Habitat richness and tree species richness of roundabouts: effects on site selection and the prevalence of arboreal caterpillars

This study examined the relationship between the habitat and tree species richness of roundabouts and the abundance and species richness of tree-dwelling caterpillars, and thus the potential of urban roundabouts to support breeding populations. Total tree species number on sites was related to an increase in caterpillar abundance and a greater number of habitats was associated with a higher number of caterpillar species. An increase in the total number of trees was not correlated with a greater abundance of tree-feeding Lepidoptera; nor were native trees found to support proportionally more caterpillar species than all tree species, including introduced. This could be due to differences in species accumulation, the prevalence of generalist species or a statistical sampling effect. The occupancy and average abundance of caterpillar species was generally low, which does not support the theory that Lepidoptera in urban areas tend towards mono-dominance. It may, however, represent the presence of ‘accidental’ species on roundabouts. Habitat management and planting to increase tree species diversity and density on roundabouts has the potential to increase the species diversity and abundance of arboreal Lepidoptera, and increase abundance of butterfly and moth urban populations.     

Biodiversity of the urban homegardens of São Luís city,Northeastern Brazil

There is a widely held notion that the increasing trend of urbanization accelerates loss of biodiversity and displaces native species. This study assessed the validity of this notion in the city of São Luís the capital of the state of Maranhão in the northeastern Brazil. The specific objectives of the study were to (1) assess plant and animal diversity of urban homegardens, (2) compare the diversity of homegardens in terms of origin of these species (exotic or indigenous to Brazil). We conducted a biodiversity survey in 40 randomly selected ‘quintais’ (hereafter called homegardens) from ten locations in the city of São Luis. We evaluated the species richness and diversity of various use categories of plant and animal species indigenous to Brazil as well as exotic species. A total of 186 species of plants in 68 families were recorded in the sampled homegradens. A total of 63 fruit tree species representing 34% of all tree species were found. Of these species, those indigenous to Brazil accounted for 58% of the cases, and this was significantly higher than the exotic species. Most of the species (60%) were indigenous to Brazil (wild and semi-wild domesticates), while the rest (40%) were exotic. A total of 42 species of vertebrates (mainly reptiles, birds and mammals) were also found in the homegardens, of which 47% were indigenous to Brazil. Some of the plant and animal species found in the homegardens are endangered species in their native habitats, suggesting that homegardens could provide a unique opportunity for their conservation and sustainable use. These species continue to play a vital role in the socioeconomic and ecological landscape of the city.     

Effects of urbanization on breeding birds in European towns: Impacts of species traits

Urbanization acts as a filter on bird species behavioral traits so that only few species can tolerate urban constraints. We analyzed how behavioral traits (nesting, feeding, and migratory habits) of breeding bird species affect their frequency of occurrence in the urban centers of 38 European towns. We used binary logistic regression analysis to predict the bird species traits belonging to each trait group. A total of 108 species (21% of the European breeding bird species) were found to breed in the European town centers. According to our broad-scale analyses the bird species most frequently breeding in town centers nest in buildings and/or buildings have diverse diets, in trees (40%) and are resident omnivores, or relied on seeds or fruits as their sources of food. However, almost all bird species also fed on arthropods (92%) during the breeding season. Only a few urban bird species bred on the ground. Four out of the studied 108 species were non-native and five species were predators. Our broad-scale results from Europe indicate that bird species with different behavioral traits can respond differently to urbanization. Bird species that nest in cavities/buildings have diverse diets, that benefit a resident way-of-life, may have an advantage in living and settling in European town centers. Our results from Europe may provide insights related to the development of bird assemblages in the urban core areas of the New World.     

Predicting tree species richness in urban forests

There has been an increasing interest in urban forests and the levels of biodiversity they contain. Currently there are no spatially explicit maps of tree species richness in urban areas. This research tests and identifies GIS and remote sensing metrics (climate, area, productivity, three-dimensional structure) hypothesized to be associated with species richness in native forests and identifies methods that can be applied to predict and map tree species richness in cities. We quantified tree species richness, floristic composition, and structure in 28 1-ha plots in the city of Los Angeles. Climate and remote sensing metrics from high-resolution aerial imagery (10 cm), QuickBird (60 cm), Landsat (30 m), MODIS (250 m), and airborne lidar (2 m) were collected for each plot. There were 1208 individual stems and 108 trees identified to species. Species richness ranged from 2 to 31 species per ha and averaged 17 species per ha. Tree canopy cover from QuickBird explained the highest portion of variance (54%) in tree species richness followed by NDVI from Landsat (42%). Tree species richness can be higher in residential urban forests than native forests in the United States. Spatially explicit species richness maps at 1 ha can be created and tested for cities in order to identify both hotspots and coldspots of tree species richness and changes in species richness over time.     

