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1.
How urban habitats contribute to biodiversity conservation is a key challenge in a rapidly urbanising world. Urban parks can provide important habitats for native species, but previous studies are geographically biased; fast growing megacities, in particular in South America, are clearly understudied. To assess habitat functions and underlying drivers in parks of Santiago de Chile, we analysed the assemblages of wild growing plant species in two ubiquitous park habitat types (grasslands, wooded areas) in 15 parks (150 plots) along an urban-rural gradient. We first used linear contrasts to compare species richness, beta diversity and the proportion of introduced species. We then tested for the explanatory value of environmental variables operating at different spatial scales (plot, park, urban matrix). Unlike in most previous studies, biodiversity patterns were not related to the position of the parks on the urban-rural gradient. Introduced species, mostly from Europe, generally dominated both habitat types (>90 %). Socio-economic (population growth or density), but not spatial, variables were retained in most models. Maintenance intensity was most influential in predicting species assemblages, complemented by park age in wooded areas. A high proportion of European grassland species indicates a trend of homogenisation in park grassland at a cross-continental scale. We conclude that habitat functions of urban parks for native species that have been mainly demonstrated for Europe cannot be generalised to South American megacities. This highlights the need for innovative and locally appropriate conservation approaches (e.g., re-introduction of native species) to foster biodiversity functions in urban parks of South American megacities.  相似文献   

2.
Urban riparian habitats are potentially important resources for native birds in arid ecosystems. Most studies have assessed the value of urban riparian habitat in terms of vegetation and natural resources; however, the surrounding land use and infrastructure may determine the viability of urban habitat. We studied the impact of urban structure, the combination of land use, infrastructure and vegetation variables that work together to shape the urban environment, on avian riparian habitat in the Truckee Meadows, Nevada, USA. Land use and infrastructure explained avian species richness and abundance better than local vegetation alone, but community resemblance was more strongly correlated to vegetation. Avian species guilds responded differentially to surrounding land use, suggesting there may be a functional difference between land use types. The best models for bird diversity used urban structure (both land use and vegetation) to describe potential habitat. Urban structure describes urban habitat in ways that vegetation variables alone cannot. Studies that ignore land use and infrastructure and other socioeconomic variables are likely missing key functional differences within urban ecosystems, and may miss the potential for compatible development that encourages both biodiversity and urban growth.  相似文献   

3.
By comparing with the historic semi-natural grassland and woodland vegetation data compiled in the 1970s and 1980s, we aimed to reveal potential roles of small and linear habitat fragments remaining in the urbanized satoyama landscape (i.e., agricultural landscape) in Japan for conservation of grassland plant species. TWINSPAN cluster analysis differentiated the current vegetation from historic one. Current vegetation of Miscanthus grassland was classified into two different groups and one of the two was equivalent to current understory vegetation of fragmented woodland. The linear woodland edge vegetation along the roads was classified into one group and separated from the other current vegetation groups. The current vegetation groups were characterized by higher richness of exotic species than historic vegetation groups. Detrended correspondence analysis (DCA) revealed that there were no groups of current vegetation that is equivalent to historic woodland understory vegetation. The vegetation quality of the current group of Miscanthus grassland and secondary woodland remaining on urban public properties, and the group of linear roadside vegetation were almost equivalent to that of historic semi-natural grassland. Both of the small and linear habitat fragments might have functioned as habitats for grassland species under regular mowing management. Although small and linear habitat fragments would not be sufficient for sustaining grassland populations in the future, these habitats can serve as key reservoirs for grassland species recovery in the conservation and restoration of grassland communities in the urbanized satoyama landscape.  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
The historic Rideau Canal (built in the 1800s) in eastern Ontario, Canada is a heavily managed and engineered ecosystem, popular for recreational boating and sport fishing in the summer and ice skating in the winter. However, little is actually know about the fish and aquatic macrophyte communities, particularly in the urban reach in Ottawa between Hartwell’s Lock and the outflow of Dows Lake. The objective of this study was to examine the extent to which fish and macrophytes varied among different natural and engineered habitat/substrate types across the period when the canal is at navigational water levels. Five gross habitat types were identified, consisting of gravel, silt/sand, rip-rap/gabion basket, boulder and concrete wall habitats. Replicate transects were established in the littoral zone, representing the different habitat types. Snorkel surveys were conducted on a biweekly basis, where fish species and aquatic macrophytes within the transects were quantified. Supplementary data on fish populations was obtained through seine net sampling as well as angler interviews and visual observations. The fish community was characterized as a reasonably simple warmwater assemblage, dominated by centrarchids (e.g., pumpkinseed [Lepomis gibbosus], bluegill [L. macrochirus], and largemouth bass [Micropterus salmoides]). In fact, more than 90% of all fish encountered (snorkel surveys and seine netting) belonged to the centrarchid family. None of the 17 fish species encountered in the reach were considered “at risk” in Canada, although the system supports one of the few urban muskellunge (Esox masquinongy) populations in the world and provides a range of urban recreational fishing opportunities for sportsfish. Fish diversity metrics (e.g., diversity, richness, evenness) varied little among habitat types, perhaps reflecting the fact that vegetation communities were reasonably homogeneous, largely dominated by the exotic Eurasian water milfoil (Myriophyllum spicatum). This research provides managers with the first detailed information on the aquatic ecology in this engineered urban ecosystem which will enable relevant government agencies (e.g., Parks Canada) to better balance the iconic cultural values of national significance with their mandate to protect the ecological integrity of the canal ecosystem.  相似文献   

