Decoupling of soil reactive oxidized and reduced nitrogen gas emissions across a coastal wetland reclamation chronosequence

Soil reactive nitrogen (Nr) gas emissions significantly impact air quality and climate, yet the mechanisms regulating their co-emissions during coastal wetland reclamation remain poorly understood. Here, we investigated soil Nr dynamics across a 52-year coastal wetland reclamation chronosequence using integrated flux measurements, microbial analysis, and incubation experiments. We found soil ammonia (NH₃) emissions dominated and increased with reclamation chronosequence, while nitrous acid (HONO) and nitrogen oxides (NO_x) peaked at the mid-stage soils. Incubation results showed that elevated oxidized Nr emissions at mid-reclamation soils were insensitive to autotrophic nitrification inhibition and carbon substrate addition. Such soil emission patterns appeared to be linked to accumulated nitrite and altered iron redox conditions, potentially facilitating abiotic Nr production, alongside alternative nitrogen transformation pathways mediated by heterotrophic microbes. These findings indicate decoupling of soil reactive oxidized and reduced nitrogen gas emissions across coastal wetland reclamation chronosequence, offering insights into shifts in soil Nr emissions under anthropogenic wetland alteration.