Before Simard and her colleagues did their work, scientists had thought that this belowground mutualistic symbiosis called a mycorrhiza was involved. Mycorrhiza literally means “fungus root.” You see their reproductive organs when you walk through the forest. They include things like mushrooms. However, the mushrooms are really just the visible result. Underground are networks of fungal threads that form a mycelium that infects and colonizes the roots of all the trees and plants in the ecosystem. Where the fungal cells interact with the root cells, there is a trade of carbon for nutrients. The fungus gets those nutrients by growing through the soil and coating every soil particle. The web that is created is so dense that there can be hundreds of kilometers of mycelium under a single footstep in the forest.
The mycelium connects different individuals in the forest to each other. In fact, that connection is not just between members of the same species but even between species. That is how different species such as birch and fir are connected. The analogy Simard and others have used is the Internet—an information highway. Underneath the ground of the forest there is a vibrant thriving interconnected ecosystem connected by means of the underground Internet. It is a truly remarkable discover.
Like all networks, the underground mycorrhizal networks have nodes and links. Simard made a map by examining the short sequences of DNA of every tree and every fungal individual in a patch of Douglas fir forest. With that she drew a picture with circles representing Douglas Fir. These are the nodes. The lines on the other hand represent the Douglas fir. The lines that interlink bodies on this underground information highway show how the interlinking fungal highways work.
The largest and darkest nodes are the busiest nodes. Simard calls those Hub trees or more colorfully Mother Trees. Her research demonstrated that the “Mother Trees…nurture their young, the ones growing in the understory.” Her map also showed yellow dots that represented young seedlings that have established themselves within the network of the old mother trees. In a single forest, a mother tree can be connected to hundreds of other trees. And using isotope tracers, Simard and her colleagues found that mother trees will send their excess carbon through the mycorrhizal network to the understory seedlings. Their research also shows that this “nurturing action by Mother Trees has increased seedling survival by four times.” That is a substantial benefit. It is well known that some species, such as humans for example and many others favor their own offspring. Simard wanted to know if Douglas fir did the same thing? Could they recognize and then help their own relatives? To determine that she devised an experiment where they grew mother trees with their own kin. And also stranger’s seedlings.
That experiment showed that the trees do recognize their kin. Mother trees colonize their kin with bigger mycorrhizal networks. They also send them more carbon below ground. They even reduce their own root competition to make growing room for their offspring.
Their research even showed that “when mother trees are injured or dying, they also send messages of wisdom on to the next generation of seedlings.”
Simard also used isotope tracing to trace carbon moving from an injured mother tree down her trunk into the mycorrhizal network and into her neighboring seedlings. They also discovered that besides carbon they sent out defense signals. And these two compounds have increased the resistance of those seedlings to future stresses. “So trees talk”. They not only talk to each other trees help each other. To some extent they embody Marx’s maxim, “from each according to his ability to each according to their needs.” Trees are Marxists! Trees have conversations that go back and forth. As Simard said, “Those conversations actually increase the resilience of the whole community. It probably reminds you of our own social communities, and our families, well, at least some families.” For example, trees share some characteristics of ant colonies.
As a result of all this data, Simard has reached the conclusion that forest are much more than collections of trees. Forests are “complex systems with hubs and networks that overlap and connect trees and allow them to communicate, and they provide avenues for feedbacks and adaptation, and this makes the forest resilient. That’s because there are many hub trees and many overlapping networks.”
Although all of this breeds resilience it cannot breed omnipotence. Trees in the forest ecosystem are also “vulnerable not only to natural disturbances like bark beetles that preferentially attack big old trees but high-grade logging and clear-cut logging.
It is always possible to take out a couple of hub trees out of a forest. It can survive such a disturbance. However, the more that is taken out of the complex forest system the more likely it is that eventually the system will collapse. The big question of course, is how close are our forests to collapse. Collapses can come suddenly and for many reasons.
When her talk was over Simard asked her audience if they were thinking about forests differently after this talk. Her audience said they were, so Simard was satisfied. She wants all of us to think differently about forests. I would say we should all have a different attitude to nature. That what I want too.