Urban Intensity Research Articles

The phenological response of European vegetation to urbanisation is mediated by macrobioclimatic factors

Plant phenology is a crucial component of ecosystem functioning and is affected by multiple elements of global change; we therefore need to quantify the current phenological changes associated to human activities and understand their impacts on ecosystems. Urbanisation and the intensification of anthropogenic activities alter meteorological conditions and cause phenological changes in urban vegetation worldwide. We used remote sensing data to evaluate the phenological response (start of season date SOS, length of season LOS and end of season date EOS) of five main vegetation types (evergreen forests, deciduous forests, mixed forests, sparse woody vegetation and grasslands) to urbanisation in the 69 most populated pan-European metropolitan areas (i.e., those that include cities with a population over 450,000 inhabitants) for the period 2002–2021. In general, SOS advanced and LOS increased with urbanisation intensity across European metropolitan areas. We found that macrobioclimatic factors strongly determined the strength and direction of the phenological response to urbanisation intensity. The greatest advances in SOS with increasing urbanisation were registered in metropolitan areas in the Mediterranean region, where there was also more uncertainty in this relationship. The EOS advanced with urbanisation in metropolitan areas in the Mediterranean macrobioclimate, whereas in areas with higher precipitation during summer the opposite trend was observed suggesting water availability mediates the response between urbanisation and autumn phenophases. Our results suggest that macrobioclimatic constraints operating at the continental scale are crucial to understand the relationship between plant phenology and urbanisation intensity.

Human Activities Accelerated Increase in Vegetation in Northwest China over the Three Decades

Natural ecosystems are changing more quickly because of human activities, the type and intensity of which are directly correlated with vegetation greenness. To effectively determine how human activities affect trends in vegetation under climate change, we must differentiate between various types of human activities. The GTWR model can study the spatiotemporal non-stationary relationship between the NDVI trend and climate change. The GTWR model was incorporated into multiple climate variables and improved residual analysis to quantify the contributions of climate change and human activities on vegetation change trends in the Hexi region during different periods. This study divides human activities into four groups based on land use change: urbanization, agricultural expansion, desertification, and ecological restoration to further investigate their contribution to vegetation greenness change. The results showed that in 56.9% of the significant vegetation greening trends between 1982 and 2015, climate factors contributed only 7.4%, while human factors contributed a significant 22.7%. Since the ecological restoration project implemented in 2000, the expansion intensity of ecological restoration and urbanization increased significantly, followed by agricultural expansion and desertification. For the considerable greening trends in the Hexi region, the ecological restoration project contributed 26.7%, while agricultural expansion and urbanization contributed 17.5% and 4.6%, respectively. This study aims to provide new insights for more accurate simulation and evaluation of the interaction effects of climate change and human socio-economic development on vegetation growth.

Long-term satellite observations show continuous increase of vegetation growth enhancement in urban environment

Urbanization shows continuous expansion and development, ushering in the co-evolution of urban environments and vegetation over time. Recent remote sensing-based studies have discovered prevalent vegetation growth enhancement in urban environments. However, whether there is a temporal evolution of the growth enhancement remains unknown and unexplored. Here we expanded the existing framework for assessing the long-term impact of urbanization on vegetation greenness (enhanced vegetation index, EVI) using long time series of remote sensing images and applied it in Changsha, the capital city of Hunan province in China. Results showed that vegetation growth experienced widespread enhancement from 2000 to 2017, and increased 1.8 times from 2000 to 2017, suggesting strong continuous adaptive capability of vegetation to urban conditions. Although the overall impact of urbanization was negative due to the replacement of vegetated surfaces, the growth enhancement nevertheless offset or compensated the direct loss of vegetated cover during urbanization in the magnitude of 28 % in 2000 to 44 % in 2017. Our study also revealed large spatial heterogeneity in vegetation growth response among various districts at different urbanization levels and found an emergent trend under the observed spatial heterogeneity toward an asymptotic maximum with urbanization, showing EVI converges to 0.22 in highly urbanized areas. We further found that the positive effect of urbanization on vegetation growth is a function of urbanization intensity and time, which implies that the effect of the urban environment on vegetation can be simulated and predicted, and can be verified in more cities in the future. Our study is the first to successfully quantify long-term spatial patterns on the co-evolution of urbanization and vegetation, providing a new understanding of the continuous adaptive responses of vegetation growth to urbanization and shedding light on predicting biological responses to future environmental change.