7.
Urban growth is a strong driver of habitat degradation and loss. In spite of that, a surprising diversity of native species may survive in urban areas. In the La Paz, Bolivia metropolitan area and surroundings, local populations of “viscachas” (Lagidium viscacia) currently survive in small, isolated habitat patches. We assessed 13 study sites in 1999, 2003, and 2007 to document the effects of urban growth on L. viscacia habitats. Degree of disturbance at the study sites increased more between 1999 and 2003 than it did between 2003 and 2007 due to patterns of urban expansion. Using satellite imagery we determined that the urban area increased 566 ha (from 1987 to 2001) mostly due to southward urban area expansion down the valley where the best viscacha habitats were located. Occupied patch area decreased 74 % between 1999 and 2007, accompanied by significant increases in patch edge-to-area ratios. Currently L. viscacia populations in La Paz are experiencing a habitat attrition process. If a current urban expansion plan for La Paz is approved, about 75 % of the remaining habitat may be lost to urban development in a short time, compromising the future viability of this species in the metropolitan area and surroundings. Environmental regulations to control urban growth of the La Paz metropolitan area are urgently required and constitute the only hope for the survival of L. viscacia in the city.  相似文献   

8.
Urban green spaces provide habitat for numerous plant and animal species. However, currently we have little knowledge on which determinants drive the species richness within and across taxonomic groups. In this paper we investigate the determinants of total, native, and endangered species richness for vascular plants, birds, and mammals within and across taxonomic groups. We examined a stratified random sample of 32 urban green spaces in Hannover, Germany. Species inventories for plants and birds were generated on the basis of line transect surveys. Mammals were surveyed by means of point counts using camera traps. Using a principal component analysis and multiple regression models, we tested 10 explanatory variables for species-area effects, distance effects, and the effects of habitat structure of green spaces on species richness. When analyzing single explanatory variables, we determined that the species richness of all groups was significantly positively correlated to patch area, number of habitat types, and a short distance to the nearest green space. Testing combined effects of variables showed that patch area in combination with habitat heterogeneity was most important for plants (total, native, and endangered), birds (total and native), and overall species richness. This emphasizes the importance of the species-area effect and the effects of habitat structure on species richness in urban green spaces. We conclude that, in the context of urban planning, it is important to conserve large green spaces that include a high diversity of habitats to maintain high species richness.  相似文献   

9.
Urban areas are probably the most fragmented environments with respect to the presence of semi-natural habitats and shape of these habitats may be significantly affected by urbanization. Patch perimeter in landscape or habitat studies is much less popular to study than patch area. The studied sites were situated in the industrial city of Pardubice, which is one of the ten largest cities in the Czech Republic with nearly 100,000 inhabitants. In total, 40 grasslands were studied within a circular area of 314 km2. Butterflies and beetles with diurnal activity were studied during timed survey walks. A Simultaneous autoregressive model was used for test of the effect of biodiversity-area and biodiversity-perimeter relationships and for exclusion of potential bias caused by spatial autocorrelation. The models including patch perimeter performed better than those using patch area in explaining species richness, abundance and diversity of investigated organisms and were less influenced by spatial autocorrelation. The main conclusion and recommendation of the present study is that researchers should pay more attention to the possible influence of the patch perimeter as a potential predictor or co-predictor for landscape and habitat studies – especially in urban areas, where the negative effects of fragmentation might be much higher than in rural or more natural landscapes. Performing preliminary tests on comparisons between area and perimeter is highly recommended.  相似文献   

