Scale-dependent temporal variation in determining the methane balance of a temperate fen

Methane emissions from peatlands vary considerably over time which complicates the determination of methane balances. In this study, the relative magnitude of methane flux variation over different time scales (years, seasons, days) is evaluated using data from two years of manual chamber estimation. Closed-chamber estimations were conducted on three vegetation stands in a fen in northeastern Germany. During the first investigation year, emissions were considerably higher than during the second year. Clear seasonal patterns were only present during the first year. In both years emissions varied among vegetation stands. The parameters year and month together explained more than half of the variation in methane fluxes. In contrast, the parameter time of day was not significant in explaining variation in methane fluxes. The impact of methane emission patterns on the resulting balances decreases with a decreasing time scale. The results suggest that methane balances might be significantly biased if they rely on data from one or two years only. Consequently, if there is interest in whole balances, resources should be allocated primarily towards acquiring long-term data series. This might involve a reduction of measurement frequency to monthly or bimonthly methane flux determination.