Joshua Ginsberg 0:00
Happy to be introducing my colleague, Amy Zanne. Amy joined Cary Institute last year, and it's been a real pleasure to get to know her. She came. We poached her from Florida. She came to the cold northeast from the warm southeast, in part, her mother, who's here tonight, who lives in New Hampshire, helped lure her back, but fundamentally, Amy came here because her work fits so well with what we do at the Cary Institute. Before being the arrestee chair in Tropical Ecology Florida, she was a research professor at George Washington University, so she's got a great track record, and it is a pleasure to have her here. A lot of what for a lot of what Amy does. The currency of her work is carbon, and it's really important these days. I think everybody understands the importance of carbon and carbon sequestration and its relationship to climate change. What a lot of people don't know is how, I won't say ignorant, because that overstates it, but how much we don't know about the natural pieces of the carbon cycle? We can tell you there three and a half billion metric tons of carbon are emitted by cars every year. But the accuracy and the knowledge we have about all the natural processes is much less specific, and so Amy is working to look at carbon in forests and savannas and tropical, temperate, Antarctic environments, and she looks at carbon, particularly carbon that's stored in plants. And most ecologists study things that are living, and what Amy is particularly fascinated by and what we will talk about tonight is what happens when they die? So it is my pleasure to introduce Amy Zan and she and I will go sit down and have a conversation about the afterlife of trees. Thank you for coming.
Joshua Ginsberg 1:58
All right. My cards are with me. And the good news is I don't have to look around to see what slide we're on, because I have pictures of the slides. Thank you. Mary Beth, we'll go to the first slide. So, as I mentioned, when people think of ecology, they think of births and deaths. And you know how animals survive and plants survive, and how ecosystems are structured. And we usually think of the living right, but you tend to focus on the dead, right, and it's particularly appropriate given that Halloween is next Friday. But you know what put you on the path of this? And how does one become an ecologist who realizes that once things die, they have a whole nother life?
Amy Zanne 2:45
Great. Well, thanks so much for coming today. It's a pleasure to be here with you and to have a conversation with Josh. And so you can see a picture of me there, and the I guess your left side of the screen, that's me as a grad student, where I was studying trees in Uganda and so I spent a lot of time trying to understand how trees were constructed to live in different parts of the world. And so that was about their life. And so I worked on seedlings there in my seedling nursery, and then in my post doc, I studied, started really focusing on wood and trying to understand the construction of wood. So wood has three major jobs. One of them is it has to transport resources from the roots up to the leaves and then backwards. And so you can see those holes in that cross section on the middle left. So those those holes are the pipes that allow water to move up from the roots to the leaves. The bigger those pipes, the faster the flow. But also they can be more at risk of getting air bubbles embolism, sort of like if we go diving and get the bends, those air bubbles can block the flow, and so bigger vessels can be at risk for definitely freezing and possibly drought can cause problems. So I looked at the trade offs in the vessels. But another job that plants have to do is that they have to hold their branches high above the ground so that they can photosynthesize and compete for light. And so they need to have strong mechanical support. So there's lots of fibers in that cross section, and then they have to store resources, water, nutrients, carbon, and so there's various tissues there, parenchym and things like that. So I spent a lot of time thinking about this construction for life, especially contrasting how plants are built to move water in wet versus dry places. I learned along the way that I was a pretty bad ecophysiologist to move water. I had lots of explosions of water trying to push water at high pressure through stems. And I increasingly found myself interested in the afterlife consequences of that construction and so things like along the way, I was studying the chemistry. So you can see on the other side that wood is comprised of half of its carbon. So it's an incredibly carbon rich tissue. The bulk of that carbon, or the number one polymer, is cellulose, but followed by lignin, and then also hemicellulose and some pectins and things. Lignin is this incredibly hard structure. It's you can see. In the picture over here, it forms this crystalline matrix that gives rigid rigidity and structure. It's why we like to use wood to build houses. So trees use it so that they can stand upright and have that mechanical strength. And so I started really thinking about, what are the afterlife consequences of this construction for how plants live after they or how they function after they die.
Joshua Ginsberg 5:22
So you were trying to push water uphill, as it were, or up tree. And I was gonna have to ask you later, what happens when water explodes in a tree. But so you got focused on what happens with all these wonderful things after they die? Why is that interesting?
Amy Zanne 5:44
Yes. So why should we care about dead wood? Well, if anybody has ever walked around the forest and started pulling apart a log that's rotting on the ground, you'll see lots of things in there. So Deadwood is incredibly important for life. There's a whole other life once trees die, lots of birds use these as places to nest and to roost. Or the woodpeckers put their acorns into trees. You have a rich diversity of insects and amphibians. Or herps. I've found, I've found snakes and lizards in Deadwood. So there's a whole community of organisms that live and interact have food webs in in trees. So they're incredibly important for organisms to live and to die in. It's also incredibly important as a carbon store. So I said that half of wood is is carbon, half of the biomass and, and, and so you can see numbers up there about just how much carbon is stored, and also how much carbon is likely cycled. These are really rough estimates of the amount that is lost from wood each year. And those numbers might seem huge, but you don't quite know what they mean. Well, there's as much there's as much carbon stored in vegetation, or there's about half of the amount of carbon stored in vegetation as is up in the air. So you think about how we're always talking about greenhouse gasses, and how we respire CO two, and these different methane, these different greenhouse gasses. So there's as much half as much carbon in the in the vegetation as up in the atmosphere. So huge stores of carbon there. And it's fine. These are natural processes for plants to to cycle carbon. But as with climate change, as we start perturbing these, these pools, we can lead to to the speeding up of these, these cyclings and releases, which might have feed positive feedbacks with climate change. So it's really important to understand these pools, but there's a lot of pieces, as Josh said, that we don't know. And I found that I really like to look at the things that are underseen, under loved, often pretty hidden. And looking at Deadwood is one of those. And I think that's the third thing is that a lot of people follow like to think about the green food web. How do plants fix carbon? How do they grow? How do herbivores eat the leaves? And but there's a whole other brown food web, where you have the decomposers, the SAP probes, the things that decay the wood, that are incredibly important. And a lot of people think, Oh, they are yucky or they're hard to see there. You don't often see them, because they're doing this in hidden places, but they're incredibly important. And so I was just recently hiking with my mom and my friend Mark goes here last week in New Hampshire, and we were going down this really steep part, and you could just see the sea of leaves that we are our feet were skimming down, and it's really hard to see your feet, and it's really slippery and and so this is just one year's one year's fall leaf, leaf dropping. If we didn't have decomposers that would build up year after year after year. It's incredibly important that decomposition that happens in winter and spring, and so we would be literally swimming in a sea of dead carcasses, both animals, plants, fungi, if we didn't have the decayers. So it's an incredibly important process that we should really learn and appreciate about the world.