10.
Mediterranean landscapes resulted from complex land uses that produced a mosaic of extensive crops, grasslands, scrublands and scattered woodlands. During the twentieth century the decrease in traditional agriculture triggered a decrease in open habitats and an increase in forests. In the meantime urban centres grew dramatically. Both spread of forest and urban areas have been suspected to participate in the decline of typical Mediterranean bird species and, in general, to cause faunal loss. However, modern cities offer a variety of landscape types and, in the Mediterranean, their value for native bird species has been little assessed. We compared the bird communities from an urban landscape, including built up and natural or semi natural units within the limits of the city of Montpellier, to the bird communities from non-urban habitats (cropland, grassland and woodland) located nearby but away from direct urban influence. Fifty four percent of the bird species recorded in the non-urban habitats also occurred in the urban landscape. On average, estimated species richness in the urban landscape was similar to values obtained for non-urban habitats. Within the urban landscape species richness was lowest in the dense historical centre and highest in the residential areas. The residential areas and urban woods were suitable habitats for most generalist species but also for several more specialized species recorded in the non-urban habitats. Some species actually reached their highest observation frequency in the urban landscape. Urban landscape was least favourable to the same farmland and open-habitat specialists that have been negatively affected by agricultural abandonment in the region. Finally, five of the species common in the urban landscape had an unfavorable conservation status in 2004 in the EU. This study emphasizes that Mediterranean urban areas have the potential to host a diverse native bird community. Finding ways to improve their carrying capacity for the local avifauna might be a worthwhile objective for animal conservation.  相似文献   

11.

Urban expansion is creating environmental stressors through land use change, habitat fragmentation, and habitat loss. These stressors, along with a host of others, are driving precipitous declines in vertebrate taxa around the world. Amphibians, often requiring a narrow range of environmental conditions, can be especially susceptible to the stressors of environmental change. Despite habitat loss and degradation, some amphibian species continue to persist in altered urban landscapes. The red-backed salamander (Plethodon cinereus) is one such- species and in this study, we assess how habitat patch size affects population density and genetic diversity of salamander populations in and around an urban center in Ohio, United States. Further, we examined patterns of genetic differentiation and landscape connectivity to understand gene flow between populations and tested for historic demographic bottleneck effects. Populations were sampled from 9 urban forest patches ranging in size from less than 1 ha to approximately 250 ha. There was no apparent effect of contiguous habitat patch size on salamander density nor genetic diversity, but we did observe significant genetic differentiation between 97% of pairwise population comparisons. The differentiation observed was not a result of overland distance or effective distance due to landscape resistance. There was evidence of historic bottlenecks at every site. These results suggest that density is driven by within-patch heterogeneity and that genetic diversity is affected by drivers other than patch size or contemporary population density. Our study demonstrates that red-backed salamanders can persist in wooded, urban parks, but that genetic diversity remains susceptible to demographic changes.

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12.
Urbanization is one of the most extreme forms of land alteration. Energy fluxes are severely affected and cities tend to have the Urban Heat Island (UHI) phenomenon, although vegetated areas inside cities could have a positive effect in mitigating UHI effect. Our main objective was to analyze the relationship between vegetation characteristics, patch size and land surface temperature (LST) in three urban areas of northwestern Argentina. We selected 38 green spaces of different size distributed in four cities, all located in the eastern foothills of the subtropical mountain forests. We used Landsat TM satellite images to calculate Normalized Difference Vegetation Index (NDVI) and LST. We assessed the net effect of patch size on LST by computing a Difference Temperature Index. At the regional scale, our results showed that vegetation patch size had a direct effect on reducing the LST of the green space. At a local scale, the analysis of the relationship between vegetation on urban green spaces and LST along a gradient of urbanization showed that green spaces with more vegetation tends to reduce LST. The results showed that largest green spaces were between 1.5 and 2.8 °C cooler than the surrounding built. In order to mitigate the UHI effect in cities, larger green spaces appear to be a possible solution.  相似文献   

13.
Shih  Wan-Yu 《Urban Ecosystems》2018,21(2):379-393

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.

