This study compared the phenotypic traits and microclimate parameters of street trees as affected by species origin (native [N] vs. non-native [NN]) and location (inside vs. outside the University of the Philippines, Los Baños [UPLB]).

Tree traits were counted and measured using a meter tape and a range finder, while microclimates (air temperature, relative humidity, heat index, light intensity) under tree canopies and adjacent exposed areas were gathered using a multifunctional environmental meter and a light meter.

T-test analysis revealed that tree traits differed significantly but not in terms of microclimate, except for crown-shaded light intensity, with NN trees showing a significant reduction compared to N trees. Meanwhile, tree traits as affected by location showed significant variation only in the number of major branches, with trees outside UPLB registering more branches than the other location. Moreover, multiple linear regression indicated which part of the trees had a strong influence on crown-shaded microclimate, while results of correlation analysis showed that phenotypic traits, except for the relationship between total height and crown traits, regardless of their species’ origin, were significant, positive, and strongly correlated.

T-test analysis highlighted that street trees in solitary and/or small aggregates tend to enhance the production of protective (e.g., leaves) rather than productive (e.g., stems) traits, while correlation analysis suggested that interventions (e.g., pruning) could improve the trees’ crown-shaded microclimate condition. These findings could provide technical guidance for a more sound decision for the inclusion or removal of street trees in urban areas.

Urban landscaping enhances environmental quality but often overlooks the allergenicity of plant species, impacting public health. In Ukraine, pollen monitoring is not systematically regulated. This study aimed to assess the allergenic load of tree species in Kharkiv, Ukraine, based on aerial pollen surveys, and to identify the most allergenic species and peak periods of pollen emission.

From March to June 2024, aerial pollen samples were collected in the Novobavarskyi and Saltivskyi districts of Kharkiv using the gravimetric Durham method at 1.5-m and 15-m height. Pollen grains from woody plant species were identified and quantified. Potential allergenicity was assessed through the CARE-S index, which considers immunogenicity, morphology, and pollen production characteristics. The newly proposed Total Pollen Allergenic Load Index (PL) allowed us to identify periods of high allergenic risk.

The survey detected pollen from 16 tree species, with Betula pendula, Pinus sylvestris, Corylus avellana, and Juniperus sabina showing the highest allergenicity. The integrated PL effectively reflected the cumulative allergenic potential of the airborne pollen spectrum, allowing identification of distinct seasonal peaks. The highest pollen deposition and allergenic loads were recorded between May 5 and May 15, when 8 tree species released pollen simultaneously, 2 of which—B. pendula and P. sylvestris—contributed most to the total allergenic load.

Several indigenous and introduced tree species in Kharkiv contribute significantly to airborne allergenic loads. Regular monitoring using volumetric methods is necessary to create reliable pollen calendars and guide safer urban landscaping practices, ultimately improving public health outcomes.

Urban soils often have low-nutrient levels, reduced biota, and frequently depauperate humus. Castanopsis sieboldii trees planted in cities may grow poorly in some areas. This study investigated the effects of soil chemical and biological properties on C. sieboldii growth.

Individual and compound impacts of N (nitrogen), P (phosphorus), K (potassium), and Ca (calcium) on saplings grown in humic topsoil, humic subsoil, and river sand were investigated.

Addition of N alone and combined with P, K, and Ca affected C. sieboldii growth in humic topsoil and subsoil. Applications of N alone, in river sand with low levels of available nutrients, had no impact. However, combined nutrients such as N with P, K, and Ca increased shoot and root dry weights, number of leaves, and soil and plant analyser development (SPAD). Additionally, NPCa and NPK resulted in higher values than individual N for dry weights of shoots and roots as well as for shoot dry weights in river sand. NPKCa application resulted in increased diameter at the base of the first branch in humic topsoil over N alone. NPK produced more leaves in humic subsoil than just N. Moreover, C. sieboldii produced the greatest growth in humic topsoil, followed by humic subsoil, and finally unfertilised river sand.

Nitrogen application with additional P, K, and Ca was beneficial to growth under test conditions. Castanopsis sieboldi growth was enhanced under field conditions with humic topsoil and combined nutrients. Low available P, K, and Ca may be limiting factors restricting performance impacts of N when added alone to low-nutrient soils.

