Daniel Smith: The tiny cities protecting your soil

The following story was written in December 2023 by Liam J. May in ENGL 4824: Science Writing as part of a collaboration between the English department and the Center for Communicating Science.

Microorganisms are so tiny that we often take them for granted. They can't stand up for themselves. I mean, they don’t even have legs! It’s easy to forget the important role they play in the world around us. 

    Researcher Daniel Smith aims to change this perception.

    Smith kicked off his collegiate years at the University of Maryland in 2012 and was a postdoctoral researcher in Virginia Tech’s School of Plant and Environmental Sciences at the time of our interview.  Environmental science wasn’t always the plan, he says; rather, he thought he wanted to become a software engineer. But Smith soon discovered his passion for “applying what he had learned to the world around him” and discovered undergraduate research programs, through which he studied the effects of soil on plant health and the characterizations of wetland environments. Soon equipped with a degree in civil and environmental engineering, he continued to follow his newfound passion for research and began a graduate program at Virginia Tech. 

    Working with Dr. Theresa Thompson in biological systems engineering, Smith’s research focused on one question: How do the attributes of plants, specifically the microorganisms interacting with plant roots, impact streambank erosion? 

    “Roots protect soil physically by holding it together,” Smith explains, “but the soil is also alive and thriving with microorganisms.” Understanding how soil, roots, and microorganisms interact to influence streambank erosion can give us insight into how landscapes change over time, he says. He knew that it wasn’t just roots that could prevent erosion, but he needed to prove it.

    How might microorganisms be able to prevent erosion? Soil is full of microorganisms, plant life, and organic material, Smith explains, and their interactions are critical:  “Microorganisms in soil, usually, 99.9 percent of the time, are not by themselves.” They group together and create structures called biofilms, formed and “glued” together with the organic material they consume and create. 

    “Think of these structures as tiny cities where the microorganisms are the people, the biofilm is the buildings, and the glue is what holds the city together,” Smith says. These structures are how microorganisms “stick” the soil together.

    Smith didn’t know how strong this “glue” could be and needed a controlled environment to test his hypotheses. What better a controlled environment than one of the biological and systems engineering department’s giant water flumes?

    Eight meters long, taking up an entire room, the flume allowed Smith to test different soil samples under different conditions that mimicked the natural conditions occurring in streams and rivers.  Access holes in the flume provided the opportunity to insert samples for testing against these conditions.

    Using the flume proved to be one of the most challenging parts of Smith’s research process. Unexpected variability in the testing environment forced Smith to continuously repeat the experiment.

     “Problems can easily propagate,” he states, “especially when they go unnoticed.”

    In one of his primary experiments, Smith created four treatments to test against the different stream and river conditions: Soil with living vegetation, soil with fake root fibers, soil with organic materials, and soil with both fake root fibers and organic materials. Fake root fibers  isolated the structural benefits of roots, while organic materials allowed him to assess the structural benefits of microorganisms, as it supplied them with the materials necessary to form their “tiny cities.” He placed each sample against the edge of the flume, observed its erosion, and swapped it out with another.

    Then it was time for Smith’s favorite part of the research process: analysis of his results. Not only did the flume tests show that microorganisms could prevent erosion; they also showed that microorganisms provided protection levels similar to that seen with the fake roots he tested. 

    “I had a feeling that microorganisms would have an effect on erosion, but I didn’t realize how relevant it would be,” says Smith. And when combined, fake roots and microorganisms could produce protection nearly identical to the erosion protection of living vegetation.

     "These results showcased the major role of these organisms in erosion," says Smith.

    The research has provided us with a better understanding of erosion and how to predict it, Smith says, an important benefit for farmers, city planners, engineers, and landowners. Now that we understand the role of microorganisms, he explains, we can begin to study how environmental factors like temperature and water content can impact them in ways that will change erosion rates. This newfound understanding will provide us with additional insight into our impact on different ecosystems and how we can preserve them. 

    Smith’s postdoctoral research expanded on these principles, looking at organic materials more generally and how we can use them to improve soil structural integrity, reduce costs, and produce sustainability in construction projects, big or small.

    Ultimately, Smith’s research highlights the “biological and chemical processes [in the tiny cities around us] and their underestimated importance.” At the end of the day, it's good to have someone standing up for the little guys with no legs.