Vegetation composition and structure of woody plant communities along urban interstate corridors in Louisville, KY, U.S.A.

Roads—and the cities they serve—can have an effect disproportionate to their size on the ecosystems around them. The vegetative barriers along them, even when narrow, can offer significant value including improved aesthetics, noise reduction, and other ecosystem services. This study investigated the composition and structure of woody plants, with a focus on native vs invasive species, along three highways in Jefferson County, Kentucky. Traffic densities, land cover, and soil types were determined. Composition and size of all woody plants as well as plot characteristics (e.g., slope, sunlight intensity, distance to highway) were assessed in 100-m² plots. Landscape characteristics (distance from city center, land use) were determined with GIS. Nonmetric multidimensional scaling (NMDS) analysis was used to find similarities and differences across plots. Tree species richness was high (50 species) and native species predominated (94%). The most important factors influencing vegetative composition were distance to the city center and the presence of the exotic invasive shrub Lonicera maackii. Interestingly, the woody plant community along the most heavily traveled highway was composed almost entirely of native species, suggesting that naturally regenerating native forests can persist in such challenging environments.