Educational Resources Lets Talk Science Challenge participants

 Looking up in a forest

Looking up in a forest (shazku, iStockPhoto)

STEM in Context

Talking Trees: How do Trees Communicate?

Beverly McClenaghan

Summary

Humans use the internet to communicate. Similarly, trees use a complex underground network of fungi. These relationships are examples of symbiosis.

Imagine a forest full of trees. Each tree stands tall and solitary. It has its own trunk, branches and leaves. But did you know that those trees are connected by a complex network hidden underground?

So what is this network made of? Fungi! Scientists believe almost all plant species worldwide are in relationships with fungi living in the soil. These fungi can connect the roots of different trees (and other plants) to create what’s called a mycorrhizal network.

A mycorrhizal network can influence the survival, growth, health, and behaviour of the trees linked within it. Trees use their network to do such things as communicate and share resources. That’s why some scientists call it the internet of trees, or the “wood wide web.”

How trees secretly talk to each other (2018) by BBC News (1:47 min.).

 

How does the fungal network work?

Many kinds of fungus have the majority of their bulk underground. In the soil, fungus grows in threads called hyphae. Together, all of these threads form a network called a mycelium. These threads can colonize (live among) the roots of trees and other plants.

Thin fungal hyphae (A) form branching mycelium networks (B)
Thin fungal hyphae (A) form branching mycelium networks (B) (Let’s Talk Science using an image by TheAlphaWolf [CC BY-SA 3.0] via Wikimedia Commons).

Fungal threads can interact with tree roots in two ways. In an ectomycorrhizal network, the fungal threads coat the root and the threads spread into the roots between cells. In an endomycorrhizal network, the fungal threads pierce the root and enter its cells.

Fungi and trees form a symbiotic relationship. Symbiosis is a close, long-term relationship between two organisms. Trees produce food, in the form of glucose sugars, through photosynthesis. The plants share this glucose with the fungus. Meanwhile, the fungus finds and absorbs nutrients from the soil to give back to the tree. Most of these nutrients are phosphates and nitrates. This type of symbiosis is called mutualistic symbiosis. That is because both of the species benefit from it.

Misconception Alert

Not all symbiosis is mutualistic! In commensalistic symbiosis, one species benefits but the other is not really affected. In parasitic symbiosis, one species benefits while the other is harmed!

Did you know?

Scientists think that about 90% of plant species form mycorrhizal relationships with fungi. 

How can trees share resources?

Fungi aren’t the only ones sharing resources with trees. Trees share resources with other trees, too! They use the fungal network to transport these nutrients. For example, tree seedlings (young plants) can’t grow as quickly in the shade of parent trees because they can’t get enough light for energy. Bigger trees can help them out by sharing nutrients via fungal threads.

Different species of trees can also share nutrients. For instance, several studies, such as this one, have focused on the connections between Douglas firs (a coniferous tree) and paper birch (a deciduous tree). In the spring and fall when birch are leafless, the Douglas fir is a stronger sink for carbon and nitrogen. But in the summer, when birch are taller and have a full foliage, they are a stronger sink for carbon and nitrogen. Through osmosis, nutrients from the tree with the higher concentrations will transfer to the trees with the lower concentrations. When it comes to Douglas fir and paper birch, this will happen based on the season!

However, some plants take advantage of the generosity of others without giving anything in return. For example, there are orchids that do not photosynthesize at all. Instead, they steal all their nutrients from nearby plants!

Did you know?

In North and South American, trees like Douglas fir and ponderosa pine are host to hundreds of ectomycorrhizal fungal species.

How can sharing resources help trees defend themselves?

Disease and insect infestations can spread quickly throughout a forest -- and they can be lethal for trees! Studies have found that trees can send help to their neighbours via the fungal network. For example, when a tree is attacked, it will release certain chemicals that travel through the fungal network and warn other trees of the danger. By having an early warning, other trees are able to protect themselves better.

The warning messages could prompt these trees to change their morphology (form and structures), physiology (functions) or biochemistry. For example, a plant could change its biochemistry by increasing levels of toxins and repellents in its tissues to deter pests. It could also change its biochemistry by producing airborne compounds that attract the natural enemies of a particular pest.

