Exotic plant invasions in forested wetlands: effects of adjacent urban land use type

There are a variety of land use types in urbanized areas that may have different effects on the ecological characteristics of patches of natural vegetation. In particular, residential housing and industrial land-use may have different effects on adjacent forest communities. We tested this hypothesis by examining the vegetation of forested wetlands in a densely urban region, northeastern New Jersey. Wetlands embedded in industrial areas were much less invaded by exotic plant species than were wetlands embedded in residential areas, as reflected in the number of exotic species, the fraction of the total flora that was exotic, and their frequencies of occurrence. Few other structural characteristics of the vegetation differed between the two types of urban areas. We suggest that the management of land adjacent to forest edges may explain this surprising result. The low rate of invasion of wetlands within industrial areas suggests they could have high conservation value in urban ecosystems.     

Relationship of bird richness,abundance and assemblage to the built environment in a small island tropical urban setting: a Suva,Fiji case study

There have been few studies investigating the relationship between the built environment and the status of bird distributions in small island tropical urban areas. We present a study investigating the relationship between bird species richness, abundance and assemblage to the built environment in Suva, Fiji. Field surveys were taken at 54 randomly selected sites throughout the city, stratified by three building density classes and the central business district (CBD). At each site bird counts were recorded, along with environmental data such as average building height, within a 150 m radius. Land-use information was obtained from screen digitized high-resolution satellite imagery within the same radius. Distance to undeveloped patches of land within the urban area was calculated using a GIS. Analysis of the effects of the built environment was carried out for all species, and for exotic and native species separately. Abundance of exotics was significantly higher in the central business district (CBD) than all other urban density classes, and significantly higher than natives in all other density classes. We found a negative relationship between native species richness and distance to undeveloped patches, but no relationship for exotics. Species assemblage was not related to urban density class. We conclude that the status of native and exotic bird species in Suva is similar to what has been found in urban areas in temperate climates, and conservation efforts should focus on minimizing the amount of heavily urbanized “core areas” and protecting undeveloped areas of forested vegetation to improve bird biodiversity in small tropical islands cities.

     

Functional connectivity in urban landscapes promoted by <Emphasis Type="Italic">Ramphastos toco</Emphasis> (Toco Toucan) and its implications for policy making

The scarcity of green areas in urban landscapes hinders connectivity among sites reducing the flux of organisms and seed dispersal. Ramphastos toco is an effective plant disperser in tropical landscapes, playing an important role in conserving plant connectivity. In this study we combined two methods of landscape connectivity analysis, in a way not yet explored, to assess the potential contribution of Ramphastos toco to enhancing connectivity among urban vegetation patches. We used spatial modeling techniques to evaluate least cost routes, or those that facilitate bird movement through green urban areas, in Belo Horizonte, a city in Southeast Brazil. We also assessed the relative importance of forest patches for conserving both bird and seed dispersal fluxes using the integral index of connectivity. The resulting least cost route of greater accessibility for the species included in its course an important forest patch under environmental licensing for the construction of a residential condominium. The number of green urban areas covered by forest, of highest habitat quality for the species, summed to 155 patches. Of this total only 5.2% were relevant for regional connectivity, while the four most important patches are targeted by the city’s expansion plans. Ramphastos toco is an effective connector for tropical green urban areas given its adaptability, wide range of movement and seed dispersal effectiveness. We emphasize the need for incorporating ecological knowledge and the prioritization of green areas into city planning, since current expansion projects jeopardize forest patches that are crucial to the functional connectivity of the urban landscape.     

Frugivory and habitat use by thrushes (Turdus spp.) in a suburban area in south Brazil

