Grazing as a Control for the Spread of Mile-a-Minute (Persicaria perfoliata) and the Restoration of Biodiversity in Plant Communities in a Lower New York State Parkland

The invasive annual vine, mile-a-minute (Persicaria perfoliata), has disrupted native plant communities throughout the mid-Atlantic United States and is rapidly spreading. This study investigated the efficacy of using sheep to control the spread of mile-a-minute at Ward Pound Ridge Reservation in Westchester County, NY. Animals were rotated, at a high stocking density (equivalent to ca. 9 tons of grazer biomass ha^–1) through a system of 200 m² enclosures at high frequency (2–3 day enclosure^–1). An ungrazed reference area was delineated adjacent to each of the grazed enclosures. Cover class analysis was performed, species richness was determined and the inflorescence (presence of flower clusters) of individual mile-a-minute plants was monitored in all enclosures and corresponding reference areas prior to the commencement of grazing and following the final grazing rotation. Prior to sheep deployment, mile-a-minute cover was 3.8 times greater in grazed enclosures than in ungrazed areas. Following grazing, mile-a-minute cover in grazed enclosures (6.69% ± 5.9%) was 3.6 times lower in the ungrazed areas (20.6 ± 21.2%). Furthermore, mile-a-minute inflorescence was significantly lower (X2 = 98.019, n = 4; p < 0.001) in grazed enclosures than in ungrazed areas after completion of the grazing phase of the study. Following the final grazing rotation, an increase in vascular plant species richness (+ 23.08%), was observed in response to grazing whereas a decrease in species richness (–6.94%) was observed in ungrazed areas.