Mycelium is the vegetative part of a fungus. Photo courtesy of Gwen Balogh 

Ken Springer
Watoga Trail Foundation

Talking Trees
The Wood Wide Web

In the early 1990s, there was a popular comedy series on TV called Northern Exposure. It was set in Alaska in a fictional town named Cicely; the citizens of which, were a true cast of characters. On one episode, called Dateline Cicely, the headlines of the Cicely News and World Tele- gram proclaimed: “Amazing Find in the Tundra, Trees That Talk.”

In the program, only those who believed it possible could actually hear the trees talking. In the age of science, most of us would not take such a notion too seriously, but this case may be a rare instance where science is catching up with fiction.

Researchers have uncovered some interesting facts over the last couple of decades that has them taking a fresh look at communication between plants. It turns out that trees do communicate by way of an underground network. Not only do they, but the health of individual trees and much of the forest ecosystem is dependent upon this fascinating system.

Suzanne Simard, Professor of Forest Ecology at the University of British Columbia, first realized the extent of this “underground economy” when she set up an experiment in a forest of birch, cedar and fir trees. She already knew that if either species failed due to lack of sunlight, disease or infestation, then it negatively affected the other species.

To prove that trees are actually messaging with other trees, she bagged a Douglas Fir sapling and injected a radioactive gas into the sealed plastic bag. Then, using a Geiger counter she checked other trees in the vicinity. What she found was astounding – in short order, the neighboring trees, including birch and cedars, started setting off the Geiger counter. In all, this one tree was communicating with a total of 47 other trees, even those of other species.

So, we know that the root systems of trees alone cannot account for this network of communication; they just don’t extend that far nor are they efficient in the uptake of nutrients and minerals. The facilitator of this activity is something that is so small that just a pinch of forest soil can contain up to seven miles of the microscopic cable that connects trees together. We are talking about the vast and strange world of mycelium, or as it is more commonly known – fungi.

Fungi are usually considered more animal than plant. They do not photosynthesize, so carbon-based sugars must be obtained through other strategies. We see the fruit of the mycelium frequently and they make up the often bizarre world of mushrooms.

Mycelium is a network of fine white filaments. They are actually hollow tubes capable of transporting nutrients, water and chemical signals. Some mycelium form relationships with trees in a symbiotic fashion, exchanging minerals needed by the trees for carbohydrates that are then consumed by the fungi. But they appear to go much further than just an even exchange.

We are taught that it is a “dog eat dog” world in nature and, even in the forest, trees strive to create as great a canopy as possible, maximizing their own photosynthesis. And in doing so they block the sun from other trees, thereby slowing their growth. This, of course, is true to a certain extent. But by only examining the surface, we don’t see what is actually going on underground.

What researchers find when they do peer into this subterranean world is a complex network of trees giving, taking, and even loaning, needed nutrients. Mycelium will transport carbohydrates and minerals from a healthy tree to one that is struggling to survive.

If one tree is under attack from a pest or parasite it will send chemical signals to other trees via the mycelium to warn them of the impending danger.

Pardon my momentary lapse into anthropomorphism, but it all sounds a bit like altruism – doing something at one’s own expense for the greater good?

If I said that mycelium can perform all of these functions because they hunt, fish and mine minerals, you may think that I have crossed that fine line of believability, but, please, read on a bit further.

Trees require much more in the way of minerals than their root systems can provide. In fact, without the added support of the fungi in breaking down and providing minerals, trees would not have sufficient rigidity to grow beyond the height of a tulip. Mycelium actually works its way into stones by secreting acid to create tiny tunnels, in effect, mining the minerals that are then sent on to the trees.

In still another strategy for providing nitrogen to trees, mycelium will hunt for tiny creatures called springtails that are abundant in the forest soil. As the thread of mycelium makes its way through the soil it encounters these flea-sized insects and, after immobilizing them, will invade the body, often while the springtail is still alive. The mycelium then extracts the nutrients and sends them where they are needed.

During DNA research on trees in the coastal areas of British Columbia and the U.S. Northwest, researchers discovered that the growth rings contained DNA from salmon. It turns out that the source of this salmon DNA was once again our friend, the fungi.

The salmon is choice food for bears and when they are running upriver and plentiful, the bears take a choice bite and drop the rest of the salmon to the ground. When the salmon carcasses are inevitably broken down by the elements and other scavengers, the remainder works its way into the forest duff. From this point, the remaining residue of the fish is absorbed by the mycelium and transported to trees.

Fungi have played a larger role in the development of our modern forests than we might think. The amazing relationship between fungi and plants began in the late Ordovician era over 400 million years ago. 

Fossil evidence shows a symbiotic relationship of fungi with early mosses and liverworts and other non-vascular terrestrial plants. This would set the stage for the success of the larger vascular plants such as trees.

So, maybe we should stop thinking of the forest as a large area with a lot of individual trees, but rather, one large and complex eco-system with an emphasis on the good of the entire system.

Amazingly, when the forest’s underground system is mapped, it has a striking resemblance to the neural pathways of the human brain. Not only the brain but the internet and even the universe.

Perhaps there is a common design to nature, all of nature.

We may one day find out that our entire universe and all that it holds, is but one interdependent organism.

Happy Hiking,
Ken Springer

A special thanks to the folks of Radio Lab, an NPR program who strive to make science accessible to broad audiences; and to the CBC program The Nature of Things; How Fungi Made our World.