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| Titel |
Drought impact on Quercus pubescens Willd. isoprene emissions over the Mediterranean area: what future? |
| VerfasserIn |
Anne Cyrielle Genard-Zielinski, Christophe Boissard, Elena Ormeño, Juliette Lathière, Bertrand Guenet, Thierry Gauquelin, Catherine Fernandez |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102384
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| Publikation (Nr.) |
 EGU/EGU2015-1699.pdf |
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| Zusammenfassung |
| Biogenic Volatile Organic Compounds (BVOCs) released by plants mostly originate from
their secondary metabolism. Their emissions are modulated, in terms of intensity
and molecule diversity, by environmental conditions. Among BVOCs, isoprene
has been especially studied due to its high emission fluxes and its contribution to
tropospheric photochemistry, both in the gaseous and particulate phases. However, the way
isoprene emissions are impacted by some abiotic factors, especially water stress, is still
under debate. In a world facing climatic changes, global climate models expect
air temperature and drought intensity to strengthen in the Mediterranean area by
2100.
Our work focuses on the impact of water stress on isoprene emissions (ERiso) from
Quercus pubescens Willd. This species covers large areas of the Mediterranean area where it
appears to be the main isoprene emitter. An in situ experimentation was performed at the
O3HP (Oak Observatory at OHP, southern France) in a pubescent oak forest with trees
adapted to long lasting stress periods. We investigated during a whole seasonal
cycle (from June 2012 to June 2013) the course of ERiso under both natural water
stress (control treatment: C) and intensified water stress (stress treatment: S) by
artificially reducing rain by 30% using a specific rain exclusion device. Restricted rain
did not modify either the net CO2 assimilation or ERiso during the whole season.
However, isoprene emission factors (Is) for trees under S were significantly higher (a
factor of ≈ 2) than for trees growing under C in August (137.8 compared to 75.3
μgC.gDM-1.h-1 respectively)Âand September (75.3 compared to 40.2 μgC.gDM-1.h-1
respectively).
Based on our experimental emission database, an appropriate isoprene emission algorithm
(GZ2014) was developed using a statistic approach (an artificial neural network). Using
ambient and edaphic environmental parameters integrated over up to 3 weeks, GZ2014 was
found to represent more than 80% of ERiso variations, during natural and intensified water
stress. Soil water content cumulated over 2 and 3 weeks was found to be the dominant
parameter among the others considered in GZ2014. In comparison, isoprene seasonal
variations at O3HP were poorly represented by the MEGAN model during both natural and
intensified drought periods.
Based on GHG-Europe forcings and ORCHIDEE model outputs, GZ2014 was used to
predict changes of Q. pubescens isoprene emission between present and 2100. In 2100,
maximum isoprene emissions were found to occur earlier (June instead of August) with
values 3.5 times higher in 2100 than at present.
Keywords: Biogenic volatile organic compounds (BVOCs), isoprene emissions, water
stress, drought, artificial neural network, climate changes, ORCHIDEE. |
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