Trees In Cities Research Articles

Cooling cities through urban green infrastructure: a health impact assessment of European cities

High ambient temperatures are associated with many health effects, including premature mortality. The combination of global warming due to climate change and the expansion of the global built environment mean that the intensification of urban heat islands (UHIs) is expected, accompanied by adverse effects on population health. Urban green infrastructure can reduce local temperatures. We aimed to estimate the mortality burden that could be attributed to UHIs and the mortality burden that would be prevented by increasing urban tree coverage in 93 European cities. We did a quantitative health impact assessment for summer (June 1-Aug 31), 2015, of the effect of UHIs on all-cause mortality for adults aged 20 years or older in 93 European cities. We also estimated the temperature reductions that would result from increasing tree coverage to 30% for each city and estimated the number of deaths that could be potentially prevented as a result. We did all analyses at a high-resolution grid-cell level (250 × 250 m). We propagated uncertainties in input analyses by using Monte Carlo simulations to obtain point estimates and 95% CIs. We also did sensitivity analyses to test the robustness of our estimates. The population-weighted mean city temperature increase due to UHI effects was 1·5°C (SD 0·5; range 0·5-3·0). Overall, 6700 (95% CI 5254-8162) premature deaths could be attributable to the effects of UHIs (corresponding to around 4·33% [95% CI 3·37-5·28] of all summer deaths). We estimated that increasing tree coverage to 30% would cool cities by a mean of 0·4°C (SD 0·2; range 0·0-1·3). We also estimated that 2644 (95% CI 2444-2824) premature deaths could be prevented by increasing city tree coverage to 30%, corresponding to 1·84% (1·69-1·97) of all summer deaths. Our results showed the deleterious effects of UHIs on mortality and highlighted the health benefits of increasing tree coverage to cool urban environments, which would also result in more sustainable and climate-resilient cities. GoGreenRoutes, Spanish Ministry of Science and Innovation, Institute for Global Health, UK Medical Research Council, European Union's Horizon 2020 Project Exhaustion.

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.

Allometries of Acer negundo for a better space management in two cities of northeastern Greece

Abstract The ability to estimate the space volume that a tree occupies, in various heights, is a crucial factor in designing the street trees schedule in pavements of new urban infrastructures. The dimensions of Acer negundo tree crown in various heights can be the basis for a better space management in the pavements of cities. In this study, the height and the crown width of the A. negundo street trees in the Greek cities of Orestiada and Alexandroupoli and the allometric relations that can be found between them, were investigated. Data from 117 street trees growing in semi-permeable pavements of the two cities were used. In each selected tree, the total height (H), and the maximum and minimum crown diameter (CW) were measured. The selected model (CW-H) for Alexandroupoli exhibits a coefficient of determination (R2) of 0.81. The R2 of the model selected for Orestiada is lower (R2 = 0.66). The R2 of the model selected using the complete dataset is 0.77. A. negundo appears to have greater crown width in Alexandroupoli compared to that of Orestiada. In Orestiada the conditions of growth were variable since in many cases the measured trees were under side shade, while this not the case in the corresponding trees in Alexandroupoli. The better fit of the selected model in Alexandroupoli compared to that of Orestiada is probably due to the more variable growth conditions of Orestiada.

Effect of the urban matrix on flower-visiting bees (Hymenoptera: Apoidea) and the pollination of city trees in Bogotá, Colombia

Aunque la urbanización es uno de los mayores impulsores de transformación ecológica a nivel global, su impacto sobre la biodiversidad y procesos ecosistémicos como la polinización ha sido poco estudiado, especialmente en el trópico. La polinización es crucial porque determina el éxito reproductivo de muchas plantas silvestres, y provee frutos y semillas para muchos animales y para el consumo humano. Las abejas constituyen uno de los grupos más importantes de animales polinizadores, y se sabe que ensambles diversos de especies nativas pueden proveer servicios de mayor calidad. El objetivo del presente estudio fue evaluar el efecto de la matriz urbana sobre las interacciones de polinización de abejas silvestres y dos especies modelo de árboles urbanos en Bogotá, Colombia. Se registraron la producción de frutos y las tasas de visitas florales de distintos grupos de abejas en 36 árboles de Tecoma stans (L.) Juss. ex Kunth y 35 árboles de Pittosporum undulatum Vent. repartidos en cuatro áreas estratégicas de la Estructura Ecológica Principal de la ciudad. Utilizando análisis de varianza, se encontraron diferencias significativas en la representatividad de distintos taxones de abejas entre fragmentos verdes y la matriz urbana circundante. La especie exótica Apis mellifera Linnaeus demostró gran resiliencia a los espacios más urbanizados, en donde las visitas de Thygater aethiops Smith y Bombus Latreille tendieron a disminuir. No se encontraron diferencias en la producción de frutos entre los fragmentos verdes y la matriz urbana, ni hubo correlación significativa entre esta variable y las tasas de visitas florales.

