FAYETTEVILLE — Natalie Clay studies the health of forest ecosystems — not only by studying the trees, but also by inspecting the organisms that live beneath them.
Clay is a new associate professor of entomology and plant pathology at the Arkansas Agricultural Experiment Station. Her research focuses primarily on how the availability of food and living space for leaf litter and soil arthropods affects forest ecosystem function.
Forest health is a broad concept that includes not only the trees, but also the riparian areas of the forest — the land that borders a river or stream — and the soil, leaf litter and terrestrial organisms, Clay said.
“These trees don’t exist without the soil and the leaves and what’s going on in those systems,” she said.
Clay joined the Experiment Station, the research arm of the University of Arkansas Department of Agriculture, in September. Along with her research efforts, she will teach classes in the Dale Bumpers College of Agriculture, Food and Life Sciences at the University of Arkansas.
“My work is like a game,” Clay said. “I get to go out and see great things and make natural history observations, and one question always leads to another.”
“I hope I can help research what’s going on and help find solutions, or at least explanations, for problems that may be affecting the forests of Arkansas.”
Clay’s first research project with the experiment station will examine how the presence of sodium in terrestrial ecosystems affects the movement of resources, such as carbon, between land that borders a freshwater body and freshwater streams.
She collaborated with Michelle Evans-White, a professor of biological sciences at the University of Arkansas, and Sally Entrekin, an associate professor of aquatic entomology at Virginia Tech.
The increase in salt in freshwater ecosystems is an increasingly common global phenomenon due to natural rock weathering, hurricanes carrying salt further inland, increases in road salting, resource extraction and accidental spills, Clay said.
“There are many different pathways by which salt increases in terrestrial systems and that can end up in freshwater systems,” Clay said. “Our research looks at how this affects ecosystem functions in both riparian forest and stream ecosystems.”
Freshwater ecologists and those who study 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 rate of decomposition and the productivity of organisms.
“The historical perspective for freshwater ecologists has been to view salt as harmful, and for 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’re doing in those systems,” said Clay. “But in the land systems where I’m primarily focused, salt, except in agricultural systems, is seen as a good thing.”
Ken Court, head of the Department of Entomology and Plant Pathology, said he is excited to welcome Clay to the department.
“Her expertise in forest systems is an excellent addition to our ongoing research and teaching and fills a major gap in our collective expertise,” said Court.
Forests cover about 19 million acres in Arkansas — more than half of the state, according to the Arkansas Department of Agriculture.
“As our state’s population increases and urban growth encroaches on forested areas, tree and forest health issues will become increasingly critical for Arkansas residents,” he said. “Likewise, the economic importance of healthy forests in our state is significant.” This, combined with emerging issues due to a changing climate and emerging pests, makes Natalie’s research important and even more impactful.”
Maintaining a salty diet
Clay’s previous research projects also explored the role of salt in Earth’s systems, specifically through the diet of soil-dwelling organisms. During her graduate studies, she investigated two methods of how arthropods maintain sodium in their diet when they are farther from shore.
The first part of the study showed the role of urine 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 arthropods from leaf litter,” Clay said.
Adding sodium increases the decomposition of litter and dead wood, detritus 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 a flexible diet — consume more animal tissue when salt is less available.
She sampled ants in 20 forests on the East Coast of the United States. It collects ant species in the coastal parts of forests, where sodium-rich leaf litter will be present, and over 100 kilometers, or about 62 miles, at the same latitude inland, where the availability of sodium in leaf litter is scarce. She found that ants of the same species were more predatory when sodium was unavailable on the forest floor.
“This has somewhat led to a general geography of omnivores, a way of potentially predicting when omnivores might be more carnivorous,” Clay said.
Omnivores can have major effects on ecosystems, such as forests, by acting as both herbivores and predators, Clay said. So understanding the factors that influence their behavior can help better inform the understanding, conservation and management of these ecosystems.
Clay received her BA in Biology and Arts from Colby College in Waterville, Maine in 2008 and her PhD in Zoology – Ecology and Evolution from the University of Oklahoma in Norman in 2013. She has worked as an assistant professor at Louisiana Tech University School of Biological Sciences from 2015 to 2021 and as Associate Professor from 2021 to 2023.
Brittany Mann is from the U of A System Division of Agriculture.