Respiration of nitrous oxide in suboxic soil

Soils are both a major source and sink of nitrous oxide (N 2 O), but the proportion of soil N 2 O production released to the atmosphere (termed the N 2 O yield) is poorly constrained due to the difficulty in measuring gross N 2 O production. The quantification of gross N 2 O fluxes would greatly improve our ability to predict N 2 O dynamics across the soil-atmosphere interface. We report a new approach, the 15 N 2 O pool dilution technique, to measure rates of gross N 2 O production and consumption under laboratory and field conditions. In the laboratory, gross N 2 O production and consumption compared well between the 15 N 2 O pool dilution and acetylene inhibition methods whereas the 15 NO 3 À tracer method measured significantly higher rates. In the field, N 2 O emissions were not significantly affected by increasing chamber headspace concentrations up to 100 ppb 15 N 2 O. The pool dilution model estimates of 14 N 2 O and 15 N 2 O concentrations as well as net N 2 O fluxes fit observed data very well, suggesting that the technique yielded robust estimates of gross N 2 O production. Estimated gross N 2 O consumption rates were underestimated relative to rates calculated as the difference between gross and net N 2 O production rates, possibly due to heterogeneous and/or inadequate tracer diffusion to deeper layers in the soil profile. Gross N 2 O production rates were high, averaging 8.4 ± 3.2 mg N m À2 day À1 , and were most strongly correlated to mineral nitrogen concentrations and denitrifying enzyme activity (R 2 = 0.73). Gross N 2 O production rates varied spatially, with the highest rates in soils with the best drainage and the highest mineral N availability. Estimated and calculated N 2 O consumption rates constrained the average N 2 O yield from 0.70 to 0.84. Our results demonstrate that the 15 N 2 O pool dilution technique can provide well-constrained estimates of N 2 O yields and field rates of gross N 2 O production correlated to soil characteristics, improving our understanding of terrestrial N 2 O dynamics.

show abstract

“…S1; Rhew & Abel, ). Nitrous oxide production and consumption also follow first‐order kinetics (Vieten et al ., , ).…”

Section: Methodsmentioning

confidence: 99%

A test of a field‐based ¹⁵N–nitrous oxide pool dilution technique to measure gross N₂O production in soil

Yang

Teh

Silver

2011

Global Change Biology

View full text Add to dashboard Cite

show abstract

“…Under low oxygen (O 2 ) availability, nitrifier denitrification and heterotrophic denitrification with N 2 O as intermediate become more relevant (Philippot et al, 2009). At stably anoxic conditions and low concentrations of nitrate (NO − 3 ), complete denitrification consumes substantial amounts of previously produced N 2 O by further reduction to N 2 (Baggs, 2008;Vieten et al, 2009). In environments that do not sustain stable anoxia, but undergo sporadic transitions between oxic and anoxic conditions, the activity of certain N 2 O reductases can be suppressed by transiently elevated O 2 concentrations and thus can lead to the accumulation of N 2 O (Morley et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Alteration of nitrous oxide emissions from floodplain soils by aggregate size, litter accumulation and plant–soil interactions

et al. 2018

View full text Add to dashboard Cite

Abstract. Semi-terrestrial soils such as floodplain soils are considered potential hot spots of nitrous oxide (N2O) emissions. Microhabitats in the soil – such as within and outside of aggregates, in the detritusphere, and/or in the rhizosphere – are considered to promote and preserve specific redox conditions. Yet our understanding of the relative effects of such microhabitats and their interactions on N2O production and consumption in soils is still incomplete. Therefore, we assessed the effect of aggregate size, buried leaf litter, and plant–soil interactions on the occurrence of enhanced N2O emissions under simulated flooding/drying conditions in a mesocosm experiment. We used two model soils with equivalent structure and texture, comprising macroaggregates (4000–250 µm) or microaggregates (<250 µm) from a N-rich floodplain soil. These model soils were planted with basket willow (Salix viminalis L.), mixed with leaf litter or left unamended. After 48 h of flooding, a period of enhanced N2O emissions occurred in all treatments. The unamended model soils with macroaggregates emitted significantly more N2O during this period than those with microaggregates. Litter addition modulated the temporal pattern of the N2O emission, leading to short-term peaks of high N2O fluxes at the beginning of the period of enhanced N2O emission. The presence of S. viminalis strongly suppressed the N2O emission from the macroaggregate model soil, masking any aggregate-size effect. Integration of the flux data with data on soil bulk density, moisture, redox potential and soil solution composition suggest that macroaggregates provided more favourable conditions for spatially coupled nitrification–denitrification, which are particularly conducive to net N2O production. The local increase in organic carbon in the detritusphere appears to first stimulate N2O emissions; but ultimately, respiration of the surplus organic matter shifts the system towards redox conditions where N2O reduction to N2 dominates. Similarly, the low emission rates in the planted soils can be best explained by root exudation of low-molecular-weight organic substances supporting complete denitrification in the anoxic zones, but also by the inhibition of denitrification in the zone, where rhizosphere aeration takes place. Together, our experiments highlight the importance of microhabitat formation in regulating oxygen (O2) content and the completeness of denitrification in soils during drying after saturation. Moreover, they will help to better predict the conditions under which hot spots, and “hot moments”, of enhanced N2O emissions are most likely to occur in hydrologically dynamic soil systems like floodplain soils.

