Light and dark conditions control the nitrous oxide uptake and emission dynamics in a subarctic, nutrient-poor permafrost peatland

Abstract As permafrost in the Arctic thaws due to global warming, emissions of nitrous oxide (N 2 O), a powerful greenhouse gas, may rise—yet its dynamics in permafrost peatlands remain poorly understood. Here we present 1,487 chamber measurements of N 2 O fluxes collected over three snow-free seasons in a subarctic thawing permafrost peatland. Measurements were taken under both light (with sunlight) and dark (without sunlight) conditions. Under light conditions, fluxes were mostly positive, indicating net emissions, and increased with plant activity and cooler soil temperatures. Under dark conditions, fluxes were consistently negative, indicating net uptake, and linked to soil moisture and green plant cover. The contrast between light and dark was clear and consistent. Overall, the ecosystem acted as a small but continuous N 2 O sink. Yet, localised areas showed strong N 2 O production potential. These results highlight the critical role of light and plant-soil interactions in regulating N 2 O fluxes, with implications for improving Arctic greenhouse gas budget estimates.