A team of French scientists have conducted experiments which suggest that trees make noises when they are thirsty.
The tests, run at Grenoble University, have revealed ultrasonic pops, released too quickly for the human ear to detect, in slivers of pine.
The slivers were immersed in a hydrogel that was then treated to approximate an arid environment. Using sensitive equipment, scientists listened to the resulting air bubbles.
Says lead researcher Philippe Marmottant: “The majority of the sounds that we heard were linked to bubbles. I say majority, because there may be other causes like cracks in the wood or insects. But the majority of sounds occur during cavitations (tiny air bubbles that pop out in the water).”
The air bubbles are a sign that the tree is trying to vacuum up water from the ground through its root system, pulling it up through a complex system of xylem tubes. In times of drought, trees enter a state of tension.
Some species of trees can heal themselves, says Katherine McCulloh, a plant ecophysiologist at Oregon State University in the US. Others, however, will die from lack of moisture.
The race is now on across the globe to develop devices to detect trees in need of moisture. Such tools can address the
issue of desert and overfarmed land. Acoustic sensor technology, similar to that used to monitor bridge cracks, looks promising, says Marmottant.
Category: Summer 2015