Thrushes (Turdus spp., Turdidae) are among the most common frugivorous birds in urban areas around the world, where they disperse the seeds of a variety of plant species. We studied the abundance, habitat use, foraging behavior and diet of four thrush species (Turdus rufiventris, T. amaurochalinus, T. leucomelas, and T. albicollis) in a suburban area in south Brazil. Abundance, habitat use and foraging behavior were based on birds surveyed along a 3,240 m transect crossing open (formed by lawns, streets, and buildings) and forested areas. Diet was based on fecal samples collected from mist-netted birds. Turdus rufiventris was the most abundant species, followed by T. amaurochalinus, T. leucomelas, and T. albicollis. All species used forest fragments more frequently than expected by chance. A total of 91.8% (n = 147) of the fecal samples contained fruit remains, while 42.2% contained only animal matter. Most of the foraging records were on the ground, where birds got mainly invertebrates. Fruits and invertebrates were eaten more frequently in open than in forested areas. A total of 25 seed morfospecies were found in the droppings, including five exotic plant species. Thrushes overlapped widely in the fruit composition of their diets. The high abundance and degree of frugivory, coupled with the frequent use of forest patches, indicate that thrushes are among the great bird contributors to the seed dispersal occurring in urban forest patches, potentially influencing the vegetation dynamics of such habitats so important for the maintenance of the biodiversity in urban areas.     

Effects of long-term landscape dynamics and city growth on biodiversity in the Mediterranean: the case study of Montpellier,France

In the Mediterranean, long-term land-use changes have resulted into landscape mosaics composed of very few ancient woodland remnants scattered across extended post-agricultural woodlands. Patches of ancient woodlands are now suffering rapid urban growth that reduces their area and impact their associated biodiversity. Here we use the case study of Montpellier, one of the most dynamic cities in France, to 1) characterize temporal changes in land covers (between 1860 and 2006) in its area, and 2) using two guilds of fungal bioindicators (i.e., polypores and lichens), to compare biodiversity stakes between ancient and secondary Mediterranean woodlands. We used a combination of historical maps, archives, fungal collections and field survey in eight Quercus ilex patches (4 ancient versus 4 recent replicates) to reconstruct landscapes dynamics and assess biodiversity changes. From the 19th to the 21st century, over half (52.4%) of the ancient woodlands within Montpellier were replaced by other land covers, mainly by urban equipment, while secondary patches (16.8% of the total area) were naturally established. Remaining ancient woodlands show multi-layered vegetation made of multi-secular Pinus halepensis dominating a dynamic understorey made of Quercus ilex and various Mediterranean shrubs. Polypores, but not macrolichens, tended to differ in community composition between ancient and recent woodland patches, with the highest diversity found in ancient woodlands. This study highlights that urban woodland patches of contrasted histories harbour distinct biodiversity stakes to be included in urban planning and provide valuable areas to evaluate biodiversity patterns and dynamics.     

Ecological consequences of fragmentation and deforestation in an urban landscape: a case study

Landscape change is an ongoing process even within established urban landscapes. Yet, analyses of fragmentation and deforestation have focused primarily on the conversion of non-urban to urban landscapes in rural landscapes and ignored urban landscapes. To determine the ecological effects of continued urbanization in urban landscapes, tree-covered patches were mapped in the Gwynns Falls watershed (17158.6?ha) in Maryland for 1994 and 1999 to document fragmentation, deforestation, and reforestation. The watershed was divided into lower (urban core), middle (older suburbs), and upper (recent suburbs) subsections. Over the entire watershed a net of 264.5 of 4855.5?ha of tree-covered patches were converted to urban land use??125 new tree-covered patches were added through fragmentation, 4 were added through reforestation, 43 were lost through deforestation, and 7 were combined with an adjacent patch. In addition, 180 patches were reduced in size. In the urban core, deforestation continued with conversion to commercial land use. Because of the lack of vegetation, commercial land uses are problematic for both species conservation and derived ecosystem benefits. In the lower subsection, shape complexity increased for tree-covered patches less than 10?ha. Changes in shape resulted from canopy expansion, planted materials, and reforestation of vacant sites. In the middle and upper subsections, the shape index value for tree-covered patches decreased, indicating simplification. Density analyses of the subsections showed no change with respect to patch densities but pointed out the importance of small patches (??5?ha) as ??stepping stone?? to link large patches (e.g., >100?ha). Using an urban forest effect model, we estimated, for the entire watershed, total carbon loss and pollution removal, from 1994 to 1999, to be 14,235,889.2?kg and 13,011.4?kg, respectively due to urban land-use conversions.     