Urban intensity and flower community structure drive monkey beetle assemblage in Cape Town

Background: Urban landscapes present an important opportunity for pollinator conservation, but little is known about the status and distribution of pollinator populations in urban habitats in Africa. This represents a major gap in the development of a global understanding of urban pollinators – particularly from the rapidly urbanising context. This study uses a speciose clade of flower-visiting beetles (Coleoptera: Scarabaeidae: Hopliini) to explore patterns of pollinator distribution in a major metropolitan area in South Africa. Objectives: We investigated community composition across gradients of urban intensity (defined according to the percentage of soil-sealing within 1 km2 of each sampling location) and socio-economic status to determine pollinator responses to these urban landscape effects. Methods: A selection of 142 sites were surveyed twice in the austral spring seasons of 2018 and 2019. Data were collected on habitat structure, flower diversity, and pollinator diversity. Results: The study found that different feeding guilds of monkey beetles favoured different levels of urban intensity and that beetle richness significantly correlated with flower richness. It did not, however, correlate with diversity indicating that abundance is less impacted than the number of species present. Monkey beetles with moderate sensitivity to urban intensity benefitted from the presence of preferred species of flowers. Conclusion: Overall, the findings demonstrate the importance of plant community assemblage in supporting urban monkey beetles. We recommend landscaping with preferred flower species in urban parks to support urban pollinators.

Multi-city assessments of human exposure to extreme heat during heat waves in the United States

There is a lack of understanding of the complex spatiotemporal patterns of heat exposure during heat waves, and the impact of urbanization intensity and urban morphology on heat exposure in urban thermal environments. To address these issues, this study used mean radiant temperature (Tmrt) as an index to indicate human exposure to extreme heat, and generated hourly heat exposure maps at a 1-m spatial resolution in Summer 2020 for heat wave and non-heat wave days across three diversely urbanized and climatically different U.S. cities (Riverside, CA; Des Moines, IA; and Boston, MA) using the SOlar LongWave Environmental Irradiance Geometry (SOLWEIG) model and multi-source remote sensing and GIS data. Based on these high-frequency and microscale maps, we found that heat exposure in urban canyons of downtown areas was high due to relatively low building's height to street's width (H/W) ratio, which resulted in a limited shading effect in the studied cities. Heat exposure during heat waves was enhanced by 6 °C to 10 °C compared to non-heat wave conditions, with the main differences occurring in the early afternoon between 12 pm and 2 pm. We found that hot cities (Riverside, 63 °C) had higher heat exposure than warm cities (Des Moines and Boston, 53 °C and 51 °C) during heat waves. Heat exposure in urban core areas was approximately 5C higher than that in rural areas during heat waves. Additionally, we found that sky view factor was the most important urban morphology factor influencing heat exposure, with a relative importance of over 67% in these cities, but the role of impervious surface and trees varied among these cities. Impervious surface area (ISA) contributed more to heat exposure than trees in dry and hot regions (Riverside), but not in humid and warm cities (Des Moines and Boston). This study is the first to generate hourly heat exposure maps at a 1-m resolution for heat wave and non-heat wave days, and to investigate spatiotemporal patterns and the impacts of urbanization intensity and urban morphology on heat exposure in multiple cities. The findings of this study can be useful in developing urban policies to improve urban thermal environments in diverse urban settings, and our transferable framework can potentially be applied to other cities for heat exposure studies.

