Soil Microbiom and Trees

In this Friday episode of Talking Trees, we explore the soil microbiome as a critical but often overlooked driver of tree health, biodiversity, and ecosystem resilience. Far beyond just a substrate for roots, soil is a living, dynamic system influencing the entire tree environment.

We discuss:

• How soil microbial communities support nutrient cycling, disease resistance, and plant growth through complex interactions
• The concept of soil health as a foundational element of the One Health framework—linking plant, animal, and human well-being
• The evolving understanding of soil as a multifunctional ecosystem service, not merely a medium for productivity
• Why soil health assessment should integrate biological, chemical, and physical indicators to reflect its true vitality
• The dual role of soil microbes as both beneficial allies and potential sources of pathogens, highlighting the need for careful balance

Healthy soils mean healthy trees—and understanding this hidden world is key to building sustainable, resilient landscapes in the face of climate and biodiversity challenges.

Background information:

• Banerjee et van der Heijden. 2022. Soil microbiomes and one health.pdf
• Lehmann et al. 2020. The concept and future prospects of soil health.pdf

Chapters

• 0:00 Introduction to Soil Health
• 1:03 The Living Soil Ecosystem
• 3:33 Mycorrhizal Relationships with Trees
• 5:14 One Health: Everything is Connected
• 8:13 Sustainable Practices for Healthy Soil
• 11:42 Supporting Native Ecosystems
• 13:49 Conclusion and Key Takeaways

Transcript

Roger: 0:02

Talking Trees with Lillian Jadd. Welcome to Talking Trees, your daily journey into the intricate connections between nature and our well-being. In today's episode, we explore the concept of soil health within the broader One Health framework, highlighting the interdependence of human, animal, plant and environmental health. Our first source delves into the crucial role of soil microbiomes, examining how these microscopic communities underpin the health of diverse ecosystems and ultimately influence overall vitality. The second source expands on this idea, investigating the definition and future of soil health as a key pillar of sustainability. It discusses various indicators and assessment methods, while exploring how soil health ties into ecosystem services and human wellness. Join us as we uncover the hidden world beneath our feet and its profound impact on life above.

Jad: 1:03

Hey everyone and welcome to a deep dive into a world that's pretty much invisible but totally essential for the work that we do as arborists.

Lilly: 1:11

You got it. We're talking about the soil microbiome.

Jad: 1:14

Right, the soil microbiome, all those billions and billions of tiny organisms living in the soil.

Lilly: 1:19

And I mean it when I say billions.

Jad: 1:20

I bet you know I've been looking at some research papers lately on this topic soil microbiomes and one health Banerjee and van der Heiden. That was from 2022, and also the concept and future prospects of soil health by Lehman and some others from 2020.

Lilly: 1:37

Oh yeah, those are really interesting papers.

Jad: 1:39

They are. They really highlight just how complex and important this whole world beneath our feet is.

Lilly: 1:46

Yeah, and they connect it to everything else too. You know, plant health, animal health, even human health. It's all connected, it's all part of what they call One Health.

Jad: 1:53

Right One Health. So before we get too far ahead of ourselves, can you give us a little bit of a picture of just how much life is actually down there in the soil?

Lilly: 2:02

OK, so imagine this All right the soil holds the largest amount of global biomass, except for plants, of course.

Jad: 2:09

Of course.

Lilly: 2:09

So besides plants, soil has the most and bacteria are the most abundant, then fungi and archaea.

Jad: 2:16

More than animals, oh yeah, way more.

Lilly: 2:18

The total number of microorganisms in a soil is larger than the biomass of all animals on earth.

Jad: 2:23

Wow, that's amazing. So we're talking about like a whole universe under our feet, exactly. So how does all of this microscopic metropolis affect the trees that we work with every day?

Lilly: 2:34

Well, soil microorganisms are basically essential for nutrient cycling. I mean they provide trees with 18 out of the 29 essential elements that they need to grow.

Jad: 2:43

So it's not just about giving a tree the right fertilizer.

Lilly: 2:45

Nope, it's much more complex than that.

Jad: 2:47

We have to think about the health of this entire community underground.

Lilly: 2:50

You got it. It's like an ecosystem.

Jad: 2:52

An ecosystem, okay. So what about the rhizosphere? I know that's important.

