Urban Environmental Stressors Research Articles

Health burden and inequities of urban environmental stressors in Sofia, Bulgaria

Health burden and inequities of urban environmental stressors in Sofia, Bulgaria

Urban abiotic stressors drive changes in the foraging activity and colony growth of the black garden ant Lasius niger

Changes in habitat characteristics are known to have profound effects on biotic communities and their functional traits. In the context of an urban-rural gradient, urbanisation drastically alters abiotic characteristics, e.g., by increasing environmental temperatures and through light pollution. These abiotic changes significantly impact the functional traits of organisms, particularly insects. Furthermore, changes in habitat characteristics also drive changes in the behavioural traits of animals, allowing them to adapt and thrive in new environments. In our study, we focused on the synanthropic ant species Lasius niger as a model organism. We conducted nocturnal field observations and complemented them with laboratory experiments to investigate the influence of night warming (NW) associated with Urban Heat Islands (UHI), light pollution (ALAN), and habitat type on ant foraging behaviour. In addition, we investigated the influence of elevated temperatures on brood development and worker mortality. Our findings revealed that urban populations of L. niger were generally more active during the night compared to their rural counterparts, although the magnitude of this difference varied with specific city characteristics. In laboratory settings, higher temperatures and continuous illumination were associated with increased activity level in ants, again differing between urban and rural populations. Rural ants exhibited more locomotion compared to their urban counterparts when maintained under identical conditions, which might enable them to forage more effectively in a potentially more challenging environment. High temperatures decreased the developmental time of brood from both habitat types and increased worker mortality, although rural colonies were more strongly affected. Overall, our study provides novel insights into the influence of urban environmental stressors on the foraging activity pattern and colony development of ants. Such stressors can be important for the establishment and spread of synanthropic ant species, including invasive ones, and the biotic homogenization of anthropogenic ecosystems.

Assessment of relationship between aging and contaminant-carryover for different filter layer of surgical mask under urban environmental stressors.

Abundant disposable surgical masks (SMs) remain in the environment and continue to age under urban environmental stressors. This study aimed to investigate the aging characteristics of SMs and the effect of different aged layers of SMs on phenanthrene (PHE), tylosin (TYL), and sulfamethazine (SMT) under two different urban environmental stressors (UV and ozone). The results show that UV exposure causes more severe aging of the SM layers than ozone. The middle layer, made of melt-brown fabric, has displayed the highest degree of aging due to its smaller diameter and mechanical strength. The two-dimensional correlation spectroscopy (2D-COS) analysis reveals the different aging sequences of functional groups and three layers in aged SMs under the two urban environmental stressors. Whether the SMs are aged or not, the adsorptions of three organic pollutants on SMs are positively correlated with the octanol-water partition coefficient. Furthermore, except for the dominant hydrophobic interaction, aged SMs can promote the adsorption of three organic pollutants by accessory interactions (hydrogen bonding and partition), depending on their structures. These findings highlight the environmental effects of new microplastic (MP) sources and coexisting pollutants under the influence of COVID-19, which is helpful in accurately evaluating the biological toxicity of SMs.

Indoor and roadside exposures to traffic noise and cardiovascular mortality and the role of urban environmental stressors across a high-rise, high-density environment: A case study in Hong Kong

Traffic noise is a common factor associated with elevated cardiovascular risks. Compact environment and building morphology in a high-rise, high-density city can magnify traffic noise in various locations (e.g., roadside and indoor environments). However, no studies have investigated how indoor and roadside traffic noise separately and jointly influenced cardiovascular risks across a compact environment. Thus, this study applied negative binomial generalized linear mixed models to estimate associations between roadside/indoor exposures to traffic noise and cardiovascular mortality (2006–2015). Stratified analyses were applied to evaluate effect modifications by canopy-layer and surface-layer urban heat island (UHI), night-time light, and greenness. Our results showed that each 1 dB increase in roadside and indoor exposures to traffic noise was positively associated with 1.183 (95% confidence interval (CI): 1.068–1.311) and 1.046 (95% CI: 1.012–1.081) times the risk of all cardiovascular deaths, respectively. When both types of noise were included in the models, the associations of roadside exposure were attenuated and became non-significant whereas the associations of indoor exposure remained consistent. Stronger and significant associations between roadside exposure and cardiovascular mortality were observed in areas with more intensive UHI, more severe light pollution, and lower average greenness. Robust impacts regarding indoor exposure to traffic noise were found after roadside exposure was accounted for. In conclusion, urban environment stressors could act synergistically on their adverse effects on cardiovascular outcomes. Built environment interventions should be applied to minimize indoor exposure to traffic noise to reduce cardiovascular risks, despite complex urban morphology.