Spatial variations of plant species diversity in urban soil seed banks in Beijing, China: Implications for plant regeneration and succession

The near-to-nature urban forestry concept and practices are widely recognized for urban greening, urban ecosystem restoration, urban greenspace management for biodiversity conservation and ecosystem services provision. However, the regeneration and succession of urban vegetation are rarely studied due to the complex settings of the urban environment. To this end, we conducted a large-scale field investigation in the metropolitan area of Beijing, China to explore the spatial variations in plant species composition and diversity in soil seed banks, and their similarity to the aboveground vegetation to assess the potential of urban plant regeneration. Overall, 657 vegetation and soil sampling plots from 219 grids, measuring 2 km × 2 km each, were investigated within two perpendicular 10 km wide transects running across the urban center in north-south and east-west directions within the 6th Ring Road of the city. We recorded a total of 102 plant species in soil seed banks, including 13 tree species, 10 shrub species, and 79 herb species. We found that the soil seed bank species diversity and its similarity to that of the aboveground vegetation communities decreased significantly with the urbanization intensity. Higher urbanization intensity is typically associated with increased human management and a reduction in Greenspace Area (GSA). Soil seed bank species richness increased significantly when GSA exceeded 45 % and the similarity of species composition and diversity between soil seed banks and aboveground vegetation communities was the highest in forest parks. This suggests that habitats under forest park management are more conducive to plant regeneration. Soil seed bank species diversity first increased and then decreased significantly with increased distance to the city center, whereas the species similarity between the soil seed banks and the aboveground vegetation communities showed little change with the ring roads going out. The results of this study have important implications for further understanding the potential for urban vegetation regeneration and sustainability, which have significant implications for urban biodiversity conservation and restoration.

Monitoring Urban Expansion (2000–2020) in Yangtze River Delta Using Time-Series Nighttime Light Data and MODIS NDVI

The Yangtze River Delta Urban Agglomeration (YRDUA), which is located in the convergence zone of “The Belt and Road Initiative”, is one of the regions with the best urbanization foundations in China. Referring to the four five-year plans (China’s national economic plan), this study aimed to investigate the spatiotemporal patterns of urban expansion in the YRDUA from 2000 to 2020. To conduct a long-term analysis of urbanization, an extended time series (2000–2020) of a nighttime light (NTL) dataset was built from the multi-temporal Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) data (2000–2013), and Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS) data (2014–2020); data from these sources are crucial to understanding the urbanization processes in the region in order for more effective decision making to take place. The support vector machine (SVM) method was used to extract urban clusters from the extended time-series NTL data and MODIS NDVI products. The evolution of the urban expansion intensity was detected at city scales, and the inequality of urban growth was demonstrated using the Lorenz curve and Gini coefficient. Finally, a quantitative relationship between urban NTL intensity and socio-economic data was built to explore the main factors that control urban intensity. The results indicated that the urban extents extracted from time-series NTL data were consistent with those extracted from Landsat data, with an average overall accuracy (OA) of 89%. A relatively fast urbanization pace was observed during the 10th five-year plan (from 2000 to 2005), which then declined slightly in the 11th five-year plan (from 2006 to 2010). By the 12th and 13th five-year plan (from 2011 to 2020), urban clusters in all cities tended to grow steadily. Urban expansion has presented a radial pattern around the main cities, with sprawl inequality across cities. The results further revealed that the primary factors controlling NTL brightness were gross domestic product (GDP), total fixed asset investment, tertiary industry, gross industrial output, urban area, and urban permanent residents in city clusters, but the same driving factors had a different contribution order on the NTL intensity across cities. This study provides significant insight for further urbanization study to be conducted in the YRDUA region, which is crucial for sustainable urban development in the region.

