Invasive Plant Abundance and Spatial Distribution in an Urban Ravine: Vegetation Trends and Management Implications in G. Ross Lord Park, Toronto

Abstract

Urban ravines in Toronto support urban biodiversity and provide essential ecological and recreational services, but are under ongoing threat from non-native invasive plants (NNIPs). This study provides a localized assessment of invasive species abundance and spatial patterns within a 13.8-ha section of G. Ross Lord Park, where Sanofi conducts ongoing stewardship initiatives. Using 30 Vegetation Sampling Protocol (VSP) plots and a 25 × 25 m presence grid, invasive species were identified, ranked using SER Ontario categories, and analyzed with conditional means, Importance Value Index (IVI), Moran’s I, and Getis-Ord Gi* hotspot mapping. Eight top-priority (Category 1) species were identified as the highest management concern in the woodland areas of the study area. Common buckthorn (Rhamnus cathartica) was the most widespread and abundant invasive, with significant hotspots of Garlic mustard (Alliaria petiolata), Norway maple (Acer platanoides), and Reed canary grass (Phalaris arundinacea). Other priority invasives included European euonymus (Euonymus europaeus), Dog-strangling vine (Cynanchum rossicum) and non-native honeysuckles; Tatarian honeysuckle (Lonicara tatarica) and Morrow’s honeysuckle (Lonicera morrowii). Findings from this study provide site-specific guidance for invasive plant management and support ongoing stewardship efforts towards ecological restoration within the park