Distinct latitudinal patterns and drivers of topsoil nitrogen and phosphorus across urban forests in eastern China.

Nitrogen (N) and phosphorus (P) are the two most important macronutrients supporting forest growth. Unprecedented urbanization has created growing areas of urban forests that provide key ecosystem services for city dwellers. However, the large-scale patterns of soil N and P content remain poorly understood in urban forests. Based on a systematic soil survey in urban forests from nine large cities across eastern China, we examined the spatial patterns and key drivers of topsoil (0-20 cm) total N content, total P content, and N:P ratio. Topsoil total N content was found to change significantly with latitude in the form of an inverted parabolic curve, while total P content showed an opposite latitudinal pattern. Variance partition analysis indicated that regional-scale patterns of topsoil total N and P contents were dominated by climatic drivers and partially regulated by time and pedogenic drivers. Conditional regression analyses showed a significant increase in topsoil total N content with lower mean annual temperature (MAT) and higher mean annual precipitation (MAP), while topsoil total P content decreased significantly with higher MAP. Topsoil total N content also increased significantly with the age of urban park and varied with pre-urban soil type, while no such effects were found for topsoil total P content. Moreover, topsoil N:P ratio showed a latitudinal pattern similar to that of topsoil total N content and also increased significantly with lower MAT and higher MAP. Our findings demonstrate distinct latitudinal trends of topsoil N and P contents and highlight a dominant role of climatic drivers in shaping the large-scale patterns of topsoil nutrients in urban forests.

An Efficient Convolutional Denoising Autoencoder-Based BDS NLOS Detection Method in Urban Forest Environments.

The BeiDou Navigation Satellite System (BDS) provides real-time absolute location services to users around the world and plays a key role in the rapidly evolving field of autonomous driving. In complex urban environments, the positioning accuracy of BDS often suffers from large deviations due to non-line-of-sight (NLOS) signals. Deep learning (DL) methods have shown strong capabilities in detecting complex and variable NLOS signals. However, these methods still suffer from the following limitations. On the one hand, supervised learning methods require labeled samples for learning, which inevitably encounters the bottleneck of difficulty in constructing databases with a large number of labels. On the other hand, the collected data tend to have varying degrees of noise, leading to low accuracy and poor generalization performance of the detection model, especially when the environment around the receiver changes. In this article, we propose a novel deep neural architecture named convolutional denoising autoencoder network (CDAENet) to detect NLOS in urban forest environments. Specifically, we first design a denoising autoencoder based on unsupervised DL to reduce the long time series signal dimension and extract the deep features of the data. Meanwhile, denoising autoencoders improve the model's robustness in identifying noisy data by introducing a certain amount of noise into the input data. Then, an MLP algorithm is used to identify the non-linearity of the BDS signal. Finally, the performance of the proposed CDAENet model is validated on a real urban forest dataset. The experimental results show that the satellite detection accuracy of our proposed algorithm is more than 95%, which is about an 8% improvement over existing machine-learning-based methods and about 3% improvement over deep-learning-based approaches.

Urban forest species selection for improvement of ecological benefits in Polish cities - The actual and forecast potential.

