The impact of pruning and mortality on urban tree canopy volume

Urban trees provide a wide range of ecosystem services for city residents, with tall, mature trees with wide crowns generally regarded as preferable. The tree biomass which is responsible for shading, pollution removal, rain runoff retention etc. gets periodically reduced by the municipal tree management practice of pruning. This is a necessary activity, which reduces the risk of infrastructure damage and falling branches, but many estimates of ecosystem service provision in cities do not consider its impact explicitly. Tree mortality is also higher in cities, preventing trees from attaining and remaining at large sizes. This study used extensive field measurements of tree structure to estimate the impact of pruning on 8 tree species in two Italian cities: Taranto and Florence. Crown widths were reduced by 1.6 m on average, however there is large variation between species variation with branches more often being removed for thinning crowns resulting in larger gap fractions, which increased by 15% on average. No significant differences were observed for crown widths or gap fraction between trees pruned 3 and 4 years previously, suggesting that tree crowns structurally recover from pruning after 3 years. A deterministic model revealed that current urban forest pruning rates (every 6 years) and mortality (1%) may create a situation in which a city dominated by the species studied benefits from 93.5% of the maximum ecosystem services possible. This work will allow more nuanced estimates of urban forest services to be calculated.     

Urban wild food foraging locations: Understanding selection criteria to inform green space planning and management

Urban wild food foraging is increasingly attracting attention as an activity in urban green spaces that encourages urban residents’ interaction with their natural environment. However, little is known about the criteria influencing urban foragers’ selection of foraging locations that could inform urban green space management and planning to encourage urban foraging. To elicit these criteria, we conducted 21 semi-structured expert interviews with urban foraging stakeholders in Vienna, Austria, and analysed the data using qualitative content analysis. The respondents suggested 11 criteria that influence the selection of foraging locations. These are related to spatial factors, management of public urban green spaces and the green space activities of other visitors. However, the respondents reported that urban foragers do not uniformly follow these different criteria, but subjectively assess and apply them depending on the specific locations and the plant materials and mushroom species being targeted. For some foragers, even intensively managed public urban green spaces can offer certain advantages. Thus, urban residents forage in public urban green spaces that have diverse properties and management strategies. We suggest that urban foraging is best supported by biodiversity- and wilderness-friendly green space management that supports access to foraging locations, clear foraging regulations and codes of conduct, and comprehensive information about contamination for urban residents. Implementation of these suggestions would not only benefit urban foraging, but also enhance urban biodiversity and guarantee the multifunctional benefits of public urban green spaces for urban residents and urban nature.     

A novel index for assessing perceived availability and public demand for urban green space: Application in a Mediterranean island

The objective benefits that humans derive from natural ecosystems and their enduring manifestation in urban green spaces (UGS) is well-know. Nevertheless, citizens’ preference, and perceived necessity of UGS is not always evident and therefore often not accounted for, especially in the context of urban planning decisions, where it could positively influence the effectiveness of greening strategies. This information is especially important in the Mediterranean islands, due to their unique character. Here we address these aspects, including the way they are affected by UGS perceived adequacy, accessibility, maintenance, distance, and other self-reported obstacles using a questionnaire completed by 703 residents of the Island of Crete, Greece. To integrate results, main covariates are compiled into the newly developed public UGS approval index. Survey results show that, 87.82 % of the participants consider public UGS highly necessary for their wellbeing, while only 69.22 % consider private UGS equally necessary. Nevertheless, private UGS were the most frequently visited green at 16.3 ± 0.7 days/month. Public UGS is considered more necessary for female respondents, under 35 years, living in an apartment in the city. However, it emerged that despite the significantly higher need for public UGS in the urban centers of the island, residents consider UGS inadequate and often inaccessible for people with mobility problems. Integration of the results in the new approval index, shows that citizens of Crete, are on average neutral or disapprove of local public UGS. The outcomes can be used for targeted interventions at existing and strategic planning in new UGS.     