Species richness,phylogenetic and functional structure of bird communities in Chinese university campuses are associated with divergent variables

University campus is an important component of urban landscapes for biodiversity conservation. However, to our knowledge no study has quantitatively assessed the diversity and structure of bird communities in Chinese university campuses, especially from phylogenetic and functional perspectives. Here, for the first time we linked species richness, phylogenetic structure and body mass structure of campus bird communities with contemporary climate, glacial-interglacial climate change, altitudinal range, population density around campus, area and age of campus to test their associations. We found 393 bird species in 38 university campuses (29% of all Chinese bird species, two species are endangered, four species are vulnerable, and 33 species are near threatened). The variables significantly correlated with campus bird species richness, phylogenetic structure and body mass structure were altitudinal range and mean annual precipitation, glacial-interglacial anomaly in temperature, and altitudinal range, respectively. In particular, there were more species in steeper and wetter campuses, more young species clustered in campuses with stable glacial-interglacial climate, and more species with smaller body size in steeper campuses. Our study highlights the importance of considering both phylogenetic and functional information for biodiversity conservation in urban ecosystems.     

Ant dominance in urban areas

A survey was conducted to determine the distribution of dominant ants and factors that may influence their dominance in New Zealand cities. A new method of active ant trapping combining aspects of pitfall trapping and attraction to food baits was used to capture a sample of all ant species that attended baits. Fifty eight percent of the ant species present in New Zealand were recovered from 2202 traps, with multiple species catches in 245 traps. There was a strong latitudinal relationship in the distribution of ant species, with the proportion of native to introduced species increasing in favour of the native species as latitude increased (south). The presence of Linepithema humile, the Argentine ant, a numerically dominant species was associated with a significant reduction in the number of other ant species captured. With increased urbanisation, providing refugia at times of cool temperatures for warm temperate-sub tropical introduced ant species, their range may extend into the higher latitudes, further displacing native ants from New Zealand cities.     

Dynamics of ruderal species diversity under the rapid urbanization over the past half century in Harbin,Northeast China

Urbanization has resulted in obvious changes in plant species diversity. We analyzed the dynamics of ruderal species diversity in Harbin over the past half century using historical data collected in 1955 and data of the present spatial distribution in 2010–2011. The results show that, the number of ruderal species decreased from 611 to 175 with remarkable tendency of decreasing in perennial species and increasing in winter annual species in the past half century, which caused the shift of life form spectrum from perennial mono-dominant type to summer annual and perennial co-dominant type. Meanwhile, the proportion of tropical originated species increased and the proportion of temperate originated species decreased which were considered to relate with the increase of temperature in urban area during the past half century. Moreover, there was a distinct decrease of the proportion of aquatic and hygrophytic ruderal species while an increase of mesic and xeric ruderal species which suggested a drought trend in urban habitats that consistent with the change of land use characterized as decrease of natural water bodies and wetlands and increase of urban land. Comparison of ruderal species along urbanization gradient also got the similar results with the above results from analysis on temporal scales and confirmed the effect of urbanization on decreasing plant richness. Our results suggested that land use change combined with its effect on temperature and disturbance regimes in urban habitats preferred species with short life span, high drought tolerance, fast growth rates and high seed yields.     

Occurrence of breeding bird species in urban parks: Effects of park structure and broad-scale variables

Occurrences of breeding bird species in 54 urban parks were investigated in the city of Oulu in northern Finland. Park area, human activity, habitat, and landscape structure within a 9-ha square surrounding the study park were related to the bird species richness and occurrence of individual bird species. A total of 22 species was observed. The area of the park explained 39% of the variance of species richness. Seven species (wheatear [Oenanthe oenanthe], common rosefinch [Carpodacus erythrinus], garden warbler [Sylvia borin], lesser whitethroat [Sylvia curruca], linnet [Acanthis cannabina], redpoll [Carduelis flammea], and yellowhammer [Emberiza citrinella]) were not detected in parks of >0.75 ha. Species with lower area demands occurred closer to the town center than species with greater area requirements. Ground-nesting species were poor colonizers of urban parks, whereas high numbers of nest boxes in urban parks attracted many cavity-nesting species. The willow warbler (Phylloscopus trochilus) and the magpie (Pica pica) bred more often in unmanaged than in managed parks, probably because of the greater vegetation cover in unmanaged parks. Park structure variables were entered into models for 7 of the 12 most common bird species, whereas broad scale variables were entered into models for 6 of the 12 species. The number of adjacent buildings had a negative affect on three bird species (the willow warbler, hooded crow [Corvus corone cornix], and spotted flycatcher [Muscicapa striata]). The occurrence of breeding species in urban parks depends on the size of the park, park structure, and landscape structure outside the park.     