Comparison of visual risk assessment methods applied in street trees of Montevideo city, Uruguay

Risk assessment of urban trees is an incipient practice in Latin America, generally performed with foreign methods, due to the lack of qualified personnel and locally validated or adapted methodology. This article evaluates the application of three methods on street trees in Montevideo city, Uruguay: Tree Hazard Risk Evaluation and Treatment System (THREATS), Quantified Tree Risk Assessment (QTRA) and Best Management Practices - Tree Risk Assessment (ISA BMP). Three assessors with similar experience applied three methods in 36 trees of three widely used genera, totaling 324 assessments and 1,296 data. The methods were decomposed into the components: Likelihood of Failure, Likelihood of Impact, Consequence and Risk Rating. The data were statistically analyzed through a generalized linear mixed model (p<0.05), for the factors: assessor, method, genus, and their interactions. Results showed no significant differences among assessors, but there were differences among methods, specifically for the Likelihood of Impact and Risk Rating components. The ISA BMP method presented higher means in these last two components. Still, this method is suggested for street trees in Montevideo until a more appropriate method is adapted or developed for local conditions. Highlights No significant differences were found among assessors, which encourages standard training for all assessors. The ISA BMP method presented the highest results for the likelihood of impact and risk rating. Target occupation rate influenced differences among genera found for the likelihood of impact component. The ISA BMP method is suggested for street trees risk assessment in Montevideo, until a method is adapted or developed. The absence of descriptors and categorizations, as well as the application time, need to be improved.

Species clustering, climate effects, and introduced species in 5 million city trees across 63 US cities.

Sustainable cities depend on urban forests. City trees-pillars of urban forests-improve our health, clean the air, store CO2, and cool local temperatures. Comparatively less is known about city tree communities as ecosystems, particularly regarding spatial composition, species diversity, tree health, and the abundance of introduced species. Here, we assembled and standardized a new dataset of N = 5,660,237 trees from 63 of the largest US cities with detailed information on location, health, species, and whether a species is introduced or naturally occurring (i.e., "native"). We further designed new tools to analyze spatial clustering and the abundance of introduced species. We show that trees significantly cluster by species in 98% of cities, potentially increasing pest vulnerability (even in species-diverse cities). Further, introduced species significantly homogenize tree communities across cities, while naturally occurring trees (i.e., "native" trees) comprise 0.51-87.4% (median = 45.6%) of city tree populations. Introduced species are more common in drier cities, and climate also shapes tree species diversity across urban forests. Parks have greater tree species diversity than urban settings. Compared to past work which focused on canopy cover and species richness, we show the importance of analyzing spatial composition and introduced species in urban ecosystems (and we develop new tools and datasets to do so). Future work could analyze city trees alongside sociodemographic variables or bird, insect, and plant diversity (e.g., from citizen-science initiatives). With these tools, we may evaluate existing city trees in new, nuanced ways and design future plantings to maximize resistance to pests and climate change. We depend on city trees.

Erythrina stem borer moth in California - New taxonomic status and implications for control of this emerging pest.