One study has found that certain stressed and dying trees can even pass resources, such as nitrogen and phosphorus, to their neighbours before they die. This gives the healthy trees that receive the extra resources a boost in combating the disease or outbreak.

How can sharing resources benefit trees of various ages?

Forests are made up of trees of different ages. The biggest, oldest trees are called mother trees. They are usually the trees that are the most connected in the fungal network. These mother trees nurture their offspring by providing them with the nutrients they need to prosper.

Mother tree by the side of the road
Mother tree by the side of the road (Source: Jim Smith via Wikimedia Commons).

On the flip side, trees can use the network to stop the growth of unwanted neighbours. Some trees release toxic chemicals into the fungal network to slow down the growth of plants competing for their resources.

How can the fungal network keep forests healthy?

Trees rely on their fungal network to communicate and gain knowledge just as much as we humans rely on the internet! A healthy forest is one that is well-connected by the “internet of trees” and has plenty of mother trees. This allows a forest to recover from random changes, like those caused by humans harvesting trees.

Scientists can use what they’ve learned about the “wood wide web” to help loggers make better decisions when harvesting trees. For example, for reasons you’ve read about, loggers should keep mother trees alive in the forest. And they should allow dying trees to release their nutrients before they remove them.

Next time you stroll through the woods, think of all the communication happening just beneath your feet!

How trees secretly talk to each other in the forest (2018) from National Geographic (3:41 min.).

 

 

Starting Points

Connecting and Relating
  • What methods of communicating do humans use that do not require speaking and listening? 
  • Before reading this article, did you think that plants could communicate with one another? Why or why not?
Connecting and Relating
  • What methods of communicating do humans use that do not require speaking and listening? 
  • Before reading this article, did you think that plants could communicate with one another? Why or why not?
Relating Science and Technology to Society and the Environment
  • Why might forestry and woodlot managers benefit from understanding how trees communicate? 
  • How could the forestry practice of clearcutting affect mycorrhizal networks and the health of forests? 
  • How could invasive species disrupt forest mycorrhizal networks?
  • How is an understanding of the science and benefits of mycorrhizal networks being extended to other commercial crops? Why is this a topic of interest?  (Note: This question will require additional research.)
Relating Science and Technology to Society and the Environment
  • Why might forestry and woodlot managers benefit from understanding how trees communicate? 
  • How could the forestry practice of clearcutting affect mycorrhizal networks and the health of forests? 
  • How could invasive species disrupt forest mycorrhizal networks?
  • How is an understanding of the science and benefits of mycorrhizal networks being extended to other commercial crops? Why is this a topic of interest?  (Note: This question will require additional research.)
Exploring Concepts
  • What is a mother tree? How can the health of a mother tree impact on the health of other trees in a forest? 
  • How do mycorrhizal networks work to create communication between trees? What are the benefits of a mycorrhizal network? 
  • What is a symbiotic relationship? Provide an example from the article.  
  • Why is biodiversity important for mycorrhizal networks in forests?
Exploring Concepts
  • What is a mother tree? How can the health of a mother tree impact on the health of other trees in a forest? 
  • How do mycorrhizal networks work to create communication between trees? What are the benefits of a mycorrhizal network? 
  • What is a symbiotic relationship? Provide an example from the article.  
  • Why is biodiversity important for mycorrhizal networks in forests?
Nature of Science/Nature of Technology
  • Knowing the function of mother trees within a forest environment, should there be legislation that protects these trees from being harvested?
Nature of Science/Nature of Technology
  • Knowing the function of mother trees within a forest environment, should there be legislation that protects these trees from being harvested?
Media Literacy
  • What movies or books can you recall that have trees that talk or communicate? (e.g., the Tree of Souls in the film Avatar) How did these trees communicate? What was their role in the story or narrative? Could any of these fictional trees be considered “Mother Trees”?
Media Literacy
  • What movies or books can you recall that have trees that talk or communicate? (e.g., the Tree of Souls in the film Avatar) How did these trees communicate? What was their role in the story or narrative? Could any of these fictional trees be considered “Mother Trees”?
Teaching Suggestions
  • This article and embedded videos can be used in Biology for teaching and learning related to forests & forestry, symbiosis and biodiversity. Concepts introduced include fungi, mycorrhizal network, hyphae, mycelium, symbiotic relationship, photosynthesis, seedlings, ectomycorrhizal network, endomycorrhizal network, coniferous, deciduous and mother tree.
  • Prior to reading this article and viewing the embedded videos, teachers could provide students with a Vocabulary Preview to engage prior knowledge and introduce new terminology. Ready-to-use Vocabulary Preview learning strategy reproducibles are available in [Google doc] and [PDF] formats. 
  • During and after reading and viewing the videos, students could create a Print-Video Venn Diagram to collect, compare and contrast the essential information in each resource. Ready-to-use Print-Video Venn Diagram learning strategy reproducibles are available in [Google doc] and [PDF] formats.
  • Alternately, after reading and viewing, students could complete a Concept Definition Web for the concept: mycorrhizal networks. Ready-to-use Concept Definition Web learning strategy reproducibles are available in [Google doc] and [PDF] formats. 
Teaching Suggestions
  • This article and embedded videos can be used in Biology for teaching and learning related to forests & forestry, symbiosis and biodiversity. Concepts introduced include fungi, mycorrhizal network, hyphae, mycelium, symbiotic relationship, photosynthesis, seedlings, ectomycorrhizal network, endomycorrhizal network, coniferous, deciduous and mother tree.
  • Prior to reading this article and viewing the embedded videos, teachers could provide students with a Vocabulary Preview to engage prior knowledge and introduce new terminology. Ready-to-use Vocabulary Preview learning strategy reproducibles are available in [Google doc] and [PDF] formats. 
  • During and after reading and viewing the videos, students could create a Print-Video Venn Diagram to collect, compare and contrast the essential information in each resource. Ready-to-use Print-Video Venn Diagram learning strategy reproducibles are available in [Google doc] and [PDF] formats.
  • Alternately, after reading and viewing, students could complete a Concept Definition Web for the concept: mycorrhizal networks. Ready-to-use Concept Definition Web learning strategy reproducibles are available in [Google doc] and [PDF] formats. 

