Dynamics of N2O emissions from Amazonian tropical peat forest and partitioning N-processes using 15N isotopes.

Tropical peatlands are crucial for global nitrogen (N) cycling because they store large amounts of carbon and N. This study, conducted in November 2023, investigated the dynamics of N₂O emissions from Amazonian peatland forests in Peru. It focused specifically on two peatland forest sites in Iquitos: the Quistococha and Zungarococha forests. We conducted static chamber gas measurements to assess soil greenhouse gas (GHG) fluxes. Additionally, we took soil samples for physical and chemical properties and soil microbiome (DNA & RNA). In order to investigate the source processes for N₂O production and consumption, we applied ¹⁵N isotopes as tracers in soil. We also took samples for natural abundance of ¹⁵N in N₂O gas. Our results indicate that both forests exhibited different trends in soil GHG fluxes and N substrates. Quistococha had higher levels of soil nitrate and ammonium compared to Zungarococha, which correlated with increased N₂O emissions from Quistococha. A similar pattern was observed for CO₂ emissions, with Quistococha producing higher levels than Zungarococha. Contrastingly, Zungarococha had higher soil moisture levels, which aligned with its lower N₂O emissions. This forest also showed greater soil N₂ emissions, suggesting the potential for complete denitrification. However, this site was also a significant source of CH₄ emissions due to its higher soil moisture, which supports methanogenic activity. Overall, the two sites demonstrated distinct behaviors: Quistococha was a source of N₂O and CO₂, influenced by intermediate soil moisture. Zungarococha emitted higher levels of CH₄ and N₂ due to its high soil moisture conditions. The patterns in N₂O fluxes are further supported by ¹⁵N isotopic mapping, correlating N₂O emissions with their source processes. The site preference values fall within the denitrification zone at Zungarococha and the nitrification zone, with some hybrid processes in Quistococha.  The microbiome analyses show similar results, with denitrifying microbes dominating the Zungarococha soil and nitrifying microbes dominating the Quistococha soil.