COMPLEXITY: Physics of Life

Mingzhen Lu on The Evolution of Root Systems & Biogeochemical Cycling

Episode Notes

As fictional Santa Fe Institute chaos mathematician Ian Malcolm famously put it, “Life finds a way” — and this is perhaps nowhere better demonstrated than by roots: seeking out every opportunity, improving in their ability to access and harness nutrients as they’ve evolved over the last 400 million years. Roots also exemplify another maxim for living systems: “What doesn’t kill you makes you stronger.” As the Earth’s climate has transformed, the plants and fungi have transformed along with it, reaching into harsh and unstable environments and proving themselves in a crucible of evolutionary innovation that has reshaped the biosphere. Dig deep enough and you’ll find that life, like roots, trends toward the ever-finer, more adaptable, more intertwined…we all live in and on Charles Darwin’s “tangled bank”, whether we recognize it in our farms, our markets, or our minds.

Welcome to COMPLEXITY, the official podcast of the Santa Fe Institute. I’m your host, Michael Garfield, and every other week we’ll bring you with us for far-ranging conversations with our worldwide network of rigorous researchers developing new frameworks to explain the deepest mysteries of the universe.

This week on Complexity, we talk to SFI Postdoctoral Fellow Mingzhen Lu (Google Scholar, Twitter) about the lessons of the invisible webwork beneath our feet, the hidden world upon which all of us walk and rely — largely unnoticed, and until recently scarcely understood. We discuss the intersection of geography, ecology, and economics; the relationship between the so-called “Wood-Wide Web” and urban systems; how plants domesticated mycorrhizal fungi much as humans domesticated animals and plants; the evolutionary trends revealed by a paleoecological study of roots and what they suggest for the future of technology and civilization… This episode is an especially intertwingled and far-reaching one, as suits the topic. Plant yourself and soak it up!

If you value our research and communication efforts, please subscribe to Complexity Podcast wherever you prefer to listen, rate and review us at Apple Podcasts, and/or consider making a donation at You'll find plenty of other ways to engage with us at

Thank you for listening!

Join our Facebook discussion group to meet like minds and talk about each episode.

Podcast theme music by Mitch Mignano.

Follow us on social media:
Twitter • YouTube • Facebook • Instagram • LinkedIn

Discussed in this episode:

Evolutionary history resolves global organization of root functional traits
by Zeqing Ma, Dali Guo, Xingliang Xu, Mingzhen Lu, Richard D. Bardgett, David M. Eissenstat, M. Luke McCormack & Lars O. Hedin
in Nature

Global plant-symbiont organization and emergence of biogeochemical cycles resolved by evolution-based trait modelling
by Mingzhen Lu, Lars O. Hedin
in PubMed

Biome boundary maintained by intense belowground resource competition in world’s thinnest-rooted plant community
by Mingzhen Lu, William J. Bond, Efrat Sheffer, Michael D. Cramer, Adam G. West, Nicky Allsopp, Edmund C.  February,  Samson Chimphango, Zeqing Ma, Jasper A. Slingsby, and Lars O. Hedin

Complexity ep. 8 - Olivia Judson on Major Energy Transitions in Evolutionary History

A (Very) Short History of Life on Earth
by Henry Gee (Senior Editor of Nature)

"General statistical model shows that macroevolutionary patterns and processes are consistent with Darwinian gradualism
by SFI Professor Mark Pagel
in Nature
Complexity ep. 29 - On Coronavirus, Crisis, and Creative Opportunity with David Krakauer

Childhood as a solution to explore–exploit tensions
by SFI Professor Alison Gopnik
in Philosophical Transactions of The Royal Society B

Complexity ep. 35 - Scaling Laws & Social Networks in The Time of COVID-19 with Geoffrey West

Complexity ep. 17 - Chris Kempes on The Physical Constraints on Life & Evolution

Complexity ep. 60 - Andrea Wulf on The Invention of Nature, Part 1: Humboldt's Naturegemälde

Do Androids Dream of Electric Sheep?
by Philip K. Dick

The Shock Doctrine
by Naomi Klein

Doughnut Economics
by Kate Raworth

The Long Descent
by John Michael Greer

6 Ways Mushrooms Can Save The World
by Paul Stamets

Complexity ep. 43 - Vicky Yang & Henrik Olsson on Political Polling & Polarization: How We Make Decisions & Identities

The Expanse (novel series)
by James S. A. Corey (Daniel Abraham & Ty Franck, here at IPFest 2019 on our World Building panel)

Episode Transcription

Prepared by and Aaron Leventman.

Mingzhen Lu (0s): So natural system, as we are discussing is recycling itself, eating itself as it matures. But it wasn't that way in the beginning. In the beginning, no organism was using oxygen, same full plants, plan, stern lignin, and those fossils terms that you dig up when they were first in limited 420 million years ago. No one can decompose with them until after 130 meeting years later, like around 295, many years, there was fungus that finally figured out an enzyme that can decompose lignin.

But by then, there was already a lot parting up. And then some of them become cool that we are using. I mean, it took them a long time to figure out. But before that it's basically linear. Natural system was the linear economy. So you take up calcium, you take carbon nitrogen, you build up your body. Then, you die. They become a waste. You lying on the ground and no one can do composts. You for meeting me to, yes, it was a linear economy like us. We're dumping our waste. More than one third of our global waste is opened down way more than once it opened up.

That's what forests ordering 300 million years ago. Look, over time ecosystem evolved to be circular and more and more circle with amazing efficiency. Especially for certain elements. They can be like 99%. Self-sustainable right. So being away in nature over time, figured out the ultimate question of sustainability. Starting those nature problem led me to ask, how about cities? How are we doing? I mean, I grew up on farm where everything is recycled.