During the last 10 years, the Erythrina stem borer moth, Terastia meticulosalis, emerged as a pest of cultivated coral trees (Erythrina spp.) in California. Erythrina trees are valued for their moderate drought resistance and beautiful flame-like flowers. They are beloved enough to be considered Los Angeles's official "City Tree." Thus, they are a valuable horticultural crop and are grown by many nurseries and occur throughout the landscape in coastal southern California. Coral trees have been heavily affected by T. meticulosalis recently. Using whole genome sequencing techniques, we analysed the origins of this and other infestations of Erythrina in coastal areas and found that they have likely originated from the repeated expansions of the native range of the species in Arizona, a process possibly driven by climatic factors and/or movement of plants by humans. We also found sufficient genetic differences between the western population of the moth and the rest of the New World populations to describe a new western subspecies, T. meticulosalis occidentalis Sourakov & Grishin ssp. n. (type locality USA: CA, San Diego Co., La Jolla). These findings are of economic importance for future attempts to control the moth's impact on activities surrounding the horticultural use of Erythrina spp. by the Californian landscape and nursery industries.

Native pedunculate oaks support more biodiversity than non-native oaks, but non-native oaks are healthier than native oaks: A study on street and park trees of a city

Trees in cities provide multiple ecosystem services. However, simultaneously ensuring healthy trees with high habitat diversity can be challenging in a harsh urban environment. We compared health, microhabitats, and bat activities between native (Quercus robur L.) and non-native (Quercus rubra L.) oaks growing in different urban habitats (street vs. park) in Karlsruhe, southwestern Germany. We randomly selected 167 oak trees with a diameter at breast height (DBH) >20 cm across the city from Urban Tree Registrar. We performed tree health assessment, dendrometric, and microhabitat inventory. We recorded the four-day bat activities on 45 native and non-native oaks with acoustic loggers installed on the trees. We found that non-native oaks were healthier than native oaks but provided less abundance and richness of microhabitats. Tree size (positive effect) and pruning (negative effect) strongly influence microhabitat richness and abundance. In addition, park trees hosted significantly more microhabitats than street trees. We recorded the activities of 9 bat species from 4 genera. Pipistrellus bats were more active in park trees than street trees. Long-eared bats (Plecotus) were more active near the native than non-native oaks. Bats are likely favored by microhabitats such as fork split, lightning scar, and woodpecker “flute” that are more common in less healthy trees. We conclude that non-native red oak can be planted alongside streets, where the conditions are harsher than in parks to better adapt to climatic changes and stay healthy with less maintenance. The preservation of native pedunculate oak trees, especially within parks, is paramount for urban biodiversity conservation because of their potential to provide microhabitats and supporting bats.

A socio-ecological approach to align tree stewardship programs with public health benefits in marginalized neighborhoods in Los Angeles, USA

Extreme heat in the United States is a leading cause of weather-related deaths, disproportionately affecting low-income communities of color who tend to live in substandard housing with limited indoor cooling and fewer trees. Trees in cities have been documented to improve public health in many ways and provide climate regulating ecosystem services via shading, absorbing, and transpiring heat, measurably reducing heat-related illnesses and deaths. Advancing “urban forest equity” by planting trees in marginalized neighborhoods is acknowledged as a climate health equity strategy. But information is lacking about the efficacy of tree planting programs in advancing urban forest equity and public wellbeing. There is a need for frameworks to address the mismatch between policy goals, governance, resources, and community desires on how to green marginalized neighborhoods for public health improvement—especially in water-scarce environments. Prior studies have used environmental management-based approaches to evaluate planting programs, but few have focused on equity and health outcomes. We adapted a theory-based, multi-dimensional socio-ecological systems (SES) framework regularly used in the public health field to evaluate the Tree Ambassador, orPromotor Forestal, program in Los Angeles, US. The program is modeled after the community health worker model—where frontline health workers are trusted community members. It aims to address urban forest equity and wellbeing by training, supporting, and compensating residents to organize their communities. We use focus groups, surveys, and ethnographic methods to develop our SES model of community-based tree stewardship. The model elucidates how interacting dimensions—from individual to society level—drive urban forest equity and related public health outcomes. We then present an alternative framework, adding temporal and spatial factors to these dimensions. Evaluation results and our SES model highlight drivers aiding or hindering program trainees in organizing communities, including access to properties, perceptions about irrigation responsibilities, and lack of trust in local government. We also find that as trainee experience increases, measures including self- and collective efficacy and trust in their neighbors increase. Findings can inform urban forestry policy, planning, and management actions at the government and non-profit levels that aim to increase tree cover and reduce heat exposure in marginalized communities.

