EGU23-13401, updated on 19 Apr 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Drought effect on urban plane tree ecophysiology and its isoprene emissions 

Ruben Puga Freitas1, Alice Claude1, Alice Maison2,4, Luis Leitao1, Anne Repellin1, Paul Nadam1, Carmen Kalalian3, Christophe Boissard3, Valérie Gros3, Karine Sartelet2, Andrée Tuzet4, and Juliette Leymarie1
Ruben Puga Freitas et al.
  • 1Institute of Ecology and Environmental Sciences of Paris (iEES-Paris), Universite Paris Est Creteil (UPEC), Créteil, France
  • 2Centre d'Enseignement et de Recherche en Environnement Atmosphérique (CEREA), École des Ponts ParisTech-EDF R&D, Marne la Vallée, France
  • 3Laboratory of Climate and Environmental Sciences (LSCE), CNRS-CEA-UVSQ, Gif sur Yvette, France
  • 4UMR Écologie fonctionnelle et écotoxicologie des agroécosystèmes (ECOSYS), INRAE, Thiverval-Grignon, France

Urban trees emit a wide range of biogenic Volatile Organic Compounds (bVOC). Some of these bVOC, like isoprene can react with atmospheric oxidants to form secondary compounds, such as ozone (O3) and secondary organic aerosols (SOA), which have impacts on air quality and climate. In addition, isoprene emissions are strongly influenced by environmental factors and urban sites are known as stressful environment, characterized for example by water scarcity. However, little is known on the contribution of urban trees to air quality, notably during drought periods. In a semi-controlled experiment, fourteen young plane trees (Platanus x hispanica, known as a strong isoprene emitter) were grown in containers, in an urban site (at Vitry-sur-Seine, near Paris), since 2020. In June 2022, half the trees were subjected to drought by total rainfall exclusion and by withholding watering. A comprehensive characterization of tree response to drought, including plant morphology (leaf density and area), water status (i.e., leaf water potential, δ13C isotopic composition) and physiology (stomatal conductance, net photosynthesis, leaf pigment contents, stress molecular markers, chlorophyll fluorescence) analyses, was undertaken along with the characterization of bVOC emissions by an original leaf scale method (portable GC-MS coupled to a leaf chamber). All together, these parameters provided relevant information on the relation between bVOC emissions and plant morphology, its water use efficiency and photosynthetic energy conversion.

Shortly after the onset of drought, the isoprene emissions of the plane trees remained unchanged even though typical responses to drought stress were observed, such as partial stomatal closure leading to a decrease in carbon assimilation. With the progression of drought stress, progressive leaf shedding occurred. When almost completely defoliated, the trees emitted lower amounts of isoprene emissions likely due to disruption of the photosynthetic energy conversion process. Despite the moderate decrease in absolute isoprene emissions rates (as expressed per dry leaf mass) induced by the drought treatment on plane trees with nearly zero gas exchange, total emissions were strongly affected because defoliation significantly reduced the total leaf area. We emphasize that this phenomenon should be taken into account in atmospheric models especially in species highly subjected to drought induced defoliation. Here, a simple parameterisation of this effect on plane tree-bVOC emissions is proposed.

How to cite: Puga Freitas, R., Claude, A., Maison, A., Leitao, L., Repellin, A., Nadam, P., Kalalian, C., Boissard, C., Gros, V., Sartelet, K., Tuzet, A., and Leymarie, J.: Drought effect on urban plane tree ecophysiology and its isoprene emissions , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13401,, 2023.