Pando is the popular name assigned to one of the most extraordinary living beings that can currently be observed on Earth. It looks like a more or less normal forest of trembling aspen (Populus tremuloides) but in reality, the scientists explain, it is a single tree that probably grew around 80,000 years ago and currently has 47,000 living shoots. Each of these shoots resembles an individual tree but, as has been found, they are genetically identical parts of a common organism intertwined underground.
This great symbol of the permanence of life on our planet is now in the news due to the presentation at the 184th meeting (congress) of the Acoustic Society of America, which is being held this week in Chicago, of Pando's first sound atlas, generated with help of microphones and hydrophones installed in the trunks and roots of this unique tree.
“Pando challenges our basic understanding of the world,” recalls Jeff Rice, a sound expert who made the recordings with Lance Oditt, founder in 2019 of the nonprofit organization Friends of Pando. The first recordings of Pando sounds (leaves, atmosphere after a storm...) were broadcast in 2018 in The New York Times Magazine. In 2022, Rice returned to Pando to expand the work with the help of more sophisticated recording equipment. .
Friends of Pando has created and maintains a magnificent website where, for example, you can see more than a dozen 360-degree interactive images of various parts of the interior of the set of shoots that make up Pando. With these images it is possible to simulate a walk through the interior of this set of shoots that look like a large grove of trees.
Despite the quality of this website, it has not yet (May 10) incorporated the recordings presented this week in Chicago, which can be heard on pages like NPR, for example, the one about its vibrations. In Apple Music you can also listen to an ambient sound cut of this tree-forest and some of its inhabitants (birds).
“Sounds are beautiful and interesting, but from a practical standpoint, natural sounds can be used to document the health of an environment,” Jeff Rice has noted. “They are a record of local biodiversity and provide a measurable baseline against environmental change.”
Rice was particularly captivated by the sound of vibrations passing through the tree during a wind storm. He wanted to see if they could record the sound of the Pando root system, which according to some accounts can reach depths of 27 meters. Oditt, executive director of Friends of Pando, identified several potential recording locations below the surface.
“Hydrophones don't just need water to work,” Rice said. “They can also pick up vibrations from surfaces like roots, and when I put the headphones on, I was instantly amazed. Something was up. There was a faint sound."
That sound is inconclusive of Pando's root system. But a handful of experiments support the idea. Rice and Oditt were able to show that vibrations can pass from one tree to another through the ground. When they hit a branch 27 meters away, the hydrophone registered a low blow. Rice likens this to the classic tin can phone.
“It's similar to two cans connected by a string,” he said. “Except there are 47,000 cans connected by a huge root system,” Rice and Oddit explain.
A similar phenomenon occurred during a thunderstorm. As the leaves moved more strongly in the wind, the signal recorded by the hydrophone also increased.
“The findings are enticing. While it started as art, we see enormous potential for its use in science. Wind, converted into vibration (sound) and traveling through the root system, could also reveal the inner workings of Pando's vast hidden hydraulic system in a non-destructive way."
Friends of Pando plans to use the collected data "as the basis for further studies on water movement, how branch arrays are related to each other, insect colonies, and root depths, all of which we know little about today." , explains Lance Oditt.