Soil microbial diversity, succession, and greenhouse gas cycling across a Greenlandic glacial chronosequence.

Accelerated glacial retreat in Greenland drives increased development of glacial outwash plains. These newly exposed landscapes provide an opportunity to study microbial dynamics during soil development. We explore soil microbial diversity, community assembly, and biogeochemical cycling across the Kiattuut Sermiat glacial chronosequence (southern Greenland) via 16S rRNA gene amplicon analysis paired with microbial abundance, soil physicochemical parameters, and gas flux data. Microbial diversity varied with soil depth, with more acidic topsoils abundant in Cyanobacteriota and Armatimonadota taxa. While aerobic lower soils likely contained relatively more anoxic pore spaces, hosting aerobic nitrifiers such as Nitrospirota, low-oxygen-associated Planctomycetota taxa, and less characterized Gemmatimonadota. Microbial diversity varied across the chronosequence following distance-decay principles, as communities were predominately dispersal limited and shaped by heterogeneous selection, with greater heterogeneous conditions further from the glacier terminus. Soil CO2 fluxes increased with distance from the glacier, following a shift from autotrophic sulfur- and iron-oxidizing taxa towards heterotrophic members. CH4 fluxes demonstrated greater uptake further from the glacier, and CH4-oxidation was associated with the methanotroph Methylocapsa. Considering the climatic relevancy of Greenlandic proglacial environments, we describe the largely unexplored microbial diversity and biogeochemical cycling of greenhouse gases in these developing soils.