The study examined microorganisms living in the bark of eight common tree species in various Australian habitats and their influence on climate-active gas fluxes.[2][5] The bark has been found to host up to approximately 6 trillion microbial cells per square meter, and these communities are distinct from the surrounding soil and water microbiota.[2][4] Metagenomic analyzes have shown that these are mainly metabolically "flexible" bacteria that can cycle gases such as methane (CH₄), hydrogen (H₂) and carbon monoxide (CO).[2][4] Laboratory experiments have shown that in the presence of oxygen, microbes consume these gases, while in an oxygen-free environment they can produce them.[2][4] Measurements directly on trees have shown that there are significant fluxes of several climate-active gases at the bark surface, and that net uptake of hydrogen occurs across all species and bark heights examined.[2] The authors estimate that microbes in the crust can annually remove hydrogen from the atmosphere in the order of teragrams.[2] The study concludes that the bark microbiota significantly modulates the fluxes of the main climate-active gases (CH₄, H₂, CO and volatile organic compounds) and thus contributes to the climate benefits of trees.[2][5]