Burning questions: The mysteries of pyrogenic carbon and the effects of prescribed fire on soil

When you think of a forest on fire, you aren’t usually thinking about what’s happening in the soil- but graduate student Ali Moss is. The Spencer Research Grant winner and Warnell School of Forestry and Natural Resources student’s research investigates the relationship between prescribed fire and carbon cycling, specifically studying an organic material known as pyrogenic carbon. This form of organic carbon appears when soil interacts with fire, and Moss intends to learn its secrets.

Soils are beautiful! Moss examines soils collected immediately after the prescribed burn in April 2021. In the background, pyrogenic carbon from burned grasses and litter blankets the soil surface.

“One of the big areas of mystery is that pyrogenic carbon is present in rivers, and is travelling from rivers to the ocean,” Moss said, “but we don’t really understand the details of how it moves from soil to waterways, and we don’t really understand how it becomes dissolved.” Pyrogenic carbon tends to persist in soil longer than unburned organic matter. Researchers originally thought that this was because microbes couldn’t break down pyrogenic carbon, but this since been disputed.

“We know that pyrogenic carbon is harder for microorganisms to decompose than regular organic matter,” Moss explained. “But it’s always a mistake to underestimate microorganisms, because they can do, like, anything.” Moving forward, Moss hopes to characterize dissolved pyrogenic carbon in South Georgia forests managed with prescribed fire, and figure out how it makes its way into water.

There are several moving parts to this research: Moss and their team pull soil cores to get a profile of organic matter at different soil depths. Then, to investigate the connections between carbon in the soil and in the water, they pull water samples directly from the soil using lysimeters. They also do extractions of soil in water in order to test and compare two different methods for studying dissolved pyrogenic carbon in soil.

A field of lysimeters installed in the burned stand of forest immediately after the prescribed fire, April 2021. A lysimeter is a device used to measure evapotranspiration by recording the amount of water percolating through soil.

Another major question is simply how long pyrogenic carbon can last in the soil after a burn. “Because pyrogenic carbon hangs out in the soil longer, it might be an important carbon sink,” Moss said, explaining how carbon, pulled from the atmosphere by plants, may remain sequestered in the soil longer after it has been exposed to fire. “Some pyrogenic carbon does hang out in the soils for millennia, but most of it is probably cycling out within decades or centuries. So what are the controls on this? How can we get a better idea of what kind of sink pyrogenic carbon is and how would we quantify that?”

The experiment is currently underway near Tifton, Georgia and compares two stands of longleaf pine trees, one of which is not managed with fire, and one where Moss and their team performed a prescribed fire back in April of 2021. Prescribed fire is a forestry management technique that involves strategic burning. The practice brings a lot of known environmental benefits that are still being explored—and Moss is a big fan. “I think prescribed fire is awesome.” Moss said. “Getting to participate in prescribed fire I felt was really cool…It’s a really powerful tool.”

The prescribed fire in April 2021, shortly after ignition: a backing fire crawls through the understory with low intensity.

Part of her interest in the project stems from this enthusiasm for prescribed fire. “Despite its importance as a land management tool,” Moss said in their Spencer Research Grant proposal, “prescribed fire science remains underfunded compared to wildfire science, resulting in many knowledge gaps.”

Moss hopes her research may one day help inform forest managers how to regulate carbon through fire. “I love to talk to people about prescribed fires and spread the word about how awesome prescribed fire is.”

Ali Moss in March 2021, assessing fuel composition before the prescribed fire.

Moss’s research is funded by the Warnell School of Forestry and Natural Resources as well as a 2022 Spencer Research Grant. The grant is an annual award given to graduate students studying freshwater resource management and conservation. It is named for the late John Kyle Spencer, an Odum graduate student who was passionate about freshwater research. Moss’s project reflects a love for ecological science and conservation-focused management techniques.

Photos provided by Ali Moss. Story by Olivia Allen.

Rasmussen, Jackson offer expertise in documentary series

The Weather Channel featured Todd Rasmussen, River Basin Center affiliate and Warnell School of Forestry and Natural Resources professor, in its series, “The Earth Unlocked,” a segment that explores the power of water, volcanoes, desserts and hurricanes. The eight-episode series concluded in July. Catch the trailer—and hear Rasmussen discuss his area of research, hydrology—here.

Rhett Jackson, River Basin Center affiliate and Warnell School of Forestry and Natural Resources professor, contributed expertise on the Okefenokee Swamp and the Chattahoochee River in three episodes of GPB’s “View Finders,” a show that highlights Georgia’s most beautiful natural features. Learn more about the series here.

Part 1: On the Road—and the River—with the Ecological Problem Solving Class

Across three state and three rivers: An experiential learning journey

Science doesn’t—and shouldn’t—happen in a vacuum. Amanda Rugenski, lecturer and undergraduate coordinator at the University of Georgia Odum School of Ecology, gets that. 

