Effects of urbanization on Neotropical wasp and bee assemblages in a Brazilian metropolis

The rapid growth of cities in many parts of the world has stimulated an increasing number of ecological studies of urban environments. Here, 12 study sites in the city of Belo Horizonte (MG), southeastern Brazil, were compared to analyze the effects of habitat changes related to urbanization on the species richness and abundance of native wasps and bees. Two spatial scales were considered: large portions of the urban landscape (entire sites) and small areas within these sites (public squares). Overall, the abundance of advanced eusocial bees (i.e. stingless bees), which were the dominant species, was directly affected by the loss of vegetation cover and the increase of buildings associated with urbanization. The magnitude of this effect varied according to the nesting habits of each species. The loss of vegetation cover associated with urbanization also had a negative effect on the abundance and species richness of advanced eusocial wasps. Generalist species of bees and wasps, such as Trigona spinipes and Polybia occidentalis, were very abundant and not sensitive to the habitat changes related to urbanization. Advanced eusocial bees also responded to small-scale habitat changes (size and vegetation cover of public squares). No relation was found between the solitary and the primitive eusocial wasps and bees and the habitat changes considered here. Conservation strategies in urban environments need to consider different spatial scales in order to maintain or enhance the local diversity of wasps and bees.     

Back to Von Thunen: a Southern European perspective on mono-centric urban growth,economic structure and non-urban land decline*

This study assesses trends (1960–2010) in forest cover over a Mediterranean metropolitan region (Attica, Greece) with the aim to investigate the role of local contexts promoting changes in the use of land. Forest cover decreased in a spatially heterogeneous manner over the study period determining a land-use structure coherent with the Von Thunen mono-centric model. We used a multivariate exploratory analysis of 26 contextual variables to identify changes in the urban spatial structure at the local scale. The shift from a land-use structure based on urban–rural and cropland-forest polarizations in the early 1960s to a pattern based on the polarization in medium-density, mixed urban/agricultural areas and low-density, sparse forest land has been observed in the last 50 years. Urban expansion into rural land and the establishment of protected areas in economically marginal and remote districts has been identified as relevant drivers of landscape transformation in the area. Our study demonstrates that land-use changes driven by expansion of dispersed settlements may consolidate mono-centric urban structures. A concentric land-use distribution around the central city is compatible with urban sprawl and may be indirectly supported by ‘green belt’ regional planning and environmental policies protecting high-quality natural land.     

Long-term sodium and chloride surface water exports from the Dallas/Fort Worth region

Sodium and chloride in surface water are typically related to urbanization and population density and can have a significant impact on drinking water sources and the subsequent salinity of aquatic ecosystems. While the majority of research has focused on the impact of deicing salts on urban surface waters in colder climates, the effect of urbanization on sodium and chloride concentrations has been found to occur in warmer climates. This study investigated long-term exports of sodium and chloride from watersheds with increasing urbanization in the humid subtropical Dallas-Fort Worth region. We compared exports to characteristics of urbanization: urban land cover, impervious surface area, and calculated contributions from wastewater discharges. Long-term data (1980-2008) were obtained from five USGS gages located in and around the cities. Exports were calculated by regression analysis between concentrations and discharge and normalized for time and the watershed area. Grab samples were collected from June 2009 to May 2010 and sodium and chloride concentrations quantified. Our results show a strong positive relationship between the mean annual sodium and chloride exports from each watershed and the percent urban land cover and impervious surface area. Long-term increases in sodium and chloride fluxes were found for the three watersheds with the highest percentage of urban land cover. The single largest contributor was wastewater effluent that was estimated to contribute approximately half of the total loads in the three urbanized watersheds. Atmospheric deposition and deicing salts accounted for small amounts of the total export for urbanized watersheds. The source of the remaining salt load is still unknown and may be a combination of non-point sources. Estimates of urban salt exports were similar to estimates from northern watersheds affected by deicing salts.     

