Relationships between urbanization,tree morphology,and carbon density: An integration of remote sensing,allometric models,and field survey

Urban trees store and sequester large amounts of carbon and are a vital component of natural climate solutions. Despite the well-recognized carbon benefits of urban trees, there is limited effort to examine how spatial distribution of carbon density varies across distinctive social, demographic, and built dimensions of urban landscapes. Moreover, it is unclear whether specific aspects of landscape structure and design could help increase carbon densities in urban trees. Here, we produced a fine-resolution carbon density map of urban trees in New York City (NYC) by integrating high-resolution land cover map, LiDAR-derived tree metrics, i-Tree Eco, and field survey data. We then explored spatial variations of carbon density across the gradients of urban development intensity, social deprivation index, and neighborhood age, and we examined the relationships between carbon density, and fragmentation, aggregation, size, and shape of tree canopy cover. We find that carbon stored in urban trees in NYC is estimated as 1078 Gg, with an average density of 13.8 Mg/ha. This large amount of carbon is unevenly distributed, with carbon densities being highest in Bronx and in open parks and street trees. Furthermore, carbon densities are negatively associated with urban development intensity and the social gradient of deprivation. Regarding the impacts of tree morphology on carbon density, our results show that while the amount of tree cover is the most influential factor in determining carbon density, small-sized forest patches and moderate levels of forest edges are also conductive to increasing carbon densities of urban trees. To incorporate urban forestry into developing innovative, effective, and equitable climate mitigation strategies, planners and decision makers need to identify the optimal spatial configuration of urban forests and invest in tree planting programs in marginalized communities.     

Effects of vegetation structure and environmental characteristics on pollinator diversity in urban green spaces

With accelerating urbanization, insect pollinators in urban ecosystems face challenges such as reduced pollen sources, habitat fragmentation, and damage to the nesting environment. Urban green spaces (UGS) are essential for the stability of pollinator communities. However, little is known about the relationship between vertical layer heterogeneity and horizontal layer complexity of vegetation structure in UGS and pollinator communities. The present study aimed to assess how vegetation structure and environmental characteristics shape the insect pollinator community in UGS. To this end, this study was conducted with seven typical vegetation types which were selected according to the biotope mapping classification system (BMCS) in the ring parks around Hefei City, in Anhui province, China. A total of 11,401 pollinators belonging to 6 orders and 34 families were identified during the eight-month survey. Among the seven habitats under the BMCS, mainly successional short-cut shrub and partly open green space, trees two- or multi-layered broad-leaved mixed forest and partly closed green space, and mainly successional tall grass and partly open green space were identified as high-quality insect pollinator habitats. According to the results of the generalized linear regression, the explanatory power of the four best-fitting generalised linear models is relatively high (over 77%). In four optimal models, the effect of vegetation structure on pollinator community was greater than that of environmental characteristics. The redundancy discriminant analysis showed that the flowering abundance of nectar plants, herb richness, and shrub coverage rate were the three most important factors influencing insect pollinator communities, with a cumulative explanatory power of up to 78.8%. Pollinator abundance was positively influenced by spontaneous herbs and low-intensity management. However, high-intensity management, low diversity of plants, low nectar plant richness, ignoring seasonal nectar plant configuration, and dense tree distribution could limit pollinator reproduction and population growth. These results reflect the status of insect pollinator community in UGS in Hefei city and present a possible direction for improving urban green habitats and plant configurations.     

Multi-scaled habitat considerations for conserving urban biodiversity: native reptiles and small mammals in Brisbane,Australia

