Studying microbes in the frozen tundra: A great accident that feels like home
January 09, 2013
With climate change at the top of the world agenda and increasing evidence that arctic soils will play a big role in global warming, it appears as though Joshua Schimel, tundra soil scientist, recently stumbled upon a hot, new field. In fact, he’s been in it since the late 1980s, and when asked why he studies arctic soil, Schimel doesn’t hesitate: “It was all a great accident.”
It was, in fact, a string of fortuitous accidents that brought Schimel, professor at University of California-Santa Barbara, from tentative chemistry major to accomplished soil scientist. He now studies arctic microbes, including their activity during the cold winter months and the changes in their behavior as temperatures fluctuate. His life in science, however, started in a different place.
Studying chemistry in college, Schimel knew by the time he graduated that he would not find his career in that field. While he liked chemistry, the questions were not emotionally appealing to him, he says. So he looked elsewhere.
It was in his first job as a lab technician in Woods Hole, MA working with Jerry Melillo that Schimel got his first taste of soil science and field work. Melillo’s lab focused on looking at soils as part of a complete ecosystem. There, Schimel studied decomposition and denitrification, the process through which microbes change nitrogen into different forms. He liked what he was doing, but he wanted to approach the project from a more chemistry-based angle.
“I wanted to know why things work the way they do,” explains Schimel. “If you want to [do that] within the context of ecosystem ecology, you either go into plant physiological ecology or you go into soil microbiology.”
Schimel took the latter route and applied for PhD programs in soil microbiology even though he hadn’t taken a biology course since high school. He wanted to work in denitrification since he was familiar with the topic from Melillo’s lab, and he found a place in Mary Firestone’s lab at Berkeley. An unforeseen change in direction in the Firestone lab meant that Schimel never actually worked on denitrification, though. Instead he found himself studying how the organisms in soils function and drive the ecosystems. He came to realize that those questions could be answered from several angles.
“I recognized that soil microbiology isn’t really about just biology,” says Schimel. “It’s as much about soil physics, chemistry, and organic matter composition. It only gets more and more interesting that way.”
Feels like home...only a lot colder
Upon finishing his PhD, another accident was waiting to happen. As he was looking to take his next step, Schimel found a job posting from the University of Alaska-Fairbanks that seemed to be written specifically for him. While he was certain he didn’t want to move to Alaska, he applied because, as he says, it was a job. Within four days of the interview, he had to find a way to tell his mom that he was moving to Alaska. He had been immediately intrigued by the people, the atmosphere, and the opportunity for science there, and he soon found himself in Fairbanks.
In yet another turn of events, Schimel recognized that the Long-Term Ecological Research Program, a project studying arctic landscapes at Toolik Lake, AK, was run by the research group from Woods Hole with whom he had worked as a technician. They heard that he was working at the University of Alaska and invited him out to see the field station. It was there that Schimel found his place in arctic soil research.
“I came over the top of the Brooks Range, and I looked out over the tundra,” remembers Schimel. “I said to myself, ‘I think I’m home.’ And I’ve been working in the Arctic ever since. It’s just a very emotionally appealing environment for me.”
As Schimel journeyed into tundra soil science, he witnessed a change within the soil science community – the study of arctic soils year-round instead of just in the growing season. Through his work at Toolik Lake and with permafrost scientists, Schimel came to learn that even when the temperature is below zero degrees, not all of the water in the soil is frozen. Water in small pores and on the surface of soil particles stays liquid and creates water films in which the microbes can live. The idea that microbes are active in the winter was a change in thinking for many soil scientists and one that intrigued Schimel right away.
Are microbes still active when soils are frozen?
“The first thing that really kicked my interest was some data showing that carbon dioxide was elevated in the snow,” explains Schimel. “The carbon dioxide has to be coming from somewhere, so it must be from microbial metabolism. It became an almost obvious question – are the microorganisms still active when the soils are frozen?”
Many others in the field were surprised by the new research path too. Matthew Wallenstein worked with Schimel as a National Science Foundation post-doctoral fellow, and much of his arctic knowledge grew from his time in Schimel’s lab. Wallenstein also found the microbe behavior in frozen soils unexpected.
“They’re just really well adapted to their environment,” says Wallenstein. “What we perceive as extreme conditions must not be extreme to them – they function well.”
