Roger: 0:02

Talking Trees with Lily and Jad. Welcome to today's episode. We're exploring the fascinating concept of compartmentalization in trees, their natural defense system against insects, diseases and infections. We'll look at how trees respond to wounds, form barrier zones and heal, as well as the role of cavities in overall tree health. We'll also dive into the CODIT model, a framework for understanding how compartmentalization impacts insect and fungal development in trees. Let's get into it.

Jad: 0:40

Trees, these silent giants. They just stand tall for decades.

Lilly: 0:44

Yeah.

Jad: 0:45

Some even for centuries, exposed to the elements, pests, you know, even us humans.

Roger: 0:51

Oh yeah.

Jad: 0:52

Damaging them, but have you ever wondered how they managed to survive?

Lilly: 0:56

A fascinating question.

Jad: 0:58

All that time.

Lilly: 0:58

One that scientists have been exploring for quite some time. Unlike animals, trees can't heal in the conventional sense.

Jad: 1:07

Right.

Lilly: 1:07

They can't simply replace damaged tissue.

Jad: 1:11

Okay, so how do they deal with the lifetime of wounds and potential infections? Right, what's their their secret lies. Secret weapon.

Lilly: 1:20

In a remarkable process called compartmentalization. Okay, a dynamic defense system. Compartmentalization, it's key toalization.

Jad: 1:25

Okay, a dynamic defense system Compartmentalization.

Lilly: 1:27

It's key to their longevity.

Jad: 1:29

Okay, yeah, sounds intriguing.

Lilly: 1:31

Well, think of it this way, tell me more. A tree is constantly strengthening its existing boundaries and creating new ones to isolate any damage.

Jad: 1:40

This is where the CODI model comes in.

Lilly: 1:42

This is where the CODI model comes in. Yeah, Okay. Which stands for compartmentalization of decay in trees.

Jad: 1:47

Got it.

Lilly: 1:49

It was developed by Dr Alex Shigo Okay Back in the 1980s and it revolutionized our understanding of how trees defend themselves.

Jad: 1:58

CODI, codi, got it, got it. So this deep dive is going to be all about precisely understanding this model.

Lilly: 2:04

We'll be taking a close look at Shugo's research, really getting into the nitty gritty of how these defense mechanisms work. We'll also touch upon the CODI principle, which expands on Shugo's original work.

Jad: 2:18

Okay, I'm ready to dive in. Let's start with the basics. Why is it so crucial for trees to have this defense system? What are they up against?

Lilly: 2:25

Well, trees, like all living organisms, are constantly under attack. Right Fungi, bacteria, insects, all sorts of things, get in and take advantage of their resources, so it's a constant battle for survival. It is, and because trees can't replace damaged tissue, they need a way to contain those threats and prevent them from spreading.

Jad: 2:49

So that's where compartmentalization comes in.

Lilly: 2:51

That is where compartmentalization comes in.

Jad: 2:53

yes, but you mentioned it's different from healing.

Lilly: 2:56

Yes.

Jad: 2:57

Can you explain?

Lilly: 2:58

Think of it this way If you get a cut, your body will heal by replacing the damaged tissue with new, healthy tissue.

Jad: 3:05

Right.

Lilly: 3:06

Trees, on the other hand, can't do that. Instead, they compartmentalize, which means they create barriers to wall off the damaged area and prevent the spread of decay.

Jad: 3:17

So it's more about containment than repair.

Lilly: 3:19

Exactly. They're essentially sacrificing a small part of themselves to protect the whole organism.

Jad: 3:25

That's pretty incredible.

Lilly: 3:26

Yeah.

Jad: 3:27

So how does this compartmentalization process actually work? What are these barriers made of?

Lilly: 3:32

Well, Shigo's model describes four distinct walls that make up this defense system. Okay, they're not physical walls, of course but, rather zones within the tree where chemical and structural changes occur.

Jad: 3:45

Okay, four walls.

Lilly: 3:46

Yes.

Jad: 3:47

I'm intrigued. Tell me about wall one.

Lilly: 3:49

Wall one. The first line of defense focuses on resisting the vertical spread of decay.

Jad: 3:55

Okay.