The rapid expansion of the world’s urban population is a major driver of contemporary landscape change and ecosystem modification. Urbanisation destroys, degrades and fragments native ecosystems, replacing them with a heterogeneous matrix of urban development, parks, roads, and isolated remnant fragments of varying size and quality. This presents a major challenge for biodiversity conservation within urban areas. To make spatially explicit decisions about urban biodiversity conservation actions, urban planners and managers need to be able to separate the relative influence of landscape composition and configuration from patch and local (site)-scale variables for a range of fauna species. We address this problem using a hierarchical landscape approach for native, terrestrial reptiles and small mammals living in a fragmented semi-urban landscape of Brisbane, Australia. Generalised linear modelling and hierarchical partitioning analysis were applied to quantify the relative influence of landscape composition and configuration, patch size and shape, and local habitat composition and structure on the species’ richness of mammal and reptile assemblages. Landscape structure (composition and configuration) and local-scale habitat structure variables were found to be most important for influencing reptile and mammal assemblages, although the relative importance of specific variables differed between reptile and mammal assemblages. These findings highlight the importance of considering landscape composition and configuration in addition to local habitat elements when planning and/or managing for the conservation of native, terrestrial fauna diversity in urban landscapes.     

Successional change in the insect community of a fragmented landscape

Habitat fragmentation strongly affects insect species diversity and community composition, but few studies have examined landscape effects on long term development of insect communities. As mobile consumers, insects should be sensitive to both local plant community and landscape context. We tested this prediction using sweep-net transects to sample insect communities for 8 years at an experimentally fragmented old-field site in northeastern Kansas, USA. The site included habitat patches undergoing secondary succession, surrounded by a low turf matrix. During the first 5 years, plant richness and cover were measured in patches. Insect species richness, total density, and trophic diversity increased over time on all transects. Cover of woody plants and perennial forbs increased each year, adding structural complexity to successional patches and potentially contributing to increased insect diversity. Within years, insect richness was significantly greater on transects through large successional patches (5000 m²) than on transects through fragmented arrays of 6 medium-sized (total area 1728 m²) or 15 small (480 m²) patches. However, plant cover did not differ among patch types and was uncorrelated with insect richness within years. Insect richness was strongly correlated with insect density, but trophic and α diversities did not differ among patch types, indicating that patch insect communities were subsets of a common species pool. We argue that differences in insect richness resulted from landscape effects on the size of these subsets, not patch succession rates. Greater insect richness on large patches can be explained as a community-level consequence of population responses to resource concentration.     

Overwintering in a megacity: Urban green areas and migratory birds in Mexico City

Nearctic-Neotropical migratory birds are threatened by land-use change throughout their complex annual cycles. While urbanization is an essential driver of land-use change, it is unclear how it affects migrant birds. Although migratory birds are more diverse in non-urban patches of native vegetation than in urban areas, neotropical cities can host diverse assemblages of overwintering migrant birds. Migratory birds in neotropical cities tend to be closely associated with urban green areas (UGAs). However, how their presence and abundance are affected by the habitat elements of UGAs and the urban matrix of neotropical cities is poorly understood. In this study, we compared the migratory bird species richness and abundances among UGAs and the urban matrix of the southern section of the megacity of Mexico City and native vegetation sites outside the city. Our results show that UGAs in neotropical cities provide habitats capable of maintaining complex overwintering migratory bird assemblages with local trees as critical features. We also assess the role that UGAs' characteristics play in determining migrant bird assemblages. We conducted bird censuses and measured habitat traits to determine how migrant bird assemblages are related to the habitat features of our study sites. We measured local, buffer, and spatial habitat features of each UGA. We found 23 overwintering migrant species in the three habitats, with 22 present within UGAs. Both UGAs and urban matrix sites had higher estimated species richness of migrant birds than non-urban native vegetation sites located outside the city. Only local features of UGAs affected migrant birds. While tree abundance in UGAs was positively associated with migratory bird species richness, the proportion of tree coverage was positively related to bird abundance. Our results show that UGAs in neotropical cities can maintain complex overwintering migratory bird assemblages, with trees being the most critical habitat feature. As a result, UGA management focused on maintaining trees and increasing their numbers can improve habitat conditions for migratory birds overwintering in neotropical cities.     