Trees provide crucial ecosystem services for urban areas, but the stress of the urban environment can influence tree health and ecosystem service provision. Street trees grow in particularly stressful conditions, but often receive care from some combination of municipal agencies, private businesses, nonprofits, and individuals.

In this study, we quantified tree stress using 4 canopy-based metrics (leaf discoloration, leaf defoliation, dieback, and overall crown stress) to see how stress varies with growing conditions and tree characteristics in 2 US cities: Chicago, IL, and Durham, NC. Using separate Bayesian models for each city, we examined the relationship between tree stress and tree characteristics (e.g., species), site-condition variables (e.g., land use) and cues to care (e.g., mulch).

In both cities and for most tree stress metrics, the degree of tree stress was associated with species group and either site type and/or land use. Cues to care were not clearly associated with reduced stress in either city. Defoliation was better explained by the models than the other metrics of tree stress. Discoloration, defoliation, and dieback provided unique information on tree stress and therefore can be useful indices for tree health monitoring.

Consistent with arborist practices, species selection plays a large role in informing the degree of tree stress. Because the benefits of tree care were unclear, future work focusing on the context dependence of tree care effectiveness could clarify the conditions under which tree care (especially mulch) is most effective.

Practitioners rely on sample-based estimates of street tree population characteristics when complete inventories are not feasible. Selecting a sample size is a primary consideration when implementing a sample-based inventory, as it involves a tradeoff between costs and data quality.

We used street tree inventory data from 16 municipalities in Indiana, USA, to assess how data quality improves with increasing sample size. Specifically, we conducted 1,000 random draws of street segments at increasing sample depths to observe how estimates improved for the number of total trees citywide, species richness, species diversity, and vulnerability to an invasive pest.

Compared to previous research, our results indicate that a larger percent of sampled street segments is needed to achieve relative standard error values below the heuristic target of 10%. We also calculated reliability thresholds that showed the percent of street segments that would need to be inventoried to achieve estimates within a given margin of the true citywide value in 95% of random draws. Again, relatively large random samples were needed to reliably achieve accurate estimates of street tree characteristics, especially in smaller municipalities.

This study provides information that practitioners can consider when planning street tree sampling given the community’s size, capacity to inventory trees, and level of data quality needed for planning and management activities. In general, we suggest that municipalities may need to acquire larger samples than previously thought to achieve accurate estimates of citywide street tree characteristics, and smaller municipalities should conduct complete inventories when possible.

For the past 20 years, approximately twice as many trees were removed annually from urban areas in the USA as were harvested annually from the US National Forest System. Yet, most of this wood is treated as waste instead of as a valuable resource to generate economic growth and sustainable cities. Residential landowners are key actors in the establishment of local urban wood economies as both sources of material and users of urban wood products, yet they remain a difficult to reach group compared with others, such as tree care companies, mill operators, and public landowners.

We analyze a representative survey of urban residential landowners in 6 United States cities. We assess (1) status of participation in urban wood systems; and (2) interest in and perceived importance of urban wood products.

Overall, 15% of residential landowners reported purchasing or acquiring urban wood products in the past. Landowners were more likely to purchase—and were more interested in—lower value products like wood chips and compost than higher value products like lumber or furniture. Private sector actors, like landscaping and tree care companies, and social sources, like friends and family, were more often recognized as sources of trusted information for tree care advice than local or state government and nonprofit organizations.

We present baseline results of, to our knowledge, the largest survey of urban wood perceptions and practices to date, which indicate a substantial group of landowners already engaged in urban wood economies, and discuss potential avenues to activate future participation.

Tree roots colonize cracks in rock and similarly confining spaces in built environments, contributing to natural weathering processes and urban infrastructure dysfunction.

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.

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.

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.

Stem respiration is influenced by elevation, but this phenomenon has not been adequately studied for palms. Therefore, the influence of stem height on carbon dioxide efflux (E_s) was determined for 6 palm species.

Gas exchange protocols were employed to determine E_s. The lowest height was 35 cm above the root collar, and the greatest height was 20 cm below the oldest living leaf in the crown.