Urbanisation of a growing tropical mega-city during the 21st century — Landscape transformation and vegetation dynamics

Fine scale spatial and temporal patterns in land-cover dynamics arising from rapid urbanisation of tropical regions are poorly understood. We quantify changes in landcover across the Bangkok region using high-resolution aerial imagery from ∼ 2004 to ∼ 2018 and address three questions: i) does urbanisation generate temporal shifts in the form of vegetation cover-urbanisation intensity relationships?, ii) do urban expansion and densification generate different vegetation dynamics?, iii) do net changes in vegetation cover and loss vary with urbanisation intensity? The form of vegetation cover-urbanisation intensity relationships exhibited negligible temporal variation, supporting the use of space-for-time substitution approaches for predicting future landcover dynamics. During our study period impervious surface cover increased by ∼ 474 km2and there were net losses of grassland (∼583 km2) and rice-fields (∼94 km2), and a net gain in treecover (∼137 km2). These changes have substantial implications for urban heat islands, flood risk and biodiversity. Urban expansion contributed more to vegetation dynamics than densification, partly because expansion impacted more land. Densification minimised loss of green-space, grasslands, and agriculture (rice-fields), but generated substantial local tree cover loss, which is critical to retain in highly urbanised areas. This contrasts with increasing tree cover elsewhere, including areas experiencing urban expansion. Trade-offs thus arise between impacts on different vegetation types when meeting the demand for tropical urban development through densification or expansion. Densification benefits most vegetation types but must be accompanied with tree protection and planting schemes to balance these trade-offs and minimise detrimental impacts of densification on people, ecosystem services and biodiversity.

Intensity as the Perceivable Dimension of Density in the Urban Environment: The Case of Housing Blocks by MBM Arquitectes in Barcelona, Spain

The concept of intensity is a concentration of spatial, social, and environmental experiences in the urban environment. It is an extension of density, beyond the quantitative measure of the urban environment toward its qualitative and perceivable aspects. Drawing on urban studies with a human-centered approach by Michael Sorkin, Jane Jacobs, Jan Gehl and William T. Whyte, and proxemics studies by Edward T. Hall, this paper explores the spatial implications of intensity to identify the qualities of the built environment that positively influence the relationship between people and space. With this purpose, case studies were selected from the housing complexes designed, from the 1960s to the 1990s, by the architectural office MBM Arquitectes in Barcelona (Spain). The observational, spatial and visual analysis focused on the public spaces of those housing complexes as well as on the use and appropriation of them by inhabitants. Public spaces are the ground for studying urban intensity: they are the set where urban life can be performed and the main vehicle for promoting intentional relationships between people and space. A series of five spatial qualities were identified as categories of perceived urban intensity and are discussed in detail: Connection, Articulation, Differentiation, Extension and Concentration. Such categories can help orient the analysis and interpretation of the physical and perceptual materials of urban intensity, to better understand the design of our public space, our cities and their futures.

Does the development zone promote population urbanization? Evidence from China

As the main space carriers of industrial agglomeration and land development, the development zones’ (DZs’) ability to absorb the population is crucial to the coordination of land urbanization and population urbanization. Based on the theory of New Economic Geography, this study uses China’s fifth and sixth census data to empirically analyze the impact and mechanism of DZs on population urbanization by comprehensively utilizing propensity score matching, difference-in-difference model and mediating effect model. Results show that the establishment of DZs can promote the population urbanization. When the dominant industries planned by the DZs are in line with the local comparative advantage, the intensity of population urbanization affected by the DZs will enhance. The “policy rents” provided by the DZs attract firms to gather, which in turn creates additional jobs by attracting new firms and expanding the scale of incumbent firms, attracting additional population inflow. From another perspective, the establishment of DZs improves labor’s wages and welfare, promotes the stable living of labor nearby, which boost population urbanization. In addition, the expansion of land supply is also a channel for the DZ to promote population urbanization.

