Community heterogeneity of aquatic macroinvertebrates in urban ponds at a multi-city scale

Purpose

Urbanisation is a leading cause of biotic homogenisation in urban ecosystems. However, there has been little research examining the effect of urbanisation and biotic homogenisation on aquatic communities, and few studies have compared findings across different urban landscapes. We assessed the processes that structure aquatic macroinvertebrate diversity within five UK cities and characterise the heterogeneity of pond macroinvertebrate communities within and among urban areas.

Methods

A total of 132 ponds were sampled for invertebrates to characterise biological communities of ponds across five UK cities. Variation among sites within cities, and variation among urban settlements, was partitioned into components of beta diversity relating to turnover and nestedness.

Results

We recorded 337 macroinvertebrate taxa, and species turnover almost entirely accounted for the high beta-diversity recorded within each urban area and when all ponds were considered. A total of 40% of all macroinvertebrates recorded were unique to a particular urban settlement. In contrast to the homogenisation of terrestrial and lotic communities in urban landscapes reported in the literature, ponds support highly heterogeneous communities within and among urban settlements.

Conclusions

The high species turnover (species replacement) recorded in this study demonstrates that urban pond biodiversity conservation would be most efficient at a landscape-scale, rather than at the individual ponds scale. Pond conservation practices need to consider the spatial organization of ecological communities (landscape-scale) to ensure that the maximum possible biodiversity can be protected.

     

Multi-level,multi-scale habitat selection by a wide-ranging,federally threatened snake

Context

Although multi-scale approaches are commonly used to assess wildlife-habitat relationships, few studies have examined selection at multiple spatial scales within different hierarchical levels/orders of selection [sensu Johnson’s (1980) orders of selection]. Failure to account for multi-scale relationships within a single level of selection may lead to misleading inferences and predictions.

Objectives

We examined habitat selection of the federally threatened eastern indigo snake (Drymarchon couperi) in peninsular Florida at the level of the home range (Level II selection) and individual telemetry location (Level III selection) to identify influential habitat covariates and predict relative probability of selection.

Methods

Within each level, we identified the characteristic scale for each habitat covariate to create multi-scale resource selection functions. We used home range selection functions to model Level II selection and paired logistic regression to model Level III selection.

Results

At both levels, EIS selected undeveloped upland land covers and habitat edges while avoiding urban land covers. Selection was generally strongest at the finest scales with the exception of Level II urban edge which was avoided at a broad scale indicating avoidance of urbanized land covers rather than urban edge per se.

Conclusions

Our study illustrates how characteristic scales may vary within a single level of selection and demonstrates the utility of multi-level, scale-optimized habitat selection analyses. We emphasize the importance of maintaining large mosaics of natural habitats for eastern indigo snake conservation.

     

Linking greenhouse gas emissions to urban landscape structure: the relevance of spatial and thematic resolutions of land use/cover data

Context

Emissions of greenhouse gases in urban areas play an important role in climate change. Increasing attention has been given to urban landscape structure–emission relationships (SERs). However, it remains unknown if and to what extent SERs are dependent on observational scale.

Objective

To assess how changing observational scales (in terms of spatial and thematic resolutions) of urban landscape structure affect SERs.

Methods

We examined correlations between 16 landscape metrics and greenhouse gas emissions across 52 European cities, through (1) systematic manipulation of spatial and thematic resolutions of the urban land use/cover (ULUC) dataset, and (2) comparison between available standard ULUC datasets with different spatial resolutions.

Results

Our analyses showed that the observed SERs significantly depend on both thematic and spatial resolutions of the ULUC data. For the 16 landscape metrics, we found diverse spatial/thematic scaling relations exhibiting monotonic, hump-shaped or scale-invariant trends. For different landscape metrics, the SERs were strongest at different spatial scales, suggesting that there is no consistent scaling relation over those observational scales.

Conclusions

SERs are highly sensitive to spatial and thematic resolutions of landscape data. To avoid the problem of ‘ecological fallacy,’ important caveats should be taken for interpretations based on single landscape metrics. Particular consideration should be paid to metrics that are easily interpretable, predictable in scaling behaviors, and important for shaping SERs, such as PLAND, ED, and LPI. Systematic investigations on scaling behaviors of SERs over well-defined scale domains are encouraged in future studies linking greenhouse gas emissions and urban landscape structure.

