Peaks of in situ N₂O emissions are influenced by N₂O‐producing and reducing microbial communities across arable soils

Abstract

Agriculture is the main source of terrestrial N 2 O emissions, a potent greenhouse gas and the main cause of ozone depletion. The reduction of N 2 O into N 2 by microorganisms carrying the nitrous oxide reductase gene (nosZ) is the only known biological process eliminating this greenhouse gas. Recent studies showed that a previously unknown clade of N 2 O-reducers (nosZII) was related to the potential capacity of the soil to act as a N 2 O sink. However, little is known about how this group responds to different agricultural practices. Here, we investigated how N 2 Oproducers and N 2 O-reducers were affected by agricultural practices across a range of cropping systems in order to evaluate the consequences for N 2 O emissions. The abundance of both ammonia-oxidizers and denitrifiers was quantified by real-time qPCR, and the diversity of nosZ clades was determined by 454 pyrosequencing.Denitrification and nitrification potential activities as well as in situ N 2 O emissions were also assessed. Overall, greatest differences in microbial activity, diversity, and abundance were observed between sites rather than between agricultural practices at each site. To better understand the contribution of abiotic and biotic factors to the in situ N 2 O emissions, we subdivided more than 59,000 field measurements into fractions from low to high rates. We found that the low N 2 O emission rates were mainly explained by variation in soil properties (up to 59%), while the high rates were explained by variation in abundance and diversity of microbial communities (up to 68%). Notably, the diversity of the nosZII clade but not of the nosZI clade was important to explain the variation of in situ N 2 O emissions. Altogether, these results lay the foundation for a better understanding of the response of N 2 O-reducing bacteria to agricultural practices and how it may ultimately affect N 2 O emissions.

Remotely sensed canopy nitrogen correlates with nitrous oxide emissions in a lowland tropical rainforest

“…After analysis of more than 59,000 N 2 O field measurements, Domeignoz‐Horta et al. () found that only high emissions rates were explained by variation in abundance and diversity of microbial communities, while rates of N 2 O emissions measured in this study fell at the low end of the observed range.…”

Arbuscular mycorrhizal fungi reduce nitrous oxide emissions from N2O hotspots

“…availability of O 2 , or carbon). (2018) (van Kessel et al, 2015) or N 2 O reduction (Sanford et al, 2012;Jones et al, 2014;Domeignoz-Horta et al, 2017). Domeignoz-Horta et al (2017) found that N 2 O hotspots were predominantly controlled by changes in the microbial communities, whereas lower N 2 O-producing areas were more likely to be controlled by variation in soil properties.…”

“…(2018) (van Kessel et al, 2015) or N 2 O reduction (Sanford et al, 2012;Jones et al, 2014;Domeignoz-Horta et al, 2017). Domeignoz-Horta et al (2017) found that N 2 O hotspots were predominantly controlled by changes in the microbial communities, whereas lower N 2 O-producing areas were more likely to be controlled by variation in soil properties. Using similar organic patches as in the present study, Nuccio et al (2013) found that while there was no overall change in bacterial diversity, the presence of AMF hyphae significantly modified the bacterial community.…”

“…Regardless of the process, the response to NH 4 + application in the AMF treatments suggests that there was either a reduction in N 2 O production, through reduced function or number of nitrifiers, or that nitrifier activity was masked by an increase in activity of N 2 O reducers, which can cause some soils to become N 2 O sinks (Domeignoz-Horta et al, 2017). It is also feasible that the presence of AMF hyphae modified the microbial community, shifting it away from N 2 O-producing nitrifiers or nitrifier denitrifiers, perhaps towards organisms capable of complete Fig.…”

Growth yield and selection of nosZ clade II types in a continuous enrichment culture of N2O respiring bacteria

“…The phylogeny of the nitrous oxide reductase (NosZ), encoded by the nosZ gene, has two major clades, clade I and II (Jones et al ., ). A high abundance and diversity of N 2 O reducing bacteria harboring nosZ clade II, in particular, has been linked to an increased N 2 O reduction potential in soils as well as lower in situ N 2 O emissions (Jones et al ., ; Domeignoz‐Horta et al ., ), but a mechanistic explanation for this is lacking. nosZ clade I and clade II differ in (i) the co‐occurrence with other denitrification genes, with nosZ clade II being more often associated to non‐denitrifiers (Graf et al ., ) and (ii) the accessory proteins associated to the nos operon.…”