Joshua Ginsberg 8:58
It's a fine thing we have decayers, because no one would like that. You know, I was talking to you earlier, and I said I remember reading about the history of Australia when they brought lots of ungulates there, basically sheep, and all of a sudden they didn't have dung beetles. And because the ecosystem was not adapted or designed to deal with all that poop, the poop started accruing pretty quickly. So it's really important for all the things that we don't want to step in that something eats them, all right. And so the question I have for you is, you know, how do you look at when you when you look at Wood decaying? What are the all the various factories that lead to the decay of wood, and how do they intersect with each other? And how do you separate them out?
Amy Zanne 9:41
Yes, so there's, there's several interesting and interacting factors, the primary players. And it took me a little while to get to this. I started with the plant traits, but it really the players are the decayers. And so knowing who's there and around the world and how they work is incredibly important. Important. So there's two basic groups. You have, the the abiotic, the nonliving. And so there's a number of things. Fire is one of those sunlight, solar radiations. If you ever think about you have your favorite blue t shirt, and you wear it outside all the time, and all of a sudden, or you notice that it's starting to become a dull gray. That's because that your T shirt, that blue, has photo, decorative properties. And so the sunlight is degrading them. And so sunlight can be something that degrades plant material. You can also have freeze, thaw vents or leaching. And so a number of nonliving things, the other which is where I've mainly focused, are the living things. And so microbes, especially fungi are globally the most important decayer, because you find them everywhere you go. I found a good friend studies them. In Antarctica, we study them. They're the most common thing here in temperate forests. And so everywhere you find microbes, especially the fungi as decayers. The other are insects. And insects can become really important in certain places in the world, and so termites, especially are we find wood decayed termites all the way up to around the Canadian border, but they're most abundant and diverse in the tropics. And so it's really important to think of who's there, because they can have really different ways that they decompose, and they're also differently sensitive to different other factors, and those other factors, one of them are the wood traits. And so this was my gateway into studying wood decay. Was thinking about how the traits control the decay. And most of what we know is about the microbial decomposition, the fungal decomposition. Probably part of that is that most of us, who are scientists, we tend to be in temperate places, and so there's a lot of research dollars that go into understanding decay, and it's microbial decay because, because it's in our backyards. So you have traits such as the higher amount of carbon, especially as lignin is means slower decay, higher or lower nutrients also slower decay, nutrients like nitrogen and phosphorus, the same thing you put out as fertilizer and denser wood is often slower decaying. And so the plant, the wood traits, really matter. The other thing that really matters is the environmental conditions. And so a lot of what I've looked at is temperature and precipitation. So if you've ever made your peanut butter sandwich in your counter in a hot summer day, hot, moist summer day, and you drop it, or it falls, or you lose it for a while, you find it again, and it's covered with mold that's fungal decomposition happening there for you, if you instead, had remembered and stuck it in the fridge where it's cold and dry, it slows things down, so microbial fungal decay is faster in warm, wet places. We know that termites, like the tropics, are most diverse there, so we think that they're also sensitive to environmental conditions, but they have all these really amazing adaptations. They build and live in mounds. They have tubes that they build and things like that that protect them from the predators, but also environmental conditions. So that we think maybe they are better at dry conditions than microbes.
Joshua Ginsberg 13:03
So cold, dry and hard are the three factors that make it slow down, yep, and then the hot, wet and less hard, which is often lower, softer, yeah, less carbon and more nutrients, more nutrients. All right, so you mentioned termites, you mentioned fungi. And I think most of us around here think of termites from the perspective of the two or three species that eat our houses. But can you talk a little bit more about the differences between what each of those might do and how they might do it.
Amy Zanne 13:41
And I think, Well, I'll start by talking a little bit about the relative importance, yes, yes, contrasting them. So there's they're incredible in their diversity and what we do and don't know about them. So here you have some amazing photos of fungi. So there's dead man's fingers, apropos for our upcoming holiday. And you also have Jack O' Lantern mushrooms. And so the jack lantern mushrooms glow in the dark. They're pretty incredible. And these are both found in the forest around here. These are both saprobes. They're both decayers. There's, if you might say, fungi or small or what do they contribute? Well, they're incredibly diverse. So there's about two to 4 million species. Possibly have also seen estimates that are 100 fold bigger than that. So they're incredibly diverse, but we only know about a small fraction of them. They're so tiny that they're often sitting in places where we haven't discovered them yet. We call this the dark diversity of all these fungi that we've yet to discover. And know what they do in the world. They're also, you might also say, oh, a given mushroom doesn't weigh very much, but if you add up all of the biomass of the fungi around the world, there's six times the biomass, total biomass and fungi, than there is in all of the animals in the world. You're adding up elephants, and you're adding up insects and all of that. So that. Have a huge amount of biomass. The other thing so that's our fungi that we want to discover more about. The other are the termites. And so there's a lovely image taken by my former grad student, Becca Clement. Those are pictures of termites from our Australia project that I'll talk about in a little bit. And then we worked with an amazing artist. We had a wonderful science art collaboration, and she added even more color color to the termites to show some of the diversity of how they look and what they do. And so for termites, there's about 3000 species, so a lot fewer species. We think about the the pest species often. So only 3% of termites are pests and eat our homes, and because probably it's quite lucrative to know about termites and to help people fix their homes that most, a lot of the people who study termites study these pest species. So 97% of the species are out there somewhere in the wild, doing other things, and we often don't know what sort of homes they live in, or all sorts of things. So there's a lot we don't know about the diversity. And similarly, you might say, well, the termite doesn't weigh very much, but if we add up all of the biomass of termites, it's about equivalent to the biomass of humans, and it's about equivalent to the biomass of cows. Why should I say cows? Well, one of the things that we hear about a lot is that cows belch methane, right? And methane CO two is the most common greenhouse gas that contributes to has feedbacks with warming, but Methane is a 30 fold worse greenhouse gas over 100 years. So it's a stronger greenhouse gas. It's a less, a lot less concentrated. There's less of it, but things like humans and humans and termites, fart termite, or fart methane, and cows belch it. So we're talking about a greenhouse of gas that's being emitted. And so if you're thinking about, you're worried about your cows belching methane, then you should potentially be considering whether termites are farting methane.