Learn more

Fungus (2017)

Detailed article on Encyclopedia Britannica on fungi, their importance, and forms and function.

Plants talk to each other using an internet of fungus (2014)

Article from the BBC on how different fungi might help trees communicate and thrive.

The Earth's Internet: How Fungi Help Plants Communicate (2018)

Sci Show video (5:19 min.) on the networks that allow them to communicate.

How Trees Talk to Each Other (2016)

TEDSummit video (18:20 min.) with Canadian ecologist Suzanne Simard discussing how trees can talk to each other.

References

Amos, H. (2011, July 7). At the root of the problem: Trees may have trouble growing in changing environments. University of British Columbia.

BBC News. (2018, June 29). How trees secretly talk to each other.

Biology Dictionary. (n.d.). Mycorrhizae definition.

Fleming, N. (2014, November 11). Plants talk to each other using an internet of fungus. BBC.

Simard, S. W. (2009). Mycorrhizal networks and complex systems: Contributions of soil ecology science to managing climate change effects in forested ecosystems. Canadian Journal of Soil Science, 89(4), 369-382. DOI: 10.4141/cjss08078 

Simard, S. W., Beiler, K. J., Bingham, M. A., Deslippe, J. R., Philip, L. J., & Teste, F. P. (2012). Mycorrhizal networks: Mechanisms, ecology and modelling. Fungal Biology Reviews, 26(1), 39-60. DOI: 10.1016/j.fbr.2012.01.001  

Song, Y. Y., Simard, S. W., Carroll, A., Mohn, W. W., & Zeng, R. S. (2015). Defoliation of interior Douglas-fir elicits carbon transfer and stress signalling to ponderosa pine neighbors through ectomycorrhizal networks. Scientific Reports, 5(8495). DOI: 10.1038/srep08495

Song, Y. Y., Zeng, R. S., Xu, J. F., Li, J., Shen, X., Yihdego, W. G. (2010). Interplant communication of tomato plants through underground common mycorrhizal networks. PLoS ONE 5(10). DOI: 10.1371/journal.pone.0013324