Modeling the intensity of surface urban heat island based on the impervious surface area

The urban heat island (UHI) effect is anticipated to be intensified and cause severe damage to human society under future urbanization and climate change. Due to the complicated human-nature interactions in the urban domain, it is challenging to characterize the intensity of UHI quantitatively, especially at the global scale. Here, we proposed a framework to estimate the surface urban heat island intensity (SUHII) based on satellite-derived land surface temperature (LST) and the derived impervious surface area (ISA) data across 355 cities worldwide from 2003 to 2018. First, we employed linear regression models to estimate LST using ISA as the explanatory variable, given that the LST generally elevated with increasing urban intensity along the urban-rural gradient. Then, using the modeled LST, we estimated the spatiotemporal patterns of SUHII worldwide. The established linear regression models with ISA as the explanatory variable perform reasonably well in estimating LST for both daytime and nighttime, with average RMSEs of 1.40 and 0.80 °C, respectively. The resulting SUHII reasonably captures the spatial heterogeneity across cities in the world, with the highest value in the tropical region at daytime and in the arid region at nighttime. The estimated and observed SUHII show good agreement with average R2 values of 0.81 and 0.72 for daytime and nighttime, respectively. Using ISA as an indicator for LST estimation, this study first implemented a comprehensive estimation of SUHII at the global scale. The proposed methodology is of great potential to project future SUHII by expanding urban impervious surfaces under diverse scenarios jointly determined by shared socioeconomic pathways and climate change scenarios.

Effects of Glomalin-Related Soil Protein Driven by Root on Forest Soil Aggregate Stability and Carbon Sequestration during Urbanization in Nanchang, China.

Glomalin-related soil protein (GRSP) is a hydrophobic protein released by arbuscular mycorrhizal fungi. It is an important component of the soil carbon pool, and it improves the soil aggregate structure; however, it remains unclear whether GRSP can enhance soil carbon sequestration and improve soil quality during rapid urbanization. The built-up area in Nanchang, China was the study area, and the proportion of impervious surface area was the parameter of urbanization intensity. A total of 184 plots (400 m2) were set up to collect soil samples (0-20 cm) for analysis. Aggregates of five particle sizes were sieved, and the percentage amounts of soil organic carbon (SOC) and GRSP for them were determined. The results showed that the easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) contents of the four aggregates of <2 mm were 22-46% higher in low urbanization areas than those in high urbanization areas (p < 0.05), indicating that the higher urbanization intensity was associated with the lower GRSP content of different aggregates. The GRSP was significantly positively correlated with SOC (p < 0.05). Moreover, the contribution of GRSP to the SOC pool in the <0.25 mm aggregate was significantly higher than that in other aggregates. In addition, the EE-GRSP content was significantly positively correlated with mean weight diameter (MWD) and geometric mean diameter (GMD) in the four aggregates of <2 mm, whereas it was negatively correlated with fractal dimension (D) in the >2 mm, 1-2 mm and <0.053 mm aggregates. The T-GRSP content showed significant correlations only with MWD, GMD, and D in the 1-2 mm aggregate. This study revealed that increasing urbanization intensity can significantly reduce the GRSP content of different sized aggregates. Moreover, the GRSP content significantly promoted SOC sequestration, and the EE-GRSP content more significantly promoted soil aggregate stability than that of the T-GRSP. These findings provide new ideas for exploring the improvement of soil quality during the process of urbanization.