Matrix configuration and patch isolation influences override the species–area relationship for urban butterfly communities

The aim of this paper is to examine the role of urban public parks in maintaining connectivity and butterfly assemblages. Using a regression framework, we first test the relative importance of park size and isolation in predicting abundance and species richness of butterfly assemblages across a set of 24 public parks within a large metropolitan area, Marseille (South-East France). Then, we focus on landscape features that affect diversity patterns of the recorded butterfly communities. In this second part, the urban landscape surrounding each park is described (within a 1 × 1 km window) according to two major components: vegetated areas (habitat patches) and impervious or built areas (matrix patches). Specifically, we aim to test whether the incorporation of this built component (matrix) in the landscape analysis provides new insights into the understanding of ecological connectivity in the urban environment. We found a significant effect of both matrix configuration (shape complexity of the built patches) and distance from regional species pool (park isolation) on diversity of butterflies that overrides park size in their contribution to variation in species richness. This result suggests that many previous studies of interactions between biodiversity and urban landscape have overlooked the influence of the built elements.     

The importance of landscape context for songbirds on migration: body mass gain is related to habitat cover

Landscape context influences many aspects of songbird ecology during the breeding season. The importance of landscape context at stopover sites for migrating songbirds, however, has received less attention. In particular, landscape context may affect the availability and quality of food for refueling during stopovers, which is critical for successful migration. We evaluated the influence of woody habitat cover in the surroundings of stopover sites at several spatial extents on the hourly changes of body mass in two species of European-African forest-dwelling songbird migrants (Willow Warbler, Phylloscopus trochilus, and the Eurasian Redstart, Phoenicurus phoenicurus). Data were sampled by standardized methods from a network of ringing stations throughout Europe during the falls of 1994–1996. In both species, hourly body mass gain calculated for first captures increased with woody habitat cover. We found a similar logarithmic relationship for both species, although for Willow Warblers mass gain was more strongly related to the habitat cover within 5 km, in contrast to 3 km for Redstarts. For Willow Warblers, where sufficient data are available for each year, the relationship is consistent over the years. The shape of the relationship suggests existence of a threshold of landscape suitability for refueling at stopover sites: in sites with less than 10% of woody habitat cover, birds tend to lose body mass or to gain mass at a lower rate. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Comparing street tree assemblages and associated stormwater benefits among communities in metropolitan Cincinnati,Ohio, USA

Green infrastructure approaches leverage vegetation and soil to improve environmental quality. Municipal street trees are crucial components of urban green infrastructure because they provide stormwater interception benefits and other ecosystem services. Thus, it is important to understand the patterns and drivers of structural heterogeneity in urban street tree assemblages. In this study, we compared the forest structure of street trees across nine communities along both geographic and demographic gradients in metropolitan Cincinnati, Ohio, USA. Specifically, we used a two-part statistical model to compare both the proportion of sampled street segments containing zero trees, and basal area magnitude for street segments with trees. We made community-scale comparisons based on street tree management, socioeconomics, and geographic setting. Then, using modeled stormwater interception estimates from i-Tree Streets, we investigated the implications of heterogeneity in street tree assemblages for stormwater interception benefits. The forest structure of street trees varied across communities in relation to management practices, namely participation in the Tree City USA program. As a consequence of this structural difference, we observed a stark discrepancy in estimated stormwater interception between Tree City USA participants (128.7 m³/km street length) and non-participants (59.2 m³/km street length). While street tree assemblages did not vary by community poverty status, we did find differences according to community racial composition. In contrast to previous research, basal area was greater in predominantly black (i.e., African American) and racially mixed communities than in predominantly white communities. We did not observe structural differences across geographic strata. This research underscores the importance of proactive management practices for increasing the forest structure of street trees. Our findings regarding socioeconomics and geographic setting contrast previous studies, suggesting the need for continued research into the drivers of structural heterogeneity in street tree assemblages.     

Rethinking the distribution of urban green spaces in Mexico City: Lessons from the COVID-19 outbreak

The COVID-19 pandemic has exposed inequalities that are expected to widen if no action is taken to support the most marginalized populations. One such inequality is the distribution of urban green spaces (UGS), which are essential to pandemic recovery. Cities that aim to be inclusive and resilient should assess whether access to their UGS is equitably distributed among the population and identify the areas where these spaces are most needed. This study therefore examines the equity of access to UGS in Mexico City at the neighborhood level using network analysis. First, access to UGS was identified at a threshold of 300 m, regardless of UGS size. Second, access was differentiated by the functional level of the UGS, which primarily depends on their size, with larger UGS having more extensive catchment areas. The results of this study suggest a deficit of access to small green spaces in most of the neighborhoods of Mexico City, with the neighborhoods with higher rates of poverty showing an even lower average of UGS access. The results further highlight which neighborhoods in Mexico City should receive priority attention and funding for UGS to mitigate the disproportionate effects of public health crises. This is critical for future city planning and may be used as a roadmap for identifying priority neighborhoods in other cities with similar segregation patterns.     