A consistent baseline flux was observed for the midlength of the stems, a moderate increase in E_s occurred at the lowest elevation, and a substantial increase in E_s occurred at the highest elevation. The midheight flux ranged from 0.9 µmol·m^–2·s^–1 for Corypha utan to 2.3 µmol·m^–2·s^–1 for Carpentaria acuminata. The basal increase in E_s averaged 63% and was greatest for C. utan and least for Phoenix sylvestris. The apical increase in E_s averaged 157% and was greatest for Wodyetia bifurcata and least for C. acuminata. A quadratic model described the influence of stem height on stem E_s.

The moderate increase of E_s at the lowest stem height was consistent with the influence of root-respired carbon dioxide entering the stem in xylem mass flow then conducting radially to the stem surface. The substantial increase in E_s at the highest stem height was consistent with proximity to the growth respiration of the large primary thickening meristem of the pachycaulous palm stem. These findings confirm that the elevation of the stem influences palm E_s, and the elevation pattern is consistent among every species.

Street tree plantings are common in urban greening programs, and these trees provide important ecosystem services that increase as trees survive to maturity. Field-based monitoring to understand mortality rates and causes is valuable for urban forest management but very time-consuming.

We used street-level imagery to virtually monitor survival for 2,884 street trees over several years postplanting in Philadelphia, Pennsylvania, United States.

We observed similar mortality rates to other studies, with 7.5% of trees dead or removed by the first summer after planting and the mortality rate dropping to 3.5% between the third and fourth summers postplanting. Logistic regression models were constructed over various time horizons to understand which site, neighborhood, and species characteristics related to survival outcomes. These models showed that higher tree survival was associated with less impervious surface surrounding the tree; lower social vulnerability in the neighborhood; and tree planting in the fall season as opposed to spring.

Our results point to management activities that could improve survival outcomes, such as planting site enhancements and establishment maintenance, as well as the use of monitoring data to drive decisions regarding planting season. This study demonstrates the value of street-level imagery interpretations to provide mortality data on a large number of street trees planted over multiple years.

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.

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.

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.

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.

While many tree professionals recognize the importance of planting quality stock and a diversity of species to enhance longevity and increase urban forest resiliency, the availability of such stock is often limited.

To address this disconnect, we conducted 3 focus groups with growers, designers, urban foresters, and other technical experts from the Chesapeake Bay watershed region (USA) to identify challenges and opportunities for growing greater numbers of high-quality, underused species.

Contract growing was seen as a key opportunity for increasing quality and diversity. Additionally, increased communication between growers and tree purchasers, as well as potential partnerships with nonprofit or state nurseries, were identified as potential solutions where the marketability of underused species was limited. There were differences among participants regarding their preferences for native species, non-native species, cultivars, and non-cultivars.

While this research focused on the tree supply chain within the Chesapeake Bay watershed, many of the challenges and opportunities discussed are not region-specific, making our findings applicable to professionals beyond the study area.

Small and large cities typically both have street trees, but small cities have fewer resources to manage them. Three 1980s papers assessed that small rural cities in the state of Iowa, USA, were at a disadvantage in managing street trees as reflected in the diversity, age, and condition of their street tree populations. This paper analyzes more current street tree inventory data in conducting a similar assessment.

Street tree inventory data were obtained from small, midsize, and large Iowa cities for 2008 to 2024. Tree diversity, age, and condition were analyzed based on city size. Diversity was assessed by relative abundance percentages and diversity index statistics, age by trunk DBH distributions, and condition by ratings for tree wood and leaves.

Small cities have less street tree diversity than midsize and large cities. A diversity t-test found statistically significant differences based on city size. Small and midsize cities were found to have older tree population profiles than large cities. Large and midsize cities had better condition wood ratings than small cities, but little difference was found between cities for leaf condition.

Inventory data suggest that Iowa’s small cities still face challenges managing their street trees. Lack of funding is the reason most often cited. Progress is being made although its extent cannot be determined due to lack of longitudinal data. There remains a need to assist Iowa’s small cities in sustainably managing their street trees and maintaining the benefits they provide.