Trees in cities perform important environmental functions: they produce oxygen, filter pollutants, provide habitat for wildlife, mitigate stormwater runoff, and reduce the effects of climate change, especially in terms of lowering temperatures and converting carbon dioxide from the atmosphere into stored carbon. Generally, to increase the environmental benefits of urban forests, the number of trees is increased, directly influencing the canopy coverage. However, little is known about potential of modifying the species composition of urban tree communities in order to increase ecological benefits. Planting and managing trees to increase canopy is particularly challenging in city centres, where the dense, often historic infrastructure of buildings and roads do not allow for a significant increase in greenspace. Estimations of canopy cover obtained through i-Tree Canopy analysis unveiled significant potential to increase canopy cover in historical urban areas in Polish cities from 15-34% to 31-51%. This study models the ecological benefits of urban forests in Polish cities, focusing on how different species compositions can enhance environmental functions such as carbon sequestration and pollution filtration. Two main scenarios were analyzed: one involving the addition of trees based on the most common species currently planted ("standard option" SO), and another incorporating changes to the species composition to enhance ecological benefits ("city specific option" SCO). Acer platanoides (14.5%) and Tilia cordata (11.45%) were the most frequently species of Polish cities. Betula pendula, Quercus robur, Robinia pseudoacacia, Fraxinus excelsior, Acer pseudoplatanus, Aesculus hippocastanum and Acer campestre were also common species in urban forest communities (up to 5%). The diverse range of tree species in Polish cities contributes significantly to the overall carbon sequestration potential. The results suggest that modifying species composition could significantly increase carbon sequestration rates by 47.8%-114% annually, with the city specific option (SCO) being the most effective in enhancing carbon sequestration potential. This highlights the importance of strategic species selection in urban forestry practices to maximize environmental benefits and mitigate climate change effects.

Effect of urbanization and urban forests on water quality improvement in the Yangtze River Delta: A case study in Hangzhou, China.

In the context of rapid global urbanization, the sustainable development of ecosystems should be considered. Accordingly, the Planetary Boundaries theory posits that reducing the amount of nitrogen and phosphorus pollutants entering bodies of water is necessary as excess levels may harm the aquatic environment and reduce in water quality. Thus, based on the long-term monitoring data of representative urban rivers in the Yangtze River Delta region, we evaluated the nitrogen and phosphorus pollution of water bodies in different urbanization stages and further quantified the effect of urban forests on water quality improvement. The results showed that, with the continuous progression of urbanization, the proportion of impervious surface area increased, along with the levels of nitrogen and phosphorus pollution in water bodies. The critical period of water quality deterioration in urban rivers occurred during the medium urbanization level when the proportion of impervious surface area reached 55-65 %, and the probability of an abrupt increase in total nitrogen (TN) and total phosphorus (TP) concentration exceeded 95 %. However, increasing the area of urban forests during this period reduced TN pollution by 36.64 % and TP pollution by 49.03 %. The results of this study support the expansion of urban forests during the medium urbanization stage to improve water quality. Furthermore, our results provide a reference and theoretical basis for urban forest construction as a key aspect of the sustainable development of the urban ecosystem in the Yangtze River Delta and similar regions around world.

Governance, institutional and economic frameworks for Urban Forests as a Nature-Based Solution in Europe.

Urban forests as nature-based solutions (UF-NbS) play a crucial role for promoting the health and well-being of urban populations. Despite increasing recognition of their importance, knowledge gaps remain regarding UF-NbS implementation, particularly with respect to their performance, their perception, and on decision-making and governance practices for their implementation and management. Grounded in a project-as-practice approach and based on sixteen UF-NbS case histories, this paper seeks to gain insights into UF-NbS project actualities by an identification of characteristic trends as a function of a projects' scope and purpose, or challenge-orientation, respectively. A particular emphasis is on project structure and coordination, on the scope and depth of participation and stakeholder involvement, and on funding mechanisms. Identified trends reveal centrally coordinated, single-responsible public authorities as the most common project structure, but with certain feature contents, i.e., regeneration and reclamation, as being associated with more decentralised forms of governance. It is concluded that irrespective of challenge-orientation, comparatively broad participation appears to be realised within the UF-NbS framework, however, the depth of participation differs considerably. With respect to funding, a strong reliance on public capital is asserted for the UF-NbS context, however, various forms of private contributions appear reasonably common across the assessed case histories. Recommendations for policy-making and avenues of future research are identified, including the validation of identified trends, the fostering of collaboration, the dispersal of decision-making authority, the encouragement for implementing non-tokenistic modes of participation in UF-NbS governance, and the promotion of potentially under-utilised funds.

