They are forever rooted to the same place, have no eyes, ears or mouths, yet trees may still have better social lives than we do. It may sound bizarre, and even a little depressing, but research suggests that it could well be true.
Many poets have written of the tranquility that can be found in a forest. Birds and insects may punctuate the serenity from time to time, but there is a peaceful silence to be found in the company of trees. Little do people know, there is a right old chinwag going on beneath the soil.
Trees are anything but the lonesome giants we perceive them as. They actively converse, nurture their young, and make sacrifices to help fellow strugglers. Connected via an underground network, they are constantly communicating and cooperating with one another.
Professor Suzanne Simard has a long held fascination with this phenomenon, but found it difficult to gain research funding 25 years ago. Many were sceptical of the idea, whilst some just thought she was plain crazy.
Using limited resources, Simard ventured deep into the Canadian forests to conduct experiments in the wild. She grew 80 replicates of three species: paper birch, Douglas fir, and western red cedar. Her theory was that the birch and fir would be connected via this underground network, but not the cedar.
Simard had to contend with grizzly bears chasing her away, and apparatus that ranged from duct tape to syringes full of radioactive gas, but she proved her theories were correct. By placing plastic bags over the young trees and injecting isotopic tracers, she was able to use a Geiger counter to follow the carbon moving between her specimens.
Simard found that the paper birch and Douglas fir were in a “lively two way conversation”. One would send more carbon to the other when they were in need, such as when one was leafless or in shade.
“I knew that I had found something big,” says Simard, “something that would change the way we look at how trees interact in forests, from not just competitors but to cooperators. And I had found solid evidence of this massive below ground communications network, the other world.
It was not only carbon that was being transmitted, but also nitrogen, phosphorus, water, defence signals, chemicals and hormones. What allows the plants to communicate this information is an underground mutualistic symbiosis called a mycorrhiza.
This symbiotic association occurs between a fungus and the roots of a plant. The mushrooms you see scattered across the forest floor are the reproductive organs of this fungus. But, beneath the soil, a mass of fungal threads branch off in all directions to form a mycelium. It is so dense, there could be hundreds of kilometres under a single footstep.
Simard explains that, “mycelium infects and colonises the roots of all the trees and plants. And where the fungal cells interact with the root cells, there’s a trade of carbon for nutrients.”
Paul Stamets, an American mycologist who studies fungi, first proposed in the early nineties “that mycelium is the Earth’s natural Internet”. Simard’s research has found that the mycorrhizal networks have nodes and links like a communication network, and she has been able to map these out using the DNA sequences of trees and fungi.
Simard refers to the hub trees as ‘mother trees’, because they nurture the young growing in the understory. They can be connected to hundreds of other trees within a single forest and are the cornerstones of a healthy and vibrant network. Simard believes that if too many are removed, then the whole system could collapse.
These mother trees have been found to not only recognise their own young, but to show them preferential treatment, giving them extra space by reducing root competition. Messages of wisdom will also be sent when a mother tree is injured or dying, in the form of defence signals that can increase a seedling’s resistance to future stresses.
Simard now hopes that these little known revelations will help change the way we understand and manage our forests. Trees have been using their underground networks to communicate and cooperate with one another for untold years. We may marvel at our Internet, but theirs serves an egalitarian purpose. Ours on the other hand, is mainly used to watch hilarious memes.