Research in Context
Experimentation on
Ecophysiology of Urban Trees
A series of experiments on trees and climate change focus on the ecophysiology of trees.
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"Ecophysiology aims to explain how the trees work as a whole, what processes they contain and how they interact with the environment" (University of Helsinki 2025). The field of these studies on trees may be forest ecosystem or single urban trees.
Finland
At the University of Helsinki, the research group "Ecosystem processes" is conducting studies on the functioning and responses of boreal forest ecosystems. ​The interaction of physiological processes with the environment are monitored with instruments. Field measurements and laboratory experiment results may be the basis for modelling.
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Gas exchange of carbon dioxide (CO2) and water (H2O) and an array of different volatile organic compounds (VOCs)
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Photosynthesis can be measured at multiple spatial and temporal scales (from the leaf to the landscape, and from seconds to years).
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Water transport from the soil to the leaves and its consequent transpiration to the atmosphere from the leaf surfaces.
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Water transport is interconnected with the movement of phloem sap uptake and the transport and usage of carbon
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Root processes and root-fungal interactions and the effect on plants' C allocation. (University of Helsinki 2025)
Tree rows in a street in the city of Kerava in Finland. Image credit: Hanna Nyéki (2025).
Large trees in the city of Kerava in Finland Image credit: Hanna Nyéki (2025).
​​Post-doctoral Kaisa Risanenn, a member of the 'Ecosystem processes" group has joined an international network (UTEN) of twenty five researchers who cooperate in the study of the ecophysiology of urban trees.
Urban Trees Ecophysiology Network (UTEN)
UTEN is an international network of researchers aiming to understand the urban trees response to climate change and their ability to mitigate climate change effects such as air pollution and urban heat island (UTEN n.d.).
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This initiative has led to the creation of a broad worldwide network with many locations that host monitoring and experimentation at Universities or Reseach centers and the urban areas:
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Europe. Elsinki [Finland], Dresden [Germany], Lausanne [Switzerland], Clermont-Ferrand [France]
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Mid-Orient. Tel-Aviv [Israel]
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Africa. Johannesburg [South Africa]
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Australia. Sydney
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North America. Montreal [Canada], Northampton MA, Cambridge MA, Minneapolis–Saint Paul MN, Sacramento CA, Athens GA, Gainesville FL [USA]
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Central and South America. Bogotá [Colombia], Tandil [Argentina]
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The various locations are grouped on climatic similarities (Mantova et al 2024).​ On UTEN website's map the correlations between colors and environment classification:
blue points = cool and dry
orange points = hot and dry
yellow points = hot and wet​
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Official Website: https://www.uten-network.com/​
Website Map of Locations: https://www.uten-network.com/?lightbox=dataItem-lq4wlpbq​
UTEN locations - Interactive Map
Street trees in a borough of Montreal, Canada.
Image credit: A. Vardakis (2013).
Habitat tree in a park in the borough of Eira in Helsinki, Finland.
Image credit: Hanna Nyéki (2025).
Street trees in the square "Place Saint-François" in Lausanne, Switzerland. Researchers cooperate through the UTEN network and exchange data and insights on trees' response to the urban environment in many locations: Lausanne, Helsinki, Montreal et al. Image credit: Sophia Vardaki (2025).
Germany
Urboretum project.
Karlsruhe Institute of Technology (KIT)
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The Institute KIT is cooperating with other stakeholders and research centers on conducting experiments on city trees.
The aims of the Urboretum project are "Inter- and transdisciplinary measures to reduce tree mortality for preserving ecosystem services in cities in the face of increasing drought, heat stress, and urbanization" (Moosmueller 2025, KlimaZeit 2025). ​
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A better understanding of the ecology of city trees can guide the selection of suitable tree species in urban and peri-urban forests.
The city of Karlsruhe serves as a real laboratory due to its more than 200 species growing in the urban and periurban environment.
The project is managed by Somidh Saha with contributions by Dr. Tamalika Chakraborty, Jan Totzki, and Katrin Fröhlich.
The researchers have installed sensors on city trees in order to measure sap flow in relation to irrigation. In order to determine te ability of trees You want to measure the sap-free, that is how much water the tree can absorb water and transport it from the root to the crown.
"Some trees are watered, some in the spring, some in the summer and then there are trees that are not watered at all. And then we can see how the water flows in the tree when it is really dry or there is a drought period. The sensors collect data for two years." (KlimaZeit 2025, Urboretum 2025).
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​More information and interviews on the documentary by journalist Gina La Mela of SWR, news corporation (KlimaZeit 2025).
