Photo Credit: Mycelium 1 – “Mycelium” by Bushman.K is licensed under CC BY-NC 2.0.
Imagine you are walking through a quiet, lodgepole pine forest. The forest floor may look calm, but beneath the surface there is an entire network of activity occurring. Now, I am not just talking about the roots of the many trees around you, but something we call mycelium. Mycelium is essentially the “roots” of fungus. It can appear threadlike in texture, and it is made up of a network of “hyphae”. Hyphae is the vegetative structure of a fungus, different from the “fruiting body” often associated with mushrooms (the part of fungi we see most often). Networks of hyphae, in the form of mycelium, give fungus the ability to branch out and locate food sources to decompose. But, did you know that this special structure creates a network between many other organisms and the fungi itself? Mycelium actually plays a very important role in
ecosystems.
Mycelium is able to branch off beneath soil in search of food, and can grow to immense sizes. These structures are able to decompose organic matter by releasing enzymes and absorbing nutrients. It is argued that some of Earth’s largest organisms are mycelial growths of individual fungi. The “humongous fungus”, located in Oregon, is a single, oyster mushroom individual, whose mycelial network spans over 2,300 acres! These structures can be widespread, setting the basis for “nature’s network”.
Photo Credit: Diagram – “Mutualistic mycorrhiza en” by Nefronus is licensed under CC BY-SA 4.0.
Mycelium sets the groundwork for what are called “mycorrhizal networks”. Mycorrhizae is the symbiotic relationship between the mycelium and the roots of plants. In other words, mycorrhizae is the result of a fungus mycelium and a plant working together. What exactly does this relationship entail? Mycorrhizae are vital for the exchange of nutrients and water within the forest ecosystem. An important example of this exchange is phosphorus and sugar transfers. Fungi take up phosphorus from the environment, and in turn “trade” it with the trees through mycorrhizae connections for sugar molecules to be used as nutrients. Similarly, this exchange can sequester carbon. Carbon absorbed by trees can be transferred with fungi in return for important mineral nutrients. Up to 30% of the carbon sequestered by trees is used in this exchange!
Mycorrhizal connections can also be used as a way for plants to communicate with one another. It’s almost like the mycelium can act as an organic telephone line! Plants are capable of sending chemical signals via mycelium to one another to preemptively warn other plants of attack. A great example within the SNRA would be Blue Flax (Linum lewisii). Blue Flax is able to produce chemical signals that attract wasps and other predatory insects to the plant to get rid of pests that may be damaging it. Studies have shown that in this circumstance, plants will send “infochemical” signals (as mycologist Merlin Sheldrake calls them) to other plants nearby through the mycorrhizal network, so they are able to preemptively put up these defensive mechanisms.
The role of mycelium goes beyond the ability to help plants communicate. It also aids in the distribution of resources between older and younger plants. Often, younger trees are shaded by older ones, reducing the ability for these plants to photosynthesize. Studies have shown that older trees will utilize mycorrhizal connections to distribute resources to younger trees when needed. Studies have even found that Douglas Fir trees will preferentially send nutrients to closely related individuals – talk about family ties!
Photo Credit: Forest – “beautifuly day in the lodgepole forest” by YellowstoneNPS is marked with Public Domain Mark 1.0.
Mycelium makes up the hidden world beneath our feet. It promotes growth for our forests and the agricultural lands we get our food from. It allows our favorite plants to thrive and grow stronger. Without mycorrhizal connections, who knows what our world would be like. Next time you are out for a walk, take a second to think about the interconnectedness of the world all around you, starting with the smallest fungi to the largest tree.
If you are interested in learning more about mycelium, mycorrhizal networks and the importance of fungi in our world: I got a lot of information (and inspiration) from reading Merlin Sheldrake’s book, Entangled Life: How Fungi Make Our Worlds, Change Our Minds & Shape Our Futures. Definitely check the book out if you are interested in learning more!
Bailey Cole is a 2025 Naturalist for SIHA. When she’s not working at the Redfish Visitor’s Center, she enjoys long hikes to alpine lakes and exploring hot springs in the Sawtooth National Recreation Area.