Branching out to residential lands: Missions and strategies of five tree distribution programs in the U.S

Residential lands constitute a major component of existing and possible tree canopy in many cities in the United States. To expand the urban forest on these lands, some municipalities and nonprofit organizations have launched residential yard tree distribution programs, also known as tree giveaway programs. This paper describes the operations of five tree distribution programs affiliated with the Urban Ecology Collaborative, a regional network for urban forestry professionals. We analyzed the programs’ missions, strategies, and challenges as reported through surveys and interviews conducted with program staff. The programs were led by nonprofit organizations and municipal departments in New York City, NY; Baltimore, MD; Philadelphia, PA; Providence, RI; and Worcester, MA. These organizations focused their tree distribution efforts on private residential lands in response to ambitious tree canopy or planting campaign goals. We assessed these programs through the framework of urban forests as social-ecological systems and discuss the programs’ biophysical, social and institutional contexts. Programs face principle-agent problems related to reliance on individual tree recipients to meet goals; their institutional strategies meant to ameliorate these problems varied. Differing organizational and partner resources influenced the programs’ abilities to perform outreach and follow-up on tree performance. Programs attempted to connect with diverse neighborhoods through free trees, targeting areas with low existing canopy, and forging partnerships with local community groups. Given tree recipients’ demand for smaller flowering or fruiting trees, as well as lack of resources for tree survival monitoring on private lands, program leaders appeared to have turned to social measures of success − spreading a positive message about trees and urban greening − as opposed to biophysical performance metrics. We conclude with suggestions for outcomes monitoring, whether those outcomes are social or biophysical, because monitoring is critical to the sustainability and adaptive management of residential tree programs.     

Multi-scale responses of bird species to tree cover and development in an urbanizing landscape

Landscape change is an ongoing process for even the most established landscapes, especially in context to urban intensification and growth. As urbanization increases over the next century, supporting bird species’ populations within urbanizing areas remains an important conservation challenge. Fundamental elements of the biophysical structure of urban environments in which bird species likely respond include tree cover and human infrastructure. We broadly examine how tree cover and urban development structure bird species distributions along the urban-rural gradient across multiple spatial scales. We established a regional sampling design within the Oak Openings Region of northwestern, Ohio, USA, to survey bird species distributions across an extensive urbanization gradient. Through occupancy modeling, we obtained standardized effects of bird species response to local and landscape-scale predictors and found that landscape tree cover influenced the most species, followed by landscape impervious surface, local building density, and local tree cover. We found that responses varied according to habitat affiliation and migratory distance of individual bird species. Distributions of short-distance, edge habitat species located towards the rural end of the gradient were explained primarily by low levels of urbanization and potential vegetative and supplemental resources associated with these areas, while forest species distributions were primarily related to increasing landscape tree cover. Our findings accentuate the importance of scale relative to urbanization and help target where potential actions may arise to benefit bird diversity. Management will likely need to be implemented by municipal governments and agencies to promote tree cover at landscape scale, followed by residential land management education for private landowners. These approaches will be vital in sustaining biodiversity in urbanizing landscapes as urban growth expands over the next century.     

