Restoration of Native Plant Communities after Road Decommissioning in the Rocky Mountains: Effect of Seed-Mix Composition on Vegetative Establishment

Road decommissioning is increasingly recognized as a critical first step in the restoration of terrestrial and aquatic habitats. However, crucial gaps in knowledge exist about the efficacy and ecological effects of road-removal practices. One particularly important issue is the effectiveness of post-road-removal revegetation practices. This study evaluated (1) the short-term effects of road decommissioning on plant community composition, (2) the effects of seed-mix origin, species diversity, and seeding density on vegetative establishment, and (3) the impact of overstory canopy cover and coarse woody debris (CWD) on revegetation success on recently decommissioned roads. One year after decommissioning, total vegetative cover (on the former roadbed) declined by 60%, with non-native plants showing the greatest magnitude of response (circa 90% decline). Although the use of non-native seed is often justified by the need for rapid vegetative establishment on disturbed sites, we did not find significant differences in percent cover of total vegetation between plots seeded with native versus non-native species. As expected, cover of native species was significantly higher in plots seeded with natives compared to those seeded with non-natives (12.3 vs. 7.8%, respectively). Furthermore, in plots seeded with native species, 43% of total vegetative cover was due to cover of seeded species; in comparison, non-native seeded species accounted for only 18% of total vegetative cover in non-native plots. Cover of seeded species was not significantly impacted by overstory canopy cover or CWD. These findings suggest that native seed mixes may outperform non-native seed mixes in terms of vegetative establishment after disturbance associated with road removal.