Bird species assemblages across a rural urban gradient around Kolkata,India

Urban development leads to changes in habitat structure and resource base. Bird communities are known to respond sharply to such changes. Our result from study of bird community along urbanization gradient around Kolkata metropolitan city clearly separated the urban bird community from the rural and rural 3 habitats in terms of species diversity and foraging groups. Rural and rural 3 sites had more number of rare species and higher percentage of unique species as compared to the urban habitats. Functional group analysis showed higher abundance of granivores in urban habitats and absence of insectivore and carnivorous species that were found in the rural and rural 3 habitats. The bird species assemblage along the gradient was significantly nested where bird species recorded in urban areas were subset of the species rich rural areas. There was no difference in individual counts between urban and rural habitats, therefore nullifying the hypothesis that rural areas are more species rich because of higher population size. Bird community in the urban areas was less even as compared to the rural areas due to the dominance of omnivorous guild. Bird diversity was negatively correlated to the density of house lots.     

Foraging in the tropics: relationships among species’ abundances,niche asymmetries and body condition in an urban avian assemblage

Two main theories attempt to explain species coexistence: the neutral theory considers all the species as equivalents so biodiversity is mainly regarded as a function of total available resources (i.e. niche expansion), while the niche theory stresses the relevance of differences in niche use between species (i.e. niche packing). The relative importance of these forces is under discussion and has been largely tested in natural ecosystems. However, few studies have addressed this issue in tropical-urban environments. In this work we studied niche overlap asymmetries among the most common urban resident birds, and the effect of habitat type on this pattern, in a subtropical location of South China (Nanning, Guangxi). We found differences in abundances and niche use among species and urban habitats (parks, streets and orchards). We also recorded strong asymmetries in niche use between species, which we divided into three categories: species with positive asymmetries, which showed highly specific niches and were able to exploit other species’ niches; species with neutral asymmetries, which showed high levels of niche overlap with the rest of species; and species with negative asymmetries, which showed low specificity in their niches and were unable to exploit other species’ niches. These differences in niche use correlated with differences in fat scores. Species from the first group showed higher fat scores than other two groups. Ultimately, niche asymmetries correlated with species’ body condition and mediated their differences in abundance, which supports the view that in this urban context niche theory is more appropriate than neutral theory.     

Do arid species use less water than mesic species in an irrigated common garden?

There is an increasing need to consider the water use of horticultural plants grown in arid and semi-arid garden settings. Species that originate from arid and semi-arid regions are often considered suitable for xeriscaping, but there have been relatively few direct measurements of important water relations parameters such as gas exchange, resistance to cavitation, and water use efficiency (WUE) in irrigated urban gardens. In this study, we compared plant gas exchange, cavitation resistance, and WUE in evergreen shrub species from arid, temperate, and tropical environments grown in an irrigated common garden environment. Contrary to expectations, arid and non-riparian species had greater transpiration rates than temperate and riparian species, and lower specific leaf area than tropical and riparian species. Temperate species had the highest WUE as measured with the isotopic composition of leaf soluble sugar. Cavitation resistance and maximum hydraulic conductivity were not different among species from different biomes. These results indicate that under well-watered conditions, species from temperate environments may use less water than species from arid environments. In addition, native habitat is not a strong predictor of resistance to cavitation, which has implications for plant responses to water stress and drought.     

The structure of a micro-bat community in relation to gradients of environmental variation in a tropical urban area

We investigated patterns of community structure (species composition, foraging activity, and nightly foraging patterns) of bats in relation to gradients of environmental variation in a tropical urban area. A total of 32 sites spread equally across eight habitat types were sampled in the city of Townsville, North Queensland, Australia. Each site was sampled on 3 non-consecutive occasions using automated AnaBat systems. Eleven species were confidently identified while a possible four more were identified only to the genus level. Ordination of environmental variables measured at these sites identified two distinct environmental gradients reflecting the degree of urbanisation and foliage density. With increasing urbanisation there was a decline in species richness and total foraging activity. We used regression trees to characterise foraging preferences of each species. This analysis suggested that only one species of Mormopterus was able to exploit the resources provided by urbanisation. This species foraged in areas with higher numbers of white streetlights. The remaining species of bats preferred to forage within close proximity to natural vegetation and with low numbers of streetlights. The density of vegetation in long-established suburbs did not substantially reverse the trend for urban areas to have fewer bat species than original habitats.     