Amenity trees and green space structure in urban settlements of Kigali,Rwanda

According to the national policy, overall forest and agroforestry cover in Rwanda is to increase up to 30% land cover by 2020. On the other hand, demographic data reveal that Rwanda's urban areas are among the fastest-growing on the continent. Unfortunately, there is only little information of the effects of such a rapid urbanization on tree cover and green space structure, knowing that data on urban plant assemblages in the country are rather rare. The paper discusses developments in Kigali's green spaces with regard to its rapid rate of expansion. An integrated approach of research, combining results from interview sessions, desk-based investigations, walk-over and vegetation surveys, and photogrammetric analyses of remotely acquired imagery was applied. The findings suggest that the city green space network consists of plant assemblages largely dominated by alien species (75%). Tree cover fraction averaged at around 10–35%. No significant difference was observed between field-drawn and photogrammetric-based fraction of tree cover estimates; making the later a quick but cheap tool for rapid tree cover evaluation. Cultivated forests, urban woodlots and domestic garden tree stands are far the most dominant types of green spaces in terms of coverage of city surface area. Street tree communities and institutional gardens appear to be the most intensively designed green space layouts. Both distribution and species composition in domestic gardens were socioeconomic-driven. For instance, palm trees were characteristic of fortunate quarters while fruitbearing ornamental such as Psidium guajava and Persea americana were common within scattered and informal settlements. Markhamia lutea, Erythina abyssinica, Euphorbia candelabrum, Phoenix reclinata and Acacia sieberiana are among native taxa that thrive to keep a place in the city. Euphorbia tirucalli, a native tree that is widespread in home compound fences within informal settlements, is significantly declining as modern housing expands and concrete-based fences replace live enclosures.     

Characterization of co-benefits of green stormwater infrastructure across ecohydrologic regions in the United States

Stormwater Green Infrastructure (SGI) systems such as rain gardens, permeable pavement and bioswales are commonly used in municipalities to reduce urban flooding and water pollution. In conjunction with these direct benefits, SGI systems provide additional social and environmental “co-benefits”. Our goal was to investigate the co-benefits of commonly used SGI systems in five cities in the United States, including Baltimore, Denver, New York City, Philadelphia, and Portland. The i-Tree Eco model was used to predict carbon storage and sequestration, air pollution removal, UV reduction, and cooling effects of trees for individual tree species and estimated SGI tree inventories across the five study cities based on observed tree characteristic data. Aspects of SGI design, environmental factors, and model inputs were assessed to understand what parameters impacted SGI co-benefits predicted by the model. We evaluated the most highly influential parameters using a global sensitivity analysis method. As expected, the type of SGI design, and the overall number of trees utilized within those designs, played a large role in determining the overall amount of co-benefits predicted by the model. However, climate also influenced estimation of benefits produced, with similar responses predicted for cities in the same climate zone (e.g. Baltimore, Philadelphia, and New York City). In particular, the global sensitivity analysis showed that variables influencing environmental conditions and tree growth also impacted final co-benefit predictions produced by i-Tree Eco. study revealed how various assumptions and prevailing equations within the i-Tree Eco model can play a major role in the final outcomes predicted by the model. Studies that use i-Tree Eco to analyze potential co-benefits of SGI projects, especially when the goal is to compare projects across climate zones, should consider what aspects of the results are simply a function of the model itself. Overall, the model predicts that more co-benefits are provided in certain climate zones, an assumption currently supported in the literature.     

Pond area and distance from continuous forests affect amphibian egg distributions in urban green spaces: A case study in Sapporo,Japan

We examined factors that affect egg distributions of amphibians, which are currently declining globally, in urban areas. We counted the number of egg masses of two amphibian species (Hynobius retardatus and Rana pirica) in ponds in urban green spaces during two years (2011 and 2012) and investigated the effects of local and landscape factors on them. Forest area in green spaces and pond area had positive effects, and distance from continuous forests in the suburbs and the rate of pond shore protection had negative effects on the number of eggs. Among these factors, distance from continuous forests and pond area had strong effects on egg distributions. These results suggest the importance of water habitat size and the need for colonization by amphibians from surrounding continuous forests. To conserve urban amphibian assemblages, the preservation of ponds with sufficient area and continuous forests close to urban habitats would be important.     

