Tree tissues and species traits modulate the microbial methane-cycling communities of the tree phyllosphere

Background Methanogenic and methanotrophic communities (i.e., the microbial communities involved in methane production and consumption) of the tree phyllosphere remain uncharacterized for most tree species despite increasing evidence of their role in regulating tree methane fluxes. Using 16S rRNA gene sequencing, we studied the methanogenic and methanotrophic communities of leaves, wood and bark of five tree species ( Acer saccharinum , Fraxinus nigra , Ulmus americana , Salix nigra , and Populus tremuloides ) growing in the floodplain of Lake St-Pierre (Québec). Results Methanogenic and methanotrophic communities differed mostly between tree tissues (leaf, wood and bark) but also between tree species according to different traits (e.g., leaf, heartwood and bark pH, leaf and heartwood humidity). Methanogens were prevalent in the wood of trees, while facultative methanotrophs were found in higher proportions than methanogens in leaves and bark, suggesting different potential role of these microbial communities in methane regulation. Tree species differing in key traits could also be associated with differential microbial production/consumption of methane. Tissue pH was a particularly important trait in modulating methanogen-methanotroph community composition and the relative abundance of methanogens and methanotrophs in the different phyllosphere compartments. Conclusion Our study shows that methanogens and methanotrophs are prevalent in the phyllosphere of several tree species, suggesting a potential widespread role in the regulation of tree methane fluxes. Tree species traits are important in determining the composition and abundance of phyllosphere methane-cycling microbial communities. Better understanding these microbial communities and their drivers can help assess their potential contribution to methane mitigation strategies.