Colorado researchers are studying how soil rebuilds after wildfires

In a lab at the Colorado School of Mines is a large, oven-sized box. Environmental microbiology professor John Spear opens the door and throws in a sample of ash from a Colorado fire before lighting it. It sounds like an airplane engine, but this machine has a completely different function.

It’s a scanning electron microscope,” Spear explained. “And we can see things that are very small. This microscope is going to magnify things 10,000 times, and we don’t know what we’re going to see until we put it in there.”

He is on the hunt for microbes, tiny creatures that are invisible to the naked eye and exist all around us, including bacteria, fungi and viruses. They are critical to nutrient cycling to create healthy soil for plants to grow – and regrow. But wildfires can burn up too 96% of them, as researchers at Colorado State University have shown. With this microscope, Spear can see which cells are left.

    John Spear, a researcher and professor at the Colorado School of Mines, places the ash sample under the scanning electron microscope.  It enlarges the sample so he can look for microbes.
John Spear, a researcher and professor at the Colorado School of Mines, places the ash sample under the scanning electron microscope. It enlarges the sample so he can look for microbes.

“When you look at an image like this, you’re just trying to diagnose what’s in front of your eyes,” he said, viewing the magnified ash sample on his computer. “It looks like moon sand. [But] It’s a whole mix of minerals, microbes, ash – stuff that comes from the fire itself. And all of this right here makes up a new kind of earth.”

A window into this “new kind of soil” is becoming increasingly important as wildfire season lasts longer in the West. The fires are burning hotter and covering more area — about 7 million acres, according to reports so far this year Data from the National Interagency Fire Center.

“When fire burns the ground, it takes a native ecosystem and changes it really drastically,” Spear said. “It’s a big disruption.”

Spear’s team wants to understand how the ground handles it. By analyzing microbial survival and activity deep in the soil, he hopes to gain insight into how soil repairs itself in charred soil.

“So the goal is, can we predict the outcome of a fire before it happens?” he said. “Can we predict how quickly a bottom will become a bottom again after this drastic disruption?”

His team started testing in 2016. Since then, they’ve looked at three Colorado fires: the 416 Fire, the Decker Fire, and the Marshall Fire. Their first research results were already published in June Applied and environmental microbiology.

Spear said this research may help preserve soil quality as climate change bakes Mountain West.

“Fire is with us,” Spear said. “We need to understand how this is affecting our entire ecosystem around us because that’s going to affect our water quality, the way we grow food and how we can live, recover and be close to a forest.”

In search of microbes

In order to analyze the ground, Spear’s team must first collect it. They visit burn scars about a week after a fire has cooled.

    Carmen Villaruel, a graduate student at the Colorado School of Mines, places the test tubes in the centrifuge.
Carmen Villaruel, a graduate student at the Colorado School of Mines, places the test tubes in the centrifuge.

“We literally go in there with a spatula that we sterilize and we scoop up the soil and put it in tubes and freeze it in the field and then we bring it back and extract DNA from it. ‘ Spear said.

The DNA analysis is the task of Carmen Villaruel. She is a graduate student at the Colorado School of Mines doing soil testing. She starts by putting the tubes in a bead beater.

“I’ve already put ashes and earth in it [the tubes], but they have these really tiny silica beads inside them,” Villaruel explained. “We can fill the soil with some lysis solution and then stir it up. So it (the bead beater) just shakes it around to create many different shear forces to break different cells apart.”

The next step is to put the tubes in a centrifuge to separate the solid parts of the solution from the liquid.

This separation allows us to separate the pearls and the earth chunks and debris,” Villaruel said. “And our DNA is now suspended in the liquid.”

For them, this research is personal. Growing up in California, she lived with the effects of wildfires.

“I want to be involved in figuring out how we can rehabilitate these areas afterwards,” Villaruel said. “How will communities recover, especially as these fires continue to move into this wild urban intersection?”