Characterizing Non-governmental Organizations And Local Government Collaborations In Urban Forest Management Across Canada.

Urban forests are being threatened by rapid urbanization, biodiversity crises, and climate variability. In response, governments are increasingly collaborating with the public for solutions to these mounting challenges. Non-governmental organizations (NGOs) are dominant players in these collaborations because of their ability to supplement governments' expertize and resources and bring social and ecological issues to the forefront of civic agendas. Despite their growing visibility in urban forest management, there is a lack of attention directed to the forms and range of NGO relationships. This study focuses on addressing this gap and examining collaborations between local governments and NGOs in urban forest programming by characterizing their components including mandates, relationship ties, accountability, resource exchange, and power dynamics. We collected data using semi-structured interviews with three groups: leaders of NGOs, municipal government officials in an urban forest or public works departments, and urban-forest experts who have observed their interactions. The participants represent 32 individuals in nine Canadian cities. Our results indicate that NGO-government collaborations have relational ties and accountability processes that are both formal and informal in nature. Formality in collaborations is often associated with the amount of funding, proximity to government, or size of the NGO. In addition, our findings suggest that NGOs present an opportunity for local governments to supplement their resources and capacity. While the strength and formality of collaborations may be a product of NGO size and budgets, public servants should not hesitate to engage smaller, grassroots NGOs to realize their public service mandates. Characterizing the components of these governance processes provides a benchmark for practitioners participating in similar public-civic interactions and arms them with the knowledge to navigate collaborative decision-making.

Urbanization can accelerate climate change by increasing soil N2 O emission while reducing CH4 uptake.

Urban land-use change has the potential to affect local to global biogeochemical carbon (C) and nitrogen (N) cycles and associated greenhouse gas (GHG) fluxes. We conducted a meta-analysis to (1) assess the effects of urbanization-induced land-use conversion on soil nitrous oxide (N2 O) and methane (CH4 ) fluxes, (2) quantify direct N2 O emission factors (EFd ) of fertilized urban soils used, for example, as lawns or forests, and (3) identify the key drivers leading to flux changes associated with urbanization. On average, urbanization increases soil N2 O emissions by 153%, to 3.0 kg N ha-1  year-1 , while rates of soil CH4 uptake are reduced by 50%, to 2.0 kg C ha-1  year-1 . The global mean annual N2 O EFd of fertilized lawns and urban forests is 1.4%, suggesting that urban soils can be regional hotspots of N2 O emissions. On a global basis, conversion of land to urban greenspaces has increased soil N2 O emission by 0.46 Tg N2 O-N year-1 and decreased soil CH4 uptake by 0.58 Tg CH4 -C year-1 . Urbanization driven changes in soil N2 O emission and CH4 uptake are associated with changes in soil properties (bulk density, pH, total N content, and C/N ratio), increased temperature, and management practices, especially fertilizer use. Overall, our meta-analysis shows that urbanization increases soil N2 O emissions and reduces the role of soils as a sink for atmospheric CH4 . These effects can be mitigated by avoiding soil compaction, reducing fertilization of lawns, and by restoring native ecosystems in urban landscapes.

Assessment of street forest characteristics in four African cities using google street view measurement: Potentials and implications.

