EGU2020-12994
https://doi.org/10.5194/egusphere-egu2020-12994
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Impact of pollen on throughfall biochemistry in European temperate and boreal forests

Arne Verstraeten1, Elena Gottardini2, Nicolas Bruffaerts3, Fabiana Cristofolini2, Elena Vanguelova4, Johan Neirynck1, Gerrit Genouw1, Peter Waldner5, Anne Thimonier5, Anita Nussbaumer5, Mathias Neumann6, Sue Benham4, Pasi Rautio7, Liisa Ukonmaanaho7, Päivi Merilä7, Annika Saarto8, Jukka Reiniharju8, Bruno De Vos1, Peter Roskams1, Nathalie Cools1, and the ICP Forests - Aerobiology*
Arne Verstraeten et al.
  • 1Research Institute for Nature and Forest (INBO), Brussel, Belgium (arne.verstraeten@inbo.be)
  • 2Research and Innovation Centre, Fondazione Edmund Mach (FEM), San Michele all'Adige, Italy
  • 3Mycology and Aerobiology, Sciensano, Brussels, Belgium
  • 4Forest Research, Alice Holt Lodge, Farnham, Surrey, UK
  • 5Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
  • 6Institute of Silviculture, Vienna, Austria
  • 7Natural Resources Institute Finland (LUKE), Helsinki, Finland
  • 8Aerobiology, University of Turku, Turku, Finland
  • *A full list of authors appears at the end of the abstract

Pollen is known to affect forest throughfall biochemistry, but underlying mechanisms are not fully understood. We used generalized additive mixed modelling to study the relationship between long-term series of measured throughfall fluxes in spring (April–June) at forest plots and corresponding airborne pollen concentrations (Seasonal Pollen Integral, SPIn) from nearby aerobiological monitoring stations. The forest plots were part of the intensive long term monitoring (Level II) network of the UNECE International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) with dominant tree genera Fagus, Quercus, Pinus and Picea, and were distributed all across Europe. We also conducted a 7-day laboratory dissolution experiment with bud scales and flower stalks of European beech (Fagus sylvatica L.), pollen of beech, common oak (Quercus robur L.), silver birch (Betula pendula L.), Scots pine (Pinus sylvestris L.), Corsican pine (Pinus nigra Arnold ssp. laricio (Poiret) Maire), Norway spruce (Picea abies (L.) Karst.) and sterilized pollen of silver birch in a nitrate (NO3--N) solution (11.3 mg N L-1). Throughfall fluxes of potassium (K+), ammonium (NH4+-N), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) showed a positive relationship with SPIn whereas NO3--N fluxes showed a negative relationship with SPIn. In years with massive seed production of beech and oak SPIn and throughfall fluxes of K+ and DOC were higher, but fluxes of NO3--N were lower. The experiment broadly confirmed the findings based on field data. Within two hours, pollen released large quantities of K+, phosphate, DOC and DON, and lesser amounts of sulphate, sodium and calcium. After 24-48 hours, NO3--N started to disappear, predominantly in the treatments with broadleaved pollen, while concentrations of nitrite and NH4+-N increased. At the end of the experiment, the inorganic nitrogen (DIN) was reduced, presumably because it was lost as gaseous nitric oxide (NO). There was no difference for sterilized pollen, indicating that the involvement of microbial activity was limited in above N transformations. Our results show that pollen dispersal might be an overlooked factor in forest nutrient cycling and might induce complex canopy N transformations, although the net-impact on N throughfall fluxes is rather low.