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Official Website: https://www.uten-network.com/​​
The city of Karlsruhe serves as a living laboratory for the study of more than 200 urban tree species.
Image credit: Yuliia Mazurkevych (2019). Magnificent view on Karlsruhe from top of Turmberg, Germany. [Online] Shutterstock
https://www.shutterstock.com/image-photo/magnificent-view-on-karlsruhe-top-turmberg-1394266418
France
Thermal InfraRed for Street Trees ( TIR4sTREEt ). Monitoring of city streets in Strasbourg.
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It is supported by ANR (Agence National de la Recherche), the University of Strasbourg, INRAE (Institut National de Recherche Scientifique) etc. ​The project carries out a campaign of thermal measurements in three streets of Strasbourg to study interactions between trees and the urban micro-climate facades. It aims to reveal the impact of the interspecific variety of street trees species. It is a succession of the ANR project "CoolTrees" which studied the physiology of lime tree species and its impact on parks' microclimat. (Landes et al 2024, Lecomte et al , Nature en ville 2024).
​Official Website: https://trio-climatologie-strasbourg.fr/​
At the city of Strasbourg, lime trees and other tree species are monitored for studying their interaction with the urban microclimate. Image credit: Leonid Andronov (2018). City tram crossing the Ill river in Strasbourg - Bas-Rhin, France
[Online] Shutterstock https://www.shutterstock.com/image-photo/city-tram-crossing-ill-river-strasbourg-1106641580
REFERENCES
UNIVERSITY AND RESEARCH WEBSITES
​Moosmueller, J.I. (2025).
KIT - ITAS - Organization - Projects - URBORETUM – Inter- and transdisciplinary measures to reduce tree mortality for preserving ecosystem services in cities in the face of increasing drought, heat stress, and urbanization.
Kit.edu.
https://www.itas.kit.edu/english/projects_saha24_urboretum.php
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TIR4sTREEt.
https://trio-climatologie-strasbourg.fr/
University of Helsinki. (2025).
Tree ecophysiology | Ecosystem processes | University of Helsinki. [online] Available at: https://www.helsinki.fi/en/researchgroups/ecosystem-processes/research/tree-ecophysiology
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Urban Trees Ecophysiology Network (UTEN).
PAPERS
Landes, T., Macher, H., Kastendeuch, P., Najjar, G., Nerry, F., Gangloff, J., Cuvillon, L., Durand, S., Lallement, A., Bonal, D., Breda, N., Saudreau, M., Ameglio, T., Serre, C., Bastianelli, C., Slisse, P., Lecomte, V., Colot, P. and Laille, P. (2024).
MODELING OF STREET TREES FOR URBAN MICRO-CLIMATOLOGY IN STRASBOURG -THE TIR4STREET PROJECT Modélisation des arbres urbains pour la climatologie urbaine à Strasbourg -Le projet TIR4sTREEt.
https://aic2024paris.sciencesconf.org/data/pages/AIC2024_Paris_LANDES.pdf
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Lecomte, V., Macher, H., Landes, T., Nerry, F., Cifuentes, R., Kastendeuch, P., Najjar, G., Delasse, C., Ii, H., Al Irfane, M., Allal, A., Fassi, E. and Maroc, R. (2024).
Thermal measurement campaign in three streets of Strasbourg to study interactions between trees and facades.
https://doi.org/10.25855/SFT2024-079
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Mantova, M., Johnson, D.M., Antebi, J., Beery, S., Blumstein, M., Cohen, R., Defavari, F., Feng, X., Feuer, E., Gersony, J., Hammond, W.M., John, G., Marchin, R.M., Mau, Y., Miller, B., Nibbelink, C., Ossola, A., Paquette, A., Rademacher, T. and Rissanen, K. (2024).
Monitoring urban trees across the world: report from the Urban Trees Ecophysiology Network (UTEN) inaugural workshop.
New Phytologist, 242(5), pp.1881–1885.
https://doi.org/10.1111/nph.19621.
TV BROADCASTS
KlimaZeit (2025).
KlimaZeit: Bäume und Hecken schützen für positive Auswirkungen auf Klima und Artenvielfalt - hier anschauen. [Climate time: protecting trees and hedges for positive effects on climate and biodiversity]
Ardmediathek.de.
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SCIENCE AND GREEN SPACES NEWS
​Nature En Ville. (2022).
Climatologie urbaine : suivi des arbres en ville à Strasbourg.
Plante & Cité.
https://www.nature-en-ville.com/sinspirer/climatologie-urbaine-suivi-des-arbres-en-ville-strasbourg