For Trees (and other green plants) WWW stands for Wood Wide Web

In Richard Power's National Book Award and Pulitzer Prize winning novel The Overstory, one of the characters, a plant scientist dares to propose the idea that trees in a forest are signaling one another...trees a little way off, untouched by the invading swarms, ramp up their own defenses when their neighbor is attacked.  Something alerts them.  They get wind of the disaster.  They prepare.  

But in the chronology of the novel this is in the late 1950s and the idea seems preposterous to other plant scientists.  The big name professors mock both her and her research:  "Patricia Westerford displays an almost embarrassing misunderstanding of the units of natural selection..." The response of her peers trashes her reputation; her research publications languish unread. (Powers, 2018)

But science is dynamic: old professors retire to be replaced by assistant professors who grew up in a world that is also dynamic and changed by new technologies and discoveries.

Phenomena that once had appeared odd or even bizarre and inexplicable to the teachers transform into phenomena that no longer frighten their students; the students think of ways to seek answers to new questions.

One of these facts, previously viewed as odd, bizarre, inexplicable; the idea that trees can message each other, no longer seemed so bizarre and inexplicable after Claude Shannon’s 1948 paper A Mathematical Theory of Communication which defined “the fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point. Frequently the messages have meaning.”  If communication is not just talking and writing but also includes the sharing of information, talking trees may not seem quite so odd, bizarre, or inexplicable. (Gleick, 2011)

We now leave the novel’s portrayal of reality and enter reality as described in scientific papers. 

If messages are to be passed between trees, there must be some pathway to connect sender with receiver.

The discovery of the pathway is credited too A.B. Frank, a German botanist who in 1885 is credited with the discovery that many trees are in a symbiotic relationship with fungi living on or in the tree’s roots. This relationship is known as a mycorrhiza from the Greek word for fungus myco- and the word for root rhiz-, fungus root.

​The vegetative body of a fungus is composed of many filaments called hyphae. The hyphae taken together compose the fungus’s mycelium.

In a mycorrhiza, the hyphae, fine tube-like fungal bodies extend outwards from the root as in the image on right showing the root and the mycorrhiza’s tiny hyphae filaments. As the hyphae penetrate the soil, they collect important chemicals needed by the plant to thrive such nitrates and phosphates which flow them back to the plant’s root.  In exchange the fungi composing the mycorrhiza gets room and board:  a safe place to live along with carbohydrates produced by the plant’s photosynthesis.

Fugus-root or mycorrhizae are neither exotic or rare, given that perhaps 85 percent of all plants include a mycorrhiza and that nearly every ecosystem is dominated by plants with mycorrhizae.

​​This means that mycorrhizal plants play significant role in all ecosystem processes such as seedling survival and soil aggregation; that is, the ability of soils to retain and exchange air and water. According to a study that draws on a wide range of research and attempts to quantify the effect of mycorrhizal on the ecosystem such mycorrhizal plants affect up to 80% of the carbon cycle; 30% of decomposition; up to 80% of the nitrogen cycle; plant phosphorus uptake up to 100% in the case of orchids; and the reduction of  the loss of nitrogen from leaching by up to 50%. (van der Heijden, Martin, Selosse, & Sanders, 2015)

The description so far might suggest that specific kinds of fungi colonize specific kinds of plants. This is not the case. Many different kinds of fungi may make up the mycorrhiza of any given plant.

Even more striking has been the discovery that a mycorrhiza not only connects its particular oak or willow to its particular soil resource but it also links the particular oak or elm to other oaks or spruce and so on.Suzanne Simard, now a professor at the University of British Columbia, discovered that the mycorrhizal connections created a complex set of networks under the forest floor by which trees were connected to trees of different species, trees were connected to forest plants as well as to the mycorrhiza.

Simard studied the connection between the paper birch and the Douglas fir. Using radioactive isotopes to track the interactions, she found that while the paper birch and the Douglas fir are competitors, they are also connected by the mycorrhiza hyphae which each uses to share resources with the other.  During the time of day when the Douglas fir is in the shade and the paper birch in full sunlight, the Douglas fir receives carbon; while in the fall when the paper birch had shed its leaves the evergreen the Douglas sends carbon to the paper birch! (Toomey, 2016)
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Simard suggests that the mycorrhiza itself plays an as yet unknown role in the transfer of resources across the network.  In human terms, the mycorrhiza has an “interest” in the process since it is sharing nitrates and phosphates with the tree in exchange for a portion of the carbohydrates synthesized by the tree. Therefore, the mycorrhiza must somehow benefit from the interchanges between the paper birch and the Douglas fir just as the fir benefits somehow by sending carbon to the paper birch in the fall.

Simard’s graduate students are exploring yet other ways that the wood wide web works. One has found that seedlings from the same tree apparently recognize one another through their root tips which they favor over the root tips of seedlings from different trees by sharing carbon. “We don’t know how they do it,” according to Simard. She wonders if it might be scent but do roots have scent organs? (Grant, 2018)

Suzanne Simard, who may resemble a latter-day and real version of Patricia Westerford, writes about her lab’s findings in ways that would be familiar to the readers of The Overstory. Just as the fictional Patricia Westerford described trees as talking, Professor Simard describes the biggest and oldest trees that have the most fungal connections as Mother trees in the sense of supportive and nurturing. The Mother trees deep roots allow Mother trees to draw up large amounts of water that that she is prepared to share in dry periods with younger and therefore more shallow-rooted trees.  

Simard tells an interviewer that this kind of language makes “more sense because we were looking at not just resource transfers, but things like defense signaling and kin recognition. 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.” (Toomey, 2016)

Resources:

Gleick, J. (2011). The Information: A History, A Theory, A Flood. New York: Pantheon Books.

Grant, R. (2018). Do Trees Talk to Each Other? A controversial German forester says yes, and his ideas are shaking up the scientific world. Smithsonian Magazine.

Powers, R. (2018). The Overstory. New York: W.W. Norton & company.

Shannon, C. E. (1948). A Mathematical Theory of Communication. The Bell System Technical Journal, 27, 379-423, 623.

Toomey, D. (2016). Exploring How and Why Trees ‘Talk’ to Each Other. Yale e360. Retrieved from e360.yale.edu
van der Heijden, M. G. A., Martin, F. M., Selosse, M.-A., & Sanders, I. R. (2015). Mycorrhizal ecology and evolution: the past, the present, and the future. New Phytologist, 205). Retrieved from https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.13288

Images:
Page 2: Micro-photo of tree root with mycorrhiza hyphae from https://www.bbc.com/news/science-environment-22462855 
 

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