Scale-dependent habitat relations of birds in riparian corridors in an urbanizing landscape

As the amount of urbanization in the landscape surrounding a riparian zone increases, local riparian vegetation structure and composition change in complex ways. The impact of increasing urbanization on birds in and around riparian zones will depend on their differential sensitivity to local- versus landscape-scale habitat variation. Thus, our principal objective was to determine which spatial scale has a greater association with the distribution of each bird species using riparian corridors in a landscape mosaic comprised of anthropogenic land uses and undeveloped native shrublands in coastal southern California. We surveyed 137 points in riparian vegetation along an urbanization gradient, and used logistic regression and information theory to select best supported models describing the distribution of each of 52 bird species. Models based only on local-scale vegetation variables were best supported for 19 species, whereas landscape-scale (amount of urbanization within a 1000-m radius) models were best supported for 13. Ten species were best described by models combining local- and landscape-scale variables, and 10 had no well-supported models. Within guilds, woodland and riparian-dependent species appeared to respond to local vegetation variables whereas shrubland species appeared more sensitive to landscape context. Likewise, insectivores were more likely to be associated with variation in local-scale variables. In contrast to other studies, Neotropical migrants were not sensitive to increasing urbanization. Provided that local vegetation remains in good condition, our results suggest that riparian bird species may persist even in areas with extensive urbanization.     

Satellite based land use and landscape complexity indices as predictors for regional plant species diversity

It is known that habitats composed of spatially heterogeneous abiotic conditions provide a great diversity of potentially suitable niches for plant species. The scientific premises of landscape ecology suggest that, at a higher spatial level, also the composition and structure of the landscape mosaic, influences biotic processes and hence species richness. In this exploratory study we investigated if plant species diversity could be correlated with landscape structure and complexity indices which were based on Landsat Thematic Mapper satellite imagery. Plant species data were derived from the 4 km×4 km resolution Flora Database of Flanders (i.e. northern Belgium). Plant species number within the 4 km×4 km grid cells was positively correlated with most of the landscape diversity indices whereas landscape fragmentation indices only affected the group of the threatened species. We found a gradient of increasing species richness beginning from the rural areas of Flanders over the suburban towards the urban areas. This gradient was mostly due to the higher number of alien plant species, warmth indicators and threatened species in urbanised areas. We conclude that, at least in the studied region, the effects of landscape changes on plant species diversity can be monitored and predicted on a large scale and over long periods of time using land cover data. Bottleneck in this kind of analyses remains the reliability of the land cover data and the availability and reliability of the biological data.     

Assessing land-use effects on water quality, in-stream habitat, riparian ecosystems and biodiversity in Patagonian northwest streams

Changes in land-use practices have affected the integrity and quality of water resources worldwide. In Patagonia there is a strong concern about the ecological status of surface waters because these changes are rapidly occurring in the region. To test the hypothesis that greater intensity of land-use will have negative effects on water quality, stream habitat and biodiversity we assessed benthic macroinvertebrates, riparian/littoral invertebrates, fish and birds from the riparian corridor and environmental variables of 15 rivers (Patagonia) subjected to a gradient of land-use practices (non-managed native forest, managed native forest, pine plantations, pasture, urbanization). A total of 158 macroinvertebrate taxa, 105 riparian/littoral invertebrate taxa, 5 fish species, 34 bird species, and 15 aquatic plant species, were recorded considering all sites. Urban land-use produced the most significant changes in streams including physical features, conductivity, nutrients, habitat condition, riparian quality and invertebrate metrics. Pasture and managed native forest sites appeared in an intermediate situation. The highest values of fish and bird abundance and diversity were observed at disturbed sites; this might be explained by the opportunistic behavior displayed by these communities which let them take advantage of increased trophic resources in these environments. As expected, non-managed native forest sites showed the highest integrity of ecological conditions and also great biodiversity of benthic communities. Macroinvertebrate metrics that reflected good water quality were positively related to forest land cover and negatively related to urban and pasture land cover. However, by offering stream edge areas, pasture sites still supported rich communities of riparian/littoral invertebrates, increasing overall biodiversity. Macroinvertebrates were good indicators of land-use impact and water quality conditions and resulted useful tools to early alert of disturbances in streams. Fish and birds having a greater ability of dispersion and capacity to move quickly from disturbances would reflect changes at a higher scale.     