Stress-resistant trees are more common in urban than rural forests: A case study of Cleveland,Ohio’s natural parks

Natural parks are comprised of preserved forested natural areas that are undergoing natural ecological processes. These areas can offer a refuge for local biodiversity and contribute substantially to ecosystem services in both rural areas with relatively low population densities, as well as high-density urban areas. Forested natural parks located in urban areas should experience more stressful environmental conditions than nearby rural areas, yet we know relatively little about how urbanization impacts tree communities within these important natural habitats. To better understand the impact of urbanization on forests, we investigated the species composition, abundance, and diversity of midstory and canopy trees as well as tree seedlings in urban and rural natural parks in and around Cleveland, Ohio. We found that both urban and rural natural parks have similar tree abundance, but midstory and canopy trees as well as tree seedling communities in the urban natural parks included higher abundances of stress-tolerant species compared to rural parks. In addition, this pattern was driven by changes in native tree species, as we observed low abundance of invasive species. More stress-resistant native species in urban areas include Quercus rubra and Prunus serotina, in contrast to rural natural parks which are dominated by Acer spp. and Fagus grandifolia. Lastly, we show that urban and rural natural parks have similar species diversity within plots, but we found higher variation in community composition among urban natural parks compared to among rural parks. Furthermore, Q. rubra and P. serotina were significantly larger in rural natural parks, indicating that both environmental stress and successional stage could drive compositional differences. Thus, we show that urbanization can have unexpected effects on plant community composition and diversity. Our study refutes the idea that these are degraded habitats, highlights the need to conserve them, and suggests that characterization of local variation in self-assembled urban tree communities will provide the most accurate picture of their management needs and potential ecosystem services.     

Nature orientation and opportunity: Who values and who has opportunity for satisfactory green spaces in proximity to their place of residence

Urban green spaces (UGS) provide important contributions to people. Yet, UGS planning requires better understanding of by whom and where such contributions are being valued or missed. Based on a mixed-methods online survey and choice experiment with residents of Wellington in Aotearoa New Zealand, we analyse how much and why residents value UGS and their benefits when deciding where to live and how socio-economic and spatial factors might impact nature orientation and opportunity for satisfactory local UGS. We find that local UGS are an important residential choice criteria for the majority of respondents, especially in the context of Wellington’s intensification plans. However, we show that socio-economic and spatial factors significantly impact whether someone values and is satisfied with UGS in proximity to their place of residence. Our findings call for careful scoping of a city’s population and spatial structure when planning for equitable UGS provision. More holistic approaches to green space planning are needed to address contextualities and the complex interdependencies between nature orientation and opportunity and to plan for green space distributions that provide opportunities now and help shaping nature orientation for future generations.     

Analyzing spatial inequalities in use and experience of urban green spaces

As cities become more densely populated, urban green spaces (UGS) are increasingly important due to the environmental and social benefits they provide. Cities are confronted with the challenge of equitable supply of high-quality urban green that meets the demand of residents. This is particularly relevant in lower-income neighborhoods, which tend to suffer from the lowest supply of (high quality) UGS. In this paper, we perform spatial analysis on the responses of an online user survey to explore how UGS frequency of use, choice, and satisfaction differ by use pattern and place of residence in the Brussels Capital Region. Additionally, we identify the “push-pull” factors of individual UGS by identifying the desirable (pull) and undesirable (push) qualities that may attract or repel the use of a UGS. We find that use pattern is related to choice and experience of UGS. Compared to people who use UGS for social purposes, those who use UGS for nature-oriented reasons more often choose to visit UGS that are substantially farther from their home but are more often satisfied with the UGS they use. Our findings also show that respondents living in areas with higher proportions of disadvantaged groups tend to travel substantially farther to reach their UGS and are more often dissatisfied with the UGS they visit. Finally, our push-pull analysis indicates that characteristics that are important to nature-oriented users, such as quietness and calmness, are often more negatively experienced in dense city center UGS. Our research thus demonstrates the need to bring more green, particularly green that elicits a feeling of “naturalness”, to areas of the city where low green space quality and quantity overlap with areas inhabited by vulnerable populations.     