Joshua Ginsberg 16:58
And I know you don't know the answer, but, but when we did a back of the envelope calculation a few months ago, termites were pretty far up there, close to cows, in terms of how much methane they might be releasing, at least order of magnitude.
Amy Zanne 17:11
Well, they're probably potentially producing it, and we'll get to in a little bit whether it's actually being emitted to the atmosphere.
Joshua Ginsberg 17:16
All right, now that we've seen the amazing biodiversity, and you said earlier that we've studied ants a lot more, and we'll have to figure out why ants are so much more attractive for ecological study than termites. But now that you've studied termites and fungi and decay, can you talk a bit about the difference between how they approach
Amy Zanne 17:41
it the Yes. So you have, you have these really different groups. They're in different kingdoms. You have a fungus, and you have, you have termites, that are an insect, right? So really wildly different organisms that are both adapted to feed on the same resource. And so for them to be able to do that, they figured out how to do that in some really different ways. And we should switch to the next slide. Yeah. Please, that pull up. Please. There we go. Yeah. So here's incredible visions of how our views of how they forage for them. And so you have these two groups, the fungi and the and the termites that are both out there in the world trying to find this resource and and so the one thing you can guarantee about fungi is that they're going to be there. You can't guarantee any given species of fungus finds a given piece of wood, but there's spores of fungus that are floating around in the air and raining down on all of us, including on the dead wood. You also have that you can see the hyphae. They make these hyphy little threads that are kind of like little roots from plants that explore the world. And so you can have the hyphy colonize the wood from below. And then you can also have them as spores, latent spores, or yeasts that sit or sit in the living wood. And once the tree dies, the stem dies, they start growing. So they can easily colonize the wood. So again, any given species would be hard to predict, but you can guarantee that there'll be fungus out there in the world. Termites, on the other hand, are insects, so they're ectotherms. Ectotherms means they don't produce their own heat, so they're really dependent on the temperatures being warm enough for them to be able to move around. How they work is that they have a caste system, and so they have a king and a queen, which is a little bit different to ants. Those king and queen mate for life. And then you have soldiers that go out and protect them. Ants are their biggest predators, but many other things eat them. And then you have workers. And those workers are who go, go and find the food. So what they have to do, they have a multi step process. You have a worker go out, find a piece of wood, searching, and they can use things like these, these mud tubes, so that they don't get eaten by other animals. And they, they they're protected from the elements. That worker finds a piece of wood, returns and recruits its colony mates, and then they go back and they eat the wood. And. And once they consume it, they often go back to the mound where they're processing it. So there's differences in how they discover the wood. They're also really interesting because there are differences in how they can digest it. So termites have stomachs like us. Their stomachs have moisture in it, so that's a nice place for the enzymes to work. It also their stomachs are full of bacteria and produce and all sorts of things that help with decay. As you can probably imagine, fungi don't have stomachs, right? So how do they do this business? And so what they do is they excrete enzymes. They have extracellular enzymes that goes get excreted out to the environment, those enzymes then have to be able to get delivered to the substrate, to the to the wood, and that happens with moisture. So there's it's a very moisture dependent process for those enzymes to move to the wood. They're different, again, in terms of what they can break down. So the only thing that has evolved an ability to break down lignin, that really hard compound I talked about earlier is white rot fungus. So there's different kinds of decay fungus. There's white rot that can break down lignin. Brown rot fungi are really neat. They throw free radicals at the lignin and Break it, break that jail cell open, and then they can go in and get things that they want. So the fungus can can degrade the different components, especially if there's white rot, they can break down all the components. Termites don't have that ability to break down lignin. Some of them, though, incredibly, have become farmers, and what they farm is a fungus that can break down the lignin. So they bring the lignin to the comb, and the comb does the work, and then they can get the resources they need. But you know, most and those are only in Africa and Asia, so in the new world and in Australia and here in the US there, they can't break down lignin. So there's differences in whether different components get broken down. Both of them respire. So just like all of us are breathing out and releasing CO two carbon dioxide to the atmosphere, which is that greenhouse gas we talked about. But termites are these, these methane farter, so they're producing methane in their mounds. So they're different. They're differences in terms of the rates and forms that carbons release from the wood.
Joshua Ginsberg 22:14
So it's looking at the carbon from the trees, then into the system and then out into gasses,
Amy Zanne 22:19
or into the soil store into the mounds can be locked up in the soil or mounds for a while.
Joshua Ginsberg 22:25
We'll talk about one of my favorite terms in your research was early on when you did something called a rot plot. So I'll repeat that rot plot, right? So you do plots that you study rot in, and those were in temperate environments when you were doing your graduate work. And I'm just actually in my faculty job, faculty, so it was early faculty work. Okay, you see a lot of fungi in the temperate or at least, you see mushrooms and thing in shelf fungus and but, but there's more fungi. You don't see a lot of termites in forests in North America. So what did you learn about what were the major lessons you took home from these rock plots and the relative contributions of the two decomposers, right?
