Sarah Hagel Svendsen:
Arctic emissions of biogenic volatile organic compounds – from plants, litter and soils

Date: 29-09-2017    Supervisor: Riikka Rinnan & Anders Michelsen

Significant amounts of biogenic volatile organic compounds are emitted from terrestrial ecosystems. These emissions may influence the atmospheric chemistry and the climate. Climate warming will be most pronounced in the Arctic and this will likely have a large effect on the BVOC emissions from these areas. Despite this, BVOC emissions from arctic ecosystems are sparsely studied and measurements of high arctic soil and litter BVOC emissions are completely lacking. In this thesis, I have studied BVOC emissions from a high arctic soil moisture gradient, from decomposing shrub litter from high and low arctic heaths at increasing temperature and from high arctic active layer soils and permafrost soils during a thaw event and at increasing temperature.

Ecosystem BVOC emissions were measured in situ and BVOC emissions from soils and litter were measured from laboratory incubations. BVOCs were sampled in adsorbent cartridges and analyzed using gas chromatography–mass spectrometry.

Ecosystem BVOC emissions were highly dominated by terpenoids but the composition of terpenoids differed between different plant species. Litter emissions were less dominated by terpenoids than the ecosystem emissions, however they still constituted approximately 50 % of the total emissions. I suggested that the litter emissions derived both from microbial soil processes and from stores inside the litter tissue and that the relative importance of these two sources were plant species specific. Furthermore, emissions of non-terpenoid BVOCs were dominating the emission profile from the soils and the magnitude of the soil emissions depended greatly on the soil water content and temperature.

A warmer arctic climate will likely alter the composition of plant species, cause a thawing of permafrost soil and change soil characteristics such as the water content. Results presented in this thesis suggest that these changes will alter the both the composition of arctic BVOCs emitted and increase the emission magnitude.

This thesis contribute to reduce the large knowledge gap that exists about BVOC emissions in the Arctic from litter, soils and whole ecosystems and shows that BVOC emissions in the Arctic vary significantly. This may be highly important considering the large variations in the emissions reported in this thesis and can therefore help to improve our understanding of future BVOC emissions for the Arctic.