     

A hierarchical analysis of the relationship between urban impervious surfaces and land surface temperatures: spatial scale dependence,temporal variations,and bioclimatic modulation

Context

Understanding how urban impervious surfaces (UIS) affect land surface temperatures (LST) on different scales in space and time is important for urban ecology and sustainability.

Objectives

We examined how spatial scales, seasonal and diurnal variations, and bioclimatic settings affected the UIS–LST relationship in mainland China.

Methods

We took a hierarchical approach explicitly considering three scales: the ecoregion, urban cluster, and urban core. The UIS–LST relationship was quantified with Pearson correlation using multiple remote sensing datasets.

Results

In general, UIS and LST were positively correlated in summer daytime/nighttime and winter nighttime, but negatively in winter daytime. The strength of correlation increased from broad to fine scales. The mean R² of winter nights at the urban core scale (0.262) was 4.03 times as high as that at the ecoregion scale (0.065). The relationship showed large seasonal and diurnal variations: generally stronger in summer than in winter and stronger in nighttime than in daytime. At the urban core scale, the mean R² of summer daytime (0.208) was 3.25 times as high as that of winter daytime (0.064), and the mean R² of winter nighttime (0.262) was 4.10 times as high as that of winter daytime (0.064). Vegetation and climate substantially modified the relationship during summer daytime on the ecoregion scale.

Conclusions

Our study provides new evidence that the UIS–LST relationship varies with spatial scales, diurnal/seasonal cycles, and bioclimatic context, with new insight into the cross-scale properties of the relationship. These findings have implications for mitigating urban heat island effects across scales in China and beyond.

     

Application of partial least squares regression in detecting the important landscape indicators determining urban land surface temperature variation

Context

Revealing the interaction between landscape pattern and urban land surface temperature (LST) can provide insight into mitigating thermal environmental risks. However, there is no consensus about the key landscape indicators influencing LST.

Objectives

This study sought to identify the key landscape indicators influencing LST considering a large number of landscape pattern variables and multiple scales.

Methods

This study applied ordinary least squares regression and partial least squares regression to explore a combination of landscape metrics and identify the key indicators influencing LST. A total of 49 Landsat images of the main city of Shenzhen, China were examined at 13 spatial scales.

Results

The landscape composition indicators derived from biophysical proportion, a new metric developed in this study, more effectively determined LST variation than those derived from land cover proportion. Area-related landscape configuration indicators independently characterized LST variation, but did not give much more new information beyond that given by land cover proportion. Shape-related landscape configuration indicators were effective in combination with land cover proportion, but their importance was uncertain when temporal and spatial scales varied.

Conclusions

The influence of landscape configuration on LST exists but should not be overestimated. Comparison of numerous variables at multiple spatiotemporal scales can help identify the influence of multiple landscape characteristics on LST variation.

     

Multi-scale mismatches between urban sprawl and landscape fragmentation create windows of opportunity for conservation development

Context

Urban sprawl and the expanding transportation infrastructure drive land consumption and landscape fragmentation, causing environmental deterioration and loss of species. Current understanding of how these drivers interact to shape landscape fragmentation is still poor. However, a strong correlation between urban sprawl and landscape fragmentation patterns is commonly assumed.

Objectives

Our main objective was to test the strength, non-stationarity, and scale-dependency of the relationship between urban sprawl and landscape fragmentation patterns (‘sprawl-fragmentation relationship’). Subsequently, we propose an extended framework for the links between urban sprawl, expansion of transport infrastructure, and landscape fragmentation.

Methods

We quantified spatial patterns of urban sprawl and landscape fragmentation for mainland Spain at multiple scales. We then fitted global regression models and geographically weighted regression models with metrics of landscape fragmentation and urban sprawl.

Results

Most variation in landscape fragmentation values (almost 80 % on average) is not explained by urban sprawl metrics through global modeling. Local models show substantial improvements in model performance, with an average of 37 % of the variance remaining unexplained. The contribution of urban sprawl to landscape fragmentation patterns varies locally and depends on scale, with higher contributions at coarser scales and at higher organizational levels.

