Abstract

As cities expand tree planting to promote benefits to residents, they require strong baseline knowledge on urban forest conditions. Historically, public tree databases have been used to assess urban forest composition, structure and diversity, yet recent studies suggest trees on private land can differ in important ways from public trees, influencing urban forest benefits and resilience. We used a city-wide network of plots spanning multiple urban gradients to assess six private and public land use types (residential, public right-of-way, institutional, commercial, parks (excluding woodlands), vacant lots) and asked how urban forest composition and structure differed. Our study presents one of the most complete urban forest inventories and analyses for a large North American city, capturing the diversity, structure, and composition of trees across multiple land use types. We found strong differences in tree abundance, size, and diversity among land use types, reflecting contrasting management practices and planting histories. Hedges emerged as a dominant feature across all land use types – but most prominently on residential land – contributing a substantial proportion of trees, particularly Thuja occidentalis. Residential land and public rights-of-way supported the greatest tree abundance and species richness, while parks contained larger trees and greater basal area. Despite overlapping species, dominance patterns differed across land use types. Our work emphasizes that public green spaces are insufficient to represent citywide urban forest composition and structure, and private green spaces must be considered to better understand the urban forest. It also reveals that overall, the urban forest is much more diverse than previously thought.