The ecologist Suzanne Simard has spent over 30 years studying the Canadian forests making an incredible discovery: the trees talk to each other through a real underground communications network that extends over long distances
A forest is much more than what you see - says Suzanne Simard, ecologist who has been studying for a living Canadian forests. Under the surface there is another world, made of endless biological pathways through which the trees are connected to each other and communicate, acting as parts of a single great organism.
25 years ago, the first experiments of Simard is concetrarono on three species: the paper birch, Douglas fir and red cedar Pacific. Using of radioactive carbon isotopes to track the carbon displacement between the various plants, he noted as birch and spruce actively communicated with each other, while the cedar stood apart.
In summer, birch fir sent more carbon than this it would send the birch, especially when the spruce stood in the shade. But at other times of the year it was rather fir to send more carbon birch, when this was not the leaves. So the two species they helped one another, overturning the idea that plants of a forest were competing, showing that instead collaborate with each other.
As communicated birch and spruce? Their interaction took place not only on the carbon floor, but also nitrogen, phosphorus, water, defense signals, allelochemicals compounds and hormones. Already other scientists had figured out how this communication could be behind the mycorrhiza, the symbiotic association between a fungus and the roots of a plant.
When we see the mushrooms, we only see the tip of the iceberg. Below them branching fungal filaments that form the mycelium, which infects and colonizes the roots of all the plants and alberi.Quando fungal cells interact with those radicals occurs a carbon exchange and nutrients. The network is so dense that there may be hundreds of kilometers of mycelium in a few steps. In practice, the mycelium connects different individuals in the forest, not just the same species but of different species, just as the spruce and birch: works much like the Internet.
Costrunedo map of a part of the Canadian forest, Simard has identified how the various Douglas firs were connected to each other via the fungal links. He also found that there are the "hub trees" or "mother trees" that represent major nodes of the communication network: these trees are those that nurture the younger plants, which grow in the undergrowth.
In fact, a mother tree can be connected to hundreds of other trees. Every tree mother sends its surplus carbon through the mycorrhizal network, the younger plants found in the underbrush, reaching even to limit the extent of their roots to make them more space. Thanks to that young trees are four times more likely to survive.
In addition, when the mother trees are injured or die, they send the "wisdom messages" to subsequent generations of seedlings that are growing all around. In fact, tracing the carbon displacement and other signals - traveling from one mother tree wounded, from its trunk until the mycorrhizal network, and from there reaches the neighboring seedlings - it was discovered that the dying plant gives useful indications that instruct the young plants on how to cope better in the future the same kind of stress.
The conclusion is that the forests are not simply a set of trees, are complex systems with hundreds of "hub trees" and networks that overlap with each other, putting in communication the various plant species, paving the way for the adaptation and feedback : all this makes the resilient forest.
However, the forest is also vulnerable, not only to natural disturbances, such as bark beetles that attack the older trees, but also to deforestation for commercial purposes. We can take one or two "hub trees", but there is a limit because the "hub trees" are like pins in a plane. We can take one or two, and the aircraft will continue to fly, but if you take too much, or if we take what keeps the wings in place, the whole system collapses.
In the video below Suzanne Simard tells his ricerce on stage Ted (video in English with subtitles in Italian):