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

Kim Yrjälä (1) , Tero Tuomivirta (2) , Heli Juottonen (3) , Anuliina Putkinen (2, 3) , Kaisa Lappi (3) , Eeva-Stiina Tuittila (4) , Timo Penttilä (2) , Kari Minkkinen (4) , Jukka Laine (5) , Krista Peltoniemi (2) , Hannu Fritze (2)

1 Department of Biosciences
2 Southern Unit
3 Department of Biosciences
4 Department of Forest Sciences [Helsinki]
5 Western Unit

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 characterized the dry end. The methane-oxidizing bacterial (MOB) community consisted exclusively of Methylocystis bacteria, but interestingly of five different alleles (T, S, R, M, and O) of the particulate methane monooxygenase marker gene pmoA. The M allele was dominant in the wet locations, and the occurrence of alleles O, S and T increased with drainage. The R allele that characterized the upper peat layer correlated with CH4 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.

Mots clés: Life Sciences

Kim Yrjälä, Tero Tuomivirta, Heli Juottonen, Anuliina Putkinen, Kaisa Lappi, et al.. CH4 production and oxidation processes in a boreal fen ecosystem after long-term water table drawdown. Global Change Biology, 2010, 17 (3), pp.1311. ⟨10.1111/j.1365-2486.2010.02290.x⟩. ⟨hal-00599524⟩