Browsing by Subject "urban ecology"

Now showing 1 - 5 of 5
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    Birds & Buildings: Bird-Window Collisions in the Urban Landscape
    (2018-06) Nichols, Kathryn
    Bird collisions with buildings are the second largest anthropogenic source of direct mortality for birds (365-988 million birds killed annually in the United States). To investigate the factors that affect bird-building collisions from both the building and the avian perspective, I make use of the high quality avian collision data collected by a citizen science effort to monitor and rescue birds that collide with buildings: Minnesota Project BirdSafe. Through the program, citizen scientists walked routes in Saint Paul and Minneapolis that include buildings almost daily spring and fall migration for 10 years. I used the data collected by these citizen science volunteers to assess building and landscape factors contributing to bird-building collisions and to identify patterns in bird-building collisions based on taxonomy and behavior of birds. Findings from building and landscape analysis highlight importance of differences in building collision dynamics between spring and fall migration, the increased risk of collisions for buildings that are close to migratory stopover habitat, and using edge:area ratio of buildings rather than percent glass as a predictor of bird-building collisions. Findings from analyses of avian risk for collisions indicate that birds that predominately migrate during the day have a decreased risk of building collisions despite peak collision numbers occurring during early morning. Additionally, for many species, local abundance is the predominant determining factor for collision risk. However, for ~20% of species studied, the family, genus, and/or species of a bird may increase or decrease collision risk beyond what would be expected from abundance alone. Lastly, comparative analysis of multiple sources of avian abundance data (local point count, local banding data, eBird data, and Breeding Bird Survey data) reveal generally comparable results when used for analysis of bird-building collision risk; thus while current understanding of species collision risk is spatially restricted, but pre-existing citizen science data could allow for analyses in any location with bird-building collision data; improving our understanding of which birds are most in need of protection from bird-building collisions.
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    Land Cover Shapefiles for Minneapolis and St. Paul, Minnesota
    (2018-10-26) Anderson, Abigail W; McLachlan, K; awoodsanderson at g m a i l (dot) com; Anderson, Abigail W
    This project’s aim was to produce a land cover model of downtown Minneapolis and St. Paul, Minnesota. Our purpose was to discriminate features that offer potential cover and foraging habitat for birds (i.e. trees, shrubs, turf grass, water) from features that are less suitable for birds (i.e. impervious surfaces and buildings). Though we had birds in mind, the models we produced have broad utility in many contexts. To achieve our objectives, we integrated a variety of freely available spatial data. Object-based Image Analysis (OBIA) was the primary methodology we used to generate thematic land cover models.
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    Modeling Bird-Window Collisions in Core Urban Environments
    (2018-12) Anderson, Abigail
    Birds contribute to ecosystem function and deliver ecosystem services to human societies. However, birds are threatened by multiple anthropogenic stressors. Although window strikes are only one among many threats, they have received attention, a prominent example being public concern that the U.S. Bank Stadium’s massive glass gates could result in bird deaths. We can mitigate bird–building collision mortality with bird-safe glass. However, targeted intervention requires models that predict where losses are greatest. With this objective, I assessed spatial drivers of collisions using data provided by research partner Audubon Minnesota. These data, collected by volunteer citizen scientists and skillfully managed by staff, recorded bird collisions in the Twin Cities during migration seasons (2007–2016). I assessed the influence of vegetation on collisions while also exploring how spatial scale affected that relationship. In addition, I compared collisions at skyways versus buildings. To complement this spatial study, I conducted a distinct investigation in the same location during the breeding season (2016). I measured local bird abundance using point counts, and concurrently, surveyed the area for collisions. Of 14 total species, only 3 were counted both alive and in collisions. I used generalized linear mixed models to determine that after abundance is accounted for, species designations did not explain collision counts. However, a trait that may influence collision susceptibility is body mass, suggesting that small birds are more likely to collide than large birds. Lastly, I estimated that 6% of local birds succumb to collisions. Although cities contain hazards for birds and other wildlife, they also contain observers who can help shed light on how ecological processes are affected by urbanization. This is especially relevant in our increasingly urbanized world where conservationists engage city dwellers to protect and appreciate biodiversity.