Amy Zanne 23:09
So I began. So, as I said, I started. I started by studying for life these plant traits, so the anatomy, the vessels to transport resources, the chemistry. And so I got recruited into a working group that friends ran at first Australia and then New Zealand. So we had a bunch of meetings, and we wrote a big review paper where we thought about how plant traits would affect decomposition and the decomposers. Not too many people were studying plant traits and decomposition at that time, so we proposed some ideas, and we also proposed to start doing these rot plots. So this is my st my st Louis area rot plot, where what we did was we cut up a whole bunch of different tree species that were native to the area, and some lumber that we had that had different wood traits in them, and we put them out in the environment. We used ridge tops and valley bottoms, thinking the ridges would be drier and the valleys would be wetter. So we would get that moisture gradient to see some differences and how that affects the decomposition. And we studied this process over about seven years time and and so along the way, what we found is things rotted a lot faster than we thought. So after just one year of decay, we had almost, or more than a quarter of the wood, on average, was lost. And by three years, only three years, half of our wood had disappeared. And on average, there was huge ranges, though. So some things like horse chestnut, we had to stop the experiment early for that one, because it was decaying so rapidly, whereas other things eastern red cedar, if you've ever lined your wool chest, you know where you put your wool sweaters in eastern red cedar is really good at repelling things like decomposers and so I think on, we lost maybe about half of it across the entire seven years. So it was very slow to decay. So there was a lot of nuance about different species and the characteristics. Six, they had more lignin, more carbon, slower decay. So we started learning about the chemistry with this. We also saw that there's there's a lot of differences, a lot of specificity as to which fungus likes to be in different species of wood. So we looked at turnover of communities across species and time. And we started seeing glimpses of these insects. And so we had, at one point, I harvested in this one what you put the wood out, you let it rot, you bring it back in, you dry it down, and you weigh the mass. And so you see that change in mass. And so I pulled this one bag, and as I was pulling it out, a black widow spider crawled out. And then the next bag I grabbed. The bag started snapping at me, and it was a little poisonous snake that was in there. It's too tiny to grab me, but you know, we just found all of this diversity, and we did find some termites there. So these were our first termite glimpses. But termites are not diverse or abundant in the US. There's just a few species I have seen, elates, the kings and queens, flying in Rock Creek Park in DC and a few other places. But they weren't that common.
Joshua Ginsberg 26:00
But you're probably more sensitive to that than most of us. How many, probably, how many rot plots were out there? Was it just yours, or were there other people doing them as well?
Amy Zanne 26:10
So I'm the only one. My group's the only one that I think calls them rot plots. It just kind of rolls off the tongue. We also came up that artist Donna, we worked with. We ended up coming up. They started inventing a game across a pandemic called let's let's rot. And so we have a card game that they put together for this. So we use rot a lot. We had eight in Missouri.
Joshua Ginsberg 26:31
But I thought one of the things that was interesting, that I wanted to point out is that the group in New Zealand and Australia and getting together a whole bunch of scientists, I think people should understand that this is often and increasingly so how science works. It is not a solitary individual sitting in a lab somewhere, thinking and coming up with an idea and then going off and doing it all by themselves. And I think as you go through your work, it's it will show again and again. And I think there's a sort of a because of movies and and literature, there's this sort of crazy scientist off on their own attitude and, and that's, I am a crazy scientist. That's, I was gonna say, half true, right? All right, so you were in the temperate zone, and then next thing you know, you're working in the tropics. So what I mean, other than, you know, nice beaches and the weather's better, but why the tropics?
Amy Zanne 27:20
Clearly, I wanted to hug a termite mound Right?
Joshua Ginsberg 27:24
To cuddle Yeah? Because once you cuddle termite Yeah,
Amy Zanne 27:26
once you cuddle a termite mound, you can't stop Yes. So I think, you know, one of the things that we wrote in that review paper was that we really wanted to study the relative roles of these different decayers. And so to do that, I couldn't stay sitting in Missouri. I had to take the show on the road and go to the tropics. And so it was really important, if we wanted to contrast these different decayers and how they worked, to really study them where they are and where they're both common. And so that would be the tropics. The other thing is that the tropics is where the bulk of the trees are in the world. There's more trees. There's more living trees, ergo, there's probably more dead wood on the ground, but these numbers have been really poorly measured, and so we're trying to gather measures of how much dead wood is in the landscape and tropical landscapes as well. So it's really important from a to understand how the global carbon cycle works. You really need to look into the tropics. And so going to the tropics both for the amount of dead wood and to follow the pathway of the termites,
Joshua Ginsberg 28:22
but you said hot and dry, cold, dry, hot, wet microbes, for microbes, but now you're in the tropics, you've got more wood, it's hotter, it's wetter, and you've got microbes and termites. So is that part of why we just didn't know much, because it gets, it gets eaten up pretty quick.
Amy Zanne 28:45
So I think the what we didn't we know that termites like the tropics, but we don't know whether they prefer wet or dry. We had expectations maybe they do better the dryer, but they we didn't know much about termite decomposition yet, all right, yeah.
Joshua Ginsberg 29:03
So next up Australia, and you had both termites and microbes, and so talk a little bit about what why you went to Australia, and how you structured the research to study the differences between the two.
Amy Zanne 29:18
Yeah. So I spent my postdoc time in Sydney, and so I was already familiar with Australia, and I had connections and collaborations there already what I was looking for if I want to study this contrast of wet and dry and how that affects the decomposers, I wanted to look at the relative sensitivities of wood dwelling microbes and wood feeding termites. Do my expectations play out? Do is microbial decomposition, fungal decomposition faster in wet places, wet places in the tropics, if temperature is always warm and termites more important in the dry places. And so I needed a gradient from rainforest to Savannah, so we had that full wet to dry contrast. Left, and I knew that I could find that. So we were up in the Daintree in Far North Australia. So if anybody's been to the Great Barrier Reef, there's rainforest right near there. So we were at Dane, Dane tree rainforest, RFT two. So that's the Daintree Rainforest right here, which is also the RFT two. Yep. And, and then we knew that if we could drive 70 kilometers, and we could change the amount of rainfall tenfold, so we could get much drier systems by going just 70 kilometers away. And so that's the savanna here. And so I knew that I could get a really nice gradient without driving too much to get this entire contrast and think and see whether that the termites became relatively more important. So we established five sites. We had a drier Savannah there. That's a dingo in the background there that we happened to catch the first time we went out there. It's the only time we saw Dingo. And then a little bit of a wetter savanna, an in between site where there's a lot of eucalyptus. And then two rainforests, a bit of a drier one and then a wetter one.