Connectivity of public urban grasslands: implications for grassland conservation and restoration in cities

An important limitation of studies on the ecological value of urban habitats is the question of habitat connectivity. While connectivity allows spread and genetic exchange of species, isolation can lead to the extinction of populations through inbreeding and loss of genetic diversity. However, while practitioners already start improving urban habitat patches by means of restoration, issues of connectivity have not been taken in account although being crucial for a self-sustaining habitat network. In our study, we evaluate the connectivity of public urban grasslands such as lawns, grasslands in residential areas, playgrounds or parks in the city of Münster, Germany. Employing a graph theory approach, which uses a map (graph) of habitat patches to calculate functional connectivity measures using patch area size and patch connectivity, we studied four groups of different plant dispersal distances (2 m, 20 m, 44 m and 100 m). This approach can be recommended for planning issues due to the output of different indicator values and comparably low data demands. Our results show for the first time, that connectivity of urban grasslands is extremely low for species of short-distance dispersal but slightly increases for long-distance dispersal. Except two larger conglomerations of well-connected patches, urban grasslands were found to be mostly sparsely connected. Thus, future research should focus on options to improve connectivity and to prioritize patches for ecological improvement. The graph theory approach turned out to be a useful tool to analyse urban habitat connectivity but also to illustrate results obtained.

     

The importance of paleodunes as nesting habitat for Northern Pine Snakes (Pituophis melanoleucus melanoleucus): risk from off-road vehicles in the New Jersey Pine Barrens

Human development and disturbances can be determinants of population viability of some vertebrates in human-impacted ecosystems. The effects on the behavior and population dynamics of reptiles are not well-studied in urban environments. This paper examines the importance of pine forest clearings, openings, and paleodunes for nesting pine snakes (Pituophis melanoleucus melanoleucus) in the New Jersey Pinelands, and the risk to nesting females and offspring from off-road vehicles (ORV). In this ms we 1) develop a rating scale for ORV activity that can be modified for evaluating risk to other vertebrates, 2) compare general habitat features of nesting areas used in the early 1980s with those used in 2020, and 3) examine the fate of nesting areas used in the 1980s and the intensity of ORV use in both time periods. In 2020, nests were located at only 2 of the 10 nesting areas used in 1983 (20%), and only one of the 10 was a paleodune. In comparison, in 2020, 9 of 13 new nesting areas were on paleodunes (69%). In 1983, ORV activity on nesting areas ranged from very low to medium. In the intervening years development and ORV activity increased markedly, and snakes abandoned most areas by 2020. ORV activity in those sites still utilized for nesting increased to high and very high. In 2020, ORV activity ranged from very low (7%) to very high (19%) of the 42 nests. With increasing urban development, nesting pine snakes are using mainly paleodunes deep in the forest, and are exposed to high or very high ORV activity (43%), suggesting concern for viable snake populations in the wake of continued human activity and ORV use.

     

Urban tree cover: an ecological perspective

Analysis of urban tree cover is generally limited to inventories of tree structure and composition on public lands. This approach provided valuable information for resource management. However, it does not account for all tree cover within an urban landscape, thus providing insufficient information on ecological patterns and processes. We propose evaluating tree cover for an entire urban area that is based on patch dynamics. Treed patches are classified by their origin, structure, and management intensity. A patch approach enables ecologists to evaluate ecological patterns and processes for the entire urban landscape and to examine how social patterns influence these ecological patterns and processes.     

Urbanization affects the trophic structure of arboreal arthropod communities

Urbanization is one of the most significant causes of habitat fragmentation on the planet, resulting in substantial losses of biodiversity and disruptions to ecological processes. We examined the effects of urbanization on the diversity and abundance of arboreal invertebrates in a dominant tree species (Angophora costata) in a highly urbanized landscape in Sydney, Australia, identifying the potential ecological consequences of shifts in diversity. We hypothesized that trophic structure would be influenced by landscape context with a greater richness and abundance of invertebrates in small remnants and edges. Canopy arthropods were sampled via beating from trees in 15 sites in three landscape contexts; five large patches of continuous vegetation, five edges of large patches and five small urban remnants. Trees in large patches supported fewer individuals compared to trees in small urban remnants and edge sites. The composition of assemblages and overall trophic structure also differed between edges and large patches, with a greater abundance of grazing insects in edges. No differences were detected between small urban remnants and edges, suggesting that observed differences might be attributed to an edge effect as opposed to an area effect per se. These changes in trophic structure, revealing a greater abundance of grazing herbivores and a reduced abundance of predators and parasitoids in edge sites, are consistent with work describing elevated levels of herbivory in edges of remnant vegetation. Future management of remnant urban vegetation and associated biodiversity requires not only an understanding of how trophic status influences the extent of responses by arboreal invertebrate communities, but also how these will affect ecosystem functioning.     

