EGU24-15555, updated on 09 Mar 2024
https://doi.org/10.5194/egusphere-egu24-15555
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tracing diurnal variations of carbon and water cycle tracers over a tropical and temperate forest

Gerbrand Koren1, Kim A. P. Faassen2, Raquel González-Armas2, Getachew Agmuas Adnew3, Hella van Asperen4, Hugo de Boer1, Santiago Botía5, Oscar Hartogensis2, Lucas Hulsman2, Ronald W. A. Hutjes6, Sam P. Jones4, Shujiro Komiya4, Ingrid T. Luijkx2, Wouter Mol2, Michiel van der Molen2, Robbert Moonen7, Thomas Röckmann7, and Jordi Vilà-Guerau de Arellano2
Gerbrand Koren et al.
  • 1Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, The Netherlands
  • 2Meteorology and Air Quality Group, Wageningen University, Wageningen, The Netherlands
  • 3Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark
  • 4Biogeochemical Processes Department, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 5Biogeochemical Signals Department, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 6Water Systems and Global Change Group, Wageningen University, Wageningen, The Netherlands
  • 7Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Utrecht, The Netherlands

Diurnal temperature and carbon dioxide ranges are key metrics to quantify the impact of regional climate changes in forests. These ranges depend on biophysical processes, surface heat, water and carbon exchange, and boundary-layer dynamics. A crucial and elusive process is the entrainment of air from the free troposphere and residual air layers into the atmospheric boundary layer. Here we provide observational constraints on entrainment for two contrasting measurement sites: the Amazon Tall Tower Observatory (ATTO) in central Amazonia and the Loobos flux tower (NL-Loo) in a temperate forest in the Netherlands. We used radio soundings, air samples from tall towers and aircraft data in combination with surface air measurements and ecophysiological data. Fluxes and concentrations were measured for biophysical-process tracers  CO2, O2/N2, δ13C, δ18O (in CO2) and δ18O (in water). These novel tracers are proposed to partition gross carbon and water fluxes and for estimating plant properties and we present a unique dataset with our interpretation. Our analysis enables us to unravel the role of entrainment on the diurnal ranges and how this is controlled by surface and entrainment fluxes. By means of a coupled forest-atmosphere model constrained by the comprehensive observations, we perform a sensitivity study on the surface flux partitioning (photosynthesis versus soil respiration; soil evaporation versus plant transpiration, sensible versus heat flux) under a wide range of leaf traits, surface and boundary-layer dynamic conditions. Our results are useful to assess the performance of carbon-climate models in tropical and temperate forests.

How to cite: Koren, G., Faassen, K. A. P., González-Armas, R., Adnew, G. A., van Asperen, H., de Boer, H., Botía, S., Hartogensis, O., Hulsman, L., Hutjes, R. W. A., Jones, S. P., Komiya, S., Luijkx, I. T., Mol, W., van der Molen, M., Moonen, R., Röckmann, T., and Vilà-Guerau de Arellano, J.: Tracing diurnal variations of carbon and water cycle tracers over a tropical and temperate forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15555, https://doi.org/10.5194/egusphere-egu24-15555, 2024.