Accurate information on urban forests of tree sizes, health state, community structures, and spatial distribution is still limited in African cities. Using a Google Street View (GSV)-based tree-size measuring method developed by our team, this paper aims to evaluate street trees of four African metropolitan cities using GSV data. The study compiled a large dataset with 46,016 street trees in 3454 sites in Kampala, Nairobi, Bloemfontein, and Johannesburg. The data including tree size (diameter at breast height, DBH; tree height, TH; underbranch height, UBH; canopy size), tree floristic composition (apical dominance types, broadleaf-conifer-palm leaf, flowering or not), tree health (leaf color, diebacks, dead tree, and bracket-supporting percent), streetside development (lane number, roadside shops, parking vehicle, and pedestrian density), and geolocation (latitude, longitude). These data can be spatially visualized with the help of ArcGIS, and the large dataset favors reliable maps from the street-view level. Data statistics showed that four cities were dominated by broad-leaved, apical dominance, and flowering trees, with a low level of unhealthy leaves and a tiny percentage of dead. The arbor-shrubs-herb structure vegetation dominated all four cities. Kampala had the most slender trees (DBH = 23 cm, TH = 8.4 m), while Nairobi and Johannesburg had the thickest trees (DBH = 38 cm, TH = 8.5-8.6 m). Bare land rates were lowest at 23% in Bloemfontein and highest at 33% in Nairobi. Principal analysis and Pearson correlations showed that these tree variations were closely associated with street development and local land use configuration. By comparing the urban tree data in other regions of the world, we found that the trees in African cities are generally giant but have a lower density (the trees within a 100-m street segment). Our findings emphasized that GSV data is feasible enough for urban forest monitoring in Africa, and the database is helpful for urban landscape planning and management.

The restorative effects of short-term exposure to nature in immersive virtual environments (IVEs) as evidenced by participants' brain activities.

Short-term exposure to nature has excellent potential to be used as a public health intervention measure. Nevertheless, the physiological and psychological mechanisms of this health benefit are still unclear. In this study, we intend to verify the effects of short-term exposure to nature on psychological functioning and to explore the underlying mechanism through experiments conducted in immersive virtual environments (IVEs). Participants were randomly exposed to videos of an urban forest and an indoor environment in IVEs. Before and after the exposure, a participant's self-perceived stress and cognitive performance were measured using the PSS-14 form and the Stroop task, respectively. Their brain activities during the exposure were measured using the electroencephalogram (EEG). The PSS-14 and the Stroop task results confirmed the benefits of stress reduction and cognitive performance improvements from short-term nature exposure. At the same time, rhythmic brain activities during nature exposure indicated better attentional states. The electrodes around the parietal region detected significantly stronger power spectral density of the theta band than other bands. Also, participants showed high functional connectivity among different brain parts during nature exposure, which revealed better cognitive flexibility. The topographic pattern of the differences in functional connectivity overlapped well with the default mode network (DMN)-a "task-negative" network active during the resting state. The overlap indicated a lower cognitive processing load when exposing to nature. Our results support the hypothesis that nature's restorative effects mainly come from effortless processing in natural environments.

Scale-dependent interactions between tree canopy cover and impervious surfaces reduce daytime urban heat during summer.

As cities warm and the need for climate adaptation strategies increases, a more detailed understanding of the cooling effects of land cover across a continuum of spatial scales will be necessary to guide management decisions. We asked how tree canopy cover and impervious surface cover interact to influence daytime and nighttime summer air temperature, and how effects vary with the spatial scale at which land-cover data are analyzed (10-, 30-, 60-, and 90-m radii). A bicycle-mounted measurement system was used to sample air temperature every 5 m along 10 transects (∼7 km length, sampled 3-12 times each) spanning a range of impervious and tree canopy cover (0-100%, each) in a midsized city in the Upper Midwest United States. Variability in daytime air temperature within the urban landscape averaged 3.5 °C (range, 1.1-5.7 °C). Temperature decreased nonlinearly with increasing canopy cover, with the greatest cooling when canopy cover exceeded 40%. The magnitude of daytime cooling also increased with spatial scale and was greatest at the size of a typical city block (60-90 m). Daytime air temperature increased linearly with increasing impervious cover, but the magnitude of warming was less than the cooling associated with increased canopy cover. Variation in nighttime air temperature averaged 2.1 °C (range, 1.2-3.0 °C), and temperature increased with impervious surface. Effects of canopy were limited at night; thus, reduction of impervious surfaces remains critical for reducing nighttime urban heat. Results suggest strategies for managing urban land-cover patterns to enhance resilience of cities to climate warming.