Lilly: 3:56

It primarily involves plugging up the tree's vascular system.

Jad: 3:59

Like the channels that transport water and nutrients throughout the tree.

Lilly: 4:03

Exactly so. Imagine it like this yeah. When decay sets in.

Jad: 4:06

Okay.

Lilly: 4:07

The tree reacts by plugging up those vessels and trachides Uh-huh. This slows down movement of any invading microorganisms.

Jad: 4:15

So it's like shutting down a highway to prevent invaders from reaching the city.

Lilly: 4:20

A great analogy.

Jad: 4:21

Yeah.

Lilly: 4:21

The tree is essentially sacrificing some transport capacity to prevent further spread.

Jad: 4:27

Clever. What about wall two? What's its role in this defense strategy?

Lilly: 4:32

Wall two is all about resisting inward spread.

Jad: 4:36

Okay.

Lilly: 4:37

It utilizes the structure of the tree's annual growth ring.

Jad: 4:41

Each ring represents a year of growth.

Lilly: 4:43

And those rings are more than just markers of time. They play a critical role in defense.

Jad: 4:48

Okay.

Lilly: 4:49

You see, each ring acts as a fortified barrier making it difficult for decay to penetrate deeper into the tree. And this inward protection is enhanced by chemical changes in the cells of each ring, making them less hospitable to invaders. Oh, that's amazing. It's amazing how much is going on beneath the bark of each ring making them less hospitable to invaders.

Jad: 5:05

Oh, that's amazing. It's amazing how much is going on beneath the bark of a tree.

Lilly: 5:09

Truly remarkable. Yeah, and we're just getting started. Let's move on to wall three, which is considered the strongest of the pre-existing walls.

Jad: 5:16

Okay, Wall three the strong one. The strong one. What makes it so tough?

Lilly: 5:19

Wall three focuses on resisting lateral spread, preventing the decay from expanding sideways within the tree.

Jad: 5:26

Okay.

Lilly: 5:27

It relies on specialized cells called ray parenchyma cells.

Jad: 5:31

Ray parenchyma cells, those are part of the tree structure right.

Lilly: 5:33

They form tough boundaries within the wood running perpendicular to the growth rings. Internal brick walls.

Jad: 5:42

Oh, so they're like the reinforcement beams in a building.

Lilly: 5:44

A perfect analogy. These ray parenchyma cells are incredibly effective at stopping lateral spread, keeping the decay confined.

Jad: 5:54

But you mentioned earlier that sometimes this wall, wall three, can fail.

Lilly: 6:00

What happens then when wall three fails? It often leads to the formation of hollows in trees.

Jad: 6:07

So those hollow trees you sometimes see, that's often due to a breach in wall three.

Lilly: 6:12

And while you might think a hollow tree is a dying tree, that's not always the case. Often, the tree can survive for a surprisingly long time with a large hollow. In fact, those hollows can become valuable habitats for wildlife.

Jad: 6:27

So even in failure, nature finds a way to create something beneficial Exactly. It's a win-win for the tree and the ecosystem.

Lilly: 6:35

Yeah.

Jad: 6:36

Now what about the fourth wall?

Lilly: 6:38

Right.

Jad: 6:38

The one that forms after injury, also known as the barrier zone, is unique because it forms as a direct response to injury.

Lilly: 6:46

Oh OK.

Jad: 6:47

It's not a pre-existing wall, like the first three Gotcha, but rather a new layer that the tree creates, separate the infected wood from any new growth that occurs. So it's like the tree is saying, ok, damage is done, but from this point on we're building a fresh start.

Lilly: 7:04

That's a great way to put it, and scientifically speaking, this barrier zone is composed of cells lined with a substance called suberin.

Jad: 7:13

Isn't that a key ingredient in cork?

Lilly: 7:15

You're absolutely right.

Jad: 7:17

Oh, wow.

Lilly: 7:18

Suberin is what makes cork so waterproof and resistant to decay.

Jad: 7:23

Right yeah.

Lilly: 7:23

And trees use this same substance to create an incredibly effective barrier against the spread of infection.

Jad: 7:32

It's like the tree is building its own internal cork barrier.

