Soil moisture and activity of nitrite- and nitrous oxide-reducing microbes enhanced nitrous oxide emissions in fallow paddy soils
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Although cumulative N2O emissions are greater in the winter fallow season than in the rice-growing period, the mechanisms by which the emissions affect fallow paddy fields remain unclear. We aimed to identify N2O flux characteristics and illustrate how key nirS-, nirK- and nosZ-containing denitrifiers affect N2O emission levels in acidic fallow paddy soil. Five water-filled pore space (WFPS) levels were set at 25%, 50%, 75%, 100% and 125%, respectively. During the 48-h-long, high-flux incubation period, the N2O flux was the highest in soil samples with 75% WFPS, followed by those with 100% WFPS. The size of nirS-containing denitrifier community was more sensitive to the shifts in soil moisture and showed a stronger correlation with N2O flux than that of nirK-containing denitrifiers, whereas higher N2O concentrations induced an increase in the levels of nosZ-containing bacteria. After incubation for 48 h, nirK- and nosZ-denitrifying bacterial composition varied remarkably under 50%, 75%, and 100% WFPS treatments. However, the composition of nirS-containing denitrifying bacterial community gradually varied with an increase in soil moisture from 25% to 100% WFPS. Certain dominant OTUs of nirK- nirS- and nosZ-containing denitrifiers were highly abundant, especially under treatments of 50%, 75% and 100% WFPS, which were closely associated with the N2O flux. Thus, nirK, nirS and nosZ-containing denitrifiers respond to soil moisture differently, and enriched species might mainly be involved in controlling N2O flux in fallow paddy soils via denitrification, while the abundance of nirS-containing denitrifiers might affect N2O emission levels more significantly than that of nirK-containing denitrifiers.
KeywordsSoil moisture N2O emission Nitrite reductase N2O reductase Fallow paddy soil
PCA and correlation heatmap analyses were performed using the free Majorbio I-Sanger Cloud Platform (www.i-sanger.com). We would like to thank Editage [www.editage.cn] for providing English language editing services.
This research was financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB15020200), National Natural Science Foundation of China (41771335, 41771300), National Key Research and Development Program of China (2016YFD0200307, 2017YFD0202000), Open Fund of Key Laboratory of Agro-ecological Processes in Subtropical Region, Chinese Academy of Sciences (No. ISA2018203), and Hunan Provincial Natural Science Foundation of China (2016JJ3133).
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Conflict of interest
The authors declare that they have no conflict of interest.
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