Springtime Brings Unexpected Blooms
Look around and the signs of spring are obvious. Here in the Northeast, magnolia trees are budding, Forsythia bushes are exploding with yellow flowers, and songbirds are starting to come ‘round. But there’s another side of the season you may not have noticed—the deep, dark underworld of spring, where soil-dwelling microbes feast and explode in number.
Noah Fierer, a microbial ecologist, says he swoons for the scent of that bacterial bloom. “To soil biologists it just brings us to our knees. It’s better than the finest perfume or cologne, that smell of microbial activity, of microbes doing their thing.”
This drama of springtime soil plays out in even the driest, most desolate places. Science Friday’s collaborator Christian Baker drove to Death Valley to witness the park’s “superbloom,” a massive floral show that happens only when soil-bound seeds are soaked with enough rain to sense they might have a fighting chance as a sprout. This year’s El Nino rains moistened the desert enough to produce what Baker describes as “a two-mile-long field of gold, dancing in the sun.” See it for yourself in his video.
Noah Fierer is a microbial ecologist and an associate professor at the University of Colorado in Boulder.
Christian Baker is an independent filmmaker, producer and director of photography.
IRA FLATOW: This is Science Friday. I’m Ira Flatow. There are lots of ways of celebrating spring– take long stroll, stroll along the beach, watch March Madness. Or, put your nose to the ground, in the deep dark underworld of soil.
Microbes also celebrate springtime. And you can find them if you know what to look for. Or, I should say if you know what to smell for. Noah Fear is a microbial ecologist, associate professor at the University of Colorado in Boulder. Welcome to Science Friday.
NOAH FIERER: Hi, Ira. Thanks for having me on the show.
IRA FLATOW: Do you actually smell the ground, Noah?
NOAH FIERER: Oh, it’s a glorious smell.
IRA FLATOW: You got to describe that better. What is it, is it like roses? Is it like fresh-cut flowers? Is it like breakfast? What does it smell like?
NOAH FIERER: It’s that smell of wet soil, that smell that most of us are probably familiar with, that smell of springtime, the smell of soil. And really, what we’re smelling in most cases actually the product of microbial activity, these microscopic organisms that are essentially very active in the springtime and feeding, and it’s that smell, only some of those compounds which we can actually detect with our relatively crude sense of smell. That’s what gives that sort of characteristic, wet, earthy smell.
IRA FLATOW: So the microbiome is hard at work down there, under the soil in the spring.
NOAH FIERER: Exactly, and the microbes are still active in the wintertime. So unlike us that use the wintertime as an opportunity to huddle inside with some hot chocolate, microbes are still active in the wintertime doing what they do, for example, degrading plant material. But as soon as spring arrives, everything sort of ramps up and the microbes become more active.
IRA FLATOW: Now, soil microbes are famous for being a source of antibiotics. We know that people are always trying to find new antibiotics from the soil microbes. Would this time of you be an especially good time to test the soil for these novel compounds?
NOAH FIERER: Yes, exactly. So as spring arrives, we typically have more water, higher temperatures. And there’s also more food available to those microbes. And a lot of that food is coming from plant roots. So although we may not see a lot of plant biomass above ground or plant leaves, the roots in soil, the plant roots are already starting to release a lot of food or carbon compounds for the microbes to eat.
And that can trigger some competition between microbes for these scarce resources. And part of that competition entails the production of antibiotics. So there are fungi and there’s bacteria that will produce antibiotics to kill other bacteria. So it’s kind of like Thanksgiving dinner, a highly competitive Thanksgiving dinner.
IRA FLATOW: You need a boarding house reach for the microbiome bacteria. It never struck me before, why are there antibiotics being made in the soil? Because the microbes are fighting each other.
NOAH FIERER: Well, exactly. Microbes are tough. But it’s also a difficult place to live. There are often limited resources. And those resources that are available, they’re going to compete for them. So they’ll produce compounds to kill their neighbors, for example.
IRA FLATOW: You did a study about Central Park soil a few years ago. What did you learn from that?
NOAH FIERER: One of the big take-home messages from that study is, we sampled soils from throughout Central Park. And we chose Central Park because it’s a park that’s visited by millions of people a year, fairly familiar. Yet when we start looking in the soils from Central Park, we find enormous amounts of microbial diversity. So thousands of different species of bacteria and fungi as well as other microscopic organisms. And what was surprising is most of these organisms are undescribed. We know they’re living in soil, but we don’t know what they’re doing. We don’t have names for them. And I think that study just really emphasized how little we know about the diversity that’s found in soil.
IRA FLATOW: So could some of that diversity be coming from the New Yorkers and all the tourists who come sit on the rocks in Central Park?
NOAH FIERER: Potentially. But the organisms that we see in Central Park soils are actually pretty typical to what we see in soils from all over the world. So yeah, there are some bacteria and some other organisms that are going to be coming from the visitors to Central Park. Most of them are growing there and just inhabit the soil.
