6 minute read
The Secret Language of Trees
Dominika Front
You’re walking in a lush forest, admiring the spreading branches of tall trees. The birds are chirping, the sun is shining through the leaves, painting golden stripes on the forest floor. Yet while enjoying such a walk, few people would think that anything exciting is happening under the layer of branches, dead leaves, and ferns. You’d be quite surprised. Down below, a vast web of fungal hyphae stretches out, penetrating each square centimetre of soil and forming a channel for trees to communicate.
The fungal network grows around tree roots and penetrates them, absorbing the excess sugars that the tree obtained during photosynthesis. The sugars are indispensable for the survival of the fungi. In turn, the fungi provide the tree with nutrients from the soil, such as phosphorus and nitrogen. In other words – a win-win type of situation. This process is called mycorrhizas, a symbiosis between a plant and a fungus.
Fungi branch out their hyphae so that they collectively make up the mycelium – the fungus’s body. Not only does this complex root system allow the tree and fungus to get what they need, but it also connects the tree roots together forming mycorrhizal networks, such as the common mycelial network (CMN). According to a global project by the Society for the Protection of Underground Networks (SPUN):
“A single gram of soil can contain up to 90 meters of mycelium. The total length of mycorrhizal mycelium in the top ten centimeters of soil is around 450 quadrillion kilometers: around half the width of our galaxy.”
The complexity of the CMN does not end there. There are hundreds of species of mycorrhizal fungi; there are roughly 3 trillion trees on our planet and each tree can cooperate with dozens of fungi. These results in unique connections between individual trees and their own set of fungi. Together, they make up the CMN or, as it was dubbed by Nature in 1997, the Wood Wide Web. This name is a perfect fit for two reasons. First, it coincided with the dissemination of the Internet; second, there is a parallel between the CMN and the Internet (but more or that later).
In the 1980s, the CMN was tested in vitro but it was not until a decade later that a Canadian scholar, Suzanne Simard, started to work on her PhD which would investigate the CMN (which, if you’re interested, you can read here). When she was a student, it had only just been discovered in lab tests that one prime root could transmit carbon to another prime seedling root, so in her thesis she decided to investigate whether the same transfer takes place in forests as well. After some funding problems – the part and parcel of academia – she conducted an experiment by means of which she found out that paper birch and Douglas fir trees use the mycelial network to send carbon to each other. Her further work revealed that the trees and other plants communicate on a far deeper level, sharing not only carbon, but also the nutrients and information crucial to their survival.
Now, Suzanne Simard is a professor of forest ecology at the University of British Columbia. She also started The Mother Tree Project – a research project “investigating forest renewal practices that will protect biodiversity, carbon storage and forest regeneration as climate changes” (to learn more about the project, visit its website). Alongside other scholars, she was able to create a DNA map of the mycorrhizal network of Douglas fir trees in a Douglas fir forest. It was a huge breakthrough for the world of science. However, it was nothing compared to the discoveries by Crowtherlab, which does research on ecosystems, their structure and their global variety. They were able to build on Simard’s findings and use machine learning to create the world map of the Wood Wide Web. This impressive feat allowed for a better understanding of how ecosystems work. But more importantly, this development can help us understand how ecosystems work. This, in turn, will allow the scientists to research and, hopefully, find ways of mitigating the effects of logging on climate. How? As described, mycorrhizal network transports carbon, among all other things.
When a tree dies – be it naturally or not – gigantic amounts of carbon from this network get released into the atmosphere. Simard and other Mother Tree Project researchers are now able to use that knowledge and translate it into guidelines on how to conserve what they call mother trees, which play a vital role in protecting fungal networks that store millions of tonnes of carbon.
Why mother trees, though? It turned out that there is a pattern in the bonds between trees. The network consists of nodes and links – and it’s mind-blowing since it is comparable to neural networks on which the brain – or the Internet – is based. The nodes in the network are called hubs, or more tenderly, mothers, who use the Wood Wide Web to sustain younger trees by dispatching nutrients. They are usually connected with hundreds of other trees, as a result increasing the seedlings’ survival. Of course, this is just a metaphor used to help us picture the complexity of the connections, not to anthropomorphise plants and fungi. It’s a pretty accurate metaphor though because one can’t help but notice the parallels.
We know how the trees are interconnected. But why would the fungi transport the nutrients to neighbouring trees, send information, and pose as a channel of communication for the plants? Are the fungi being blackmailed by their mycorrhizal partners? Or maybe quite the opposite, does it benefit the fungi somehow? We don’t know the answer. What we do know, however, is the complexity of the CMN. Trees can tell where the nutrients came from; what’s more, they can even tell if the substances were sent by their close relative! They also share information on such dangers as droughts or insects, causing their neighbours to strengthen their security systems. And the most touching element of their cooperation is that a dying tree sends food to other trees so that the nutrients won’t be wasted but will nurture others. And now something amazing – the mother tree recognises its offspring and envelops it with a bigger mycorrhizal mesh, sending more carbon and nutrients; they give up on their own roots so as to provide space to their seedlings. Thanks to that, these seedlings become stronger and less susceptible to diseases that could overcome the mother tree.
The Wood Wide Web, just like the Internet, has its grim side, too. Some plants plug into the Wood Wide Web by force, using the Wood Wide Web as a darknet, really. By doing so, they can steal resources from the neighbouring trees and plants, or, like alders and walnuts, spread toxins to finish off their foes.
Next time you’re in a forest, look out for mother trees. Think not only about what you see before your eyes, but instead envisage the galaxy of connections under your feet. And maybe, if you’re pertinacious enough, you’ll discern the secret conversations of trees.
