The Weekend Wonk: How Trees Talk to Each Other

September 10, 2016

Yale Environment 360:

Two decades ago, while researching her doctoral thesis, ecologist Suzanne Simard discovered that trees communicate their needs and send each other nutrients via a network of latticed fungi buried in the soil – in other words, she found, they “talk” to each other. Since then, Simard, now at the University of British Columbia, has pioneered further research into how trees converse, including how these fungal filigrees help trees send warning signals about environmental change, search for kin, and transfer their nutrients to neighboring plants before they die.

By using phrases like “forest wisdom” and “mother trees” when she speaks about this elaborate system, which she compares to neural networks in human brains, Simard’s work has helped change how scientists define interactions between plants. “A forest is a cooperative system,” she said in an interview with Yale Environment 360. “To me, using the language of ‘communication’ made more sense because we were looking at not just resource transfers, but things like defense signaling and kin recognition signaling. We as human beings can relate to this better. If we can relate to it, then we’re going to care about it more. If we care about it more, then we’re going to do a better job of stewarding our landscapes.”

Yale Environment 360: Not all PhD theses are published in the journal Nature. But back in 1997, part of yours was. You used radioactive isotopes of carbon to determine that paper birch and Douglas fir trees were using an underground network to interact with each other. Tell me about these interactions.

Suzanne Simard: All trees all over the world, including paper birch and Douglas fir, form a symbiotic association with below-ground fungi. These are fungi that are beneficial to the plants and through this association, the fungus, which can’t photosynthesize of course, explores the soil. Basically, it sends mycelium, or threads, all through the soil, picks up nutrients and water, especially phosphorous and nitrogen, brings it back to the plant, and exchanges those nutrients and water for photosynthate [a sugar or other substance made by photosynthesis] from the plant. The plant is fixing carbon and then trading it for the nutrients that it needs for its metabolism. It works out for both of them.

It’s this network, sort of like a below-ground pipeline, that connects one tree root system to another tree root system, so that nutrients and carbon and water can exchange between the trees. In a natural forest of British Columbia, paper birch and Douglas fir grow together in early successional forest communities. They compete with each other, but our work shows that they also cooperate with each other by sending nutrients and carbon back and forth through their mycorrhizal networks.

e360: And they can tell when one needs some extra help versus the other, is that correct?

Simard: That’s right. We’ve done a bunch of experiments trying to figure out what drives the exchange. Keep in mind that it’s a back and forth exchange, so sometimes the birch will get more and sometimes the fir will get more. It depends on the ecological factors that are going on at the time.

One of the important things that we tested in that particular experiment was shading. The more Douglas fir became shaded in the summertime, the more excess carbon the birch had went to the fir. Then later in the fall, when the birch was losing its leaves and the fir had excess carbon because it was still photosynthesizing, the net transfer of this exchange went back to the birch.

There are also probably fungal factors involved. For example, fungus that is linking the network is going to be looking to secure its carbon sources. Even though we don’t understand a whole lot about that, it makes sense from an evolutionary point of view. The fungus is in it for its own livelihood, to make sure that it’s got a secure food base in the future, so it will help direct that carbon transfer to the different plants.

e360: Through molecular tools, you and one of your graduate students discovered what you call hub, or mother, trees. What are they, and what’s their role in the forest?

Simard: Kevin Beiler, who was a PhD student, did really elegant work where he used DNA analysis to look at the short sequences of DNA in trees and fungal individuals in patches of Douglas fir forest. He was able to map the network of two related sister specials of mycorrhizal fungi and how they link Douglas fir trees in that forest.

Just by creating that map, he was able to show that all of the trees essentially, with a few isolated [exceptions], were linked together. He found that the biggest, oldest trees in the network were the most highly linked, whereas smaller trees were not linked to as many other trees. Big old trees have got bigger root systems and associate with bigger mycorrhizal networks. They’ve got more carbon that’s flowing into the network, they’ve got more root tips. So it makes sense that they would have more connections to other trees all around them.

In later experiments, we’ve been pursuing whether these older trees can recognize kin, whether the seedling that are regenerating around them are of the same kin, whether they’re offspring or not, and whether they can favor those seedlings — and we found that they can. That’s how we came up with the term “mother tree,” because they’re the biggest, oldest trees, and we know that they can nurture their own kin.


20 Responses to “The Weekend Wonk: How Trees Talk to Each Other”

  1. Lionel Smith Says:

    Carl Safina informs on the spoiling of the ocean caused by ramant timber extraction in the Pacific North West, as well as other bad habits on the Eastern seaboard in his:

    ‘Song for the Blue Ocean: Encounters Along the World’s Coasts and Beneath the Seas’

    other worthwhile titles of his are:

    ‘Voyage of the Turtle: In Pursuit of the Earth’s Last Dinosaur’


    Eye of the Albatross: Visions of Hope and Survival

    Colin Tudge has written some excellent books on trees such as:

    ‘Secret Life of Trees’


    ‘The Tree: A Natural History of What Trees Are, How They Live, and Why They Matter’

    and many others on a variety of ecological topics including:

    ‘So Shall We Reap: How Everyone Who Is Liable To Be Born In The Next Ten Thousand Years Could Eat Very Well Indeed; And Why, In Practice, Our Immediate … Are Likely To Be In Serious Trouble ‘

    Now, Professor Callum Roberts has written two essential books for those who wish to learn how badly we are plundering the seas

    The Unnatural History of the Sea

    which provides an object lesson on ‘shifting baseline’ and why fishing quotas should be rigoursly enforced, never mind what Trump’s latest pet poodle (Nigel Farage) might say.