Improving confidence in tree species selection for challenging urban sites: a role for leaf turgor loss

High species diversity is argued to be the most important requisite for a resilient urban forest. In spite of this, there are many cities in the northern hemisphere that have very limited species diversity within their tree population. Consequently, there is an immense risk to urban canopy cover, if these over-used species succumb to serious pests or pathogens. Recognition of this should motivate the use of less commonly used species. Analysis of plant traits, such as the leaf water potential at turgor loss (Ψ_P0), can provide useful insights into a species’ capacity to grow in warm and dry urban environments. Therefore, the aim of this study was to evaluate Ψ_P0 of 45 tree species, the majority of which are rare in urban environments. To help evaluate the potential for using Ψ_P0 data to support future decision-making, a survey of professionals engaged with establishing trees in urban environments was also used to assess the relationship between the measured Ψ_P0 and the perceived drought tolerance of selected species. This study demonstrates that Ψ_P0 gives strong evidence for a species’ capacity to tolerate dry growing conditions and is a trait that varies substantially across species. Furthermore, Ψ_P0 was shown to closely relate to the experience of professionals involved in establishing trees in urban environments, thus providing evidence of its practical significance. Use of plant traits, such as Ψ_P0, should, therefore, give those specifying trees confidence to recommend non-traditional species for challenging urban environments.     

Human land use as a driver of plant community composition in wetlands of the Chicago metropolitan region

Anthropogenic alteration of the landscape has facilitated plant community change and non-native species invasion in urban areas. We used species occurrence data from over 2000 wetlands within the Chicago metropolitan region to classify urban wetlands into community types and examined non-native species composition across community types. Non-native species were widespread across the region, occurring in over 99% of wetlands. On average, 35% of the plant species in individual wetlands were non-native. A single non-native species, Phalaris arundinacea, was present in 74% of wetlands. Six wetland community types were identified (wet meadows, marshes, forested wetlands, farmed wetlands/mudflats, roadside marshes, and an undetermined wetland type), with each having aggressively spreading non-natives amongst the most common plant species. We conducted canonical correspondence analysis to evaluate the contribution of surrounding land cover, roads, and location of wetlands to plant community composition in these wetlands, and found that similar changes to the landscape have resulted in similar combinations of native and non-native species. Differences in species composition reflected spatial gradients in land use from urban to rural areas across the region, as well as proximity to major roads. Anthropogenic drivers have resulted in profound and pervasive changes to wetland communities across the region, creating novel habitats and ultimately novel community types.     

Partitioning the effects of habitat fragmentation on rodent species richness in an urban landscape

Habitat fragmentation plays a major role in species extinction around the globe. Previous research has determined that species richness in fragments is affected by a number of characteristics. These include fragment age, size, and isolation, edge effects, vegetation coverage, habitat heterogeneity, and matrix content. Although most studies focused on one or a few of these characteristics, multiple characteristics work together to affect species richness, showing that the effects of habitat fragmentation are complex. The goal of our study was to partition the complex effects of habitat fragmentation by determining the direct, indirect, and cumulative effects of multiple habitat fragment characteristics on rodent species richness. In 2013, we determined rodent species richness in 25 habitat fragments within Thousand Oaks, California. In addition, we measured the following characteristics for each fragment: fragment age, area, isolation, shrub coverage, habitat heterogeneity, perimeter/area ratio, and percent non-urban buffer. Path Analysis was used to test the hypothesized model which described the direct, indirect, and cumulative effect of each habitat fragment characteristic on rodent species richness. Overall, the path model explained 67 % of the variation in rodent species richness among habitat fragments. Habitat heterogeneity had the greatest direct and total effect on rodent species richness. Fragment size had the next greatest total effect on rodent species richness but this was nearly entirely indirect through its influence on habitat heterogeneity, suggesting that large fragments containing the greatest diversity of habitats will support the most species. Our study shows that large habitat fragments support the greatest habitat diversity, which provides the highest likelihood of conserving rodent species richness in an urban landscape.     

