Linkage between Arctic Tundra methane fluxes and microbial communities’ structure and function

Permafrost is the largest global pool of soil organic carbon (SOC) and it is almost ubiquitous in the Arctic regions. Among Arctic regions, Alaska suffered the highest warming in the last 40 years, causing permafrost degradation and release of greenhouse gasses (GHGs). Microbial communities are crucial in this process as their metabolic activities control the rates at which SOC is decomposed and GHGs are emitted. This study explores the microbial communities’ structure and function across three distinct types of arctic tundra (dry, tussock, and wet) in Arctic Alaska to better understand their role in the different CH4 fluxes observed. Soil cores were collected from each site over two consecutive years, 2023 and 2024. Amplicon sequencing for 16S rDNA and ITS was used to characterize the bacteria, archaea, and fungi communities in these samples. Results relative to CH4 fluxes showed that tussock tundra and wet tundra acted as CH4 sources, while dry heath tundra functioned as CH4 sink. Preliminary analysis using PCoA with Bray Curtis dissimilarity showed that in the first year of sampling, microbial and fungal communities differed significantly across tundra types and varied with sampling depth (p<0.001). Metabolic predictions of bacteria and archaea communities conducted with PICRUST 2.0 confirmed that methanogenic pathways were present only in the wet and tussock tundra, whereas methanotrophic pathways were common in the three different tundra types. Ecological prediction of fungal communities with FUNGuild revealed notable differences in the metabolism of SOC among the dry, tussock and wet tundra ecosystems.