Globally important nitrous oxide emissions from croplands induced by freeze–thaw cycles

Wagner-Riddle, Claudia; Congreves, Katelyn A.; Ábalos, Diego; Berg, Aaron; Brown, S. E.; Ambadan, Jaison Thomas; Gao, Xiaopeng; Tenuta, Mario

doi:10.1038/ngeo2907

Cited by 231 publications

(149 citation statements)

References 49 publications

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“…With increasing postthaw emissions from bare as well as vegetated surfaces, future pan-Arctic N 2 O emissions likely exceed this estimate. At a global scale, this puts Arctic N 2 O emissions from thawing permafrost in the range of emissions from fossil fuel combustion, industrial processes, and biomass burning, the secondlargest anthropogenic N 2 O sources after agriculture (12,29).…”

Section: Role Of Soil Moisture and Vegetation In Regulating Arctic N 2 Omentioning

confidence: 99%

Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw

Voigt

Marushchak

Lamprecht

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

133

131

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Permafrost in the Arctic is thawing, exposing large carbon and nitrogen stocks for decomposition. Gaseous carbon release from Arctic soils due to permafrost thawing is known to be substantial, but growing evidence suggests that Arctic soils may also be relevant sources of nitrous oxide (N 2 O). Here we show that N 2 O emissions from subarctic peatlands increase as the permafrost thaws. In our study, the highest postthaw emissions occurred from bare peat surfaces, a typical landform in permafrost peatlands, where permafrost thaw caused a fivefold increase in emissions (0.56 ± 0.11 vs. 2.81 ± 0.6 mg N 2 O m −2 d −1 ). These emission rates match those from tropical forest soils, the world's largest natural terrestrial N 2 O source. The presence of vegetation, known to limit N 2 O emissions in tundra, did decrease (by ∼90%) but did not prevent thaw-induced N 2 O release, whereas waterlogged conditions suppressed the emissions. We show that regions with high probability for N 2 O emissions cover one-fourth of the Arctic. Our results imply that the Arctic N 2 O budget will depend strongly on moisture changes, and that a gradual deepening of the active layer will create a strong noncarbon climate change feedback.

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Section: Role Of Soil Moisture and Vegetation In Regulating Arctic N 2 Omentioning

confidence: 99%

Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw

Voigt

Marushchak

Lamprecht

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

133

131

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“…For example, Wagner-Riddle et al (2017) found that shortduration freeze-thaw cycles can account for 35-65 % of the annual direct N 2 O emissions from seasonally frozen croplands and that neglecting this contribution would lead to a 17-28 % underestimate of the global N 2 O source (direct + indirect) from agricultural soils. This type of variability poses a major challenge to bottom-up and top-down efforts to quantify N 2 O surface fluxes and attribute them to specific times, locations, and mechanisms.…”

mentioning

confidence: 99%

Top-down constraints on global N<sub>2</sub>O emissions at optimal resolution: application of a new dimension reduction technique

et al. 2018

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Abstract. We present top-down constraints on global monthly N 2 O emissions for 2011 from a multi-inversion approach and an ensemble of surface observations. The inversions employ the GEOS-Chem adjoint and an array of aggregation strategies to test how well current observations can constrain the spatial distribution of global N 2 O emissions. The strategies include (1) a standard 4D-Var inversion at native model resolution (4 • × 5 • ), (2) an inversion for six continental and three ocean regions, and (3) a fast 4D-Var inversion based on a novel dimension reduction technique employing randomized singular value decomposition (SVD). The optimized global flux ranges from 15.9 Tg N yr −1 (SVDbased inversion) to 17.5-17.7 Tg N yr −1 (continental-scale, standard 4D-Var inversions), with the former better capturing the extratropical N 2 O background measured during the HIAPER Pole-to-Pole Observations (HIPPO) airborne campaigns. We find that the tropics provide a greater contribution to the global N 2 O flux than is predicted by the prior bottomup inventories, likely due to underestimated agricultural and oceanic emissions. We infer an overestimate of natural soil emissions in the extratropics and find that predicted emissions are seasonally biased in northern midlatitudes. Here, optimized fluxes exhibit a springtime peak consistent with the timing of spring fertilizer and manure application, soil thawing, and elevated soil moisture. Finally, the inversions reveal a major emission underestimate in the US Corn Belt in the bottom-up inventory used here. We extensively test the impact of initial conditions on the analysis and recommend formally optimizing the initial N 2 O distribution to avoid biasing the inferred fluxes. We find that the SVD-based approach provides a powerful framework for deriving emission information from N 2 O observations: by defining the optimal resolution of the solution based on the information content of the inversion, it provides spatial information that is lost when aggregating to political or geographic regions, while also providing more temporal information than a standard 4D-Var inversion.

