Fire-driven shifts in nitrous oxide emissions in boreal peatland soils

In parts of the northern boreal zone, a significant number of peatlands have previously been drained for forestry. Climate change is increasing the frequency of forest fires, making these peatland forests particularly vulnerable to wildfires due to thick organic layers and low water table levels. Peatlands store approximately 10% of global soil nitrogen (N) and peatland forests in particular may act as a source of nitrous oxide (N2O), which is a potent greenhouse gas contributing to ozone depletion. Although forest fires affect several factors influencing soil N dynamics, very little is known about the impact of wildfires on the N cycle and N2O emissions on burned peatland sites. We investigated these impacts with a peat column experiment by simulating forest fire conditions with controlled burning. 

We collected peat profiles up to 50 cm depth from three different undrained and drained peatland sites in Southern Finland in May 2025 (n=50). Peat columns were incubated outdoors for three months, and half of the columns were scorched in mid-summer with a gas torch to simulate a surface fire. During the experiment period, N2O, carbon dioxide (CO2), and methane (CH4) were measured weekly. After three months, incubated columns were dissected, and peat samples were collected to analyze soil physicochemical parameters, microbial community structure, and the quality of soil organic matter.  

Preliminary results suggest that nutrient-rich peatland forests act as N2O sources under favorable conditions for N2O production, while nutrient-poor sites are negligible as N2O sources. The fire appeared to shift these patterns and temporarily increase N2O emissions across peatland types. Further analyses will evaluate how post-fire changes in different peat N pools relate to observed N₂O flux dynamics.