Abstract Urban forests have been widely recognized as a nature-based solution to address urban environmental changes like urban heat islands. Although previous studies have explored the cooling effects of urban forests, the extent of this effect and related influencing factors remain unclear and have not been comprehensively synthesized yet. To fill this research gap, we conducted a systematic literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method with 20 keywords and their combinations in Web of Science to address 3 main research questions: (1) what is the cooling range of urban forests; (2) what are the factors that may affect the cooling effects; and (3) how can we better manage urban forests to optimize cooling effects? We systematically reviewed 73 peer-reviewed articles selected from an initial pool of 4,072 search results following the PRISMA method. We found that urban greenspaces generally have cooling effects, but it is challenging to draw a clear conclusion on the cooling range due to variation in study design, measurement approaches, spatial scales, and local climate contexts. Moreover, the main influencing factors include land cover compositions, tree cover and canopy structures, leaf area index, forest types and tree species, and spatial arrangements of urban vegetation. Additionally, the cooling benefits of urban forests might be affected by local background climate and weather conditions, as well as distances from water bodies. These findings can help guide urban greening efforts (e.g., land cover types, tree species selection, and spatial arrangements) to achieve a greener and cooler future.

Abstract Background Tree roots colonize cracks in rock and similarly confining spaces in built environments, contributing to natural weathering processes and urban infrastructure dysfunction. Methods In this study, we assessed the limits of radial expansion in woody Quercus virginiana Mill. and Taxodium distichum (L.) Rich. roots grown in clamps under increasing tension. Results After two growing seasons, a maximum stress threshold for radial growth in mature structural roots was identified and was similar for both species. These thresholds (0.173 MPa to 0.329 MPa) fall within the lower to middle range of values reported in previous studies and are notably lower than those observed in seedling radicles or in other woody species under more acute stress exposure. Conclusions Our findings provide some of the first empirical estimates of pressure thresholds for deformation in mature woody roots, suggesting that structural root flattening can occur at relatively modest stress levels. These results offer important insights for the design of urban infrastructure aimed at minimizing root-related damage while also informing future biomechanical studies of species-specific responses to soil confinement.

Abstract Background Urban forests enhance mental health by reducing loneliness, fostering connections to nature, and reducing stress and anxiety. There is growing interest in understanding how urban forests can help support mental health across the life course, including among young adults. Given the known psychological and social benefits of nature-rich environments, it is critical to evaluate the functionality and usage of urban forest spaces for specific groups, particularly those at higher risk of mental health conditions like the members of this age group. Methods This student-led research study at the University of British Columbia’s Vancouver campus applied a mixed methods approach to assess the role of campus courtyards in supporting student wellbeing, with the ultimate aim of informing inclusive and effective spatial planning. Eight courtyards were analyzed via surveys and participant observation to understand their restorative and social benefits. Involving students as researchers played a vital role in offering alternative perspectives that helped identify previously overlooked gaps in this field. Results Our findings highlight the value of nearby, convenient greenspaces for young adults. There were 46 survey participants who shared their experiences in UBC courtyards, focusing on restorative and social benefits; 139 courtyard uses were observed by student researchers. Courtyards varied in biodiversity, order, and seclusion. Biodiverse courtyards received higher ratings for restoration, while social courtyards were linked to less reported guilt due to taking breaks. Across courtyard design typologies, students valued privacy, vegetation, and a sense of inclusion, although feelings of loneliness and discontent persisted. Conclusions This study demonstrates the value in engaging students as researchers to understand student perceptions of a campus urban forest for supporting wellbeing, social connection, and academic achievement. Although greenspaces such as courtyards are known to have restorative potential, they are not always designed to fully support student needs, highlighting the importance of student-informed planning frameworks that address existing gaps and foster more accessible, functional, and representative greenspaces on campuses.

