Urban-rural Gradient Research Articles

Urban-driven decrease in arthropod richness and diversity associated with group-specific changes in arthropod abundance

Habitat loss and fragmentation caused by land-use changes in urbanised landscapes are main drivers of biodiversity loss and changes in species assemblages. While the effects of urbanisation on arthropods has received increasing attention in the last decade, most of the studies were taxon-specific, limited in time and/or covering only part of the habitats along the rural-urban gradient. To comprehensively assess the effects of urbanisation on arthropod communities, here, we sampled arthropods at 180 sites within an urban mosaic in the city of Innsbruck (Austria) using a systematic grid. At each site, arthropods were collected in three micro-habitats: the canopy, the bush layer and tree bark. They were identified to the family, infra-order or order level, depending on the taxonomic group. Urbanisation level was estimated by five different proxies extracted from land use/land cover data (e.g., impervious surface cover), all of them calculated in a 100, 500, and 1,000 m radius around the sampling points, and three indexes based on distance to settlements. We tested for the effects of different levels of urbanisation on (i) overall arthropod abundance, richness and diversity and (ii) community composition using redundancy analyses. In the canopy and the bush layer, arthropod richness and diversity decreased with increasing urbanisation level, suggesting that urbanisation acts as a filter on taxonomic groups. Our data on arthropod abundance further support this hypothesis and suggest that urbanisation disfavours wingless groups, particularly so on trees. Indeed, urbanisation was correlated to lower abundances of spiders and springtails, but higher abundances of aphids, barklice and flies. Arthropod community composition was better explained by a set of urbanisation proxies, especially impervious surface cover measured in a 100, 500, and 1,000 m radius. Arthropods are key elements of food webs and their availability in urban environments is expected to have bottom-up effects, thus shaping foraging behaviour, distribution, and/or success of species at higher trophic levels. Studying ecological networks in urban ecosystems is the next step that will allow to understand how urbanisation alters biodiversity.

Impact of exposure to urban air pollution on grey squirrel (Sciurus carolinensis) lung health

The increased rate of global urbanisation has recently exacerbated the significant public health problem of traffic related air pollution. Despite the known significant impact on human health, little is known about the effects of air pollution on wildlife health. The lung is the primary target organ for the effects of exposure to air pollution, leading to lung inflammation, altering the lung epigenome, culminating in respiratory disease. In this study, we aimed to assess lung health and DNA methylation profiles in Eastern grey squirrel (Sciurus carolinensis) populations living across an urban-rural air pollution gradient. Squirrel lung health was assessed in four populations situated across the most polluted inner-city boroughs to the less polluted edges of Greater London. We also assessed lung DNA methylation across three London sites and a further two rural sites in Sussex and North Wales. Lung and tracheal diseases were present in 28% and 13% of the squirrels respectively. Specifically, focal inflammation (13%), focal macrophages with vacuolated cytoplasm (3%) and endogenous lipid pneumonia (3%). There was no significant difference in prevalence of lung, tracheal diseases, anthracosis (carbon presence) or lung DNA methylation levels between urban sites and urban and rural sites respectively or NO2 levels. BALT (Bronchus-Associated Lymphoid Tissue) was significantly smaller in the site with highest NO2 and contained the highest carbon loading compared to sites with lower NO2, however differences in carbon loading in between sites were not significant. High pollution site individuals also had significantly higher numbers of alveolar macrophages which suggests that grey squirrels are exposed to and respond to traffic-related air pollution and further research is needed to understand the impact of traffic-related air pollutants on wildlife health.

Spatiotemporal Trends in Self-Reported Mask-Wearing Behavior in the United States: Analysis of a Large Cross-sectional Survey.