Modelling multi-species response to landscape dynamics: mosaic cycles support urban biodiversity

The importance of the spatial as well as the temporal structure of habitat patches for urban biodiversity has been recognised, but rarely quantified. In dynamic environments the rate of habitat destruction and recreation (i.e. the landscape turnover rate), the minimum amount of potential habitat, its spatial configuration as well as the environmental conditions determining habitat quality are crucial factors for species occurrence. We analysed species responses to environmental parameters and to the spatio-temporal configuration of urban brownfield habitats in a multi-species approach (37 plant and 43 insect species). Species presence/absence data and soil parameters, site age, vegetation structure and landscape context were recorded by random stratified sampling at 133 study plots in industrial areas in the city of Bremen (Germany). Based on the field data, we predicted species occurrences by species distribution models using a multi-model inference approach. Predicted species communities were driven by successional age both at the scale of a single building lot and at the landscape scale. Minimum average succession time of brownfield habitats required to support all and especially regionally rare species depended on the proportion of available open space; the larger the potential habitat area the faster the acceptable turnover. Most plant, grasshopper, and leafhopper species modelled could be maintained at an intermediate turnover rate (mean age of 10–15 years) and a proportion of open sites of at least 40%. Our modelling approach provides the opportunity of inferring optimal spatio-temporal landscape configurations for urban conservation management from patch scale species-environment relationships. The results indicate that urban planning should incorporate land use dynamics into the management of urban biodiversity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Plant and microbial biodiversity in urban forests and public gardens: Insights for cities’ sustainable development

As the world’s population gets increasingly more urban, the preservation of urban green spaces becomes an important issue in the political agenda worldwide. These spaces may mitigate the negative environmental impacts of urbanisation and improve quality of life. Aiming to increase knowledge in urban biodiversity we compared the diversity of vascular plants and soil microbial communities (fungi and bacteria) in two contrasting typologies of urban green spaces (public gardens and remnant forests) in the city of Coimbra (Portugal). We found 252 taxa of vascular plants of which 58% were native and 42% exotic. Although overall diversity indices were similar in both typologies of green spaces, species richness and percentage cover of native taxa were significantly higher in forests than in gardens. Overall, plant communities in the two typologies of green spaces were distinct. We found high variability among gardens, which is consistent with vegetation in gardens being determined by man rather than by competitive or successional processes. Interestingly, the disparity between gardens and forests was also visible for both bacterial and fungal communities indicating an association between above and below-ground communities. We showed that, due to their origin, remnant forests harbour plant taxa with high conservation and ecological values. It also showed that gardens have higher percentage of exotic species, which led us to conclude that native plant species should be given more emphasis in these spaces. City planners should promote urban development by incorporating an ecological perspective into their management plans to enhance human health and global environmental quality.     

Spiders associated with the meadow and tree canopies of orchards respond differently to habitat fragmentation

The response of animal communities to habitat quality and fragmentation may vary depending on microhabitat associations of species. For example, sensitivity of species to woody habitat fragmentation should increase with their degree of association with woody plants. We investigated effects of local and landscape factors on spider communities in different microhabitats within Swiss apple orchards. We expected a stronger negative effect of woody habitat fragmentation on spiders inhabiting tree canopies compared to spiders living in the meadow. The 30 orchards that we sampled varied in woody habitat amount and isolation at landscape and patch scales. Local factors included management intensity and plant diversity. Spiders associated with meadow were affected by plant diversity, but not by fragmentation. In contrast, spiders associated with canopies responded to isolation from other woody habitats. Surprisingly, we found both positive and negative effects of habitat isolation on local abundance. This indicates that differences in dispersal and/or biotic interactions shape the specific response to habitat isolation. The relative importance of local and landscape factors was in accordance with the microhabitat of the spiders. Thus, considering microhabitat associations can be important for identifying processes that would be overlooked if sampling were pooled for the whole habitat.     

