This dissertation examines the relationship between abundances of Roanoke darter, Roanoke logperch, and black jump rock and availability of stream habitat features at three spatial scales in two reaches of the Roanoke River, Virginia. The utility of underwater observation as a method of estimating benthic fish densities is also assessed. Distributions of perpendicular sighting distances indicate models assuming equal sighting probability are not appropriate for benthic species but distance sampling models assuming decreased sighting probability with increased distance from observers provide reasonable alternatives. Abundances estimated using two distance sampling models, a strip transect model, and a backpack electroshocker were strongly correlated. At the microhabitat scale (45 m² cells), differential use of depth, velocity, substrate, and siltation level by all three species during summer low flows was evident. Habitat use characteristics were not transferable, as depths and velocities associated with high fish densities varied between reaches. Univariate and multivariate habitat suitability indices gave similar rankings for combinations of the four habitat variables, but site suitabilities based on these indices were poor predictors of fish abundance. Habitat cells were not selected independently of surrounding habitat characteristics, as fish densities were highest in target cells adjacent to cells with preferred microhabitat characteristics. Roanoke darter and black jumprock abundances were highest at sites where preferred microhabitat patches were non-contiguous while contiguity had no effect on logperch abundance. Multiple regressions showed area of suitable habitat and patch contiguity accounted for 42 %, 34 %, and 33 % of variation in darter, logperch, and jumprock abundances, respectively. Estimates of area of target riffles, area of pools and riffles upstream and downstream of target riffles, and depth, velocity, and substrate characteristics of pools and riffles immediately upstream and downstream of target riffles were obtained. Fish densities were correlated with at least one measure of proximal habitat for all three species. Significant multiple regression models relating fish density to adjacent habitat unit characteristics were also obtained, but the explanatory power of adjacent unit variables varied among small, medium and large riffles and among species. In summary, fish abundance was related to habitat at all spatial scales but explanatory power was limited. / Ph. D.

Habitat loss, habitat fragmentation and species invasions have been recognized as three of the leading threats to biodiversity. I examined the effects of habitat loss and fragmentation on native and invasive plants in central Texas. During the last century, the density and abundance of woody plants has been increasing in the savannas of eastern Edwards Plateau. This process, known as woody plant encroachment, not only reduces the amount of open herbaceous habitat but also fragments that habitat creating smaller and more isolated patches. In three studies, I investigated the consequences of this habitat loss and fragmentation for plants which do not occur under the cover of woody plants including native grasses and forbs and the invasive Eurasian bunchgrass, Bothriochloa ischaemum (King Ranch Bluestem). In the first study, I show that woody plant encroachment reduces native herbaceous species richness (the number of species in a given area). Using a collection of historical aerial photographs, I demonstrate that current native herbaceous species richness was most strongly related to recent habitat amount, but to the degree of habitat fragmentation at least 50 years ago. In a second study, I show that the presence of B. ischaemum was negatively related to the degree of fragmentation in the surrounding landscape. Finally, I found that B. ischaemum had higher rates of germination and growth in experimental plots where the species commonly lost with woody plant encroachment were removed than in unmanipulated control plots. Together, this work suggests that woody plant encroachment is directly slowing the spread of an invasive species while indirectly facilitating its establishment. / text

The environmental problems facing the world today are largely attributable to anthropogenic activities and landscape change. Addressing these challenges in an evidence-based way requires an understanding of precisely how species and ecosystems are responding to human impacts. Discerning linkages between stressors and their ecological repercussions, and using this to inform conservation, can be challenging due to the complexity and uncertainty of ecological research. I focused on the responses of five wide-ranging large mammal species – gray wolf (Canis lupus), Canada lynx (Lynx canadensis), coyote (Canis latrans), white-tailed deer (Odocoileus virginianus) and moose (Alces alces) – to human footprint (measure of human infrastructure and landscape change), using 12 years (2001-2013) of snowtrack surveys conducted across the boreal forest of Alberta. I explored three key challenges to discerning the linkages between ecological dynamics and management actions. First, I asked whether the direction and magnitude of species responses vary depending on the spatial extent and grain of the study. Second, I asked whether these species respond more strongly to individual footprint features or to the cumulative effects of footprint (measured as total footprint), and whether responses to footprint are consistent across species. Third, I evaluated the utility of thresholds for large mammal management and asked whether there is evidence for consistent threshold responses to total footprint across scales. In addressing the first two questions, I evaluated a set of generalized linear mixed effects models (GLMM) relating the relative abundance of each species to individual and cumulative effects of human footprint, using an information-theoretic approach. I compared the direction of species responses across our regional study area (approximately 400,000 km2) to those reported in previous smaller-extent studies (median 1,525 km2), and compared responses across three spatial grains (250m, 1500m, and 5000m transect buffers). In addressing the third question, I conducted a review on the utility of ecological thresholds, described as abrupt changes in the response to a continuous driver, for large mammal management. I further tested for thresholds in species responses to total footprint by comparing linear models (logistic regression) to piecewise regression models. I compared threshold values between two grains (approximately 33km2 - 1500m transect buffer, and 5500km2 - grouping transects into clusters), and across four regions (boreal forest extent, three landscape planning units). I found that the direction of species responses varied with spatial extent, but not grain, and that species responded strongly to a broad suite of footprint features, indicating the need to manage for cumulative effects. Despite the appeal of ecological thresholds, using these as targets is challenging and the success of doing so has rarely been evaluated. I found threshold models to be better supported than linear ones across species, but due to variability and uncertainty in threshold values, the results are more suited as guidelines or hypotheses to be further tested, as opposed to specific management targets. Translating research on complex ecological systems into management actions is a continuing challenge, yet, ongoing biodiversity monitoring and adaptive management may refine our existing tools, and ultimately lead to better environmental stewardship. / Graduate / 2017-09-05 / 0329

