Urban Forest Research Articles

Nitrogen addition weakens home-field advantage of litter decomposition by altering soil pH and bacterial communities in a subtropical forest

Abstract The home-field advantage (HFA) hypothesis predicts that litter decomposes faster in its home environment than elsewhere. Given the critical role of HFA effect on litter decomposition in terrestrial carbon and nutrient cycling, it remains unclear how nitrogen (N) deposition affects this effect. Here, we conducted a 12-month field experiment involving reciprocal litter translocation, with four N addition levels (0, 30, 50, 100 kg N ha−1 yr−1), in Quercus acutissima and Pinus massoniana stands in a subtropical urban forest and a mini meta-analysis of the effect of N addition on HFA in global forests. Results showed that a significant positive HFA of 3.98 was observed, but N addition (particularly with high rates) tended to weaken it, by decreasing it to −6.12 at 100 kg N ha−1 yr−1. Conversely, the combined HFA index increased with bacterial community dissimilarity between stands. Such relationships were due to that N addition changed soil bacterial diversity and composition in P. massoniana stand and led to the convergence of bacterial communities between stands, mainly by lowering soil pH. Similarly, our experiment and meta-analysis showed that the species-level HFA index and its response to N addition also decreased with N addition rate (P < 0.05), suggesting the generalization of how N addition affects HFA. Our findings suggest that soil acidification driven by N inputs indirectly reduces HFA through altering bacterial communities, which helps to better understand and predict the dynamics of HFA effect and the cycling of carbon and nitrogen in forest ecosystems under N deposition.

Minimizing the impact of invasive Coptotermes sp. (Heterotermitidae) on urban tree canopies using a recurrent inspection-elimination program.

Invasive subterranean termite species within the genus Coptotermes (Heterotermitidae) are important structural pests. However, they also cause extensive damage in live trees and pose serious risks to tree health as a result. The urban tree canopy in areas with established populations of Coptotermes are therefore at risk of loss of trees over time, and many urban forests within municipality parks in their introduced range may experience tangible canopy alteration. This can have wide-reaching negative impacts on the ecology of these parks and to the public that utilize them. This 5-yr long study utilized eight parks (1,304 trees) to demonstrate how a simple visual monitoring/bait approach can identify and eliminate termite colonies infesting trees and maintain minimal termite activity within public green spaces. Here, we demonstrate that the systematic direct application of an experimental above-ground chitin synthesis inhibitor (CSI) bait formulation to trees can eliminate termite activity and protect trees. However, owing to high termite pressure, colony reinfestation is likely over time, and municipalities may have to establish perennial programs that would include regular monitoring and treatment as needed. Such a long-term strategy would minimize tree loss, while using a termite-specific formulated pesticide with a low amount of active ingredient. This pilot study demonstrates that it can be achieved, but ultimately, the success of this approach relies on technically competent staff that can readily identify the signs of active Coptotermes infestation in trees and access to above ground CSI bait formulations.

Assessing the potential of multi-seasonal Sentinel-2 satellite imagery combined with airborne LiDAR for urban tree species identification

Accurate information on urban tree species composition is critical for urban green space ecosystem management. However, achieving large-scale, high-precision species identification in complex metropolitan environments remains challenging. This study assessed the potential of medium-resolution multi-temporal optical imagery combined with airborne LiDAR for tree species classification in large heterogeneous urban areas (> 5000 km²). The results indicate that precise large-scale identification of urban tree species distribution is feasible by integrating multi-seasonal Sentinel-2 imagery with airborne LiDAR data based on a Random Forest hierarchical classification model. The overall classification accuracies for deciduous broadleaf species and evergreen broadleaf species were 63.32% and 76.77%, respectively. Multi-temporal spectra were the primary explanatory variables, with spring bands significantly affecting the classification of deciduous broadleaf species. For evergreen broadleaf species, each season has its own dominant spectral information. Classifications combining data from three seasons outperformed single- or two-season combinations. The incorporation of LiDAR-derived metrics improved the classification results for most species, with accuracy increases of up to 18.75% point for deciduous broadleaf species. Overall, the results demonstrate the effectiveness of combining medium-resolution multi-temporal optical imagery with LiDAR data for urban tree species classification, laying a foundation for quantifying ecosystem services provided by urban trees through remote sensing.

