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STORIES

Welcome to the homepage of Lars L. Iversen - Freshwater kid and PhD Fellow from Copenhagen, Denmark,
 

Come meet us at the ASLO-SIL 2026 meeting

Lars Iversen

Please check out Life in Mud lab members’ talks, posters, and sessions at the ASLO 2026 meeting! Below is an overview of where you can find us throughout the conference.

Sessions

Talks

Posters

Lab collaborators:

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Lars Iversen

Starting a new lab at McGill University

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In January 2022 I will be moving my research to McGill University, Canada. In the new lab we will expand our work on freshwater ecosystems and how these are responding to global change. Both within Canada and across the globe we will document how functional adaptations to life in freshwater environments structure species distributions and how human impacts challenge the future of freshwater functions and services.

Join the lab!

We are recruiting lab members to join us at the Department of Biology at McGill University. If you are interested in spatial aspects of ecology, classic freshwater ecology, or macroecology our lab might be your fit. Although our aim is to advance freshwater ecology, interest and skills across these themes are not required in order to join the group. Through collaborations and personal development we seek to explore the broader goals in our lab while supporting personal research interests and strengths.

The lab provides a supportive and inclusive environment for members of all backgrounds to facilitate independence as scientists. We value people who have the capacity to succeed, rather than simply those who have always succeeded before. The lab provides close mentoring support via regular meetings, an open-door policy, personal development plans, and a strong community knowledge sharing between undergraduate students, graduate students, and postdoctoral researchers.

Postdoc applications are actively considered as of August 2021, graduate and undergraduate recruiting will start January 2022

Postdocs: If you found interest in our lab please email me to discuss shared research interests and potential projects. McGill has a number of fellowship opportunities, including NSERC (due Oct.), Banting (due Sept.), Liber Ero (due Nov.), and the FRQNT (due Oct.). I am happy to provide feedback on application materials.

International Postdocs are welcomed in the lab, if you have national funding opportunities to do research abroad I am happy to discuss how we can support potential applications. Researchers from China should consider the CSC program

For people interested in transnational postdocs between McGill and European partners or would like to return to a preferred European university following a postdoc in our lab we do support Global Marie Curie Fellowships (due Oct)

Grad students: I seek curious, motivated students with some prior research experience (e.g., work learn experience, undergraduate research). I have an open call for a funded position in the lab. For more info see the application flyer.

Undergrads: If you are interested in obtaining research experience during your undergraduate studies McGill offers a number of opportunities. Please explore potential opportunities here and here.

If you are interested in joining the lab as an undergrad or grad student please email your CV and a short summary of your research interests to lars.iversen@mcgill.ca

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Warming tundra and the emission of volatile organic compounds

Lars Iversen

Current climate warming in Arctic regions is driving changes in the structure and composition of tundra ecosystems. This is causing shifts in local plant communities and changes the physiological stress that plants experience during a growth season. One response to increasing temperatures is system wide increases in the amount of reactive gases, so-called volatile organic compounds (VOCs), that plants release to the atmosphere. The increasing VOC flux from the Arctic tundra to the atmosphere may have implications via climate feedbacks, for example, through particle and cloud formation in these regions with low anthropogenic influence. We know that the release of VOCs from vegetation is both temperature-dependent and controlled by vegetation composition because different plant species release a distinct blend of VOCs. Hence, the interplay between such pathways from climate warming to plant VOC emissions are important in our general understanding of how Arctic ecosystems are responding to a changing climate.

In a recent paper published in PNAS we outline the presence and relative importance of two causal path ways from local temperature to plant VOC emissions. Using both spatial hierarchical correlation models and ecosystem dynamics models we quantify the direct (plant stress) and indirect (structuring vegetation cover) effect of temperature on VOC emission in the Arctic.

The Arctic tundra vegetation at the islands of Disko in West Greenland is responding rapidly to climate warming. Causing a shift and increase in the volatile organic compounds released by the vegetation.

The Arctic tundra vegetation at the islands of Disko in West Greenland is responding rapidly to climate warming. Causing a shift and increase in the volatile organic compounds released by the vegetation.

The study builds on several years of warming experiments and dynamic ecosystem modelling work done at the University of Copenhagen by Riikka Rinnan and Jing Tang. Using data from 11 years of monitoring at four Arctic sites we show that temperature is simultaneously changing VOC emissions rates directly and indirectly via vegetation composition. However, within individual groups of compounds the direct effect was in most cases larger compared the indirect.

Local correlations between temperature and volatile organic compound emissions. Top left: Camber measurements of VOC emission for a given vegetation type.  Top right: The conceptual model tested via a structural equation model, in which te…

Local correlations between temperature and volatile organic compound emissions. Top left: Camber measurements of VOC emission for a given vegetation type.  Top right: The conceptual model tested via a structural equation model, in which temperature and soil moisture affect VOC emissions directly or indirectly by structuring the vegetation cover. Bottom: Structural equation models representing direct and indirect linkages of environmental factors on VOC emission. An example of a structural equation model for monoterpene emission. Solid arrows represent significant linear paths supported by the model; dashed lines are omitted paths. Values represent standardized effect sizes.

These findings were mirrored at larger scales, using a process-based dynamic ecosystem model for the compounds in the isoprene and monoterpenes groups. By manipulating the presence of plant establishment, mortality, disturbance, and growth, as well as soil biogeochemical processes in response to input climate variability, we compared two different scenarios: One in which warming only affects the VOC production rate and emission, but without warming-induced vegetation changes (direct effects), and one in which warming affects both the VOC production and emission, as well as vegetation dynamics (direct + indirect effects). 

 From this we show that warming alone caused large increases in annual isoprene and monoterpene emissions averaged across the Pan-Arctic region, with larger increases for 4 °C than 2 °C warming. Including indirect temperature effects (e.g., via phenology, vegetation dynamics, and plant physiological processes under a warmer climate allowing for longer growing seasons) further enhanced this increase, but again with relatively smaller magnitude compared to the direct warming effects.

Relative changes in isoprene emission under direct and indirect effects of warming by 2 °C (A and B) and 4 °C (C and D). A and C show the direct effect on isoprene production and emission rate, and (B and D) show the direct + indirect effects mainly…

Relative changes in isoprene emission under direct and indirect effects of warming by 2 °C (A and B) and 4 °C (C and D). A and C show the direct effect on isoprene production and emission rate, and (B and D) show the direct + indirect effects mainly through changes in vegetation composition and vegetation-related processes averaged for the period 1999–2012. Notice the large local differences in B and D.

In summary, we show that ongoing warming has strong direct increasing effects on VOC emissions from Arctic ecosystems and also indirect effects resulting from alterations in vegetation composition and biomass. Exactly what this means for local-to-regional impacts on atmospheric composition is still to be understood. However, forecasting how plant communities will change in response to climate change is challenging and our work outline the complexity of the mechanisms driving Arctic VOC emissions.

Paper reference:

Rinnan R., Iversen L. L., Tang J., Vedel-Petersen I., Schollert M. & Schurgers G. (2020): Separating direct and indirect effects of rising temperatures on biogenic volatile emissions in the Arctic. PNAS. DOI: 10.1073/pnas.2008901117

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