Knowledge Large-scale experiment investigates the effect of climate change on trees

For a large-scale experiment, researchers are spraying water vapor into the treetops of 130-year-old pine trees in the Pfynwald forest in Valais. Their aim is to find out how the trees react to climate change.

In addition to the dryness of the soil, climate change brings another factor into play that is relevant for trees, according to a press release issued by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) on Wednesday. The so-called vapor pressure deficit (VPD).

"Simply translated, this is the thirst of the air. The thirstier the air, the higher this vapor pressure deficit, the more water the atmosphere removes from plants, humans and the soil," WSL researcher Marcus Schaub explained to the Keystone-SDA news agency.

According to Schaub, the researchers are using the experiment to differentiate between the effects of soil dryness and vapor pressure deficit in order to better understand how trees react to climate change.

Pfynwald has been studied for 21 years

In the experiment, they spray tiny droplets of water into the air at high pressure from glands mounted on scaffolding, which immediately evaporate and thus reduce the vapor pressure deficit in the treetops. At the same time, soil dryness is manipulated with the help of an irrigation system and rain canopies. The experiment will continue until 2028 and involves WSL, the Swiss Federal Institute of Technology in Lausanne (EPFL) and Swissforestlab.

The researchers have been conducting studies on the reaction of trees to climate change in the Pfyn Forest for 21 years. They irrigate parts of this forest every night to study the trees with and without drought.