“To be able to listen to people is really important, not just to the scientists, not just to the water managers, but also to the communities that are present in these areas,” she said.

She hopes the question of who needs to have a seat at the table is something students take away from the Maymester study away course she led (ECOL 3300, Field Program in Ecological Problem Solving), from May 21 to June 4, 2022, with the assistance of Odum graduate students Kristen Zemaitis and Jeffrey Beauvais. 

Rugenski’s class of 19 had ample opportunity to practice listening as they attended presentations and hands-on workshops throughout swaths of the Apalachicola-Chattahoochee-Flint (ACF) River Basin, learning to view environmental issues through a social-ecological lens.

Ecological Problem Solving is an experiential learning course offered annually for Ecology A.B. students, and it’s an anchor course for the Sustainability Certificate. The class is meant to give students a whirlwind introduction to problem solving at the intersection of science, society, and policy. The course is built around one such issue—the tri-state “Water Wars”—and the efforts of a regional organization, the ACF Stakeholders, Inc., to provide solutions through consensus. 

For several decades, Georgia, Alabama, and Florida have disputed water allocation in the ACF Basin. Georgia needs water to support both agriculture in the southern part of the state and the continued growth of Atlanta in the north. Alabama requires water for power, drinking supply, and fisheries, and Florida needs enough water to reach the coast to prevent saltwater intrusion and to sustain its seafood industry.

In response, the ACF Stakeholders—composed of a range of people including civic leaders, farmers, fishermen and researchers across sectors and state lines—aims to foster informed, cooperative and equitable water sharing. 

The group’s goals dovetail perfectly with those of the class. To Rugenski, the organization is illustrative of a critical point. 

“Sometimes when we think of problem solving, people don’t think of humans as being a part of the solution, and others may not think of the environment and ecosystem as being part of the solution. I want students to see how interconnected these all are, to solve these complex problems,” said Rugenski.

Out of the classroom and into the creek: Field experience at the Jones Center

The group experienced the ACF basin from its headwaters to the Gulf Coast, traveling a roughly 1,000-mile loop and visiting as many of the ACF stakeholders as possible along the way to learn first-hand about their perspectives and priorities. Their travels included stops to sample fish in the Chestatee River in North Georgia, a visit from an attorney with the Southern Environmental Law Center, a tour of the AgLanta Urban Food Forest at Browns Mill, and a meeting with the West Atlanta Watershed Association.

The group swept through Florida, with highlights including a stop at the Apalachicola National Estuarine Research Reserve, a visit from Dr. Brooke, who presented on the Apalachicola Bay System Initiative and a tour of the bay by boat to learn about restoration projects along Highway 98.

By Memorial Day, the class had wound its way back to southern Georgia, to the Jones Center at Ichauway.

Aquatic biologist Steve Golladay welcomed them to the reserve, or what he calls “30,000 acres of green in a sea of agriculture,” and presented background about the research center and the scope of natural resource management in Georgia.

The center’s threefold focus is on water—the unique hydrology of the mostly free flowing Flint River and its tributary, Ichawaynochaway Creek; woods—preserving its longleaf pine ecosystem; and wildlife—protecting the roughly 1,200 species present on the reserve, partially supported by its isolated wetlands.

On paper, Georgia is a freshwater-rich area, Golladay shared, with an average of about 50 inches of rainwater a year. That’s well above the national average. And the Flint—15 miles of which wends through Ichauway—is partially fed by the rapidly recharging Floridan aquifer, not just runoff and seepage. That makes it an especially reliable source of freshwater.

The challenge is that no single year gets the average amount of rainfall. Some years see 70 inches and others see 30—sometimes several years in a row, leading to periods of stress on water systems and periods of abundance. Sensibly bridging the gap between the two is a major water management goal. 

The Jones Center supports some of the most robust research on longleaf pine management in the country. Of the 30,000 acres on the ecological reserve, longleaf pine forest makes up about 18,000.

A habitat type that once spanned between 60 to 90 million acres of land in the southeastern United States prior to European colonization, longleaf ecosystems are reduced to about four and a half million acres today.

Ichauway’s second-growth pine is now mature, at 80 to 100 years old. It’s the perfect tree cover for Georgia’s on-again, off-again water supply: longleaf pine stops pumping water in drought years. It offers the benefits of forestation without straining water systems in times of water scarcity.

A large part of the center’s mission is providing access to its findings and the physical space itself.

Students head toward the creek.

That’s why, when his presentation was over, Golladay took the students to Ichawaynochaway Creek to go “mussel hugging,” a term he uses to encompass both the process of finding and identifying mussels and the unbridled enthusiasm with which he feels that task should be undertaken.

