Saltmarsh wetlands were significant sources of N2O to the atmosphere; but the underlying mechanisms of N2O emissions from saltmarsh sediments remained elusive. Here, the integrated methodology was utilized to reveal the primary microbial pathways responsible for N2O emission in the Yangtze Estuary. The results indicated that heterotrophic denitrification (77.16–96.57 %) was the dominant pathway of N2O production, while NH2OH oxidation (1.10–6.78 %) and nitrifier denitrification (2.33–17.98 %) also had substantial contributions. The N2O consumption proportions ranged from 63.69 % to 90.98 %, and its values were quietly pronounced, suggesting that N2O emission contributed a small percentage of its gross production. The N2O emission rates of Phragmites australis and Spartina alterniflora were lower than those of Scirpus mariqueter and bare mudflat, and showed a decreasing trend along the intertidal elevation gradient, with the values fluctuating from 6.01 to 27.07 g m−2·y−1. Meanwhile, the N2O emission rates were lower at flood tide than ebb tide. The microbial genera capable of N2O metabolisms were annotated, such as Nitrosomonas and Bacillus, and nitrogen functional genes abundances were greatly positively correlated with nitrogen transformation rates, which significantly promoted N2O dynamics. The absolute abundances of nitrogen functional genes varied from 3.22 × 104 to 6.10 × 108 copies·g−1, and the potential rates of nitrification and dissimilatory nitrate reduction processes ranged from 5.07 to 236.96 nmolN2·g−1·d−1. The variations in redox condition and carbon/nitrogen substrate availability were the crucial environmental factors influencing N2O dynamics. Collectively, these findings could provide a valuable perspective on N2O emissions, and recommend the significance of N2O production and consumption in saltmarsh wetlands.
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