Face mask wearing has been identified as an effective strategy to prevent the transmission of SARS-CoV-2, yet mask mandates were never imposed nationally in the United States. This decision resulted in a patchwork of local policies and varying compliance, potentially generating heterogeneities in the local trajectories of COVID-19 in the United States. Although numerous studies have investigated the patterns and predictors of masking behavior nationally, most suffer from survey biases and none have been able to characterize mask wearing at fine spatial scales across the United States through different phases of the pandemic. Urgently needed is a debiased spatiotemporal characterization of mask-wearing behavior in the United States. This information is critical to further assess the effectiveness of masking, evaluate the drivers of transmission at different time points during the pandemic, and guide future public health decisions through, for example, forecasting disease surges. We analyzed spatiotemporal masking patterns in over 8 million behavioral survey responses from across the United States, starting in September 2020 through May 2021. We adjusted for sample size and representation using binomial regression models and survey raking, respectively, to produce county-level monthly estimates of masking behavior. We additionally debiased self-reported masking estimates using bias measures derived by comparing vaccination data from the same survey to official records at the county level. Lastly, we evaluated whether individuals' perceptions of their social environment can serve as a less biased form of behavioral surveillance than self-reported data. We found that county-level masking behavior was spatially heterogeneous along an urban-rural gradient, with mask wearing peaking in winter 2021 and declining sharply through May 2021. Our results identified regions where targeted public health efforts could have been most effective and suggest that individuals' frequency of mask wearing may be influenced by national guidance and disease prevalence. We validated our bias correction approach by comparing debiased self-reported mask-wearing estimates with community-reported estimates, after addressing issues of a small sample size and representation. Self-reported behavior estimates were especially prone to social desirability and nonresponse biases, and our findings demonstrated that these biases can be reduced if individuals are asked to report on community rather than self behaviors. Our work highlights the importance of characterizing public health behaviors at fine spatiotemporal scales to capture heterogeneities that may drive outbreak trajectories. Our findings also emphasize the need for a standardized approach to incorporating behavioral big data into public health response efforts. Even large surveys are prone to bias; thus, we advocate for a social sensing approach to behavioral surveillance to enable more accurate estimates of health behaviors. Finally, we invite the public health and behavioral research communities to use our publicly available estimates to consider how bias-corrected behavioral estimates may improve our understanding of protective behaviors during crises and their impact on disease dynamics.

Hydrogen cyanide, a key plant defense, as a potential driver of root-associated nematode communities along urbanization gradients

IntroductionPlant chemical defenses can influence the distribution, community composition, and abundance of soil biota. Urbanization plays a key role in shaping soil biotic communities either directly through changes in soil properties or indirectly via changes in plant characteristics such as defense traits. The effects of urbanization and plant defenses on the abundance and structure of aboveground plant-associated communities have been studied, yet their effects on belowground root-associated communities are poorly understood.MethodsHere we sampled white clover (Trifolium repens L.) leaves and roots along urban–rural gradients in the cities of Antwerp and Ghent, Belgium. We measured production of hydrogen cyanide (HCN) in leaves, a known defense trait against herbivores, and abundances of different feeding guilds of nematodes associated with the roots.ResultsWe found that HCN production decreased with increasing levels of urbanization in both cities. Urbanization was significantly correlated with shifts in root-associated nematode community structure in Antwerp but not in Ghent. Responses of nematode feeding guilds and trophic groups to urbanization were highly dependent on the clovers’ HCN production, especially in Ghent. Changes in nematode channel ratio in Antwerp indicated that urban root-associated nematode communities of white clover were more strongly dominated by fungivorous nematodes.DiscussionOur results demonstrate that urbanization is driving changes in a plant phenotypic trait and in the community structure of root-associated nematodes, as well as that both changes interact. Plant defense mechanisms could thus help elucidate the effects of urbanization on root-associated biota communities. As strong differences existed between the two studied cities, the particular properties of cities should be taken into account to better understand the direction and strength of phenotypic trait changes driven by urbanization.

Allometric Growth of Common Urban Tree Species in Qingdao City of Eastern China

Allometric growth equations help to describe the correlation between the variables of tree biological characteristics (e.g., diameter and height, diameter and canopy width) and estimate tree dynamics at a given tree dimension. Allometric models of common tree species within urban forests are also important to relate ecosystem services to common urban tree measurements such as stem diameter. In this study, allometric growth models were developed for common tree species used for urban greening on the streets of seven municipal districts in Qingdao city of eastern China. A sampling survey was constructed on an urban–rural gradient to obtain the data of tree diameter, crown width, height to live crown base, and tree height. From these measurements, the crown volume and crown projection area of tree species were calculated. The allometric relationship between two variables was established using quantile regression models (95%, 50%, and 5%) to explore its correlation and the influence of tree species characteristics on urban tree allometry. Our results showed that the correlation of allometric growth of different tree species varied largely due to their own characteristics, and the allometric growth of the same tree species was significantly different as well under the fitting of different quantiles. We found that the relationship between crown width and diameter was stronger than that between tree height and diameter. Moreover, the allometric relationship between crown projection area–diameter and crown width–diameter showed similar fitting. The allometric relationship analysis provide theoretical models and a way to use common field data to support urban forestry management and for the subsequent evaluation and prediction of tree functions and ecosystem services.

