Roger: 0:02

Talking Trees with Lillie and Jad. Welcome to Talking Trees. Today we discuss the importance of tree interactions within forest ecosystems and their role in ecosystem functioning. The article emphasizes that understanding these interactions is crucial for effective forest restoration and the development of mixed species stands. Effective forest restoration and the development of mixed species stands. It examines both positive and negative mechanisms, ranging from resource allocation and growth facilitation to pest suppression and biotic interplay, and proposes systematic evaluations of tree interactions in diversity experiments, with the BEF China study serving as a key example.

Jad: 0:48

Welcome back everyone. We're going to be talking trees today, specifically how they interact with each other, something that's especially relevant to all you arborists out there.

Lilly: 0:54

Yeah, I think most people, when they think about trees, they think about competition, you know, fighting for sunlight and water and all that Survival of the fittest. Exactly. But there's this really interesting review article we're looking at today from Basic and Applied Ecology and it really kind of unveils this whole hidden world of positive interactions between trees.

Jad: 1:17

Yeah, and I was thinking. You know, obviously as arborists we work a lot in urban areas.

Lilly: 1:21

Right.

Jad: 1:22

And thinking about how these positive interactions can help us build more resilient urban forests is just fascinating.

Lilly: 1:29

It is, and that's really what this paper digs into. I mean, it starts by, you know, setting the scene, talking about global change, climate extremes. You know all the new pests and pathogens that are emerging.

Jad: 1:39

Yeah, we're seeing more and more of that.

Lilly: 1:40

Exactly, and they make this really compelling case for how mixed forests can actually be a key strategy for building resilience.

Jad: 1:48

Well, that makes a lot of sense. It's like diversity is kind of like a safety net, right.

Lilly: 1:51

It is Exactly. If one species is vulnerable to a particular pest or disease, having other species around can help buffer that impact. But it goes beyond resilience too, you know. Think about urban forestry, where you might be dealing with limited space, compacted soil.

Jad: 2:09

Right right.

Lilly: 2:09

If you understand the different ways that different tree species utilize resources, you can actually create a thriving little ecosystem, even in a challenging environment.

Jad: 2:18

So we're kind of moving beyond, thinking about trees, just competing, competing for the same resources. So what does this paper say about those positive interactions Like what are some examples?

Lilly: 2:31

Well, one of the most interesting findings is how these positive interactions can actually boost productivity. They suggest that in a species-rich forest, those positive interactions might actually be the dominant force leading to greater growth than previously thought.

Jad: 2:45

Wow, that's amazing. So it's not just about mitigating the negative, it's about actually actively helping each other thrive.

Lilly: 2:51

Exactly, and they actually use this term called facilitation, which I love Imagine. Like a towering oak tree, it's acting as a natural parasol, you know, sheltering a young maple sapling from the scorching summer sun. Right, that's facilitation.

Jad: 3:08

I never thought about it that way. That's a great analogy. Okay, so facilitation is one way that trees can help each other. What are some other mechanisms?

Lilly: 3:16

Well, the paper outlines four key mechanisms, and the first one is resource partitioning. Ok, and this is essentially the idea that different species have evolved to utilize resources in different ways. Some might have deep roots, others shallow roots, some might access nutrients at different times of year or specialize in utilizing, you know, different forms of nitrogen.

Jad: 3:37

So, like a deep-rooted oak could share space with a shallow-rooted dogwood, because they're not tapping into the same water source.

Lilly: 3:45

Exactly, and knowing this is crucial when you're planning a planting. You know, imagine you're working with a site that has very limited soil depth. You can strategically pair species so they're not competing for the same precious resources.

Jad: 3:57

It's like designing a team. You know you want to make sure each player has a unique role.

Lilly: 4:01

Right. And then you have the dilution effect, which I know you're familiar with.

Jad: 4:05

Right the idea that diversity can help reduce the spread of pests and pathogens.

Lilly: 4:10

Exactly. We all know that monocultures are incredibly vulnerable.

Jad: 4:14

Oh yeah, if one tree gets hit, the whole stand can be wiped out.

Lilly: 4:17

It's like putting all your eggs in one basket, but when you have a diversity of species, it's much harder for a pest or disease to spread like wildfire.

Jad: 4:25

Oh right, Because they might encounter a tree that's resistant.

Lilly: 4:27

Exactly, and it's not just about slowing the spread. Having a variety of species also supports a greater diversity of beneficial insects and organisms, so it's like building this natural defense system for your trees.

Jad: 4:42

Right. I mean you're creating a healthier ecosystem overall, exactly OK. So we've got resource partitioning, we've got facilitation, we've got the dilution effect. What's the fourth mechanism?

Lilly: 4:52

The fourth one is biotic feedbacks. The fourth one is biotic feedbacks, and this is where it gets really fascinating, I think, because it's all about how these diverse tree communities foster a complex web of organisms predators, parasites, mycorrhizal fungi. Ok, now break that down for me a little bit. You're setting the stage for this complex, self-regulating ecosystem.

Jad: 5:33

Yeah, that's incredible. So it's like a ripple effect.

Lilly: 5:35

Exactly.

Jad: 5:36

The more diversity you have, the more benefits you create throughout the whole system.

Lilly: 5:40

It's a beautiful thing.

Jad: 5:41

It's like we're building this more robust ecosystem just by having a greater diversity of trees.

Lilly: 5:46

Absolutely. And you know, the thing is, these interactions don't just happen in isolation. The paper talks about what they call higher order interactions. It's not as simple as A plus B equals C, you know.

Jad: 5:58

Right.

Lilly: 5:58

You can have these multiple positive interactions all happening at the same time and it creates this cascade of benefits.