Exposure to urban environmental stressors in pregnancy and postpartum depression: A meta-analysis of 11 European birth cohorts

Background and Aim: Urban environmental stressors have been associated with adult depression, but few studies on postpartum depression (PPD) exist. We investigated associations between exposure to urban environmental stressors in pregnancy and PPD. Methods: We included women from 11 European birth cohorts within the EU Child Cohort Network with singleton pregnancies between 1990-2016 and no previously reported depression. Exposures included ambient air pollution (NO2, PM2.5 and PM10), road traffic noise, natural spaces (Normalised Difference Vegetation Index; NDVI, access to major green and blue spaces) and built environment (population density, facility richness and walkability). PPD was assessed using self-report questionnaires collected 3 – 18 months after birth (e.g. Edinburgh Postnatal Depression Questionnaire). We used adjusted logistic regression to estimate cohort-specific associations between single exposures and PPD and pooled results via meta-analysis using DataSHIELD. We also fit multiple exposure models where we hypothesised one exposure may confound the relationship between another exposure and PPD. Results: Rates of PPD ranged from 2 – 17% across cohorts (n = 39,329). In the pooled sample higher levels of NDVI were associated with reduced odds of PPD (OR per IQR difference in NDVI = 0.94, CI 0.89, 1.00), although results were not consistent across indicators of green spaces. We also found a trend for higher levels of traffic noise to be associated with increased odds of PPD (OR Lden >70dB = 1.19, CI 0.89, 1.59). For all other urban stressors associations were close to null and there was considerable heterogeneity between cohorts. Multiple exposure models showed similar results. Conclusions: Overall, this large European meta-analysis provides little evidence for an association between urban environmental stressors and PPD, although our findings provide some evidence that lack of green spaces may be associated with greater risk of PPD. Key words: post-partum depression, air pollution, natural spaces, traffic noise

Assessment of Relationship between Aging and Contaminant-Carryover for Different Filter Layer of Surgical Mask Under Urban Environmental Stressors

Assessment of Relationship between Aging and Contaminant-Carryover for Different Filter Layer of Surgical Mask Under Urban Environmental Stressors

Quiet Route Planning for Pedestrians in Traffic Noise Polluted Environments

Noise pollution is one of the main stressors in urban environments, having negative impacts on people’s quality of life and health. For some groups of citizens, such as school children, patients, and elders, there is a need to support them in finding pedestrian routes in noise polluted areas of cities. In this paper, we focus on the estimation of traffic noise, and present an approach to provide quiet routing services, taking into account the estimated noise levels of roads. By combining Volunteered Geographic Information, official socio-economic data, and open-access GPS trajectory data, we develop a set of traffic related variables, and apply machine learning methods to perform traffic volume estimations. Given the estimated traffic information, an existing traffic noise model is then employed to derive the noise polluted areas. For generation of quiet routes, a new routing algorithm is proposed based on the Dijkstra algorithm. It minimizes the exposure of pedestrians to traffic noise pollution while taking into account the route distance constraint. We apply our quiet routing approach to the city of Heidelberg (Germany). The application results demonstrate the efficacy of our algorithms in the generation of quiet routes customized to pedestrian preferences.

Set of stress biomarkers as a practical tool in the assessment of multistress effect using honeybees from urban and rural areas as a model organism: a pilot study

A decrease among honey bee populations (Apis mellifera) in the traditional apiaries has been observed in recent years. In light of this negative phenomenon, urban beekeeping seems to be an appropriate alternative solution for the bee population in reducing the toxic effects of a large number of pesticides that are commonly used in agricultural ecosystems. Despite the rapid development of urban beekeeping, there is little information regarding the different aspects of the defense effectiveness of bees from the urban and rural areas. The study was aimed to show whether honey bees from these two locations differ in the level of the valuable biomarkers of stress exposure helpful in establishing which bees, from urban or rural areas, are under greater environmental pressure. For this purpose, foragers from an urban rooftop apiary and a traditional rural apiary were collected. The chosen biomarkers were measured in various tissues of bees. The activity of glutathione S-transferase and acetylcholinesterase, the level of total antioxidant capacity, heat shock protein 70 (Hsp70), and defensin were selected for the analyses. In our opinion, the Hsp70 and defensin levels seemed to be important in the indication of urban multistress factors. The higher level of heat shock proteins and defensins in tissues/organs of bees from the urban apiary—in the gut (an increase, respectively, 92% and 7.3%) and fat body (an increase, respectively, 130% and 7.8%), known as targets of environmental toxins, pointed out the urban environment as highly stressful at both the individual and colony levels. In turn, high total antioxidant capacity was measured in the guts of honey bees from rural area (an increase 107%). Such a situation suggests a different mechanism of defense and specificity of rural and urban environmental stressors and also honey bees foraging activity.

