Methane consumption by proteobacterial methanotrophs in boreal spruce phyllosphere activated with methane

Current knowledge on methane (CH₄) sinks is limited to chemical processes in the atmosphere, and to methanotrophy in forest soils and peatlands. Recent discoveries have indicated that also tree branches, i.e. phyllosphere, may consume atmospheric CH₄, thus functioning as a novel CH₄ sink. However,  the process is not yet confirmed and the mechanism not resolved.

Here, we confirm that leaves and needles of boreal trees have the capacity to consume CH₄ with stable isotope enrichment studies in field and laboratory experiments, and that the consumption is a biological process. With molecular analyses, we confirmed that the activity of needle-associated proteobacterial methanotrophs increased sporadically under CH₄ and acetate enrichment. Our results indicate that CH₄ consumption can exist in the tree canopy, which is characterized by interspecies variation, spatial patchiness and small but significant microbial activity.

This is a novel symbiotic connection between microbes and plant cells, which can enhance overall carbon sequestration in the boreal forests.