Cities are increasingly focused on expanding tree canopy cover as a means to improve the urban environment by, for example, reducing heat island effects, promoting better air quality, and protecting local habitat. The majority of efforts to expand canopy cover focus on planting street trees or on planting native tree species and removing nonnatives in natural areas through reforestation. Yet many urban canopy assessments conducted at the city‐scale reveal co‐dominance by nonnative trees, fueling debates about the value of urban forests and native‐specific management targets. In contrast, assessments within cities at site or park scales find that some urban forest stands harbor predominantly native biodiversity. To resolve this apparent dichotomy in findings, about the extent to which urban forests are native dominated, between the city‐scale canopy and site‐level assessments, we measure forest structure and composition in 1,124 plots across 53 parks in New York City's 2,497 ha of natural area forest. That is, we assess urban forests at the city‐scale and deliberately omit sampling trees existing outside of forest stands but which are enumerated in citywide canopy assessments. We find that on average forest stand canopy is comprised of 82% native species in New York City forests, suggesting that conclusions that the urban canopy is co‐dominated by nonnatives likely results from predominantly sampling street trees in prior city‐scale assessments. However, native tree species’ proportion declines to 75% and 53% in the midstory and understory, respectively, suggesting potential threats to the future native dominance of urban forest canopies. Furthermore, we find that out of 57 unique forest types in New York City, the majority of stands (81%) are a native type. We find that stand structure in urban forest stands is more similar to rural forests in New York State than to stand structure reported for prior assessments of the urban canopy at the city scale. Our results suggest the need to measure urban forest stands apart from the entire urban canopy. Doing so will ensure that city‐scale assessments return data that align with conservation policy and management strategies that focus on maintaining and growing native urban forests rather than individual trees.

The context in which trees and forests grow in cities is highly variable and influences the provision of ecological, social, and economic benefits. Understanding the spatial extent, structure, and composition of forests is necessary to guide urban forest policy and management, yet current forest assessment methodologies vary widely in scale, sampling intensity, and focus. Current definitions of the urban forest include all trees growing in the urban environment, and have been translated to the design of urban forest assessments. However, such broad assessments may aggregate types of urban forest that differ significantly in usage and management needs. For example, street trees occur in highly developed environments, and are planted and cared for on an individual basis, whereas forested natural areas often occur in parkland, are managed at the stand level, and are primarily sustained by natural processes such as regeneration. We use multiple datasets for New York City to compare the outcomes from assessments of the entire urban forest, street trees, and forested natural areas. We find that non-stratified assessments of the entire urban forest are biased towards abundant canopy types in cities (e.g. street trees) and underestimate the condition of forested natural areas due to their uneven spatial arrangement. These natural areas account for one quarter of the city’s tree canopy, but represent the majority of trees both numerically and in terms of biomass. Non-stratified assessments of urban forest canopy should be modified to accurately represent the true composition of different urban forest types to inform effective policy and management.

Reforesting degraded urban landscapes is important due to the many benefits urban forests provide. Urban soils are highly variable, yet little is known about how this variability in urban soils influences tree seedling performance and survival. We conducted a greenhouse study to assess health, growth, and survival of four native tree species growing in native glacial till, coal ash, urban fill, and sandy clean fill soils collected from urban forest restoration sites in New York City. Using a multifactorial design, nine replicates of silver maple (Acer saccharinum), black birch (Betula lenta), red oak (Quercus rubra), and Canadian serviceberry (Amelanchier canadensis) were planted in four urban soil types and one greenhouse mix. We hypothesized that: 1) urban soil type would influence growth, health, and survivorship; 2) each tree species would respond differentially to each soil type; and 3) seedling stress and mortality would be higher for soils with more anthropogenic disturbance. After one growing season, we found that seedlings were less healthy and grew less in soils with a history of greater anthropogenic disturbance. Seedling mortality was low (< 3% overall) except for red oak seedlings in urban fill soil from one location. These results demonstrate that urban soil conditions can impact tree growth and health while supporting high survivorship. Species × soil type interaction for height growth and stress indicate that native tree species may not respond to urban soil conditions consistently. Consequently, matching tree species to soil type could help optimize establishment and growth of urban forest restoration projects.

Cities worldwide are engaging in large‐scale greening projects motivated by the wide range of documented ecological, economic, and social benefits of urban forests. Urban forested natural areas are a critical component of the total urban forest but are often overlooked and typically lack formal management frameworks. One approach to addressing this deficiency may be to borrow from traditional ecological management frameworks and practices (that is, silviculture). Although urban forested natural areas share similarities with rural forests, the impacts of urbanization on forest stand dynamics may require modification of these methods and in some cases development of novel silvicultural guidelines. We present an urban silviculture framework through which we synthesize emerging research and identify challenges and opportunities for advancing goal setting, assessments, and on‐the‐ground management strategies. Adapting silvicultural practices to cities can improve the long‐term sustainability of urban forests and establish management approaches that address future conditions in forests across the urban–rural continuum.

Not all urban greenspace is the same. Natural area forests can provision more benefits than designed landscapes, and healthy natural area forests can provide more benefits than degraded and invaded forests. Yet there is little information about the scale of natural areas in cities and their management systems. We used data sets on city parkland from across the United States and surveyed practitioners to understand urban natural area forest extent and management. We find that urban natural areas are a dominant greenspace landcover, accounting for 68% of total city parkland across 96 of the most populous cities in the United States in 2019. In the same cities over a five-year period (2014–2019), natural area parkland decreased by 4% (15,264 hectares). At municipal scales, most cities are managing forested natural areas to conserve native species. Across the 108 organizations and 92 cities that responded to our online survey, many different management interventions are being used to steer forest structure and composition. These activities and their outcomes are being tracked nearly 70% of the time by the managing organizations, suggesting a strong data basis for adaptive management. However, challenges exist: 94% of organizations cite invasive species and limited funding as primary challenges. Lack of data and low public awareness of the value of natural areas are also considered primary challenges by more than 70% of the organizations surveyed. As cities embark on efforts to expand and improve greenspace, protecting natural area parkland from development and addressing the challenges managers of these ecosystems face are two very important goals.