Urban-greenway factors’ influence on older adults’ psychological well-being: A case study of Taichung, Taiwan

In Taiwan, about 80 % of the population lives in urban areas, and as the number of older adults inches toward 20 % of the total population by 2026, Taiwan is expected to become a super-aged society. Because urban green spaces are critical for maintaining older adults’ physio-psychological health, maintenance of these spaces can assist the aging-in-place process. Urban greenways not only provide physical environments that support leisure activities, but also create a social environment in which older adults can develop place attachment. These areas improve older adults’ psychological well-being. By contrast, urban environmental stressors (e.g., noise and air pollution) may affect older residents’ well-being negatively. Therefore, this study developed a structural equation model to examine the relationship between physical environment and well-being from urban greenways in Taichung, and it examined how local older residents’ place attachment and perceived environmental stressors influence this relationship. Our dataset included 13 greenways and 769 participants older than 55 living in the vicinity of these greenways. The results indicate that participants perceive lower levels of environmental stress when their local greenway quality is better, enhancing levels of well-being and place attachment, as reported by older adult residents. Since urban greenways are linear public spaces adjacent to roads, greenway designers and planners should place more emphasis on environmental quality to help create high-quality and easy-to-maintain public spaces where older adults can enjoy the outdoors and improve their well-being without worrying about environmental stressors.

Acoustical Perceptions of Building Occupants on Indoor Environmental Quality in Naturally-Ventilated Building Façades

Accelerated growth of urban population and motor vehicles has resulted in constant exposure to urban traffic noise that is one of the significant environmental stressors in urban environments. The aim of this research as a preliminary study is to evaluate acoustical perceptions of building occupants on their dwelling satisfaction with outdoor traffic noise through naturally-ventilated glazed building facades in the Seoul metropolitan area. This area has the highest population density among the largest countries of Organization for Economic Co-operation and Development (OECD). First, quantitative data of the A-weighted equivalent continuous sound levels (LAeq) at six sites in the Seoul metropolitan area were analyzed, showing that LAeq exceeded the thresholds of noise level standards, 65 dB(A) for day-time (06:00 AM to 10:00 PM) and 55 dB(A) for night-time (10:00 PM to 06:00 AM) respectively. Second, a questionnaire survey was conducted to find the environmental impacts of urban noise transmission on building occupants’ comfort and their ventilation behaviors. It showed that approximately 87% of building occupants (n = 92) used mechanical ventilation systems rather than window ventilation methods. Eighty-two percent of participants have experienced sick building syndrome (SBS)-related symptoms such as skin irritations or coughs. Thirty-three percent of the respondents were deterred from opening windows for natural ventilation due to outdoor traffic noise transmission, and 49% of respondents complained mostly of poor task productivity. The survey outcomes propose the importance of acoustically-treated ventilation openings in naturally-ventilated glazed building facades for building occupants’ indoor environmental quality in high-noise urban areas.

Genetic variation of the epigeic earthworm Lumbricus castaneus populations in urban soils of the Paris region (France) revealed using eight newly developed microsatellite markers

Urban soils are subject to intense environmental pressures, e.g. physical disturbance, surface transformation and pollution, which greatly impact the activity of soil organisms. The epigeic earthworm Lumbricus castaneus (Savigny, 1826) is known to be tolerant to trace elements contamination of soils and was found to be abundant in the urban context. In order to investigate how urban environmental stressors shape the population genetic variation of this species, we developed 8 microsatellite loci from a microsatellite-enriched genomic library. Polymorphism was explored in 6 populations (153 individuals) from the Paris region. The number of alleles per locus varied from 7 to 29. The average expected heterozygosity within populations ranged from 0.596 to 0.705. These new microsatellite markers revealed a significant genetic structure at fine spatial scale, highlighting that they could be particularly useful for genetic studies of populations in urban soils.

