Citizen science and land use data provide insight into the invasive riparian plant composition of the Hudson River Valley watershed

Invasive plants in the riparian zone can negatively affect the characteristics and quality of a watershed. To support the development of a watershed management plan and foster public appreciation of the value of the riparian zone, Mohonk Preserve established a volunteer monitoring program surveying sites for invasive species. Between 2017 and 2019, citizen scientists repeatedly surveyed 20 sites in the Hudson River Valley in New York for 10 invasive plant species: purple loosestrife (Lythrum salicaria L.), common reed [Phragmites australis (Cav.) Trin. ex Steud], multiflora rose (Rosa multiflora Thunb.), garlic mustard [Alliaria petiolata (M. Bieb.) Cavara & Grande], dame's rocket (Hesperis matronalis L.), Japanese knotweed (Polygonum cuspidatum Siebold & Zucc.), wineberry (Rubus phoenicolasius Maxim.), barberry (Berberis spp.), Japanese stiltgrass [Microstegium vimineum (Trin.) A. Camus], and Asiatic bittersweet (oriental bittersweet, Celastrus orbiculatus Thunb.). We found that the number of target species detected was higher on sites closer to paved roads and with increasing drainage area size, while lower with higher percentages of forested land in the basin. Our analysis results highlight variation in the presence of target invasive species across the Hudson River Valley region, highlighting sites and areas to monitor for future introductions and take action to prevent species' invasions. Our results highlight differences in the most relevant abiotic factors for hydrophytes and non-hydrophyte species, underscoring the importance of considering species' life-history traits before the development of management plans for invasive plant species in the riparian zone. Our case study of community-collected data in the Hudson River Valley region using a relatively simple monitoring protocol can provide a road map for other regions fostering volunteer engagement with invasive plants.