Improvements to airborne laser scanning data filtering in sandstone landscapes

Sandstone rock outcrops form a unique part of the landscape of Central Europe. Due to climate conditions, they are mostly covered by dense vegetation. With some limitations, laser scanning technology allows the ground to be captured even under the tree canopy, making it a powerful tool for mapping vegetated and inaccessible terrain. A challenge in deriving a digital terrain model from an acquired point cloud lies in filtering, i.e., discrimination between ground and non-ground points. Conventional filtering methods applied on complex high-energy terrain with formations resembling man-made objects, e.g., rock walls, do not provide satisfactory results with respect to the accuracy of point assignment to ground and non-ground classes and consequently terrain modelling. However, the quality of digital terrain models is critical for geomorphometric applications and recognition of spatial patterns. This study proposes three filtering methods adapted to various morphological conditions of sandstone landscape regions i.e., spatially conditioned filtering, object-oriented classification, and filtering with additional terrain data. Spatially conditioned filtering is based on a well-known method of triangulated irregular network densification, but it adjusts selected parameters in an iterative way. This has been proven to be successful in filtering sandstone rocks by the application of distinct sets of parameters to areas with and without rock formations. Object-oriented classification distinguishes between rock pillars and trees in rock cities based on features describing the distribution of points inside these objects. The method achieved an overall accuracy of 85 % with respect to manually filtered data and outperformed the conventional methods. Filtering with additional terrain data requires already filtered and co-registered references for spatial querying. Evaluation by GNSS measurements showed that the digital terrain model derived using this method achieved a higher accuracy than that derived by conventional methods.

Spatial Distribution and Driving Factors of Old and Notable Trees in a Fast-Developing City, Northeast China

As a symbol of urban civilization and history, old and notable trees (ONTs) are facing challenges brought by rapid urbanization. Changchun is the fastest growing city in Northeast China, and throughout its development process of over 100 years it has preserved many ONTs. This study investigated all the ONTs in Changchun, and analyzed the species diversity, spatial distribution characteristics, dimension, age, and health status of trees by using ecological index and mathematical statistics, and trying to find out the underlying factors regulating their distribution. The results showed that there were 773 old trees belonging to 25 species and 2 notable trees from 1 species in Changchun. Pyrus ussuriensis was the dominant species, followed by Salix matsudana and Ulmus pumila. The urban area, population density, greening rate, and construction history did not influence the species and quantity of ONTs, while the types of land use and tree protection planning were important factors affecting the richness, diversity, and growth conditions of trees. To explore the potential reasons for their existence, the ONTs’ data in Changchun was compared with two nearby cities—Harbin and Shenyang. The comparison indicated that the geographical location and climatic conditions also controlled the distribution of ONTs. The number and dimensions of trees were driven by the history and development process of the city. Our findings suggested that preserving favorable living environments and maintaining a low intensity of human disturbance are critical factors for the survival of ONTs in cities.

Curartistry: Curating Everyday Artistry in Bangkok

How can architecture be taught internationally, beyond the neocolonialist tendency of European-based international exchange programs? Curartistry, a method of curating everyday artistry in Bangkok, is used to achieve bilateral exchanges in art and architectural education between teachers and students of different nationalities. We offer interpretations of late-nineteenth-century and post-war ideas of “everyday life,” based especially on Charles Baudelaire’s “The Painter of Modern Life,” Henry Lefebvre’s “Critique of Everyday Life,” Maurice Blanchot and Susan Hanson’s “Everyday Speech,” and Walter Benjamin’s “On Some Motifs in Baudelaire.” Their ideas grew out of their experiences in Western European metropolises, and continue to reflect similar conditions in twenty-first-century Bangkok. In addition to these literary works, Henry W. Lawrence’s City Trees: A Historical Geography from the Renaissance through the Nineteenth Century has been useful in the development of our workshop entitled, “Curartistry: Trees in Bangkok.” 
 Curartistry is a practice in which particular elements of a city are researched and recorded in drawing and photography. We invite students to visit overlooked sites, landscapes, and trees in Bangkok, and then to write and rewrite until a particular object or installation emerges from redrafting their experiences. These records lead to the proposal of projects, whether artistically, architecturally or otherwise crafted. Once a proposal takes on the form of a project, its existence as a project, rather than as a finished artwork or artefact, is what lends the project criteria for judging it. Outcomes from these projects typically take the form of an elementary installation or exhibition, presented by individual students to guest critics. 
 In this article, we discuss the processes of work, and how everyday artistry in Bangkok is curated in relation to the selected ideas of “everyday life” that transcend time and place, as well as the construction of our method of work. Curartistry is a key way in which we are addressing fundamental issues of city life such as social inequality, nature, ecological crises, labour, and materiality. The final outcomes often address a number of issues, such as the intense relationship between nature and city, dramatic effects in light and colour, transplantation, or tree names in relation to Thai beliefs in fortune. It is hoped that this attempt to systematically document the subjective experiences of urban life will be read as a contribution to global architectural education.

