Edge effects on N₂O, NO and CH₄ fluxes in two temperate forests

Forest ecosystems may act as sinks or sources of nitrogen (N) and carbon (C) compounds, such as the climate relevant trace gases nitrous oxide (N₂O), nitric oxide (NO) and methane (CH₄). Forest edges, which catch more atmospheric deposition, have become important features in European landscapes and elsewhere. Here, we implemented a fully automated measuring system, comprising static and dynamic measuring chambers determining N₂O, NO and CH₄ fluxes along an edge-to-interior transect in an oak (Q. robur) and a pine (P. nigra) forest in northern Belgium. Each forest was monitored during a 2-week measurement campaign with continuous measurements every 2h. NO emissions were 9-fold higher than N₂O emissions. The fluxes of NO and CH₄ differed between forest edge and interior, but not for N₂O. This edge effect was more pronounced in the oak than in the pine forest. In the oak forest, edges emitted less NO (on average 60%) and took up more CH₄ (on average 177%). This suggests that landscape structure can play a role in the atmospheric budgets of these climate relevant trace gases. Soil moisture variation between forest edge and interior was a key variable explaining the magnitude of NO and CH₄ fluxes in our measurement campaign. To better understand the environmental impact of N and C trace gas fluxes from forest edges, additional and long-term measurements in other forest edges are required.