2,384 research outputs found
Urbanisation lowers great tit Parus major breeding success at multiple spatial scales
While numerous studies have reported negative effects of urbanisation on birds, few have examined the role of urban scale in influencing breeding success. Furthermore, many studies have relied on qualitative rather than quantitative assessments of urbanisation. This study sought to address these issues by testing the effects of urbanisation, measured at two spatial scales, on the breeding success of great tits Parus major. A nested study design, incorporating over 400 nestboxes, was used in study sites across northern Belgium with a priori quantified degrees of urbanisation at both local and regional scales. All measured breeding parameters were found to vary at one or both spatial scales of urbanisation; in more urbanised areas great tits displayed advanced laying dates but lower breeding success compared to rural areas, with smaller clutch sizes, lower nestling masses and fewer fledglings per egg. Importantly, urbanisation effects were not limited to big cities as birds breeding in gardens or parks in small towns also had comparatively low success. We found that both regional- and local-scale urbanisation had consistent significant effects on laying date, clutch size and nestling mass, while the number of fledglings per egg was negatively influenced by local-scale urbanisation only. Results of this study therefore highlight the importance of utilising multiple spatial scales in analysing urbanisation effects, as well as the potential negative impact of local urbanisation on breeding success. This calls for further investigation into mechanisms driving urbanisation effects and how these may vary at different scales
A Space-For-Time (SFT) Substitution Approach to Studying Historical Phenological Changes in Urban Environment
abstract: Plant phenological records are crucial for predicting plant responses to global warming. However, many historical records are either short or replete with data gaps, which pose limitations and may lead to erroneous conclusions about the direction and magnitude of change. In addition to uninterrupted monitoring, missing observations may be substituted via modeling, experimentation, or gradient analysis. Here we have developed a space-for-time (SFT) substitution method that uses spatial phenology and temperature data to fill gaps in historical records. To do this, we combined historical data for several tree species from a single location with spatial data for the same species and used linear regression and Analysis of Covariance (ANCOVA) to build complementary spring phenology models and assess improvements achieved by the approach. SFT substitution allowed increasing the sample size and developing more robust phenology models for some of the species studied. Testing models with reduced historical data size revealed thresholds at which SFT improved historical trend estimation. We conclude that under certain circumstances both the robustness of models and accuracy of phenological trends can be enhanced although some limitations and assumptions still need to be resolved. There is considerable potential for exploring SFT analyses in phenology studies, especially those conducted in urban environments and those dealing with non-linearities in phenology modeling.The article is published at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.005126
Wildlife Use of Vernal Pools in an Urbanizing Landscape with a Focus on Population Vitality of Vernal Pool-breeding Amphibians
Vernal pools in the northeastern United States provide essential habitat for pool-breeding amphibians and provide resources for other forest-dwelling wildlife. These pools and pool-breeding amphibians in particular are threatened by land conversion associated with urbanization and urban-associated factors. The responses of these amphibians and of birds and mammals using vernal pools to intermediate levels of urban development are largely unknown. I used field observations and lab experiments to study the amphibians, birds, and mammals associated with vernal pools along an urban development gradient in greater Bangor, Maine.
In Chapter 1, I examined bird and mammal use and assemblage composition at 33 pools, with specific focus on the influence of impervious surface as an indicator of urbanization intensity. I detected 59 bird and mammal species using pools and the adjacent terrestrial areas. Within-pool vegetation and land cover types within 1,000 m of pools likely influenced assemblages with increases in impervious cover linked to shifts towards urban-affiliated species.
Chapters 2 focused on the associations between site characteristics in an urbanizing landscape and wood frog (Lithobates sylvaticus) larval morphology and survival. Differences in morphology were associated with urban land conversion, hydrology, within-pool vegetation, and conspecific density. Urbanization was associated with greater tadpole survival, development rate, and size.
In Chapter 3, I examined the carry-over effects of larval morphology and site characteristics, particularly urban-associated land conversion within 1,000 m, on newly emerged and post-breeding male wood frogs in 15 pools. Egg density had a salient influence with negative effects on larval and froglet responses, and the effects of urban-associated cover near pools at larval and adult stages suggest that the carry-over effects of urbanization from larval to froglet stages may not persist to adulthood.