Joshua Ginsberg 30:59
So over the course of 70 miles, you have the complete range of moisture. Temperature vary a lot.
Amy Zanne 31:09
So yeah, there were temperature differences. There's it was all in the same wet season dry season cycle. What you'll see is that this says mount in both of these. And so the mount Lewis is the higher elevation. So Australia is not a tall continent. These were 1000 meters high. So about as about as tall as you'd get in. Well, you get maybe 3000 is the tallest you get. But so we went over the divide, and as we went over. This is why, this is Mount Lewis wet. It's on the east side near the ocean, and this is the dry side away from that. And so it was a little bit cooler at these higher elevation sites.
Joshua Ginsberg 31:49
And was the assumption that you were close enough so that the biota could move, and so that you were controlling for sort of potential random effects of geography. Was it just practical?
Amy Zanne 32:05
No, it's more practical. Can we actually reach these in a field campaign? Because actually, there's complete turnover of the tree species. There's also a complete turnover of the termite species along this gradient, and there's, I think probably, I can't remember if there's complete turnover of the microbes, the fungi, but certainly there's strong differences across this gradient. So you see this, what we we didn't know if you can see that in this slide here we have, we have one rain forest, one Savannah, and the sclerophyll site right next to one another. So presumably they could move. We're within a kilometer of one another in those places. But we see complete turnover the species. So it's very much a habitat selection. You either do wet and you know, well in rainforest, you do well in Savannah.
Joshua Ginsberg 32:47
And so you have termites, you have the microbes. And so what was the sort of take home message you got from studying them in these different habitats so close to each other,
Amy Zanne 33:06
So there we go. So we have, we had, we started with the rot plots, which you see there. So we took my same rot plot design of these small blocks of wood we had. We used Radiata pine because it was not native to any of the places. So it was novel everywhere, and we put that at all five sites. We also harvested native tree stems at the two end points, a rain forest and Savannah. So we looked at tree wood trait diversity. And we also looked at a common substrate across the entire place.
Joshua Ginsberg 33:34
Define what a wood trait is. So people, because we had the wood traits before.
Amy Zanne 33:37
So that's the chemical composition, like the amount of lignin, a lot amount of carbon, amount of nitrogen, the density of the wood. We played around early days with vessel anatomy, but that didn't we thought these might be highways that the termites could move through, or the fungi could move through, but it didn't seem to be. So we measured a lot about the chemical composition and the density of these species, and so we put out these blocks of wood, and we found that that when it's warm and wet in the rain forest, you get faster microbial decomposition as we'd gone in expecting. What we also found was that termites were everywhere, but they did elevate the decomposition in the drier places, so that we got similar total decomposition when it was wet or when it was dry. We didn't find the contrast of dry season and termites more important, which is interesting, and I'd be happy to chat about that later. So we had some really nice findings. We're having some continuing really nice findings. So Baptiste, my post doc, who I think is watching as we speak, is having some really interesting work that he's finding where that if a termite discovers a piece of wood, that termite is somehow altering the fungal community. And so remember, these are competitors, right? And so what he's finding is that there's actually a decrease of the saprobes, those those those decayers, those fungal decayers, probably leaving the wood. Available to the termites from longer so we still have some emerging findings that are really fun coming out of there. The other thing that we learned was that the oh shit moment where you have lemons all of a sudden. So we wrote the proposal. I came up with this proposal that was funded by NSF and NERC, the UK funding agency, and we thought, This was great. Remember, I'm largely living in the temperate zone, and I'm thinking I've mostly been exposed to microbial decomposition process. When we actually got to the savannas we saw, we realized that a lot of these trees while living, are hollowed on the inside. So if anybody's ever heard a didgeridoo, a didgeridoo is an a musical instrument played by Indigenous men in Australia. This is a termite hollowed tree that they cut, cut and make into a musical instrument. And so these trees are hollowed on the inside, and we and why this matters is that a lot of times we're trying to think about carbons as forests as carbon stores. So what we do is we see the size of the tree and how dense that wood is, and then we calculate how much carbon should be in there, since about half of the wood is is carbon. But if there's missing trees, missing parts of the tree, if there's hollowing that you don't see from the outside, then you're you're saying that there's more carbon in that tree than is actually sitting there. And so I was fortunate enough at the time to be my post doc Habakkuk, and then my graduate student, Abby. This is she started as an undergrad and then continued with us for her PhD. And now she's doing this for a living in Australia, doing carbon accounting and trees. She did different things like cutting down trees. So this is this tree here, cut and you can see the hollowing it has on the inside. They were going to create a fire break, so take these trees down. Anyway. She used a resistograph drill to drill inside the tree. We can also use sound waves to look for hollowing in trees. So use these different non invasive methods to look for how much is missing. And so some of our savannas, we found that 30 to 40% of the biomass is probably missing while the trees are still alive. And so we get this answer pretty wrong about how much carbon is stored, if we didn't take into account some of these other places, like the rain forests, are missing three to 8% so less, but still, there's a fair bit of necrosis happening even even while the tree is still alive. The other missing thing that we forgot about when we were writing the grant is that termites like to go to the wood, eat the wood, but then return back to their homes. Right their mounds. Some of them stay in the wood, but most of them return back to the nest. So a lot of the decomposition is actually happening in the mounds. And we were measured, we were trying to follow the carbon out of the wood, so we would measure the amount of CO two and methane being emitted from each piece of wood that we would harvest. But if the termites have taken it away, it's actually not been emitted yet. So Abby, again, came to the rescue. And so another part of her dissertation was to make mounds kind of look like Franken mounds, where she put these collars on top and she could collect the CO two and measure how much they were emitting. And so from that work, she was able to show that that you get more methane when it's warmer. Termites are ectotherms. They are more active when it's warmer out. But she also saw some really incredible differences amongst the different species. And so a lot of what we know about termite methane emissions is thought they're listed as one of the biggest natural sources of methane, certainly salt marshes and Marsh systems and things like that. But termites are on that list. Usually, what people do is they take what we call naked termites. You just take a termite and you stick it into a chamber and measure how much methane it produces. So this copter termes, which is what's hollowing these trees, was our biggest methane emitter when they were naked, but when she went to the mound and put the collar on, they were the lowest methane emitters. And what's happening here is that these mounds are not just homes to termites. They're homes to lots of things, including lots of bacteria and things like that. In their walls, there's a type of bacteria called a methanotroph. Methanotrophs like to eat methane. So what they're doing is they're consuming the methane before it's emitted. So certainly the termites are farting a lot in there. But then you end up getting these methanotrophs up ticking in the mounds and really scrubbing out that methane. So
Joshua Ginsberg 39:14
they've got their their stack scrubbers Exactly. Well, that's That's impressive, and also fascinating, because we, I think this is a great example of how curiosity driven science can answer serious questions about the carbon balance globally. And, you know, I think that we need to understand that science is not always linear, right? And you go out with set of assumptions. And I think what was great about this was, you know, on the fly, you adapted, and you saw something, it didn't make sense, and you figured out, not once, but twice or three times, how to lots of lemonade, lots of lemonade, but, but the lemonade is useful. So, you know, termites became, obviously. A passion, and then we shut down for the pandemic. And I'm wondering if you could talk a little bit about your crowd sourcing project during the pandemic, and how you know what you discovered from that.
Amy Zanne 40:15
So actually, this started before the pandemic, but carried us through into the pandemic. So this was, this was a project that I we ended up learning a lot from that site in Australia about how termites and fungi decay would but that's only one place in the world, and I really wanted to understand global carbon cycles. And so if you only go to that one point in Australia, you don't know how that operates across other places. So I wanted to scale up and put that into context. How does a relative role of termites and fungi decay wood around the globe? The other element of this is that I was trying to get NSF funding to support my project looking at the relative climate, temperature and moisture, precipitation sensitivities of termites and fungi. I wrote an NSF grant, and the reviewer said, why would we possibly fund this? Who cares about termites? You know, they don't matter at all. And I had colleagues that were showing in Borneo that 50% of wood in their systems is going through termites. And there are quite a few trees in Borneo, and there's quite a few trees in Borneo. So we said, Okay, well, we'll do a pilot study. And so we did a pilot study in Australia, those two end points, and we ran it for a year and quantified how important termites were in this system. I happened to be on sabbatical that year, and I was based in Bordeaux, but also Amsterdam and Copenhagen, running around Europe and different giving different talks in different places. I was coming over for field work in Australia, but also going to Japan and to Indonesia. And so as I go around and talk about this project, I we were, I said, you know, we came up with a simple system where to do the rot plot in Australia. We would wrap the pieces of wood in mesh to keep out the termites, but then we'd cut holes in the bottom to allow, we just used a hole punch and to allow the termites to come into the system. So it was a very simple method that was not very expensive to do. And so people really liked this idea, and said, Oh, I want to study this. I want to study this. And so we started getting all of these other people joining in the effort. And it got so popular that we ended up, I ended up posting on Facebook and Twitter, and so this sort of crowdsourcing of citizen scientists who wanted to join our project. And so I ended up convincing 108 people at 133 sites around the world to join our efforts. And it was fun, because we I was able to, it was, it was low cost stakes to come in. So I had a Brazilian PhD student do this as one of his chapters for his PhD. I also had full professors from Spain and Colombia and the US who put in many sites, 16 sites that they could look at replication and really look at their system. So it was a low cost to enter, but you could get a lot of lottery tickets as you wanted to understand your system. So lots of people participated. The other thing was that it was equally representing the north and the south hemispheres, and it was equally representing the tropics and the temperate zones. So you can see lots of empty holes in this map of our sites, but we had a really good spread from the equator to the poles.
Joshua Ginsberg 43:16
Was that accidental or intentional? Did you recruit people to fill in those holes?
Amy Zanne 43:21
I recruited as I can. I tried really hard, say, with India, and I was on Twitter with a guy, or I was messaging with a guy that found me on Twitter who really wanted to join, but this was he was wanting to join during the pandemic. His dad was really struggling health wise, and so he never got out his sights. But, you know, it led to these interesting conversations. And I really targeted we started because we wanted to contrast also the those fungus farmers versus non fungus farmers. We had, we knew from my other termites, the termites the fungus farmers in Africa and Asia, and I was working in Australia, but we needed somebody from the New World. So I would target some places to start bringing people on board, yeah, and sometimes it works, sometimes it did. And what did you find out? Yeah, so and so that was the the the story of how we built the this group of people, and then we had some really incredible findings. And so with microbes, what we we as I already described to you, fungal decomposition is enzymatic. They excrete those enzymes. And so what we know from enzyme kinetics is that for every increase of 10 degrees, you get a doubling of the rate of decay. So there's a two fold Fahrenheit, I say, in Celsius. But it should, shouldn't matter. Yeah, it shouldn't matter. And so there's you get a doubling of the process. Well, it should matter, because it sells. It's in Celsius, is what I'm reporting. But you can do the conversions if you want and then. But for termites, we had no idea. So when we measured the termites, what we found was that they had more than a 6.8 fold increase with temperature. So if you increase 10 degrees. Then you get a 6.8 fold increase in how fast they decomposed. So this is incredibly fast, four times faster than what what we are seeing with with the fungal decomposition. So it's this unheard of rate response to temperature, incredibly sensitive to temperature. We still don't know why we're really curious. Is it about the enzymes that are doing the decomposition that are different, maybe in the termite guts. Is it differences in the microbes in their guts? Or is it simply that in warmer places, you have a longer growing season, so Termites can just make more babies that can eat more things? And so there's lots of potential solutions that we're really curious that we want to chase up. So, you know, it's very proud that this was a we had something that was very accessible to lots of people. We had no centralized funding for this. Everybody just pitched in with their own sites, with their own small grants. But we could come up with a really big answer that's that's incredibly important for thinking about future carbon models. So one of the things that we did was, then we said, well, the warm world is warming. Is expected to warm in these ways. Let's model that and think about what that means for where termites are going to discover wood more frequently in the future. And so we showed this expansion of termites into new the likely expansion of termites into new places around the world, especially in the southern hemisphere and and as I've already described to you, because there's differences in the rates and forms of carbon, termites probably decay less lignin, but they might release more methane or not, depending on whether those methanotros are there. So there are carbon consequences at global scales. As you, as you, as you alter as you warm the world and you change whether termites or microbes are decomposing, what I like to call the scary feedback loops. The scary feedback loops, positive feedback loops.
