Periodic Reporting for period 4 - TUVOLU (Tundra biogenic volatile emissions in the 21st century)
Reporting period: 2022-10-01 to 2024-03-31
Biogenic volatile organic compounds (BVOCs) influence atmospheric oxidation causing climate feedback thought to be especially significant in remote areas with low anthropogenic emissions, such as the Arctic. Still, we do not understand the dynamics and impact of climatic and biotic BVOC emission drivers in arctic and alpine tundra, which are highly temperature-sensitive BVOC sources. This ERC consolidator project aimed to redefine tundra BVOC emission estimates to account for rapid and dramatic climate warming accompanied by effects of vegetation change, permafrost thaw, insect outbreaks and herbivory. We quantified the relationships between leaf and canopy temperatures and BVOC emissions to improve BVOC emission model predictions of emission rates in low-statured tundra vegetation, which efficiently heats up under clear skies. We experimentally determined the contributions of induced BVOC emissions from insect herbivory in the warming Arctic by field manipulation experiments addressing basal herbivory and insect outbreaks and laboratory experiments. We used laboratory experiments to determine if permafrost thaw leads to significant BVOC emissions from thawing and newly available soil processes, or if the released BVOCs are largely taken up by soil microbes. We also used a global network of existing climate warming experiments in alpine tundra to assess how the BVOC emissions from tundra vegetation world-wide respond to climate change. Measurement data will help develop and parameterize BVOC emission models to produce holistic enhanced predictions for global tundra emissions. We used modelling to estimate emission impacts on tropospheric ozone concentrations and secondary organic aerosol levels, producing the first assessment of arctic BVOC-mediated feedbacks on regional air quality and climate.
In WP1, focused on canopy surface temperature impacts, we conducted field work in Abisko, Sweden, Narsarsuaq, Greenland, and Finse, Norway. Leaf-level studies on tundra shrubs revealed that evergreen and deciduous species differ in temperature responses for photosynthesis and BVOC emissions (Simin et al. 2021, Environ. Exp. Bot.). Plant-scale measurements on dwarf birch and grey willow across an elevation gradient assessed relationships between canopy height, plant and environmental traits, and BVOC emissions (Simin et al. 2022, Sci. Total Environ.). Ecosystem-scale measurements showed that a palsa area emitted more BVOCs than a wet fen, while a lake acted as a BVOC sink (Seco et al. 2020, Atmos. Chem. Phys.; Seco et al. 2022, PNAS). Tundra BVOC emissions' strong temperature dependency was evident at the ecosystem scale (Seco et al. 2020, Atmos. Chem. Phys.; Seco et al. 2022, PNAS).
In WP2, focused on insect herbivory, field work was conducted in Abisko, Tromsø, and Narsarsuaq. An experiment using methyl jasmonate (MeJA) to mimic insect herbivory on dwarf birch showed increased BVOC emissions and altered compound profiles, with climate warming amplifying this response (Li et al. 2019, Nat. Plants). The effects of herbivory on dwarf birch BVOC emissions varied under different environments (Rieksta et al. 2021, Glob. Change Biol.; Rieksta et al. 2023, Plant Environ. Interact.). Experiments indicated a positive relationship between the number of feeding larvae and BVOC emissions from mountain birch (Rieksta et al. 2020, Front. Plant Sci.). Gall-infestation caused less changes in BVOC emissions from Arctic willows (Swanson et al. 2021, Sci. Total Environ.).
In WP3, focused on permafrost thaw emissions, we showed that thawing permafrost releases BVOCs, especially ethanol and methanol, with lower atmospheric emissions due to microbial uptake during passage through the active layer (Kramshøj et al. 2018, Nat. Commun.). Microbial uptake is efficient for all BVOCs in all soils (Albers et al. 2018, Biogeosciences; Rinnan & Albers 2020, JGR Biogeosci.). The uptake rate increases with higher BVOC availability (Jiao et al. 2023, Soil Biol. Biochem.). Soil water content, affecting oxygen levels, also influences BVOC emissions (Kramshøj et al. 2019, Glob. Change Biol.). Emissions vary over the growing season and between landscape types (Jiao et al. 2023, Geoderma).
WP4 assessed temperature sensitivity of BVOC emissions in Alpine ecosystems beyond the Arctic, with field measurements in Ecuador, Bolivia, and Costa Rica. Comparisons of BVOC emissions in control and warming treatments in local Alpine vegetation are under analysis (Chan et al., in preparation; Smart et al., in preparation).
WP5’s modelling work analyzed Pan-Arctic tundra BVOC emissions under different climate scenarios and their impacts on atmospheric chemistry (Tang et al. 2023, npj Clim. Atmos. Sci.). A review article summarized current knowledge and identified gaps in modelling soil BVOC processes (Tang et al. 2019, Rev. Geophys.). New leaf temperature algorithms were developed using data from WP1 (Simin et al. 2021, Environ. Exp. Bot.) and ecosystem data were used for model validation (Seco et al. 2020, Atmos. Chem. Phys.). Herbivory-BVOC emission relationships were assessed to develop algorithms for model improvement (Tang et al., in preparation).
