Extreme heatwaves are arising due to climate change. Forest can withstand hot temperatures but when is the situation critical for forest trees? \u201cDuring the hot summer of 2023, a research team led by EPFL and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) investigated this in Switzerland, southern France and Spain.\u201d<\/p>\n
\u201cThe team used drones with infrared thermal imaging cameras. These flew over forests in Switzerland, France, and Spain on hot days and recorded the temperature of the uppermost leaf layer. The researchers also measured photosynthesis and water loss in the leaves on branches in the treetops.\u201d<\/p>\n
\u201cThe results show that the oaks can withstand astonishing temperatures.The oaks in France and Spain can withstand leaf temperatures of up to 51 and 53 degrees Celsius, respectively, while the sessile oaks in Switzerland can even withstand 59 degrees Celsius.\u201d<\/p>\n
The fact that they rarely reached this level is probably due to another process: The leaves always lost a little water, the measurements show. Trees indeed close the pores on the underside of their leaves at some point during hot weather, through which they absorb and release gases. But a little water evaporates passively through the leaf surface. It cooled the leaves just enough. Only the most exposed leaves at the top of the canopy turned brown and dry.<\/p>","protected":false},"featured_media":41409,"template":"","acf":[],"yoast_head":"\n