventories.