Managers of forest fragments in cities are faced with a uniquely urban set of challenges. Small patch sizes, a constant flow of new species introduced from around the globe, altered local climates, and atmospheric deposition of pollutants combine with a wild array of current and former land uses to structure today’s plant communities. What will be the future successional trajectories of these forests? How can management direct these trajectories to maximize forest health and desired environmental benefits? This presentation discusses new results of a long-term study of the effects of ecological interventions in urban forests where invasive woody plant species have been the target of restoration management.
Community structure and composition of multiple forest strata were sampled in 60 long-term plots located in two site types in New York City Park woodlands: 1. Forest patches invaded by woody climbing species porcelain berry (Ampelopsis brevipedunculata), oriental bittersweet (Celastrus orbiculatus), and/or multiflora rose (Rosa multiflora) for a minimum of 20 years; and 2. Invaded patches that have been subjected to restoration treatment within that 20 year period. Sites were first sampled in 2009-2010, and were re-sampled in 2015-2016.
Patches dominated by invasive woody plant species since ca. 1990 exhibited relatively little change in composition and structure between samplings, despite multiple disturbance events affecting these sites due to major storms (e.g. Sandy and Irene). This contrasts with an increase in abundance and diversity of native species observed in sites where these invasive species were removed and native species planted between samplings. Sites where restoration via invasive species removal and native plantings was initiated > 20 years prior continued to be dominated to a greater degree by native plant species and to have a significantly lesser abundance of target invasive species than unrestored sites. These findings indicate both that invasive species can form persistent communities resilient to small-scale ecological disturbances; and that the effects of directed restoration disturbance that alters site and species availability can result in desired long-term change in the trajectory of successional vegetation dynamics in urban forests.