Conclusions

Our investigation revealed three critical characteristics of the sprawl-fragmentation relationship: it does not prevail, is non-stationary, and scale-dependent. We propose four mechanisms that may have resulted in this mismatch: scale, time-lagged development, spatial arrangement of development, and other external variables including teleconnections. These spatial mismatches provide windows of opportunity for conservation through better development strategies.

     

Abundance of urban male mosquitoes by green infrastructure types: implications for landscape design and vector management

Context

Urban green space (UGS) is widely espoused in sustainable urban design. Notwithstanding its ecosystem services, UGS is commonly perceived as inadvertent habitats for urban mosquitoes. Moreover, the lack of ecological understanding of mosquitoes and their urban habitats renders vector control in green spaces without reliance on chemical and bio-pesticides especially challenging.

Objectives

This study envisages the application of a comparative analytical method for the evaluation and optimization of vector management in different urban spaces. The research examines the extent of male habitat preference as measured by population characteristics of urban adult mosquitoes on green roof and control sites.

Methods

Adult mosquito traps were deployed on green roofs (GR), bare roofs (negative control, NC), and low-elevation gardens (positive control, PC). Distribution of male and female members of vector species were analyzed

Results

Urban adult male mosquitoes exhibited highly-selective habitat use of the studied urban spaces, in that they were clustered chiefly in PC. Their spatial distributions are consistently explained by site group even under the stringent measure of presence/absence. The sex ratios of GR and NC were highly skewed toward females, which lends further to the interpretation of strong male habitat preference for the studied PC gardens.

Conclusions

Urban mosquitoes do not display similar degrees of affinity for different types of green infrastructure. The methodology used can help prioritize urban sites and optimize control strategies. The uses of amenable environmental features salient to mosquito survival in landscape design should be explored as a sustainable and environmentally-friendly vector management approach.

     

The relative impacts of vegetation,topography and spatial arrangement on building loss to wildfires in case studies of California and Colorado

Context

Wildfires destroy thousands of buildings every year in the wildland urban interface. However, fire typically only destroys a fraction of the buildings within a given fire perimeter, suggesting more could be done to mitigate risk if we understood how to configure residential landscapes so that both people and buildings could survive fire.

Objectives

Our goal was to understand the relative importance of vegetation, topography and spatial arrangement of buildings on building loss, within the fire’s landscape context.

Methods

We analyzed two fires: one in San Diego, CA and another in Boulder, CO. We analyzed Google Earth historical imagery to digitize buildings exposed to the fires, a geographic information system to measure some of the explanatory variables, and FRAGSTATS to quantify landscape metrics. Using logistic regression we conducted an exhaustive model search to select the best models.

Results

The type of variables that were important varied across communities. We found complex spatial effects and no single model explained building loss everywhere, but topography and the spatial arrangement of buildings explained most of the variability in building losses. Vegetation connectivity was more important than vegetation type.

Conclusions

Location and spatial arrangement of buildings affect which buildings burn in a wildfire, which is important for urban planning, building siting, landscape design of future development, and to target fire prevention, fuel reduction, and homeowner education efforts in existing communities. Landscape context of buildings and communities is an important aspect of building loss, and if taken into consideration, could help communities adapt to fire.

     

Habitat connectivity and complexity underpin fish community structure across a seascape of tropical macroalgae meadows

Context

In heterogeneous landscapes, local patterns of community structure are a product of the habitat size and condition within a patch interacting with adjacent habitat patches of varying composition and quantity. While evidence for local versus landscape factors have been found in terrestrial biomes, support for such multi-scale effects shaping marine ecological communities is equivocal.

Objectives

We investigated whether within-patch habitat condition can override seascape context to explain the community structure of macroalgae-associated reef fishes across a tropical seascape.

Methods

We mapped the distribution and abundance of a diverse family of reef fishes (Labridae) occupying macroalgae meadows within a tropical reef ecosystem, and using best-subsets model selection, investigated the potential for habitat structural connectivity and/or local habitat quality for predicting variations in fish community structure across the seascape.

Results

Local habitat quality (canopy structure, hard habitat complexity) and area of coral-dominated habitat within 500 m of a macroalgal meadow provided the best predictors of fish community structure. However, the specific importance of a given predictor varied with fish life history stage and functional trophic group. Interestingly, macroalgae meadow area was among the least important predictors.

