Investigating Predictors of Plant Establishment During Roadside Restoration

Ecological restoration on roadsides confers several ecological benefits, but also poses significant challenges. Native plants used in restoration efforts must survive compacted soil, harsh microclimates, prolific invasive species, and pollution from road salts and vehicle emissions. Criteria for both site and species selection need to be developed to assist practitioners in restoring roadside environments. We transplanted seedlings of 9 grassland plant species into plots within 8 highway interchanges surrounding Ann Arbor, Michigan, United States. To see if they might predict plant performance in roadside restoration, we assessed 2 indices: the coefficient of conservatism (CC) as an index of affinity to undisturbed habitat; and the number of U.S. counties in which each species occurs as an index of distribution. We measured seedling survival, height, and biomass during the first growing season, and survival 1 year after transplant. We also measured soil characteristics, air temperature, and humidity at each interchange. We found that soil characteristics largely determined plant survival. Plants were more likely to survive in sandier soils than in soils rich in silt or clay that had high bulk density, high pH, and high conductivity. Although plant survival varied among species and interchanges, neither CC nor county-level distribution was a useful predictor of survival. Our results illustrate the importance of matching plant species with local soil characteristics when choosing restoration sites, and offer guidance to transportation officials considering roadside restoration with native plants, and practitioners working to restore any heavily disturbed site.