The contribution of the bark of isolated trees as habitat for ants in an urban landscape

Since urbanisation and fragmentation result in a decrease in larger forests, the importance of isolated trees as habitat in urban landscapes is increasing. This study investigated the contribution of trees in urban landscapes to the abundance and variety of arthropod taxa. Ants and other arthropods were surveyed on the bark of 341 trees in three types of arrangement: isolated trees, trees in linear corridors and trees in patches. Ant species and other arthropods were identified and the numbers on each tree were counted. In order to determine the effects of host tree properties (size and plant species) and the surrounding environment (arrangement of trees, surrounding land cover), an analysis of covariance was conducted. Tree species was the most important influence, followed by tree size, on ants and other arthropods in the urban landscape, with little effect from the arrangement of trees. Thus, in order to increase arthropod diversity in urban landscapes, it is important to select tree species that attract a large number of arthropod taxa.     

A fieldwork study on the diurnal changes of urban microclimate in four types of ground cover and urban heat island of Nanjing,China

Records of the past years showed that the climate of built-up regions differs significantly from rural regions and one of the most obvious and important modifying effects of urbanization on local climate is the urban heat island (UHI). In this paper, four types of land cover, namely urban bare concrete cover, urban woods or the shade of trees, urban water areas and urban lawn, were selected to study their microclimate, and the UHI was also analyzed using air temperature data measured at four fixed observation spots in Nanjing, China, during hot weather from July to September, 2005. Dry and wet bulb temperature data were obtained by whirling psychrometers, and wind speed data by cup anemometers. Our observed data focused on the detailed statistical analysis of the microclimate variation in the four types of land cover during the whole day. The results showed that: (1) the microclimate of these four types of land cover had significant differences among different observation sites. In general, the air temperature of these four types of land cover complied with the order during daytime: bare concrete cover>lawn>water areas>woods or the shade of trees, with reversed order during nighttime when the air temperature of the lawn became the lowest. Compared with the bare concrete cover, the other three types of land cover showed the effect of dropping air temperature ranging between 0.2 and 2.9 °C. There were some instant dynamic characteristics in detailed temporal series among these four types of cover in the different observation sites. (2) The UHI effect could be detected obviously by the air temperature difference between the urban center area and the rural area. The average UHI intensity during the monitoring period was between 0.5 and 3.5 °C; however, there were also significant day-to-day variations. A strong UHI effect usually occurred around midnight; while about 2–3 h after sunrise the UHI began to decrease till midday time; and during 13:00–15:00, the UHI effect had a sudden increase and then decreased again; after sunset, a peak UHI effect was frequently observed during 18:00–21:00. (3) Finally, by means of the standard deviation (SD), this paper provides a concise and comprehensive understanding for the temporal and spatial microclimatic dynamics of these four kinds of urban cover in the four observation sites. Air temperature at the height of 1.5 m in Nanjing showed that the nocturnally horizontal temperature gradient was somewhat different from that reported in other large cities, and a marked heterogeneity in a smaller ground cover scale could be detected from the microclimatic spatial pattern. There is no doubt that the analysis of these four types of land cover presents the insight into possible countermeasures to decrease the high air temperature in hot summers, and is relevant to the urban planning redevelopment.     

重庆市小城镇风貌特色规划的探讨

加快小城镇建设是统筹城乡发展、积极解决"三农"问题、推动城镇化进程的有效途径。而目前的快速发展中,重庆市小城镇传统的、具有差异性的城镇特色正逐渐缺失。该文通过对重庆市小城镇建设整体定位、风貌特色及规划体系建构的讨论,尝试提出较为系统的、具有可操作性的风貌规划策略,对小城镇建设与管理提供参照。     

Relationships between urbanization and the oak resource of the Minneapolis/St. Paul Metropolitan area from 1991 to 1998