Not All Greenness Is the Same: Associations with Health Are More Nuanced than We Thought.

Not All Greenness Is the Same: Associations with Health Are More Nuanced than We Thought.

Public satisfaction with urban trees and their management in Australia: The roles of values, beliefs, knowledge, and trust

The success of urban forest management strategies is dependent on public support for and engagement with urban trees. Satisfaction with urban trees and their management, and the level of trust people have in urban tree managers, are useful for understanding public opinions. Yet these concepts, and the mechanisms leading to the formation of public opinions remain poorly explored in the literature. Here we explore how satisfaction with urban trees and with urban tree management, and trust in the agencies responsible for urban tree management, are explained by cognitive factors (values, beliefs, and knowledge) and socio-ecological contextual factors (tree presence/canopy cover, cultural diversity, and socioeconomic status) using an online survey of 16 local government areas in south-eastern Australia. Analyses of 2367 responses revealed that people’s opinions about trees in general (values and beliefs) were overwhelmingly positive, while their opinions about more contextualised measures such as satisfaction and trust were more mixed. Two distinct pathways that influence satisfaction were identified: one linked to beliefs about having trees in cities, and another one linked to trust in urban tree management. At the local government level, satisfaction was negatively associated with a measure of cultural diversity and very low levels of tree canopy cover, but not with socioeconomic disadvantage. Satisfaction with local trees could be improved by increasing the quality of ecological function of trees, such as habitat provision and tree diversity. Community engagement could also improve satisfaction and trust, particularly perceived procedural fairness of decision-making, reinforce positive beliefs about the outcomes of having trees in cities, and dispel negative beliefs. Engagement processes should recognise that people hold complex and diverse opinions about urban trees, and by incorporating these opinions into decision-making we can meet the increasingly complex and diverse expectations being placed on urban forests.

Conifers May Ameliorate Urban Heat Waves Better Than Broadleaf Trees: Evidence from Vancouver, Canada

Anthropogenic greenhouse gas emissions are increasing the frequency of deadly heat waves. Heat waves are particularly devastating in cities, where air pollution is high and air temperatures are already inflated by the heat island effect. Determining how cities can ameliorate extreme summer temperature is thus critical to climate adaptation. Tree planting has been proposed to ameliorate urban temperatures, but its effectiveness, particularly of coniferous trees in temperate climates, has not been established. Here, we use remote sensing data (Landsat 8), high-resolution land cover data, and Bayesian models to understand how different tree and land cover classes affect summer surface temperature in Metro Vancouver, Canada. Although areas dominated by coniferous trees exhibited the lowest albedo (95% CrI 0.08–0.08), they were significantly (12.2 °C) cooler than areas dominated by buildings. Indeed, we found that for conifers, lower albedo was associated with lower surface temperatures. Planting and maintaining coniferous trees in cities may not only sequester CO2 to mitigate global climate change, but may also ameliorate higher temperatures and deadly heat waves locally.