Lilly: 2:55

Oh yeah, the rhizosphere is super important An area right around the roots of a tree. It's just teeming with microbial activity, all kinds of bacteria and fungi interacting with those roots in all kinds of ways that we're still figuring out.

Jad: 3:09

So you mentioned bacteria. What are some of the things that different bacteria do in this rhizosphere ecosystem?

Lilly: 3:14

Well, take rhizobium bacteria, for example. They've got this symbiotic relationship with certain trees, where they convert atmospheric nitrogen into a form that the trees can actually use. It's like a natural fertilizer factory right there in the soil.

Jad: 3:28

Wow, that's pretty cool.

Lilly: 3:29

It is, and then you've got fungi too. Fungi play a big role, especially mycorrhizal fungi. They're like these threads that extend way beyond the reach of the roots and they help the tree access water and nutrients more efficiently.

Jad: 3:40

So it's like they're expanding the tree's feeding zone.

Lilly: 3:43

You could say that and in return the tree provides the fungi with sugars from a photosynthesis. So it's a win-win.

Jad: 3:48

Mutually beneficial. Millions of years of evolution.

Lilly: 3:51

Yeah, it's pretty amazing. So are there specific types of mycorrhizae that are better for certain trees?

Jad: 3:58

That's a good question, you know, because I know there are different types of mycorrhizae.

Lilly: 4:02

Right. Well, like, for example, you have ectomycorrhizae. Those are commonly found on trees like pines and oaks and birches. They form this sheath around the root tips and their hyphae extend out into the soil.

Jad: 4:14

It's creating a huge network, exactly.

Lilly: 4:16

And then you've got arbuscular mycorrhizae. Those are found on a lot of different trees, like maples and ash and fruit trees. They actually penetrate the root cells. They form these structures called arbuscules. Arbuscules, okay, and they actually penetrate the root cells.

Jad: 4:27

They form these structures called arbuscules Arbuscules. Okay, and that's where the nutrient exchange happens. Wow, it seems like knowing the types of mycorrhizae that are associated with different tree species could really help us make better decisions about planting and care Absolutely.

Lilly: 4:38

The more you understand about these relationships, the better you can work with nature. Instead of against it Right it's about seeing soil as a living ecosystem, not just some dirt.

Jad: 4:48

Yeah, and a healthy ecosystem is a resilient ecosystem.

Lilly: 4:51

Exactly which brings us to disease. Suppressive soils.

Jad: 4:55

Disease suppressive soils. What are those?

Lilly: 4:57

These are soils that have a community of microorganisms that are really good at keeping pathogens under control.

Jad: 5:03

So they can actually prevent soil borne diseases or at least reduce their impact.

Lilly: 5:07

And get this. This ability to suppress diseases can last for over 40 years, even when pathogens are present.

Jad: 5:13

That is incredible. So it's like the soil itself has this built in defense system.

Lilly: 5:18

You could say that it's like a microclimatic army protecting your trees.

Jad: 5:21

This whole soil microbiome is like a superpower.

Lilly: 5:23

It is. It's a superpower.

Jad: 5:24

But I'm guessing there are things that we do that can mess it up.

Lilly: 5:27

Unfortunately, yes, some of the practices that are common in arboriculture can actually harm the very organisms that we're trying to protect.

Jad: 5:35

Like what.

Lilly: 5:36

Well, things like excessive tillage and the use of synthetic pesticides can have a negative impact on the diversity and function of the soil microbiome.

Jad: 5:45

So things that we think are helping could actually be hurting.

Lilly: 5:48

It's possible. And then there's also the issue of antimicrobial resistance.

Jad: 5:52

Antimicrobial resistance.

Lilly: 5:53

Yeah, you know where the overuse of antibiotics in livestock can lead to resistant bacteria.

Jad: 6:00

And that affects the soil.

Lilly: 6:02

Those resistant bacteria can end up in the soil and then you've got soil-dwelling mice that can pick up those microorganisms from the soil and then farm animals graze and they ingest soil.

Jad: 6:12

Ingest soil.

Lilly: 6:13

Yeah, they eat it and it contributes to their rumen, microbiome.

Jad: 6:17

Rumen microbiome what's that?

Lilly: 6:18

It's the first compartment of a cow's stomach. It's full of microorganisms that help break down plant material.

Jad: 6:24

Oh, okay.

Lilly: 6:25

And it's estimated that up to 3% of a cow's rumen microbiome can come from ingested soil.