Analysis of Anthropogenic Disturbances of Green Spaces along an Urban–Rural Gradient of the City of Bujumbura (Burundi)

Bujumbura city has diversified but unevenly distributed green spaces. The typology and anthropogenic disturbances of these green spaces are still unknown. This study presents a typology of green spaces along the urban–rural gradient through a literature review. It assesses the presence of anthropogenic disturbances through inventories in 100 m × 100 m grids. Data reveal that Bujumbura’s green spaces are made up of green squares concentrated exclusively in urban areas, cemeteries present in peri-urban areas and sports green spaces observable all along the urbanization gradient. These green spaces are more exposed to trampling, which is more present in administrative entities with a peri-urban morphological status, as opposed to various constructions in administrative entities with an urban status. Finally, significative pairwise associations of anthropogenic disturbances were observed. The results show the need to protect these green spaces from all kinds of anthropogenic disturbances by raising the eco-responsible awareness of the population and the municipal authorities.

Urban-rural disparities of carbon storage dynamics in China's human settlements driven by population and economic growth

China has experienced a rapid expansion of human settlement in both urban and rural areas over the past three decades. Regarding the impacts on carbon storage, previous studies that only focus on certain ecosystems cannot reflect urban-rural disparities, resulting in the carbon storage changes in human settlement remaining unknown. In this study, we aimed to explore China's urban-rural disparities in human settlement expansion and direct impacts on carbon storage by using the big Earth data technology. The results showed that from 1990 to 2018, the total amount of China's human settlement expansion reached 175,703.80 km2, and the inner-city, peri-urban, and rural components accounted for 21.00 %, 20.18 %, and 58.82 %, respectively. Along with the general tendency of impervious surface area (ISA) growth, there was more soil organic carbon (SOC) (1254.33 TgC) being sealed beneath ISA (0–100 cm depth), compared to a huge reduction in vegetation biomass carbon (VBC) (91.44 TgC) during the study period. The results further indicated that the change density of either VBC or SOC presented a slightly rising trend along the urban-rural gradient, due to the increasingly common encroachment on vegetation and soil types with higher carbon content. We also found that socioeconomic drivers had a greater influence in urban areas than rural areas, and the related correlation exhibited a descending trajectory in both urban and rural areas. There is thus an urgent need to preserve lands with abundant carbon storage and contain the waste of land resources in rural areas. All stakeholders should pay more attention to concerted and targeted regulation policies for well-planned and eco-friendly human settlement expansion such as enhancing rural land use efficiency and promoting large-scale afforestation and continuous urban greening, which will be critical not only for guiding sustainable urbanization all over China but also for mitigating climate change for the entire world.

Legitimacy, Shared Understanding and Exchange of Resources: Co-managing Lakes Along an Urban–Rural Gradient in Greater Bengaluru Metropolitan Region, India

Co-management is increasingly seen as a way forward in natural resource management and collective goods provisioning, especially in the management of urban commons. Co-management entails sharing of power between actors, including elements such as exchange of information and resources as well as changes in regulations favouring the development of common goals among actors. In this paper, we try to understand if and how preconditions of legitimacy, shared understanding and exchange of resources combine to facilitate the co-management of lakes in Greater Bengaluru Metropolitan Region (GBMR), India. To understand these issues, we undertook an exploratory, qualitative analysis of the governance of three lakes located within a single watershed placed along an urban-rural gradient. We provide an exploratory assessment of co-management across the cases situated in diverse contexts, highlighting the importance of heterogeneity of socio-economic settings for co-management of lakes. Community involvement in co-management varies with heterogeneity, correspondingly increasing transaction costs. In urbanising contexts, state actors have started to recognise the political efficacy of non-state actors mobilising knowledge and financial resources for lake management. Involvement of the state custodian and third-sector organisations (NGOs) was found to be crucial in developing and facilitating shared understanding. Deliberation between mutually dependent state and non-state actors was key to overcoming scepticism in order to realign actor perspectives. We highlight that increased acceptance of community participation based on the development of a collective identity and understanding of mutual dependence observed in our urban and rural cases reduced transaction costs and thus enabled co-management.