The effects of land tenure and land use on the urban forest structure and composition of Melbourne

The urban forest provides valuable ecosystem services for enhancing human well-being. Its structure and composition determine the quantity and quality of these services. There has been little research on the heterogeneity in structure and composition of urban forests in the Australasian region, especially in the centre of a highly dynamic and rapidly urbanizing city. This paper quantifies the structure and the composition of the urban forest of Melbourne, Australia's city centre. The effects of land tenure and land use on the heterogeneity of canopy cover, tree density and canopy size were explored. Species and family composition by land use, land ownership and street type were also analysed using the Shannon–Wiener and Jaccard similarity indices. Most of the canopy cover in the city centre is located on public land and is unevenly distributed across the municipality. The mean canopy cover (12.3%) is similar to that found for whole city studies around the world, which often include peri-urban forests. Similarly to other cities, structure varied across different land uses, and tree size, density and cover varied with land tenure and street type. The diversity index shows that the urban forest is rich in species (H′ = 2.9) and is dominated by native species. Improving the distribution, and increasing tree cover and variety of species will result in a more resilient urban centre, able to provide multiple ecosystem services to their residents and its large population of visitors and workers. The study of the urban centre provides further understanding of compact city morphologies, and allows inter-city comparison independent of the size.     

Malaysians’ perception on the contribution of urban green spaces to the UN sustainable development goals

There are only few studies globally that have documented the linkages between urban green spaces (UGS) and sustainable development goals (SDGs). In Malaysia, there is no existing research evaluating the relationship between UGS and SDGs. In this study, we assessed Malaysians’ perception on the association between UGS and seven selected SDGs, building on existing studies that looked at importance of UGS with regards to biodiversity, health, and wellbeing outcomes in Malaysia. Using an online survey of 645 respondents across Malaysia, we tested two hypotheses: H1) perception of SDGs varies by socio-demographic factors and H2) perception of SDGs is moderated by distance to green spaces. A pre-tested structured online questionnaire was administered using a 5-point Likert scale. The data was then analysed using analysis of variance and ordinary least squares. Results show that there is an overall statistically significant difference (p < 0.001) between the sociodemographic variables and the positive perceptions of seven selected SDGs. Several sociodemographic factors (female, younger age, university education, closer to UGS, physical activities in UGS) had positive and significant relationship between UGS and SDGs perception. However, proximity to UGS did not moderate the effect of demographic factors on the attitude towards the SDGs. As Malaysia is becoming a rapidly urbanized country, we suggest developing small green spaces (e. g. pocket parks) in the vicinity of housing areas so that people will have easy access and perform physical activities for their wellbeing. At the same time these green spaces will ultimately contribute to achieving other SDGs in urban areas.     

Private trees contribute uniquely to urban forest diversity,structure and service-based traits

The urban forest provides our communities with a host of benefits through the delivery of ecosystem services. To properly quantify and sustain these benefits, we require a strong baseline understanding of forest structure and diversity. To date, fine-scale work considering urban forest diversity and ecosystem services has often been limited to trees on public land, considering only one or two green space types. However, the governance of urban green spaces means tree species composition is influenced by management decisions at various levels, including by institutions, municipalities, and individual landowners responsible for their care. Using a mixed-method approach combining a traditional field-inventory and community science project, we inventoried urban trees in the residential neighbourhood of Notre-Dame-de-Grȃce, Montreal. We assessed how tree diversity, composition and structure varies across multiple green space types in the public and private domain (parks, institutions, street rights of way and private yards) at multiple scales. We assessed how service-based traits – traits capturing aspects of plant form and functions that urban residents find beneficial – differed across green space types, with implications for the distribution of ecosystem services across the urban landscape. Green space types displayed meaningful differences in tree diversity, structure, and service-based traits. For example, the inclusion of private trees contributed an additional 52 species (>30% of total species) not found in the local public tree inventory. Trees on private land also tended to be smaller than those in the public domain. Beyond patterns of tree richness, size, and abundance we also observed differences in the composition of tree species and service-based traits at site-scales, particularly between street rights-of way and private yards. While species composition varied considerably across street blocks, blocks were very similar to one another in terms of mean service-based traits. Contrastingly, while species composition was similar from yard to yard, yards differed significantly in mean service-based trait values. Our work emphasises that public tree inventories are unlikely to be fully representative of urban forest composition, structure, and benefits, with implications for urban forest management at larger spatial scales.     