IRA FLATOW: I know how difficult– it’s very difficult to take the microbes– excuse me– out of the soil and bring them into the laboratory to study, is it not? 90% of them don’t survive on their own in the laboratory.
NOAH FIERER: Yeah, there’s just this amazing number of bacteria and fungi and other microorganisms that we can use techniques like DNA sequencing and so forth to see that they’re in soil. But it’s very hard to isolate them and study them in the lab and figure out what they like to eat, what environmental conditions they like to grow under. So it’s really terra incognita. There’s really a lot of unknowns about what sort of organisms are in soil and what they’re doing in soil and how they may play a role in, for example, soil fertility.
IRA FLATOW: So what can we as gardeners– and I’m an avid gardener– what can I do to the soil to help those that microbiome in the soil this time of year?
NOAH FIERER: The one thing is, they are going to be more active. They’re getting more food available to them. You’ve got these higher temperatures. You’ve got a lot of moisture. And they’re going to be doing what they do. They’re going to be degrading plant material, some of it left over from the fall. They’re going to be producing these antibiotics. They’re going to be reproducing and growing. And they’re tough. Sometimes they’ll just keep going along. They don’t need a lot of help from us.
IRA FLATOW: You sound like you have such a romance with the soil, and I don’t blame you. I know that smell. I know the feel of getting your hands in the soil. When did you first understand and discover that you were a soil person?
NOAH FIERER: Primarily just due to how little we know about soil. Obviously, soil is very important to growing crops, to our gardens, to our natural ecosystems, and even to our lawns. We don’t think about the lawn soil very much. But we know surprisingly little about what organisms are in soil, how they’re interacting with one another, how they may be responding to changes in precipitation or changes in temperature and things like that. So what’s appealing to me is just how little we know about this environment that we literally walk on almost every day.
IRA FLATOW: And how does the microbiome affect seeds that drop into the soil?
NOAH FIERER: So that’s what’s interesting. So you mentioned– we were talking about the smell of soil, this ambrosia to soil biologists. In my opinion, it’s better than the finest perfume or cologne, this smell of microbes that are active in soil, producing all these different compounds. But we do know that some of those compounds can actually serve as an alarm clock to plants. And they can trigger, for example, germination of seeds.
So whether that’s a direct or indirect action, these smells are doing more than just appealing to our own senses. They can also trigger plant responses, for example.
IRA FLATOW: Is there any way to make it more healthy, or are there things that we do to work to hurt the microbes in the soil? I remember we heard of a study a while back that actually plowing or tilling the field actually wrecks the microbiome that you don’t want to do. It’s better to just stick the seed in the soil.
NOAH FIERER: Yeah, exactly. There’s a lot of things we do to our soil– applying pesticides, tilling the soil that can alter the types of organisms and disrupt some of the food webs in soil. So the key is really to supply that organic matter back into the soil, give the microbes food to eat, and try not to disturb them that much.
But that question is a good one, is how do we actively start managing the organisms in soil to promote plant health, for example. And that’s a question that’s very much– people are really diving into that now and trying to figure out how can we start manipulating organisms in soil to make that soil more fertile?
IRA FLATOW: Is there any way– you said we know so little about– you mentioned Central Park and there’s so many microbes in there that we’ve never seen before. Is there any way to catalog any of these unknown microbes?
NOAH FIERER: There’s lots of efforts underway right now to catalog the diversity of organisms in soil, and not only the microbes, not only the bacteria and fungi, but also the nematodes, these minuscule worms, the insects and other arthropods and so forth. And a lot of that surveying is being done using DNA sequencing technologies that allow us to get a glimpse of at least who’s there. And that’s really the first step, is start seeing what types of organisms do we find in soil and how do those types change across different soil types or different management strategies and stuff like that.
IRA FLATOW: There are lots of ways of celebrating spring. I want to bring on someone else now. This drama of springtime soil plays out in even the driest, most desolate places. And this year’s El Nino rains delivered enough rain to Death Valley– this was really interesting– to produce what’s known as a super bloom. And we sent our collaborator, Christian Baker, to check it out. Christian is an independent filmmaker and producer based in Los Angeles. Welcome back to Science Friday, Christian.
CHRISTIAN BAKER: Hi, Ira. How’s it going?
IRA FLATOW: Tell us first of all, what is this thing called the super bloom and what does it look like?
CHRISTIAN BAKER: It is awesome. Let me just say that. A super bloom is an above-average of desert wild flowers. It is, in years of heavier precipitation in Death Valley, there is– rainfall will tap deep into the seed bank, this massive seed bank in the valley floor.
And what results is what I can only describe as a field of dancing, golden wonder. It’s just beautiful. But I should also point out that super bloom is an unofficial term. So I personally would like to try and get that on the books as the official term. I think that would be great.
IRA FLATOW: Let’s start the meme super bloom, or hashtag at superbloom or something. Get it to go viral. Why are the super blooms so rare? Is there a minimum amount of rainfall needed to kickstart one of these?