The periodical cicadas of Brood X (Hemiptera: Cicadidae) emerged in the summer of 2021, shortly after several thousand trees were planted throughout the District of Columbia, USA, during 2020 to 2021. There was concern that the millions of cicadas would negatively impact recently planted trees. This presented an opportunity to assess the impacts of periodical cicadas on an urban tree planting program.

Newly planted trees were surveyed, with field inspections and remote sensing techniques, for evidence of cicada egg laying and twig damage related to tree genus and location within trees and throughout the District.

There were significant differences in egg-laying behavior among 10 tree genera, with the most damage observed in Acer and Nyssa. Egg laying occurred most often in scaffold and lateral branches. Egg-laying intensity was positively correlated with percent foliage lost. There was little evidence of cicada impacts on tree health as tree condition was unrelated to egg-laying intensity. Survival of the 2020 to 2021 tree cohort was similar to previous years without a large-scale cicada emergence. Remote sensing was unsuccessful in differentiating cicada caused damages from other damage.

Municipal urban forestry departments facing a large periodical cicada emergence may continue tree planting campaigns and avoid damage to new trees by choosing less preferred genera. Although useful, remote sensing products are not currently at the point where a non-remote sensing specialist can acquire and utilize these tools for identifying cicada damage. Field surveys are recommended for accurate delimitation of cicada activity in urban settings.

This study aimed to evaluate bioactive compounds and initial growth parameters of Jacaranda mimosifolia seedlings under shading levels and substrate compositions.

A completely randomized design arranged in a 3 x 5 factorial scheme (3 shading x 5 substrates) was used. The shading levels were 0%, 30%, and 50%. The substrates were compost made up of organomineral material (M) and vermiculite (V): 100/0 M:V, 80/20 M:V, 60/40 M:V, 40/60 M:V, and 20/80 M:V.

Producing J. mimosifolia seedlings under the full sun is not recommended in tropical conditions. The 30% and 50% shade screens reduced photosynthetically active radiation by 38% and 62%, respectively. In the 50% shading environment, the average number of leaves increased by 68%, the stem diameter by 60%, the shoot dry matter by 250%, the root dry matter by 113%, the total dry matter by 184%, and the quality of the J. mimosifolia seedlings by 127%. The cultivation in the 50% shading environment, on average, increased the chlorophyll a content by 77%, the chlorophyll b content by 56%, the total chlorophyll content by 70%, and the carotenoid content of the J. mimosifolia seedlings by 45%. A substrate containing 20%M for J. mimosifolia seedlings is not recommended. The best J. mimosifolia seedlings are produced in the 50% shading environment and the 100%M substrate, resulting in better biometric quality and higher chlorophyll and carotenoid contents in addition to promoting an improvement in the survival rate and acceleration in initial growth.

Sustainable cities will require water sensitive urban design (WSUD) that integrates street trees, urban soils, and engineered infrastructure. However, there can be a perception that these systems contribute to ground/soil movement that can be problematic for hard infrastructure. There is concern that diverting water into kerbside harvesting systems for street trees may exacerbate ground movement.

Twenty-eight small kerbside stormwater harvesting systems that diverted storm runoff into roadside soakage wells were dispersed along a residential street in an inner suburb of the City of Adelaide, South Australia. The wells can be utilized with or without the presence of street trees, but greater utility and environmental benefits could be achieved with vegetation. Regular measurements of ground level were undertaken to determine ground movement over a period of 2 years, comparing sites with and without soakage wells.

Results showed that stormwater harvesting and infiltration into the site’s reactive clay did not increase ground movement at the kerb or at the road surface during periods of above and below average rainfall. Kerb levels generally remained within +10 mm (heave) and –15 mm (settlement) of the reference datum, and movement at the top of the asphalt road seal was no greater than +7 mm or –6 mm. The maximum extent of ground movement (sum of the maximum heave and maximum settlement) at any point was 26 mm, but typical movement at 9 points, 6 of which were near inlets, was 4 mm. Ground movement was of similar amplitude near and further from infiltration points and was unaffected by stormwater harvesting.