Urban Forest Health Intervention Program to promote physical activity, healthy eating, self-efficacy and life satisfaction: impact on Israeli at-risk youth.

The aim of this study was to evaluate an urban forest intervention program effect on physical activity, healthy eating habits, self-efficacy and life satisfaction (LS) among Israeli at-risk youth. The quasi-experimental study ran from September 2016 to June 2017; participants were randomly selected. There were 76 total study participants: 53 in the intervention and 23 in the control group. Participants ranged in age from 15 to 18 years. Questionnaires were administered to intervention and control groups before and after the intervention. Univariate and multivariable analyses evaluated the intervention effect. Repeated measures analyses of covariance were calculated to assess change in group differences. An increase was found in measures of physical activity in the intervention group (p < 0.001), while no change was noted in the control group. Healthy eating increased in both groups (p = 0.007), with no significant difference between them (p = 0.165). Unhealthy eating decreased significantly in the intervention group (p = 0.002) and increased in the control group (p = 0.007). Self-efficacy increased in the intervention group (p < 0.001), while no change was noted in the control group (p = 0.353). Likewise, LS increased in the intervention group (p < 0.001), while no change was found in the control group (p = 0.657). Findings indicate that the intervention was efficacious in increasing physical activity, healthy eating habits, self-efficacy, and LS. The effectiveness of this intervention among larger samples is warranted in future prospective studies.

Historical Urban Tree Canopy Cover Change in Two Post-Industrial Cities.

Present-day spatial patterns of urban tree canopy (UTC) are created by complex interactions between various human and biophysical drivers; thus, urban forests represent legacies of past processes. Understanding these legacies can inform municipal tree planting and canopy cover goals while also addressing urban sustainability and inequity. We examined historical UTC cover patterns and the processes that formed them in the cities of Chelsea and Holyoke, Massachusetts using a mixed methods approach. Combining assessments of delineated UTC from aerial photos with historical archival data, we show how biophysical factors and cycles of governance and urban development and decay have influenced the spatiotemporal dynamics of UTC. The spatially explicit UTC layers generated from this research track historical geographic tree distribution and dynamic change over a 62-year period (1952-2014). An inverse relationship was found between UTC and economic prosperity: while canopy gains occurred in depressed economic periods, canopy losses occurred in strong economic periods. A sustainable increase of UTC is needed to offset ongoing losses and overcome historical legacies that have suppressed UTC across decades. These findings will inform future research on residential canopy formation and stability, but most importantly, they reveal how historical drivers can be used to inform multi-decadal UTC assessments and the creation of targeted, feasible UTC goals at neighborhood and city scales. Such analyses can help urban natural resource managers to better understand how to protect and expand their cities' UTC over time for the benefit of all who live in and among the shade of urban forests.

Ecosystem functions of fruit woody species in an urban environment.

The objective of this work was to investigate the potential ecosystem services of 16 fruit trees to plan and manage more efficiently "Urban Forest," increasing also the resilience of cities to climate change. We evaluated the potential capacity of PM10 absorption, the storage of CO2 from the atmosphere, and the cooling of the environment through shading by the crown and through evapotranspiration. We observed that some species, such as Morus nigra, Juglans regia, Pyrus communis, and Cydonia oblonga, are able to store a higher quantity of CO2 than others over a period of 50 years, respectively, of 2.40 tons, 2.33 tons, 1.51 tons, and 0.96 tons. Ficus carica, Juglans regia, and Morus nigra were relevant for PM10 absorption, since they were able to absorb, referring to the year 2019, 146.4 gr/tree, 195.6 gr/tree, and 143.1 gr/tree, respectively. Results showed that these ecosystem functions depend principally on the morphological characteristics of the individuals: their height, DBH, expansion of their crowns, and characteristics of the foliage system.

A trait-based typification of urban forests as nature-based solutions.