I mean, nothing goes to waste. We have chicken with her pigs. We grow crops. So I can't stop asking like how I was doing in terms of cities. Are cities, linear or circular economy? The messages cities are very much linear. We have a long way to go to become a circular economy, which we should go to and which we will go to, but we should go there fast.

Michael Garfield (2m 23s): As fictional Santa Fe Institute chaos mathematician, Ian Malcolm famously put it, life finds a way. And this is perhaps nowhere better demonstrated than by roots, seeking out every opportunity, improving in their ability to access and harness nutrients as they've evolved over the last 400 million years. Roots also exemplify another maximum for living systems, what doesn't kill you makes you stronger. As the earth climate has transformed plants and funky have transformed along with it reaching into harsh and unstable environments and proving themselves in a crucible of evolutionary innovation that has reshaped the bias fear. Dig deep enough and you'll find that life like roots trends towards the ever finer, more adaptable, more intertwined. We all live in and on Charles Darwin's tangled bank, whether we recognize it in our farms or markets or our minds. Welcome to 


y, the official podcast of the Santa Fe Institute. I'm your host, Michael Garfield, and every other week, we'll bring you with us for far ranging conversations with our worldwide network of rigorous researchers developing new frameworks, to explain the deepest mysteries of the universe.

This week on 


, we talked to SFI postdoctoral, fellow Mingzhen Lu, about the lessons of the invisible web work beneath our feet, the hidden world upon which all of us walk and rely largely unnoticed and until recently, scarcely understood. We discussed the intersection of geography, ecology, and economics, the relationship between the so-called woodwide web and urban systems, how plants domesticated microrisal funky much as humans, domesticated animals and plants, the evolutionary trends revealed by a paleo ecological study of roots and what they suggest for the future of technology and civilization. This episode is an especially intertwangled and far reaching one as suits the topic. Plant yourself and soak it up. If you value our research and communication efforts, please subscribe to complexity podcast wherever you prefer to listen, rate and reviewus at applepodcasts and/or consider making a donation at

 you'll find plenty of other ways to engage with us at



Thank you for listening. 



It's a pleasure to have you on Complexity.

Mingzhen Lu (4m 57s): Thank you by having me.

Michael Garfield (4m 59s): I would like to talk with you first about your past, your biography, how you got into doing science, what inspires your intellectual curiosity and how you ended up at SFI? So just you want to riff on that for a little bit before we get into your work that would be great.

Mingzhen Lu (5m 15s): So it seems like a question with three steps. So originally it comes from my childhood experience. I’ll talk a little bit about my college, then how I ended up at SFI. So I grew up at a foothill of a mountain range in between Monte forest and fabulous. So that's where my family was at. So I grew up doing farming practice very early on. So I contacted his plants, soil, clouds, and also forest I going into the forest hands for mushrooms and sometime rabbits.

So from early on, I'm immersed in this natural environment. I get curious about all sorts of question, why this type of cloud will at you to rent tomorrow, like all those sorts of things. So I was always curious about nature and this why I decided to study ecology when I was in college, but I didn't only majoring in college when I went to college. So my college was Peking University, which in China is kind of an anomaly. It's a very liberal arts unit sense. So the encourage us to take all sorts of different topics.

So I actually took geography as my major and economics as a double major. And the reason is that I was always joined to make scope patterns like patterns. So that happened at the geographical scale, that to the top of the mountain, you'll see the others doing patterns. So that's why I was into geography. The idea of using a very simple theoretical framework to understand ecology is very fascinating to me. I mean, ecology is the economy of nature. That's why I decided after I was exposed to ecology.

That's why I decided to take economics as a double major, just to get to know more about the fundamentals of economics and modeling framework of economics. So I had all those different sorts of discipline of knowledge. Then I did a PhD at Princeton University focusing on ecosystem ecology, but I never forgot about my roots, where I come from, the intellectual roots or where I was interested in all sorts of different systems. The geography ecosystem at large scale and the biological system at a small scale and also human system.

So coming to SFI is it's kind of like a natural choice for me after an in-depth study of ecosystem, ecology off to, I was equipped to is the techniques that we co-system ecology. Now, I want to extend my research into other different additive systems. That's why I'm looking at urban systems, look at my side projects on psychology, the brain systems.

Michael Garfield (7m 49s): Casting long narrow roots out into all the adjacent. I feel like this conversation is going to be full of puns. So I apologize in advance to the listeners, but you basically just knocked off the entire bingo card of stuff I wanted to bring up with you today about how all of these different domains relate to one another and how your work provides a kind of lens through which insights into all of these different areas can be gained. So I think the place to start would be in this paper that you authored in nature. Evolutionary history resolves global organization of root functional traits, because just as we were talking about before we started, you're right, that with my background in paleontology, I love the time axis.

And this is something that we talked about with Olivia Judson way back I think was in episode eight, about how we take for granted that the systems that we see on the earth are just sort of always that way. Even after the advent of evolutionary theory, it's still been very difficult for people I think in general, to disabuse ourselves of this bias, this present bias that once upon a time the earth would have been for us now, a very inhospitable place.

And so I've been reading the senior editor of Nature, Henry Gee, wrote A Very Brief history of Life on Earth. And he's been talking about this thing, which is the evolution of root systems and of the success of stages of plant innovation and new forms of plants. And I'd like to start with you now that you've given us a personal biography, I'd love to actually like literalize that root metaphor and talk about the evolution of roots themselves and how that has changed over time and what you and your colleagues were working on in this paper.

Mingzhen Lu (9m 36s): So this two question, why is the history of roots? Another one is the history of collaboration. So the history of roots, I mean, it's easy to talk to you as a paleontologist, I mean, we can use the time of exes now. So imagine roots as a tool for plants to acquire water and nutrients, just like us eating right to sustain our metabolism, to grow the different facets of this roots. I mean, it looks like one thing, actually, they have different facets. One is root itself, the structure, the geometry, the size, the surface, I mean everything itself and the other parties, semblance is helper.

So roots actually form a mutualism, helping relationship. We as fungus fungi, as the mushroom, you see is their fruit body. So that's another, to root to themselves and their helper. So over evolutionary time both have changed. So I'll talk about root itself first, which is related to the paper itself. So root first emerged around 400 million years ago. I mean, that's based on the fossil record from Peking University, maybe even earlier, but roughly around that time, when a fish was dominating and after that for the last few handled, many years. In this paper, we present a decreasing trend of root diameter.

The most terminal absorbed here roots that are in charge of pumping up nutrients and pumping up water and the decreasing in size getting thinner and thinner. So this is one trend. Another trend is the helper. So they were from the first day. I mean, I shouldn't say from the first day, because I don't know, but very close to the first emergence of roots, they were already associated with mycorrhizal fungi. Mycorrhizal fungi here mean those fungi are almost domesticated by plants.  

Michael Garfield (11m 24s): They were there first, right? But they came to land first.

Mingzhen Lu (11m 26s): Fungi was first. It was way earlier than plants. They were already low 10-meter- tall organism, but this is a different type of fungi. Those are the descendants of those land fungi, but they are domesticated by plants, if I can use that word, they lost their independence. They're actually dependent on plants to feed them carbon. So the one you were mentioning, the even older fungi, they rely on algae to them, carbon sugar, right? Those fungi that are associated with roots, the mandatory, they are obligating dependent on plants to feed them carbon from the footer censuses.

So those fungi also go through evolutionary trend. The first of all is a very simple simplistic. You can think of the earliest association is the thin roots, basically because they're thinner they can get into cracks and get to the nutrients starting those soil pores. But around the time dinosaur first emerged, that's about 250 million years ago. So around that time, another type of fungi and mycorrhizal got evolved. Those are the descendants of this fungi that can decompose food that can give you mushroom, delicious mushroom the are domesticated by plants to use them to decompose soil organic matter and acquire nutrients directly.

Instead of waiting for bacteria for the insects to decompose the nutrients. Now plants have the initiative to just get it from the symbiotic helper. So this is about 200 million years ago. Then around the time dinosaurs went extinct earth went through a very dramatic climatic change period. Right around that time, the most powerful symbiosis happen. So plants figured out how to cooperate with certain type of bacteria that can break nitrogen into natural gas from the atmosphere, the most abundant gas by which means that they have an unlimited supply of nitrogen, which is the most demanded nutrients, most abundant elements, other than carbon, hydrogen, and oxygen.

So that's what the evolution of the helper site. So both are evolving. The roots are getting thinner and the helper are getting more powerful in terms of helping them. So this is a brief evolution of roots. In terms of how I get into this research, how this research has studied. So, as I told you, I was seeing Peking University as a student, I was studying geography, studying biology, studying ecology. So my thesis, otherwise it happens to be one of the few, the pioneer biologists who recognize the branching structure of routing system. Before him and another researcher, Professor Kurt Praxell, before they, to the branching structure roots up are not a much ignored.

So they were considered as just one thing and the use of sieve when they dig them up, the user's safe to just give them the arbitrary cutoff of two millimeter and the things then other than that, I'll call it a roots, find roots, but starting from, there was a recognition of the branching structure, the architecture that actually inherent difference based on the order of the roots, but all that I mean, if you think of a river system, you have small stream as first order when two small stream meet up, they form second order. When two second order river meet up into a bigger one, they form third order.

So on and so forth until they reached the ocean. So actually what we should really focus on of the first order, the terminal units using the language of the Geoffrey West Scalebook. I mean, it is a universal phenomenon. Implants is first order of roots, but you and your computer, your iPhone is a transistor, the smallest unit or, you know, building, it could be the faucet that fun us water and the waste throughout the building. So we decided to look at this terminal units across different continents, across different country.

And we found this astonishing with us that wasn't possible before, because they were not looking into the thing.

Michael Garfield (15m 27s): So in this paper, you talk about how it was assumed up to this point that the structure, the morphology of root systems was constrained by and adaptive to the same kind of economics that are governing leaves. So could you talk a little bit about that and how your results challenged that assumption and why there are kind of two different forces at play, two different pressures at work between what's shaping leaves and what's shaping roots.

Mingzhen Lu (15m 55s): And that's a fascinating question. So what is driving the evolution with leaf? I mean, obviously they have two dramatically different driving force. Why is driven by light competition? I mean, if your purpose, why you are designed is to observe light to the best of your ability and you need to compete. So it's a light game and it's air again. But when you are in the soil, it's a 3d space. So light shed onto plant it's actually 2d. I mean, it is 3d, but a leaf except light is actually 2d. It's a surface and leaf surface, but use a 3d you're using the soil matrix.

Now, after that image, the soil, I mentioned, we call it the soil matrix, actually it's 3d and water and nutrients come to you from all direction instead of from above by plight, only come from one direction, but nutrients and water from all directions. And for that, the driving force is for you to be as permeable, as possible, as efficient as possible to let in material. And that has caused the evolution of thinner and thinner roots. Because if you get thinner, you using one gram, I mean, that's the example we used in the most recent paper, using one gram of carbon, which you get from photosynthesis.

You can produce a thousand meters of roots and explore soil and they can give you water and nutrients. So that's the take level, why they are different in terms of the different pattern we found. So leaf, because it's driven by light completion. People have been long talking about this slow, fast spectrum. They call it leaf economic spectrum. I mean, they use the word economy again, because it's an investment. So either a thick leaf that can live long or thin that live shorter lifespan, and those thinner leaves tends to have higher nutrient concentration.

And those thick leaf tends to be where poor or less palpable from animals perspective in a way. 

Michael Garfield (17m 47s): So succulents.

Mingzhen Lu (17m 48s): Not less palpable. So I just mentioned the age and the longevity of the leaf as an axis, another axisis nitrogen as excess. So what we found in the roots is we only found one axis of change, which is diameter just to get everything else to this change of size. So within the fine two axes of change.

Michael Garfield (18m 11s): So again, to bring the time dimension back into this, and one of the findings that is really curious about this paper, but it makes sense once you kind of put it into that kind of natural history context is that you're seeing something different in the tropics than you are at the higher latitudes. And again, I was just reading a Gee’s book about how the re-emergence of polar ice caps and this sort of stratification of climatic zones across latitudes that was less obvious during the age of reptiles, you know, where like everything was basically kind of tropical until I guess the end of the ecoscene and then you get Antarctica and the Northern polarized cap.


It seems like as there is an increasing diversity of climate zones on earth, you're also seeing this change. I don't know if they're causally related, but one of the things that you talk about in this paper is how you see more kinds of roots in the tropics, because the tropics have basically preserved more ancestral plant forms than are apparent at the higher latitudes. And I'd love to hear you talk about that and how the strategies of these plants differ up in like the Northern boreal forests, for instance, versus like the Amazon.

Mingzhen Lu (19m 23s): I think about tropics as a source that has been pre-lived since the dinosaurs went extinct. I mean the more than tropical forest emerged right after dinosaur, when the extinct, and since then the tropics has been warm and landmass hasn't moved much right before that landmass was moving around from Pangea to the current one. But for the last 6 million years asked me pretty stable. So tropics has it been tropics, but the ball real has been killed periodically by the glacier. I mean the most recent one is from the last glacial maximum, which wiped out all plants up until north New Jersey.

That's why I did my PhD study. You can still find those borders that are carried by the glacier. So think about when the glacier retreat, you need to repopulate the area with spaces. Because of that, you have a filtering process. Subset of the tropics spaces will move out, but most of them wont adapt, be able to tolerate those colder climate, those more nutrient, poor soil, all sorts of things. I mean, also are the extreme biome that are younger, the desert, the Mediterranean, I mean, from a plant's perspective, the harsher compared to, with the tropics, which has ample water and pour light and pour warm temperature. So in that way is a filtering of the fittest. And because of that, you necessarily have less spaces and less functions. And because only a few functional traits can flourish in harsher any moment. And this is what we're finding that those harsher new environments tend to have, much thinner roots and the tends to have smaller variation of roots, which means thin roots is while the field strategy to throw there.


And once the extreme is seeing our most recent paper, the thinnest of all, which is quite absurd, absurdly thing, three times thinner than my hair.

Michael Garfield (21m 20s): So I want to dig it into this just a little bit more because as you say, in this paper, thin roots benefit plants in less predictable environments where rapid root growth response to a fluctuating resource supply is rewarded. So this is where I get to savor making these analogical leaps to other areas. Basically like there's a broader pattern that people like Mark Pagel have noted in his recent essay on evolvability, which is like the ability of a lineage of organisms to evolve rapidly. And he finds an upward trend in that evolvability over tens of millions of years in the mammal lineages that they studied, where even though evolution is still obeying the sort of Darwinian incremental process, animals are making larger jumps and body size towards the end of their dataset.

And this is related to this conversation I had with David Krakauer on the show back in 2020, episode 29, which I love bringing up all the time, because it's talking about what kind of organisms make it through these extremely disruptive phases of earth history, like the end Cretaceous extinction that you brought up a moment ago, where it seems like all of the survivors of that extinction are generalists that are highly adaptable and they tend to be small bodied organisms that are less sort of dependent on these mature, highly specialized ecosystems.

And then to stack one more thing on this house of cards. There's the way that it seems over the years over your lifetime and mine education has shifted from indoctrinating people in the great classics to teaching people how to navigate a rapidly changing knowledge system, to teaching people how to remain lifetime learners, how to keep searching. And this is akin to the research that SFI Childhood Development Researcher, Alison Gopnik has done on the explore exploit tension and how they're saying, like kids tend to be geared towards more and more exploration.

As you get older, you start paying more and more attention to exploiting what you already know. And you know, just one more thing, which is, you know, you brought up Geoffrey West a moment ago and his work on allometric scaling and organisms. He talks about this exact same thing about there being a trade-off and you know, his work with Chris Kempes also, they talk about the trade-off between growth and then maintenance as an organism gets older. So it seems like over time, at least in living memory, as the increasing complexity of human society has led to a more and more unstable environment it's favoring people that are sort of like shallower more nimble, faster growing root systems, intellectually things that, you know, it's, it's favoring, generalists, it's favoring people that to bring up the conversation we had with Andrea Wulf. And she was talking about how like Alexander Von Humboldt lived in a time when people had very, very deep sort of narrow specialties. You could think of like a tuber drawing down. And now you've got these people that look much more like the root systems that you were just recently studying in South Africa where you cast out a lot of nets are social networks.


5,000 Facebook friends, like they're much shallower and more tenuous, more precarious in some respect, but it's part of this bias towards a greater evolvability. And so I'm just curious how much water you're willing to let that hold as an analogy. It's like, how do you feel like that's supported by your work or not?

Mingzhen Lu (24m 46s): There's a lot of analogy. I'm impressed. So you mentioned quite a few things. I can't remember all of them, but you did mention exploration was exploitation, but I want to hold on that and expand it a little bit. So think about those find routes as very cheap, but very large net and they're more explorative. And if one direction doesn't work out, you can choose the other direction, but they'll thicker roots tend to do better at, in stable environment where they know what's facing next year.

So it's more like exploiting the location, they’re growing. So then that exploration, exploitation phenomenon is also very general in other area of ecology. For example, the contrast between mice and elephants. So we call mice our strategist. They are small. They reproduce where fast and where you knock them out they're very resilient. It's real quick to come back. But elephants take like 40 years to mature and then live for 60, 70 years. 

But once you knock them out very slowly, so they are called case strategists. So this is a very common phenomena, ecology. And I think the roots of economics. They call them nature that the spectrum of strategy to adapt, to live, to thrive. And there's two spectrum at both end, one is more adapt to you and why is less adaptive, but takes advantage of what is already here. And I think, as you said, as we are moving into an era where rapid global change at all fronts, I think those are strategist both intellectually or literally, we're benefit.

I think a lot of the mice in New York City are doing pretty good and they will be the last, I mean, we might be the last standing animal if the city got some much.

Michael Garfield (26m 38s): So, to that point, you make this comment in the paper that the trend towards the new roots has had major consequences for the symbiosis between plant roots and mycorrhizal fungi that we found that microrisal pollenization. That is the percentage of root length, colonized, declines, as the roots get thinner. And that herbaceous roots have approximately 30% less colonization than plants at the same root diameter, you know, call me crazy. But that reminds me of Philip K. Dick's novel Do Androids Dream of Electric Sheep? in which he's projecting the sort of post-apocalyptic society in which we basically extinguished all other non-human megafauna on the planet, which, you think about the history of human civilization has been one of us eradicating all of our other hominid competition and hunting various large, like the moa to extinction, these big animals.

And now we have livestock, and we have domesticated animals, but the biodiversity of those organisms is much, much lower than it used to be. And we're continually as we construct a more and more complete human niche with our technologies, the animals that we have domesticated in the way that plants domesticated fungi are fewer and fewer. And it seems like the same kind of trend is happening in that symbiosis. I'm curious to speak on that.

Mingzhen Lu (27m 57s): I didn't see that. Oh, well, so we did present a trend, you know, common language is if I can do it myself, why should I pay money for you to do it? So that's the calculation for plants, especially moving into new harsh environment is getting increasingly more expensive to pay others to do their work. It becomes increasingly beneficial for them to figure out on their own. It's like Apple now is no longer buying Intel chips. I mean, Apple, Silicon, why do I pay the premium for last powerful product, which Intel is providing instead of using our own M1chips, which is far more far more efficient, far more powerful and cheaper.

Apple is gaining so much more money by doing it themselves, right. And that's a trend, but I, I didn't see a where you're going in human history of domesticating animals and plants we actually selecting fewer and fewer and focusing more on efficiency. That's true. Yes. But I don't know if plants are doing that intentionally.

Michael Garfield (29m 3s): Probably not intentionally. So what does this mean in terms of soil composition in nutrient processing? One of the things that happened after the extinction of dinosaurs was that grasslands took over a huge percentage of the terrestrial earth surface. And over the span of human history, there has been a tremendous amount of deforestation and more and more of the earth. This is starting to edge into the other work that you mentioned a moment ago and your more recent papers. But, you know, one of the things that define grasses is that they have this unlike, I guess, most other plants, which have like a quote-unquote C3 metabolism.

Michael Garfield (29m 37s): Yeah, they have a C4, which is better athigh temperature. It's sort of more effective at harvesting scarce carbon dioxide. So like there's been a change in the atmospheric composition that has accompanied all of this stuff as well. And so, I'm just curious what your work has to say about the way that soils themselves have changed over the last 65 million years or so, the way that the atmosphere itself has changed and the way that that's created a different kind of environment for animals and the other organisms. And I guess that gets us into what you found in these other papers, the one that you published in NatureEcology and Evolution on global plant symbiont organization and the emergence of biogeochemical cycles resolved by evolution based trait modeling.

Michael Garfield: And then lastly, this piece biome boundary maintained by intense below ground resource competition in the world's thinnest rooted plant community. And maybe we're biting off too much all at once there, but maybe the right place to poke in here would be to talk about that NatureEcology and Evolution piece, and how you found these four different root strategies that you alluded to earlier and how they're related to one another and how they're setting up these competitions that lead to phase cycles like flickering in different biomes and how that changes the composition, that sort of tapestry of biomes across the surface of the earth.

Mingzhen Lu (31m 4s): I want to focus on one word you mentioned, flickering. That seems to be, I mean, that is central to what we are finding. So I want to focus on the word feedback. So we have been talking about this tiny little roots and the evolution of history, but one thing we should realize is yes, this is a tiny little thing that have been pumping water nutrients through a history. But this tiny little thing actually can generate macro scope patternyou can actually see with your eyes instead of the hair thing, then you can't over there. You can take an airplane and you can see those large-scale patterns. And the way it is functioning is through feedback. And the natureecology paper is focusing on those root helper, those microrisal, giant bacteria that are helping roots. So how the power of the feedback of ecosystems and vegetation and this alternative state that flicker of when you are at a certain zone and then the collapsing to one state or the other campaign song, which we, you move.

But the paper is focusing on the geometry of root itself and how the geometry itself generate this type of alternative stable states on the one. And you have this low statue of vegetation on the other side, one meter away, you have a totally different ecosystem that has much more biomass, but much less diversity. So both papers share this common thread of feedback and local skill, tiny thing, generating, this macro scope pattern of bi-stable states.

Michael Garfield (32m 48s): That's interesting. I mean, it reminds me of, they talk about sort of nutrient availability in coral reefs versus in other parts of the ocean and how the reefs sort of are harvesting and trapping much more of the nutrients. And so the water is in those areas are actually kind of nutrient poor. This gets into some of the findings in this paper where you're talking about succession and how at different phases of ecological succession, the system is limited by different nutrients. And I'd love to hear you talk about that because I feel like that really gets into, as you mentioned in the nature ecology evolution piece, why it is that experimentally, they found that, if you're a farmer, you know, this, that like certain, certain systems are limited by nitrogen and others are limited by phosphorus.

And so what are we seeing here? 

Mingzhen Lu (33m 31s): I was a farmer before I went to college. I still farm when I go back. So here's the thing. We talk about glacier, glaciation, glacier, distressed, everything. But when the go away, they leave abandoned nutrients in the soil, all those primary rock material that has been frozen in the ice, where the melt they'll verify tile and those foot higher soil are reaching phosphorous, but pulling nitrogen, that's just simple geology. And that provides the primary feeding ground for plants.

And there you have succession. You have the first tree growing, feeding on those who reach phosphorous. But as you grow, you move those phosphorus in your body and you have less and less in the soil. You start to get more and more phosphorous limited. But nitrogen is totally different in the beginning. This almost no naturally in the soil, but as you grow and grow nitrogen introduced from the atom sphere by those bacteria, by those natural fixing plants. And those are accumulated in those deaths, in those black soil, organic matter and the accumulate over time.

So over time you have two contrasting trends, your phosphorus is fixed in your body more and more, but in the system you're accumulating more and more naturally that are originally from atmosphere that wasn't there. And because of this contrasting trend, younger forest often limited by nitrogen because we were not there, not in the soil and older forest often limited by phosphorus because of the rock alleged aware that, I mean the older the soil, like the tropics are most phosphorous and limited.

So that's why you see this trend. And that's also why you tend to see a naturally and fixing plants in the earliest stage because there's none much natural there. And it is those natural fixing plants like the Red Elder in Oregon who are famous, the fixed towns, tons of nitrogen, and those natural don't get lost easily. We just stay in the liter cycle in the leaf. When the leaf die, they get into the soil. Then we get recycled, recycled, recycled, they keep popping up.

Michael Garfield (35m 39s): So, this raises questions for me. And I'm curious how far you're willing to explore in this direction about lessons from this for human economic systems. When, you know, talking with Geoffrey West on the show, and he talks about just how absurd it is that economists assume that capitalism can grow on check forever. But then it's like, well, at the same time, you know, you have systems like the Amazon that are constantly growing, but they're growing into their own decay. Like you're talking about, like a mature forest has found ways to recycle a lot of its own nutrients.

And so, you know, it's funny because if you look at stuff like Naomi Klein's Shock Doctrine, capitalism, where she's talking about, well, we have no more frontier anymore. So capitalism is just eating itself and that's terrifying on one level. But then if you recast it in terms more like Kate Raworth’s Doughnut Economics, then what you're actually talking about is the possibility that we're sort of transitioning into a mature form of the economy that is much better at recycling its own waste products.

So like, I mean, it, clearly we shouldn't, like that's not what we're really talking about when we're talking about like upsetting democracies or capitalism loving a disaster. So it can go in and rebuild exactly. But there is some kind of similarity in the way that ecosystems reinvade their own disruptive zones. And I mean, I know that, you know, you and I have talked about the way that the glycolytic metabolism that animals use that depends on oxygen evolved in kind of a response to this crisis created by cyanobacteria and climate cycles and the great oxidation event that killed a ton of stuff by flooding the atmosphere with oxygen.

And so modern industrial pollution has this kind of clear analogy to this prehistoric form of atmospheric pollution. And there's a lesson in there I'd love to hear you kind of play with a little bit.

Mingzhen Lu (37m 37s): You just led the conversation to my current research that I'm working on with colleagues here at SFI and colleagues at Stanford. I don't want to go too deep there, but I want to tell the analogy to why I'm working on urban system now. So natural system, as we are discussing is recycling itself, eating itself as it mature, but it wasn't that way in the beginning. We just talk about oxygen in the beginning. No organism, was using oxygen, same for plants, plants, stern, lignin, and those fossil stems that you dig up when they were first invented 420 million years ago, no one can decompose with them until after 130 million years later.

Yes. Later, like around 295 million years, there was fungus that finally figured out an enzyme that can decompose lignin.

Michael Garfield (38m 32s): Like all the plastic we're worried about. 

Mingzhen Lu (38m 34s): But then there was already a lot parting up. I mean, some of them become cool that we are using. I mean, it took them a long time to figure it out. But before that it's basically linear natural system was a linear economy.? So you take up calcium, you take carbon nitrogen, you build up your body. You become a waste. You lie on the ground. No one can do compost you for meeting me to, yes, it was a linear economy like us. We're dumping our waste more than one third of our global waste is opened down way more than once it opened up.