Jad: 6:05

It's more like a web. You know this complex dance between different species in their surroundings.

Lilly: 6:12

And sometimes those positive interactions can even outweigh the negative ones.

Jad: 6:16

I'm trying to imagine, like how that might play out in an urban setting. You have a street tree planted in this tiny little opening surrounded by a pavement.

Lilly: 6:24

Right.

Jad: 6:25

It's got to be competing with its neighbors for water and nutrients. But then at the same time, you know, maybe the buildings are providing some protection from wind or frost and maybe that tree attracts beneficial insects that also help protect the trees nearby from pests.

Lilly: 6:41

Exactly so. Even in a really challenging, tough environment like that, you still have this potential for these positive interactions to really make a difference.

Jad: 6:50

Yeah, it's making me think about urban forestry in a whole new way.

Lilly: 6:54

That's what's so exciting about this research it's calling for a real paradigm shift in how we approach designing and managing these urban forests. You know, it's not just about planting trees, it's about fostering these interactions. It's about creating these communities of trees that can actually support each other.

Jad: 7:12

I know the paper talks about this really fascinating experiment in China, BEF China.

Lilly: 7:16

Oh, china, bef China. Oh yeah, bef China, which is looking at these interactions in a forest setting. Can you tell us a little bit more about that? Yeah, so BEF China is the world's largest tree diversity experiment. It's in subtropical China and they're basically planting all sorts of different tree species in various combinations. They're looking at tree pairs, they're looking at whole neighborhoods of trees across all these different levels of diversity. It's really an incredible undertaking.

Jad: 7:41

That sounds massive.

Lilly: 7:42

It is.

Jad: 7:43

But I'm wondering what can we, as urban foresters learn From an experiment that's happening in a subtropical forest halfway across the world?

Lilly: 7:52

Well, one of the most amazing findings from BF China is that planting trees in these groups of five, with a mix of different species, it can actually boost growth by 20 percent compared to monocultures. Wow, and now think about, you know, applying that to your next park design, or even just a small little planting strip between a sidewalk and a road 20 percent.

Jad: 8:12

That's significant. It's making me see all those those little planting strips in a whole new light.

Lilly: 8:17

Exactly. It's all about maximizing the benefits of every single space that we have. Even in the most confined environments, we can still create these resilient little communities of trees by by understanding and harnessing those positive interactions.

Jad: 8:33

Yeah, this is really eye-opening. I'm starting to see positive interactions everywhere. Now I'm looking at the trees outside my window in a whole new way.

Lilly: 8:41

I know it's like this whole secret world has been revealed, right it?

Jad: 8:44

really is. So for our listeners out there, those arborists who are working in the field, every day.

Lilly: 9:03

What would you say is the most important action they can take? Based on what we've talked about today, Are there ways you can use resource partitioning in your planting plans? You know, really start to see the forest for the trees, so to speak.

Jad: 9:18

So it's about observation, becoming more aware of these interactions happening in the real world.

Lilly: 9:25

Exactly, and once you start seeing them, you can start managing for them, you can start creating these even more resilient and thriving urban forests.

Jad: 9:35

I feel like I'm looking at urban forests through a whole new lens now. All these connections I never really paid attention to before.

Lilly: 9:41

Yeah, it's like the secret language has been revealed, you know.

Jad: 9:44

Yeah, exactly. So for our listeners out there, those arborists who are working hard out in the field, what would you say is like the most important thing they can do, based on what we've talked about?

Lilly: 9:56

You know, I think the biggest takeaway is that we really need to start challenging our assumptions. When you go out to a site, don't just look at those individual trees, you know. Look for those interactions, look for the way they're talking to each other. Are there examples of facilitation that are happening naturally? Are there places where you can use resource partitioning in your planting plans? You know, really start to see the forest for the trees.

Jad: 10:23

So it's about observation right, Like becoming more aware of these interactions that are already happening out there.

Lilly: 10:28

Absolutely, and once you start to see them, then you can start to manage for them, and that's how we can create these truly resilient and thriving urban forests, you know, urban forests that can handle all the challenges that are coming their way.

Jad: 10:44

And I know our listeners are always, you know, hungry for more knowledge. What are some resources that they could explore if they want to really dive deeper into this topic?

Lilly: 10:53

Well, I mean obviously this this review article we've been discussing from basic and applied ecology is a great starting point. They lay out, you know all the the key mechanisms, the latest research and you know keep an eye on what's coming out of BF China.

Jad: 11:08

Right.

Lilly: 11:08

Even though it's a forest setting. You know a lot of the principles that they're they're uncovering are are definitely applicable to urban environments as well.

Jad: 11:17

Yeah, for sure, and we'll. We'll be sure to keep our listeners updated on any any really interesting findings that come out of come out of BF.

Lilly: 11:25

China a future episode where we dive into some specific tree pairings that work really well together in urban settings or talk about how to apply some of these principles to challenges like managing trees in really confined spaces or dealing with invasive species.

Jad: 11:45

Ooh, I love those ideas.

Lilly: 11:46

Yeah.

Jad: 11:46

Yeah, we're always looking for ways to bring the latest research to our listeners and help them tackle those real-world challenges. To all of our arborist listeners out there, keep those questions coming in and keep observing, keep pushing the boundaries of what's possible.

Lilly: 12:02

Until next time.

Roger: 12:07

Thank you for joining us on this episode of Talking Trees. Today, we explored the critical role of tree interactions in forest ecosystems, focusing on their impact on forest restoration and mixed species stand establishment. We discussed positive and negative mechanisms, including resource sharing, pest suppression and biotic interactions, and reviewed the BF China study as a model for understanding ecosystem balance through tree diversity. We look forward to further discussions in future episodes.