Renaissance of a rural artifact in a city with a million people: biodiversity responses to an agro-forestry restoration in a large urban traditional fruit orchard

The rural landscapes surrounding large cities are rapidly becoming incorporated into the urban environment. The most conspicuous changes involve green spaces, such as former agro-forestry systems like fruit orchards. In this paper, we assess the influence on biodiversity of restoring a large urban traditional fruit orchard as reflected by six selected taxa: plants, lichens, butterflies, beetles, orthopteroids and birds. The study was performed in Prague, which is the capital city of the Czech Republic and has more than a million inhabitants. We studied the effect of orchard renewal in 45 patches (15 for birds and 30 for other taxa). The majority of taxa responded positively to the restoration. The restoration had a significant positive effect on the species richness of lichens, butterflies and beetles. All taxa showed significantly altered species compositions, and the number of red-listed species increased. Orchards have a high potential for multi-functional use. Orchards are productive agro-forestry systems and host numerous possible human activities. Therefore, orchard restoration also has a social aspect. Moreover, our research in this artificial ecosystem revealed that its restoration increased the biodiversity and conservation potential of the associated areas.

     

Spatial distribution and the value of green spaces for urban red-tailed hawks

Raptors increasingly live and nest successfully in urban areas. In the urban landscape of Hartford, CT, red-tailed hawks established home ranges in large green spaces such as parks, golf courses, and cemeteries but also nested successfully in the commercial district of downtown and in densely built urban and suburban neighborhoods. Data collected from 11 radio-tagged breeding adult hawks indicated that year-round home ranges averaged 107.7 ha, much smaller than home ranges reported for hawks inhabiting rural areas. Most hawk home ranges had multiple core areas that were usually associated with favored perches or larger patches of ‘usable’ green space, defined as patches ≥0.25 ha in size, and home range size was positively associated with larger usable green space patches in core areas. Most nests were located in the largest core area and were within a larger patch of green space within the largest core area. Rather than just the amount or size of green space patches, the value of urban green spaces for these hawks likely also varies with the number and proximity of suitable perches such as buildings or tall trees, types and density of prey, and amount of human activity in and adjacent to these spaces. Territoriality and intraspecific competition may also influence home range size and dispersion of red-tailed hawks nesting in Hartford. In this urban area, mortality due to ingestion of rodenticides and collisions with vehicles affected hawk reproductive success.

     

Interethnic marriage: identifying the second generation in Australia

"Studies in Australia show that an increasing proportion of the population have ancestors from more than one country. Evidence regarding differences in the marriage patterns of first and second generation migrants has been restricted in scope as published marriage registration data includes only birthplace of partners. Marriage registration records include information about the birthplace of parents of partners, but is available only through specially produced tabulations. Changes in the census for 1986 and 1991 make it possible to identify the second generation in households, and this article examines the use of census data as an alternative to marriage registration records in tracing changes in intermarriage patterns and differences between urban and rural areas."     

The influence of urban park characteristics on ant (Hymenoptera, Formicidae) communities

As rapid urbanization continues, existing natural areas within urban zones will play a critical role in safeguarding remaining biodiversity. Ants are an integral part of almost every terrestrial ecosystem, including urban environments, and understanding which environmental characteristics influence their persistence is critical. In this study, 24 protected natural areas within urban parks including mosaic, scrub, herbaceous and forest habitats were surveyed for ants with 563 pitfall traps. The data provide insights into the distribution and abundance of ant fauna in San Francisco natural areas, as well as which characteristics of parks have the most influence on ant community composition. A total of 2,068 ant individuals representing 15 species were collected. A regression analysis revealed that urban forests reduced ant richness and abundance and that there was little or no impact of the Argentine ant on native ants. Natural area size and shape were not important in explaining variations in overall ant species richness and abundance, with many smaller natural areas harboring ant populations that are just as diverse and robust as larger areas.     