Conclusions

Given the complex interplay between local habitat quality and spatial context effects on fish biodiversity, our study reveals the multi-scale predictors that should be used in spatial conservation and management approaches for tropical fish diversity. Moreover, our findings question the ubiquity of habitat area effects in patchy landscapes, and cautions against a sole reliance on habitat quantity in spatial management.

     

Activating landscape ecology: a governance framework for design-in-science

Context

In response to predominantly local and private approaches to landscape change, landscape ecologists should critically assess the multiscalar influences on landscape design.

Objectives

This study develops a governance framework for Nassauer and Opdam’s “Design-in-Science” model. Its objective is to create an approach for examining hierarchical constraints on landscape design in order to investigate linkages among urban greening initiatives, patterns of landscape change, and the broader societal values driving those changes. It aims to provide an integrative and actionable approach for landscape sustainability science.

Methods

This framework is examined through an ethnographic study of public policy processes surrounding the urban tree initiatives in Boston, MA; Philadelphia, PA; and Baltimore, MD.

Results

These initiatives demonstrate the impact of political and economic decentralization on urban landscape patterns. Their collaborative governance approach incorporates diverse resources to implement programming at a fine-scale. The predominant tree giveaway program fragments the urban and regional forest.

Conclusion

Spatial and temporal fragmentation undermines the long-term security of urban greening programs, and it suggests reconsideration of the role of state regimes in driving broad scale spatial planning.

     

Ecological contributions to human health in cities

Context

Ecological research, from organismal to global scales and spanning terrestrial, hydrologic, and atmospheric domains, can contribute more to reducing health vulnerabilities. At the same, ecological research directed to health vulnerabilities provides a problem-based unifying framework for urban ecologists.

Objective

Provide a framework for expanding ecological research to address human health vulnerabilities in cities.

Methods

I pose an urban ecology of human health framework that considers how the ecological contributions to health risks and benefits are driven by interacting influences of the environment, active management, and historical legacies in the context of ecological self-organization. The ecology of health framework is explored for contrasting examples including heat, vector borne diseases, pollution, and accessible greenspace both individually and in a multifunctional landscape perspective.

Results

Urban ecological processes affect human health vulnerability through contributions to multiple hazard and well-being pathways. The resulting multifunctional landscape of health vulnerability features prominent hotspots and regional injustices. A path forward to increase knowledge of the ecological contributions to health vulnerabilities includes increased participation in in interdisciplinary teams and applications of high resolution environmental sensing and modeling.

Conclusions

Research and management from a systems and landscape perspective of ecological processes is poised to help reduce urban health vulnerability and provide a better understanding of ecological dynamics in the Anthropocene.

     

Deciduous trees increase bat diversity at stand and landscape scales in mosaic pine plantations

Context

In heterogeneous landscapes, habitat complementation is a key process underlying the distribution of mobile species able to exploit non-substitutable resources over large home ranges. For instance, insectivorous bats need to forage in a diversity of habitat patches offering varied compositions and structures within forest landscape mosaics to fulfill their life cycle requirements.

Objectives

We aimed at analyzing the effects of forest structure and composition measured at the stand and landscape scales on bat species richness, abundance and community composition in pine plantation forests of south-western France.

Methods

We sampled bat communities at different periods of the summer season using automatic ultrasound recorders along a tree composition gradient from pine monocultures to pure oak stands. We analyzed bat species activity (as a proxy for bat abundance) and species richness with linear mixed models. Distance-based constrained ordinations were used to partition the spatio-temporal variation in bat communities.

Results

Deciduous tree cover increased bat activity and modified community composition at both stand and landscape scales. Changes in bat communities were mostly driven by landscape-scale variables while bat activity responded more to stand-scale predictors.

Conclusions

The maintenance of deciduous trees at both stand and landscape scales is likely critical for bat communities living in fast-growing conifer plantations, by increasing the availability and diversity of prey and roosting sites. Our study suggests that bats respond to forest composition at both stand and landscape scales in mosaic plantation landscapes, mainly through a resource complementation process.