The impact of mosses on the growth of neighbouring vascular plants,substrate temperature and evapotranspiration on an extensive green roof

Currently the majority of vegetation used on shallow extensive green roofs are species of Sedum, which are able to survive in the harsh green roof environment. While mosses frequently colonize green roofs in Europe, intentional planting of mosses on green roofs is less common, especially in North America. Mosses may contribute to the ecosystem services provided by green roofs, and may act as facilitators of vascular plants. This study examined the effect of three different moss species on soil temperature, water loss rates and the growth of neighbouring vascular plant species. Overall, the presence of mosses in this experiment impacted the neighbour species differently, suggesting that mosses are best used in particular species combinations. One species of grass showed a net benefit of moss neighbours, suggesting that facilitation may be operating. Mosses reduced soil temperature relative to bare substrates; net evapotranspiration of green roof modules planted with mosses varied depending on the identity of moss and neighbour species.     

Evaluating the distribution of invasive woody vegetation around riparian corridors in relation to land use

Invasive species have been causing important and irreversible impacts to native species and communities of ecosystems. They distort ecosystem functions by degrading forest lands, wetlands, and agricultural habitats and replace the native vegetation and reduce biodiversity, forest productivity, and suitable wildlife habitat. To address disturbances caused by invasive species occurrence, further information is needed regarding the occurrence, extent, and dispersal of invasive species and how land use may increase the spread of these species. The objective of this study was to find the frequency and dominance of three invasive species common to riparian areas of east Alabama: Ligustrum sinense (Chinese privet), Elaeagnus pungens (silverthorn), and Triadica sebifera (Chinese tallow tree). Surveys of these species in riparian forests in and around Auburn, Alabama were conducted to show the relative extent of these shrubs and their relation to urban land use. It was expected to see the highest levels of invasive species in the city center with decreasing levels radiating outward into rural areas. Another objective was how urban land use may affect the presence-absence and prevalence of these non-native plant species within study sites. The results showed that around the city center and suburban lands, cover of both Chinese privet and silverthorn tended to increase. In contrast, Chinese tallow tree density percent cover showed an opposite trend with landscapes close to city center often having slightly less cover. This study shows that urban land use may be an important association with distribution of invasive plant species.     

Which traits influence the frequency of plant species occurrence in urban habitat types?

Plants in cities must cope with various anthropogenic environments that differ from surrounding landscapes. Moreover, the differences in biotic and abiotic conditions among these habitats filter species with suitable traits and niche requirements. Here we aim to identify those attributes that promote species occurrence across and within urban habitat types of large cities. Species composition of spontaneously occurring vascular plant species was recorded in 1-ha plots in seven different urban habitat types in each of 32 European cities. Each species was characterized in terms of dispersal type, growth form, height, seed bank longevity, seed mass, selected leaf traits and ecological indicators including Ellenberg indicator values, Grime’s life strategies, and immigration pathways using information from available species-trait databases. For each species, total frequency of occurrence across all plots and habitat frequency of occurrence across plots of given habitat types were calculated and regression trees were used to relate them to traits and ecological indicators. The most frequently occurring species in the cities tended to be human-dispersed, nutrient-demanding plants that prefer drier to mesic soil conditions. These species do not possess the S-strategy and usually produce seeds of low mass forming short-term persistent seed banks. Habitat-specific responses were also revealed, indicating the effects of between- and within-habitat heterogeneity on trends in species performance in cities. Such patterns can be overlooked when differences in species occurrences in particular urban habitat types are not considered; thus, habitat-specific responses can resolve inconsistencies found when whole urban floras are analysed as a whole.     

Habitat origins and microhabitat preferences of urban plant species

Urban vegetation is commonly described as dominated by weedy species that are adapted to human disturbance. In this study, we determined the original (pre-agriculture) habitats of urban plant species sampled quantitatively in the spontaneous vegetation of a university campus in Halifax, Nova Scotia (eastern Canada). We sampled 11 distinct patch types corresponding to different built forms. Differences in vegetation among patch types were related in part to environmental variables such as soil moisture and light availability. The urban vegetation was dominated by species from rocky habitats such as cliffs and talus slopes, with lesser representation from grassland and floodplain habitats. When compared to a null model of species origins based on the global area and species richness of different original habitats, species from rock outcrops and grassland habitats were overrepresented in the urban vegetation. These results contrast with the received view that cities represented highly “unnatural” ecosystems: built form appears to replicate the habitat templates required by rock outcrop species. Urban ecological theory should incorporate the replication of habitat analogs by built forms in addition to the creation of ecologically novel habitats.