Effects of flooding-induced N2O production, consumption and emission dynamics on the annual N2O emission budget in wetland soil

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

Christian Juncher Jørgensen, Bo Elberling

Rapid flooding of wetland soil promotes subsurface N2O production in the soil and potential emission to the atmosphere in distinctive emission pulses. Changes in flooding frequency of wetland soil following future climate change will likely affect the timing and magnitude of nitrous oxide (N2O) emissions from the soil to the atmosphere. From October 2009 to October 2010, rapid flooding of a natural Danish wetland was observed twice in response to high precipitation events. A flooding induced N2O emission pulse (delay ~16 hrs; duration ~12 hrs; total emission 1.83 mg N2O-N m-2, max. emissions ~250 µg N2O-N m-2 hr-1) was observed when the soil conditions in the top soil had been oxidized for more than 2-3 weeks prior to flooding. This flooding induced N2O emission pulse constituted ~2.5% of the annual net N2O emissions of 0.74 kg N2O-N ha-1 yr-1. A net uptake of atmospheric N2O was observed during mid-summer when the WL was at its seasonally lowest counterbalancing ~6.4% of the total annual net N2O emission budget. Main surface emission periods of N2O were observed when the water level and associated peaks in subsurface N2O concentrations were gradually decreasing to soil depths down to 40 cm below the surface. These surface emission patterns are predominantly linked to variations in plant-mediated gas transport via Phalaris arundinacea and N2O producing/consuming processes in the root-zone. Soil flooding experiments using high-resolution N2O microsensors demonstrate very large N2O production and consumption capacities where >500 nmol N2O cm-3 were sequentially produced and consumed in less than 24 hrs. It is concluded that a higher future frequency of flooding induced N2O emissions will have a very limited effect on the net annual N2O emission budget as long as NO3- availability in the soil prior to rapid flooding is not dramatically increased.
TidsskriftSoil Biology & Biochemistry
Sider (fra-til)9-17
Antal sider9
StatusUdgivet - 2012

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