Format: ORAL

Annika Engroff1, Wanying Zhang1,2, Kathrin Rousk1

1 Center for Volatile Interactions (VOLT), Department of Biology, University of Copenhagen, Copenhagen Ø, 2100, Denmark 2 School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China

Cryptogams can be significant emitters of volatile organic compounds (VOCs). VOCs are highly reactive, can considerably affect atmospheric chemistry and lead to positive and negative climate feedback. Simultaneously, cryptogams associate with microbes, especially nitrogen (N)-fixing cyanobacteria. Cyanobacteria can contribute to N-budget of the plant host as well as of the ecosystem. Besides their contribution to the N cycle, these microbes could contribute substantially to VOC emissions measured from cryptogams. However, their contribution has not been assessed to date, and a potential link to N fixation, albeit plausible, is similarly unknown. In this study, VOC emission and N fixation rates of several cryptogamic species were measured. Four moss species (Hylocomium splendens, Sphagnum spp., Pleurozium schreberii, Polytrichum commune), three lichen species (Peltigera aphtosa, Nephrona arcticum, Cladonia spp.) and one liverwort species (Lophozia lycopodioides) from subarctic tundra were investigated before and after removal of associated microbes. Removal of associated microbes was done by surface sterilizing. VOC emissions were measured using real time PTR-ToF-MS and GC-MS. N fixation rates were measured using the acetylene reduction assay (ARA) as a measure of nitrogenase activity. Results revealed statistically significantly lower N fixation rates in washed compared to control condition in Hylocomium splendens and Polytrichum commune. Of all cryptograms in this study, N fixation rates were highest in the lichens Peltigera aphtosa and Nephrona arcticum and lowest in the liverwort Lophozia lycopodioides but without significant differences between control and washed condition. This lack of effect to surface sterilization on N fixation could be due to various reasons such as cyanobacteria residing safely within the plant cell or generally low colonization of some species. Preliminary data shows VOC emission rate and blend differences among cryptogam species as well as a positive link to N fixation rates.