Effects of urban matrix on reproductive performance of Great Tit (Parus major) in urban woodlands

In urban areas the density of breeding tits (Paridae) is generally higher and reproductive performance lower compared to rural areas. To explain these landscape differences several hypotheses have been proposed, e.g. differences in habitat quality, inter- and intra-specific competition, predation and food abundance. How breeding performance of birds within remnants of natural vegetation in urban areas is affected by adjacent matrix has been less studied. We performed an experimental study in four urban woodlands surrounded by three types of habitat matrix: residential, high-rise building and grassland/golf course. We placed 300 nest boxes for tits (great tit Parus major and blue tit Cyanistes caeruleus) in 15 transects that were 200 m long, extending from the adjacent matrix 150 m into urban woodland. Density of breeding great tit pairs was highest in residential areas and hatch date was earlier in the residential habitat compared to the other two habitats, however, nestling condition was lower in residential areas. Hatching date was earlier but hatching spread (heaviest nestling/lightest nestling) higher in the three types of urban matrix than inside the urban woodlands. In contrast to previous large-scale comparisons of urban and rural matrix, we almost exclusively found differences in qualitative measures (nestling condition and hatchling spread) at the small scale in which this study was conducted. Adjacent matrix affect great tits breeding in remnant urban woodlands, thus we suggest that management of the surrounding matrix should be included in conservation plans for urban woodlands.     

Vulnerability of native and exotic urban birds to housing densification and changing gardening and landscaping trends

Variation in densities of native and exotic urban-adapted birds across suburban habitats may reveal levels of adaptation that predict vulnerability to habitat modification over time. We investigated the densities of the eight most common exotic and native birds in a southern hemisphere city across suburbs of varying housing density, vegetative cover and garden vegetation characteristics to determine whether avian population densities are maintained across variations in habitat structure that mirror current temporal trends in land use and landscaping/gardening preferences. We also tested whether densities of birds in residential areas bordering undeveloped patches were higher due to spill-over from patches. Densities of all four native species were highest in undeveloped patches and these species were largely absent from high density housing areas. While densities of two exotic species (blackbird, song thrush) were slightly higher in suburbs with greater vegetation complexity, they were still present in higher density housing suburbs in significant numbers. Common starlings were similarly abundant across all residential habitats and house sparrow density increased in higher density housing areas. Blackbirds appeared least vulnerable to housing densification and landscaping and gardening trends because they were abundant across all habitats, including undeveloped patches. Densities of native birds were higher in residential areas bordering undeveloped patches indicating spill-over was occurring and emphasising the role that patches could play in boosting city-wide native bird abundances. Native birds are vulnerable to reductions in garden size and vegetation complexity that should have little or positive effects on populations of common exotic species.     

Determinants of urban tree canopy in residential neighborhoods: Household characteristics, urban form, and the geophysical landscape

The aesthetic, economic, and environmental benefits of urban trees are well recognized. Previous research has focused on understanding how a variety of social and environmental factors are related to urban vegetation. The aim is often to provide planners with information that will improve residential neighborhood design, or guide tree planting campaigns encouraging the cultivation of urban trees. In this paper we examine a broad range of factors we hypothesize are correlated to urban tree canopy heterogeneity in Salt Lake County, Utah. We use a multi-model inference approach to evaluate the relative contribution of these factors to observed heterogeneity in urban tree canopy cover, and discuss the implications of our analysis. An important contribution of this work is an explicit attempt to account for the confounding effect of neighborhood age in understanding the relationship between human and environmental factors, and urban tree canopy. We use regression analysis with interaction terms to assess the effects of 15 human and environmental variables on tree canopy abundance while holding neighborhood age constant. We demonstrate that neighborhood age is an influential covariate that affects how the human and environmental factors relate to the abundance of neighborhood tree canopy. For example, we demonstrate that in new neighborhoods a positive relationship exists between street density and residential tree canopy, but the relationship diminishes as the neighborhood ages. We conclude that to better understand the determinants of urban tree canopy in residential areas it is important to consider both human and environmental factors while accounting for neighborhood age.