Effects of heat and drought stress on the health status of six urban street tree species in Leipzig, Germany

Trees are one of the most important elements of green infrastructure in cities. Climate change is specifically affecting trees in many European cities. Trees are experiencing negative impacts from the increase in heat waves and droughts, both of which begin, in some cases, early in the year and continue through the growing season. Current studies on the regionalization of climate change indicate that important water reservoirs such as soil and tree canopies have been drying out for years/decades, and these impacts can be observed in various parts of Europe. Trees react to stress as they age through mechanisms such as crown defoliation, early wilting, shedding of branches and, ultimately, lowered resistance to pests. As a result, massive tree death, both in park trees and street trees, can be observed in many cities. The present study provides a current inventory of street tree damage caused by heat and drought in the city of Leipzig, Germany, in 2020, the third extreme dry year after 2018 and 2019. The field maps focus on different age groups of Quercus, Tilia, Aesculus, Platanus, Fraxinus and Acer along a periurban-urban gradient. The results are clear: significant damage was found in all tree species. Older trees and newly planted trees are most likely to die as a result of extreme conditions, while younger trees with narrow trunks and crowns that have not yet expanded cope better with both heat and drought. Four out of five mapped street trees showed recognizable damage, indicating severe impacts of climate change on important elements of green infrastructure in cities.

Urban Trees in the Arctic City: Case of Nadym

Trees in Arctic cities perform not only important provisional and regulating ecosystem services, but also bring predominantly settler population closer to the visual images and household standards of their home southern regions. However, maintenance of green infrastructure in the Arctic has specific difficulties associated with the harsh climatic and environmental conditions. This paper focuses on state and dynamics of vegetation in the city of Nadym, Russia, with a particular focus on native and introduced trees as the main ecosystem service providers and an articulation of local values towards green spaces. The research is based on interdisciplinary approach which includes interviews with local residents, geobotanical survey and analysis of remote sensing data. The results of the study show that maintaining of natural vegetation requires specific measures due to environmental the critical impact of anthropogenic activity. The active introduction of plants from more southern regions is manifested both in the deliberate practice of landscaping the city’s streets and courtyards, and in spontaneous attempts to introduce plants from more southern (not Subarctic) agricultural regions of Russia, which are privately brought by city residents from other regions.

Assessing climate risk to support urban forests in a changing climate

Societal Impact StatementGlobally, cities are planning for resilience through urban greening initiatives as governments understand the importance of urban forests in improving quality of life and mitigating climate change. However, the persistence of urban forests and the ecosystem benefits they provide are threatened by climate change, and systematic assessments of causes of tree dieback and mortality in urban environments are rare. Long‐term monitoring studies and adaptive management are needed to identify and prevent climate change‐driven failures and mortality. Research and monitoring when coupled with systematic forecasting will enable governments to incorporate climate change resilience into urban forestry planning. Future scenarios in which urban forests are resilient or in decline will depend on the management and planning actions we make today.SummaryThe management of urban forests is a key element of resilience planning in cities across the globe. Urban forests provide ecosystem services as well as other nature‐based solutions to 4.2 billion people living in cities. However, to continue to do so effectively, urban forests need to be able to thrive in an increasingly changing climate. Trees in cities are vulnerable to extreme heat and drought events, which are predicted to increase in frequency and severity under climate change. Knowledge of species' vulnerability to climate change, therefore, is crucial to ensure provision of desired ecosystem benefits, improve species selection, maintain tree growth and reduce tree mortality, dieback and stress in urban forests. Yet, systematic assessments of causes of tree dieback and mortality in urban environments are rare. We reviewed the state of knowledge of tree mortality in urban forests globally, finding very few frameworks that enable detection of climate change impacts on urban forests and no long‐term studies assessing climate change as a direct driver of urban tree dieback and mortality. The effects of climate change on urban forests remain poorly understood and quantified, constraining the ability of governments to incorporate climate change resilience into urban forestry planning.

An Estimation of Oxygen Release from Green Surfaces in Durres City

Due to urbanization trend in Durres city, distance between city inhabitants and nature is increasing. Urban greenery is one of the methods to bridge this gap between people and nature. The study results were performed with the cooperation of EPER Center, professors and students of Durres “Aleksander Moisiu” University. It was focused in the estimation of O2 release from green surfaces at different areas of Durres city. The results achieved were carried out by field visits, the use of the GIS method and calculations performed based on various standard manuals. According to the results, it was concluded that the total amount of O2 release from green surfaces was 64420 kg/year or 64.4 t /year. It was also calculated that the available green surface for a resident in Durres city is only 1.05 m2 out of required 9 m2 per capita. Based on the needs of the population and the EU standards, this study suggests that the amount of O2 release should be 1.49∙ 108 kg/year or 1.49. 5∙ 105 t/year. The needed costs to be invested to achieve this O2 amount, is about 47 .65 billion ALL. Finally, it can be concluded that the low number of trees in Durres city, requires urgent provisions to improve air, and life quality of Durres citizens.