Urbanization was associated with loss and transformation of the oak forest in the Twin Cities (Minneapolis and St. Paul) metropolitan area (TCMA) over a recent 7-year interval. Between 1991 and 1998, urbanization increased based on several indicators: population density, area of developed land, and area of impervious surface—total impervious area and area within three classes of increasing degree of imperviousness (protected, affected, and degraded). We quantified relationships between changes in urbanization and changes in several parameters describing the oak forest at the scale of ecological subsection. Increased total and affected impervious area were strongly correlated with decreased area of oak forest when changes of the urbanization indicators and oak were expressed as percentages of the subsection area. Relationships were reversed when changes were expressed as percentages of the 1991 values. Increased population density was strongly correlated with increased loss in numbers and increased isolation of oak patches, but weakly correlated with loss of oak forest area. This is the first study to quantify relationships between changes in urbanization and changes in a specific forest cover type. Our results demonstrate complexities of urbanization impacts on a metropolitan forest resource, and highlight the importance of selected variables, spatial and temporal scales, and expressions of change when quantifying these relationships.     

Thermal comfort implications of urbanization in a warm-humid city: the Colombo Metropolitan Region (CMR), Sri Lanka

In this paper we analyze the historic trends in thermal comfort (measured in terms of Temperature–Humidity Index [THI] and Relative Strain Index [RSI]) in the Sri Lankan primate city of Colombo and correlate them with land cover changes in the region. Land cover is calculated form time-series aerial photographs in terms of “hard” cover (buildings, paved areas and roads) and “soft” cover (trees, green areas and waterbodies). The period selected for analysis includes pre-rapid (up to 1977) and rapid urban phases (1978 onwards) in the city. Contemporary Sri Lanka's urbanization is peculiar in that mid to late 20th century urban rates (approx. 22% of the population) had remained virtually unchanged till the economy was liberalized in 1977, but have recently intensified (currently at about 35%). This offers a unique window of opportunity to look at the thermal comfort transition consequent to urbanization. Since many tropical cities are at a similar stage of demographic transition, lessons from Colombo may generally be applicable to other tropical developing cities as well.

An increasing trend in thermal discomfort—particularly at night—is seen especially at the suburban station and it correlates well with hard land cover changes. The study also brings out the relative importance of land cover in city center vs. rural areas (e.g. hard cover has more effect on thermal discomfort in city center than in rural areas). Based on these findings, we postulate an outline for a climate-sensitive urban design policy for tropical cities.     

Distribution and dynamics of birds in a rural sub-Mediterranean landscape

The richness and abundance of birds in a sub-Mediterranean rural landscape (north Italy, Massa Carrara Province) were investigated across two spatial scales (10 km × 10 km and 5 km × 5 km), two functional scales (land use mosaic and ecotope) and two temporal scales (annual and seasonal).Information on birds collected using the line transect method was compared with some landscape attributes (altitude, orientation, patch size, distance from cultivations).Distribution, abundance and seasonal turnover of birds were described efficiently by land use cover and ecotopes, but altitude, orientation, patch size and neighboring patch types were also important.Pure crop areas and crops mixed within woodlands and farming villages were the areas preferred by birds especially out of the breeding period, although woodlands supported more stable birds assemblages over the year. The multiscalar approach proposed was an efficient strategy to investigate these bird assemblages living in a patchy rural mosaic in which resources were made seasonally available by agricultural practices.The recent landscape change due to abandonment of agriculture in most of the sub-Mediterranean mountainous rural areas and the consequent woodland encroachment were expected to produce impoverishment of both diversity and abundance of resident and migratory birds.     

Do landscape factors affect brownfield carabid assemblages?