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“…More studies of long-term, multi-season N2O fluxes are needed to improve global estimates of agricultural N2O emissions (Reay et al, 2012;Wagner-Riddle et al, 2017). The optimal performance combined with its lower power and low maintenance 15 requirements make the TDLAS-TE suitable for N2O flux measurements under rugged field conditions in remote or rural areas where power quality can be a concern.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a lower-powered analyser and sampling system for eddy-covariance measurements of nitrous oxide fluxes

Brown¹,

Sargent²,

Wagner‐Riddle³

2017

Preprint

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Abstract. Nitrous oxide (N2O) fluxes measured using the eddy-covariance method capture the spatial and temporal heterogeneity of N2O emissions. Most closed-path trace-gas analyzers for eddy-covariance measurements have large-volume, multi-pass absorption cells that necessitate high flow rates for ample frequency response, thus requiring high-power sample pumps. Other sampling system components, including rain caps, filters, dryers, and tubing can also degrade system frequency 10response. This field trial tested the performance of a closed-path eddy-covariance system for N2O flux measurements with improvements to use less power while maintaining the frequency response. The new system consists of a thermoelectrically cooled tunable diode laser absorption spectrometer configured to measure both N2O and carbon dioxide (CO2). The system features a relatively small, single-pass sample cell (200 ml) that provides good frequency response with a lower-powered pump (~250 W). A new filterless intake removes particulates from the sample air stream with no additional mixing volume that could 15 degrade frequency response. A single-tube dryer removes water vapor from the sample to avoid the need for density or spectroscopic corrections, while maintaining frequency response. This eddy-covariance system was collocated with a previous tunable diode laser absorption spectrometer model to compare N2O and CO2 flux measurements for two full growing seasons (May 2015 to October 2016) in a fertilized cornfield in Southern Ontario, Canada. Both spectrometers were placed outdoors at the base of the sampling tower demonstrating ruggedness for a range of environmental conditions (minimum to maximum 20 daily temperature range: -26.1 to 31.6°C). The new system rarely required maintenance. An in situ frequency response test demonstrated that the cutoff frequency of the new system was better than the old system (3.5 Hz compared to 2.30 Hz), and similar to that of a closed-path CO2 eddy-covariance system (4.05 Hz) using shorter tubing and no dryer that was also collocated at the site. Values of the N2O fluxes were similar between the two spectrometer systems (slope = 1.01, r 2 = 0.96); CO2 fluxes as measured by the short-tubed eddy-covariance system and the two spectrometer systems correlated well (slope = 25 1.03, r 2 = 0.998). The new lower-powered tunable diode laser absorption spectrometer configuration with the filterless intake and single-tube dryer showed promise for deployment in remote areas.Atmos. Meas. Tech. Discuss., https://doi

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Globally important nitrous oxide emissions from croplands induced by freeze–thaw cycles

Cited by 231 publications

References 49 publications

Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw

Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw

Top-down constraints on global N<sub>2</sub>O emissions at optimal resolution: application of a new dimension reduction technique

Evaluation of a lower-powered analyser and sampling system for eddy-covariance measurements of nitrous oxide fluxes

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Globally important nitrous oxide emissions from croplands induced by freeze–thaw cycles

Cited by 231 publications

References 49 publications

Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw

Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw

Top-down constraints on global N&lt;sub&gt;2&lt;/sub&gt;O emissions at optimal resolution: application of a new dimension reduction technique

Evaluation of a lower-powered analyser and sampling system for eddy-covariance measurements of nitrous oxide fluxes

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Top-down constraints on global N<sub>2</sub>O emissions at optimal resolution: application of a new dimension reduction technique