Lilly: 7:34

Yeah.

Jad: 7:35

So let me get this straight We've got these four walls.

Lilly: 7:38

Yes.

Jad: 7:38

Wall one slows down the vertical spread. Right Wall two, which resists inward spread.

Lilly: 7:44

Right.

Jad: 7:44

Wall three, which is the strongest. The strongest and stops lateral spread.

Lilly: 7:46

Right Wall two, which resists inward spread Right Wall three, which is the strongest? The strongest.

Jad: 7:47

And stops lateral, spread Correct and then wall four this remarkable barrier zone that forms after an injury. Right, it's an amazing system.

Lilly: 7:56

It truly is, and understanding how these walls work, both individually and as a system, is fundamental to understanding how trees survive and thrive despite constant challenges.

Jad: 8:08

This is also fascinating.

Lilly: 8:09

It is.

Jad: 8:10

But before we move on, I'm curious about the limitations of compartmentalization. Are there cases where this system isn't enough to protect the tree?

Lilly: 8:19

That's a great question, and it leads us to some of the criticisms of the CODAT model. You see, while compartmentalization is remarkably effective in most cases, it's not foolproof. So there are situations where even the mighty tree's defenses can be overwhelmed. Some critics argue that compartmentalization might not be as effective in dealing with very large wounds or when the tree is attacked by particularly aggressive pathogens.

Jad: 8:46

Okay. So it's like any defense system, it has its limits.

Lilly: 8:49

But even with these limitations, the coded model remains a powerful tool for understanding how trees respond to injury and decay.

Jad: 8:59

I can already see how this knowledge could be incredibly valuable Anyone working with trees.

Lilly: 9:04

Understanding the principles of CODIT can inform everything from pruning practices to risk assessment.

Jad: 9:11

Yeah Well, I'm eager to learn more about those practical applications.

Lilly: 9:14

Okay.

Jad: 9:15

But before we get into that, you mentioned earlier that there's another concept, the concept Right, the coded principle yes, which builds upon the original coded model Right. Can you tell me more about that?

Lilly: 9:25

Of course, the coded principle developed by Dirk Dujazivkin.

Jad: 9:29

OK.

Lilly: 9:29

Takes a broader look at the tree's response to injury, focusing on the dynamic process that unfolds over time.

Jad: 9:37

So it's not just about the walls themselves, but how the tree reacts and adapts to the damage over time.

Lilly: 9:43

Exactly the Cody principle describes four distinct phases.

Jad: 9:47

Okay, four phases.

Lilly: 9:48

That occur as the tree attempts to encapsulate the damaged area.

Jad: 9:52

Can you break those down for me?

Lilly: 9:54

Absolutely. The first phase involves those immediate reactions we discussed earlier. Okay, the changes in wood chemistry, the plugging of the vascular system Right. The first phase involves those immediate reactions we discussed earlier the changes in wood chemistry, the plugging of the vascular system Right. These are the first lines of defense.

Jad: 10:06

So it's all about containing the damage right from the start. Exactly Okay.

Lilly: 10:10

The second phase is all about the formation of that remarkable barrier zone, wall four.

Jad: 10:15

Yeah.

Lilly: 10:20

It's the tree's way, creating a clear separation between the infected wood and the new growth that follows. Now the third phase is where things get really interesting. This is where the tree actively tries to push out the damaged tissue.

Jad: 10:32

How, does it? Do that.

Lilly: 10:33

By forming callus, tissue, callus tissue. You know how you sometimes see a tree forming a swollen area around a wound.

Jad: 10:41

Yeah, yeah.

Lilly: 10:41

That's callus tissue and it's the tree's way of trying to expel the infection.

Jad: 10:45

It's almost like the tree is trying to shed the damaged part like a scab.

Lilly: 10:49

That's a good analogy.

Jad: 10:50

Yeah.

Lilly: 10:50

And finally, the fourth phase is full encapsulation.

Jad: 10:54

Full encapsulation.

Lilly: 10:55

This is where the wound is completely sealed off and the new growth continues over the damaged area.

Jad: 11:02

So it's a gradual process, with the tree actively working to contain and eventually seal off the damaged area.