CHRISTIAN BAKER: Yes. Well, Death Valley on average gets less than three inches of rain annually. But what happens is in years of heavier rain, especially years of heavier winter rain, that moisture will soak deeper into the soil. So if picture beneath the soil– we get into this a little bit in the video– there’s just this massive seed bank. Now, seeds might be an inch to three inches under the surface of the soil, or they may be up to, like, 16 inches or even deeper.
And in a year of average rainfall, moisture will only seep so far down into the soil. So in years of heavier rain, you get moisture that soaks obviously much deeper and cap tap into these seeds that are buried deeper down. Now, to go a step further with that, if you want, I can talk about the coating on the seed.
IRA FLATOW: Sure.
CHRISTIAN BAKER: So these seeds in the desert kind of come equipped with a natural insurance policy. So what you don’t want is to get a little bit of rain and to start growing. Because then there’s not going to be enough moisture to support a full life cycle. But if you get a lot of rain, these seeds have this coating that’s a prohibitive coating. It prevents them from growing or sprouting too early.
And if they get enough water, the water will actually erode the coating. And then once this coating, which is sort of made of a wax or a protein or it could even be like a natural chemical base, once that coating is eroded, then the seed can actually germinate. And presumably, there’s enough moisture available that it will support its full life cycle and allow it to deposit more seeds for future blooms.
IRA FLATOW: And you mentioned the video. Christian, you mentioned a video. It’s up on our website at ScienceFriday.com. And it’s a gorgeous video. You can’t do it– going out there, I’m very jealous. You go out there and [INAUDIBLE]. Let me just tell everybody I’m Ira Flatow. This is Science Friday from PRI, Public Radio International. Noah, if there’s a super bloom going on above the ground, is there a microbial version going on in the soil?
NOAH FIERER: Oh, for sure. As the name Death Valley would suggest, we think of it as being very inhospitable to life. But to microbes, they can do just fine in Death Valley. Because a lot of them are tolerant of the conditions that the soils in Death Valley experience, and they can kind of stay dormant. They can stay dormant for days to weeks to months, even decades, and wait for those right conditions that large rain event, for example, and really start growing in that short window of time when they can be active.
IRA FLATOW: There was an article out this week by Jim Robinson, in Yale Environment 360 in which he writes about the uncertainty facing the world’s microbes as the climate changes. Is that a concern of yours, Noah?
NOAH FIERER: Oh, for sure. We know these soil microorganisms do a lot of important things for us, from growing crops to cycling carbon in natural ecosystems. What remains to be determined is, how are they going to respond to climate change? We’re starting to get a handle on how plants and animals may respond to climate change. But when it comes to understanding how the soil microbes are going to respond to climate change and how that may impact our ecosystems, it’s a big unknown. And we’re really just starting to figure that out.
IRA FLATOW: Christian, what’s the future of the super bloom? Do you think you’ll see another one in your lifetime?
CHRISTIAN BAKER: That is definitely the hope. I do know that the issue of the drought in Southern California– we’re in the midst of a four-year-long drought. That could be impacting future super blooms. However, I’ve gotten mixed answers from the various people that I’ve spoken to, various botanists and park rangers and whatnot. So on the one hand, people are very optimistic that we will see another super bloom. It just could take a few years. It could take a few decades.
IRA FLATOW: Is it over? Is it too late for us to get on a plane and get out there and see it?
CHRISTIAN BAKER: Unfortunately, they were hoping for greater rains in the last few weeks earlier this month. I think there were supposed to be some storms that were going to pass through Death Valley. Unfortunately, that did not happen. That would have kickstarted another wave of bloomage, if you want to put it that way. But the rains did not come. However, I checked the website right before we got on the radio, and I do believe there’s some cactus blooming now. So there’s always a little bit of life out there.
IRA FLATOW: Cactus bloom is gorgeous stuff. And [? ever you ?] know, the desert always blooms earlier than everything else, for some reason. Noah, what’s going on there?
NOAH FIERER: Well, it just depends on when that moisture is available. Obviously, they have plenty of sunlight in the desert, at least most times. It’s just waiting for that pulse of moisture to enter the soil, and everything really springs into action. All the microbes, the plants, the whole soil food web really starts ramping up.
IRA FLATOW: Well, Christian. It’s a great video. It’s up there on our website at ScienceFriday.com. Thank you for taking such beautiful pictures.
CHRISTIAN BAKER: Thank you. My pleasure.
IRA FLATOW: And bringing it home as much as anyone can, I’m sure trying to capture that giant scope of many miles of flowers blooming. Noah, have you ever seen one– super bloom?
NOAH FIERER: I have, actually. It was in, I believe, around 2000, 2001. It was very impressive.
IRA FLATOW: 15 years between blooms is a while. Worth waiting for. Thank you, gentlemen. Thank you both for taking time to be with us today.
NOAH FIERER: Thank you, Ira.
IRA FLATOW: Noah Fierer is a microbial ecologist, associate professor at the University of Colorado in Boulder. Christian Baker is an independent filmmaker and a producer based out in LA. And if you want to see the super bloom, you can check out his video on our homepage at ScienceFriday.com.