Joshua Ginsberg 46:45
All right, so we're running out of time, unfortunately, but I'm curious, what are you working on now, and how has all the things you've done gotten you here?
Amy Zanne 46:55
Yes, this has been a fun entry into carry this year. I've got lots of different projects that we have simmering away, but I'll highlight two of them. So one of them is in collaboration with Baptiste that you can see here the post doc and my group and we were thinking about how termites build mounds. The outside of the mound is built with a lot of mineral soil and also their spit, but the inside can be hollowed, and they need to fit in a lot of bodies. So remember that we like to use wood because it has lignin and it's a really good building property. Well, termites are pooping out lignin, right? Or we think they probably are, and what we were expecting is that they build these nest cavities, this nest material that we think should be really lignin or enriched. And so Baptiste convinced people from five continents to send samples. So we have, I think it's about 140 inside of termite mounds sitting in my my fridge here at Cary and he came,
Joshua Ginsberg 47:57
we don't let people keep food in those fridges. Just don't worry. Well, it's termite food, right? Yeah.
Amy Zanne 48:04
So he, he came over to Cary for a month. He lives in Australia and Brisbane area now, and he ground up the samples, and he extracted out the lignin and the carbon and the nitrogen. And so you can see this amazing diversity of colors here from these different insides of mounds. And so what he's showing is that some mounds have 65% of the inside of mounds is just lignin alone. So incredibly lignin enriched. And he's done some back of the envelope calculations to contrast how much Deadwood is in the ground in some of these ecosystems versus inside termite mounds. And what he's finding is that in some places, there's more carbon stored in the mounds than on the ground in Deadwood, which is, again, a really unmeasured, unexpected potential carbon store. So really interesting. But what we also don't know is how long these mounds exist. There are some amazing numbers. Some places in South Africa where mounds have known to be in the same place for 30,000 years. So some of them can be incredibly long. We don't know if that carbon, though inside is turning over. So is that carbon, that similar age, and so how long? So we want to set up, you know, people set up these forest monitoring networks where they'll measure the growth and the death of trees in different landscapes. And so what we're hoping to do is to do something similar with termite mounds that Baptiste will likely lead, looking at how long termite mounds exist, and how old is that carbon, how fast does it cycle in the mound? So that's one project we're really excited about, and then another has been a delight with Jane Lucas and Evan Gora here at Cary. And so this is supported by an Innovation Award, which is great seed money that we have here at Cary to really facilitate collaborations among scientists. So Jane and Evan, before I got here last year, wrote an innovation award and included Brad oberly, who's at the New York Botanic Gardens and and Jane and Evan have been working in Panama for quite some time. There's one of those monitoring plots, a 50 hectare monitoring plot. There a. In Panama, at barrel, Colorado Island, and the plot was set up in 1982 so you have live trees tagged back in 1982 and then re censused every five years. Well, if there's a tag put on when it's alive, when it falls over and dies, you can follow that tag. And so Evan has been following that dead wood. And I think there's around 18,000 pieces, or something insane, dead wood on the ground, following and so we just went down. Most of the people who study the decomposition process, who the microbes are, how the chemistry changes through time, do little experiments like I showed you. And so we don't know a lot about what happens with naturally recruited wood. So with this filtering that Evan was able to do, we're now following these huge logs that are lying in the grass, on the soil, and monitoring those changes in the fungal communities, the changes in the chemistry of the wood and lots of other processes. So this is a really fun project. We were just down at end of August, doing some sampling and setting up some protocols. So these are, these are two of my current threads,
Joshua Ginsberg 50:57
great, and they both show interesting things. I think the potential carbon storage in termite mounds is astonishing. If it's more lignin, more carbon in the lignin in the termite mound than out on the ground. And I'll amplify a little the Science Innovation Awards are we give runs about every 14 to 15 months. It's not quite annually, but they've been a real source of innovation and some marvelous failures, right? Because we like to fund experimental, early stage things that the National Science Foundation or major philanthropic foundations aren't going to fund because it's just too risky, as you said about the work that catalyzed that global citizen science project. They tend to like things that if you don't know the answer, you're pretty sure you're going to get one. And so we try and do that, all right, one of the questions people always ask and we try and end with, is, so I'm not a microbial ecologist. I don't know the structure of wood or the microbes that destroy it, or can't identify the difference between a termite and an ant. So what can I do? Right?
Amy Zanne 52:08
Well, I think one of the most important things to start out with is just be curious. I think that's been one of my delights as a scientist. I started as a botanist, and now I'm a termatologist, and so I've been curious along the way, and it's fun to explore, and that's one of my favorite things when I teach, is to be curious. But there are some other concrete things that you can do. One of them is that many of us have have wild places in our backyards, and so maybe some resist the urge to always remove the dead wood and tidy things up, or the leaves that are decaying, because these are home to lots of insects and other wildlife, and these are also storing carbon and nutrients. And as they're decaying, and they're releasing that carbon and nutrients back into the environment, these are nutrients that can stay in the ecosystem, so rather than moving them away and pulling them away. So thinking about your wild spaces and maybe changing your views and how much you need to remove all those rotting leaves across the entire lawn or those pieces of logs. Another is to support science. And so science right now is under under threat and and so thinking of ways to just support the science so that we can continue to try to understand the world and to better understand the world for the future. Probably a third one then is thinking about we. As long as you're 18, you can vote, so use your voice. Think about the wild places that we care about and continue to protect them as well.