Spatial inequality of shopping opportunities under the boom of express deliveries in China

The orderly spatial structure of cities promotes city vitality and human well-being. The spatial mismatch between traditional shops and population causes spatial inequality in shopping opportunities along urban‒rural gradients. This spatial inequality has been deconstructed. The rapid expansion of express delivery outlets linked to online shopping reduces the spatial inequality of shopping opportunities to an unknown degree. This study focused on the spatial patterns of shops and express delivery outlets in cities. The Gini coefficient was used to quantify the spatial inequality of shopping opportunities in 18 Chinese cities. This study further compared the ecosystem services of the two types of shopping facilities. The results show that (1) the net ecosystem services provided by express delivery outlets are 3-fold those of shops; (2) the environmental impact of online shopping are lower than those of traditional shopping; (3) express delivery outlets show more spatial dispersion than shops; (4) the spatial inequality of shops is higher than that of express delivery outlets; and (5) the supplement of express delivery outlets to shops reduces spatial inequality by 35%. These findings show that online shopping promotes ecosystem services, reduces the spatial inequality of city structure and improves human well-being and the sustainability of cities.

Factors Shaping Occurrence Probability of a Generalist Raptor Species across an Urban-Rural Gradient

La urbanización es una de las causas más intensivas y rápidas que explican la pérdida de biodiversidad a nivel mundial. La extensión de las áreas urbanas y la configuración del paisaje afectan la habilidad de las rapaces para explotar parches urbanos. El cárabo euroasiático Strix aluco es una especie forestal nocturna con una amplia distribución y bien adaptada a los ambientes urbanos. Sin embargo, siguen siendo desconocidos qué factores relacionados con el hábitat explican su presencia en ambientes urbanizados. Nuestro objetivo general es el de determinar el efecto que tienen los paisajes urbanos en la probabilidad de presencia del cárabo euroasiático a lo largo de un gradiente urbano-rural. Se espera que el cárabo sea capaz de usar los parches urbanos que tengan (1) un mínimo número de jardines/parques con árboles para cazar; y (2) un limitado nivel de ruido durante la noche (ej. autopistas). Nuestro estudio se llevó a cabo en Donostia-San Sebastián, en el País Vasco, norte de España. Los datos se obtuvieron mediante un censo realizado en 2017. El municipio se dividió en 329 cuadrículas y 251 de ellas fueron censadas. Se detectaron cárabos en 141 cuadrículas, y obtuvimos que el ruido nocturno y la cubierta de matorral fueron las variables que más contribuyeron a explicar la probabilidad de presencia; el ruido nocturno tuvo un significativo efecto negativo en la probabilidad de presencia, mientras que la cubierta de matorral tuvo un efecto positivo, probablemente porque la especie utiliza áreas abiertas o semiabiertas para cazar (pero bosques para criar). En general, se puede concluir que las zonas más ruidosas y urbanizadas de la ciudad componen un hábitat no óptimo para la especie.—Pagaldai, N., Rodríguez-Pérez, J., Arnaiz, A. y Arizaga, J. (2023). Factores que afectan a la probabilidad de presencia de una rapaz generalista a lo largo de un gradiente urbano-rural. Ardeola, 70: 75-88.

ANALYSIS OF PERI-URBAN LANDSCAPE COMPOSITION AND ITS SPATIO-TEMPORAL TRANSFORMATIONS: THE CASE OF THE METROPOLITAN DISTRICT OF QUITO

Latin American contemporary cities are facing a rapidly urban dispersion which is mainly occurring in periurban zones. Since these transitional spaces remain geographically and conceptually unclear, having a greater understanding of its landscape composition has become a key issue for territorial planning purposes. In this article, the Metropolitan District of Quito urban-rural gradient landscape composition and its spatiotemporal transformations are analysed. Using satellite images of very high resolution of two periods, five Land Use-Land Covers (LULC) were identified in sixty-four sample polygons. Based on that, a transition matrix and a stability index were developed to analyse landscape composition change intensity. Results demonstrate that peri-urban areas show the highest landscape instability, although through a great diversity of land occupation typologies. The four dominant typologies are analysed. Parsing LULCs independently, vegetation showed the greatest instability, which significantly alters ecosystems and their services. On the other hand, mega-road infrastructure appears to be one of the most dramatic drivers of peri-urban transformation, since samples crossed by new highways experienced the greatest landscape transformation on average. Finally, this methodology and insights could be extrapolated to other Latin American cities, where micro-scale policymaking should be a priority in scenarios of complex and highly heterogeneous peri-urbanization.