Biodiversity and environmental stressors along urban walking routes

There is increasing focus on designing liveable cities that promote walking. However, urban walking routes can expose people to adverse environmental conditions that reduce health, well-being and biodiversity. Our primary objective is to assess how urban form is associated with environmental quality, including biodiversity, for people moving through urban spaces. We assess a range of environmental conditions that influence human health and biodiversity (temperature, noise and particulate pollution) and biodiversity of three taxa (trees, butterflies and birds) along 700 m public walking routes embedded in 500 m x 500 m grid cells across three UK towns. Cells are selected using random stratification across an urbanisation intensity gradient. Walking routes in more built-up areas were noisier and hotter; noise levels further increased in areas with more industrial land-use and large roads. There was no evidence of vegetation mitigating noise or temperature, but there was some evidence that increased vegetation cover mitigated small particulate pollution. Walking routes in more built-up environments had lower butterfly, bird and native tree species richness, and reduced butterfly abundance. Large roads were associated with reduced bird species richness and increased noise was associated with reduced bird abundance. Most specific measures of vegetation in the surrounding matrix (median patch size, structural complexity at 1.5 m resolution) were not detectably associated with biodiversity along walking routes, indicating minimal beneficial spill-over. Increased garden cover in the surrounding matrix was associated with less abundant and less species-rich butterfly communities. Our results highlight considerable heterogeneity in the environmental quality of urban walking routes and pedestrians’ potential to experience biodiversity along these routes, driven by reduced quality in areas with more built cover. A greater focus is needed on mitigating adverse effects of specific features of the built environment (roads, industrial areas, noise) surrounding walking routes to enhance the co-benefits of more biodiversity and healthier conditions for pedestrians.

Vegetation growth enhancement modulated by urban development status

Cities are natural laboratories for studying the vegetation response to global change due to their own climatic, atmospheric, and biological conditions. However, whether the urban environment promoted vegetation growth is still uncertain. Using the Yangtze River Delta (YRD), an economic powerhouse of modern China, as a case study, this paper investigated the impact of urban environment on vegetation growth at three scales: cities, sub-cities (rural-urban gradient) -pixels. Based on the satellite observations of vegetation growth indicated during 2000–2020, we explored the direct (replacement of original land by impervious surfaces) and indirect impact (e.g., climatic environment) of urbanization on vegetation growth and their trends with urbanization level. We found that significant greening accounted for 43.18 %, and significant browning accounted for 3.60 % of the pixels in the YRD. Urban area was turning green faster than suburban area. Moreover, land use change intensity (D) was a representation of the direct impact ωd of urbanization. The direct impact of urbanization on vegetation growth was positively correlated with the intensity of land use change. Furthermore, vegetation growth enhancement due to indirect impact ωi occurred in 31.71 %, 43.90 % and 41.46 % of the YRD cities in 2000, 2010 and 2020. And vegetation enhancement occurred in 94.12 % of highly urbanized cities in 2020, while in medium and low urbanization cities, the averaged indirect impact was near zero or even negative, proving that vegetation growth enhancement was modulated by urban development status. Also, the growth offset (τ) was most pronounced in high urbanization cities (4.92 %), but there was no growth compensation in medium urbanization cities (−4.48 %) and low urbanization cities (−57.47 %). When urbanization intensity reached a threshold value of 50 % in highly urbanized cities, the growth offset (τ) tended to saturate and remained unchanged. Our findings have important implications for understanding the vegetation response to continuing urbanization process and future climate change.

Plant Traits of Tilia tomentosa Moench, Fraxinus excelsior L., and Pinus nigra J.F.Arnold as a Proxy of Urbanization

Linden, ash, and pine are ubiquitous ornamental trees due to their ability to adapt to the urban environment. They have been key species in urban green infrastructure from more than hundreds of years and play an active role in maintaining ecosystem services. The urbanization rate in recent decades, combined with global climate change, has led to dynamic changes in the environmental factors which pose new challenges to urban vegetation. Hence, the aims of this study were as follows: (i) to track changes in the content of some elements in plant leaves after transplanting them into an urban environment; (ii) to investigate the relationship between urbanization intensity with plant traits (leaf injuries, photosynthetic activity, transpiration, stomatal conductance, and molecular changes); and (iii) to provide recommendations for improving the management and ecological functions of urban trees. To address these aims, data on urbanization intensity (according to the percentage of built-up area and traffic volume), plant performance, and intraspecific variations of silver linden (Tilia tomentosa), European ash (Fraxinus excelsior), and European black pine (Pinus nigra) were collected at four experimental plots in the city of Plovdiv (Bulgaria) during 2015–2020. The initial concentrations of some potentially toxic elements (As, Cd, Cr, Cu, Mn, Pb, V, and Zn) in the tree leaves at the beginning (prior to planting into the urban environment) and at the end of the experiment were also measured. We illustrate that the growth of urbanization intensity increased the concentrations of potentially toxic elements in tree leaves, caused leaf injuries, and enhanced the maximum photosynthetic rate but decreased the transpiration rate and stomatal conductance. At the molecular level, the percentage of polymorphic bands was also found to depend on urbanization intensity. High similarity was observed between the trees in the first three experimental plots (subjected to urbanization load), with the lowest similarity in the control plot. These findings are of high practical value for urban planners regarding how to build a new green infrastructure and how to preserve plant diversity in urban areas across urbanization gradients.