Comparison of Acoustic Tomography and Drilling Resistance for the Internal Assessment of Urban Trees in Madrid

Acoustic tomography is a non-destructive technique used in the internal assessment of standing trees. Various researchers have focused on developing analytical tools using this technique, demonstrating that they can detect internal biodeterioration in cross-sections with good accuracy. This study evaluates the use of two ultrasonic wave devices with different frequencies (USLab and Sylvatest Duo) and a stress wave device (Microsecond Timer) to generate acoustic tomography using ImageWood VC1 software. The tests were carried out on 12 cross-sections of urban trees in the city of Madrid of the species Robinia pseudoacacia L., Platanus × hybrida Brot., Ulmus pumila L., and Populus alba L. Velocity measurements were made, forming a diffraction mesh in both standing trees and logs after cutting them down. An inspection was carried out with a perforation resistance drill (IML RESI F-400S) in the radial direction in each section, which allowed for more precise identification of defects and differentiating between holes and cracks. The various defects were determined with greater accuracy in the tomographic images taken with the higher-frequency equipment (45 kHz), and the combination of ultrasonic tomography and the use of the inspection drill can provide a more accurate representation of the defects.

Study on the restorative benefits of four behavioural patterns of urban landscape forests under seasonal change

Urban landscape forests (ULFs) are important green spaces that promote human well-being by providing health benefits and leisure opportunities. Most studies have concentrated only on health promotion differences in terms of plant community characteristics and have ignored the influence of a user’s own activity type. This study explores the restorative effects of different behavioural modes in deciduous ULFs. We chose 4 common behavioural modes, and a grouping experiment was conducted on a ginkgo scenic forest in Shuangliu Central Park, Chengdu, China. A total of 128 subjects were randomly divided into four gender-balanced groups. Physiological and psychological responses were evaluated using blood pressure, heart rate, electroencephalogram (EEG) measurements, and the Profile of Mood States (POMS) scale. The results revealed that the changes in systolic blood pressure and heart rate in the GL group decreased significantly, and diastolic blood pressure decreased significantly. In the monitoring of EEG changes, the α wave and β wave activity in the GS group and GW group were significantly increased. A comparison of the ANCOVAs among the four groups revealed that the α wave activity of the GS group was significantly greater than that of the other three groups (p < 0.001), the β wave activity of the GS group was significantly lower than that of the GW group, and the T–A mood values of the four behaviour pattern groups were significantly lower according to the POMS. According to the overall statistics of the available indicators, the health benefits of walking in autumn landscape forests are greatest, followed by sitting, lying and talking. The results of this research can encourage urban planners to consider appropriate behavioural guidance when developing nature tours or immersive nature projects on the basis of differences in behaviour patterns to gain more scientific insights into activity types.

Multi-Criteria Analysis of Three Walkable Surface Configurations for Healthy Urban Trees: Suspended Grating Systems, Modular Boxes, and Structural Soils

The conflicting demands of urban trees and walkable surfaces result in significant financial burdens for municipal administrators who understand that urban residents want tree-lined walkable surfaces. This study investigates three methodologies for mitigating this tension: suspended grating systems, modular box systems, and structural soils. A Multi-Criteria Analysis (MCA) was conducted to evaluate their suitability in dense urban areas, employing criteria categorized into Environmental, Economical, and Other considerations. The comparison focused on critical aspects such as the impact on tree health (root growth, water availability), installation complexity, initial costs, and overall suitability for diverse urban contexts. The MCA indicates that, under the given weighting of criteria, suspended grating systems (especially those suited for existing trees) rank the highest, primarily due to their superior root protection and minimal disturbance to established root systems. In contrast, modular box systems and structural soils emerge as particularly strong contenders for new tree plantings. Structural soils may have application at sites with existing trees, but the costs of removing native soil are a consideration. Sensitivity analysis suggests that modular box systems may become the preferred option when greater emphasis is placed on stormwater management and new plantings, rather than on challenges for existing trees or underground infrastructure. Structural soils score well in cost-effectiveness and installation speed but require careful implementation to address their lower root protection performance and long-term maintenance concerns. Ultimately, the optimal solution depends on unique site-specific conditions and budgetary constraints, emphasizing the necessity of tailored approaches to balance urban infrastructure with tree health.

