Activity and Abundance of Nitrous Oxide Reducing Bacteria in Platismatia glauca : An Epiphytic Lichen in the Boreal Spruce Forest

ABSTRACT The nitrous oxide (N 2 O) dynamics in boreal forests are better known at the ecosystem scale, with greater uncertainty associated with specific ecosystem compartments. We investigated the N 2 O dynamics of the lichen Platismatia glauca in boreal forests near Kuopio, North Savo, Finland. At the study sites, P. glauca is the most abundant lichen colonising Norway spruce ( Picea abies ) . Despite their abundance, the contribution of epiphytic lichens like P. glauca to N 2 O dynamics in boreal forests has received little attention. By incubating P. glauca , we assessed the effects of moisture, temperature, and oxygen availability on its N 2 O dynamics. We observed net N 2 O consumption potential, particularly at +5°C at aerobic condition. Quantitative real‐time PCR analysis targeting the N 2 O reductase gene fragment ( nosZ ) revealed that it was present and active in both in situ and incubated lichens. nosZ transcription was higher at +5°C. Clade I nosZ was dominant, with most sequences affiliated with the order Rhizobiales. We confirmed the presence of nosZ gene with targeted metagenomics sequencing. Our results demonstrate that P. glauca acts as a net consumer of N 2 O, with potential ranging between 0.1 and 0.4 ng N 2 O–N g DW −1 h −1 under aerobic conditions.