Urban forests as nature-based solutions (UF-NBS) are important tools for climate change adaptation and sustainable development. However, achieving both effective and sustainable UF-NBS solutions requires diverse knowledge. This includes knowledge on UF-NBS implementation, on the assessment of their environmental impacts in diverse spatial contexts, and on their management for the long-term safeguarding of delivered benefits. A successful integration of such bodies of knowledge demands a systematic understanding of UF-NBS. To achieve such an understanding, this paper presents a conceptual UF-NBS model obtained through a semantic, trait-based modelling approach. This conceptual model is subsequently implemented as an extendible, re-usable and interoperable ontology. In so doing, a formal, trait-based vocabulary on UF-NBS is created, that allows expressing spatial, morphological, physical, functional, and institutional UF-NBS properties for their typification and a subsequent integration of further knowledge and data. Thereby, ways forward are opened for a more systematic UF-NBS impact assessment, management, and decision-making.

Green spaces, quality of life, and citizen perception in European cities.

Urban green spaces generate a number of perceived benefits toward human health and well-being, including an overall improvement in the quality of life. To date, processes underlying these benefits are mostly investigated at city level, while very little research has been conducted at a larger scale, such as the European level. Evidence is lacking on the association between green spaces and citizens' perceived benefits based on variations among cities with different socio-economic conditions. This study aims to disentangle the relationship between greenness, citizens' perceived quality of life, the environment, social inclusion and urban management in 51 European cities, as well as the role of per capita income in moderating the effects of greenness on overall perceived quality of life. Through structural equation modeling, the effect of greenness was tested on citizens' perceived overall quality of life (i.e., on the environment, social inclusion, and urban management). The role of metropolitan gross domestic product per capita in moderating the relationship between greenness and citizens' perceptions on overall quality of life was investigated. Our findings confirm the influence of greenness on citizens' quality of life. More importantly, the influence of greenness on the overall perception of quality of life was considerably more marked in lower-income cities. This study represents one of the first attempts at exploring the complex mechanisms underlying the association between green space and citizens' well-being at continent level. Practical implications for European urban planners and policy makers are discussed.

International approaches to protecting and retaining trees on private urban land.

Most studies of urban forest management look at vegetation on public land. Yet, to meet ambitious urban forest targets, cities must attempt to maintain or increase trees and canopy cover on private urban land too. In this study, we review and evaluate international approaches to protecting and retaining trees on private urban land. Our study combines a systematic academic literature review, two empirical social science studies on the views of urban forest professionals, and a global case study review of innovative regulations and incentives aimed at protecting and retaining trees on private urban land. Case studies were evaluated for the extent they exceeded minimum standards or went beyond 'business-as-usual'. We found that the most innovative mechanisms combine many regulations, instead of relying on a single regulation, and use financial incentives to retain or plant trees in newly developed or re-developed sites, as well as private residences. We did not find any cases where appropriate monitoring was in place to determine the efficacy and efficiency of these mechanisms. We also found no single simple solution that could effectively and efficiently protect and retain trees on private land. Only by combining policies, planning schemes, local laws, and financial incentives with community engagement and stewardship will cities protect and retain trees on private land. Useful and innovative ways to protecting and retaining trees on private land involves providing solutions at multiple governments levels, embedding trees in existing strategic policy and management solutions, incentivising positive behavior, creating regulations that require payment up front, and engaging the broader community in private tree stewardship.

The importance of street trees to urban avifauna.