Quantitative assessment of the treescape and cityscape of Nanjing,China

The urban landscape is by nature the result of many cultural and natural factors and processes. Cityscape associated with land attributes and human activities expresses a city's social and economic functions. Treescape in the form of species composition, tree dimension and tree performance echoes ecological and environmental functions. The cityscape can be denoted by urban factors, such as tree growing-space condition, tree management regime, human activities and planting history. The hypothesis that the cityscape plays a key role in molding the treescape is tested. Nanjing, an east China city notable for its high tree coverage, is chosen as the study area. A quantitative method has been developed to assess the relationship between cityscape and treescape. Based on statistical analyses on the surveyed results of 6527 trees and related cityscape attributes, this paper explores the pertinent patterns and underlying factors of treescape variations. Species composition has the strongest association with cityscape. Roadside and factories have lower species diversity. Residential and industrial land uses show smaller tree dimension. Trees in residential, commercial, heavy industrial land-uses perform below par. A three-way classification has been developed to examine the effects of urban factors on treescape at different cityscape scales. At the small scale, a well-vegetated groundcover will ensure better tree performance and a lower management burden. The medium-scale cityscape (land-use and habitat) is preferred in the study of treescape attributes and their spatial variations, and is suitable for urban tree planning and management. This revised version was published online in July 2006 with corrections to the Cover Date.     

The ecosystem disservices of trees on sidewalks: A study based on a municipality urban tree inventory in Central Italy

Urban green infrastructure, including street trees, plays a key role in providing ecosystem services to urban residents. However, to fully understand the effective role of trees in the urban context, it is also necessary to evaluate the disservices that they can produce in the development of their functions if not managed in an adequate and integrated way. This contribution aims to demonstrate an approach to assess three disservices (pavement damage, aesthetic damage, likelihood of tree failure) of street trees at the municipal level, starting from the existing municipal tree inventory. In this case study, from the street tree population, a sample of approximately 5% of the trees was drawn by stratified random sampling, where the strata were composed of groups of tree species. In particular, a sampling scheme is adapted in which the probability to select a tree in the sample is greater for bigger trees, under the assumption that the bigger the trees the greater are the disservices caused. In this way, a greater precision of the estimates of the considered disservices for the population of urban trees is expected. The results show a high variability of disservices provision among species groups. The results also confirmed a positive correlation between the considered disservices and tree diameter at breast height, while other tree attributes such as total height and crown diameter were found to be positively related only to pavement damages. Finally, severe pruning can lead to a high level of the aesthetic and functional disservices even for shorter and younger street trees.     

Revised Contemplative Landscape Model (CLM): A reliable and valid evaluation tool for mental health-promoting urban green spaces

Due to rapid urbanization and an increase in mental health issues in urban populations, urban green spaces (UGS) design needs to be optimized to meet mental health and well-being promotion goals. However, existing frameworks and tools that aim to address this pressing need are often not adequately validated against health measures. The Contemplative Landscape Model (CLM), developed in 2016, is the first instrument that measures the quality of UGS and informs landscape design with regard to the mental health and well-being of people passively exposed to them. Recent studies with this tool and developments in UGS literature prompted the development and validation of a revised version of CLM presented here. The reliability and validity of CLM were tested with a panel of independent experts and showed better reliability/internal consistency (ω = .893; α = .890) than the original CLM. This time, validity was tested in two ways: (1) against neuropsychological data (electroencephalogram, EEG, and self-reported valence and arousal ratings), acquired during passive exposure to UGS scenes and (2) through factor analysis of experts’ UGS assessments. Validity testing showed that (1) CLM predicts brain activity patterns associated with mindfulness, relaxation, and positive mood, and (2) contemplativeness of landscapes is a valid construct undergird by two parallel factors both predicting beneficial EEG responses. In conclusion, CLM is an effective and robust instrument for assessing the visual quality of UGS predictive of mental health and well-being benefits in urban residents.     