The Role of Urban Green Spaces in Mitigating the Urban Heat Island Effect: A Systematic Review from the Perspective of Types and Mechanisms

Due to rising temperatures, energy use, and thermal discomfort, urban heat islands (UHIs) pose a serious environmental threat to urban sustainability. This systematic review synthesizes peer-reviewed literature on various forms of green infrastructure and their mechanisms for mitigating UHI effects, and the function of urban green spaces (UGSs) in reducing the impact of UHI. In connection with urban parks, green roofs, street trees, vertical greenery systems, and community gardens, important mechanisms, including shade, evapotranspiration, albedo change, and ventilation, are investigated. This study emphasizes how well these strategies work to lower city temperatures, enhance air quality, and encourage thermal comfort. For instance, the findings show that green areas, including parks, green roofs, and street trees, can lower air and surface temperatures by as much as 5 °C. However, the efficiency of cooling varies depending on plant density and spatial distribution. While green roofs and vertical greenery systems offer localized cooling in high-density urban settings, urban forests and green corridors offer thermal benefits on a larger scale. To maximize their cooling capacity and improve urban resilience to climate change, the assessment emphasizes the necessity of integrating UGS solutions into urban planning. To improve the implementation and efficacy of green spaces, future research should concentrate on policy frameworks and cutting-edge technology such as remote sensing.

Powdery mildew of oak (Quercus robur) caused by Erysiphe alphitoides in the Northwest of Argentina

The common oak, although infrequently, can be found as urban trees in the cities of northwestern Argentina. Between late 2023 and early 2024, leaves of Quercus robur exhibiting typical symptoms of powdery mildew were collected from three provinces in this region. Based on its morphological characteristics, host specificity, and the available descriptions, the fungus was identified as Erysiphe alphitoides in the asexual phase. This represents the first report of this fungus in northwestern Argentina. The symptoms of the disease, as well as the morphological characteristics of the anamorph are described and illustrated.

Neighborhood-scale reductions in heatwave burden projected under a 30% minimum tree cover scenario

Cities pursuing nature-based solutions to mitigate heatwaves need tools to estimate cooling benefits from increased tree canopy cover. This study applied the i-Tree Cool Air model and a heatwave degree day (HWDD) metric to quantify reductions in heatwave severity if neighborhoods in 10 Italian cities achieved the recommended minimum 30% tree cover. The scenario focused on establishing functional urban forests, with additional canopy placed over permeable surfaces to enhance stormwater infiltration and evapotranspiration-based cooling. Despite dry summer conditions, the 30% tree cover scenario reduced HWDD by a median of 34% (range: 16–84%), translating into comparable reductions (median 36%) in heatwave-related mortality for those aged 65 + . The tree cover generated new ecosystem service benefits valued at $10 million per city (range: $2–$62 million) through avoided stormwater runoff, air pollution removal, and carbon sequestration. Results consider drought constraints and potential irrigation trade-offs, including exacerbation of humid heat extremes.

Mapeando conexões entre tecnologias digitais e florestas urbanas na construção de cidades inteligentes e sustentáveis: uma revisão de escopo

In the face of increasing urbanization and environmental pressures, urban forests are emerging as strategic allies for smart and sustainable cities. However, there is a gap in the literature regarding the integration of digital technologies in the management of these spaces. This study maps the interactions between urban forests and smart, sustainable cities, emphasizing the role of emerging digital technologies. Through a Scoping Review, a portfolio of articles was constructed to explore the application of technological solutions, such as the Internet of Things (IoT), Big Data, and Geographic Information Systems (GIS), in the monitoring and management of urban forests. The analysis highlights that these innovations enhance sustainability, resilience, and urban well-being. Furthermore, the importance of smart governance, strategic urban planning, and citizen participation in the effective integration of these technologies is emphasized. The review provides insights for future research and public policies aimed at promoting more sustainable and resilient cities. Keywords: Smart and Sustainable Cities. Urban Forests. Information and Communication Technologies. Scoping Review.