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14.
Urban Ecosystems - Urbanisation affects fauna in many ways; with some species persisting and going on to dominate urban habitats, while other species decline over time due to habitat disturbance...  相似文献   

15.
Nowadays, urban areas play a crucial role in biodiversity conservation and habitat protection despite the constant pressures on which these habitats are subjected. They may even host relatively new plant communities due to the peculiar ecosystem where they vegetate. The port of Trieste (NE Italy) is characterized by a mixed mosaic of intensely human impacted areas (where commercial activities are still ongoing) flanked by abandoned areas where vegetation persists or has spontaneously recovered. In this study, we sampled the whole port area through a stratified random sampling by placing multiscalar nested plots in four different habitats (strata) previously identified by photo-interpretation. Plant species richness and abundance were assessed in each plot. Each species was then classified as native or alien and patterns of species richness and complementarity were compared among habitats. Results show that there is a significant difference in species richness patterns among habitats, while observed patterns are likely to vary at different spatial scales. As expected, urban plots account for most of the alien species in the sampling, while wooded plots cope better with invasion, accounting for a lower alien/native ratio. These results highlight how habitat diversity enhances biodiversity in urban areas and how it could provide an effective filtering effect able to reduce the spread of alien species. In addition, we provide further evidence for the use of multi-scale approaches in order to study the complex relationships between spatial heterogeneity and plant species richness.  相似文献   

16.
Green infrastructure in urbanized areas has a dual purpose that achieves both sociological and ecological goals. To benefit society and the urban ecosystem, green infrastructure should be effectively managed. We investigated carabid diversity and assemblage structure as indicators of biodiversity in green infrastructures in a rapidly developing urban area to identify the habitat’s values. In addition, we attempted to reveal the effect of environmental variables (e.g., vegetation structure, soil, and disturbance) that strongly contribute to carabid diversity and assemblage structure. Of the collected organisms, 6,154 individuals representing 20 carabid species were identified in the green infrastructure. Those species with flight ability and that were found in dry habitats were widely distributed and dominated green infrastructures. Carabid assemblages changed significantly in response to management practices. These changes were both positive and negative, with the negative changes increasing the instability of the carabid assemblages through the destruction of their habitat. Other factors, such as the presence of original habitat, habitat age, and habitat succession, also had a considerable effect on carabid diversity. We revealed that management practices prevented habitat succession, and these interactive effects determined carabid diversity and structure in green infrastructures.  相似文献   

17.
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.  相似文献   

18.
As urbanization in the landscape increases, some urban centers are setting aside habitat for wildlife. This habitat may be particularly valuable to declining or conservation-priority species. One group in particular need of conservation actions that may benefit from habitat located in urban areas is grassland birds. Declines of grassland bird species have been particularly severe in the Midwestern U.S., where most grassland cover has been lost, fragmented, and surrounded by unsuitable habitat. Conservation efforts have focused on protecting large grasslands surrounded by minimal amounts of trees and development. Although urban development is considered hostile to grassland birds, this assumption has received little attention. In heavily fragmented landscapes where habitat is limited, urban grasslands may be of significant value to grassland birds. We examined grassland bird response to development and additional landscape and habitat variables in the greater Chicago metropolitan area. In 2012 and 2013, we surveyed bird communities in grassland patches along a gradient of urbanization and patch sizes. Density of Savannah Sparrows (Passerculus sandwichensis) increased with amount of development, while density of Sedge Wrens (Cistothorus platensis) decreased. Development did not appreciably impact Bobolinks (Dolichonyx oryzivorus), Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), Grasshopper Sparrows (Ammodramus savannarum), or Henslow’s Sparrows (Ammodramus henslowii). Patch size had a positive effect on species densities. These results indicate that for many conservation-priority grassland birds, urban landcover surrounding grasslands generally has neutral rather than negative effects on habitat use. Therefore, grasslands in developed landscapes may provide valuable contributions to regional conservation efforts.  相似文献   

19.
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.  相似文献   

20.
Urban development either eliminates, or severely fragments, native vegetation, and therefore alters the distribution and abundance of species that depend on it for habitat. We assessed the impact of urban development on bird communities at 121 sites in and around Perth, Western Australia. Based on data from community surveys, at least 83 % of 65 landbirds were found to be dependent, in some way, on the presence of native vegetation. For three groups of species defined by specific patterns of habitat use (bushland birds), there were sufficient data to show that species occurrences declined as the landscape changed from variegated to fragmented to relictual, according to the percentage of vegetation cover remaining. For three other groups (urban birds) species occurrences were either unrelated to the amount of vegetation cover, or increased as vegetation cover declined. In order to maximise the chances of retaining avian diversity when planning for broad-scale changes in land-use (i.e. clearing native vegetation for housing or industrial development), land planners should aim for a mosaic of variegated urban landscapes (>60 % vegetation retention) set amongst the fragmented and relictual urban landscapes (<60 % vegetation retention) that are characteristic of most cities and their suburbs. Management actions for conserving remnant biota within fragmented urban landscapes should concentrate on maintaining the integrity and quality of remnant native vegetation, and aim at building awareness among the general public of the conservation value of remnant native vegetation.  相似文献   

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