Finding out about exactly what those microbes are doing in frozen soils is what has driven Schimel’s research. Some of the first studies he undertook about 20 years ago were simple soil measurements. Soils would be sampled, put in jars, and stored in incubators. Because they wanted to keep the soils cold when they were taken in and out of the incubators, Schimel and his team went to a nearby store to buy all the foam beer can holders they could find.
Schimel laughs at the memory. “The guys at the store said, ‘You want to buy what? How many?’ They thought we were having quite the party.”
The experiments have since become more complex but no less intriguing. One of the stranger results that Schimel has seen came when he tried to look at the types of changes that were happening during the summer to winter shift. He monitored microbe behavior as the soil temperature was dropped from +10 degrees to -2 degrees. Schimel expected to see the microbes change their behavior when the temperature was around -2 degrees, after the soils had frozen, but instead their activities changed between +2 and +0.5 degrees. It looked as if the microbes were preparing themselves for the colder temperatures.
“It looked like what the microorganisms were doing was analogous to what trees do with the onset of winter. They frost harden, and they do it before it freezes,” says Schimel. “At first we thought this was really surprising – the microbes seem to know it’s about to freeze. Then we realized it shouldn’t be such a surprise. The microbes have been living in these soils for millions of years. If freezing is a stress, of course they’ll respond to the cold that they have learned comes before the freeze.”
Microbes and climate change
With the adjustments that microbes make based upon the temperature, it is easy to see how microbial research in frozen soils is closely linked with global climate change concerns. In the summer, plants take up carbon dioxide to use for photosynthesis, and the microbes in the soil pump carbon dioxide back out into the atmosphere. The processes in summer are well balanced because plants are active. In the winter, however, the lack of plant activity means that the carbon is only going one direction – out into the atmosphere. Because microbial activity is extremely sensitive to temperature changes in ranges below zero, small increases in the soil temperature during arctic winters could affect carbon output.
“If you warm soils by just a degree or two in that range below zero, you can increase activities enormously,” explains Schimel. “And if soils warm more during the winter, which they’re expected to do, big changes could occur. There’s about twice as much carbon tied up in cold soils as there is in the atmosphere. Modest losses of carbon from the soils could be a big deal.”
Schimel is now at the University of California-Santa Barbara, and in addition to his tundra soil research, he plays a large part in graduate student and post-doc training, science communication education, service activities, and collaborations with other laboratories. Through his work as an academic, he has found the home he was missing as a chemistry major in college.
“It’s hard to imagine what I would be doing if not this,” says Schimel. “I got here by accident, so if accidents had worked other ways, I imagine there would be other outcomes – maybe equally rewarding or maybe not. It’s the ‘maybe not’ that’s always scary.”
Wallenstein, Schimel’s former post-doc, is an assistant professor at Colorado State University, and he is certainly happy that Schimel found his way to academia. The two still work on projects and proposals together, and they often team up to write conceptual papers and syntheses. Wallenstein makes it clear that collaboration is an important part of soil science.
“The nature of soil science is that it is very interdisciplinary,” explains Wallenstein. “I really rely on good collaborators to add their expertise and provide a product that is more than the sum of the contributions of each member. Josh is an important contributor.”
Schimel returns the sentiment saying, “I continue to work with Matt because he is leading the charge and has developed tool kits and techniques that I want to tap into. It’s great to see his success as he takes on leadership roles.”
While Schimel has high praise for his former post-doc, Wallenstein says that he seems to find his former mentor one step ahead of him much of the time. “Every time I think I have a new, original idea, I realize that Josh already not only thought of the same idea, but did the research and reported it years ago,” Wallenstein says laughing. “I can’t tell you how many times that has happened. And I don’t think I’m alone – I think many people in our field feel like that.”
While others in his field may think he has all the answers, Schimel says it’s actually the puzzle of science that keeps him excited about arctic soils research. “I’ll go ten years knowing more and more about a topic and understanding it less and less. You start to see the contradictions, and you can’t quite see the pattern that ties them all together. Then at some point, something slips into place, and you see how it all works. Then you start the process over again. I think that is what moves us all forward as scientists.”
This story appears in the January-February issue of Soil Horizons.