In WP2, focused on insect herbivory, field work was conducted in Abisko, Tromsø, and Narsarsuaq. An experiment using methyl jasmonate (MeJA) to mimic insect herbivory on dwarf birch showed increased BVOC emissions and altered compound profiles, with climate warming amplifying this response (Li et al. 2019, Nat. Plants). The effects of herbivory on dwarf birch BVOC emissions varied under different environments (Rieksta et al. 2021, Glob. Change Biol.; Rieksta et al. 2023, Plant Environ. Interact.). Experiments indicated a positive relationship between the number of feeding larvae and BVOC emissions from mountain birch (Rieksta et al. 2020, Front. Plant Sci.). Gall-infestation caused less changes in BVOC emissions from Arctic willows (Swanson et al. 2021, Sci. Total Environ.).
In WP3, focused on permafrost thaw emissions, we showed that thawing permafrost releases BVOCs, especially ethanol and methanol, with lower atmospheric emissions due to microbial uptake during passage through the active layer (Kramshøj et al. 2018, Nat. Commun.). Microbial uptake is efficient for all BVOCs in all soils (Albers et al. 2018, Biogeosciences; Rinnan & Albers 2020, JGR Biogeosci.). The uptake rate increases with higher BVOC availability (Jiao et al. 2023, Soil Biol. Biochem.). Soil water content, affecting oxygen levels, also influences BVOC emissions (Kramshøj et al. 2019, Glob. Change Biol.). Emissions vary over the growing season and between landscape types (Jiao et al. 2023, Geoderma).
WP4 assessed temperature sensitivity of BVOC emissions in Alpine ecosystems beyond the Arctic, with field measurements in Ecuador, Bolivia, and Costa Rica. Comparisons of BVOC emissions in control and warming treatments in local Alpine vegetation are under analysis (Chan et al., in preparation; Smart et al., in preparation).
WP5’s modelling work analyzed Pan-Arctic tundra BVOC emissions under different climate scenarios and their impacts on atmospheric chemistry (Tang et al. 2023, npj Clim. Atmos. Sci.). A review article summarized current knowledge and identified gaps in modelling soil BVOC processes (Tang et al. 2019, Rev. Geophys.). New leaf temperature algorithms were developed using data from WP1 (Simin et al. 2021, Environ. Exp. Bot.) and ecosystem data were used for model validation (Seco et al. 2020, Atmos. Chem. Phys.). Herbivory-BVOC emission relationships were assessed to develop algorithms for model improvement (Tang et al., in preparation).
We collected the first growing season-long BVOC exchange time series in Arctic tundra using eddy covariance (EC) and real-time measurement of hundreds of compounds. These datasets reveal seasonal variations and confirm the high temperature dependency of BVOC emissions from tundra vegetation, previously suggested by small-scale data. Coupled with remote sensing of vegetation greenness and surface temperature, this provides strong tools to assess BVOC exchange factors and understand tundra shrub responses to warming (Seco et al. 2022, PNAS).
Our pioneering work on BVOC emissions from permafrost thaw has led several process studies revealing that actual emissions depend on the balance between release and microbial uptake, influenced by environmental conditions (Kramshøj et al. 2018, Nat. Commun.; Rinnan & Albers 2020, JGR Biogeosci.; Kramshøj et al. 2019, Glob. Change Biol.). The work related to soil processes in ecosystem BVOC exchange is still at its infancy and will likely lead to important new understanding in the future.
We also highlighted insect herbivory's importance in affecting Arctic BVOC emissions. While rising temperatures strongly influence emissions, herbivory has even more drastic effects during active feeding periods, amplified by temperature (Li et al. 2019, Nat. Plants).
Overall, we improved BVOC emission models, enhancing estimates of their magnitudes and compositions under different climate scenarios and their impact on atmospheric composition and climate (Tang et al. 2023, npj Clim. Atmos. Sci.).
Our pioneering work on BVOC emissions from permafrost thaw has led several process studies revealing that actual emissions depend on the balance between release and microbial uptake, influenced by environmental conditions (Kramshøj et al. 2018, Nat. Commun.; Rinnan & Albers 2020, JGR Biogeosci.; Kramshøj et al. 2019, Glob. Change Biol.). The work related to soil processes in ecosystem BVOC exchange is still at its infancy and will likely lead to important new understanding in the future.
We also highlighted insect herbivory's importance in affecting Arctic BVOC emissions. While rising temperatures strongly influence emissions, herbivory has even more drastic effects during active feeding periods, amplified by temperature (Li et al. 2019, Nat. Plants).
Overall, we improved BVOC emission models, enhancing estimates of their magnitudes and compositions under different climate scenarios and their impact on atmospheric composition and climate (Tang et al. 2023, npj Clim. Atmos. Sci.).