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.     

The pattern of distribution and diversity of avifauna over an urbanizing tropical landscape

An investigation was done to determine the occurrence and composition of avian fauna community in the urbanizing city of Nairobi, Kenya. We conducted bird counts in sample sites randomly distributed over the Nairobi landscape within a two-year period. The proportion of seven different land cover types derived from within a 500 m radius of classified satellite image described the habitat condition of each sample site. Multivariate analysis of the site and species data indicated that savannah vegetation, forest and agriculture land cover types were the main environmental gradients that differentiated the sample sites. Four clusters of sample sites occurred on the ordination plane according to canonical correspondence analysis (CCA). From 50 families of birds observed, species related to bush and scrub habitats occurred at a rate of about 31 %, followed by grassland species at 20 % and forest species at about 16 % rate. Out of CCA, five functional groups of birds were distinguishable. The proportion of sites occupied by birds per functional group and mean count of individual birds declined significantly, p?<?0.0001, as groups of birds changed from being urban-related to savannah and then to forest-related species. One cluster comprised birds marked as having conservation concern status and related mainly to savannah vegetation of scrub and grasslands. In this landscape context, features such as native savannah vegetation and woodland accompanied by a process of controlled land use, could greatly mitigate negative impacts of ecosystem degradation on the sensitive tropical urban bird biodiversity.     

The effects of landscape scale on greenery and traffic relationships with urban birds and butterflies

Actions and policies to enhance biodiversity in the urban landscape must match the spatial scale at which biodiversity responds to the management and target variables. To this end, we compare the importance and effect of different kinds of greenery cover and road-lane density on bird and butterfly species richness between two landscape scales: 50-m versus 126-m radii around point counts (equivalent to areas of 0.8 h and 5 ha, respectively). We also compared the results against those of an earlier study using 500-m walking transects with widths of 100 m (i.e., 5 ha). Road lane density was more important at the 126-m than 50-m radius for both birds and butterflies. For birds, natural vegetation or forest cover and cultivated shrub cover were also more important at 126-m radius whereas the cultivated tree canopy cover was more important at 50-m radius. Cultivated tree cover and natural vegetation or forest cover were positively associated with species richness while road lane density and cultivated shrub cover were negatively associated with species richness. The results from point counts generally corroborate the results from the transects-based study, except that the short-duration point counts performed poorly in sampling butterflies. Our results indicate that in designing urban greenery policy, the plot sizes of individual developments is an appropriate spatial scale for the stipulation of tree cover targets, while urban planners have more flexibility to allocate natural greenery at broader spatial scales.

     

Forest cover is important across multiple scales for bird communities in vacant lots

Urban vacant lots can vary considerably in their vegetation structure, from dense, shrubby habitats to wooded remnant fragments that may provide habitat for a variety of birds. By identifying which features promote diverse bird communities, we can determine at which scale management practices should focus and the necessary habitat structure and composition features. We surveyed 150 vacant lots throughout Baltimore, Maryland for their bird communities, lot vegetation, and landscape-level forest cover. An ordination of the bird community indicated a response to a gradient of canopy cover and canopy height at the vacant lot. We also found that forest cover within 100 m of the vacant lot was the most important predictor of abundance for five bird species of interest. Species richness was spatially autocorrelated among sites, indicating that bird communities may also be driven by species’ dispersal and environmental gradients across the city. Overall, bird communities are responding to habitat features across multiple scales, from the vacant lot vegetation, to landscape-level forest cover, to city-wide dynamics. Thus, we recommend management practices to focus on increasing city-wide forest cover in order to increase species richness, yet with awareness regarding where the lot occurs within the city.     

Influence of habitat type and distance from source area on bird taxonomic and functional diversity in a Neotropical megacity

The Neotropical region has been subjected to massive urbanization, which poses high risks for some global biodiversity hotspots and losses of ecosystem functions and services. In this study, we investigate how distance from large patches of native forests (source areas) and vegetation (green)/and infrastructure (gray) characteristics affect bird species richness and functional diversity in São Paulo megacity, southeastern Brazil. We analyzed the effects of source areas and green/gray characteristics on species richness and functional diversity (richness, evenness, and divergence) indices. We detected 231 bird species, and our data confirmed our predictions: (1) bird species richness in urbanized habitats was found to be (~?50–85%) lower than in source habitats; (2) species richness and trait composition significantly decreased as the distance from the source area increased, while functional richness was not affected by this metric; and (3) shrub and herbaceous covers and maximum height of trees were positively correlated with species richness and unique functional traits regarding habitat, diet, foraging and nesting strata and dispersal ability of birds in the forest-urban matrix. The number of buildings was negatively correlated with bird species richness and functional richness. Maximum height of buildings caused dramatic declines in functional evenness. Functional divergence was notably lower in sites with high shrub cover. Our study stresses the complexity of vegetation embedded in large Neotropical urban settlements and the need to maintain large protected areas surrounding megacities to mitigate the impacts of urbanization on birds.