Allometric equations for urban ash trees (Fraxinus spp.) in Oakville,Southern Ontario,Canada

Tree growth equations are an important and common tool used to effectively assess the yield and determine management practices in forest plantations. Increasingly, they are being developed for urban forests, providing tools to assist urban forest managers with species selection, placement, and estimation of management costs and ecosystem services. This study describes the development of allometric equations for Fraxinus americana and F. pennsylvanica growing in Oakville, Canada. With data collected from 103 ash trees, five allometric models were tested to develop equations estimating diameter-at-breast-height (dbh), tree height, crown width and crown height, using age and dbh as explanatory variables. Mean annual growth rates are presented to demonstrate species growth performance and were not significantly different over the first 40 years of growth for the two species. Of all the tested random coefficient models for both species, the cubic with weight 1/x provided the best fit for estimating dbh from age. The best models for other parameters were the loglog for crown height from dbh, the quadratic for crown diameter from dbh, and the linear for tree height from dbh for F. americana. Model types showed more consistency for F. pennsylvanica with linear providing the best fit for crown diameter, crown height and tree height from dbh. The number of model types suggests the difficulty of fitting any single model to the vast array of conditions affecting plant growth in urban areas where management practices and environment can significantly influence tree size and growth. These models may be used to estimate the growth of ash tree populations in Oakville and communities with similar climate, soil, planting, and management environments.     

A comparison of local and general models of leaf area and biomass of urban trees in USA

Ecosystem service estimation is a very popular topic. Many urban studies use the i-Tree Eco model developed by US Forest Service to estimate ecosystem services. Several ecosystem service estimation studies have been conducted acting upon the assumption that relationships developed elsewhere are applicable to sites that vary in species, site, climate, and environmental conditions. This study tested the accuracy of highly used existing leaf area and biomass models when used outside the region in which it was developed. To do this, we measured 74 urban trees from five species in Stevens Point, Wisconsin collecting data such as diameter at breast height (Dbh), tree height, height to the base of live crown, crown width, crown volume, leaf area, and leaf dry weight biomass. Using the data, we developed two models each to predict leaf area and biomass. Using ten independent samples, we compared our predictions with predictions from the existing models which are also used in i-Tree. Our results indicated that the local models developed in the current study predicted leaf area and biomass better than existing models which had higher prediction error. The difference in prediction will ultimately affect ecosystem services estimation when. using i-Tree, and future studies should acknowledge the difference.     

Assessing the influence of location attributes on urban forest species composition in suburban neighbourhoods

Determining how suburbanization shapes tree-species composition and diversity is vital in Canadian and most nations’ cities, as suburban and peri-urban areas continue to grow faster than any other region. These areas, characterized by various land types and uses, represent differences in management and governance, jurisdiction, planting practices and species selection, and professional and political agendas. Such complexities emphasize the importance of exploring the influence of various environmental and location attributes of suburban neighbourhoods. Using hierarchical cluster analysis to classify urban forest species assemblages, we found that location attributes such as land type, development decade, and geography are influential on species composition and diversity − but only to an extent. We found that street-tree assemblages were classified more distinctly than remnant woodlands, which were in turn more distinct than tree communities found on residential properties. Residential land types had a high degree of species heterogeneity, highlighting the importance of not only considering the location attributes chosen for this study, but also including socioeconomic and cultural variables in future ecological classification schemes. Identifying drivers of species composition and diversity is useful for developing and implementing forest management strategies for urban and peri-urban areas, as different species assemblages give rise to different challenges and management opportunities, as well as varying quantities of ecosystem services, values, and benefits.     

Private residential urban forest structure and carbon storage in a moderate-sized urban area in the Midwest,United States

