Urban forest fragments under climbing invasive species: Plant communities and outcomes of long-term management
Forested patches in cities are subject to multiple anthropogenic stressors, including high frequency of exotic plant species introductions. Many species of woody climbing plants have been introduced to serve as visual screens, wall coverings, and slope stabilizers. These species are also well adapted to thrive on the edges of forest fragments. High edge-to-interior ratios and an abundance of roads, trails and other edge-creating land uses give cause for concern about increasing vine abundance among managers of these small but disproportionately important habitats. In New York City, Department of Parks and Recreation managers began treatment of vinelands dominated by exotic invasive species in the late 1980s with manual, mechanical and chemical removal followed by planting with native trees. 15-20 years after initial treatment, we revisited restored sites and sampled ground, understory and canopy species composition and abundance. We also sampled sites that had been reported to contain the same invasive species (Ampelopsis brevipedunculata and Celastrus orbiculatus, often co-occurring with climbing shrub Rosa multiflora) but which had not been treated in the same period. In 2014, we sampled more recently disturbed sites in canopy gaps caused by large storms using the same methods.
We found that these restoration treatments resulted in persistent change in species composition and abundance compared to unrestored sites, indicating divergent trajectories in vegetation dynamics between site treatments. In all site types, we found novel assemblages of native, non-native and invasive species. We found that plant community structure and composition of invaded and restored vinelands varied, with implications for future management to contain these invasive vegetation elements.