Chapter 4 addresses the effects of urban-associated land conversion and road salt on breeding effort of wood frog, spotted salamander (Ambystoma maculatum), and the blue-spotted salamander (including the unisexual complex, Ambystoma laterale-jeffersonianum). All three taxa responded negatively to tree cover reduction, but had some positive responses that are indicative of the removal of breeding pools 300-1,000 m from a study pool resulting in displaced adults consolidating breeding in remaining pools
Wildlife Use of Vernal Pools in an Urbanizing Landscape with a Focus on Population Vitality of Vernal Pool-Breeding Amphibians
Vernal pools in the northeastern United States provide essential habitat for pool-breeding amphibians and provide resources for other forest-dwelling wildlife. These pools and pool-breeding amphibians in particular are threatened by land conversion associated with urbanization and urban-associated factors. The responses of these amphibians and of birds and mammals using vernal pools to intermediate levels of urban development are largely unknown. I used field observations and lab experiments to study the amphibians, birds, and mammals associated with vernal pools along an urban development gradient in greater Bangor, Maine.
In Chapter 1, I examined bird and mammal use and assemblage composition at 33 pools, with specific focus on the influence of impervious surface as an indicator of urbanization intensity. I detected 59 bird and mammal species using pools and the adjacent terrestrial areas. Within-pool vegetation and land cover types within 1,000 m of pools likely influenced assemblages with increases in impervious cover linked to shifts towards urban-affiliated species.
Chapters 2 focused on the associations between site characteristics in an urbanizing landscape and wood frog (Lithobates sylvaticus) larval morphology and survival. Differences in morphology were associated with urban land conversion, hydrology, within-pool vegetation, and conspecific density. Urbanization was positively associated with greater tadpole survival, development rate, and size.
In Chapter 3, I examined the carry-over effects of larval morphology and site characteristics, particularly urban-associated land conversion within 1,000 m, on newly emerged and post-breeding male wood frogs in 15 pools. Egg density had a salient influence with negative effects on larval and froglet responses, and the effects of urban-associated cover near pools at larval and adult stages suggest that the carry-over effects of urbanization from larval to froglet stages may not persist to adulthood.
Chapter 4 addresses the effects of urban-associated land conversion and road salt on breeding effort of wood frog, spotted salamander (Ambystoma maculatum), and the blue-spotted salamander (including the unisexual complex, Ambystoma laterale-jeffersonianum). All three taxa responded negatively to tree cover reduction, but had some positive responses that are indicative of the removal of breeding pools 300-1,000 m from a study pool resulting in displaced adults consolidating breeding in remaining pools
A dataset of 30-meter annual vegetation phenology indicators (1985–2015) in urban areas of the conterminous United States
Fine-resolution satellite observations show great potential for characterizing seasonal and annual dynamics of vegetation phenology in urban domains, from local to regional and global scales. However, most previous studies were conducted using coarse or moderate resolution data, which are inadequate for characterizing the spatiotemporal dynamics of vegetation phenology in urban domains. In this study, we produced an annual vegetation phenology dataset in urban ecosystems for the conterminous United States (US), using all available Landsat images on the Google Earth Engine (GEE) platform. First, we characterized the long-term mean seasonal pattern of phenology indicators of the start of season (SOS) and the end of season (EOS), using a double logistic model. Then, we identified the annual variability of these two phenology indicators by measuring the difference of dates when the vegetation index in a specific year reaches the same magnitude as its long-term mean. The derived phenology indicators agree well with in-situ observations from PhenoCam network and Harvard Forest. Comparing with results derived from the moderate resolution imaging spectroradiometer (MODIS) data, our Landsat derived phenology indicators can provide more spatial details. Also, temporal trends of phenology indicators (e.g., SOS) derived from Landsat and MODIS are consistent overall, but the Landsat derived results from 1985 have a longer temporal span compared to MODIS from 2001. In general, there is a spatially explicit pattern of phenology indicators from the North to the South in cities in the conterminous US, with an overall advanced SOS in the past three decades. The derived phenology product in the US urban domains at the national level is of great use for urban ecology studies for its fine spatial resolution (30 m) and long temporal span (30 years). The data are available at https://doi.org/10.6084/m9.figshare.7685645.v2
Plant-pollinator communities responsive to local and landscape level factors in grassland restorations.