     

Reducing management intensity and isolation as promising tools to enhance ground-dwelling arthropod diversity in urban grasslands

Urbanisation is a growing global phenomenon having multiple ecological consequences. However, the effects of urbanisation on biodiversity remain ambiguous, and some evidence exists that cities provide valuable secondary habitats for many species, possibly mitigating regional biodiversity loss. Therefore, the value of urban sites for biodiversity depends on local habitat conditions and the configuration of the surrounding landscape. We aimed to disentangle the effects of local habitat parameters (management, plant diversity) and urban matrix variables (urbanisation, isolation) on carabid beetle and spider diversity and traits in informal urban green spaces in Berlin, Germany. Habitat management and isolation were the most important influences on carabid beetle and spider species and trait compositions. Spider communities of irregular managed sites contained 2.5 times more species of conservation concern than extensive (regular) managed sites. Moreover, irregular managed sites contained larger species (both for carabid beetles and spiders) and affected the hunting mode of spiders. Isolated sites tended to have lower spider species richness and number of spider species of conservation concern. Moreover, isolated sites were characterised by small, mobile and herbivorous carabid beetles. In contrast, urbanisation and local plant diversity had no effect on carabid beetles and spiders. We conclude that urban grasslands within residential areas – even if not targeted for conservation plans – can provide important habitats for conserving biodiversity, including species of conservation concern. Reducing the intensity of habitat management and increasing the connectivity of urban grassland sites can promote diverse arthropod communities and should therefore be considered in urban planning.     

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.     

Bird diversity of greenspaces in the densely developed city centre of Taipei

Urban greenspaces harbouring many species in cities are vital planning objects for enhancing biodiversity. Seeking to optimise ecological values of urban greenspaces, this paper explores 1. Bird composition by feeding and foraging characteristics in urban greenspaces located in densely developed central districts of Taipei City; and 2. Important features of greenspaces and underlying built environments that influence bird abundance, species richness, and diversity. Results show that the majority of birds found in the study sites are omnivorous and ground foragers; whereas birds relying on water/wetland habitats for feeding and foraging are relatively small in population and species richness. This suggests water/wetland associated environments and birds might be negatively impacted by urbanisation. Secondly, bird richness and diversity increase in accordance with greenspace size, water area, and habitat heterogeneity, but little relationship is found with greenspace structure, such as greenspace shape, distance to nearest greenspaces, and proximity to source patches of mountains and rivers. Also, no significant influence is observed from development intensity, which is measured by NDBI, and building height at greenspace surroundings. According to this result, this study suggests conservation of large greenspaces as a priority strategy for enhancing urban biodiversity. The development of land should take its potential ecological value into account while assessing environmental impact. For enhancing habitat quality of existing urban greenspaces, creating water bodies and increasing habitat types can be effective methods. Yet current planning strategies to increase street greenery and to connect urban greenspaces with surrounding mountains and rivers might only benefit specific urban exploiters or adaptors and result in little overall effect on richness and diversity.

     

What shapes plant and animal diversity on urban golf courses?

Recent concern over increasing loss of biodiversity has prompted considerable interest in the role of urban green spaces as reservoirs of local biodiversity. This study assessed the diversity of three indicator taxa - plants, ants and birds - on golf courses spanning a wide range of environmental variation in terms of climate, elevation, course age, size and connectivity to native woodland. Species richness and community composition was further compared between contrasting on-course habitat types that reflect different management intensities. We identified a set of taxon-specific environmental correlates indicating an intricate interplay of landscape- and local-scale variables that affect local species diversity. Our results show that floristic diversity is positively associated with the amount of rainfall, whereas ant and bird diversity are related to local-scale factors, particularly the number of trees and the size of water features on a site. The amount of on-course native habitat was a strong predictor of plant and ant diversity and was also associated with the number of unique species at the site level; this reinforces the value of remnant habitat patches as local biodiversity reservoirs that represent mini hot-spots in an otherwise species-poor urban landscape. Community composition for all three taxa differed markedly between non-playing and playing areas, with boundary and remnant habitats generally having more diverse, species-rich communities. Our results suggest that local floral and faunal biodiversity on urban golf courses can be enhanced by creating woody non-playing areas and, especially, by preserving, restoring or expanding remnant habitats.     

