Wheat rhizodeposition stimulates soil nitrous oxide emission and denitrifiers harboring the nosZ clade I gene

Stimulatory effects of growing plants on nitrous oxide (N2O) emissions have been widely reported in terrestrial ecosystems, but the potential mechanisms responsible for these effects remain unclear. This study revealed that wheat can induce a 3.5–9.2-fold increase in N2O emissions under different soil fertility levels, and that this “plant” source of N2O occurs in the rhizosphere. Moreover, plants induced soil niche differentiation between denitrifiers harboring the nitrous oxide reductase genes nosZI and nosZII. Pulse labeling of wheat demonstrated that 67% of 13C-labeled nosZI-type denitrifiers, but no nosZII-type denitrifiers, were more abundant in the rhizosphere than in bulk soil. Furthermore, a higher percentage of bacterial genomes containing nitrite reductase genes was found within plant-associated nosZI-type denitrifiers than nosZII-type denitrifiers, favoring NO2− to N2O conversion. Overall, this study revealed a strong selective stimulating effect of wheat on soil denitrifiers through root-derived carbon and a key role of the nosZI-type community in rhizosphere denitrification.