The carabid fauna of 28 derelict sites in the West Midlands (England) were sampled over the course of one growing season (April-October, 1999). The study aimed to investigate the relationship between carabid assemblages and five measures of landscape structure pertinent to derelict habitat. At each site measurements of landscape features pertinent to derelict habitat were made: (i) the proximity of habitat corridors; (ii) the density of surrounding derelict land; (iii) the distance between the site and the rural fringe; and (iv) the size of the site. Concurrent surveys of the soil characteristics, vegetation type, and land use history were conducted. The data were analysed using a combination of ordination (DCA, RDA), variance partitioning (using pRDA) and binary linear regression. The results suggest that: 1. There is very little evidence that the carabid assemblages of derelict sites were affected by landscape structure, with assemblages instead being principally related to within-site habitat variables, such as site age (since last disturbance), substrate type and vegetation community. 2. No evidence was found to support the hypothesis that sites away from railway corridors are impoverished in their carabid fauna than sites on corridors. 3. There are some suggestions from this study that rarer and non-flying specialist species may be affected by isolation, taking longer to reach sites. We infer from this that older sites with retarded succession, and sites in higher densities of surrounding derelict land may eventually become more species rich and that these sites may be important for maintaining populations of rarer and flightless species. 4. Conservation efforts to maintain populations of these species should focus principally on habitat quality issues, such as maintaining early successional habitats that have a diversity of seed producing annuals and perennial plants and enhancing substrate variability rather than landscape issues.     

Selecting independent measures to quantify Melbourne's urban–rural gradient

As cities and towns increase in population and size around the world, there is a growing interest in the impact of urbanisation on humans and the environment. The use of urban–rural gradients has proven to be a useful tool for studying changes in ecological patterns and processes across urbanising landscapes. Currently, there are a wide range of measures being used to represent changes in human demographic patterns, physical structures and landscape composition and structure along urban–rural gradients. The aim of this paper was to identify a suite of measures that can be used to define an urban–rural gradient in Melbourne, Australia. Using principal components analysis, we assessed 17 commonly used measures of urbanisation that included demographic variables, physical variables and landscape metrics. Four measures captured most of the variability in the patterns of urbanisation: (1) Index_combined; (2) the ratio of people per unit urban land cover; (3) landscape shape index; (4) dominant land-cover. We used these four measures to quantify Melbourne's urban–rural gradient and then explored their use in representing urbanisation as an environmental space rather than a geographic space. This study provides an example of how to objectively select a subset of measures to quantify urbanisation, and illustrates a novel way of combining the measures to obtain a richer understanding of ecological responses to urbanisation.     

首都地区城乡建设用地空间格局与增长趋势——基于2000-2010年数据

新型城镇化过程中城乡建设用地的永续利用和合理扩张是社会各界关注的热点问题,也是空间规划改革的重要内容.现有的研究往往从城镇扩张、土地非农化等角度分析建设用地的整体演变规律,对于用地结构、空间特征的关注往往不够.考虑到我国特殊的城乡二元土地制度,城镇和农村建设用地扩张相对独立,需要将两者统筹起来,分析城镇、农村和工矿建设用地各自空间格局和增长趋势的特征.选取我国城镇化较为迅速的首都地区作为研究对象,以2000-2010年间的空间数据为基础,从城乡建设用地的规模分布、结构比例、增长趋势、内部结构变化等几个方面总结其演变规律,并从空间管理、内部转换、政策工具三个方面给出建议.     

Does spatial configuration matter? Understanding the effects of land cover pattern on land surface temperature in urban landscapes

The effects of land cover composition on land surface temperature (LST) have been extensively documented. Few studies, however, have examined the effects of land cover configuration. This paper investigates the effects of both the composition and configuration of land cover features on LST in Baltimore, MD, USA, using correlation analyses and multiple linear regressions. Landsat ETM + image data were used to estimate LST. The composition and configuration of land cover features were measured by a series of landscape metrics, which were calculated based on a high-resolution land cover map with an overall accuracy of 92.3%. We found that the composition of land cover features is more important in determining LST than their configuration. The land cover feature that most significantly affects the magnitude of LST is the percent cover of buildings. In contrast, percent cover of woody vegetation is the most important factor mitigating UHI effects. However, the configuration of land cover features also matters. Holding composition constant, LST can be significantly increased or decreased by different spatial arrangements of land cover features. These results suggest that the impact of urbanization on UHI can be mitigated not only by balancing the relative amounts of various land cover features, but also by optimizing their spatial configuration. This research expands our scientific understanding of the effects of land cover pattern on UHI by explicitly quantifying the effects of configuration. In addition, it may provide important insights for urban planners and natural resources managers on mitigating the impact of urban development on UHI.     

