High Temporal and Spatial Variability of Atmospheric-Methane Oxidation in Alpine Glacier Forefield Soils

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• Soil Science

Background:

• Glacier forefield soils are young, developing ecosystems continuously exposed by glacial retreat.
• Aerobic methane-oxidizing bacteria (MOB) facilitate methane (CH₄) oxidation, a crucial process for atmospheric CH₄ removal.
• Understanding CH₄ oxidation in these dynamic environments is vital for accurate global CH₄ budgets.

Purpose of the Study:

• To assess the spatial and temporal variability of atmospheric CH₄ oxidation in an Alpine glacier forefield.
• To investigate the influence of soil age and landform on CH₄ flux and MOB communities.
• To determine factors controlling CH₄ uptake and emission in these nascent soils.

Main Methods:

• Quantified CH₄ flux using soil gas profiles and static flux chambers across varying soil ages and landforms (sandhill, terrace, floodplain).
• Analyzed MOB abundance and community structure via pmoA gene quantitative PCR and amplicon sequencing.
• Employed linear mixed-effects models to identify key drivers of CH₄ flux.

Main Results:

• CH₄ uptake increased with soil age and showed decreased variability in older soils.
• Sandhill soils exhibited significant CH₄ uptake, while floodplain and terrace soils showed lower rates or intermittent emissions.
• Soil age and landform were primary factors controlling CH₄ flux, with cumulative rainfall as a secondary influence.

Conclusions:

• Soil age and landform are critical determinants of CH₄ sink strength in glacier forefields.
• Recent rainfall influences short-term CH₄ flux variability.
• Findings are essential for incorporating glacier forefield soils into global CH₄ inventories.