In conjunction with urbanization and its importance as a major driver of land-use change, increased efforts have been placed on understanding urban forests and the provisioning of ecosystem services. However, very little research has been conducted on private property and little is known about the structure and function of privately owned urban forests. This research examines the structure of and carbon storage services provided by private residential urban forests in a moderate-sized Midwestern city. The primary research questions are as follows: What is the structure of private urban forests, and how does it vary across parcels? How much carbon is stored in tree and soil pools of private urban forests, and how does carbon vary across parcels? Ecological inventories were conducted on 100 residential parcels within 14 Neighborhood and Homeowners Associations of varying size and development age. Tree species richness, diversity, density, and diameter distribution were determined on a per parcel basis and for the entire tree population sampled. Further, tree and soil carbon storage were determined for each parcel. Results of this research demonstrated large variability in per-parcel tree metrics. Twelve of the parcels sampled had two or fewer trees, while eleven had greater than 50 trees. Further, tree carbon storage ranged from no carbon to 11.22 kg C m^?2. Alternatively, soil carbon storage was less variable and averaged 4.7 kg C m^?2, approximately 1.9 times higher than the average carbon stored in trees (2.5 kg C m^?2). Management efforts aimed at maintaining or enhancing carbon storage and other ecosystem services should focus on both soil protection and maximizing services in living biomass. Our results demonstrate that sustaining tree-produced ecosystem services requires maintenance of large old trees and species diversity, not only in terms of relative abundance, but also relative dominance, and in combination, species–specific size distributions.     

The role of urban green spaces in care facilities for elderly people across European cities

Urban green spaces (UGS) are increasingly acknowledged for their importance for the well-being of urban populations. However, studies are lacking the consideration of the demand and use of UGS by different population groups and connecting UGS with social infrastructure. In an era of worldwide urbanization and ageing, this European study sheds light on the role of UGS for care facilities for elderly. 126 care facilities from 17 cities in Austria, Germany, Norway, Poland, Romania and Slovenia took part in an online survey. Administrations of care facilities gave insights on the (1) importance of gardens related to care facilities for the quality of life for the seniors, (2) importance of UGS outside of care facilities for the quality of life for the seniors and (3) the consideration of natural and age-friendly designs and management of ecosystem disservices of UGS. The results emphasize not only the importance of UGS for the quality of life of seniors residing in care facilities, but also for the staff and visitors. UGS contribute to physical activities, recreation, and social interactions. The study found that in particular facilities with an own garden are highly aware of the benefits UGS provide. The study holds important lessons for UGS planning, management and design not only to focus on the quantitative supply of UGS, but also to consider age-sensitive amenities in and access to UGS of high quality for seniors.     

Assessment of green space benefits and burdens for urban health with spatial modeling

We present a new spatial model to quantify and map health-related impacts of urban green space (UGS), with the aim to address major shortcomings of existing models and to meet the needs of urban spatial planners for quantitative, spatially-explicit assessment of both the health benefits and burdens of UGS. This GIS-based model uses publicly available high-resolution geospatial data to estimate street-level values of five major determinants of urban health that are significantly influenced by urban spatial design (including UGS): unattractive views, heat stress, air pollution, perceived unsafety and tick-bite risk. We also describe a potential major application of the model for urban spatial planners, a so-called hotspot analysis for a set of five urban design-related health problems, which can assist in setting spatial priorities in urban greening strategies as well as in designing effective greenspace interventions. Hotspots are areas within a city where urban design-related health problems are the largest. An analysis for Maastricht (The Netherlands) showed that in hotspots UGS was mostly a net burden, but also that redesign of UGS could make its role more beneficial for human health.     

Anomalies in Australian municipal tree managers’ street-tree planting and species selection principles

There is scant research on Australian municipal tree managers’ motivations for street tree planting and the rationales for street tree species selections. Tree managers from 129 city councils across Australia were surveyed to address this knowledge gap. This paper presents the findings from 115 (89%) usable survey responses. Tree managers reported four primary motives for street tree planting: visual and aesthetic (97%), environmental (92%), socio-cultural and community (87%), and health (70%). In contrast, tree species characteristics (97%), management and maintenance issues (92%), visual and aesthetic benefits (89%), site environmental factors (80%) and problems caused by different species (70%) were reported to govern street tree species selection. In spite being the primary motives for planting, considerations for socio-cultural and community benefits (61%) and environmental benefits/ecosystem services (61%) had minor influence on street tree species selection. In absence of established research, Australian city councils’ institutional culture is biased by personal opinions on potential threats to city’s vital infrastructure posed by street tree, resulting in the mismatch between planting and species selection principles. Future research correlating species characteristics to specific ecosystem services/disservices might help Australian city councils to adopt an ecosystem services based approach to street tree planting and species selection.