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    Multiple element limitation of primary producer communities across ecosystems and contribution of leaf litter to nutrient export during winter months in an urban residential watershed
    (2017-08) Bratt, Anika
    Human alteration of global macronutrient availability is well documented. Compared to pre-industrial levels, anthropogenic creation of biologically reactive nitrogen (N) has increased twelve fold and phosphorous (P) inputs to terrestrial systems have doubled. Additionally, it is well understood that N and P limit primary productivity globally across ecosystems, and recent meta-analyses have demonstrated that primary producer response to nutrient manipulation most frequently supports co-limitation by N and P. However, the role of resource availability in driving nutrient limitation of aquatic primary producer communities remains unclear, especially in freshwater ecosystems subject to human perturbation. To address this knowledge gap, we determined how resource availability influences nutrient limitation by N and P of phytoplankton primary production in aquatic communities across 12 lakes in Minnesota. Despite large differences in land use (agricultural, urban, and suburban) and water column N and P availability, planktonic algal community response to nutrient manipulation was consistently characterized by co-limitation by N and P across years and months. Higher lake primary production was associated with a stronger, positive response to N+P addition. These results support the emerging body of literature on co-limitation. However, few studies have explored beyond a two-nutrient approach to assess effects of other nutrients (e.g. K, Si, Ca) in limiting primary productivity. We performed a meta-analysis using 120 fertilization studies that tested the effects of N, P, and “other” nutrients (anything other than N and P) additions on primary productivity. We found that additions of other nutrients significantly increased primary production when added with N and P, and additions of two other nutrients significantly increased primary production compared to additions of one other nutrient. These results demonstrate that co-limitation by other nutrients is more prevalent across ecosystems than previously assumed. Taken together, these chapters of my dissertation research further supports the emerging paradigm shift towards co-limitation of primary production across ecosystems, especially in freshwaters.
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    Nutrient transport, transformation, and retention in urban landscapes
    (2014-08) Nidzgorski, Daniel
    Urban nutrient sustainability faces challenges of both too much and too little: Excess nutrient loading to the environment can degrade ecosystem functions and impact human health, while at the same time depleting nonrenewable nutrient sources and moving nutrients into unrecoverable pools. Most studies and efforts to date have focused on source reduction, identifying and reducing the largest drivers of carbon (C), nitrogen (N), and phosphorus (P) consumption. However, this addresses only one aspect of urban nutrient cycling; processes that transport, transform, or retain nutrients also determine their eventual fate as pollution, inert storage, or recycling. The first chapter examined C, N, and P output fluxes from ~2,700 households in the Twin Cities metropolitan area (Minneapolis-Saint Paul, Minnesota, USA), and tracked these fluxes through various transformations in the waste streams to their eventual fates. We found few opportunities to redirect pollutant fluxes to either inert storage or recycling; reducing household nutrient pollution must rely primarily on reducing consumption. High pollution fluxes were driven not only by household nutrient outputs, but also by waste-management practices (e.g. septic vs. sewer) and spatial considerations. In contrast, we found substantial opportunities to increase household N and P recycling by ten-fold, which could potentially exceed household inputs of N and P in food. To complement this study of opportunities for improving nutrient waste management, the second and third chapters examined opportunities to manage the biophysical environment - specifically, the urban forest - to reduce nutrient pollution. We focused on the role of urban trees driving N and P movement from land to water, both leaching to groundwater and loading to stormwater. In the second chapter, we compared nutrient leaching under 33 trees of 14 species, as well as open turfgrass areas, and explored correlations with soil nutrient pools and plant functional traits. Trees had similar or lower N leaching than turfgrass in 2012 but higher N leaching in 2013; trees reduced P leaching compared with turfgrass in both 2012 and 2013, deciduous trees more than evergreens. Scaling up our measurements to the Capitol Region Watershed (~17,400 ha), we estimated that trees reduced P leaching to groundwater by 533 kg in 2012 and 1201 kg in 2013. Removing the same amounts of P with stormwater infrastructure would cost $2.2 million and $5.0 million per year, respectively. In the third chapter, we measured tree litter nutrient inputs to street gutters, which can ultimately contribute to stormwater loading, under four species of boulevard trees. Differences among tree species in the total amount of nutrients in the street gutters were driven primarily by interspecific differences in the mass of litter dropped, which were much greater than differences in litter chemistry. In developing management recommendations, we found that tree phenology is a more important consideration than litter chemistry. Cleaning up spring and autumn pulses of tree litter shortly after they fall has substantial potential to reduce nutrient inputs to stormwater; for autumn litterfall, we estimated that doing so could remove 219.0-274.4 kg N km-2 and 14.2-20.6 kg P km-2. Because of the wide variation in species' litterfall timing, achieving this goal is likely to require adjusting both boulevard tree selection and litter cleanup strategies.