     

Effects of land use on population presence and genetic structure of an amphibian in an agricultural landscape

Context

Species distributions are a function of an individual’s ability to disperse to and colonize habitat patches. These processes depend upon landscape configuration and composition.

Objectives

Using Blanchard’s cricket frogs (Acris blanchardi), we assessed which land cover types were predictive of (1) presence at three spatial scales (pond-shed, 500 and 2500 m) and (2) genetic structure. We predicted that forested, urban, and road land covers would negatively affect cricket frogs. We also predicted that agricultural, field, and aquatic land covers would positively affect cricket frogs.

Methods

We surveyed for cricket frogs at 28 sites in southwestern Ohio, USA to determine presence across different habitats and analyze genetic structure among populations. For our first objective, we examined if land use (crop, field, forest, and urban habitat) and landscape features (ponds, streams, and roads) explained presence; for our second objective, we assessed whether these land cover types explained genetic distance between populations.

Results

Land cover did not have a strong influence on cricket frog presence. However, multiple competing models suggested effects of roads, streams, and land use. We found genetic structuring: populations were grouped into five major clusters and nine finer-scale clusters. Highways were predictive of increased genetic distance.

Conclusions

By combining a focal-patch study with landscape genetics, our study suggests that major roads and waterways are key features affecting species distributions in agricultural landscapes. We demonstrate that cricket frogs may respond to landscape features at larger spatial scales, and that presence and movement may be affected by different environmental factors.

     

Spatial scale and pattern dependences of aboveground biomass estimation from satellite images: a case study of the Sierra National Forest,California

Context

Spatial scale and pattern play important roles in forest aboveground biomass (AGB) estimation in remote sensing. Changes in the accuracy of satellite images-estimated forest AGBs against spatial scales and pixel distribution patterns has not been evaluated, because it requires ground-truth AGBs of fine resolution over a large extent, and such data are difficult to obtain using traditional ground surveying methods.

Objectives

We intend to quantify the accuracy of AGB estimation from satellite images on changing spatial scales and varying pixel distribution patterns, in a typical mixed coniferous forest in Sierra Nevada mountains, California.

Methods

A forest AGB map of a 143 km² area was created using small-footprint light detection and ranging. Landsat Thematic Mapper images were chosen as typical examples of satellite images, and resampled to successively coarser resolutions. At each spatial scale, pixels forming random, uniform, and clustered spatial patterns were then sampled. The accuracies of the AGB estimation based on Landsat images associated with varying spatial scales and patterns were finally quantified.

Results

The changes in the accuracy of AGB estimation from Landsat images are not monotonic, but increase up to 60–90 m in spatial scale, and then decrease. Random and uniform spatial patterns of pixel distributions yield better accuracy for AGB estimation than clustered spatial patterns. The corrected NDVI (NDVIc) was the best predictor of AGB estimation.

Conclusions

A spatial scale of 60–90 m is recommended for forest AGB estimation at the Sierra Nevada mountains using Landsat images and those with similar spectral resolutions.

     

Influences of scale on bat habitat relationships in a forested landscape in Nicaragua

Context

Scale dependence of bat habitat selection is poorly known with few studies evaluating relationships among landscape metrics such as class versus landscape, or metrics that measure composition or configuration. This knowledge can inform conservation approaches to mitigate habitat loss and fragmentation.

Objectives

We evaluated scale dependence of habitat associations and scaling patterns of landscape metrics in relation to bat occurrence or capture rate in forests of southwestern Nicaragua.

Methods

We captured 1537 bats at 35 locations and measured landscape and class metrics across 10 spatial scales (100–1000 m) surrounding capture locations. We conducted univariate scaling across the 10 scales and identified scales and variables most related to bat occurrence or capture rate.

Results

Edge and patch density, at both landscape and class levels, were the most important variables across species. Feeding guilds varied in their response to metrics. Certain landscape and configuration metrics were most influential at fine (100 m) and/or broad (1000 m) spatial scales while most class and composition metrics were influential at intermediate scales.

Conclusions

These results provide insight into the scale dependence of habitat associations of bat species and the influence of fine and broad scales on habitat associations. The effects of scale, examined in our study and others from fine (100 m) to broad (5 km) indicate habitat relationships for bats may be more informative at larger scales. Our results suggest there could be general differences in scale relationships for different groups of landscape metrics, which deserves further evaluation in other taxonomic groups.

