Hotspots of soil N2O emission enhanced through water absorption by plant residue

Kravchenko, Alexandra; Toosi, Ehsan R.; Guber, Andrey; Ostrom, Nathaniel E.; Jin, Yu; Azeem, Kamran; Rivers, Mark L.; Robertson, G. Philip

doi:10.1038/ngeo2963

Cited by 154 publications

(123 citation statements)

References 60 publications

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“…Hence, we hypothesized that in the soils of high‐diversity systems, due to their higher amounts of POM and large pores, N 2 O‐BD also would be positively associated with POM and pore abundance. Yet, this hypothesis was not supported by the data and greater anoxic conditions, which could be surmised to occur within POM fragments due to enhanced decomposition (Kravchenko et al, ; Negassa et al, ), did not translate into greater N 2 O production via bacterial denitrification.…”

Section: Discussionmentioning

confidence: 82%

X‐ray computed tomography to predict soil N₂O production via bacterial denitrification and N₂O emission in contrasting bioenergy cropping systems

et al. 2018

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While renewable biofuels can reduce negative effects of fossil fuel energy consumption, the magnitude of their benefits depends on the magnitude of N2O emissions. High variability of N2O emissions overpowers efforts to curb uncertainties in estimating N2O fluxes from biofuel systems. In this study, we explored (a) N2O production via bacterial denitrification and (b) N2O emissions from soils under several contrasting bioenergy cropping systems, with specific focus on explaining N2O variations by accounting for soil pore characteristics. Intact soil samples were collected after 9 years of implementing five biofuel systems: continuous corn with and without winter cover crop, monoculture switchgrass, poplars, and early‐successional vegetation. After incubation, N2O emissions were measured and bacterial denitrification was determined based on the site‐preference method. Soil pore characteristics were quantified using X‐ray computed microtomography. Three bioenergy systems with low plant diversity, that is, corn and switchgrass systems, had low porosities, low organic carbon contents, and large volumes of poorly aerated soil. In these systems, greater volumes of poorly aerated soil were associated with greater bacterial denitrification, which in turn was associated with greater N2O emissions (R2 = 0.52, p < 0.05). However, the two systems with high plant diversity, that is, poplars and early‐successional vegetation, over the 9 years of implementation had developed higher porosities and organic carbon contents. In these systems, volumes of poorly aerated soil were positively associated with N2O emissions without a concomitant increase in bacterial denitrification. Our results suggest that changes in soil pore architecture generated by long‐term implementation of contrasting bioenergy systems may affect the pathways of N2O production, thus, change associations between N2O emissions and other soil properties. Plant diversity appears as one of the factors determining which microscale soil characteristics will influence the amounts of N2O emitted into the atmosphere and, thus, which can be used as effective empirical predictors.

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Section: Discussionmentioning

confidence: 82%

X‐ray computed tomography to predict soil N₂O production via bacterial denitrification and N₂O emission in contrasting bioenergy cropping systems

et al. 2018

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“…Kravchenko et al . () recently reported that increased water absorption by plant residue in the soil created favourable conditions for microbial denitrification and N 2 O hotspots that were much different than the bulk soil. Our study soils contained low organic carbon, likely limiting these production hotspots.…”

Section: Resultsmentioning

confidence: 99%

Ammonia‐oxidizing bacteria are the primary N₂O producers in an ammonia‐oxidizing archaea dominated alkaline agricultural soil

Meinhardt

Stopnišek

Pannu

et al. 2018

Environmental Microbiology

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Most agricultural N O emissions are a consequence of microbial transformations of nitrogen (N) fertilizer, and mitigating increases in N O emission will depend on identifying microbial sources and variables influencing their activities. Here, using controlled microcosm and field studies, we found that synthetic N addition in any tested amount stimulated the production of N O from ammonia-oxidizing bacteria (AOB), but not archaea (AOA), from a bioenergy crop soil. The activities of these two populations were differentiated by N treatments, with abundance and activity of AOB increasing as nitrate and N O production increased. Moreover, as N O production increased, the isotopic composition of N O was consistent with an AOB source. Relative N O contributions by both populations were quantified using selective inhibitors and varying N availability. Complementary field analyses confirmed a positive correlation between N O flux and AOB abundance with N application. Collectively, our data indicate that AOB are the major N O producers, even with low N addition, and that better-metered N application, complemented by selective inhibitors, could reduce projected N O emissions from agricultural soils.

