Microbial communities in standing dead trees in ghost forests are largely aerobic, saprophytic, and methanotrophic

Standing dead trees (snags) are recognized for their influence on methane (CH₄) cycling in coastal wetlands, yet the biogeochemical processes that control the magnitude and direction of fluxes across the snag-atmosphere interface are not fully elucidated. Herein, we analyzed microbial communities and fluxes at one height from ten snags in a ghost forest wetland. Snag-atmosphere CH₄ fluxes were highly variable (− 0.11–0.51 mg CH₄ m⁻² h⁻¹). CH₄ production was measured in three out of ten snags; whereas, CH₄ consumption was measured in two out of ten snags. Potential CH₄ production and oxidation in one core from each snag was assayed in vitro. A single core produced CH₄ under anoxic and oxic conditions, at measured rates of 0.7 and 0.6 ng CH₄ g⁻¹ h⁻¹, respectively. Four cores oxidized CH₄ under oxic conditions, with an average rate of − 1.13 ± 0.31 ng CH₄ g⁻¹ h⁻¹. Illumina sequencing of the V3/V4 region of the 16S rRNA gene sequence revealed diverse microbial communities and indicated oxidative decomposition of deadwood. Methanogens were present in 20% of the snags, with a mean relative abundance of