Dynamic Responses of Landscape Pattern and Vegetation Coverage to Urban Expansion and Greening: A Case Study of the Severe Cold Region, China

Urbanization is the natural trend of human social development, which leads to various changes in vegetation conditions. Analyzing the dynamics of landscape patterns and vegetation coverage in response to urban expansion is important for understanding the ecological influence of urban expansion and guiding sustainable urban development. However, existing studies on the effects of urbanization on vegetation conditions in severe cold regions are limited. Here, taking Harbin, China as an example, the study explored the evolution of the urban expansion process and adopted landscape metrics to derive landscape pattern changes from 2005 to 2020. Based on the fraction of vegetation coverage (FVC) derived from Landsat satellite observations during 2004–2020, we investigated the spatiotemporal change characteristics of FVC. By separating the direct and indirect effects of urbanization on vegetation growth, we quantified the impacts of urbanization on vegetation. The results show that the urban area increased by 70.37%, and urban expansion exhibited a compact sprawl pattern. Cropland and water were the major resources converted for urban expansion. The distribution of FVC exhibits a pattern that the urban fringe region is significantly higher than the central region. The FVC trend is decreased overall, but the changes are not significant with regional variation. Moreover, the average observed FVC decreased with increasing urban intensity. By contrast, the indirect impact is increased along the intensity gradient, with growth enhancement offsetting about 2.26%~2.71% of direct vegetation loss. The study further shows that vegetation growth responses to urbanization vary according to urbanization levels. Our findings provide detailed information and reveal the relationship between urban intensity and vegetation coverage, which could help to manage urban vegetation for planners and stakeholders.

Influence of urbanisation on the phenology of evergreen coniferous and deciduous broadleaf trees in Madrid (Spain)

Plant phenology plays a crucial role in terrestrial ecosystems and is a key indicator of ecological changes. It is influenced by alterations in meteorological conditions at micro- and mesoscale in cities as a result of urbanisation and the intensification of anthropogenic activities. One example is the urban heat island (UHI), i.e. the increase in temperature in city cores compared to their surroundings. In this study, we used plant phenological data from the High-Resolution Vegetation Phenology and Productivity dataset of the Copernicus Land Monitoring Service to explore the relationship between urbanisation intensity (i.e., proportion of built-up area) and the phenology and productivity of broadleaf deciduous and evergreen coniferous trees in the city of Madrid and its surroundings, one of the largest metropolitan areas in Europe. We found the average start of season date advanced by 0.79–11.79 days in broadleaf deciduous trees in highly urbanised areas, and was delayed by 5.77–9.16 days in evergreen coniferous trees. Although differences were also observed for the end and length of the growing season, these patterns showed great interannual variability. Both broadleaf deciduous and evergreen coniferous trees were most productive in highly urbanised areas. Although previous studies have explored the response of different land-cover types to urbanisation, to our knowledge, none have looked at this relationship at a fine spatial scale in a Mediterranean city with different vegetation functional groups. The analysis of more specific classes of vegetation enables a better understanding of the phenological response of vegetation to urbanisation intensity.

