Disproportionate CH₄ Sink Strength from an Endemic, Sub-Alpine Australian Soil Microbial Community

Soil-to-atmosphere methane (CH₄) fluxes are dependent on opposing microbial processes of production and consumption. Here we use a soil-vegetation gradient in an Australian sub-alpine ecosystem to examine links between composition of soil microbial communities, and the fluxes of greenhouse gases they regulate. For each soil/vegetation type (forest, grassland, and bog), we measured carbon dioxide (CO₂) and CH₄ fluxes and their production/consumption at 5 cm intervals to a depth of 30 cm. All soils were sources of CO₂, ranging from 49 to 93 mg CO₂ m^-2 h^-1. Forest soils were strong net sinks for CH₄, at rates of up to -413 µg CH₄ m^-2 h^-1. Grassland soils varied, with some soils acting as sources and some as sinks, but overall averaged -97 µg CH₄ m^-2 h^-1. Bog soils were net sources of CH₄ (+340 µg CH₄ m^-2 h^-1). Methanotrophs were dominated by USCα in forest and grassland soils, and Candidatus Methylomirabilis in the bog soils. Methylocystis were also detected at relatively low abundance in all soils. Our study suggests that there is a disproportionately large contribution of these ecosystems to the global soil CH₄ sink, which highlights our dependence on soil ecosystem services in remote locations driven by unique populations of soil microbes. It is paramount to explore and understand these remote, hard-to-reach ecosystems to better understand biogeochemical cycles that underpin global sustainability.