Spring begins a new symphony of sounds. Bird calls amplify. Thawed-out amphibians scream. Flying insects buzz by. Humans begin to spend more time in the growing sunlight. With all this noise above ground, it’s hard to remember that there’s a lot going on below our feet.
Like other creatures, trees also call out to others of their species. Wait — trees can’t talk! With no mouth, vocal cords or even a brain like ours, how are they communicating?
The simple answer: using fungi.
Wood wide web
Have you ever played the telephone game? It’s the game where one person whispers a phrase to the person next to them and then that person whispers what they heard to the next person and then so on down the line. Trees are playing the same game, except fungi are delivering the messages.
Different species of fungi often grow around tree roots. Sometimes we see them grow above ground. But even if their weird-shaped and colorful mushrooms are not visible to us, they’re still underground. Similar to plant roots, fungi grow thin threads called hyphae. A group of these thin threads together are called the mycelium. As fungi grow, the mycelium grows and spreads out, linking to different tree roots. Once connected, the fungi and trees form what is called a mycorrhizal network.
Through this network, trees can send chemical or electrical signals to other trees, just like the telephone game. While the trees aren’t talking with mouths, they are not standing silent!
Signals and sugars
Think of summertime, when mosquitos are out. They might be landing on you, looking for a snack. Most likely you share your observation so others can protect themselves from getting mosquito bites as well. Trees do that too.
Words to know
Amplify: To increase the volume of or to become more intense.
Discourage: To cause someone to lose confidence or enthusiasm.
Matriarch: A woman who is the head of a family or tribe.
Symbiotic: Denoting a mutually beneficial relationship between different living things or groups.
Some insects, like beetles, like to burrow into tree bark. What looks like a nice home to a beetle might feel like danger to a growing tree. The tree can send a signal to nearby trees warning of danger. The neighbor tree could start to produce toxins to discourage any predatory bugs.
Trees can also send nutrients to other trees through fungi.
You might be wondering: Do the fungi get anything for their role in this network? They do! Trees pass along sugars from photosynthesis to the fungi. In addition to their messenger duties, the fungi also share mineral nutrients (nitrogen and phosphorus) from the soil.
This mutual give-and-take relationship is called a symbiotic relationship, and examples of this can be found all around in nature! Another example is bees and flowers. Bees visit flowers in search of food. As they visit the flowers, pollen sticks to the bee and gets transferred to another flower, pollinating the plant! Learn more about pollination.
While the mycorrhizal network links trees and fungi, plants also tap in for food or to send toxins.
Family trees
Forests are made of different species of trees but also trees of different ages. Older trees reach up to the open canopy and younger trees fight for sunlight below. Some of the oldest, largest trees in the forest are the most connected. These are called “hub trees” or “mother trees.”
Think of these mother trees like women in your family. Family matriarchs are often the mothers, grandmothers or great-grandmothers in the family, providing love, guidance and those cherished family recipes to younger generations.
The same thing happens in the forest. Seedlings cannot reach the same amount of sunlight that tall trees do, so mother trees will send down nutrients through their trunks and the mycorrhizal network to her seedlings nearby. This is just like a parent handing a top-shelf cookie over to a small child with outstretched hands.
Over the years, family matriarchs make strong connections outside of the family — childhood friends, work acquaintances and neighbors down the street. Mother trees tend to do the same; there are relationships between different species of trees that communicate with each other and send nutrients when the others need it.
Finally, even at the end of their lives, trees continue to give. When a tree knows it is dying, it will pass on its stored carbon to seedlings and neighbors. When you walk through a forest and see a tree stump, it’s tempting to think of that tree as dead. While it is no longer growing, it is still passing on nutrients. And sometimes, neighbor trees still pass on nutrients to the stump. That’s why seedlings, plants and fungi still attach to those stumps!
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