Species composition and stand structure in the urban forest: Comparing remnant forest patches and secondary growth in Toronto's ravine system

Abstract

Forested patches within urban areas provide essential ecosystem services and play a critical role in preserving urban biodiversity. Based on their origin, forested patches can be classified as remnant forests, areas that have not been cleared and have remained forested throughout urbanization, or secondary forests, established on land previously cleared for alternative uses. This capstone project compares species composition and stand structure between remnant forest patches and secondary growth within the G. Ross Lord Park, part of Toronto’s extensive ravine network. Using the Vegetation Sampling Protocol (VSP), 54 fixed-area plots were surveyed to assess native and nonnative plant abundance, species richness, and floristic quality across canopy and understory strata. Historical forest cover mapping from 1954 was integrated with field data to classify monitoring plots according to their proximity to remnant forest patches. This allowed for the examination of ecological patterns using Kruskal–Wallis tests, Spearman’s correlation tests, and Generalized Linear Models. The results demonstrated that remnant forest patches exhibited higher native species richness and stronger floristic quality, particularly within the tree layer. Remnant forest patches also contained fewer nonnative tree species compared to secondary forests. These findings indicate that remnant forests serve as important refuges for native vegetation within urban forests and highlight the long-lasting effects of historical land use on secondary forests. This project provides evidence-based management recommendations to guide conservation and restoration efforts in the G. Ross Lord Park. It emphasizes the need to protect remnant forest patches, prioritize invasive species removal at remnant edges, and support assisted regeneration in secondary forests to strengthen ecological resilience across the ravine system.