Bird and butterfly communities associated with two types of urban riparian areas

We examined the distribution of birds and butterflies at two types of urban riparian areas in the metropolitan area of Denver, Colorado, USA. The sites consisted of relatively natural areas containing native woody vegetation, and those that had been highly modified with trees and shrubs removed and planted with lawn grass. Species richness of both butterflies and birds differed significantly between the two types of sites. Species richness, however, was not significantly correlated between birds and butterflies. Bird abundance was similar between site types but consisted of two assemblages. Brewer's blackbirds, common grackles, bank swallows, and mourning doves were abundant at wooded sites while American robins, European starlings, house sparrows, house finches, and mallards were more abundant at lawned riparian sites. Butterfly abundance was less at lawned sites. This contrast in bird and butterfly response to habitats suggests they respond to different habitats in distinct ways. Both taxon groups, however, were important discriminators between habitat types. Overall, butterfly and bird species richness was 44% less at highly modified riparian sites.     

Relation between green spaces and bird community structure in an urban area in Southeast Brazil

Increased urbanization typically leads to an increase in abundance of a few species and a reduction in bird species richness. Understanding the structure of biotic communities in urban areas will allow us to propose management techniques and to decrease conflicts between wild species and human beings. The objective of this study was to describe the structure of the bird community in an urban ecosystem. The study was carried out in the city of Taubaté in southeastern Brazil. Point-counts were established in areas with different levels of tree density ranging from urban green spaces to predominantly built-up areas. We looked for a correlation between the richness/abundance of birds and the size of the area surveyed, the number of houses, the number of tree species and the number of individual trees. The results of multiple regression showed that bird richness had a direct relationship with vegetation complexity. The abundance and diversity of tree species were better predictors of bird species than the number of houses and size of the area surveyed. We discuss implications of this study for conservation and management of bird diversity in urban areas, such as the need to increase green areas containing a large diversity of native plant species.     

Woody plant species richness,composition and structure in urban sacred sites,Grahamstown, South Africa

Sacred sites are important not only for their traditional, spiritual or religious significance, but may also potentially be valuable for biodiversity conservation in human transformed landscapes. Yet, there has been little consideration of sacred sites in urban areas in this respect. Consequently, to better understand the ecosystem service and conservation value of urban sacred sites, inventories of their floral communities are needed. We examined the richness, composition and structure of the trees and shrubs in 35 urban churchyards and cemeteries in the City of Saints (Grahamstown). The combined area of urban sacred sites (38.7 ha) represented 2.2% of the city area and 13.6% of the public green space area. Species richness of woody plants was high, albeit dominated by non-native species. Levels of similarity among sites were low, indicating the effects of individual management regimens. There was no relationship between age of the site and measured attributes of the vegetation, nor were there any significant differences in vegetation among different religious denominations. However, the basal area and number of woody plants was significantly related to site size. These results indicate the significant heterogeneity of urban sacred sites as green spaces within the urban matrix. The significance of this heterogeneity in providing ecosystem services to users of sacred sites and the broader urban communities requires further investigation.     

The influence of small urban parks characteristics on bird diversity: A case study of Petaling Jaya,Malaysia

The capacity of small urban park to serve as urban habitats are rarely explored. This study analyses the characteristics of small urban parks and their potential to support urban biodiversity and ecological functions. Nine small urban parks were studied in Malaysia in August and September 2014 using the combined field survey method of structured observation and field measurements. The measured variables were divided into three broad categories of physical characteristics, species richness and human factors. Bird species richness and abundance were used as the indicators for assessing biodiversity. Pearson correlations and multiple regressions were conducted to analyse the relationships between variables and to identify which variables had a significant effect on bird species richness and abundance. The results demonstrated that park area and vegetation variables ( e.g. the percentage of tree canopy cover, open grass/ground, native-exotic plants) are the important predictors of bird species richness and abundance. The percentage of canopy covers (negative relation) and park area (positive relation) are the best predictors of bird species richness in small urban parks. Meanwhile, the best predictors for bird abundance are the percentage of canopy covers (negative relation) and native vegetation species (positive relation). Human activities and park surroundings have a marginal effect on the presence of bird species in small parks. Based on the findings, we provide two general recommendations that could probably increase bird diversity in small urban parks: (1) the park development and management plan should incorporate a social-ecological approach that can benefit both city-dwellers and bird species, and (2) findings from the study should be used to rethink the planting design and composition of especially newly established small urban parks.     