ICP Forests - Aerobiology:

Arne Verstraeten1, Elena Gottardini2, Nicolas Bruffaerts3, Fabiana Cristofolini2, Elena Vanguelova4, Johan Neirynck1, Gerrit Genouw1, Peter Waldner5, Anne Thimonier5, Anita Nussbaumer5, Mathias Neumann6, Sue Benham4, Pasi Rautio7, Liisa Ukonmaanaho7, Päivi Merilä7, Annika Saarto8, Jukka Reiniharju8, Bruno De Vos1, Peter Roskams1, Nathalie Cools1, Geert Sioen1, Nicholas Clarke9, Volkmar Timmermann9, Hans-Peter Dietrich10, Manuel Nicolas11, Maria Schmitt5, Katrin Meusburger5, Silvio Schüler12, Anna Kowalska13, Idalia Kasprzyk14, Katarzyna Kluska14, Łukasz Grewling15, Joanna Święta-Musznicka16, Małgorzata Latałowa16, Marcelina Zimny16, Małgorzata Malkiewicz17, Lars Vesterdal18, Miklós Manninger19, Donát Magyar20, Hugues Titeux21, Gunilla Pihl-Karlsson22, Marco Ferretti5 1Research Institute for Nature and Forest (INBO), Geraardsbergen, Belgium 2Research and Innovation Centre, Fondazione Edmund Mach (FEM), San Michele all'Adige, Italy 3Mycology and Aerobiology, Sciensano, Brussels, Belgium 4Forest Research, Alice Holt Lodge, Farnham, Surrey, UK 5Swiss Federal Research Institute WSL, Birmensdorf, Switzerland 6Institute of Silviculture, Vienna, Austria 7Natural Resources Institute Finland (LUKE), Helsinki, Finland 8Aerobiology, University of Turku, Turku, Finland 9Norwegian Institute of Bioeconomy Research (NIBIO), Ås, Norway 10Bayerische Landesanstalt für Wald und Forstwirtschaft, Munich, Germany 11Office national des forêts, Fontainebleau, France 12Austrian Research Centre for Forests (BFW), Vienna, Austria 13Forest Research Institute, Raszyn, Poland 14University of Rzeszów, Rzeszów, Poland 15Adam Mickiewicz University, Poznan, Poland 16University of Gdánsk, Gdánsk, Poland 17University of Wroclaw, Wroclaw, Poland 18University of Copenhagen, Frederiksberg, Denmark 19NARIC Forest Research Institute, Sárvár, Hungary 20National Public Health Center, Budapest, Hungary 21Université catholique de Louvain, Louvain-la-Neuve, Belgium 22Swedish Environmental Research Institute IVL, Stockholm, Sweden

How to cite: Verstraeten, A., Gottardini, E., Bruffaerts, N., Cristofolini, F., Vanguelova, E., Neirynck, J., Genouw, G., Waldner, P., Thimonier, A., Nussbaumer, A., Neumann, M., Benham, S., Rautio, P., Ukonmaanaho, L., Merilä, P., Saarto, A., Reiniharju, J., De Vos, B., Roskams, P., and Cools, N. and the ICP Forests - Aerobiology: Impact of pollen on throughfall biochemistry in European temperate and boreal forests, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12994, https://doi.org/10.5194/egusphere-egu2020-12994, 2020

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  • CC1: Comment on EGU2020-12994, Anke Hildebrandt, 06 May 2020

    This is an impressive European scale analysis giving much food for thought. I am wondering whether other factors affecting throughfall quality may have influenced the results of the interannual study, e.g. the young leaf age coinciding with timing of the pollen production at least for the broadleaved species?

    • AC1: Reply to CC1, A. Verstraeten, 06 May 2020

      Dear Anke,

      thank you very much for your question. I think that herbivourous insects could influence the results somehow, because they appear as soon as the young leaves emerge. A study by Pitman et al. (2010) for the UK found that certain peaks of DOC in TF during the growing season were related to outbreaks of afids (honeydew). And there are caterpillars and other insects as well. However, I believe their overall effect is rather limited compared to the input by pollen/flowering, as for example for beech we can clearly see the difference between mast years and non-mast years. Also, by subtracting the fluxes during the previous and the following month from the (arbitrary chosen) 2-month pollen period, we partially eliminate the effect of insects.