Emissions of biogenic volatile organic compounds (BVOCs) from arctic ecosystems are scarcely studied and the effect of climate change on BVOC emissions even less so. BVOCs are emitted from all living organisms and play a role for atmospheric chemistry. The major part of BVOCs derives from plants, emitted in order to communicate within and between trophic levels and as protection against biotic and abiotic stresses, or as byproducts. Some BVOCs are very reactive, and when entering the atmosphere they rapidly react with for example hydroxyl radicals and ozone, affecting the oxidative capacity in the atmosphere. This may warm the climate due to a prolonged lifetime of the potent greenhouse gas methane in the atmosphere. However, oxidized BVOCs may participate in formation or growth of aerosols, which in turn may mitigate climate warming.
Climate change in the Arctic, an area characterized by short growing seasons, low temperatures and low statured plants, occurs at twice the speed of the global average. Changes in temperature and precipitation patterns have consequences for soil, plant species distribution, plant biomass and reproductive success. Emission and production of BVOCs are temperature dependent and the emissions will increase in a future warmer climate.
The aims of this dissertation were to study BVOC emission rates and blends from arctic ecosystems and to reveal the effect of climate change on BVOC emissions from the Arctic. BVOC emissions were measured in ambient and modified environmental conditions in the field. Sampling of BVOCs was done in situ using a push-pull enclosure technique and adsorbent cartridges which were analyzed using GC-MS. BVOC emissions have been measured in three different arctic/subarctic locations in numerous ecosystems during several growing seasons and whole diel cycles.
BVOC emissions were found to be emitted at all time points during a diel cycle in low- and subarctic ecosystems, highlighting that the night-time emissions from the Arctic should not be overlooked. This dissertation reports alarming responses in BVOC emission rates to rising temperatures. Three to four times higher emissions rates were found when temperature increased 1.2 and 4 °C in a fen and mesic tundra heath, respectively. The dark tundra surface temperature was on average 7.7 °C warmer over a growing season than the air temperature 1.5 meters above ground level, indicating that canopy surfaces temperatures should be used in BVOC models instead of air temperatures obtained from weather stations.
BVOC emissions will likely increase significantly in a future warmer climate due to the direct effect of temperature, but also due to the indirect effect of more plants biomass. Thus, arctic BVOC emissions will become more important for the global BVOC budget as well as for the regional climate due to the positive and negative climate warming feedbacks.