Lilly: 11:09

Exactly, and the CODIT principle helps us understand the dynamic nature of this process, which can vary depending on the type of injury, the tree species and environmental factors. Knowing how the tree reacts over time can help arborists make more informed decisions about pruning, wound care and risk assessment.

Jad: 11:30

Well, I'm eager to delve deeper into those practical applications. All right, okay, so we've got this solid foundation of the CODIT model and the CODIT principle. Okay, so we've got this solid foundation of the coded model and the coded principle, yes, but I'm really curious to see how this all plays out in real life. Can we dive into some specific examples of compartmentalization in action?

Lilly: 11:51

Let's start with something everyone's familiar with.

Jad: 11:52

Okay, branches.

Lilly: 11:53

When a branch dies, whether it's from natural causes, storm damage or pruning, the tree needs to protect itself from the decay spreading into the main trunk and this is where that branch collar comes in. The branch collar, you know that slightly swollen area at the base of a branch, that collar is actually packed with specialized cells that are primed and ready to form a barrier zone. When the branch dies, the tree activates these cells and they swing into action, creating that crucial wall.

Jad: 12:27

Four so it's like a built-in emergency response team.

Lilly: 12:30

Exactly.

Jad: 12:31

Ready to seal off the breach?

Lilly: 12:33

And you'll often see evidence of this compartmentalization.

Roger: 12:36

Oh, okay.

Lilly: 12:37

If you look closely at a dead branch, you'll notice that the decay is mostly contained within the branch itself, not spreading into the trunk.

Jad: 12:45

It's fascinating to think about all this happening silently within the tree.

Lilly: 12:49

It is.

Jad: 12:50

But I'm guessing the fungus doesn't always give up so easily.

Lilly: 12:53

Unfortunately, you're right.

Jad: 12:54

Yeah.

Lilly: 12:55

But even then, the tree is still using compartmentalization to limit the spread of the infection and protect itself.

Jad: 13:04

So even in a long-term battle, the tree is still fighting to survive.

Lilly: 13:07

Yes.

Jad: 13:07

Now what about the roots? Roots Does compartmentalization happen in roots too?

Lilly: 13:12

It's crucial in roots. Compartmentalization in roots is essential for maintaining the tree's stability in roots is essential for maintaining the tree's stability. Remember, the roots are the tree's foundation, anchoring it to the ground and absorbing water and nutrients, so the roots are compromised.

Jad: 13:27

Exactly the whole tree's at risk.

Lilly: 13:29

And that's why understanding compartmentalization in roots is so important, especially for professionals who might be assessing root damage from construction or other impacts.

Jad: 13:38

It makes you realize how vulnerable trees can be. They are vulnerable To things we might not even see Absolutely Now shifting gears a bit. We talked about limitations of the Code 8 model earlier. Yeah, I'm curious to hear more about those criticisms, sure, and how they might impact our understanding of tree care.

Lilly: 13:55

You're right. It's important to acknowledge that, while coded is a powerful model, it's not without its critics. Yeah, some researchers argue that it oversimplifies a complex biological process, and there's ongoing debate about the effectiveness of compartmentalization in certain situations. Can you give us an example? Sure, one area of contention is the ability of compartmentalization to effectively contain decay in very large wounds. Think of a tree that's been struck by lightning or has suffered significant damage from a construction project. These massive wounds can overwhelm the tree's defenses, making it more susceptible to decay.

Jad: 14:35

So it's like the size of the breed sometimes exceed the tree's ability to contain it.

Lilly: 14:39

And another point of debate is the effectiveness of compartmentalization against certain aggressive pathogens.

Jad: 14:46

Oh right.

Lilly: 14:47

Some fungi and bacteria have evolved ways to overcome the tree's defenses, making it difficult for the tree to effectively isolate the infection.

Jad: 14:57

So it's an ongoing evolutionary arms race, precisely Between the tree and its attackers.

Lilly: 15:02

And this is why it's crucial for professionals working with trees to stay up to date on the latest research and to understand the nuances of compartmentalization.

Jad: 15:12

It's a reminder that nature is incredibly complex.

Lilly: 15:15

Yeah.