As humans continue to degrade natural ecosystems via greenhouse gas emissions and habitat destruction, many species are being pushed to the brink of extinction. In hopes to offset this degradation, habitat restoration attempts to restore ecosystem function to an improved state resembling intact, remnant values. This is a difficult, but important, undertaking with factors to consider at multiple spatial and temporal scales. The restoration and conservation of pollinator communities has garnered heightened attention because of the valuable ecosystem services they provide. This dissertation investigates the local and landscape level factors of grassland restorations that influence plant-pollinator communities. I used a combination of approaches, including large dataset compilation, and field surveys of local plant and animal communities. This work tells a nuanced story of how plant-pollinator communities are influenced by humans, but also how we can offset the most detrimental effects. Specifically, grassland restorations have the potential to increase pollinator abundance and species richness values compared to degraded grasslands. Furthermore, the surrounding land usage and quality of these restorations play an important role in their functionality. Restorations with higher plant richness and a higher proportion of native plants were able to support more robust plant and pollinator communities. Additionally, restorations nested within urban areas experienced increased stress, indicating increased support may be warranted. This work highlights the importance of high-quality restorations for the preservation of our pollinator communities. If we are to protect some of the most important species in the world, we must effectively restore the ecosystems they rely on
Climate-driven change in Himalayan Rhododendron phenology
Phenology – the seasonal timing of life-history events – is a critical dimension of natural history. It is also one of the earliest and most noticeable traits by which organisms respond to climate change. However, these responses are complex, and only beginning to be understood, especially in the montane and alpine environments that are among the ecosystems most vulnerable to climate change. Drawing from diverse data sets and employing multiple methodologies, I examined how climate affects phenology in Himalayan Rhododendron spp. Comprehensively monitoring flowering phenology over gradients of season and elevation on Mt. Yulong, China – home to a diverse assemblage of Rhododendron spp. that is ecologically and culturally salient – I showed that the species have an elaborate sequenced progression of flowering over season and elevation. Both phenology and the responses to annual temperatures directly impact reproductive success, making this progression vulnerable to the effects of future climate change. A community phylogeny suggests this flowering progression experiences constraints from shared evolutionary history and morphology: the last flowering day of each species shows phylogenetic signal, and is associated with flower size and fruit size. This pattern may be driven by the limited time for fruit development before the onset of cold temperatures in autumn, underscoring the asymmetric pressures on phenology at seasonal extremes. To gain a longer-term perspective, I contextualized Rhododendron phenological progressions within a 125 year proxy record of phenology based on herbarium collections, demonstrating that although increased annual temperatures are associated with earlier flowering, increased fall temperatures are associated with delayed flowering. These contrasting effects have resulted in opposing changes in flowering time, even during rapid recent anthropogenic warming. Finally, interviews with Mt. Yulong villagers revealed a rich knowledge base, with local understandings of changes in and drivers of Rhododendron phenology paralleling the results from ecological studies. In combination, these studies reveal the complexity of phenological responses to climate change. The multiple methodologies allowed a deeper exploration than simple ‘earlier spring’ models of phenological response. Each illuminated distinct details, while agreement among diverse data sources increased confidence in both the methodologies and the conclusions
Phenotypic signatures of urbanization are scale-dependent : a multi-trait study on a classic urban exploiter
Understanding at which spatial scales anthropogenic selection pressures operate most strongly is a prerequisite for efficient conservation and management of urban biodiversity. Heterogeneity in findings on the strength and direction of urbanization effects may result from a lack of consensus on which spatial scales are most adequate when studying biotic effects of urbanization. Therefore, here, using the house sparrow (Passer domesticus) as model, we test the hypothesis that more than one spatial scale will explain variation among phenotypic stress markers. By applying a unique hierarchical sampling design enabling us to differentiate between local and regional effects of urbanization, we here show that the strength and direction of relationships with the percentage of built-up area - a simple structural measure of urbanization - vary among phenotypic stress markers and across the spatial range over which urbanization is measured. While inverse relationships with scaled body mass and bill height of adult house sparrows (Passer domesticus) were strongest when the degree of urbanization was quantified at city-level, similar relationships with corticosterone concentrations in feathers were only detected at the scale of individual home ranges. In contrast, tarsus length, wing length, and two measures of feather development were not significantly related to urbanization at any spatial scale. As the suite of phenotypic stress markers applied in this study revealed signatures of urbanization over a broad spatial range, we conclude that measures aimed at mitigating impacts of urbanization on free-ranging populations should best be implemented at multiple spatial scales too
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