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“…Regardless, the characterization of this less mobile domain along with observations of N 2 O production suggests that this less mobile porosity is likely contributing to the biogeochemical function of these lake SWIs, explaining the denitrification signals produced in bulk oxic pore waters. In addition to the physical porosity heterogeneity, buried POC has also been shown to result in localized anoxic zones and denitrification (e.g., Kravchenko et al, ), and enhanced microbial activity (Sobczak et al, ). Recognition that denitrification rates and residence times can be highly variable across small spatial scales (Harvey et al, ; Lansdown et al, ) further emphasizes the potential importance of microzone contribution to total flow path denitrification across freshwater SWIs, especially in studies focused on N cycling and N 2 O production.…”

Section: Resultsmentioning

confidence: 99%

Residence Time Controls on the Fate of Nitrogen in Flow‐Through Lakebed Sediments

et al. 2019

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For many glacial lakes with highly permeable sediments, water exchange rates control hydrologic residence times within the sediment‐water interface (SWI) and the removal of reactive compounds such as nitrate, a common pollutant in lakes and groundwater. Here we conducted a series of focused tracer injection experiments in the upper 20 cm of the naturally downwelling SWI in a flow‐through lake on Cape Cod, MA. We systematically varied residence time and reactant controls on nitrate processing, using isotopically labeled 15N nitrate to monitor the effect of these changes on nitrate removal via denitrification. The addition of acetate, a labile carbon compound, triggered the lake SWI to switch from net production to net removal of nitrate. When acetate was combined with increased residence time created by controlled reductions in water flux, we observed a fivefold increase in nitrate removal, a 26‐fold increase in N2 production, and a 42‐fold increase in N2O production. We demonstrate that water residence time is an important control on the fate of nitrate in these lake SWIs and illustrate that seasonal conditions that alter lake exchange rates and variability in lake carbon may predict dynamic nitrate removal across the SWI. Additionally, observed N2O production during the oxic pore water experiments paired with geophysical characterization of the sediment porosity revealed that the lake SWI has less mobile pores occupying upward of 50% of the total porosity volume, which function as reactive microzones for nitrate processing.

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Hotspots of soil N2O emission enhanced through water absorption by plant residue

Cited by 154 publications

References 60 publications

X‐ray computed tomography to predict soil N₂O production via bacterial denitrification and N₂O emission in contrasting bioenergy cropping systems

X‐ray computed tomography to predict soil N₂O production via bacterial denitrification and N₂O emission in contrasting bioenergy cropping systems

Ammonia‐oxidizing bacteria are the primary N₂O producers in an ammonia‐oxidizing archaea dominated alkaline agricultural soil

Residence Time Controls on the Fate of Nitrogen in Flow‐Through Lakebed Sediments

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Hotspots of soil N2O emission enhanced through water absorption by plant residue

Cited by 154 publications

References 60 publications

X‐ray computed tomography to predict soil N2O production via bacterial denitrification and N2O emission in contrasting bioenergy cropping systems

X‐ray computed tomography to predict soil N2O production via bacterial denitrification and N2O emission in contrasting bioenergy cropping systems

Ammonia‐oxidizing bacteria are the primary N2O producers in an ammonia‐oxidizing archaea dominated alkaline agricultural soil

Residence Time Controls on the Fate of Nitrogen in Flow‐Through Lakebed Sediments

Contact Info

Product

Resources

About

X‐ray computed tomography to predict soil N₂O production via bacterial denitrification and N₂O emission in contrasting bioenergy cropping systems

X‐ray computed tomography to predict soil N₂O production via bacterial denitrification and N₂O emission in contrasting bioenergy cropping systems

Ammonia‐oxidizing bacteria are the primary N₂O producers in an ammonia‐oxidizing archaea dominated alkaline agricultural soil