Unveiling an intricate relationship: Ficus trees, their associated wasps (Hymenoptera, Chalcidoidea) and another story of invasion in the Iberian Peninsula and Europe

The plant genus Ficus (Moraceae) includes keystone tree species in tropical ecosystems, providing essential resources for a wide range of animals. Due to their ornamental value, fig trees have been introduced beyond their native ranges, often accompanied by their natural pollinators, which in some cases has led to ecological invasions. This study documents, for the first time, the presence of several pollinating and non-pollinating fig wasps (Chalcidoidea) on the Iberian Peninsula, focusing on three exotic Ficus species: Ficus microcarpa L.f., 1782, F. rubiginosa Desf. ex Vent., 1805 and F. macrophylla Pers., 1807. Through syconia sampling and dissection, we identified six fig wasp species: the pollinators Eupristina aff. verticillata (Waterston, 1921) and Pleistodontes imperialis Saunders, 1882, the gall-formers Eufroggattisca okinavensis Ishii, 1934, Josephiella microcarpae Beardsley &amp; Rasplus, 2001, Walkerella microcarpae Bouček, 1993, and the parasitoid Philotrypesis okinavensis Ishii, 1934. Additionally, we documented several cases of non-native Ficus species reproducing spontaneously in urban areas, suggesting a significant ecological establishment and invasive spread through sexual reproduction. This spread poses potential risks to urban infrastructure, as the robust root systems of fig trees can damage buildings, pavements, urban trees, and heritage sites. Finally, we observed urban native and non-native bird species consuming mature fig syconia, which likely assist in the dispersal of these plants. Our findings underscore the need for further studies on the ecological impact of introduced Ficus species in non-native regions, their long-term economic consequences for urban heritage, and the continued monitoring of pollinator fig wasp populations.

Sull’ampliamento del giardino Gulbenkian. Attualità di un manifesto ecologico e poetico

The paper starts from the opening of the new southern part of the Gulbenkian Foundation garden in Lisbon, in order to reflect on the legacy of the Portuguese landscape school, traditionally inclined to mixture. When, between 1959 and 1961, Antonio Viana Barreto and Gonçalo Ribeiro Telles drew up the design assumptions for the new park, they identified the ecological approach and the integration of existing vegetation as the main cornerstones. They also seek a strong visual continuity between the architecture and the outside, firmly renouncing any geometrical axis, preferring the design of space over the form, celebrating the intrinsic beauty of Nature; they created a park that has been called a ‘political flag’ on several occasions. The essay tries to critically analyse the outcomes of the competition announced in 2019 and won by Kengo Kuma (architecture) and Vladimir Djurovic (landscape architecture), who planned a nature garden with the features of an urban forest, integrating existing vegetation with Mediterranean species from Portuguese nurseries. The main topics are biological diversity, and the symbolic charge of several design choices, oriented towards inclusiveness and dialogue of the garden with the surrounding urban complexity.

Urban forest quality corresponds with soil microbial community composition and arbuscular mycorrhizal fungi root colonization

Fairfax County government (Virginia, USA) conducted an extensive survey of urban/suburban forests. Measurements such as tree health, impervious surface, and invasive species was used to calculate a quality index with the iTree tool kit. Building on survey results, our team sampled soils and tree roots in a subset of sites representing a range of forest quality index values. Our goal was to determine if aboveground forest quality correlated to belowground soil biomass, microbial community composition, and mycorrhizal fungal abundance. Soil bacterial/archaeal and fungal communities were quantified (qPCR) and characterized (amplicon sequencing). We observed differences in community composition, but not quantity. Putative functional assignments indicated a decrease in ectomycorrhizal fungi with declining quality and arbuscular mycorrhizal fungal root colonization also decreased. This study demonstrates the crucial above- and belowground connections within urban forests and highlights the need for managers to consider soil biology when assessing ecosystem health.

