Microstegium vimineum Invasion Changes Soil Chemistry and Microarthropod Communities in Cumberland Plateau Forests

Microstegium vimineum (Japanese Stiltgrass) is an exotic shade-tolerant C-4 grass that invades open and forested habitats throughout the southeastern United States. Studies suggest that invasive plants can alter ecosystem biogeochemistry by changing soil chemistry and biota. The objective of our study was to determine if M. vimineum invasion induces soil chemical changes that alter litter microarthropod communities in acidic, nutrient-poor upland forests of the Cumberland Plateau. In a greenhouse experiment comparing forest soil in tubs seeded with M. vimineum to those left unseeded over I year, we found that after 6 months, soil pH under M. vimineum was significantly higher than that in the unseeded tubs. We compared A-horizon chemistry, litter nutrients, and microarthropod community diversity in 3 forested sites with and without M. vimineum. We found higher pH, phosphorus (P), and base cations, and lower aluminum (Al) in soil under dense M. vimineum growth compared to soil under surrounding uninvaded understory. M. vimineum litter was more P-rich and had a higher abundance of mites than the surrounding forest floor over 3 sampling periods. However, microarthropod community evenness was lower in M. vimineum litter, indicating a decrease in diversity. These results suggest that a rapid rise in soil pH and P availability following M. vimineum colonization may reduce litter microarthropod community diversity by favoring mites.