Legacy effect of trees in the heritage landscape of a peri-urban golf course

Negative environmental impacts of golf courses have received more attention than positive ecological contributions. We studied the mature tree communities and their legacy effect in a historical urban-fringe golf-course site in Hong Kong covering 170-ha with well-managed natural-cum-cultural landscape. Some 44.3 % of the site is covered mainly by large trees forming a mature peri-urban forest. The 94 species in 35 families offer a high species diversity exceeding local secondary and climax fengshui woodlands with notable rare and protected species. Tree species composition, richness and legacy effects brought by anthropogenic and natural factors were investigated by three habitats with varying naturalness and three golf courses with different age. Landscape zone is remarkably heterogeneous versus other microhabitats (fairway and woodland) and the heterogeneity of tree communities amongst the three courses is relatively weak. Synergistic operation of natural regeneration (natural legacy effect) and anthropogenic management (anthropogenic legacy effect) has fostered diversity accumulation. On the one hand, temporal changes in landscape fashion through a century and variations in site management have driven and maintained species diversity. On the other hand, the founder effect of inherited and cultivated species, as well as successful invasion and establishment of native species, have imposed floristic imprint and inertia on woodland habitat. The findings suggested that urban golf courses can serve as potential hotspots for biodiversity conservation within urban ecosystems.     

Diversity,abundance, and species composition of ants in urban green spaces

Urbanization threatens biodiversity, yet the number and scope of studies on urban arthropod biodiversity are relatively limited. We sampled ant communities in three urban habitats (forest remnants, community gardens, vacant lots) in Detroit and Toledo, USA, to compare species richness, abundance, and species composition. We measured 24 site characteristics to examine relationships between richness and composition and habitat patch size, vegetation, and urban features. Ant richness was higher in forests (26) than in gardens (14) and intermediate in vacant lots (20). Ant richness in gardens and vacant lots negatively correlated with abundance of an exotic ant species (Tetramorium caespitum); thus this ant may affect native ant richness in urban habitats. Ant composition differed with habitat type, and abundance was lowest in forests. Site characteristics varied with habitat type: forests were larger, had more woody plants, higher woody plant richness, more branches, and leaf litter whereas lots and gardens had more concrete and buildings. Vacant lots had taller herbaceous vegetation, and gardens had higher forb richness, density, and more bare ground. Differences in vegetation did not correlate with ant richness, but several vegetation factors (e.g. patch size, number and size of trees, leaf litter, and amount of concrete and buildings) correlated with differences in ant species composition. Additional factors relating to soil, nests, or microclimatic factors may also be important for urban ant communities. Implications for biodiversity conservation in urban ecosystems are discussed.     

Habitat type,food resources,noise and light pollution explain the species composition,abundance and stability of a winter bird assemblage in an urban environment

At present, urban areas cover almost 3% of the Earth’s terrestrial area, and this proportion is constantly increasing. Although urbanization leads to a decline in biodiversity, at the same time it creates extensive habitats that are exploited by an assemblage of organisms, including birds. The species composition and density of birds nesting in towns and cities are determined by the types of buildings, the structure and maturity of urban greenery, and habitat diversity. In contrast, the habitat traits shaping the community of birds wintering in urban areas are not known. The aim of this work was to assess the influence of habitat structure, food resources and the urban effects (pollution, noise, artificial light) on an assemblage of birds overwintering in an urban area. It was carried out in 2014 and 2015 in the city of Kraków (southern Poland), on 56 randomly chosen sample plots, in which the composition, density and interseasonal similarity of bird assemblage were assessed with line transect method. A total of 64 bird species (mean = 17.7 ± 4.9 SD species/plot) was recorded. The mean density was 89.6 ind./km ±63.3 SD. The most numerous species were Great Tit Parus major, Magpie Pica pica, Blackbird Turdus merula, Blue Tit Cyanistes caeruleus, Rook Corvus frugilegus, Fieldfare Turdus pilaris and House Sparrow Passer domesticus. Noise adversely affected species numbers and density, but artificial light acted positively on the density of birds and their interseasonal stability. The species richness and density of birds were also determined by the number of food sources available (e.g. bird-feeders). In addition, the greater the proportion of open areas, the fewer species were recorded. In contrast, the more urban greenery there was, the greater the density of the entire bird assemblage. Urban infrastructure (buildings, roads, refuse tips) had a positive effect on the interseasonal stabilization of the species composition of wintering birds. The results of this work indicate that the urban effect, i.e. noise and light pollution, apart from purely habitat factors, provide a good explanation for the species richness, density and stability of bird assemblage wintering in urban areas.     

