Multi-technique assessment of spatial and temporal variability of methane fluxes in a peat meadow

Both the chamber method and eddy covariance showed significant spatial variability, which was best explained by soil water level in combination with root depth patterns. Together, these variables probably determined the net methane production and the available mechanisms for methane transport to atmosphere. The methane fluxes showed strong temporal variability at different scales: diurnal cycles, significant day-to-day variability, and seasonal variations. Clear diurnal cycles of methane fluxes were observed synchronous to incoming radiation, latent heat and net ecosystem exchange, but not synchronous to temperature. This suggested that stomatal opening and/or pressurized convective throughflow were important mechanisms for gas transport through plants. The variability at the day-to-day scale was best explained by soil temperature below the water level combined with soil water level. Highest methane fluxes were observed during summer and lowest fluxes during autumn and winter. The vegetation density together with temperature and length of day-light probably determined this seasonality. Also, temporal variability varied spatially, probably due to the water table and root depth.