Talk Leafy to Me: Tree Communication
Think about the last time you were in a forest - it might have been a bright, sunny day, or the mood may have been dim and damp. Regardless, you probably experienced a sense of peace and quiet while you were there. But did you know that there was communication happening all around you?
Forest ecologist Suzanne Simard and others like her have been researching the communication connections between trees and other plants. While some critics say Simard is engaging in anthropomorphization (the ascribing of human attributes like emotions and intentions to non-human organisms), very little fault should be found with the use of the term "communication." After all, communication is simply the transfer of information. And in a forest, it turns out, a lot of information is being sent back and forth.
How do trees communicate? It's all about being connected. The connections between trees can stretch for astounding distances, and just like fiber optic cables, they run under the ground. Trees and many other plants have a special relationship with mycorrhizae, which are fungi that form networks with plant roots. These are often symbiotic relationships, just like the relationship between fungi and algae that create lichens.
Mycorrhizal networks are composed of the mycelia (bodies) of fungi that look like mats of incredibly thin white hairs. That's right - a mushroom isn't the body of a fungus, but only the reproductive organ!
Anyway, these thin white filaments grow throughout the soil. The symbiotic relationship comes into play because fungi are unable to create their own sugars for food, so they receive sugars from the roots of their partner trees. In return, the mycorrhizae contribute minerals and other nutrients from the soil back to the trees.
The mycorrhizae can be connected to more than one tree, though, so the fungal webs beneath the soil in a forest could conceivably connect all of the trees. And this is how the communication is achieved. Simard's research has identified "hub trees," usually some of the largest and oldest in a forest. Because these hub trees are so old, they have the most mycorrhizal connections to other trees. Through these connections, hub trees are able to send sugar and water to younger, smaller trees that are struggling to survive. There is also some evidence that the root tips of these trees can "recognize" the root tips of trees that are genetically related to them, so they might preferentially send nutrients to their "kin." The important role hub trees seem to play in the dynamics of a forest ecosystem means that Simard and other researchers recommend identifying and protecting hub trees from logging harvests.
It's important to remember, though, that when there's sharing going on in nature, some organism will usually figure out how to exploit the system. Indian pipes and other parasitic (non-photosynthetic) plants can also tap into the mycorrhizal network and "steal" nutrients from the trees above them.
Trees and plants can communicate through the air, too. If a plant is being attacked by an herbivore, it may release chemicals into the air. When other plants sense these chemicals, they will often boost the production of chemicals within their own systems that help protect them from herbivores. This "warning system" is demonstrated well by the example of giraffes and acacia trees, where the acacias downwind will increase their production of tannins (which can make giraffes and other herbivores sick). Many plants will also engage in this behavior when attacked by aphids and other insect pests.
But we're trying not to inappropriately assign intent or awareness to plants without any proof. There's no way for us to be sure that this release of chemicals is actually a warning system - that would require proof of intent and even altruism. However the alternative - that these chemicals are just distress signals - leaves us wondering what the evolutionary point of such chemicals would be. Why signal stress if no other organisms are intended to "hear" it? Why waste the resources needed to create those distress signals?
While we don't yet know why these chemical signals are released, we can measure their effects, like the increase in tannin production. And other animals have learned this "language of plants," too. When certain plants are being eaten by caterpillars, they will release a subset of these distress chemicals. The chemicals are detected by parasitoid wasps. These wasps are incredibly tiny, and they lay their eggs directly inside the caterpillars' bodies, so the caterpillars are then eaten from the inside-out by the baby wasps. Maybe the plants are calling for help? Maybe the wasps are just taking advantage of distress chemicals?
While we may never be able to say with certainty how much intelligence plants have or whether this communication occurs with intent, we can demonstrate that the communication is occurring. And I don't know about you, but I will never think of the forest as "quiet" again!
Forest ecologist Suzanne Simard and others like her have been researching the communication connections between trees and other plants. While some critics say Simard is engaging in anthropomorphization (the ascribing of human attributes like emotions and intentions to non-human organisms), very little fault should be found with the use of the term "communication." After all, communication is simply the transfer of information. And in a forest, it turns out, a lot of information is being sent back and forth.
How do trees communicate? It's all about being connected. The connections between trees can stretch for astounding distances, and just like fiber optic cables, they run under the ground. Trees and many other plants have a special relationship with mycorrhizae, which are fungi that form networks with plant roots. These are often symbiotic relationships, just like the relationship between fungi and algae that create lichens.
Mycorrhizal networks are composed of the mycelia (bodies) of fungi that look like mats of incredibly thin white hairs. That's right - a mushroom isn't the body of a fungus, but only the reproductive organ!
Anyway, these thin white filaments grow throughout the soil. The symbiotic relationship comes into play because fungi are unable to create their own sugars for food, so they receive sugars from the roots of their partner trees. In return, the mycorrhizae contribute minerals and other nutrients from the soil back to the trees.
The mycorrhizae can be connected to more than one tree, though, so the fungal webs beneath the soil in a forest could conceivably connect all of the trees. And this is how the communication is achieved. Simard's research has identified "hub trees," usually some of the largest and oldest in a forest. Because these hub trees are so old, they have the most mycorrhizal connections to other trees. Through these connections, hub trees are able to send sugar and water to younger, smaller trees that are struggling to survive. There is also some evidence that the root tips of these trees can "recognize" the root tips of trees that are genetically related to them, so they might preferentially send nutrients to their "kin." The important role hub trees seem to play in the dynamics of a forest ecosystem means that Simard and other researchers recommend identifying and protecting hub trees from logging harvests.
It's important to remember, though, that when there's sharing going on in nature, some organism will usually figure out how to exploit the system. Indian pipes and other parasitic (non-photosynthetic) plants can also tap into the mycorrhizal network and "steal" nutrients from the trees above them.
Trees and plants can communicate through the air, too. If a plant is being attacked by an herbivore, it may release chemicals into the air. When other plants sense these chemicals, they will often boost the production of chemicals within their own systems that help protect them from herbivores. This "warning system" is demonstrated well by the example of giraffes and acacia trees, where the acacias downwind will increase their production of tannins (which can make giraffes and other herbivores sick). Many plants will also engage in this behavior when attacked by aphids and other insect pests.
But we're trying not to inappropriately assign intent or awareness to plants without any proof. There's no way for us to be sure that this release of chemicals is actually a warning system - that would require proof of intent and even altruism. However the alternative - that these chemicals are just distress signals - leaves us wondering what the evolutionary point of such chemicals would be. Why signal stress if no other organisms are intended to "hear" it? Why waste the resources needed to create those distress signals?
While we don't yet know why these chemical signals are released, we can measure their effects, like the increase in tannin production. And other animals have learned this "language of plants," too. When certain plants are being eaten by caterpillars, they will release a subset of these distress chemicals. The chemicals are detected by parasitoid wasps. These wasps are incredibly tiny, and they lay their eggs directly inside the caterpillars' bodies, so the caterpillars are then eaten from the inside-out by the baby wasps. Maybe the plants are calling for help? Maybe the wasps are just taking advantage of distress chemicals?
While we may never be able to say with certainty how much intelligence plants have or whether this communication occurs with intent, we can demonstrate that the communication is occurring. And I don't know about you, but I will never think of the forest as "quiet" again!
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