Modelling above ground biomass for a mixed-tree urban arboretum forest based on a LiDAR-derived canopy height model and field-sampled data

Modelling above ground biomass for a mixed-tree urban arboretum forest based on a LiDAR-derived canopy height model and field-sampled data

An improved hybrid approach involving deep learning for urban greening tree species classification with Pléiades Neo 4 imagery—A case study from Nanjing, Eastern China

An improved hybrid approach involving deep learning for urban greening tree species classification with Pléiades Neo 4 imagery—A case study from Nanjing, Eastern China

Global trends in urban forest irrigation: Environmental influences, challenges and opportunities for sustainable practices across 109 cities worldwide

Global trends in urban forest irrigation: Environmental influences, challenges and opportunities for sustainable practices across 109 cities worldwide

Soil health assessment of urban forests in Nanchang, China: Establishing a minimum data set model

Soil health assessment of urban forests in Nanchang, China: Establishing a minimum data set model

Life cycle cost analysis of urban trees: a case study of five cities in Germany

Life cycle cost analysis of urban trees: a case study of five cities in Germany

Socio-Economic Drivers and Sustainability Challenges of Urban Green Space Distribution in Jinan, China

Urban green spaces (UGSs), including parks, forests, and community gardens, play a critical role in enhancing public health and well-being by providing essential ecosystem services such as improving air quality, reducing surface temperatures, and mitigating harmful substances. As urbanization accelerates, especially in rapidly growing cities like Jinan, China, the demand for UGSs is intensifying, necessitating careful urban planning to balance development and environmental protection. While previous studies have often focused on city-level green coverage, this study shifts the analytical focus from UGS as a whole to urban functional units (UFUs), allowing for a more detailed examination of how green space is distributed across different land use types. We investigate UGS changes in Jinan over the past two decades and assess the influence of socio-economic factors—such as housing prices, land use types, and building age—on UGS distribution within UFUs. Remote sensing technology was employed to analyze the spatiotemporal dynamics of UGS and its correlation with these variables. Our findings reveal a significant shift in UGS distribution, with parks and leisure areas becoming primary drivers of UGS expansion. This study also highlights the growing influence of economic factors, particularly housing prices, on UGS distribution in more affluent UFUs. Additionally, while UGS in Jinan has generally expanded, challenges remain in balancing green space with urban expansion, especially in commercial and residential UFUs. This paper contributes to a more nuanced understanding of UGS distribution by integrating the UFU framework and identifying socio-economic drivers—including housing prices, construction age, and land use type—that shape green space patterns in Jinan. Our findings demonstrate that the spatial pattern of UGS in Jinan mirrors socio-economic and land use disparities observed in other global cities, highlighting both the universality of these patterns and the need for targeted planning in rapidly urbanizing contexts.

Assessing air pollutant removal and carbon sequestration across urban forest stands and individual species in a medium-sized southern Italian city.

Urban areas are characterized by elevated levels of air pollution and carbon emissions resulting from human activities. Addressing these challenges simultaneously is essential for achieving resilient and healthy cities. Given the potential of urban forests to mitigate both air pollution and carbon emissions, this study focused on quantifying these ecosystem services in Monte Sant'Antonio's urban forest, located in Campobasso, Italy. The urban forest's capacity to remove carbon and atmospheric pollutants (O3, SO2, NO2, CO, and PM2.5) was first assessed using i-Tree Eco v.6 software. The results from i-Tree Eco were then compared with estimates we developed using Italian biomass calculation equations from the 2015 National Inventory of Forests and Carbon Sinks. To support this comparison, linear regression models were developed to characterize the relationships between total tree biomass (independent variable) and pollutant removal and carbon sequestration (dependent variables) by individual tree species. The analysis followed a stepwise approach. Subsequently, we assessed temporal variations in air pollutants removal capacity and gross carbon sequestration for the two tree species present in all four stands analyzed: Fraxinus ornus L. and Pinus nigra J.F. Arnold. Based on the estimates derived from applying the models using total tree biomass calculated with Italian equations, the urban forest of Monte Sant'Antonio can remove approximately 1 ton of pollutants per year (CO, O3, NO2, SO2, PM2.5) and approximately 158 tons of gross carbon sequestration per year.