干旱区绿洲城市树木健康评估及影响因素——以乌鲁木齐市为例

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱区绿洲城市树木健康评估及影响因素——以乌鲁木齐市为例 DOI: 10.5846/stxb202106111558 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31770750，31971713） Health assessment of urban trees in arid land oasis cities and its influencing factors: a case study of Urumqi Author: Affiliation: Fund Project: The National Natural Science Foundation of China (31770750，31971713) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:树木作为城市绿色基础设施重要组分，其健康直接影响城市生态系统服务及人居环境质量。城市化进程加快导致生态土地缺失，同时缺乏合理养护加之极端自然条件干扰对树木健康造成严重威胁。为揭示城市树木健康风险及影响因素，对乌鲁木齐市核心城区117个样地绿化树木进行健康评估，从4个维度12个指标构建树木健康分级体系，基于样地调查结果，分析树木组成、结构、关联性、健康状况及影响因素，揭示乌鲁木齐市不同功能区树木健康差异。旨在为研究区树木健康保护、城市绿地可持续经营及城市生态文明建设提供理论依据和数据支撑。结果表明：（1）乌鲁木齐市城市园林树木乔灌比为8.3 ： 1，树木多样性与种间关联程度较低。榆树占比高达43.87%，其中白榆占比22.62%，是主要优势树种；（2）不同树种健康程度呈现差异性，榆树类健康状况呈现圆冠榆 > 大叶榆 > 白榆 > 垂枝榆特征；（3）城市不同功能区树木健康也呈现异质性；以公园和居住小区树木健康分值较高，而行道树和学校庭院树木健康分值相对较低，且冗余分析进一步揭示地面铺装、林木配置结构、生长空间和胸径对树木健康影响程度最为显著。未来优化城市树木生境条件、提升物种丰富度、加强古树名木保育和提高园林绿化管理水平是维护和提升绿洲城市树木健康的重要举措。 Abstract:Urban green space is an important natural and heterogeneous component of urban landscape, which plays an important role in providing urban ecosystem services and improving residents' well-being. As an important component of urban green infrastructure, the health status of urban trees directly affects urban ecosystem services and the quality of human settlement environments. The accelerated urbanization process leads to the loss of ecological land, and the lack of reasonable maintenance and the disturbance of extreme natural conditions pose a serious threat to the health of urban trees, affecting the effective development of the ecological, social and economic benefits of trees. In order to find the risk and influencing factors of urban tree health, a tree health index system was constructed from 4 dimensions and 12 indexes. Based on the survey of 117 sample plots in core urban area of Urumqi, through analyzing the tree composition, structure, association, health status and its influencing factors, the differences of tree health are revealed in different functional zones. The purpose is to provide theoretical basis and data support for tree health protection and sustainable management of urban green space in the study area, which is of great significance to play the landscape service function of green space and improve the degree of urban ecological civilization. The results show that:(1) the average ratio of trees to shrubs in core urban areas in Urumqi is 8.3:1; especially, the tree species diversity, inter and intra correlation of urban green species are low. Elm (Ulmus spp.) accounts for 43.87% of the total urban trees, of which Ulmus pumila accounts for 22.62%, which is the main dominant tree species. (2) There are some differences of the health status between different Elm species. The overall health status of the Elm species elaborates the characteristics of Ulmus densa > Ulmus laevis > Ulmus pumila > Ulmus pumila cv. pendula. (3) The tree health presents heterogeneity in different urban functional zones, which main public parks and residential areas are higher, while roadside and schools are relatively lower. The redundancy analysis further reveals that ground pavement, tree configuration structure, growth space and diameter at breast height (DBH) have the greatest contribution on the tree health. In the future, optimizing urban tree habitat conditions, improving species richness, strengthening conservation of ancient trees and improving landscape planning and management level are important measures to maintain and improve the health status of urban trees in arid land oasis cities. 参考文献 相似文献 引证文献