Golladay lectures from Ichawaynochaway Creek, camera in-hand.

Graduate student Jamie Rogers and research associate Caitlin Sweeney, with the help of student volunteers, set up a kick net and searched for critters. The water was clouded, but the murky flow was actually the result of staining from swamps up river, Golladay explained. It’s normally quite clear, with visibility sometimes reaching 15 feet.

Jamie Rogers and Caitlin Sweeney demonstrate how to use a kick net to gather samples.

Though no mussels were found, students discovered minnows, small fish, insects and several crayfish. It’s the kind of field experience and tactile learning that Golladay says the center is all about.

“I think one of the things that we offer at Ichauway is a real field experience. We’re all field-oriented, and so it gives people a chance to come and stay here, to see what we do out in the world. Especially now, given that we’re coming out of two years of virtual learning, the role of places like Ichawauy has become extremely important,” Golladay said.

Tina Vu inspects a net for insects, her favorite critters.

And students were conscious of that. For class member Alanna Deveter, the interactive nature of the course wasn’t just a perk—it was integral to her learning experience.

“I definitely prefer this type of learning environment to just sitting in a classroom,” she shared. “I have a pretty busy brain. So hands-on works for me. It’s an actual experience where I get to have my own perspective.”

And with each stop, students’ perspectives became more and more informed.

This kind of experiential learning is available to all A.B Ecology majors and students pursuing the Sustainability Certificate. Current and prospective students can learn more here.

Check back soon to read about the students’ stop at the Albany State’s Water Policy Center, UGA’s Stripling Center and the Flint RiverQuarium!

Laura Naslund, sitting in a canoe on a pond, smiles while taking emissions data.

A Day in the Life of a Pond: Measuring Small-Reservoir Emissions to Inform Infrastructure Decisions

By 7:45 a.m. on Tuesday, June 21, Laura Naslund had already spent over an hour in a canoe on a little pond on the east side of Athens, Georgia. Naslund, a graduate student in the Odum School of Ecology and a 2022 Spencer Grant recipient, was finishing up the first field sampling event of her new research project. She’d started work early on Monday morning, and was still paddling a canoe out to measure gas emissions all over the pond 24 hours later.

“The idea is to understand the times, places and pathways that are most important for emissions,” Naslund said over a quick breakfast, “and then apply that information to a later study at more sites which examines the drivers of the differences in emissions between sites.” 

There are 364 reservoirs in Athens-Clarke County, but only 23 of them are listed in the National Inventory of Dams, leaving hundreds of smaller reservoirs that receive far less attention from freshwater research and management alike.

Laura Naslund and volunteer assistant Ally Whiteis paddle a canoe across a small pond for field sampling.
Laura Naslund and volunteer assistant Ally Whiteis paddle a canoe across a small pond for sampling, around the 2-hour mark of the 24-hour field sampling.

Naslund believes these small reservoirs may have a much larger impact on inland water systems than we currently recognize. She hopes to expand our understanding of freshwater reservoir emissions by focusing research attention on the small ponds of Athens. The end goal of Naslund’s research is to help inform infrastructure decisions regarding which of these dams have the greatest environmental impact and which may be highest priority for removal.

“Particularly as we are about to have the largest infrastructure investment probably in my lifetime, I think now’s a good time to start thinking about how we can use ecological knowledge to inform where and what kind of infrastructure we have,” she explained. “And this project, I think, is a little bit unique among that body of work in that it’s focused on the end of an infrastructure life cycle.”

Naslund is particularly dedicated to accurate field testing: data collection for this research will involve sampling all over each test reservoir for over 24 hours at each event. These methods were designed to get the most accurate possible understanding of where, when and how gases are emitted throughout a day.

Laura Naslund paddles a canoe across a wollfia-covered pond.
Laura Naslund paddles a canoe across a wollfia-covered pond, around the 6-hour mark of her 24-hour field sampling.

“I think researchers have thought about spatial variation a lot, we’ve thought about seasonal variation a lot, but we’ve though less about the variation in emissions that happens over the course of a single day,” Naslund explained. By focusing on variation at a daily scale, Naslund hopes to collect emissions data that more accurately represents the natural history and spatial heterogeneity of a system.

It’s strenuous work to sample for 30 hours at a time, but Naslund doesn’t mind camping out. “The places that I’m working in are beautiful. So that always helps!”

She also acknowledged that she could not do this research alone. Her team of volunteer assistants included professors, undergraduates, and fellow graduate students, who came in shifts throughout the 30-hour sampling. “It’s been really great to collaborate with people, to show them new techniques, and to learn from them,” Naslund said.

Ally Whiteis, Odum undergraduate, paddles a canoe on a wolffia-covered pond.
Ally Whiteis, Odum undergraduate, paddling a field canoe.
Olivia Allen, Odum undergraduate, sitting behind Laura Naslund in a field canoe and recording data.
Olivia Allen, Odum undergraduate, recording data.