Jad: 6:31

So even a cow's digestion depends on healthy soil.

Lilly: 6:33

It seems so Wow it's all connected. It is, and just like those practices can affect soil health and tree health, they can also affect livestock health.

Jad: 6:42

It all comes back to one health, doesn't it?

Lilly: 6:44

Exactly, it's all part of the same web, so we're part of this web too, right? Absolutely, we're connected to the soil through the food we eat and we're exposed to soil microorganisms through dust and even geophagy.

Jad: 6:56

Geophagy what's?

Lilly: 6:56

that that's the practice of eating soil or clay. It's more common than you might think, especially in certain cultures.

Jad: 7:03

Interesting. So the health of the soil is directly connected to our own health. It is even in ways that we might not realize. We've covered a lot of ground here, this first part, from the abundance of life in the soil to the connections between soil microbes, trees, animals and even ourselves. So what are some of the key takeaways that you want our listeners to remember from this part of our deep dive?

Lilly: 7:23

I think the most important takeaway is that soil is alive. It's not just dirt, it's an ecosystem, and it plays a vital role in the health of everything from the trees we care for to the food we eat, and as arborists, we have a responsibility to understand and protect this hidden world.

Jad: 7:40

It's like we've been given a glimpse into this secret world.

Lilly: 7:42

Exactly.

Jad: 7:43

And now we have a chance to become allies with the organisms that live there.

Lilly: 7:46

By working with them instead of against them.

Jad: 7:48

Exactly, and by doing that we can improve the health of our trees and contribute to a healthier planet for everyone.

Lilly: 7:54

That's the goal, and now I want to learn more about how what we do as arboriculture and land management in general can actually unintentionally harm the soil.

Jad: 8:13

Right, we were talking about excessive tillage and synthetic pesticides earlier.

Lilly: 8:16

Exactly.

Jad: 8:17

Can you talk a bit more about how those practices actually disrupt the balance of the soil microbiome?

Lilly: 8:23

Sure. So tillage, especially deep tillage, can be incredibly disruptive. I mean, you're essentially like bulldozing a forest, you know. Yeah, you're uprooting trees, you're destroying habitats, you're scattering all the inhabitants, right, and it's kind of the same thing with tillage. You know you're disrupting the soil structure, you're exposing microorganisms to harsh conditions and you're breaking up those intricate networks of fungal hyphae.

Jad: 8:44

So we're basically destroying the home of all these beneficial microbes.

Lilly: 8:47

Yeah, you could say that.

Jad: 8:48

What about synthetic pesticides? How do they affect the soil ecosystem?

Lilly: 8:51

Well, you know, pesticides are designed to target specific pests, but they often have unintended consequences. Right, they can also harm beneficial microbes, which can lead to a decline in biodiversity and overall soil health.

Jad: 9:05

So it's like we're using a sledgehammer when what we really need is a scalpel.

Lilly: 9:10

Yeah, that's a good analogy.

Jad: 9:12

So we need to be a lot more mindful about our approach. What are some things that we can do differently? What are some alternative practices that we can use that will actually promote a healthy soil microbiome?

Lilly: 9:23

Well, one of the most important things is reducing or even eliminating tillage. Okay, whenever possible.

Jad: 9:29

Less killage.

Lilly: 9:29

Yeah, minimizing soil disturbance allows those microbial communities to thrive and it helps to maintain the soil structure.

Jad: 9:36

Right, less disturbance, happier microbes.

Lilly: 9:38

Exactly. And then another really valuable tool is incorporating organic amendments.

Jad: 9:44

Like what? What kind of organic amendments are we talking about?

Lilly: 9:47

Things like compost, biochar, well-composted animal manure these can really work wonders for your soil.

Jad: 9:55

How do they actually help the soil microbiome?

Lilly: 9:57

Well, they introduce a lot of diverse organic matter, which is like food for the microbes, and it improves the overall soil structure.

Jad: 10:04

So it's like having a party and you're bringing all the good food.

Lilly: 10:06

Exactly the more diverse the food, the better the party.

Jad: 10:12

Okay, so less disruption, more diversity. I'm seeing a pattern here. What about the types of trees that we plant? Can that affect soil health?

Lilly: 10:17

Oh, absolutely. Native trees have co-evolved with the soil microbes in their region Right and they form these complex relationships that benefit both the tree and the soil.

Jad: 10:28

So when we choose native species we're kind of supporting those established partnerships.