Nest selection by red-headed woodpeckers across three spatial scales in an urban environment

Forest habitat is important for a variety of woodpecker species, and is under pressure from urbanization. Red-headed Woodpeckers (Melanerpes erythrocephalus; RHWO) were once abundant across Eastern North America, and their populations have been declining since the 1960s. Their distribution encompasses urban centers, and since urban habitats differ from natural forest areas, our goal was to understand RHWO nest-site selection in an urban context. We addressed two main questions 1) what are the characteristics of RHWO nest selection across multiple spatial scales and 2) how do RHWO nest tree characteristics in city parks compare to those in forest preserves? This work was done in Cook County, IL, which includes Chicago, the third-largest city in the USA by population. We examined 34 RHWO nest trees used between 2010 and 2013, their surrounding habitat, and the landscape within a 1 km radius. Used trees and habitats were compared to paired unused trees and habitats, and landscape-scale characteristics were compared to random locations. Advanced decay of the nest tree, low canopy cover and increased presence of fungus on trees in the surrounding habitat were the best predictors of RHWO nesting in the area. Nests were most commonly found in forested areas outside of dense urban areas. However, we did not detect significant differences in the characteristics of the nest trees located in forest preserves and city parks. Our findings are consistent with nest selection studies in rural and natural areas, suggesting that forest habitats in metropolitan landscapes can support RHWO nesting.     

Urban biodiversity: comparison of insect assemblages on native and non-native trees

Trees are thought to be important for supporting urban biodiversity. However tree species differ considerably in the numbers of invertebrates they support, with potential consequences for higher trophic groups such as birds. In this study the influence of native and non-native trees on the abundance of insects (Hemiptera) and the incidence of insectivorous birds (Paridae) were investigated in the southern English town of Bracknell. The number and species of tree were recorded from each of 17 roundabout and parkland sites. Tree beating was used to sample arboreal Hemiptera and Paridae were recorded either with point counts and transect walks, depending on the size of the site. Due to the great variation between tree species, there was no overall significant difference in species richness or abundance of Hemiptera between native and non-native tree species. However, individual native trees had more species and individuals than non-natives. The proportion of native trees at Bracknell sites was positively related to the abundance of both Hemiptera and the number of Paridae observed. The consequences of vegetation type for insect abundance indicates that in order to sustain and enhance urban biodiversity, careful consideration needs to be given to species of trees present in urban areas.     

Influence of urban landscape structure on bird fauna: a case study across seasons in the city of Valencia (Spain)

Studies on bird fauna of urban environments have had a long history, but the potential of studies mapping the distribution of birds in cities probably has not fully developed. The bird fauna of the municipality of Valencia (Spain) was studied to determine the influence of urbanization on bird species richness and abundance. Birds were censused during winter and the breeding season of years 1997–1998 in 197 squares measuring 49 ha each from a rural and an urbanized area. Across seasons the number of species decreased around 40% in the city compared with the rural landscape surrounding it. Such pattern could be attributed to the low number of farmland species capable to use the habitats inside the city, and the limited ability of urban parks in attracting woodland species. In the urban landscape, the influence of the dimensions and spatial arrangement of habitat patches was outweighed by the amount of each habitat per square. Bird richness and the abundance of most species were negatively related with the amount of built-up habitat per square and positively with the amount of urban parks, and of habitat diversity. Conversely, bird fauna was largely independent of mean park size per square especially during winter, indicating that at the landscape scale even small patches of habitat could play an ecological role. Conservation of urban bird diversity could benefit of two complementary strategies: (i) the protection of the surrounding rural landscape from urban development; (ii) habitat enhancement within the city. Particularly, a proper design and habitat management of urban parks could improve their suitability for urban bird fauna.