“Mother Tree” ecologist Susan Simard shares the secrets of communicating between trees: snapshots

Ecologist Susan Simard says that trees are “social beings” who communicate with one another in collaborative ways that include lessons for humans as well.

Simard grew up in the Canadian forests as a descendant of loggers before becoming a forest ecologist. She is now a professor of forest ecology at the University of British Columbia.

The trees are connected to neighboring trees by an underground network of fungi Which are similar to neural networks in the brain, she explains. In one study, Simard saw a Douglas fir that had been struck by insects that seemed to send a chemical Warning signs To ponderosa grows nearby. Then the pine tree produced defensive enzymes to protect against the insect.

“It was a huge achievement,” says Simard. The trees were sharing “really important information for the health of the entire forest.”

In addition to warning each other of the danger, Simard says trees have been known to share nutrients at critical times to keep each other healthy. She says that trees in the forest are often linked together by an older tree that she calls the “parent” or “hub” tree.

“By communicating with all trees of different ages, [the mother trees] It can actually facilitate the growth of these young seedlings. “Seedlings will connect to the network of old trees and take advantage of the capacity of these huge uptake resources. Old trees will also transfer a little bit of carbon, nutrients and water to young seedlings, at critical times in their lives, which actually helps them survive.”

The tree study gained new resonance for Seymard when she was diagnosed with breast cancer. During her treatment, she learned that one of the chemotherapy drugs she relied on was actually derived from a substance that some trees make for self-defense. She explains her research on cooperation and coexistence in the woods, and shares her personal story in the new memoir Finding the mother tree: discovering the wisdom of the forest.

Interview highlights

She worked at a logging company in British Columbia in her twenties

It was in the late 1970s when I started; They were clear And I just started planting trees. And so, of course, this was very different from what I saw my grandfather, father, and uncles do. They got the strange tree out here and there. But this was killing all trees, large and small. This was my first job in the forestry industry, and it was very shocking to me. But it was also very exciting because it was so dangerous. I was also one of the first girls to work in the industry.

About being a young forester and realizing that mushrooms were key to forest health

On the forest floor … there are all kinds of insects, but there are also a lot of fungi. And the fungi are very colorful. There are yellow and purple and white and … it grows across the forest floor to the point where it kind of looks like gauze, approx. And so I found this yellow fungus. However, when I pulled out the seedlings that weren’t working well – they were yellow and dying – I realized their roots were kind of black and straight. … So I wondered, what are they missing? Have they lost this fungus? Was this fungus … a pathogen or was it a helper?

And in the end I learned that this was a special type of helper fungus called the mycorrhizal fungus – which just means that the fungus is the type that grows through the soil and picks up nutrients and water and returns them to the seedlings. So in the end, I was able to put together that these little, not well-functioning seedlings were missing them Mycorrhizal fungi.

About the critical relationship between trees and fungi

Keep in mind that all trees and plants – except for a very small handful of plant families – have mandatory relationships with these fungi. This means they need them in order to survive, grow, produce cones and fit – in other words, to pass on their genes to future generations. And fungi depend on plants or trees … because they do not have leaves on their own [for photosynthesis]. And so they enter into this symbiosis in that they live together at the root, and they exchange these basic resources: carbohydrates from the plant versus nutrients from the fungi, in this two-way exchange that is very tight, almost like a market exchange. If you give me five dollars, I’ll give you five dollars. It is very structured between these two coexistence partners. But, yes, all the trees and all the plants in all of our forests around the world depend on this relationship.

How trees can help each other by sharing nutrients

[At the time] Birch is considered a weed. There was a massive program of spraying and pesticides for these trees to get rid of them because forests considered the birch to compete with the Douglas fir, and to compete for light especially. I was noticing in these plantations that when they removed the birch trees, when they sprayed or cut them down, there was disease in the forests that would start spreading like a fire. It was called Armillaria root disease. I really thought we were doing something wrong here. And so I wanted to know if the birch somehow protected the fir from this disease and that when we cut it down it only got worse.

I learned about these fungi and how they can protect trees from disease. And I also heard about David Reed’s work in the UK, where he showed that in the lab trees can be bound together by root fungi and pass carbon between them. So I tested this between birch and fir in our sick farms.

I planted birch, spruce and cedar together in little triplets. … and tracked how the carbon particles moved back and forth between birch and fir and didn’t actually end up in cedar. Because rice that they They form a different type of fungus that is not related to either birch or fir. And therefore [the cedar] He wasn’t actually in the grid with birch and spruce wood, and hardly picked up any of these analogs.

I knew that birch and spruce shared carbon underground – which went against the prevailing wisdom that they only compete for light and also that the more I kept Douglas Spruce, the more carbon was sent to Douglas Fir so there was a net conversion from birch wood to Spruce that was kinda softening the shading effect.

This way the ecosystem was keeping its balance – birch and fir could coexist due to this cooperative behavior that was kind of compensating for some of the competition that was underway.

On the ways her breast cancer diagnosis shaped her research

It definitely had a huge impact on me, and it changed my life as a result, but it changed my research as well. That was when I started working with kin recognition, to see if these ancient trees, especially when they were dying, could recognize and help their relatives. And I had alumni who really come to ask these questions. You know, if the tree is dying, they send more [nutrients and other signals] To their relatives? And we found that they do.

Then I also started some research – paclitaxel was one of the main chemotherapy drugs I was given. [also called Taxol]. Paclitaxel is a defensive agent – actually a defensive chemical – that is produced by the Pacific yew tree, or all yew around the world, in fact. It was essential to my recovery – this compound that trees produce to defend themselves against disease.

And so I thought, you know what, I want to know more about this. She’s starting a study with a new graduate student, Eva, as she looks at the yews neighborhood – whether they’re related to old cedar trees and shrubs, and how their neighbors might influence their ability to produce high-quality taxol to increase their defense capabilities.

We just discovered that these trees are all interconnected by the mycorrhizal muscle network, which provides the means for them to communicate this information. So, yeah, we’re getting this business started. I hope that helps us, for one reason, in preserving these trees to their medicinal qualities – because they are good at what they’ve done. They have developed these, what we call drugs, but they are for themselves to defend themselves against disease as well. Cancer treatment is what motivated me to do this study. And I’m so excited to see what we’re learning.

Why is it important to let the old tree go through a long dying process on its own

[Trees] get old. They hold back in the end. Dying is a very time consuming process. It can take decades for the tree to die. In the process of dying, there are a lot of things that happen. And one of the things that I studied was where their energy is directed – where is the carbon stored in their tissues – where does it go? And so we labeled some trees with carbon dioxide – using C13, which is a stable isotope – and we saw that we were actually causing these trees to die. We stress them out by pulling out their needles, attacking them with worms, etc. Then we saw what happened to her carbon.

And we found that about 40% of the carbon travels through the networks to their neighboring trees. The rest of the carbon may be dispersed through natural decomposition processes … but some of it is directed directly to the neighbors. In this way, these old trees have a very direct effect on the regenerative capacity of the new forest in the future.

This is a completely different way of understanding how ancient trees contribute to future generations – that they have a potency in future generations. And our logging practices to get rid of dying trees, or trees that have just died or burned in forest fires – if we go and cut them right away, we are actually shortening this natural process.

Our studies indicate that it will have indirect effects on the upcoming regeneration. They will not be well prepared for their next life. So I was trying to tell people: Let’s back off this rescue so the trees have a chance to pass this energy and information on to the upcoming new seedlings.

Sam Briger and Thea Chaloner produced and edited this interview for broadcast. Bridget Bentz, Molly Seavy-Nesper, and Deborah Franklin adapted it for the web.