Lilly: 10:32

Exactly. It's like choosing a dance partner who already knows the steps.

Jad: 10:35

Okay, I like that analogy. So we should really be thinking about what the soil wants when we're selecting trees.

Lilly: 10:41

Yeah, it's all about recognizing that a tree is not just an individual. It's part of a whole web of interactions.

Jad: 10:47

Right, it's part of an ecosystem.

Lilly: 10:48

Exactly, and by choosing trees that fit well with that existing soil ecosystem, we're really setting them up for success.

Jad: 10:54

Okay, so we've talked a lot about building up the soil's natural defenses, but what about situations where we're already facing challenges like soil compaction or disease pressure? How can we address those issues while still making sure that we're not harming the soil?

Lilly: 11:10

Well, even in those cases we can use soil health focused solutions. So for compaction you can use aeration techniques to help improve drainage and oxygen flow.

Jad: 11:19

OK.

Lilly: 11:19

That creates a more hospitable environment for those beneficial microbes.

Jad: 11:23

So it's like we're giving the soil the tools it needs to heal itself.

Lilly: 11:26

Exactly, and when it comes to disease, remember those disease suppressive soils we talked about.

Jad: 11:30

Yeah.

Lilly: 11:31

Well, by fostering a diverse and thriving microbial community, we can create conditions that naturally suppress pathogens.

Jad: 11:38

How do we actually do that in a practical sense though?

Lilly: 11:40

Well, diversity is key, so incorporating a variety of organic amendments, planting cover crops, choosing a mix of tree species, can all help to create a more resilient soil ecosystem.

Jad: 11:51

It's kind of like building a diverse community. It is.

Lilly: 11:54

It is when everyone has different strengths and skills the community as a whole is stronger and more adaptable.

Jad: 12:00

That's a great point. So instead of relying on chemical treatments to combat diseases, we can actually empower the soil to fight back naturally.

Lilly: 12:08

Exactly, and there are even biocontrol products available that introduce specific beneficial microbes to help combat certain pathogens.

Jad: 12:16

Oh, wow. So it's like we're recruiting a specialized team of microbes.

Lilly: 12:19

That's a good way to think about it.

Jad: 12:21

It all ties back to that one health concept, doesn't it?

Lilly: 12:23

It does the health of the soil, the plants, the animals and us humans. It's all interconnected. When we take care of the plants, the animals and us humans, it's all interconnected.

Jad: 12:28

When we take care of the soil, we're taking care of everything.

Lilly: 12:31

That's right. So, as we're wrapping up here, what are some of the key takeaways that you want our listeners to remember?

Jad: 12:37

Yeah, what are the big things?

Lilly: 12:39

Well, first of all, I want everyone to remember that soil is alive, you know, it's not just dirt, it's an ecosystem, and it's an ecosystem that supports the health of our trees and the health of our planet. So by shifting our perspective, you know, instead of just treating individual trees, let's start thinking about nurturing that entire soil ecosystem.

Jad: 12:55

The whole web. The whole web and by doing that we can unlock all kinds of benefits. You know, we can reduce our reliance on chemical inputs, we can make our trees more resilient and we can contribute to a healthier environment for everyone. Well said, it's like we've been given the keys to this amazing secret garden that's a good way to put it and now we have the knowledge and the tools to help it thrive.

Lilly: 13:16

That's right. So let's go out there and let's do it.

Jad: 13:18

This deep dive has been truly inspiring.

Lilly: 13:21

It has.

Jad: 13:22

It feels like we've not only learned a lot, we've also been reminded of just how important it is to care for this world beneath our feet.

Lilly: 13:29

And that's what it's all about, you know empowering arborists to become champions for soil health. So keep learning, keep experimenting and keep sharing your knowledge with others, because together we can create a future where healthy soil is the foundation for thriving trees and a vibrant planet.

Jad: 13:45

That's a great message to end on. Thank you so much for joining us on this deep dive into the soil microbiome. We hope you enjoyed it and we'll see you next time.

Roger: 13:56

Thank you for joining us on today's exploration of soil health and its vital connection to the One Health Framework. We've delved into the remarkable role of soil microbiomes in sustaining ecosystems and discussed how robust soil health underpins sustainability and human well-being. May these insights inspire a deeper appreciation for the intricate web of life beneath our feet. Until next time, keep nurturing the ground that sustains us. Thank you.