Urban mycorrhizas: predicting arbuscular mycorrhizal abundance in green roofs

Abstract Mycorrhizas face unique anthropogenic stressors in urban environments, but the factors influencing their abundance in cities remains comparatively unstudied. Using green roofs as a model system, we built a conceptual model outlining the biotic and abiotic factors influencing arbuscular mycorrhizal (AM) fungal abundance in cities. We then tested this model and its multiple causal hypotheses with structural equation modeling using plant, soil, and AM fungal abundance measurements from 60 plots across 12 green roofs in Chicago, USA. The best direct predictor of AM fungal abundance was not plant cover, plant richness, or soil nutrients, but instead green roof age, suggesting temporal accumulation of AM fungal propagules in degraded urban environments. Soil P had the strongest total effect on AM fungal abundance both directly and via indirect promotion of plant cover. This study highlights knowledge gaps and challenges to studying the urban ecology of AM fungi.

Biodiversity in sacred urban spaces of Bengaluru, India

Urban green spaces provide critical social and ecological support for cities, but we know little about their diversity and composition in cities of the Global South. This is especially true of lesser known urban spaces such as sacred sites, which are of important cultural and biodiversity significance. We examine tree diversity and composition in sacred sites in Bengaluru, one of India’s fastest growing cities. We recorded 5504 trees from 93 species across 62 temples, churches, and Hindu, Christian and Muslim cemeteries in central areas of Bengaluru. Over half (52%) of the tree species were of native origin, a much higher proportion when compared to other green spaces in the city such as parks. Tree density in sacred sites was much higher than that in parks and informal settlements in Bengaluru. Temples and Hindu cemeteries contained the highest proportion of native species, with large numbers of Ficus benghalensis, a keystone sacred species. Trees in sacred spaces provide an important buffer against urban environmental stress in Indian cities, and serve as refuges for urban wildlife and biodiversity. We need greater information on these lesser known, but culturally significant alternate spaces. They play an important, though ignored role in the environmental sustainability of rapidly growing cities in the Global South.

Oxidative stress in birds along a NOx and urbanisation gradient: An interspecific approach

Urbanisation is regarded as one of the most threatening global issues for wildlife, however, measuring its impact is not always straight forward. Oxidative stress physiology has been suggested to be a useful biomarker of health and therefore, a potentially important indicator of the impact that urban environmental stressors, especially air pollution, can have on wildlife. For example, nitrogen oxides (NOx), released during incomplete combustion of fossil fuels, are highly potent pro-oxidants, thus predicted to affect either the protective antioxidants and/or cause oxidative damage to bio-molecules. To date, epidemiological modelling of the predicted association between oxidative stress and NOx exposure has not been performed in wild animals. Here, we address this short-coming, by investigating multiple oxidative stress markers in four common passerine bird species, the blue tit (Cyanistes caeruleus), great tit (Parus major), house sparrow (Passer domesticus) and tree sparrow (Passer montanus), living along a gradient of NOx and urbanisation levels in southern Sweden. First of all, the results revealed that long- and medium-term (one month and one week, respectively) NOx levels were highly correlated with the level of urbanisation. This confirms that the commonly used urbanisation index is a reliable proxy for urban air pollution. Furthermore, in accordance to our prediction, individuals exposed to higher long- and medium-term NOx levels/urbanisation had higher plasma antioxidant capacity. However, only tree sparrows showed higher oxidative damage (protein carbonyls) in relation to NOx levels and this association was absent with urbanisation. Lipid peroxidation, glutathione and superoxide dismutase levels did not co-vary with NOx/urbanisation. Given that most oxidative stress biomarkers showed strong species-specificity, independent of variation in NOx/urbanisation, the present study highlights the need to study variation in oxidative stress across contexts, seasons and life-stages in order to understand how the ecology and phylogeny of species interact to affect species resilience to urban environmental stress.

Nitrogen cycling process rates across urban ecosystems.