基于深度学习的上海城市街景与景观 美学公众认知研究

随着中国城镇化转型与城市更新的开展,服务城市大众美学认知与文化精神的城市风貌与景观塑造成为当前的迫切需求。以上海典型街景为例,结合问卷调查、深度学习与贝叶斯统计方法,构建具大范围评估应用潜力的公众审美感知模型,进行公众景观偏好研究。发现公众对于街景的不同场景审美感知差异较大;景观美学感知概念模型中关键景观要素为土地、建筑、树、墙;想象度、自然度、对比度和审美干扰度是影响公众对景观美学认知的重要指标。研究结果可进一步推广到大规模公众景观认知快速评估,为城市设计提供本土公众偏好美学理论的信息支持。     

Spatio-temporal dynamics and evolution of land use change and landscape pattern in response to rapid urbanization

Analyzing spatio-temporal characteristics of land use change is essential for understanding and assessing ecological consequence of urbanization. More importantly, such analysis can provide basic information for appropriate decision-making. By integrating historical high spatial-resolution SPOT images and spatial metrics, this study explored the spatio-temporal dynamics and evolution of land use change and landscape pattern in response to the rapid urbanization process of a booming-developing city in China from 1996 to 2006. Accurate and consistent land use change information was first extracted by the change detection method proposed in this study. The changes of landscape pattern were then analyzed using a series of spatial metrics which were derived from FRAGSTATS software. The results indicated that the rapid urbanization process has brought about enormous land use changes and urban growth at an unprecedented scale and rate and, consequently, given rise to substantial impacts on the landscape pattern. Findings further revealed that cropland and water were the major land use types developed for urban sprawl. Meanwhile, the landscape pattern underwent fundamental transition from agricultural-land-use dominant landscape to urban-land-use dominant landscape spanning the 10 years. The results not only confirmed the applicability and effectiveness of the combined method of remote sensing and metrics, but also revealed notable spatio-temporal features of land use change and landscape pattern dynamics throughout the different time periods (1996–2000, 2000–2003 and 2003–2006).     

Multiscale analysis of the urbanization pattern of the Phoenix metropolitan landscape of USA: Time,space and thematic resolution

Investigating the ecological consequences of urbanization require knowledge of land-cover dynamics. Quantification of land-use/land-cover change in Phoenix, Arizona during the period of 1985–2005 using landscape metrics computed from Landsat-derived maps revealed temporal patterns of landscape composition and configuration. With accelerated urbanization the landscape as a whole became more fragmented ecologically and more complex compositionally and geometrically. However, the majority of individual patches became more compact in shape. Urban land covers, especially xeric residential, increased substantially and the desert decreased by 20%. Spatial and thematic resolution of data was shown to have large effects on the analysis of land-cover pattern. Our results, while agreeing in general with previously reported scaling relations with respect to changing spatial grain and extent, showed that scaling relations are also robust and consistent across thematic resolutions and time periods. Some metrics behaved unpredictably and some exhibited scale-free behavior. Compositional metrics, such as patch density, diversity, evenness, and largest patch index, were well correlated with vegetative cover, its spatial variation, and population density. Many of these correlations exhibited hump-shaped patterns with respect to increasing grain size, indicating a characteristic scale at approximately 500–1000 m. By simultaneously manipulating spatial and thematic resolutions, the importance of the Modifiable Area Unit Problem in relating landscape patterns to vegetation and socio-economic variables was also demonstrated. Additionally, highly variable desert vegetation due to precipitation variability poses a challenge for accurately quantifying urbanization pattern in arid environments. Choosing appropriate spatial, temporal and thematic resolutions is essential in meeting this challenge.     

环境景观格局对绿地冷岛效应的影响

城市绿地的自身特征和周围环境的景观格局可影响其冷岛效应.以上海市中心城区68个面积大于1hm2的绿地为研究对象,探讨绿地内外部的环境景观格局配置对其冷岛效应的影响,并得到以下结论:为增强一定面积绿地的冷岛效应,可通过提高绿地边界形态的复杂度、提高绿地内外部环境中水体斑块的面积、降低不透水面斑块面积或分散布置绿地内外部环...