ANALYSIS OF PERI-URBAN LANDSCAPE COMPOSITION AND ITS SPATIO-TEMPORAL TRANSFORMATIONS: THE CASE OF THE METROPOLITAN DISTRICT OF QUITO

Latin American contemporary cities are facing a rapidly urban dispersion which is mainly occurring in periurban zones. Since these transitional spaces remain geographically and conceptually unclear, having a greater understanding of its landscape composition has become a key issue for territorial planning purposes. In this article, the Metropolitan District of Quito urban-rural gradient landscape composition and its spatiotemporal transformations are analysed. Using satellite images of very high resolution of two periods, five Land Use-Land Covers (LULC) were identified in sixty-four sample polygons. Based on that, a transition matrix and a stability index were developed to analyse landscape composition change intensity. Results demonstrate that peri-urban areas show the highest landscape instability, although through a great diversity of land occupation typologies. The four dominant typologies are analysed. Parsing LULCs independently, vegetation showed the greatest instability, which significantly alters ecosystems and their services. On the other hand, mega-road infrastructure appears to be one of the most dramatic drivers of peri-urban transformation, since samples crossed by new highways experienced the greatest landscape transformation on average. Finally, this methodology and insights could be extrapolated to other Latin American cities, where micro-scale policymaking should be a priority in scenarios of complex and highly heterogeneous peri-urbanization.

Competition between biogeochemical drivers and land-cover changes determines urban greening or browning

Urban vegetation, a harbinger of future global vegetation change, is controlled by complex urban environments. The urban-rural gradient in vegetation greenness trends and their responses to biogeochemical drivers (e.g. elevated atmospheric CO2 concentration and climate warming) and land-cover changes, however, remain unclear. Here we used satellite-derived enhanced vegetation index to examine the greenness trends for 1500-plus cities in China for 2000–2019. We developed a conceptual framework to differentiate between the contributions of four key drivers to the greenness trends: two biogeochemical drivers, a background biogeochemical driver (BBD) and an urban biogeochemical driver (UBD), and two drivers of land-cover changes, urban expansion or densification (UED) and urban green recovery (UGR). We find that the greening trends gradually decreased from urban cores to urban new towns and then to browning trends in urban fringes. The significant greening in urban cores was mainly contributed by BBD (25.6%) and UBD (52.3%). While the minor greening in urban new towns was contributed by both BBD (33.1%) and UBD (24.1%) and weakened by UED (−39.7%). The UED (−64.4%) dominated the browning in urban fringes. These results suggest that biogeochemical drivers and land-cover changes jointly regulated the urban-rural gradient in greenness trends, which contributes to the assessment of future global vegetation change driven by complex environmental changes.

Epidemiological-survey-based multidimensional modeling for understanding daily mobility during the COVID-19 pandemic across urban-rural gradient in the Chinese mainland

ABSTRACT Human mobility survey data usually suffer from a lack of resources for validation. Epidemiological survey records, which are released to the public as a containment measure by local authorities, provide place visitation details validated by the authority. This study collected and analyzed the epidemiological survey reports published by local governments in the Chinese mainland, between January 2020 and November 2021. To reveal the mobility patterns during the COVID-19 pandemic across the urban-rural gradient in China’s mainland, we derived key mobility indicators from the epidemiological survey data from rural to megacities. We then applied exploratory factor analysis to identify latent factors that affected people’s mobility. We found that the pandemic poses varying impacts across the urban-rural gradient in the Chinese mainland, and the mobility patterns of middle and small cities are more influenced. Our results also showed that the pandemic did not enlarge gender gap in people’s mobility, as gender was not a significant driving factor for explaining people’s quantity of out-of-home activities as well as extent of life space, while age group and city levels were significant. Overall, we argue that the epidemiological survey data are valuable data sources for daily mobility modeling, especially for relevant studies to understand human mobility patterns during the pandemic.

Ixodes ricinus density, Borrelia prevalence and the density of infected nymphs along an urban-rural gradient in southern England.