Nitrogen (N) pollution of freshwater, estuarine, and marine ecosystems is widespread and has numerous environmental and economic impacts. A portion of this excess N comes from urban watersheds comprised of natural and engineered ecosystems which can alter downstream N export. Studies of urban N cycling have focused on either specific ecosystems or on watershed-scale mass balances. Comparisons of specific N transformations across ecosystems are required to contextualize rates from individual studies. Here we reviewed urban N cycling in terrestrial, aquatic, and engineered ecosystems, and compared N processing in these urban ecosystem types to native reference ecosystems. We found that net N mineralization and net nitrification rates were enhanced in urban forests and riparian zones relative to reference ecosystems. Denitrification was highly variable across urban ecosystem types, but no significant differences were found between urban and reference denitrification rates. When focusing on urban streams, ammonium uptake was more rapid than nitrate uptake in urban streams. Additionally, reduction of stormwater runoff coupled with potential decreases in N concentration suggests that green infrastructure may reduce downstream N export. Despite multiple environmental stressors in urban environments, ecosystems within urban watersheds can process and transform N at rates similar to or higher than reference ecosystems.

Coping with environmental stress: The effects of wastewater pollutants on energy stores and leptin levels in insectivorous bats

Anthropogenic environmental stress imposes increasing pressure on ecosystems. Wastewater treatment works (WWTWs) are major stressors in urban environments and are associated with high levels of pollutants that bioaccumulate and elicit stress responses in animals such as bats. Stress responses are linked with increased metabolic rate and may result in energy store depletion. In this study we measured the effects of WWTWs on energy stores and leptin levels in the insectivorous bat, Neoromicia nana. Energy stores including glucose, glycogen, lipids and proteins were measured in the storage tissues (liver and pectoral muscles) and blood of bats. Further, lactic acid was measured in the pectoral muscles to provide an indirect measure of anaerobic respiration and stress. Leptin, the hormone associated with satiation, and hypoxia inducible factor 1α (Hif-1α) were measured in the interscapular brown adipose tissue (iBrAT). Bats caught at WWTWs exhibited significantly higher pectoral glucose and lactic acid concentrations than bats at reference sites, indicating a stress induced increase in glucose demand and increased reliance on gluconeogenesis to fuel this response. However, glycogen, lipid and protein stores were not depleted in WWTW bats. This may be due to their fat-rich diet at WWTW sites. Moreover, this high polyunsaturated fatty acid (PUFA) diet may be responsible for the unexpectedly high leptin levels in WWTW bats. Lactic acid concentrations were elevated in the pectoral muscles of bats at WWTW sites, indicating some degree of oxidative stress although there was no increase in iBrAT Hif-1α levels. These results show that in the face of environmental stresses, N. nana is able to maintain energy stores.

(244) Exploration of racial pain disparities: the role of urban environmental stressors

(244) Exploration of racial pain disparities: the role of urban environmental stressors

Expanding fundamental ecological knowledge by studying urban ecosystems

The expansion, densification and proliferation of urban areas around the world is currently occurring at a rate that is unprecedented in human history. It is predicted that global urban land cover will triple between 2000 and 2030, with some regions (including biodiversity hotspots) experiencing a ninefold increase in urban land cover over the same time period (Seto, G€ uneralp & Hutyra 2012). Accompanying the expansion of urban landscapes, it is anticipated that the human population living in cities and towns globally will increase from 3 5 to 5 billion people within the next 20 years (Fragkias et al. 2013). Thus, the demands of an expanding and urbanizing human population are one of the pressing ecological problems our world is facing (Sanderson et al. 2002), alongside, and in combination with, global climate change and changes to biodiversity at local and global scales (Pimm et al. 2014). Yet, urban environments also present a unique opportunity to expand our fundamental knowledge related to ecology and evolution due to the presence of intense and often novel selection pressures. In the inaugural issue of this journal, Calow (1987) defined functional ecology as the sum of three interactive processes: (i) those occurring between organisms and their environment, (ii) biotic interactions between organisms and (iii) adaptive processes driven by natural selection. The same three processes were highlighted 1 year earlier by Jared Diamond in Nature, when he called for biologists to pay more attention to the potential of using the unprecedented environmental conditions that exist within towns and cities to develop and test evolutionary and ecological theory (Diamond 1986). There is thus a natural synergy between functional ecology and urban ecology, as exemplified by some of the classic papers that have appeared in this journal, such as Rydell (1992) who demonstrated that the form of echolocation system determined the impact of light pollution on bat foraging behaviour. The potential of combining functional ecological research with urban ecology is, however, a long way from being fully realized. This is in part explained by the youth of urban ecology as a discipline. Scientific enquiry into the ecological consequences of urban environments has been underway for over half a century, although most of the momentum emerged after the mid 1990s (McDonnell 2011; Wu 2014). Thus, the focus of much urban research to date has involved describing patterns along environmental gradients (Gagn e 2013; McDonnell & Hahs 2013) rather than investigating the mechanistic processes that lie at the heart of functional ecology. To be effective in addressing the global challenges of urbanization, a much better understanding of how the urban environment affects the ecology and evolution of organisms needs to be developed (Grimm et al. 2008; Marzluff 2012; Gil & Brumm 2014; McDonnell & Hahs 2015). The purpose of this special feature is to draw attention to the plethora of opportunities that await researchers investigating the ecology and evolution of organisms in urban environments. The combination of environmental stressors and conditions within urban areas provides a novel opportunity to test and expand our theories related to ecology and evolution of organisms, and some intriguing insights are already beginning to emerge. For example, the detailed understanding of the molecular, genetic and developmental mechanisms of beak evolution that has arisen from studying Galapagos finches has been significantly advanced by studying beak evolution in the house finch Carpodacus mexicanus in response to novel urban food sources and its consequences for acoustic communication (Badyaev 2010, 2014). Thus, urban ecology has the potential to extend our understanding of extremely well-studied ecological and evolutionary problems.

