Spatiotemporal variation of net methane emissions and its causes across an ombrotrophic peatland : a site study from Southern Sweden

Sammanfattning: Methane emissions from natural wetlands are an important contributor to methane levels in the atmosphere. These emissions are highly variable in time and space, even within sites. Further understanding of this variation is vital to successfully model the overall methane emissions from wetlands. This study investigates spatial variation through measurements of 22 plots across Fäjemyr bog. Manual measurements were taken in 16 plots across four sites at the bog during five days throughout November 2012. In addition 6 automatic chambers were used that measures emissions once every hour throughout the year. The emissions from these 6 automatic chambers were also used for assessing the temporal variation during the year 2012. The spatial variation was found to depend upon microtopography more than site location. Plot-specific variation was also found, which suggests that other variables also affect spatial variation. The temporal variation was generally best explained by temperature at soil depths of 20 and 50 cm, especially if daily averages were used. The importance of temporal scale became evident when correlations between net methane emissions and environmental variables changed depending on the time investigated. Yearly, seasonal and shorter timescales revealed different responses which were thought to depend on the seasonality of light and plant phenology at Fäjemyr in addition to the measured variables. Shorter timescales could be used to increase the process understanding of Fäjemyr. In addition, the study also reveals that the automatic chamber system poorly represents the methane emissions from hollows across the bog as emissions were lower than those measured in the manual plots. Emissions from lawns and hummocks seem to be better represented.