Oak leaves can withstand more than 50 degrees Celsius
Published: Wednesday, Aug 7th 2024, 10:30
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The leaves of oak trees can tolerate heat of over 50 degrees Celsius. Researchers from Birmensdorf ZH and Lausanne have come to this conclusion. They measured the temperatures in the hot summer of 2023 in Switzerland, southern France and Spain.
This was announced by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) on Wednesday. It conducted the study together with the Swiss Federal Institute of Technology Lausanne (EPFL).
"The uppermost leaves of the crowns reached temperatures of up to 50 degrees Celsius in August, which is pretty incredible," study leader Charlotte Grossiord is quoted as saying in the press release. This was at an air temperature of well below 40 to 42 degrees.
The team used various tools for the measurements. For example, drones with infrared thermal imaging cameras were used. In the Jura region of Basel, the researchers used a crane to go up into the air because the sessile oaks there are around 30 meters high. In France, on the other hand, scaffolding was sufficient to measure the holm oaks. And in Spain, no tools were needed as the Kermes oaks only grow to a height of 1.5 meters.
Deciduous trees will suffer
The researchers assume that their extreme heat tolerance saved the oaks. The scientists estimated this tolerance by exposing leaves to increasing temperatures in a water bath. They found that the critical temperatures only begin at almost 50 degrees Celsius. The oaks in France and Spain can tolerate leaf temperatures of up to 51 and 53 degrees Celsius respectively, while the sessile oaks in Switzerland can withstand even higher temperatures of 59 degrees Celsius.
Nevertheless, the results suggest that deciduous trees will suffer in the event of more frequent heatwaves, the researchers write. "Some species are likely to reach their limits when heatwaves become more extreme," study leader Grossiord is quoted as saying. This was already evident in Switzerland in the summer of 2018, when numerous beech trees withered on poorly water-storing soils.
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