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.

As urbanization increases worldwide, investments in nature‐based solutions that aim to mitigate urban stressors and counter the impacts of global climate change are also on the rise. Tree planting on degraded urban lands—or afforestation—is one form of nature‐based solution that has been increasingly implemented in cities around the world. The benefits of afforestation are, however, contingent on the capacity of soils to support the growth of planted trees, which poses a challenge in some urban settings where unfavorable soil conditions limit tree performance. Soil‐focused site treatments could help urban areas overcome impediments to afforestation, yet few studies have examined the long‐term (>5 yr) effects of site treatments on soils and other management objectives. We analyzed the impacts of compost amendments, interplanting with shrubs, and tree species composition (six species vs. two species) on soil conditions and associated tree growth in 54 experimental afforestation plots in New York City, USA. We compared baseline soil conditions to conditions after 6 yr and examined changes in the treatment effects from 1 to 6 yr. Site treatments and tree planting increased soil microbial biomass, water holding capacity, and total carbon and nitrogen, and reduced soil pH and bulk density relative to baseline conditions. These changes were most pronounced in compost‐amended plots, and the effects of the shrub and species composition treatments were minimal. In fact, compost was key to sustaining long‐term changes in soil carbon stocks, which increased by 17% in compost‐amended plots but declined in unamended plots. Plots amended with compost also had 59% more nitrogen than unamended plots, which was associated with a 20% increase in the basal area of planted trees. Improvements in soil conditions after 6 yr departed from the initial trends observed after 1 yr, highlighting the importance of longer‐term studies to quantify restoration success. Altogether, our results show that site treatments and tree planting can have long‐lasting impacts on soil conditions and that these changes can support multiple urban land management objectives.

Urban forested natural areas are valuable ecological and social resources, but long‐term sustainability of these habitats is challenged by environmental and social factors associated with urban ecosystems. Advances in city‐scale assessments of urban forests have increased the resolution of forest community types and conditions, allowing for improved understanding of ecological function, such as natural regeneration, in these urban habitats. By applying metrics of tree regeneration that are commonly used for the management of rural forests, urban ecologists can test the potential for traditional forest management strategies within our cities. In this study, we compare urban and rural oak–hickory forest composition and structure and the capacity for natural regeneration in the New York metropolitan area. Specifically, we use two metrics of advance regeneration that describe the abundance of seedlings and saplings at different size classes to test whether this management for natural regeneration is a viable option. We found differences in recruitment dynamics between urban and rural forests that have implications for the sustainability of these forests and new management strategies. First, after controlling for forest community type, species composition in urban and rural sites was significantly different across multiple strata and within the seed bank. Species‐specific capacity for natural regeneration was different in urban and rural sites, signaling the possibility of divergent successional trajectories. Second, while differences in species composition exist, both urban and rural sites were dominated by native species across all forest strata except for urban seed banks. Third, despite finding significantly lower average annual seedling abundance in urban (1.9 seedlings/m²) compared to rural (7.1 seedlings/m²) sites, we observed greater density of saplings in urban forests, and no significant difference in stocking index between sites. These findings suggest that early‐establishment barriers to recruitment are greater in urban forest sites. However, once established, seedling transition into advance regeneration stages may not be different between site types, and advance regeneration may, in some cases, be more viable in urban forested natural areas. These results highlight functional differences between urban and rural forest recruitment dynamics that may impact on the future community composition of oak–hickory forests in the two landscape settings.

Forested natural areas in cities provide a range of social, ecological, economic, and health benefits. Ensuring the delivery of these benefits requires an understanding of current and potential future forest conditions, yet urban forest dynamics are not well‐understood. Here, we address this knowledge gap by examining forest structure and composition in 126 plots distributed across three forest patch sizes (large [95–126 ha], medium [1–19 ha], and small [0.05–0.65 ha] patches) in the city of New Haven, CT. We detected significant shifts in forest structure and composition suggesting a suite of distinct successional trajectories within each patch size. Large patches comprised 95% native tree species in the canopy (>5 cm dbh), sapling (1–5 cm dbh), and seedling (<1 cm dbh) layers, suggesting that these large patches will continue to be native‐dominated in the future—a primary objective for urban forest management. Moreover, in these large patches, shifts in the dominant species in each stratum suggest that as large patches move through succession they will transition from moderately shade‐tolerant forest types (i.e., oaks) to shade‐tolerant types (i.e., American beech)—a similar successional trajectory to surrounding second‐growth forests in the region. Medium patches were the most heterogeneous patch size sampled. Despite this heterogeneity, they generally resembled large patches in the canopy and sapling layers but diverged in the seedling layer. In medium patches, the invasive Norway maple replaced American beech as primary seedling species suggesting a future shift toward non‐native‐dominated forest in the future. Small patches were the most compositionally and structurally distinct patch size sampled. Only 36% of the canopy trees and saplings in small patches were native species; however, this increased to 71% native in the seedling layer. Additionally, the most important seedling species included those that are bird‐dispersed highlighting the potentially valuable role that these small, non‐native, forest fragments play as wildlife corridors. Collectively, our study demonstrates that multiple forest types, dynamics, and conditions can be found within a single city and that forest patch size offers a helpful framework to begin to parse out these differences.

Poplar tree improvement strategies are needed to enhance ecosystem services’ provisioning and achieve phytoremediation objectives. We evaluated the establishment potential of new poplar clones developed at the University of Minnesota Duluth, Natural Resources Research Institute (NRRI) from sixteen phytoremediation buffer systems (phyto buffers) (buffer groups: 2017 × 6; 2018 × 5; 2019 × 5) throughout the Lake Superior and Lake Michigan watersheds. We divided clones into Experimental (testing stage genotypes) and Common (commercial and/or research genotypes) clone groups and compared them with each other and each NRRI clone (NRRI group) at the phyto buffers. We tested for differences in clone groups, phyto buffers, and their interactions for survival, health, height, diameter, and volume from ages one to four years. First-year survival was 97.1%, with 95.5%, 96.2%, and 99.6% for the 2017, 2018, and 2019 buffer groups, respectively. All trees had optimal health. Fourth-year mean annual increment of 2017 buffer group trees ranged from 2.66 ± 0.18 to 3.65 ± 0.17 Mg ha⁻¹ yr⁻¹. NRRI clones ‘99038022’ and ‘9732-31’ exhibited exceptional survival and growth across eleven and ten phyto buffers, respectively, for all years. These approaches advance poplar tree improvement efforts throughout the region, continent, and world, with methods informing clonal selection for multiple end-uses, including phytotechnologies.