Street trees are public resources planted in a municipality's right-of-way and are a considerable component of urban forests throughout the world. Street trees provide numerous benefits to people. However, many metropolitan areas have a poor understanding of the value of street trees to wildlife, which presents a gap in our knowledge of conservation in urban ecosystems. Greater Los Angeles (LA) is a global city harboring one of the most diverse and extensive urban forests on the planet. The vast majority of the urban forest is nonnative in geographic origin, planted throughout LA following the influx of irrigated water in the early 1900s. In addition to its extensive urban forest, LA is home to a high diversity of birds, which utilize the metropolis throughout the annual cycle. The cover of the urban forest, and likely street trees, varies dramatically across a socioeconomic gradient. However, it is unknown how this variability influences avian communities. To understand the importance of street trees to urban avifauna, we documented foraging behavior by birds on native and nonnative street trees across a socioeconomic gradient throughout LA. Affluent communities harbored a unique composition of street trees, including denser and larger trees than lower-income communities, which in turn, attracted nearly five times the density of feeding birds. Foraging birds strongly preferred two native street-tree species as feeding substrates, the coast live oak (Quercus agrifolia) and the California sycamore (Platanus racemosa), and a handful of nonnative tree species, including the Chinese elm (Ulmus parvifolia), the carrotwood (Cupaniopsis anacardioides), and the southern live oak (Quercus virginiana), in greater proportion than their availability throughout the cityscape (two to three times their availability). Eighty-three percent of street-tree species (n = 108, total) were used in a lower proportion than their availability by feeding birds, and nearly all were nonnative in origin. Our findings highlight the positive influence of street trees on urban avifauna. In particular, our results suggest that improved street-tree management in lower-income communities would likely positively benefit birds. Further, our study provides support for the high value of native street-tree species and select nonnative species as important habitat for feeding birds.

Vulnerability of Common Urban Forest Species to Projected Climate Change and Practitioners Perceptions and Responses.

While urban forests are often identified as part of climate change adaptation and mitigation strategies, less attention has been given to vulnerabilities urban trees may have to a changing climate and practitioners' response to those vulnerabilities. Yet, current planting and management decisions will impact how urban forests fare under future climatic conditions. We explore a case study of Mississauga (Ontario, Canada) to examine (1) if common urban forest species are vulnerable to two scenarios of projected climate change, (2) the experiences and responses of urban forestry practitioners to climate change, and (3) whether urban forestry practitioners' experience and practice are aligned with the vulnerability assessment. Vulnerabilities of 27 common species were examined based on 2071-2100 regional climate projections. Interviews were then conducted with practitioners working in the public and private sectors. The results suggest that the majority of examined species will be vulnerable to multiple conditions associated with projected climate. Practitioners all perceive recent changes in climate and extreme weather patterns, but do not prioritize future climate conditions in their species selection decisions. Moreover, they expressed uncertainty about how to make species selection decisions in light of climate change. Given the predicted vulnerabilities, alternative species need to be considered or more management resources (e.g., for watering) will be required to maintain the current composition. However, the lack of focus on future conditions by practitioners raises concerns, while also highlighting the need for more information about appropriate management strategies.

Source identification and pollution degree of deposited dust on green space in Tehran.

The information about concentration, sources, and pollution degree of heavy metals belong to deposited dust (DS) can be used for decision-making in air quality control, removal role of green space, and urban forest management. The objectives of the study were to identify and evaluate DS pollution degree with the introduction of a new index. DS samples were collected from five tree species. The concentration of heavy metals and pollution degree of DS were evaluated by enrichment factors (EF), geoaccumulation index (Igeo), modified degrees of contamination (mCd), and a new comprehensive index as weighted degree of contamination factor (wCd). The values of EF showed that all samples were significant to extremely high enrichment and DS samples were emitted from anthropogenic activities. Igeo values indicated that DS samples were polluted by Cd (80-97%) and Pb (100%). In addition, mCd results showed more than 67% of samples were unpolluted. There was a clear fact that Igeo results showed high pollution levels for Pb, Cd, and low for Ni, and the mCd results were incompatible with them. When all heavy metals were used without their importance to mCd, calculation can cause bias from reality. For this reason, the new index was suggested as wCd for all heavy metals that its results showed high to very high degree of pollution and that it was compatible with other indices results.

A city-scale assessment reveals that native forest types and overstory species dominate New York City forests.

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.