Date: 12th January 2022
Time: 13:00 - 15:15
Location: Remotely via Zoom
Host: Mari Pihlatie
Daniel Epron (13:00-14:00)
Title: Emissions of methane from tree stems: where does methane come from and where does it go?
Abstract: Forests are a well-known carbon sink, which mitigate the rise in atmospheric CO2 and hence global warming. However, methane emissions by stems of living trees become a major concern due to the increasing contribution of methane to global warming. Indeed, methane is the second most important anthropogenic greenhouse gas. Until now, most global and regional methane budgets of forests have only considered the source and sink functions of soils, ignoring stem emissions. However, there are growing evidences that trees emit methane through their stem, and the role of trees, in addition to that of the soil, must be considered in the methane budget of forests. A final goal will be to upscale stem CH4 emissions to the ecosystem and regional levels. But a first prerequisite is to understand the variability of stem CH4 emissions across individuals and species, and within individuals. A second is to clarify if methane is produced within the heartwood of the trunk, and how heartwood production and trunk emission are related.
Daniel Epron’s research activity focuses on the ecophysiological aspects of forest carbon budget. He has investigated the contribution of root and soil to the carbon budget of forests and tree plantations, both in temperate and tropical areas, with a special attention to environmental controls of phloem translocation and to carbon partitioning among ecosystem compartments. For several years, he has aimed to include methane fluxes in the carbon balance of forests. With his former group at the University of Lorraine in France, he has studied CH4 fluxes of forest soils, including the effects of soil compaction on the overall soil CH4 budget, and the role of the vegetation, including understory grasses and tree stems. After arriving at Kyoto University in Japan, he began in 2020 to implement a new research project on stem CH4 emission in a cold temperate mountain forest, while continuing to work of the ecophysiology of phloem transport.
Riikka Rinnan (14:15-15:15)
Title: Plant volatile emissions from the warming Arctic
Abstract: Arctic areas are experiencing amplified climate warming that proceeds twice as fast as the global temperature increase. The rising temperature is already causing evident alterations, e.g. changes in the vegetation cover as well as thawing of permafrost. Climate warming and the concomitant biotic and abiotic changes are likely to have strong direct and indirect effects on the production and emissions of volatile organic compounds (VOCs) from arctic ecosystems.
We have used long-term field manipulation experiments to assess effects of climate change on tundra VOC emissions. In these experiments, we have observed emission increases by a factor of 2-5 under experimental warming, and this strong temperature response has also been confirmed by ecosystem-scale data. Climate change is also increasing the abundance of insect herbivores. As insect herbivores can also induce production and release of VOCs, we have assessed the importance of herbivore-induced plant volatiles and their interactions with warming in the Sub-Arctic tundra and mountain birch forests. Our work shows that during the active insect-feeding periods, the effect of herbivory on VOC emission rates and emission compositions can override those of climatic warming. In this talk, I present our recent findings on experimental and modeling work, showing how VOC emissions in high latitude ecosystems may be directly affected by climate change and insect herbivory and indirectly affected by vegetation changes.