Naslund’s research is funded by the Network for Engineering With Nature, a collaboration between UGA and the US Army Corps of Engineers, along with a grant from the Odum School of Ecology and a 2022 Spencer Grant from the River Basin Center. The Spencer Grants are annual awards given to graduate students studying freshwater management and conservation. The grant is named for the late John Kyle Spencer, an Odum graduate student who was passionate about freshwater research. Research like Naslund’s is a reflection of this passion for freshwater science and cooperation among environmental researchers.

Photos and story by Olivia Allen

Precision Conservation of Imperiled Species

A tiny, rainbow-finned fish lives in the swiftly flowing waters of Georgia’s Etowah River. Known as the Etowah darter (Etheostoma etowahae), it exists only in the Etowah River Basin, mainly inhabiting the mountain streams of North Georgia.

The Etowah darter is only one example of the diverse array of freshwater fish, amphibians, crawfish and mussels that live in Georgia, including many endemic, imperiled species. However, the state is also a bustling transportation hub, with 1,253 miles of interstate highway and the busiest airport in the world.

Many of these species are highly sensitive to the threats associated with development.

In a recent project that brought together the University of Georgia’s River Basin Center and Institute for Resilient Infrastructure Systems, the Georgia Department of Transportation, the Georgia Department of Natural Resources and the U.S. Fish and Wildlife Service, researchers pinpointed ways to facilitate important construction projects around the state while tailoring conservation practices to each imperiled species’ needs.

Read the full article here.

Climate and Water Research Slam

Save the date: Climate and Water Research SlamThursday, May 12 1:00-5:00

The River Basin Center, the Georgia Initiative for Climate and Society, and the Office of Sustainability have joined forces for a climate and water “research slam” — a series of five-minute lightning talks by faculty and students on climate OR water (or both) followed by a social.

We have an awesome lineup of 24 5-minute lightning talks from a diverse group of speakers from across the UGA campus. Join us to hear about the wide range of water and climate work at UGA, to network with colleagues, and to celebrate the end of the semester. After the talks we’ll have a social with beverages and heavy snacks. Please join us!

Location: Innovation Hub, 210 Spring Street 

Schedule of Events:

  1:00 – 2:40  Session 1

  3:00 – 4:20  Session 2

  4:20 – 5:00  Social with beverages and snacks

Registration is free! But to help us plan for enough food and beverages, we ask you to please fill out this registration form by Monday May 9.

To see the full lineup, check out the draft detailed schedule (subject to correction for the next couple of days).

Third Wednesday Game Night with Dr. Karen Bareford

Last week Dr. Karen Bareford, the National Sea Grant and Water Resources Lead, delivered a Third Wednesday talk on the water resource efforts of the Sea Grant Network and its key partners, as well as the publicly available National Water Model. Afterwards, she presented the new Watershed Game: Coast Model, an engagement tool allowing players to take on the roles of policy and decisionmakers and collaborate in the management of water resources. Thank you to Dr. Bareford for speaking and showing this community-engaging activity!

The Role of Freshwater Crabs in Neotropical Streams

Freshwater crabs play an important role in the breakdown of nutrients from natural materials that fall into streams, but few studies have looked into exactly how their relationships with other detritivores and the leaf litter itself impacts ecosystems.  

River Basin Center graduate student Carol Yang shed light on these relationships in neotropical streams in two recently published papers.

In a paper published in Freshwater BiologyYang did an in-stream experiment in Monteverde, Costa Rica to examine the leaf litter in enclosures that contained crabs as compared to enclosures without crabs. One dynamic that Yang and colleagues hoped to learn more about was the relationship between crabs and other detritivores—which contribute to leaf breakdown, but that crabs frequently prey upon. 

Throughout the study, Yang and collaborators regularly sampled the leaf litter. They found that enclosures with crabs had faster rates of breakdown than those without, indicating that their manipulation and consumption of leaves had a larger impact than their consumption of other detritivores and shredders. 

In a follow up study published in Nauplius, Yang used a laboratory setting to gain a more in-depth understanding of the crab behaviors that most impacted leaf litter. The crabs were collected from Monteverde, Costa Rica, and transported to aquariums along with unfiltered stream water and leaves from a common subcanopy tree. 

Yang and colleagues found that the leaf mass was significantly higher in tanks with crabs than those without. They also used visual observations and recordings to watch as the crabs used their claws to grasp and shred the leaves, which aided in ingestion. At the end of the experiment, they observed that leaves in tanks with crabs were broken up into multiple pieces, whereas leaves in tanks without them remained whole.    

These studies suggest that crabs play an important role in helping to process the detritus that accumulates in neotropical streams, especially given their abundance in tropical streams.