    The Ocean of Life: The Fate of Man and the Sea

  2. dumboldguy Says:

    I’ll have more to say about this generally great piece, but for now I’d like to comment on how casually Dr. Simard talks about running from Grizzly bears (a mama with cubs no less—-the most dangerous kind), and doing it MORE THAN ONCE. Grizzlies can outrun a race horse over short distances, and she does her audience a disservice by acting like it’s no big deal to encounter one.

    I was generally scared you-know-what whenever I put boots on the ground in Glacier and Yellowstone National Parks out of visual range of a road because of the possibility of running into a Grizzly Here’s a clip of the Craighead brothers, famous Grizzly researchers, as they had an encounter with a partially sedated, not quite full size Grizzly bear some 40 years ago.

    PS Running from bears (and mountain lions) is not recommended—-it triggers a “chase the prey” reflex.

    • dumboldguy Says:

      Who is the moron who “thumbs-downed” this comment? Care to tell us why you did so?

      Have you fallen in love with Dr. Simard and just can’t bear to have anyone point out her flaws? (stay tuned for more)

      Or are you one of those morons who think encountering wild animals (in the wild) is no different than visiting a zoo?

  3. indy222 Says:

    I wonder what the trees are saying to each other about us – a not very friendly invasive species? There are other relevant films… Wasn’t there a cheesy 1950’s SciFi about killer Trees?

    • dumboldguy Says:

      There have been lots of SciFi movies about “killer” trees, and not all of them were all that “cheesy”. Day of the Triffids, Little Shop of Horrors, The Attack of the Killer Tomatoes (my overall “fun” favorite), and IMO the all around best—-The Ruins—a truly scary film made from a truly scary book The happening (2008) is a modern day tale of “revenge” of the plants because we are destroying the planet.

      And If plants could really “think” and “talk” (they can’t do either), I’m sure they would be quite upset about what a biological disaster humans have brought to the planet, and WOULD be plotting their revenge. They are in effect getting their revenge by “dying out” in so many ways, and that WILL ultimately help to cause the extinction of humans (and most everything else on the planet).

    • redskylite Says:

      “Don’t dick with the trees” . . .

  4. dumboldguy Says:

    The basic science understandings behind Dr. Simard’s discoveries are terrific. It’s things like this that caused me to switch emphasis from physics to biology 50+ years ago.

    In the ’50’s, the world of physics—-atomic energy, subatomic particles, electronics, transistors, etc. was intriguing, so that’s what I studied as an undergraduate—–by the 60’s the advances made in biology—-in genetics, DNA, biochemistry, evolution—-and particularly our growing understanding of ecology—-the workings of the biosphere and the inter-connectedness of everything on Earth—-were far more interesting to me, so I did my graduate work in biology and taught it.

    Dr. Simard’s work is great stuff and adds to the body of knowledge about interactions between living things in the forest. Others have done similar studies and found that even one tree growing in a field alters the area around it and produces a “mini-biome” with a far more diverse and healthy assortment of fungi, bacteria, other plants, insects and earthworms, etc. Life “in the woods” is not simple—-it is not just a place where bears go to do “you know what” and chase biologists.

    I actually smiled as I listened to her talk—-at the “elegance” (as used in science) of her work and discoveries. At the same time I gritted my teeth at her very unscientific anthropomorphizing of plants and the downright silliness of some of her comments.

    Trees talk? Works kind of like the internet? Trees pass on WISDOM? Like Yin and Yang? Lord love a duck! I guess when you’re doing a TED talk and talking about some obscure science to a general audience that you need to “jazz it up” and capture their attention, and she certainly did that. Maybe some of them will be motivated to push for better forestry practices that take science into account rather than profit, and that’s a good outcome that (somewhat) excuses her silliness

    PS The largest living entity on the planet is thought to be a colony of soil fungus, with a grove of interconnected aspen trees in close contention. The biggest single living thing is a Sequoia. Plants (and trees) rule!

  5. dumboldguy Says:

    PS Forgot to mention that some studies have been done that point to plants having the ability to “feel pain”, and that they even possess a sort of telepathic sense as well—-they demonstrate a physiological reaction when someone comes into the room and simply THINKS about pulling off their leaves or burning them—-in effect, they “scream” BEFORE any actual injury is inflicted..

    Remember that the next time you eat your raw veggies. If they are fresh enough, they ARE screaming in silence as you tear them apart with your nasty omnivore’s teeth.