Ticks are found across a range of habitats, with woodland being particularly important for high densities and prevalence of Borrelia infection. Assessments of risk in urban woodland can be difficult if there are low densities and small sample sizes for Borrelia prevalence estimates. This study targeted six urban woodlands with established tick populations, as well as six woodlands in peri-urban zones and six woodlands in rural zones in and around the cities of Bath and Southampton, in the South of England. Nymph densities were estimated, and 100 nymphs were tested from each of the 18 woodlands studied. Ixodes ricinus ticks were found in all woodlands surveyed, and overall density of nymphs (DON) per 100 m2 was 18.17 in urban woodlands, 26.0 in peri-urban woodlands and 17.67 in rural woodlands. Out of 600 nymphs tested across urban woodlands, 10.3% were infected with Borrelia. The same proportion of nymphs collected in rural woodlands were positive for Borrelia. In peri-urban woodlands, 10.8% of nymphs tested positive. Across both cities combined, density of infected nymphs (DIN) was 2.73 per 100 m2 in peri-urban woodland, 1.87 per 100 m2 in urban woodland and 1.82 per 100 m2 in rural woodland. Overall, DON, Borrelia prevalence and DIN did not differ significantly along an urban-rural gradient. This suggests the risk of Lyme borreliosis transmission could be similar, or perhaps even elevated in urban woodland if there is higher public footfall, subsequent contact with ticks and less awareness of the risks. This is particularly important from a public health perspective, as Borrelia garinii dominated across the gradient and this genospecies is linked to neuroborreliosis.

Microplastics in rivers along an urban-rural gradient in an urban agglomeration: Correlation with land use, potential sources and pathways

Microplastics are ubiquitous and affect all environments, including rivers. In recent years the number of studies about microplastics in rivers has strongly increased. But still many questions exist regarding sources, pathways, and the role of land use patterns. In this study the relationship between microplastics abundance and anthropogenic factors (population density, urbanization, land use types), as well as the potential role of storm sewers as pathways in tributaries of the Wu River in Taichung, central Taiwan, were studied. Two river catchments of the Dali River were studied in greater detail to investigate the influence of land use on microplastics abundance along an urban-rural gradient, and to observe the change of microplastics abundance in the transition from rural to urban areas. Samples were taken from 41 different locations in urban and rural areas using a manta net with a mesh size of 0.3 mm. Results show abundances ranging from 0 pcs/m³ in unpopulated rural areas up to 230 pcs/m³ in densely populated urban centers, and are positively correlated with population density. Remarkably, a sharp increase in microplastics abundance was observed at the transition from rural to urban areas, which coincides with the appearance of storm sewers. Land use analysis revealed that microplastics abundance positively correlates with the size of industrial, residential and traffic areas in the catchment areas, and negatively correlates with the size of forest areas. Source areas for microplastics in the studied rivers are likely residential and commercial areas. Furthermore, the results of this study show that correlations between microplastics abundances and population density or land use patterns along urban-rural gradients are not trivial. Strength of correlations can depend on local factors or how well urban-rural gradients are developed. Absence of correlations need to be considered carefully, as existing correlations might be masked by the above-mentioned factors.

Soil microarthropod distribution on the urban–rural gradient of Riga city: a study with robust sampling method application

AbstractTo address the new challenge of bringing more nature into the urban environment and developing adequate green infrastructure management methods, it is necessary to clarify the regularities of the distribution of the main ecosystem components—soil organism communities on the urban gradient. Microarthropods—collembolans and mites—are the most diverse soil animals and bioindicators of soil conditions. However, no suitable approaches exist so far to help reduce the high workload of soil zoological studies and make the data acquisition for soil assessment faster. To get closer to a solution to this problem, we propose a robust sampling approach using one pooled sample per site with surface area 58 cm2. This was tested in a microarthropod distribution study on the urban gradient of Riga city (Latvia) in six urban habitat types at 21 sites. The use of classical statistical methods for the processing of soil microarthropod data is limited because these data do not meet model requirements on which classical methods are based, first of all, conformity to the normal distribution. These problems are circumvented by bootstrapping methodology, which thanks to increasing computer performance now is implemented in the most modern program packages. We tested a set of such methods: one-way bootstrap-based analysis of variance, nonmetric multidimensional scaling (NMS), nonparametric multiplicative regression (NPMR), multi-response permutation procedure and Chao bootstrap-based rarefaction curves. NMS in combination with NPMR gave the best results providing statistically significant species distribution curves along the urban gradient which were broadly in line with species traits found by other studies.

Achieving balance between socioeconomic development and ecosystem conservation via policy adjustments in Guangdong Province of southeastern China.

