Natalie Clay studies the health of forest ecosystems — not only by examining the trees, but by inspecting the organisms living below them. 

Clay is a new associate professor of entomology and plant pathology for the Arkansas Agricultural Experiment Station. Her research primarily focuses on how the availability of food and living space for leaf litter and soil arthropods impacts the forest ecosystem's function. 

Forest health is a broad concept that includes not only the trees, but also the forest's riparian areas — the land that borders a river or stream — and the soil, leaf litter and ground organisms, Clay said.

"Those trees don't exist without the soil and the leaf litter and what's going on in those systems," she said. 

Clay joined the experiment station, the research arm of the U of A System Division of Agriculture, in September. Along with her research efforts, she will teach classes through the Dale Bumpers College of Agricultural, Food and Life Sciences at the U of A. 

"My work is like play," Clay said. "I get to go outside and see cool things and make natural history observations, and one question always leads to another." 

"I hope to be able to help research what's going on, and hopefully help find solutions, or at least explanations, for issues that might be affecting Arkansas forests."

Establishing Research

Clay's first research project with the experiment station will explore how sodium availability in terrestrial ecosystems impacts the movement of resources, such as carbon, between the land that borders a body of freshwater and freshwater streams. 

She is collaborating with Michelle Evans-White, professor of biological sciences at the U of A, and Sally Entrekin, associate professor of aquatic entomology at Virginia Tech University.  

The increase of salt in freshwater ecosystems is an increasingly common global phenomenon due to the natural weathering of rocks, hurricanes moving salt further inland, increases in road salting, resource extraction and accidental spills, Clay said.

"There's a lot of different avenues by which salt is increasing in terrestrial systems, and that can get into freshwater systems," Clay said. "Our research looks at how that impacts ecosystem functions within both riparian forest and stream ecosystems." 

Freshwater ecologists and those studying terrestrial systems have different views on salt, Clay said. Salt is a stressor in freshwater ecosystems, but it acts as a catalyst in terrestrial systems, increasing the rates of decomposition and productivity of organisms. 

"The historical view for freshwater ecologists is to view salt as bad, and with good reason, because just a little bit of salt can quickly have some negative effects on the invertebrates that are in freshwater and what they do in those systems," Clay said. "But in terrestrial systems, where I'm primarily focused, salt, besides in agricultural systems, has been viewed as kind of a good thing."

Ken Korth, department chair of entomology and plant pathology, said he is excited to welcome Clay to the department. 

"Her experience in forest systems is an excellent addition to our ongoing research and teaching, and it fills a big gap in our collective expertise," Korth said. 

Forests cover some 19 million acres of Arkansas — more than half of the state, according to the Arkansas Department of Agriculture. 

"As our state population increases and urban growth encroaches into forested areas, issues of tree and forest health will only become more critical for Arkansans," he said. "Likewise, the economic importance of healthy forests in our state is substantial. This, coupled with emerging problems due to changing climate and emerging pests, make Natalie's research essential and even more impactful."

Maintaining a Salty Diet

Clay's prior research projects also examined the role of salt in terrestrial systems, specifically through the diets of organisms living in the soil. During her graduate studies, she explored two methods of how arthropods maintain sodium in their diets when they are farther from the coast.

The first part of the research showed the role urine has as a possible source of sodium for the organisms. 

 "We added synthetic urine to these systems to determine if this could serve as a source of sodium for leaf litter arthropods," Clay said. 

The addition of sodium increased litter and deadwood decomposition, detritivores and their predators — all important components of healthy forest ecosystems, Clay said. A detritivore is an organism that consumes dead organic matter. They are also known as decomposers. 

The second part of her research tested the hypothesis that omnivores — animals with diet flexibility — consume more animal tissue when salt is less available. 

She sampled ants in 20 forests on the East Coast of the United States. She collected ant species on the coastal parts of the forests, where there would be sodium-rich leaf litter, and over 100 kilometers, or about 62 miles, away on the same latitude inland, where sodium availability in leaf litter is scarce. She found that ants of the same species were more carnivorous when sodium was unavailable on the forest floor. 

"That kind of led to a general geography of omnivory a way to potentially predict when omnivores might be more carnivorous," Clay said. 

Omnivores can have major effects on ecosystems, such as forests, acting as both herbivores and predators, Clay said. So understanding factors that impact their behavior can help better inform the understanding, conservation and management of these ecosystems.

Clay received her bachelor's degrees in biology and art from Colby College in Waterville, Maine, in 2008 and her doctorate in zoology-ecology and evolution from the University of Oklahoma at Norman in 2013. She served as an assistant professor in the Louisiana Tech University School of Biological Sciences from 2015 to 2021 and as an associate professor from 2021 to 2023.  

To learn more about Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website: https://aaes.uada.edu/. Follow us on Twitter at @ArkAgResearch. To learn more about the Division of Agriculture, visit https://uada.edu/. Follow us on Twitter at @AgInArk.

About the Division of Agriculture: The University of Arkansas System Division of Agriculture's mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices.  Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation's historic land grant education system. The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on five system campuses. The University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.