Help forests to recover

The research is still in its early stages, but Spear was surprised at how quickly microbes recover, even after fires have robbed many nutrients from the soil.

“Even at moderate and high levels of severity, the microbes are back and working within a few days,” Spear said.

Spear's team is looking for microbes, those tiny cells that the human eye can't see.  This microscope helps his team see these cells up close.
Spear’s team is looking for microbes, those tiny cells that the human eye can’t see. This microscope helps his team see these cells up close.

They mine and rebuild scorched earth. With this information, Spear’s team can use a process called statistical learning to predict how the soil will recover over time.

“Statistical learning will help you predict that X number of microbes will give you this type of response, and the microbes can actually help you predict soil chemistry, too,” Spear said. “You really think about what the carbon is doing, what the nitrogen is doing in the soil.”

Michael Wilkins is another researcher studying how wildfires affect the soil microbiome. He is an associate professor of soil and plant sciences at Colorado State University, and his work examines what exactly the microbes in the soil are doing.

    This bead beater looks and works much like a blender you'd find in your kitchen, but it actually helps rip the cells apart so Spears' team can extract the DNA.
This bead beater looks and works much like a blender you’d find in your kitchen, but it actually helps rip the cells apart so Spears’ team can extract the DNA.

“We can look at the molecules that the microbes are producing, and that gives us an indication of which ones are actually active and which ones are sitting there doing nothing said Wilkins. “We can basically reconstruct these genomes of hundreds of different microbes and figure out how they might interact and what processes they perform.”

So far he has found that some of the microbes can partially regrow after a fire because they produce spores that make them more heat resistant.

“After the fire, these little spores can be revived, and the bacteria can come back out of these spore structures,” Wilkins said. “So that was a key strategy that many of the microbes use to survive in these conditions.”

Trees and other plants are often seeded with different microorganisms to encourage growth, and Wilkins said this research can help pinpoint exactly which microbes are best suited to help wildfire-hit landscapes recover .

“If we plant trees in these badly burned ecosystems, we could supplement them with microbes that could really improve the growth of the trees and the survivability of those seedlings,” Wilkins said.

Subsequent Consequences

But there is much more to forest resilience to megafires than just soil microbes.

    Chuck Rhoades, a biogeochemist at the US Forest Service's Rocky Mountain Research Station.
Chuck Rhoades, a biogeochemist at the US Forest Service’s Rocky Mountain Research Station.

Chuck Rhoades is a biogeochemist with the US Forest Service Rocky Mountain Research Station. His work focuses on how the entire ecosystem builds itself and whether it builds up as would be expected in a less disturbed forest.

“It’s not necessarily just about whether the floor works or not; it’s whether the plants make it back to the site,” said Rhoades.

The ecosystem would recover and forests would regenerate on their own if the fire season were shorter and less severe, Rhoades said, but now climate change is affecting the types of plants that can support those areas.

“Places that used to be forest may not be forests in the future,” Rhoades said. “These severe fire seasons can send vegetation in directions that may not look the way they did before and it can take a very long time.”

When trees aren’t given a chance to regrow, harmful nutrients can more easily slip through burnt soil, contaminating water and increasing the likelihood of algal blooms.

“You can think of the trees as a kind of filter or sponge that traps nutrients and retains them at high elevations in the forest itself,” Rhoades said. “If we see severe wildfires in those areas, and those areas aren’t revegetated, we should expect that we can have downstream consequences.”

These fires – and their effects – will not go away. But Spear said his microbial research could help us adapt.

We used to have fire season in Colorado. Now we have annual fire. It’s fire season all the time,” Spear said. “If we can better understand how to manage fire and manage the recovery process through understanding the soil, that will be invaluable to me.”

This story was produced by Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, the O’Connor Center for the Rocky Mountain West in Montana, KUNC in Colorado, KUNM in New Mexico, with support from affiliated stations throughout the region. The Mountain West News Bureau is funded in part by the Corporation for Public Broadcasting.

Copyright 2022 KUNC. To see more, visit KUNC.

Source