EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Insect herbivory have significantly altered BVOC emissions, SOA concentration and radiative forcing over Fennoscandian birch forest

Jing Tang1,2, Hui Wang3, Zhanzhang Cai1, Alex Guenther3, Riikka Rinnan2, Per-Ola Olsson1, Rikke Lauge Borchmann2, Cleo Lisa Davie-Martin2, Guy Schurgers4, Zhengchao Ren5, Jolanta Rieksta1, and Tao Li6
Jing Tang et al.
  • 1Department of Physical Geography and Ecosystem Science, Lund University, Sweden
  • 2Department of Biology, University of Copenhagen, Denmark
  • 3Department of Earth System Science, University of California, Irvine, USA
  • 4Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark
  • 5Research Center of Ecological Construction and Environmental Conservation, Gansu Agricultural University, China
  • 6College of Life Sciences, Sichuan University, China

Over Fennoscandian mountain birch forest region, there are increased attacks of geometrid moth larvae. These herbivores can change forests from a carbon sink to a carbon source. When moths start to chew on leaves, large quantities of biogenic volatile organic compounds (BVOCs) are released. Herbivory-induced BVOC emissions have been observed and quantified at a few sites over Fennoscandian mountain birch forest, but we know very little of their potential regional implications for atmospheric processes.

In this work, we extracted birch defoliation information based on MODIS leaf area index (LAI) for an outbreak year 2012, and together with field-observed relationship between leaf defoliated level and changes in emissions, we modelled herbivory-induced BVOC emissions at regional scale using MEGAN. Taking a step further, we fed MEGAN-modelled BVOC emission data with or without considering herbivory impacts to a two-way coupled WRF-CMAQ system to dynamically assess the impacts of these emissions on the atmospheric chemistry and climate system .

During the whole growing season of 2012, the defoliation at some MODIS grids can be as high as 90%, and the large defoliation mainly occurs in June and July. For t-β-ocimene, Other Monoterpenes, Stress and Other compound groups, herbivory contributes to more than 30, 8, 5 and 16 times the increase in the seasonal sum for the defoliated regions. For terpenes, herbivory increased monthly emissions up to 3 times for June and July. The reduction of emissions caused by herbivory-caused decrease in LAI is much smaller than the herbivory-induced increase. We also found strong impacts of herbivory-induced BVOC emissions on downward shortwave radiation and cloud radiative forcing.

This is the first time we can link all these components, i.e., satellite monitoring of leaf defoliation, in-situ observation, ecosystem and atmospheric modelling together to answer the research questions related to the regional importance of insect herbivory on atmospheric composition and climate.

How to cite: Tang, J., Wang, H., Cai, Z., Guenther, A., Rinnan, R., Olsson, P.-O., Borchmann, R. L., Davie-Martin, C. L., Schurgers, G., Ren, Z., Rieksta, J., and Li, T.: Insect herbivory have significantly altered BVOC emissions, SOA concentration and radiative forcing over Fennoscandian birch forest, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12434,, 2023.