CH4 production and oxidation processes in a boreal fen ecosystem after long-term water table drawdown

Abstract

Mires, especially sedge dominated fens, are sources of the greenhouse gas CH4. Climate change scenarios predict a lowering water table (WT) in mires. To study the effect of WT drawdown on CH4 dynamics in a fen ecosystem, we took advantage of a WT drawdown gradient near a ground water extraction plant. Methane fluxes, CH4 production and oxidation potentials, were related to microbial communities responsible for the processes in four mire locations (wet, semi-wet, semi-dry and dry). Principal component analyses (PCA) performed on the vegetation, pH, CH4 and WT results clearly separated the four sampling locations in the gradient. Long-term lowering of WT was associated with decreased coverage of Sphagnum and aerenchymatic plants, decreased CH4 field emissions and CH4 production potential. Based on mcrA T-RF the methanogen community structure correlated best with the methane production and coverage of aerenchymatic plants along the gradient. Methanosarcinaceae and Methanocellales were found at the pristine wet end of the gradient, whereas the Fen cluster 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 oxidation potential. These results advance our understanding of mire dynamics after long-term WT drawdown and of the microbiological bases of methane emissions from mires.

Small spatial variability in methane emission measured from a wet patterned boreal bog

“…Methane-producing microbial activity may also increase as long as there are anoxic conditions and available substrates. However, in boreal climates warming is predicted to lower the WT, leading to thicker aerobic peat, which potentially creates a higher methane consumption rate layer (Yrjälä et al, 2011). Thus, changes in WT may compensate for the effect of rising temperature under a warmer climate.…”

“…Turetsky et al (2014) presented the mean methane flux of 15 bog sites as 96 ± 6 mg m −2 d −1 , which is a little higher than the mean fluxes in 2012 and 2014 (57 ± 6 and 77 ± 7 mg m −2 d −1 ) but lower than the mean flux in the warmest year 2013 (131 ± 12 mg m −2 d −1 ) in this study. Similarly, another review (Wilson et al, 2016) that included wintertime fluxes calculated lower mean methane flux for boreal nutrient-poor sites, 4100 mg m −2 yr −1 with 95 % CI from 50 to 24 600 mg m −2 yr −1 .…”

“…Although there is a wealth of studies that quantify methane emissions from different peatlands (reviewed by Turetsky et al, 2014;Wilson et al, 2016), most studies have been focused on fens that receive additional nutrients from the surrounding mineral soil and support a higher amount of aerenchymatous vegetation compared to bogs (Turetsky et al, 2014). Studies on the spatial variation in methane emissions in bogs with varying plant community types are scarce (see, however, Frenzel and Karofeld, 2000;Laine et al, 2007).…”

Dynamics of methane fluxes from two peat bogs in the Ore Mountains, Czech Republic

“…Fluxes were calculated using the linear portion of the gas concentration change over the 2-h time step (mean R 2 = 0.89). Rare ebullition events were deleted from the data (Yrjälä et al 2011). Water table level (WTL) and temperature of pore water from the surface was recorded (Figures 3b,d,f ).…”

Small spatial but large sporadic variability in methane emission measured from a patterned boreal bog

“…Methane producing microbial activity may also increase as long as there are anoxic conditions and available substrates. However, in boreal climate warming is predicted to lower WT leading to thicker aerobic peat, which enables a higher methane consumption rate layer (Yrjälä et al, 2011). Thus, changes in WT may compensate the effect of rising temperature under a warmer climate.…”