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 49-93 mg CO2 m-2 h-1. Forest soils were strong net sinks for CH4 at rates up to -413 microg CH4 m-2 h-1. Grassland soils varied with some soils acting as sources and some as sinks, but overall averaged -97 microg CH4 m-2 h-1. Bog soils were net sources of CH4 (+340 microg CH4 m-2 h-1). Methanotrophs were dominated by USCα in forest and grassland soils, and Candidatus Methylomirabilis sp. in the bog soils. Methylocystis were also detected at relatively low abundance. The potential disproportionately large contribution of these ecosystems to global CH4 oxidation, and poorly understood microbial community regulating it, highlight our dependence on soil ecosystem services in remote locations can be driven by a unique population of soil microbes.