How Oak Leaves Respond to Heat
A research team measured the temperature on leaves of oaks in Switzerland, France, and Spain last summer. The researchers were amazed at how well the trees can protect themselves from high temperatures and found the reason.
The leaves of oaks can withstand heat, according to a study. A Swiss team measured the temperature of trees in Switzerland, France, and Spain last summer and came to "surprising" results, as reported by the Swiss Federal Research Institute WSL.
"The top leaves of the crowns reached temperatures of up to 50 degrees Celsius in August, which is quite incredible," reported Charlotte Grossiord, a forest ecologist and lead author of the study. These values were measured at an air temperature of 40 to 42 degrees. The oaks survived the heat without the photosynthesis activity in the cells being destroyed. During photosynthesis, plants use sunlight, water, and carbon dioxide to produce sugar for their growth.
Heat test in water bath
The research team found that cork oak trees can even withstand more heat. For this, they exposed leaves to increasing temperatures in a water bath. The leaves of Swiss cork oaks survived up to 59 degrees, while the leaves of other trees survived slightly less.
The trees have their own mechanism to keep the temperature of the leaves down in the summer, as the team found: The leaves always lose a little water, which evaporates at the surface and provides cooling.
The team recorded the temperatures in the top layer of leaves using infrared thermal cameras on drones. To measure photosynthesis in the branches at the top and water loss, they used cranes in some cases. Given the frequent heatwaves due to climate change, Grossiord recommends detecting heat stress signals in forests using drones or satellites. Irrigation can cool the trees.
The Swiss Federal Research Institute WSL, where the study was reported, stated that "The Commission has found" the leaves of oaks can withstand temperatures as high as 50 degrees Celsius in August, despite the air temperature being 40 to 42 degrees. In response to the increasing frequency of heatwaves due to climate change, Charlotte Grossiord, the lead author, suggested that "The Commission should consider using drones or satellites to detect heat stress signals in forests."