Urbanization, oxidative stress and inflammation: a question of evolving, acclimatizing or coping with urban environmental stress

Summary To estimate the impact of urbanization on wild animals, it is important to know how different species, populations and/or individuals deal with and respond to environmental stress. Are more urbanized species adapted to their environment, or do individuals acclimatize over the course of their life? Alternatively, do they simply cope at the expense of other functions? These are three key processes that I will address using two important physiological responses as case traits, namely oxidative stress and inflammation, – which are known to be under genetic control as well as showing great plasticity. Oxidative stress is a state of more reactive oxidants than antioxidants, which may cause tissue damage linked to disease and senescence. Inflammation, on the other hand, is the response of vascular tissues to harmful stimuli. However, under progressive stimuli, inflammation may also cause tissue destruction and pathology. Although patterns and strengths of effects are not always clear cut, the often interconnected oxidative stress and inflammation have the potential to be severely affected by urban stressors, thereby mechanistically linking ecology to fitness. Here I discuss five major urban stressors: chemical, noise and artificial night light pollution, disease and diet, and how their individual and combinatory effects may affect these two physiological responses. To start to disentangle whether physiological responses are a question of evolving, acclimatizing or coping with the urban environment, population genetics along with regulatory mechanisms of gene expression will shed light on the ‘costs’ of urban life and help to understand why some species or genotypes thrive, while others are absent, in urban areas. Single nucleotide polymorphism (SNP) has been successful for explaining local adaptation and tolerance towards acute toxic substances. However, for multiple stressors acting in concert, at low chronic exposure, investigations of epigenetic mechanisms regulating gene expression may be more illuminating. Here I review the pathways by which genetic and epigenetic mechanisms can affect oxidative stress and inflammatory responses in urban environments, thereby affecting overall fitness. By doing so, I identify the major outstanding gaps of knowledge in the interfaces between ecology, toxicology, evolutionary and molecular biology to inform future studies of urban wildlife.

Woody Vegetation and Soil Characteristics of Residential Forest Patches and Open Spaces along an Urban-to-Rural Gradient

As the process of urbanization advances across the country, so does the importance of urban forests, which include both trees and the soils in which they grow. Soil microbial biomass, which plays a critical role in nutrient transformation in urban ecosystems, is affected by factors such as soil type and the availability of water, carbon, and nitrogen. The aim of this study was to characterize residual forest patches and open fields in residential areas in the City of Knoxville. A field study was conducted to investigate tree species diversity and determine spatial and temporal soil characteristics along an urban-to-rural gradient. Tree diversity did not differ significantly for residential urban and rural plots in Knoxville, Tennessee. Biologically, there was no indication that soils were affected by tree diversity, in terms of soil microbial biomass C/N along an urban-to-rural gradient in Knoxville residential plots. Rural soils did differ physically from urban soils, cation exchange capacity (CEC) and soil moisture content (GSM). Similarly, physical soil properties such as bulk density, both urban and rural sites were negatively correlated with tree diversity. Results indicate that although the urban-rural gradient is subject to urban environmental stressors, the urban ecosystem is resilient in maintaining the ecosystem functions of more natural systems.