Laboratory study of thermal and physiological responses of vegetated and artificial shading devices

With global warming, the frequency and intensity of heatwaves are set to increase over the next ten years (IPCC, 2023). As the world's urban population increases, reaching 75% by 2050 (UN, 2015), urban habitability during heatwaves is a major global challenge.

Among the existing solutions for adaptation, the greening of urban spaces represents several co-benefits (landscape, biodiversity, well-being) (ADEME, 2021). A great deal of research has been carried out into the cooling potential of vegetation (Thierry, 2024). But how do plants cope with the constraints of the city and heatwaves?

Plants emit signals in their vessels which are involved in many plant life processes and trigger physiological responses such as the regulation of transpiration, respiration, photosynthesis, etc. (Yan et al., 2009). By monitoring these signals, we can better understand what environmental changes plants perceive and integrate to adapt.

Experimental work under controlled conditions in a climatic chamber imposing temperature and relative humidity ramps will enable us to compare two shading systems: one vegetated and the other inert with cloths. Different fabrics will be tested, as well as different climatic conditions (temperature and humidity). Plants will be tested under different water conditions.

To compare the cooling performance of the two systems, evapotranspiration, temperatures and heat flows will be measured. In addition, to consider plants as living beings beyond their cooling role, photosynthesis potential and electrical signals emitted by plants will be monitored.

The aim is to understand the correlations between plant physiological state and cooling under different thermal and hydric conditions.

References    

ADEME (2021) Rafraîchir les villes, des solutions variées. ADEME.

IPCC (2023) Synthesis Report.

UN (2015) Goal 11.

Thierry, J. (2024) Impact of street trees on urban microclimate and human thermal stress: effect of heatwaves and droughts. Agrocampus Ouest.

Yan, X. et al. (2009) ‘Research progress on electrical signals in higher plants’, Progress in Natural Science, 19(5), pp. 531–541.