Emissions of biogenic volatile organic compounds from arctic shrub litter are coupled with changes in the bacterial community composition

Emissions of biogenic volatile organic compounds (BVOCs) from natural ecosystems impact atmospheric chemistry as well as biological interactions and even soil biogeochemical processes. Plant litter emits substantial amounts of BVOCs. These emissions may contribute to total ecosystem emissions especially in the Arctic where the living plant biomass is low and the amount of litter is expected to increase as the deciduous shrubs expand in response to a warmer climate. Here, we incubated in the laboratory litter from the evergreen Cassiope tetragona and deciduous Salix spp. from a high arctic and a low arctic location. The 8-week-long incubation was conducted with temperature increasing from 5 °C to 26 °C, mimicking the transition from winter to summer. BVOC emissions from the decomposing litter were sampled weekly in adsorbent cartridges and analyzed using gas chromatography-mass spectrometry, and the bacterial community composition was investigated by sequencing of PCR amplified 16S rRNA gene fragments. Our results showed that litter from C. tetragona, which is a terpenoid storing species, had higher BVOC emission rates (mainly terpenoids) than the Salix litter, which does not have specialized BVOC storing compartments. The C. tetragona litter emissions were higher in the high arctic than the low arctic samples. The emission rates from the C. tetragona litter increased during the incubation period, whereas emission rates from the Salix litter decreased, suggesting that the emissions originated from different sources and/or processes. The bacterial community composition in the Salix litter, but not in the C. tetragona litter, changed in parallel with the changes in the BVOC emissions during the incubation period. Therefore, we suggest that bacteria may be more important for the BVOC emissions from decomposing Salix litter than C. tetragona litter.