That's what forest ordering 300 million years ago. But over time ecosystem evolved to be circular and more and more circle, actually amazing efficiency, especially for certain elements, they can be like 99% self-sustainable right. So eating away in nature over time, figured out the ultimate question of sustainability. I mean, starting those nature problem led me to ask, how about cities? How are we doing? I mean, I grew up on farm where everything is recycled.

I mean, nothing goes to waste. We have chicken, we have pigs, we grow crops. So I can't stop asking like how I, we doing in terms of cities. Are cities, linear or circular economy. So I don't want to get into too much detail, but the messages cities have very much linear. We have a long way to go to become a circular economy, which we should go to and which we will go to, but we should go there fast.

Michael Garfield (40m 3s): So that kind of begs the question that I asked Geoffrey West. He wasn't very optimistic about this when he talks about how the scaling involved in cities and in the interaction networks in cities, we need to see what he called the finite time singularity, where the innovation crisis cycle is constantly ratcheting up to a faster and faster tempo. And eventually there's an inevitable collapse. It's a calculus. It's the question of, can we learn to recycle faster than we're learning to generate new waste products? You don't think so.

Mingzhen Lu (40m 34s): I use the analogy. The burst of oxygen was about 3.5 billion years ago. Then the multicellularity organisms that really thrive on using oxygen was much, much later, but that's beating your timescale leg. Then we had the lignin accumulating for the mini years until the mushroom finally figured out how to decompose them. Then we come to a more modern day. We have plastic, right? For like 50 to a hundred-year timescale. We're still trying to figure out, so you'll see this trend.

You always create waste first. Then it's only at one threshold when you realize, Hey, there's too much waste. It's either too much hazard or too much energy stored, but I have to figure out how to use it. So there will always be a lag. You can't reverse it. You can't figure out what's the way to utilize your waste before you have the waste.

Michael Garfield (41m 24s): So I guess maybe the more kind of precise way of asking that question would be, how can we think more rigorously about how much collapse is necessary in order for that recycling innovation to happen? You know, if we're talking about people like John Michael Greer who say, look, it's not a binary, it's not like we're going to have a techno utopia or it's a total collapse of civilization. He calls it like a slump. And I guess the question would be then what lessons can we draw from the fossil record? Or how can we think about this mathematically in such a way that we know not only where the limit to growth is, but sort of where the floor is if we're talking about like a market crash where it's like, at what point do we hit the price channel where Bitcoin stops sinking at around 30,000 bucks, and then it's like wobbling in that channel until it finds a way to start growing again. I mean, I don't know what your thoughts are on that, but I'd be really curious to know kind of where you given the fact that you're thinking about all this stuff all the time, see, how far are we going to fall before we catch ourselves? And we learn to metabolize all the waste products that we've been calling.

Mingzhen Lu (42m 26s): Oh, that's your question. Yeah. I'm I misunderstood your last question and I mis-characterized my response. I said no. So let me clarify my response. So the way we figured out the rate of us, figuring out how to recycle our waste, we always lag behind the rate we create waste. I mean, that's just by default, right? You first create problems or you solve problems, but as the timescale is matched. So going back to the question of lignin, it take a hundred meetings a year to figure out the lignin to compensation using genetic evolution.

The random mutation of a single location on the genome finally made a product that can decompose lignin using enzyme, which is a protein, but plastic. I don't think it will take a handle many years. It will take the timescale or many decades. We already have technique that combined two enzymes from nature to produce a soup in line that can decompose plastic super-fast as from a U.K. research group. So we already seen that. So the optimistic message is that yes, we are producing ways to foster and foster, but we are also solving the problem faster and faster, even though there's a lag.

Michael Garfield (43m 40s): And then you got people like Paul Stamets who's out there advocating for the fungi that are eating radiation. He was like trying to go out there and do micro remediation on Fukushima and this kind of thing. So it's like, it seems like the funds a year coming to our rescue.

Mingzhen Lu (43m 53s): So tying back to what you've just mentioned, Geoffrey West, we have to innovate faster and faster, I think. Yes, of course we have to because we're creating problem faster and faster, but I want to see that we can in with faster and faster. I think about the rate of genetic innovation. You're relying on natural process. We use precursor of fungi to feed on deadwood and we finally figured out a product. You compare that with our human innovation on paper, on computer, on digital platform, we’re way faster.

Michael Garfield (44m 31s): So I want to make sure that we give time to just going a little bit more into this latest paper that you put out on the fin bow in the effort temperate forest, because this requires us doubling back. I don't know what 20 minutes in this conversation to the last one and talking about how these different ecological regimes compete with one another. And I mean, this is such an interesting work because it's such a bizarre scenario. And again, you and your colleagues have challenged a pretty long standing assumption here in ecology, that it is the sort of external factors of a system that determine what's actually growing there.

And you're saying something more akin to what you just said, which is no, actually it's the way that organisms construct their niches and then lock each other out and maintain stable regimes that prevent invasion from competitors, even in a system where the climate between the fynbos and the forest is very similar, except in the way that these different plant cohorts have sort of defined it for themselves. I would just love to hear you expound on this particular piece of research a little bit before we wrap this up.

Mingzhen Lu (45m 40s): So that links back to our conversation on feedback and the non-linearity. So you think about our soil gradient from rich to poor as a continuous change. The traditional thing can, may give you a linear projection. Like if you on nutrients, it's zero, you get a vegetation that corresponds to a zero, 0.5 corresponds to 0.5, one corresponds to one. But once you consider into plants engineering their own environment using feedback, you shed your leaf to make your soil richer, or you're burning yourself to make your soil poorer.