    And I wonder what the reaction is in Dr. Simard’s forest when the loggers appear and think “bad thoughts” about the trees? Does some sort of fear reflex go viral on the forest’s “internet”? Are there deniers among the trees that say “Not to worry, the loggers are our friends”?

  6. No wonder capitalism has declared war on these socialist trees

    • dumboldguy Says:

      Actually, capitalism has declared war on every last living thing on the planet, not just on the trees. But DO remember that Nature Bats Last—–when the final innings are played most humans and their invention of “capitalism” will be eliminated, and the life forms that remain on the planet will go back to obeying the Laws of Nature.

  7. Lionel Smith Says:

    But DO remember that Nature Bats Last—–when the final innings are played most humans and their invention of “capitalism” will be eliminated…

    This is why I urge people to find and read a copy of this book: Song for the Blue Ocean: Encounters Along the World’s Coasts and Beneath the Seas for horrendous stories of rampant capitalism using humans as the unwitting agents of their own destruction after destroying the very systems that supported themselves, families and communities, capitalism which abandoned all when the resources were played out and the environment wrecked effectively for the next millennium.

    In the chapter ‘Astoria’ Safina relates one of the conversations with Reverend Irene Martin (near Skamokawa, Washington):

    “In my community,the loggers are suffering, along with the fishermen. The logging companies pulled out with no show of social responsibility…”

    “I went as part of a delegation over to Weyerhaeuser when the bailed out of here a few years ago. We asked whether the local people could at least be put to work in doing things like tree planting, brush clearing, maintaining roads. And we were told …’Were going to hire cheap crews from Mexico’”

    So there you are Donald, Trump like tactics to get cheap labour from a place that the Donald wishes to block off with a wall.

    • dumboldguy Says:

      Checked my county library system and they don’t have a copy. Looked it up on line and read some excerpts. I like Safina’a writing—-a bit over the top and even “florid” in some of his word use for a scientist, but it’s fun to read—-like a novel in places. It DOES look like a good read, especially for those who like (or need) their science books to be “exciting”.

      It IS a bit out of date and somewhat narrow in focus, though. A broader and more recent look at ALL the problems in the oceans can be found in The World is Blue by oceanographer Sylvia Earle, National Geographic Society, c2009. Her writing may not be quite as much fun to read as Safina’s, but it is clear and powerful and covers the same ground and much more.

      Earle has been called “a living legend” by the Library of Congress, was named Time magazine’s first “Hero of the Planet”, and holds a number of positions and has been given many awards—-she is no lightweight.

  8. Lionel Smith Says:

    I like Safina’a writing—-a bit over the top and even “florid” in some of his word use for a scientist, but it’s fun to read—-like a novel in places.

    One of the decisions an author has to make is deciding who is audience is, in other words choosing language that may get through to some who may not otherwise take an interest.

    In this respect I am sure Safina had very much a lay audience in mind and decided to go with a story telling narrative rather than the dry fact delivery of texts such as Raymond Bradley’s excellent Paleoclimatology: Reconstructing Climates of the Quaternary.

    I didn’t consider that by ranging description of depredations in fishery on the east coast and forest wrecking which combined with the blocking of hundreds of salmon runs by dams on the Pacific west coast, combined with practices and conditions on the other side of the Pacific to be limited in scope. The book my be ‘long in the tooth’ now but how many people who should be not aware of the scale of the ecological disaster unfolding on both sides of the continental US and further afield as a result.

    The high price paid by fisher folk on the west coast from losing income and a way of life because of the actions of water interests has, as the headwaters and ice pack have withered, become of little account. That agricultural interests were able to purchase water at less than the cost of the infrastructure to provide it is a travesty, particularly as once again we see the pecuniary interests of a few satisfied by tax-payers money in what is in this case effectively subsidised water provision.

    OK, so much has happened since 1998 when the book was first published but IMHO it is a story still worth pushing not least in reminding those who may have forgotten that the freedom for one can be the death of another. Of course sociopathic corporations don’t care about such things. Consider that books such as this are valuable for any bibliography they carry which can be a jumping off point for those who wish to dig deeper having been provided with the impetus.

    • dumboldguy Says:

      My comments weren’t meant to be disparaging. It’s simply fact that talking about those specific “horror stories” (that Safina does so well) IS “limited in scope” when one considers that things like ocean acidification, temperature increases, pollution, and disruption of the thermohaline circulation are far more damaging to the oceans and the 1.2 billion people who depend on them for a major portion of their food. Yes, the small pictures Do make up the big picture, and it’s good to get people’s attention with some glaring examples of “wrongfulness”, but The World is Blue is a much better single book to read.

      • Lionel Smith Says:

        OK I have put in for ‘The World is Blue’, the pile of books for me to read is growing rapidly (SWMBO despairs at the groaning book shelves), but noted that another suggested book was the rather more recent ‘The Ocean of Life: The Fate of Man and the Sea’, see first post above, which I have already absorbed.

  9. Ron Voisin Says:

    What was I thinking? I wasn’t,

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