No man is an island unto himself, poets, philosophers, and teachers down through the ages have emphasized, and the same, it would seem, can also be said of trees. It is now understood that roots of trees in the wild are interconnected by extensive and complex “common mycorrhizal networks” of fungi—what researchers sometimes refer to as the “wood wide web.”
When connected to this internet of fungal threads, known as mycelium, trees and other plants are able to communicate, help their neighbors by sharing nutrients, or even sabotage unwelcome plants by spreading toxic chemicals. This partnership of plants and fungi, which is especially prevalent in old-growth forests, is symbiotic in nature, with the trees providing carbohydrates to the fungi, which in turn gathers water and nutrients such as phosphorus and nitrogen for its benefactors. An estimated 90 per cent of land plants participate in this mutually beneficial relationship.
“These fungal networks make communication between plants, including those of different species, faster, and more effective,” according to chemical ecologist Dr. Kathryn Morris of Xavier University. “We don’t think about it because we can usually only see what is above ground. But most of the plants you can see are connected below ground, not directly through their roots but via their mycelial connections.” (BBC)
Large older trees, known as “mother trees,” naturally have more extensive root networks and more connections than smaller trees and as such play a key role in supporting other trees in the forest, especially their own offspring. “If you’re a mother and you have children, you recognize your children and you treat them in certain ways, says Dr. Suzanne Simard, a forest ecologist from the University of British Colombia. “We’re finding that trees will do the same thing. They’ll adjust their competitive behavior to make room for their own kin and they send those signals through mycorrhizal networks.” (ABC Science)
Recent research shows that when a mother tree is felled, the survival rate of seedlings tends to decline dramatically, while attempts to regenerate forests without mother trees are often unsuccessful. The cooperative fungal network also connects trees of different species in the same native community, which use the network to share rather than compete for resources, says Simard. In an experiment published in the journal Nature, she used radioisotopes to trace the movement of carbon, nitrogen, and water between a Douglas fir and a paper birch. When she shaded one tree, carbon-based sugars would flow into it from the other. Simard believes that many seedlings would be unable to survive were it not for the lifeline this network provides.
A former forest ranger who has worked with trees since 1987, Peter Wohlleben, best-selling author of The Hidden Life of Trees: What They Feel, How They Communicate — Discoveries From a Secret World, chooses to interpret this interconnectedness in very human terms. “[Trees] can count, learn, and remember; nurse sick neighbors; warn each other of danger . . . and, for reasons unknown, keep the ancient stumps of long-felled companions alive for centuries by feeding them a sugar solution through their roots,” he says. (Treehugger)
“These trees are friends,” Wohlleben says in an interview with The New York Times, indicating a pair of towering beeches. “You see how the thick branches point away from each other? That’s so they don’t block their buddy’s light.” He adds: “Sometimes, pairs like this are so interconnected at the roots that when one tree dies, the other one dies, too.”
Studies also indicate that trees use the networks to warn their neighbors about attacking pests. “When trees are attacked, they increase their defense against the invaders by up-regulating their defense genes to make defense enzymes,” says Simard. “Research suggests they also send chemical signals down into their roots through their mycorrhizal networks to their neighbors, which then detect these signals and up-regulate their own defense genes.” (ABC Science)
The symbiotic nature of this relationship between tree and fungi serves as a ready example of what science, philosophy, and spiritual traditions have each long sought to express in their own ways—of the interconnectedness and interdependence of apparently separate organisms that is inherent at the environmental level, the societal level, and indeed within all natural systems.