     

Spatial fit between water quality policies and hydrologic ecosystem services in an urbanizing agricultural landscape

Context

Sustaining hydrologic ecosystem services is critical for human wellbeing but challenged by land use for agriculture and urban development. Water policy and management strive to safeguard hydrologic services, yet implementation is often fragmented. Understanding the spatial fit between water polices and hydrologic services is needed to assess the spatial targeting of policy portfolios at landscape scales.

Objectives

We investigated spatial fit between 30 different public water policies and four hydrologic services (surface and groundwater quality, freshwater supply, and flood regulation) in the Yahara Watershed (Wisconsin, USA)—a Midwestern landscape that typifies tensions between agriculture, urban development, and freshwater resources.

Methods

Spatial extent of water policy implementation was mapped, and indicators of hydrologic services were quantified for subwatersheds using empirical estimates and validated spatial models.

Results

We found a spatial misfit between the overall spatial implementation of water policy and regions of water quality concern, indicating a need for better targeting. Water quality policies can also be leveraged to protect other hydrologic services such as freshwater supply and flood regulation. Individual policy application areas varied substantially in their spatial congruence with each hydrologic service, indicating that not all services are protected by a single policy and highlighting the need for a broad spectrum of policies to sustain hydrologic services in diverse landscapes. We also identified where future policies could be targeted for improving hydrologic services.

Conclusions

Joint spatial analysis of policies and ecosystem services is effective for assessing spatial aspects of institutional fit, and provides a foundation for guiding future policy efforts.

     

Resource depletion versus landscape complementation: habitat selection by a multiple central place forager

Context

The spatial distribution of non-substitutable resources implies diverging predictions for animal movement patterns. At broad scales, animals should respond to landscape complementation by selecting areas where resource patches are close-by to minimize movement costs. Yet at fine scales, central place effects lead to the depletion of patches that are close to one another and that should ultimately be avoided by consumers.

Objectives

We developed a multi-scale resource selection framework to test whether animal movement is driven by landscape complementation or resource depletion and identify at which spatial scale these processes are relevant from an animal’s perspective.

Methods

During the dry season, surface water and forage are non-substitutable resources for African elephants. Eight family herds were tracked using GPS loggers in Hwange National Park, Zimbabwe. We explained habitat selection during foraging trips by mapping surface water at two scales with gaussian kernels of varying widths placed over each waterhole.

Results

Unexpectedly, elephants select areas with low waterhole density at both fine scales (< 1 km) and broad scales (5–7 km). Selection is stronger when elephants forage far away from water, even more so as the dry season progresses.

Conclusions

Elephant selection of low waterhole density areas suggests that resource depletion around multiple central places is the main driver of their habitat selection. By identifying the scale at which animals respond to waterhole distribution we provide a template for water management in arid and semi-arid landscapes that can be tailored to match the requirements and mobility of free ranging wild or domestic species.

     

Distribution of invasive plants in urban environment is strongly spatially structured

Context

Urban environments create a wide range of habitats that harbour a great diversity of plant species, many of which are of alien origin. For future urban planning and management of the green areas within the city, understanding of the spatial distribution of invasive alien species is of great importance.

Objectives

Our main aim was to assess how availability of different ecosystem types within a city area, as well as several parameters describing urban structure interact in determining the cover and identity of invasive alien species.

Methods

We studied the distribution of chosen invasive plant species in a mid-sized city in the Czech Republic, central Europe, on a gradient of equal sized cells from the city centre to its outskirts.

Results

A great amount of variation was explained by spatial predictors but not shared with any measured variables. The species cover of invasive species decreased with increasing proportion of urban greenery and distance from the city centre, but increased with habitat richness; road margins, ruderal sites, and railway sites were richest in invasive species. In contrast, the total number of invasive species in cells significantly decreased with increasing distance from the city centre, but increased with habitat richness.

Conclusions

Our results suggest that different invasive species prefer habitats in the vicinity of the city centre and at its periphery and the spatial structure and habitat quality of the urban landscape needs to be taken into account, in efforts to manage alien plant species invasions in urban environments.