Effects of elevated CO2 and O3 on N-cycling and N2O emissions: a short-term laboratory assessment

Abstract

Background and aims Elevated atmospheric CO 2 (eCO 2 ) and tropospheric O 3 (eO 3 ) can alter soil microbial processes, including those underlying N 2 O emissions, as an indirect result of changes in plant inputs. In this study, effects of eCO 2 and eO 3 on sources of N 2 O in a soybean (Glycine max (L.) Merr.) agroecosystem in Illinois (SoyFACE) were investigated. We hypothesized that increases in available C and anaerobic microhabitat under eCO 2 would stimulate N 2 O emissions, with a proportionally larger increase in denitrification derived N 2 O (N 2 O D ) compared to nitrification plus nitrifier denitrification derived N 2 O (N 2 O N+ND ). We expected opposite effects under eO 3 . Methods Isotopically labeled 15 NH 4 14 NO 3 and 14 NH 4 15 NO 3 were used to evaluate mineral N transformations, N 2 O D , and N 2 O N+ND in a 12-day incubation experiment. Results We observed minimal effects of eCO 2 and eO 3 on N 2 O emissions, movement of 15 N through mineral N pools, soil moisture content and C availability. Possibly, altered C and N inputs by eCO 2 and eO 3 were small relative to the high soil organic C content and N-inputs via biological N 2 -fixation, minimizing potential effects of eCO 2 and eO 3 on N-cycling. Conclusion We conclude that eCO 2 and eO 3 did not affect N 2 O emissions in the short term. However, it remains to be tested whether N 2 O emissions in SoyFACE will be unaltered by eCO 2 and eO 3 on a larger temporal scale under field conditions.

Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity

“…Ozone can also impair N cycling in soil driven by microbial activity (139,150,(153)(154)(155)(156)(157). For example, N fixation by legumes can decrease in response to increasing O 3 concentrations (158).…”

Warming-Induced Stimulation of Soil N2O Emissions Counteracted by Elevated CO2 from Nine-Year Agroecosystem Temperature and Free Air Carbon Dioxide Enrichment

“…The effects of elevated CO 2 and warming on N 2 O emission pathways in agricultural soils are rather complex and still elusive. − On the one hand, both elevated CO 2 and warming could stimulate N 2 O emissions by enhancing nitrification and denitrification via increased abundances of functional genes, including ammonia-oxidizing bacteria (AOB), amoA , and nirS . , On the other hand, both elevated CO 2 and warming could suppress N 2 O emissions by promoting N immobilization and subsequently decreasing substrates for nitrification and denitrification. , Elevated CO 2 also could reduce N 2 O emissions by increasing the ratio of N 2 to N 2 O during denitrification via reducing the value of ( nirK + nirS )/ nosZ . , Moreover, the nearly neutral effects of both elevated CO 2 and warming on N 2 O emissions have been reported, presumably due to the counteractions between favorable and unfavorable factors or the insufficient response of soil properties. ,,, For instance, an increase in soil C availability under elevated CO 2 may depress nitrification and associated N 2 O emissions by increasing ammonium (NH 4 + ) immobilization while stimulating denitrification and associated N 2 O emissions, which probably accounted for the unaltered N 2 O emissions under elevated CO 2 …”

Ground-level ozone in the Mekong Delta region: precursors, meteorological factors, and regional transport

“…Symptoms of injury can be observed through leaf wilt or necrosis on the leaf surface, which can coalesce to form larger areas of injury; the leaves often dry up and fall prematurely (Emberson et al, 2009). Ozone reduces grain size, weight, nutritional quality in eld crops such as certain varieties of wheat, rice, maize, beans, and soybeans (Biswas et al, 2008;Decock et al, 2012) Asian rice (Oryza sativa) is an important food crop, supplying more than half of the world's population, particularly in Asia and Africa (Doliente et al, 2021). The impact of ground-level ozone on local rice varieties in Asia may be of greater interest, given the important role played by agriculture in this region (Chen et al, 2008).…”