show abstract

“…We assume that the gross N 2 O emission rate is linear over the duration of chamber closure, and diffusion of N 2 O from the chamber headspace into soil and its subsequent reduction follow Michaelis-Menten-type kinetics (Vieten et al, 2009), yielding the following time-…”

Section: Calculation Of Gross N 2 O Emission and Uptakementioning

confidence: 99%

Gross N2O fluxes across soil-atmosphere interface and stem N2O emissions from temperate forests

Wen¹

View full text Add to dashboard Cite

The difficulty of measuring gross N 2 O production and consumption in soil impedes our ability to predict N 2 O dynamics across the soil-atmosphere interface. Our study aimed to disentangle these processes by comparing measurements from gas-flow soil core (GFSC) and 15 N 2 O pool dilution ( 15 N 2 OPD) methods. GFSC directly measures soil N 2 O and N 2 fluxes, with their sum as the gross N 2 O production, whereas 15 N 2 OPD involves addition of 15 N 2 O into a chamber headspace and measuring its isotopic dilution over time. Measurements were conducted on intact soil cores from grassland, cropland, beech and pine forests. Across sites, gross N 2 O production and consumption measured by 15 N 2 OPD were only 10% and 6%, respectively, of those measured by GFSC. However, 15 N 2 OPD remains the only method that can be used under field conditions to measure atmospheric N 2 O uptake in soil. We propose to use different terminologies for the gross N 2 O fluxes that these two methods quantified. For 15 N 2 OPD, we suggest using 'gross N 2 O emission and uptake', which encompass gas exchange within the 15 N 2 O-labelled, soil air-filled pores. For GFSC, 'gross N 2 O production and consumption' can be used, which includes both N 2 O emitted into the soil air-filled pores and N 2 O directly consumed, forming N 2 , in soil anaerobic microsites.

show abstract

Respiration of nitrous oxide in suboxic soil

Cited by 10 publications

References 46 publications

A test of a field‐based ¹⁵N–nitrous oxide pool dilution technique to measure gross N₂O production in soil

A test of a field‐based ¹⁵N–nitrous oxide pool dilution technique to measure gross N₂O production in soil

Alteration of nitrous oxide emissions from floodplain soils by aggregate size, litter accumulation and plant–soil interactions

Gross N2O fluxes across soil-atmosphere interface and stem N2O emissions from temperate forests

Contact Info

Product

Resources

About

Respiration of nitrous oxide in suboxic soil

Cited by 10 publications

References 46 publications

A test of a field‐based 15N–nitrous oxide pool dilution technique to measure gross N2O production in soil

A test of a field‐based 15N–nitrous oxide pool dilution technique to measure gross N2O production in soil

Alteration of nitrous oxide emissions from floodplain soils by aggregate size, litter accumulation and plant–soil interactions

Gross N2O fluxes across soil-atmosphere interface and stem N2O emissions from temperate forests

Contact Info

Product

Resources

About

A test of a field‐based ¹⁵N–nitrous oxide pool dilution technique to measure gross N₂O production in soil

A test of a field‐based ¹⁵N–nitrous oxide pool dilution technique to measure gross N₂O production in soil