Periodic Reporting for period 3 - TUVOLU (Tundra biogenic volatile emissions in the 21st century)
Berichtszeitraum: 2021-04-01 bis 2022-09-30
In the insect herbivory-focused WP2, we have conducted field work in Abisko, Sweden (2018-2020), Tromsø, Norway (2018) and Narsarsuaq, Greenland (2019). Our work on the effects of insect herbivory started with an experiment, in which we used methyl jasmonate (MeJA) to mimic insect herbivory on the dwarf birch, Betula nana. We showed that the MeJA-treatment strongly increased BVOC emissions and changed the profile of compounds released (Li et al. 2019, Nature Plants). Interestingly, climate warming strongly amplified this response. To feed on the modelling work in WP5, we have conducted three experiments to assess how the number of feeding larvae impacts BVOC emissions of the mountain birch B. pubescens var. pumila. The results indicate that there is a strong positive relationship between the number of larvae and the BVOC emissions (Rieksta et al. 2020, Frontiers in Plant Science).
In WP3 with the focus on permafrost thaw emissions, we have shown that thawing permafrost releases considerable amounts of BVOCs, especially ethanol and methanol, but that the emissions to the atmosphere are lower due to active microbial uptake of BVOCs during their passage through the active layer soil (Kramshøj et al., 2018, Nature Communications). The microbial uptake may be an important, overlooked process, which functions efficiently for all kinds of BVOCs in all soils (Albers et al. 2018, Biogeosciences; Rinnan & Albers 2020, JGR Biogeosciences). The net amount and composition of BVOCs released to the atmosphere depends also on the water content of the soil, which determines the oxygen content (Kramshøj et al. 2019, Global Change Biology).
The modelling work in WP5 has been proceeding in parallel with measurement activities. We wrote a review article to summarize the current understanding and to identify knowledge gaps in modelling soil BVOC-related processes (Tang et al. 2019, Reviews in Geophysics). New leaf temperature algorithms are developed in collaboration with WP1 using leaf-level data collected (Simin et al. submitted; Simin et al. in preparation) and the ecosystem level data are used for model validation (e.g. Seco et al. 2020). Herbivory (leaf area loss)-BVOC emission relationships have been assessed by experimental work in WP2 to be able to develop algorithms for model improvement.
Our pioneering finding about BVOC release from permafrost thaw has been complemented with process understanding related to separation of BVOC production/release versus uptake in soil. We showed that while thawing of permafrost soil can release a high amount of certain BVOCs and a high diversity of compounds in general (Kramshøj et al. 2018, Nature Communications), the actual emission to the atmosphere is dependent on the balance between the release and microbial uptake processes that appear to be ubiquitous (Rinnan & Albers 2020, JGR Biogeosciences) and affected by environmental conditions (Kramshøj et al. 2019, Global Change Biology). 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 have provided novel understanding on the importance of insect herbivory in affecting BVOC emissions in the Arctic. Our work shows that while increasing temperatures have very strong effects on BVOC emissions from arctic ecosystems, the effect of herbivory is even more drastic for certain compounds during active insect feeding periods. Surprisingly, the responses to insect herbivory also appear to be strongly amplified by temperature, highlighting the importance of ecosystem-atmosphere interactions in the changing Arctic (Li et al. 2019, Nature Plants).