Glacier forefield soils can provide a substantial sink for atmospheric CH 4 , facilitated by aerobic methane-oxidizing bacteria (MOB). However, MOB activity, abundance, and community structure may be affected by soil age, MOB location in different forefield landforms, and temporal fluctuations in soil physical parameters. We assessed the spatial and temporal variability of atmospheric-CH 4 oxidation in an Alpine glacier forefield during the snow-free season of 2013. We quantified CH 4 flux in soils of increasing age and in different landforms (sandhill, terrace, and floodplain forms) by using soil gas profile and static flux chamber methods. To determine MOB abundance and community structure, we employed pmoA gene-based quantitative PCR and targeted amplicon sequencing. Uptake of CH 4 increased in magnitude and decreased in variability with increasing soil age. Sandhill soils exhibited CH 4 uptake rates ranging from -3.7 to -0.03 mg CH 4 m -2 day -1 . Floodplain and terrace soils exhibited lower uptake rates and even intermittent CH 4 emissions. Linear mixed-effects models indicated that soil age and landform were the dominating factors shaping CH 4 flux, followed by cumulative rainfall (weighted sum ≤4 days prior to sampling). Of 31 MOB operational taxonomic units retrieved, ~30% were potentially novel, and ~50% were affiliated with upland soil clusters gamma and alpha. The MOB community structures in floodplain and terrace soils were nearly identical but differed significantly from the highly variable sandhill soil communities. We concluded that soil age and landform modulate the soil CH 4 sink strength in glacier forefields and that recent rainfall affects its shortterm variability. This should be taken into account when including this environment in future CH 4 inventories.
- Atmospheric-methane oxidation
- Glacier forefield soil
- High-affinity MOB
- Methane flux
- Proglacial landforms