Impacts of Invasive Asian Jumping Worms on Soil Properties in Turfgrass Systems and their effects on Plant Nutrient Acquisition and Physiological Responses in Greenhouse Experiments

Abstract

This thesis examines the ecological impact of invasive Asian jumping worms (Amynthas spp.) in turfgrass systems and controlled greenhouse conditions. In the field, we evaluated jumping worm presence using environmental DNA (eDNA) and assessed associated changes in microarthropod abundance, microbial enzyme activity, soil chemical and physical properties, and turf condition. The study was conducted at four residential sites in southwest Virginia, each with garden bed infestations and adjacent turfgrass lawns. Sampling occurred in May and September 2024. At each site, four fixed transects were established, beginning one meter inside the garden bed and extending ten meters into the lawn. Soil and turf data were collected from one-square-meter quadrats placed at three locations along each transect: within the garden ("Bed"), at the turf edge ("Turf Near"), and six meters further into the lawn ("Turf Far"), resulting in 48 quadrats across all sites. Jumping worms were most frequently detected in turf quadrats adjacent to garden beds, confirming our hypothesis of turf as a zone of invasion. Microarthropod communities, particularly Collembola, exhibited a pronounced early-season increase in jumping worm-invaded areas followed by a late-season collapse. This shift coincided with changes in microbial enzyme activity: chitin-degrading NAG increased after arthropod decline, while nitrogen-releasing LAP decreased most in jumping worm-infested garden soils. Soil structure was primarily affected in garden beds, specifically, large aggregates (>2 mm) increased in jumping worm-infested beds, while mid-sized aggregates (0.25–2 mm) decreased. Soil nutrients remained largely stable, though phosphorus and organic matter showed seasonally dependent shifts linked to jumping worm presence. Firth logistic regression identified organic matter as a significant predictor of jumping worm detection, though this relationship reversed over time, likely reflecting resource exhaustion or outward migration into turf. Turfgrass condition appeared visually unaffected. Collectively, these findings indicate that while aboveground vegetation may appear intact, significant biological restructuring is underway below ground. In a complementary greenhouse experiment, we tested whether invasive jumping worms alter soil conditions in ways that influence bean physiology. We collected jumping worm-free topsoil from a local farm and divided it evenly into two 151 liter bins. Both bins received identical amendments of coconut coir and compost. One bin was inoculated with 80 live jumping worms; the other remained jumping worm-free. These bins were kept moist and left undisturbed for 12 weeks to allow soil conditioning. No fertilizers were added. After this period, we used each soil type to fill ten 3.8-liter nursery pots (n = 20 total), with no jumping worms transferred into the pots. Provider bush beans (Phaseolus vulgaris) were sown directly into each pot, and plants were grown under uniform greenhouse conditions. We repeated this process in a second planting round using the same bins after six months of soil conditioning to test for cumulative jumping worm effects. Across both rounds, we measured developmental stage (BBCH), chlorophyll content (SPAD), stomatal conductance, biomass, tissue nutrients, and soil chemistry. While planting round was the main driver of BBCH and SPAD, jumping worm-conditioned soils in Round 2 consistently showed slightly elevated values, suggesting compounding effects over time. Stomatal conductance declined sharply in jumping worm-free pots between rounds but remained stable in jumping worm-conditioned soils, possibly reflecting moisture or nutrient buffering. Notably, jumping worm-treated plants produced greater fresh biomass but lower nitrogen content, resulting in elevated C:N ratios. This pattern may reflect a mild dilution effect, where increased growth and water content are associated with slightly lower nutrient concentrations in vegetative tissues. However, carbon and nitrogen concentrations in bean pods remained consistent across treatments, suggesting that plants prioritized allocation of limited resources to reproductive tissues despite reduced shoot nitrogen content. Soil chemistry shifts, especially in calcium, magnesium, potassium, and organic matter, were consistent with accelerated nutrient turnover in jumping worm-conditioned soils.