The use of trees within WSUD, particularly in fine clay soils in which root growth increases water harvesting and storage, can substantially contribute to urban hydrology through canopy rainfall interception, hydraulic redistribution, enhanced soil conductance through biopore creation, and preferential flow along root channels. This research shows that the presence of soakage wells does not lead to increased ground movement in reactive clay soils.

Urban afforestation is widely recognized for providing numerous aesthetic and functional benefits to both the population and the environment. However, poor planning ranging from improper species selection to inadequate tree management can lead to various issues, including accidents caused by falling trees. These incidents often result from root failure, underdeveloped root systems, or advanced tree degradation.

To evaluate a tree’s root system, indirect methods are recommended, particularly in urban environments with sidewalks or pavements. Techniques such as sonic tomography and ground penetrating radar (GPR) each have their own advantages and disadvantages when applied to urban trees. This study aimed to assess and compare qualitatively the use of sonic tomography and GPR to characterize the root systems of 5 trees located on a sidewalk and in a square. Additionally, a new visualization approach for tomographic data is presented, using kriging interpolation of velocity and error values.

The results established a qualitative relationship between the high velocity zones detected by tomography, indicating root presence, and the roots mapped by GPR. The new visualization of tomography data provides better opportunities for clearer interpretation together with information of measurement errors.

Sonic tomography and GPR both assess trees roots in urban environments, but sonic tomography is faster for mapping the extent of root coverage, whereas GPR provides a more detailed characterization of the root system’s spatial distribution, depth, and diameter of coarse roots.

A widespread trend of declining and dying mature oaks has been observed in the Chicago region since 2019. While there have been studies on the stress-physiology of white oaks and the epidemiology of decline diseases, there have not been any studies focusing on the relationship between predisposing abiotic site and soil characteristics and white oak decline in the Chicago metro area. The objective of this study was to determine if site and soil characteristics are significantly related to white oak decline in the Chicago region.

Soil and site characteristics were compared between 66 healthy and declining trees of the white oak group on 32 sites in the summer of 2023. During site visits, deep pedon samples, composite soil samples, fine roots for oomycete detection, site characteristics, tree health assessments, and site management information were collected. DAS-ELISA Phyt tests and soil lab analyses were conducted.

Low micronutrient levels, compaction, elevated soil sodium, and poor drainage appear to be the most relevant predisposing abiotic site characteristics for white oak decline through ANOVA and GLMMs. The ELISA Phyt tests were 88% positive for both healthy and declining trees.

Results from this study can help arborists and urban foresters improve management and treatment design and implementation for white oaks, improve our understanding of the predisposing factors influencing the health of managed trees, and improve future planting guidelines.

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.

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.

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.

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.

This study demonstrated the potential of in-ground (IG) termite monitoring stations coupled with chitin synthesis inhibitor (CSI) baiting as a complementary solution to visual inspection for tree termite detection and control in Singapore.

Using lure wood pieces collected from activated IG stations to serve as a basis for comparison, we evaluated the destructiveness of detected termite species and reported their unique feeding patterns. Chitin synthesis inhibitor (CSI) baiting with chlorfluazuron was used for termite control.

A total of 6 termite species were detected: Coptotermes gestroi (Wasmann), Coptotermes curvignathus (Holmgren), Schedorhinotermes medioobscurus (Holmgren), Macrotermes gilvus (Hagen), Macrotermes carbonarius (Hagen), and Microcerotermes crassus (Snyder). However, the detection capability varied depending on site conditions such as intermittent flooding events, high soil salinity, and reduced foraging behavior after nesting within or near a host tree. This behavior of reduced foraging, in part, could be affected when heavily infested trees are removed, forcing termites to migrate and search for new food sources, leading to activation of nearby IG stations. In terms of termite control, CSI baiting with chlorfluazuron could effectively eliminate termite colonies for 3 species: C. gestroi, C. curvignathus, and S. medioobscurus. Colony elimination time ranged from 3 to 6 weeks and 24 weeks, respectively.

Considering the effectiveness of IG stations coupled with CSI bait in detection and control of subterranean termite species, large-scale application of this system in an urban tree context is discussed.