Rapid urbanization improves socioeconomic development but challenges ecosystem sustainability. Meanwhile, the gradient responses of ecosystem services (ESs) to landscape structures and associated regime shifts of the agriculture-ecosystem-economy nexus (AEEN) have not been sufficiently addressed, preventing an effective balance between socioeconomic prosperity and ecosystem conservation. To bridge this knowledge gap, this study selected the Guangdong Province of southeastern China to explore landscape dynamics from 1985 to 2020 and their spatially heterogeneous impacts on ESs and the AEEN, based on Integrated Valuation of Ecosystem Services and Trade-offs approach and other biophysical models as well as statistical records about socioeconomic factors. AEEN elements, including ESs, responded directly to policy adjustments in terms of ecosystem restoration and landscape management and presented remarkable regime shifts (i.e., phase changes) and spatial heterogeneity. Aggressive agricultural reclamation before 1999 increased crop productivity but caused vegetation degradation and biomass decline. Accelerated urban expansion and ecosystem restoration efforts have improved economic and ecological benefits but have substantially reduced crop productivity and threatened food security. However, timely policy adjustments since 2009 reversed the declining trend and maintained the grain supply. Landscape composition presented patterns of gradual decline along the urban-rural gradient, which in turn determined ES gradient patterns. For instance, water yield and nitrogen export positively correlated with each other (p < 0.0001) but negatively correlated with other ESs. Our study enriches the understandings of social-ecological systems' response to man-made interventions from AEEN perspective allowing for spatial variabilities and regime shifts, which support policy formulation for coordinating ecological and economic benefits.

Urbanization–land-use interactions predict antibiotic contamination in soil across urban–rural gradients

Antibiotics ubiquitously occur in soils and pose a potential threat to ecosystem health. Concurrently, urbanization and land-use intensification have transformed soil ecosystems, but how they affect antibiotic contamination remain largely unknown. Therefore, we profiled a broad-scale pattern of antibiotics in soil from agricultural lands and green spaces across urbanization gradients, and explored the hypothetical models to verify the effects of urbanization and land-use intensity on antibiotic contamination. The results showed that antibiotic concentrations and seasonality were higher in agricultural soil than in green spaces, which respectively showed linear or hump-shaped declines along with the increasing distance to urban centers. However, the response of antibiotic pollution to land-use intensity depended strongly on the urbanization level. More importantly, interactions between urbanization and land-use explained, on average, 59.6 % of the variation in antibiotic concentrations in soil across urbanization gradients. The proposed interactions can predict the non-linear changes in soil vulnerability to antibiotic contamination. Our study revealed that the urbanization can modulate the effects of land-use intensity on antibiotic concentration and seasonality in the soil environment, and that there is high stress on peri-urban soil ecosystems due to ongoing land-use changes arising from rapid urbanization processes.

Impact of landscape patterns on herb-layer diversity and seed size of Schima superba in urban remnant vegetation: A case study in Guangzhou, Southern China

In order to explore which ecological strategies the remnant vegetation is taken to adapt to urbanization, we investigated three kinds of typical remnant vegetation (grassland, plantation, and secondary forest) in 16 sample sites along the urban–rural gradient in the city of Guangzhou. In this study, we examined plant species composition, and plant diversity, and analyzed the seed of the dominant tree species Schima superba (S. superba) in the secondary forest sites. Those indicators are strongly related with ecological strategies. Eighteen landscape pattern characteristics were determined to reveal the extent of landscape fragmentation. Geographic Information System (GIS), linear regression, and Canonical Correspondence Analysis (CCA) were conducted to analyze the influence of landscape pattern characteristics on plant communities. Results showed that (1) Fragmentation of landscape patterns caused by urbanization has a negative impact on the diversity of herb-layer plants, the dominant species of grassland in the city center are mainly weeds, such as Bidens pilosa and Neyraudia reynaudiana. (2) In order to adapt to the pressure of landscape fragmentation, seeds of S. superba have developed into a larger size, with a competitive advantage over smaller ones. (3) Two different ecological strategies of plant communities adapting to urbanization: The pioneer weeds in grasslands, with high reproductive and dispersal ability, have adopted a r-selection strategy and the dominant tree species with higher survival rates, larger individuals, and longer life spans, have adopted a K-selection strategy to resist disturbance, as well as with a larger seed size to increase viability and settlement ability.