Abstract Background It is essential to provide higher quality environments for the development of human activities in urbanized areas, such as better adapted urban centers. Regarding concerns related to climate change, there is a discussion about joint efforts to establish an ideal standard to be followed worldwide, significantly increasing the ecosystem services provided by urban forests, which directly affects the community’s quality of life. Methods This research aimed to characterize neighborhoods with different per capita incomes according to the 3-30-300 guideline in Cachoeiro de Itapemirim, a medium-sized Brazilian municipality. An inventory of the road component of urban forests was carried out for 9 neighborhoods from 3 different economic strata based on average per capita income. Results No neighborhood considered in the different per capita incomes fully complied with the 3-30-300 guideline. There was no difference in applying the guideline about the socioeconomic distinctions of the neighborhoods evaluated. Only 1 neighborhood in 9 evaluated (Neighborhood H) presented canopy coverage values above 30% because its urbanization process had not fully occurred, thus presenting a high percentage of the remaining natural forest matrix. Only one neighborhood evaluated (Neighborhood F) had all residences no more than 300 m from a public green area. Conclusions There is a need for public authorities to assess the implementation and maintenance of urban forests in the municipality, aiming to increase them significantly. It is worth noting that when the urban environment is not planned considering the precepts of 3-30-300, its parameters can be measured using it.

Abstract Background To better understand the impacts of storms on urban forests and to develop effective management strategies, it is essential to collect accurate and consistent data on urban forests before and after a storm. However, there is often limited time for researchers to establish sampling protocols and gather data before cleanup efforts erase key visual information, such as failure modes and damage severity. Moreover, storms differ in how frequently and predictably they impact regions, potentially limiting some researchers’ opportunities to gain experience with storm assessment methods. Methods This paper presents a standardized protocol for collecting pre- and post-storm data on urban forests based on previous studies and the authors’ experiences collecting urban tree data following severe storms. Results The protocol covers a wide range of data, including tree species, size, and condition; risk factors; and damage type. The protocol also includes instructions for post-storm data collection using a variety of methods, including field surveys, remote sensing, and citizen science efforts. Conclusions A standardized protocol will help researchers collect consistent data on urban forests before and after storms, while also making the findings more relevant to urban forest managers, as the data will align with what they already collect.

Abstract BackgroundLarge urban centers, such as São Paulo, have green areas interspersed with asphalt and buildings, requiring periodic maintenance to avoid issues with electrical networks. Urban tree management generates tons of pruning waste that is often deposited in landfills. Therefore, it is essential to discard these residues sustainably by composting and reusing the material to generate bioenergy and value-added products that support a circular economy.MethodsThis study aimed to evaluate the biomass potential of pruning tree waste through a composting system by characterizing the cell wall composition, starch, lignin, and saccharification capacity.ResultsThe fermentable sugars in pruning tree waste are degraded during the composting process; however, the levels of starch, galactose, xylose, and arabinose are maintained during the first weeks of composting.ConclusionsThese sugars can be utilized for energy production and contribute to the saccharification capacity. Throughout the 32-week composting process, lignin is not degraded; however, the decrease in other sugars in the biomass increases the proportion of lignin, suggesting opportunities for the use of thermal energy and green chemistry.

Abstract Background Hawai‘i’s exceptional trees are currently identified based on 7 selection criteria established in 1975. These criteria and their corresponding program components have remained stagnant with minimal improvements since the program’s inception. This study builds upon previous exceptional (aka “heritage,” “significant,” “champion,” “monumental,” “notable,” etc.) tree research conducted in other geographic locations in an attempt to discover if consensus exists regarding how these trees of importance should be identified, managed, and protected. Methods A panel of 13 experts from around the state were presented 45 exceptional tree selection criteria and several program components using a 3-iteration Delphi method to determine if consensus exists on which selection criteria and program components should be used by Hawai‘i’s Exceptional Tree Program. Results The results identified 33 exceptional tree selection criteria and 5 program components (i.e., protection mechanisms, private property exceptional tree maintenance costs, funding, public education and outreach, and program management best practices) recommended by the expert panel, as well as examples of how each should be implemented to improve the efficacy of this conservation program. Conclusions These findings add to a growing body of exceptional tree research designed to identify, recognize, and protect a region’s most valued trees, while also having applicability to urban forestry programs more broadly.

