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Separating direct and indirect effects of rising temperatures on biogenic volatile emissions in the Arctic.

ABSTRACT: Volatile organic compounds (VOCs) are released from biogenic sources in a temperature-dependent manner. Consequently, Arctic ecosystems are expected to greatly increase their VOC emissions with ongoing climate warming, which is proceeding at twice the rate of global temperature rise. Here, we show that ongoing warming has strong, increasing effects on Arctic VOC emissions. Using a combination of statistical modeling on data from several warming experiments in the Arctic tundra and dynamic ecosystem modeling, we separate the impacts of temperature and soil moisture into direct effects and indirect effects through vegetation composition and biomass alterations. The indirect effects of warming on VOC emissions were significant but smaller than the direct effects, during the 14-y model simulation period. Furthermore, vegetation changes also cause shifts in the chemical speciation of emissions. Both direct and indirect effects result in large geographic differences in VOC emission responses in the warming Arctic, depending on the local vegetation cover and the climate dynamics. Our results outline complex links between local climate, vegetation, and ecosystem-atmosphere interactions, with likely local-to-regional impacts on the atmospheric composition.

SUBMITTER: Rinnan R

PROVIDER: S-EPMC7768730 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Separating direct and indirect effects of rising temperatures on biogenic volatile emissions in the Arctic.

Rinnan Riikka R Iversen Lars L LL Tang Jing J Vedel-Petersen Ida I Schollert Michelle M Schurgers Guy G

Proceedings of the National Academy of Sciences of the United States of America 20201130 51

Volatile organic compounds (VOCs) are released from biogenic sources in a temperature-dependent manner. Consequently, Arctic ecosystems are expected to greatly increase their VOC emissions with ongoing climate warming, which is proceeding at twice the rate of global temperature rise. Here, we show that ongoing warming has strong, increasing effects on Arctic VOC emissions. Using a combination of statistical modeling on data from several warming experiments in the Arctic tundra and dynamic ecosys ...[more]

PMID: 33257556

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Project description:Rapid Arctic warming, a lengthening growing season, and the increasing abundance of biogenic volatile-organic-compound-emitting shrubs are all anticipated to increase atmospheric biogenic volatile organic compounds (BVOCs) in the Arctic atmosphere, with implications for atmospheric oxidation processes and climate feedbacks. Quantifying these changes requires an accurate understanding of the underlying processes driving BVOC emissions in the Arctic. While boreal ecosystems have been widely studied, little attention has been paid to Arctic tundra environments. Here, we report terpenoid (isoprene, monoterpenes, and sesquiterpenes) ambient mixing ratios and emission rates from key dominant vegetation species at Toolik Field Station (TFS; 68°38' N, 149°36' W) in northern Alaska during two back-to-back field campaigns (summers of 2018 and 2019) covering the entire growing season. Isoprene ambient mixing ratios observed at TFS fell within the range of values reported in the Eurasian taiga (0-500 parts per trillion by volume - pptv), while monoterpene and sesquiterpene ambient mixing ratios were respectively close to and below the instrumental quantification limit (~ 2 pptv). Isoprene surface emission rates ranged from 0.2 to 2250 μgC m-2 h-1 (mean of 85 μgC m-2 h-1) and monoterpene emission rates remained, on average, below 1 μgC m-2 h-1 over the course of the study. We further quantified the temperature dependence of isoprene emissions from local vegetation, including Salix spp. (a known isoprene emitter), and compared the results to predictions from the Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1). Our observations suggest a 180 %-215 % emission increase in response to a 3-4°C warming, and the MEGAN2.1 temperature algorithm exhibits a close fit with observations for enclosure temperatures in the 0-30°C range. The data presented here provide a baseline for investigating future changes in the BVOC emission potential of the under-studied Arctic tundra environment.

Project description:Emissions of biogenic volatile organic compounds (BVOCs) have been earlier shown to be highly temperature sensitive in subarctic ecosystems. As these ecosystems experience rapidly advancing pronounced climate warming, we aimed to investigate how warming affects the BVOC emissions in the long term (up to 13 treatment years). We also aimed to assess whether the increased litterfall resulting from the vegetation changes in the warming subarctic would affect the emissions. The study was conducted in a field experiment with factorial open-top chamber warming and annual litter addition treatments on subarctic heath in Abisko, northern Sweden. After 11 and 13 treatment years, BVOCs were sampled from plant communities in the experimental plots using a push-pull enclosure technique and collection into adsorbent cartridges during the growing season and analyzed with gas chromatography-mass spectrometry. Plant species coverage in the plots was analyzed by the point intercept method. Warming by 2 °C caused a 2-fold increase in monoterpene and 5-fold increase in sesquiterpene emissions, averaged over all measurements. When the momentary effect of temperature was diminished by standardization of emissions to a fixed temperature, warming still had a significant effect suggesting that emissions were also indirectly increased. This indirect increase appeared to result from increased plant coverage and changes in vegetation composition. The litter addition treatment also caused significant increases in the emission rates of some BVOC groups, especially when combined with warming. The combined treatment had both the largest vegetation changes and the highest BVOC emissions. The increased emissions under litter addition were probably a result of a changed vegetation composition due to alleviated nutrient limitation and stimulated microbial production of BVOCs. We suggest that the changes in the subarctic vegetation composition induced by climate warming will be the major factor indirectly affecting the BVOC emission potentials and composition.

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Dataset Information

Separating direct and indirect effects of rising temperatures on biogenic volatile emissions in the Arctic.

Publications

Separating direct and indirect effects of rising temperatures on biogenic volatile emissions in the Arctic.

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