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Case studies of pollen spread within a Central European Forest canopy

Martin Piringer (ZAMG),

Silvio Schüler (BFW)

Bundesforschungs- und Ausbildungszentrum für Wald, Naturgefahren und LandschaftInstitut für Genetik

Zentralanstalt für Meteorologie und Geodynamik

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Martin Piringer et al.

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Outline

Site characteristics and topography of the study area

Pollen sampling and meteorological observations

Meteorological interpretation of the time course of pollen concentrations

Results for three episode days with enhanced pollen production

Summary and conclusions

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Site characteristics

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Topographic detailsaround the lower tower

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Instrumentation on the lower tower

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Meteorological parameters

Ultrasonic anemometers at the three levels of the tower deliver

- wind direction and speed- vertical velocity- standard deviations of wind components

From sonic temperature fluctuations:- Obukhov length- friction velocity- sensible heat flux

Analog sensors: air temperature, humidity Vapour pressure deficit: VPD = esat – ecurr

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Phenological observations

all trees (487) within a radius of ~ 50 m around the tower have been identified, marked, measured and mapped (in progress)

During flowering and flushing – every 2-4 days, all trees were visually surveyed for the status of flowering and flushing

To determine exactly which tree flowered at which day

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Pollen counts A new vertical pollen collector which allows continuous sampling of pollen from all

directions with high temporal resolution has been developed The spore trap comprises a chamber into which air is drawn through the top of

the trap with the aid of a fan. A small part of air-stream impacts on a slowly rotating drum, which is operated by

a clockwork mechanism to revolve once every seven days, every two days or every day.

The drum is covered by a transparent plastic tape, which is coated with vaseline, on which airborne particles are trapped.

The tape is replaced every week and then cut into seven sections and mounted for microscopy.

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top of the trapchamber

drum

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Example of pollen transport to the area

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ECMWF backwards trajectories arriving on 23. 4. 09 at 0:00 UTC (yellow), 3:00 UTC (green) and 6:00 Uhr (red)

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All backwards trajectories 925 hPa, Norway spruce

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Trees flowering and pollen measuredon site

Trees not flowering, but pollen measured on site

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Meteorological analysis of measured pollen concentrations (I)

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VPD = esat – ecurr

esat = saturation vapour pressureecurr = actual vapour pressure

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Meteorological analysis of measured pollen concentrations (II)

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VPD = esat – ecurr

esat = saturation vapour pressureecurr = actual vapour pressure

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Dispersion of pollen: outline of method

Lagrange particle diffusion model LASAT Met. Input: Time series of wind direction, wind speed, MOL, standard

deviations of the wind components from the upper platform of the tower Pollen emission rates determined via „inverse dispersion technique“

Result: Field of pollen concentrations, averaged over the hours of pollen release (assumption: all measured pollen released in situ, no advection)

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Pollen transport: results for oak

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Pollen transport: results for Norway spruce

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Summary and conclusions

Special data set of simultaneous pollen and met. measurements at the same levels of a 36 m high tower

Advection of pollen can be explained by analysis of backwards trajectories

Vertical velocity determines pollen spread within the canopy

VPD influences pollen release; also important: stand. dev. of wind components, wind speed

Modelling pollen transport: most pollen remain within study area due to low wind speeds and good vertical mixing on pollen release days

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Thank you very much for your attention!

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