Abstract Urban forest management is a multistakeholder, multi-objective situation whereby a surfeit of synergistic or competing goals may exist. Greater research and applied guidance for what works in which urban forest contexts could help improve urban tree and forest outcomes. The challenge in conducting research of this nature is systematic definitions of “what works” and “which contexts” across multidimensional, polycentric urban forest social-ecological systems. This paper presents a comprehensive framework for studying the complexities in urban forest systems (synthesized from numerous other frameworks in the field) that could be used to generate context-specific insights into urban forest management and dynamics. The logic of using frameworks and specific frameworks that already exist within the field are reviewed. Then, I present the urban forest social-ecological system (UFSES) framework. The UFSES framework specifies 5 first-tier factors: theCharacteristics of Trees in the Urban Forest (T); theSurrounding Growing Environment (E);Management & Institutions (M); andCharacteristics of the Human Community (H); which influenceUrban Forest Outcomes (O). A detailed set of second-tier variables nested within these factors are presented in tables at the end of the paper. The framework can foster holistic systems thinking in a systematic yet flexible way; provide a working draft of a common language for thinking about and studying urban forest systems; and enable comparative case research.

Abstract The expansion of the use of induced resistance (IR) has been, and remains, an attractive prospect for the management of woody plants, but little research has occurred assessing the ability of elicitors to induce the root defenses of woody plants. Eastern white pine (Pinus strobus) was used as a model plant to assess IR elicitation. Containerized plants were treated with phosphite (Phi), chitosan, curdlan (a β-1,3-glucan polymer), or silicon (Si) on 2022 June 7. The soluble phenolic levels, tissue levels of major resin acids (abietic and neoabietic), as well as the activities of peroxidase (POX), chitinase (CHI), and β-1,3-glucanase (βGLU) of fine roots were compared across elicitor treatments and nontreated controls on June 10, June 14, and June 27. There were no changes post-treatment to soluble phenolics or resin acids at any sampling point, but chitosan treatment resulted in an increase in POX and CHI activities, while curdlan increased CHI activity on June 10. On June 14, curdlan-treated plants had significantly higher POX and CHI activities, while Phi-treated plants had significantly higher POX activity. By June 27, curdlan- and Phi-treated trees had significantly higher CHI activities. Our data suggest that chitosan, curdlan, and phosphite stimulate biochemical responses and potentially prime root systems to respond to subsequent stresses, but there appears to be variation between these elicitors regarding rapid versus longer lasting IR effects.

Abstract Background Silicon in plants is a structuring element that promotes water and saline stress tolerance and decreases transpiration. The silica accumulated in the cuticle establishes a physical barrier and helps fight against pests and diseases. The present study aimed to evaluate the development of ipê-roxo (Handroanthus impetiginosus) seedlings in different environments, and the application of potassium silicate and its efficiency in mitigating the attack of pests and diseases. Methods The experiment was carried out in an agricultural greenhouse and under full sun with silicic doses of 0 and 7.15 mg per plant in a completely randomized design arranged in a 2 × 2 factorial scheme, with 6 replications of 4 seedlings per plot. Plant height, chlorophyll, stem diameter, number of leaves, shoot dry matter, root dry matter, total dry matter, height-diameter ratio, root-shoot ratio, root-plant ratio, Dickson quality index, disease severity, and pest intensity were evaluated. Results Silicon application did not confer biometric qualities to the seedlings. The application of silicon conferred 24.6% higher protection against disease severity at a 90% probability level. The protected environment promoted 48.8% more protection against the attack of pests on the seedlings. The silicon application decreases the intensity of pests in the protected environment by 36.3%. Seedlings in a protected environment increase the production of chlorophyll but are 29.6% more susceptible to the severity of diseases. The full sun promoted greater diameters, phytomass, and Dickson quality index by 18%, 73%, and 195%, respectively. Conclusions The bestHandroanthus impetiginosusseedlings were obtained under full sun. Silicon mitigated the attack of pests and diseases onHandroanthus impetiginosusseedlings.