Jad: 15:15

And we're constantly learning new things.

Lilly: 15:17

Yes.

Jad: 15:18

Now, you mentioned that the COAT principle Right Developed by Dirk Dujasiefkin. Yeah, and we're constantly learning new things. Yes, now you mentioned that the COAT principle Right Developed by Dirk Dujasiefkin.

Lilly: 15:23

Yes.

Jad: 15:23

Provides a broader perspective on the tree's response to injury.

Lilly: 15:26

It does.

Jad: 15:27

Can we delve a little deeper into how that principle can be applied in practical settings?

Lilly: 15:32

The COAT principle is incredibly valuable Right Because it emphasizes the dynamic and ongoing nature. Yeah of the tree's response. It's not a one-time event. It's a process that unfolds over time.

Jad: 15:45

So it's not enough to just know about the four walls. We need to understand how they interact and how the tree adapts over time.

Lilly: 15:52

Exactly, and this understanding can inform a wide range of tree care practices.

Jad: 15:57

Okay, like what.

Lilly: 15:58

For example, when it comes to pruning, the Coda T principle emphasizes the importance of making proper cuts to minimize the size of the wound and to encourage the formation of that all-important barrier zone.

Jad: 16:12

So it's not just about removing a branch. It's about understanding how the tree will respond to that cut and how we can help it compartmentalize effectively.

Lilly: 16:22

Precisely, and this knowledge can also inform decisions about wound care.

Jad: 16:27

Wound care.

Lilly: 16:27

For instance, knowing how the tree forms callus tissue Right and attempts to push out decay can help us determine the best approach.

Roger: 16:36

Yeah.

Lilly: 16:36

To treating wounds, and this understanding can also be applied to risk assessment.

Jad: 16:40

Risk assessment.

Lilly: 16:41

By evaluating the size and location of wounds, the tree species and the surrounding environment, professionals can make more informed decisions about the potential for decay and the risk of failure.

Jad: 16:54

So it's about taking a holistic approach, considering all the factors.

Lilly: 16:57

And this is where the CODIT principle really shines. Okay, because it provides a framework for thinking about the tree's response.

Roger: 17:04

Yeah.

Jad: 17:11

In a dynamic and nuanced way. So to summarize, okay, we've explored the world of compartmentalization we have, from the four walls of defense to the dynamic phases described by the CODIT principle. We've also touched upon some of the criticisms and limitations of the model, highlighting the need for ongoing research and a nuanced understanding of this complex process. And we've seen how this knowledge can be applied in practical settings, from pruning and wound care to risk assessment, to make informed decisions that promote tree health and longevity.

Lilly: 17:39

Absolutely.

Jad: 17:39

It's been an incredible journey into the inner workings of trees.

Lilly: 17:43

It has.

Jad: 17:45

This has been such an eye-opening deep dive. We've gone from the microscopic level of wood structure and cellular defenses to the macro level of forest management and urban planning. And it all comes back to this remarkable concept of compartmentalization.

Lilly: 17:58

And I think the key takeaway here is that trees are not passive victims.

Jad: 18:03

Right.

Lilly: 18:04

They are active participants in their own survival. They have evolved these incredible defense mechanisms that have allowed them to thrive for millions of years.

Jad: 18:15

And our role as those who study and care for trees, understand those defenses and to work with them to promote the health and resilience of these vital ecosystems.

Lilly: 18:23

Well said.

Jad: 18:24

I think that's a perfect note to end on.

Lilly: 18:26

I think so too.

Jad: 18:27

Well, folks, there you have it A deep dive into the world of CODIT, the CODIT principle and the amazing ways trees defend themselves. We hope you've gained a newfound appreciation for the silent strength and complexity of these remarkable organisms. And the next time you see a tree, take a moment to ponder the intricate world beneath the bark, A world of resilience, adaptation and constant defense.

Roger: 18:57

Thanks for tuning in. We hope you enjoyed today's journey into the protective mechanisms that trees use to defend themselves and stay resilient. Compartmentalization is a powerful reminder of how complex and adaptive trees truly are. Don't forget to join us next time for more insights into the world of trees. Until then, keep appreciating the strength and resilience of the forests around us.