Fig. 1: Spatial and temporal N₂O emission fluxes and microbial production sources in the riparian zone and riverbed sediments along a transect of a riverine hyporheic zone at the site scale.

a N₂O emission flux over 4 years of monitoring (n = 48 independent experiments). For each box chart, the horizontal line indicates the median, the box represents the 25^th and 75^th percentiles, and the whisker shows the range from the 5^th to the 95^th percentile. b, c The microbial rate and contribution to N₂O production via NH₄⁺-derived and NO₃^--derived processes based on semi-in situ sediment-core incubation via the ¹⁵N tracing method (b) and slurry incubation involving the C₂H₂-inhibitor method (c) (n = 6 and n = 3 biologically independent samples for core and slurry incubation, respectively). Data were presented as mean values ± SEM; d Transcript abundance of N₂O-production related (amoA, norB, nirS, and nirK) and N₂O-reduction related (nosZ) genes (n = 3 biologically independent samples). Data were presented as mean values ± SEM. Here, amoA, ammonia monooxygenase gene encoded the NN pathway (NH₄⁺ → NH₂OH); nirSK, nitrite reductase genes (NO₂^- → NO) encoded the ND (nirK only), NCD and HD pathways; norB, nitric oxide reductase gene (NO → N₂O) encoded the ND, NCD and HD pathways; and nosZ, nitrous oxide reductase gene (N₂O → N₂) encoded the NCD and HD pathways. e Schematic representation of the sampling sites along a transect of a riverine hyporheic zone.