All of a sudden, you are looking at a soil gradient that is still zero to one continuous change, but the vegetation on top is zero to one. You don't find open five. It’s either 0  or 0 1.  Why counts to why we in the middle, you can survive in the middle. It's almost like the weakest work on the political realm. You can't survive as a modernist. You have to appeal the extreme.

Michael Garfield (46m 37s): We talked about that with Vicky Yang, where she was talking about why, you know, both sides of the spectrum, same.

Mingzhen Lu (46m 44s): Same. You have to thrive at one condition. So as a fynbos plant, you have to devise a psudo-strategy, a combination of them let you thrive in this very moment, which is the one I said. And as forest, you have a set of strategy, allow you to thrive at a zero condition. So the soil condition to the meta point is 0.5, but you can't be that plan that is right there in the middle. You'll be odd competed by either fynbos or plant. You can't out compete any.

That is like a reinforcing process that pulls them away further and further over time.  The fynbos were burned on periodically, make them poorer and poorer and settle there at her poor nutrient state. And the forest will accumulate nutrients. I mean, we talked about the culmination of natural and in the system you'll get richer and richer over time. I mean, that's why at now we're looking at this sharp transition, like less than one meter of transition, like a binary foundation when you were flying over the landscape.

But historically the won't be less sharp. This takes time to emerge over evolutionary time.

Michael Garfield (47m 54s): So, I mean, again, maybe the last question for you would then be, so this is a sort of stable order in which you have these two sort of self-reinforcing domains, but then of course you get these extinction events and so on where again, it seems like, again for episode 29, like these generalists don't do so well in a mature ecosystem that favors highly tuned specialization, but then you have a chick salute crater, all of a sudden, and 70% of life on earth is wiped out. And then suddenly these evolvable nimble strategies pick back up.

And so I'm curious under what circumstances you do see something like the 0.5, like where are we seeing more generalists strategies in soil ecology?

Mingzhen Lu (48m 41s): Well, I want to see the 0.5 years generalist. They're not fit for the environment. So the, and those plans are one characterized specialist or generalist as a group because of the locked up together because the externalities, the shape of the harm to together in their skin of shaping up their soil environment. I don't see that much in increase the generalist versus specialist conversation.

Michael Garfield (49m 9s): I could be totally off base here, but it's sort of like asking under what conditions do political moderates start because I guess what I'm really asking you is question about, there's so much other work at SFI going on about political polarization and why we've seen increasing polarization over the last several decades. And the question would be sort of like, is there a lesson from your work on ecology that suggests the conditions under which the polarization might sort of decrease again, in which the competition between the fynbso and the forest is less intense.

Mingzhen Lu (49m 43s): Now I'll get to your question. So you nature, there are quite a few different hypo feedback mechanisms that generate macro scale pattern. So we haven't used to be looking at a self-reinforcing type of two pointing away from each other. There are the types of feedback that generate smooth coexistence, but not here, not in the south African Western Cape system. For example, let's talk about the tundra where you have shrub and grass co-exist in the same spot.

And as you traverse from zero to one in the soil gradient, your vegetation mostly change most of the time. You can certain scenario. We also expect starting foundation in Sutton parameter domain. That's our theoretical prediction. But most of the time based on most of the observation, you'll see smooth coexistence, but those are going by a different type of feedback than these that are two pointing away from each other. 

Michael Garfield (50m 43s): So maybe what you're getting at is that there is kind of a silver lining in undermining the world as we know it, that if the goal is for us to, of course, I'm just like, I'm really reaching here. But like, if the goal is for us to peacefully exist again with one another, then maybe that's just the adaptive consequence of having disrupted our environment so much that it looks more like the Tundra than it does look a rainforest. You know, that there's something about us getting to the point with civilization that we've undercut ourselves enough, that it looks like the glacier rolls in and rolls back out.

And then suddenly, you know, we all just have to find our way again together. That's kind of a squishy place to end this.

Mingzhen Lu (51m 26s): You reminded me one thing. So in nature when you've seen this type of polarization or bi-stable stays is often you have two types let’s say A and B. A and B a helping a to reestablish B, A helping B but A doesn't help B.  B doesn't have A, and this feedback will make where ever you find A wherever you find A will become stronger. And where will you find B, B will become stronger. Over time you will find the bifurcation, but in tundra it's a different type of biology happening.

So a can help B. B can help A. In the political analogy, you could be Republican, actually caring, Democrat, Democrat, actually caring.  In the tundra is so cold and so harsh, and the organism can provide shelter for organism to increase the local temperature. So it doesn't matter if your shrub doesn't matter. If your grass, as long as you have height and you have biomass, you can help your neighbor. Your province will increase your immediate, the harsh enrollment of your neighbor and this type of interaction that doesn't happen in the famous forest.

This is the opposite. Fynbos kill forest, use fire, forest kill fynbos using shading, and the only help their own, but in the Tundra, I mean, that'd be by design just by physics, by the harsh physics of the tundra plants. We are helping each other, not intentionally by forming vegetation costs that can alleviate the code.

Michael Garfield (52m 55s): So maybe the expanse has it all wrong. And actually we'll get along in space.

Mingzhen Lu (52m 59s): We should have, you should have this. Yeah.

Michael Garfield (53m 3s): Awesome, man. This is so cool, man. I love this conversation. Thank you so much for being on the show.

Mingzhen Lu (53m 7s): Thank you.

Michael Garfield (53m 10s): Thank you for listening. Complexities produced by the Santa Fe Institute, a nonprofit hub for complex system science located in the high desert of New Mexico. For more information, including transcripts research links and educational resources, or to support our science and communication efforts. Visit