Joshua Ginsberg 53:37
Thank you so Amy. Thank you so much. I am in awe and exhausted, but it was quite a run, and I hope you've enjoyed it as much as I have. We have time for a few questions.
Amy Zanne 53:58
If you look with our science paper, the first dog in the moon picked us up and wrote a fabulous cartoon about us. And so you'll see that there was a question posed by the first dog in the moon asking whether the role of being a dermatologist isn't that the best job in the world. And I would certainly agree it's been a joy for me.
Question 54:32
EO Wilson said there's a huge amount of biomass in ants. How does that compare to, say, termites or microbes or other things?
Amy Zanne 54:41
So yes, there's certainly a huge diversity in ants. There's also a lot of researchers in ants. It's been harder keeping people studying termites and understanding those diversities. So, you know, there's, there's ants are the biggest predators of termites, and so there's massive interactions between the two. So there, there's. The by some of my biggest collaborators, Kate Parr and Paul Eggleton in the UK. They they had what they called, they're the tarts, they're the termite ant research team, because they're often studying them together. So yes, they're, you know, study, study the little things, as Kate often says, the little things that make the world go around. And these are all really important to say.
Question 55:19
Do you think there are more people studying ants because there are more ants in the temperate zone and more biologists in the temperate zone? And if we had more scientists in the tropics, might we study termites more?
Amy Zanne 55:29
Possibly, yes, that also ants are often more obvious, because they have those thick exoskeletons that are, you know, they're black or dark colored, and they can be out in the environment more so they're more obvious. People, I don't know, people react to termites and find them often kind of icky and squishy. So there's maybe an ick factor. So a few things can you contribute to that?
Question 56:10
What's the rate of different, the difference in rate of release of CO two with buried wood versus exposed wood?
Amy Zanne 56:19
We were really curious about this process, you know, what is the rates and there and the release. And the other thing I didn't, I focused on on termites farting methane, but if methane is produced when an anoxic, when there's no oxygen in the system, and a lot of times, if Soils get flooded. You can get anoxic conditions where there's no oxygen, and again, methane can be produced. You think about lakes that erupt with methane, or peat bogs or things like that. And so we had, actually, it's a nice queue up. We had a study where we my my former post doc, Brad, who is now collaborating with us. One of his favorite sports is baseball. And so he was thinking about the fate of baseball bats, which are typically made of ash. And so we knew that around us in Missouri, the ash trees were all dying, and so he wanted to know the fate of the dead wood ash. And so we had an experiment where we buried some pieces of ash and we had it sitting in the soil, and we actually suspended it and we measured how much CO two and methane. So we found the the most methane when it was buried. So you'll start getting methane when you as released when you bury the wood, you'll also if it's wetter, Moisture Matters. So if wood is connected to the soil, either buried or sitting on the soil, you have a water front, and so you'll have faster microbial decomposition. Termites are another factor again, but if you're talking about around here, then it's going to be a microbial driven process. And so soil connection, moisture connection, will matter and lead to faster rates of CO two. It's all going to decompose at some point. Parts of it might be sitting in the soil for long periods of time, but it's going to stop looking like a log eventually,
Joshua Ginsberg 58:02
but you're getting different ratios of methane to carbon dioxide, so methane being a 30 fold of our greenhouse gas, which is a natural process, and we need greenhouse gasses.
Amy Zanne 58:08
Having greenhouse gasses is a very good thing. We wouldn't have life on planet without them, but it's kind of like Do you have a thin blanket versus a too heavy blanket, and if we add a lot more greenhouse gasses, and we're starting to get too hot of a blanket, and it gets too hot.
Joshua Ginsberg 58:26
Metaphor, one more question. Lori, do you have one from the from the virtual audience?
Question 58:32
We have a number from the virtual audience, but one that has come up a few times, surprisingly interestingly, is, how do we know when a tree is dead and another one that has come up a few times is, is it okay to pick the mushrooms on the decomposing trees? I do.
Amy Zanne 58:53
Yeah, so maybe I'll take the second one first so you can think of the mushrooms these the mushrooms are like the fruit on an apple tree that there's the fruiting bodies, we call them, which are often the mushrooms that we buy in the stores. These are just a bunch of hyphae all stuck together, and then they're producing the spores. And so if you pull out a mushroom, you're taking away the spores. But there's probably lots of other mushrooms around, and there's a lot of the hyphae, those hyphae, that are exploring in the log. So I definitely love to forage for mushrooms and pick them, and I do it. You can get upset with me. That doesn't mean that it's the right thing to do, but I certainly think there's a lot of mushrooms out there in the world. I think you should be fine. The other question was, when do you know a tree is dead? When do you know a tree is dead? That's a great question. I think Evan and I were just talking, we were just talking about this when we were in Panama that, you know, they marked down this tree is dead, and then all of a sudden it's come back to life. So, you know, there's, there's various, various living tissues in trees. You can tell if the the leaves are coming out. Out that there's live wood, if there's green wood, there's meristematic tissue that allows the tree to grow route bigger in size and also grow at the tips and put on new branches. You need to find green tissues there for to tell that it's alive. But you can also have the roots persisting for some time. You can think about chestnut trees. The chestnuts trees are essentially defunct. And if they get too big, they die back. But those roots keep sending up new suckers, and so they continue on. So you can have the low ground tissue is still alive. So what you want to look look for is that green tissue, the the meristematic tissue that you might find just under the bark in some places, but you might have to dig around to look for the roots.
Joshua Ginsberg 1:00:41
So the last question turns out to be a good one, even though it sounds ridiculous.
Amy Zanne 1:00:46
Yeah, right, yeah. So a good one for today. Yeah, the living dead.
Joshua Ginsberg 1:00:49
The Living Dead, right. Amy, thank you so much. And audience, thank you for coming. You.
Joshua Ginsberg 1:01:05
I forgot to mention those little tags on the back of the seat, which can be annoying, and I apologize for their annoying qualities. However, they indicate that they are seats that we reserve for our supporters in the Aldo Leopold society. And if you're interested in joining, please let us know. Just stop anybody with a tag on their their jacket.
