Edge effects on NO, NO and CH 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 (NO), nitric oxide (NO) and methane (CH). 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 NO, NO and CH 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 NO emissions. The fluxes of NO and CH differed between forest edge and interior, but not for NO. 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 CH (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 CH 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.