Methane dynamics in an alpine fen: a field-based study on methanogenic and methanotrophic microbial communities

Area of Science:

• Environmental Science
• Microbiology
• Geochemistry

Background:

• Wetlands are significant sources of atmospheric methane (CH4), a potent greenhouse gas.
• Understanding methane dynamics in wetland soils is crucial for climate change mitigation strategies.

Purpose of the Study:

• To investigate the in situ dynamics of methane (CH4) in permanently submerged soil of a Swiss alpine fen.
• To determine the vertical distribution and activity of methanogens and methanotrophs within the soil profile.
• To assess the influence of soil properties, root presence, and microbial activity on CH4 cycling.

Main Methods:

• High-resolution vertical sampling of soil cores down to 50 cm depth.
• Physico-chemical pore water analyses.
• Structural and microbiological analyses, including quantification of pmoA and mcrA transcripts.

Main Results:

• Methanogens and methanotrophs were active throughout the soil profile, with peak activity in the top 2 cm.
• Root surface area positively correlated with methanogen abundance (mcrA transcripts) and CH4 concentrations.
• Methane concentrations peaked at 10-15 cm depth, suggesting root exudates strongly influenced methanogenesis.

Conclusions:

• Root exudates from vascular plants significantly stimulate methanogenesis in alpine fen soils.
• Methane production driven by root activity plays a more dominant role in CH4 dynamics than methane oxidation stimulated by oxygen.
• Microbial communities involved in methane cycling exhibit depth-specific activity patterns influenced by soil conditions and plant presence.