Temperature dependence of greenhouse gas emissions from three hydromorphic soils at different groundwater levels

Wetlands contribute considerably to the global greenhouse gas (GHG) balance. In these ecosystems, groundwater level (GWL) and temperature, two factors likely to be altered by climate change, exert important control over CO₂, CH₄ and N₂O fluxes. However, little is known about the temperature sensitivity (Q₁₀) of the combined GHG emissions from hydromorphic soils and how this Q₁₀ varies with GWL. We performed a greenhouse experiment in which three different (plant‐free) hydromorphic soils from a temperate spruce forest were exposed to two GWLs (an intermediate GWL of ?20 cm and a high GWL of ?5 cm). Net CO₂, CH₄ and N₂O fluxes were measured continuously. Here, we discuss how these fluxes responded to synoptic temperature fluctuations. Across all soils and GWLs, CO₂ emissions responded similarly to temperature and Q₁₀ was close to 2. The Q₁₀ of the CH₄ and N₂O fluxes also was similar across soil types. GWL, on the other hand, significantly affected the Q₁₀ of both CH₄ and N₂O emissions. The Q₁₀ of the net CH₄ fluxes increased from about 1 at GWL = ?20 cm to 3 at GWL = ?5 cm. For the N₂O emissions, Q₁₀ varied around 2 for GWL = ?20 cm and around 4 for GWL = ?5 cm. This substantial GWL‐effect on the Q₁₀ of CH₄ and N₂O emissions was, however, hardly reflected in the Q₁₀ of the total GHG emissions (which varied around 2), because the contribution of these gases was relatively small compared to that of CO₂.