Eavesdropping on thirsty trees
It’s long been known that cavitations — air bubbles that block the flow of water throughout the tree — make a sound that can be heard with a microphone. If too many of these cavitations occur, such as we might see in drought conditions, a tree can die.
The problem is that the sounds of cavitations, among other tree activity, are outside our usual range of hearing and can only be heard with the proper equipment. Then, the question of how to tell which sounds are indicative of cavitations — and therefore early warning signs of drought stress — was a bit of a doozy.
Until now. A team of scientists from Grenoble University, Saint-Martin-d’Hères in France, led by physicist Alexandre Ponomarenko, presented a study at last month’s meeting of the American Physical Society that seems to hold the promise of a day when what is now lost in translation could be found. Using a gel capsule-like device developed by Cornell University’s Dr. Abraham Stroock, the scientists were able to take a peek inside a simulated tree and observe the cavitations and other activity at the same time sounds were being recording. Cross referencing the visual and audio data, they were able to distinguish the sounds that corresponded with cavitations from other sounds, such as fractures in the wood.