Urban epiphytes: Bromeliad diversity in a green cover gradient across a Neotropical streetscape

The Neotropical region is undergoing high levels of urban expansion and harbors the greatest diversity of vascular epiphytes globally. In cities, it could be expected that the density of woody vegetation positively predicts epiphyte communities by providing substrate, resources for pollinators, and buffering microclimatic conditions. However, there is a dearth of knowledge regarding how urbanization intensity affects the diversity of vascular epiphytes. In this study, we assessed the relationship between a woody cover gradient and bromeliad species richness and community composition across a streetscape of the Neotropical city of Xalapa (Mexico). We recorded bromeliads in nine street segments and one peri-urban green space. These sites represent a gradient of woody cover ranging from 10.5% to ∼87% in a 100 m buffer, and 100% in the peri-urban green space. We recorded 824 individuals of 14 species (all from the Tillandsioideae subfamily). The most abundant species was Tillandsia recurvata and the most frequent ones were T. juncea and T. schiedeana. Results show that bromeliad species richness was positively related to the woody cover, as expected. Interestingly, community composition did not associate with the percentage of woody cover. These results suggest that additional factors such as microclimatic conditions and seed availability and/or dispersal may be key modulators on the establishment of bromeliad species. Nevertheless, wooded streets do show potential for harboring diverse bromeliad communities.

Beta diversity of urban spontaneous plants and its drivers in 9 major cities of Yunnan province, China

Urbanization has significantly reshaped regional biodiversity structure globally. Previous studies suggested that urban communities of spontaneous plants are well adapted to the urban environment. However, a perspective of urbanization that accounts for the joint impacts of the current state (as expressed by urbanization intensity) and the historical progress of urbanization (as expressed by urbanization rate) to reveal the mechanisms underlying the biodiversity patterns of spontaneous plants in cities is still lacking. Here we present data and analysis of spontaneous plants sampled in 709 patches within 82 sites of built-up areas from nine cities distributed across climatic and floristic zones in Yunnan province, a biodiversity hotspot in China. We used the exponent (z) of a species accumulation curve (SAC) model to characterize beta diversity among patches in a site, and found a higher beta diversity of native species compared with non-natives, indicating that the species composition of native plants is more heterogeneous. The beta diversity of all species groups was best explained by the constant c of the SAC (a proxy of alpha diversity), followed by the urbanization intensity (as expressed by the proportion of sealed surface and patches’ Shannon diversity index), and urbanization rate (as expressed by the sealed surface expansion rate). Moreover, beta diversity of non-native species was additionally negatively correlated with altitude. Our results suggest that the interplay of natural environmental factors and human-induced urbanization shape diversity of urban spontaneous plants in Yunnan province. Our findings emphasize that urban spontaneous plants diversity is not only a reflection of the current state of urbanization, but also a consequence of historical processes of urbanization.

Occupancy models disentangle the drivers of avian urban avoidance in North America's largest urban forest

Urbanization dramatically modifies natural landscapes, fragments previously intact habitats, and is spreading rapidly, making it one of the leading causes of worldwide biodiversity decline. We studied the impact of urbanization on the occupancy of breeding birds in the Great Trinity Forest in Dallas, TX, the largest urban forest in the United States. The matrix of habitat surrounding the Great Trinity Forest varies from highly urbanized industrial landscapes to more rural areas. Between May 15th and July 15th of 2018, 2019, and 2020 we surveyed 404 5-ha plots for forest birds, recording 4274 observations representing 49 species. We used time-to-detection to model avian occupancy in 17 species while accounting for false absences. We found that the avian community responded to anthropogenic impacts of urbanization in the matrix in diverse ways. Urbanization intensity had the largest negative impact on avian occupancy and best explained observed patterns of urban avoidance from previous studies. Occupancy of species with low vocal frequency was negatively impacted by continuous anthropogenic noise from automobile traffic, while a broader group of species was negatively impacted by intermittent noise from airplane traffic. Occupancy exhibited both positive and negative responses to increased feral hog activity. To maintain diverse bird communities in forest fragments with a heavily urbanized matrix, it may be necessary to maintain large habitat tracts and mitigate for the indirect effects of the matrix like noise and invasive species.