Trait-dependent responses of flower-visiting insects to distance to semi-natural grasslands and landscape heterogeneity

Protecting semi-natural grasslands may through spill-over benefit species richness and abundance of flower-visiting insects in linear habitats, such as uncultivated field boundaries, in agricultural landscapes. However, whether local diversity increases both with decreasing distance from potential source habitats and increasing landscape heterogeneity is poorly known due to a general lack of studies replicated at the landscape scale. We analysed if local assemblages of bumblebees, butterflies and hoverflies in linear uncultivated habitats increased with increasing distance to the nearest semi-natural grassland in 12 replicated landscapes along a gradient of landscape heterogeneity in Scania, Southern Sweden. Species richness and abundance of bumblebees and butterflies, but not hoverflies, decreased with increasing distance to semi-natural grasslands, but none of these groups were related to increasing landscape heterogeneity. Further analyses on trait-specific groups revealed significant decreases in the abundance of sedentary and grassland specialist butterflies with increasing distance to assumed source populations, whereas this was not the case concerning mobile species and grassland generalists. The abundance of all bumblebee trait groups decreased with increasing distance to semi-natural grasslands, but only some species (those nesting above ground, with long colony cycles and with small colony sizes) also increased with increasing landscape heterogeneity. We conclude that local species assemblages of flower-visiting insects in linear habitat elements were mainly affected by the occurrence of nearby semi-natural grasslands. In order to conserve diverse assemblages of flower-visiting insects, including the ecological services they provide, it is important to conserve semi-natural grasslands dispersed throughout agricultural landscapes.     

Factors influencing street tree health in constrained planting spaces: Evidence from Kyoto City,Japan

Street trees are threatened by multiple stresses from biophysical and anthropogenic factors. This situation can be extremely challenging in highly developed urban areas with limited space for tree planting. Asia has some of the most densely populated cities globally, but there is a lack of data on factors affecting street tree health in the region. This study aims to examine the impact of constrained planting environments on the health condition of street trees through a case study in Kyoto City, Japan. The health condition of 1230 street trees distributed throughout the city was assessed from June to October 2018. Additionally, several tree- and site-related variables were collected to identify their impact on tree health. Trees that were in excellent and good condition accounted for 19.9 % and 32.0 % of the sample population, respectively. Multivariate linear regression (N = 1139) revealed that tree health condition was significantly related to pruning intensity, tree pit size, adjacent land use, presence/absence of tree grate or guard, width of sidewalk, tree height, presence/absence of dedicated cycle route, tree pit pattern, crown light exposure, DBH and tree pit type. Platanus × acerifolia and other trees with large diameters exhibited relatively poor condition, along with those in tree pits with concrete paving, without tree grates, or in industrial areas, whereas trees planted in strips exceeding 1.8 m in length and exposed to weak pruning showed the best condition. These results imply the potential for healthy growth of street trees in the restricted planting spaces of Kyoto City, which suggests appropriate management and planting practices. Moreover, our empirical data can inform urban tree managers to support their efforts in making decisions on the better matching of species tolerances with urban site conditions for future street tree plans.     

Equally green? Understanding the distribution of urban green infrastructure across student demographics in four public school districts in North Carolina,USA

Green infrastructure (GI) provides a suite of ecosystem services that are widely recognized as critical to health, well-being, and sustainability on an urbanizing planet. However, the distribution of GI across urban landscapes is frequently uneven, resulting in unequal delivery of these services to low-income residents or those belonging to underserved racial/ethnic identities. While GI distribution has been identified as unequal across municipalities, we investigated whether this was true in public schoolyards within and among urban school districts. We examined schoolyards in four metropolitan areas of diverse socio-economic and demographic compositions in North Carolina, USA to determine if they provided equal exposure to GI, then compared whether this was true of the broader urban landscape. We first classified the land cover of elementary schoolyards and their neighborhoods, then used bivariate and multivariate approaches to analyze the relationships between GI (i.e. tree canopy cover and total GI) and the socioeconomic status and race/ethnicity of the schools and surrounding neighborhoods, respectively. We found that the extent of tree canopy cover and total GI in schoolyards was unrelated to the socioeconomic status and the race/ethnicity of students across the four school districts. In contrast, neighborhoods with lower socioeconomic status and larger populations of underserved race/ethnicity residents had less tree canopy cover and total GI. Although total GI was more evenly distributed in schoolyards, the extent of tree canopy cover and total GI in schoolyards was lower than that in the neighborhoods. This suggests opportunities for school districts to expand GI in schoolyards, leveraging their potential to increase ecosystem services to all children, from increased educational opportunities to improved mental, physical, and environmental well-being.