A peek at life under a wheat field: Reflections from an LTER Fellow

MSU graduate researcher, Allison Zahorec, is a PhD student in Dr. Doug Landis’s lab in the Department of Entomology at Michigan State University.

Allison Zahorec holding a core of soil taken out of a wheat field at the LTER. Photo by Kurt Stepnitz.

When one envisions a typical midwestern farm, ‘biodiversity’ is hardly the first thing that comes to mind. Compared to more natural landscapes, agricultural lands can seem like ecological dead zones. Yet even the most intensively managed corn monocultures are teeming with life belowground. A few teaspoons of soil can contain over a billion individual organisms (largely microbes), and the diversity of soil-dwelling organisms is just as impressive.

Within this vast array of soil-dwellers you can find the focus of my graduate research: microarthropods. The term ‘microarthropod’ is an umbrella term for soil-dwelling arthropods between 2 and 0.1mm in size. They are often the dominant arthropod group in agricultural soils, where their numbers can reach the tens of thousands per square meter of soil. Two types of microarthropods, springtails and oribatid mites, tend to be the most abundant. Most species of springtails and oribatid mites feed on microbes, which can have a range of impacts on microbial growth, community dynamics, and activity. Because soil microbes are critical for soil organic matter (SOM) accrual and stabilization, this interaction could have potentially significant impacts on the ability of soils to retain carbon and is what drew me to microarthropod research.

By researching the role of microarthropods on microbial dynamics and the resulting effects on SOM, I hope to improve our understanding of how soil fauna may be influencing soil carbon cycling, particularly in soils used for crop production. Understanding the dynamics between microarthropods, microbes, and soil carbon is especially crucial in these soils. Over a third of all land area in the United States is dedicated to crop production, it is in these lands that are so heavily altered by humans where there exists the greatest potential for making positive management changes to support soil biotic communities and promote soil carbon accrual.

PVC quadrat used for collecting plant litter and the microarthropods living within. Photo by Kurt Stepnitz.

In order to study microarthropod-microbe relationships in soils used for crop production, I first needed to know what microarthropods are living in these soils. To address this, I have spent the last two field seasons surveying microarthropods living in plant litter and the surface soils at KBS. The majority of my research so far has taken place at the GLBRC’s (Great Lakes Bioenergy Research Center) Biofuel Cropping System Experiment, where I have conducted microarthropod surveys in bioenergy systems ranging from conventionally managed energy sorghum (similar to corn) monocultures to relatively untouched restored prairies. Here, I’ve found evidence that microarthropods tend to prefer perennial bioenergy cropping systems that experience minimal disturbance from management. But are these findings reflective of what is going on belowground in more traditional agricultural systems?

Through the LTER Summer Fellowship program, I had the opportunity to explore my questions about microarthropod communities in agricultural lands at the LTER Main Cropping System Experiment over the summer of 2019. One question I sought to address was how different types of management of the same crop can impact microarthropod communities. For this work, I surveyed microarthropods in corn-soy-wheat rotations undergoing a range of management systems, from conventional to organic. While I still need to do more surveys to identify overall patterns across time, I found that microarthropod densities tended to be greatest in the treatments experiencing less disturbance. Interestingly, the pattern of microarthropod abundance in these treatments roughly track the pattern of surface soil carbon as found by another LTER researcher.

With the recent addition of prairie strips to the LTER, I’ve also had the unique opportunity to collect baseline data surveying microarthropods collected from the surface soils to a meter below the soil surface. This survey will be repeated in after the prairie strips have had time to mature in order to see how microarthropod community structure within prairie strips change overtime. Prairie strips provide a range of ecosystem services to agricultural landscapes, such as increasing biodiversity by providing habitat to beneficial species (pollinators, predators of crop pests, etc.). Tracking the change in microarthropod communities in prairie strips overtime will shed light on the potential for prairie strips to benefit soil fauna as well.I am incredibly thankful for the opportunity to get involved in LTER research during my graduate program. In addition to being able to conduct research in a new system, being an LTER fellow allowed me to meet and network with LTER researchers from across a broad range of disciplines. It has been very enriching to receive feedback on my work from others as well as be exposed to the breadth of research being conducted at the LTER. I’m looking forward to continuing my efforts at the LTER to uncover what is going on down beneath the soil surface.