Adequate access to affordable, healthy food has long been a public health concern and has become a more pressing societal issue following the Great Recession and rising incidents of diet-related diseases. In response, research and government efforts have largely focused on identifying disadvantaged areas with poor food access and formulating policies to improve accessibility. However, the approaches that have been widely relied upon by researchers and practitioners for food access assessment are severely flawed, which may lead to inconsistent research findings or neglect of the needs of under-served/un-served neighborhoods. This dissertation identifies three important aspects of food access for improvement: the appropriate scale/neighborhoods for analysis, the use of food outlets as a proxy for affordable, healthy food; and the assessment method. In particular, three studies are conducted to: (1) examine how varying spatial scales and aggregation methods affect accessibility assessments; (2) explore the role of independent grocers, which have been neglected in previous food access studies as elements of the food landscape that may change the perception of food deserts; and (3) investigate how individual-level food access patterns compare to the widely used, area-based neighborhood measures of expected accessibility. While the dissertation discusses and addresses theoretical challenges in food access, the empirical studies conducted in the Tucson, Arizona metropolitan area contribute to a better understanding of the real-world complexity of food access. The results shed light on some predicaments identified in recent studies and have important policy implications for how best to efficiently and effectively design strategies and initiatives to enhance food-provision access.

Este trabalho enfatizou as escalas espaciais de microhabitat e de mesohabitat para investigar como a fauna de macroinvertebrados aquáticos é influenciada pelas variáveis ambientais e espaciais. O primeiro capítulo trás uma visão geral da aplicabilidade das escalas de microhabitat e de mesohabitat ao avaliar a estrutura da fauna e, também, demonstra que a composição do substrato influencia a composição faunística. No segundo capítulo, realizamos uma avaliação da suficiência amostral e comparamos a diversidade alfa e beta entre métodos de coleta e entre diferentes mesohabitats. No terceiro capítulo avaliamos diferentes variáveis hidráulicas e suas relações com a abundância de indivíduos e a riqueza de táxons considerando as escalas espaciais de microhabitat e mesohabitat. Observamos que as condições hidráulicas foram importantes na estruturação da comunidade de macroinvertebrados, influenciando positivamente a abundância de indivíduos e negativamente a riqueza de táxons nos microhabitats. No quarto capítulo nos baseamos na teoria de metacomunidades para compreender a influência das variáveis ambientais e espaciais na estruturação da fauna em uma perspectiva de microescala. Além da esperada importância do ambiente para a microdistribuição dos organismos, identificamos uma forte influência do espaço na estruturação da fauna. Nossos resultados demonstraram que a fauna de macroinvertebrados aquáticos é estruturada pela composição do substrato, condições hidráulicas e fatores espaciais, todas estas condições perceptíveis na escala do microhabitat. Deste modo, a microescala pode ser considerada como uma perspectiva válida para o estudo de ecologia de riachos. / We focused on the microhabitat and the mesohabitat spatial scales to investigate the environmental and spatial features influence on aquatic macroinvertebrate fauna. The first chapter brings an overview about the microhabitat and mesohabitat applicability to evaluate the fauna structure. Likewise, it shows the substrate influence on the fauna composition. In the second chapter, we evaluate the sampling sufficiency and compare the alpha and beta diversity among the sampling methods and mesohabitats. In the third chapter we evaluated the hydraulic features and its relationships with abundance and richness considering the microhabitat and mesohabitat spatial scales. Our results show that the hydraulic conditions have influence on macroinvertebrate community structure, showing a positive relationship with abundance and negative with microhabitat richness. In the fourth chapter, we applied the metacommunity theory in the microhabitat scale to understand the hole of environmental and spatial features on the community structure. Further than the expected environmental influence on organisms microdistribution, we identified a strong spatial influence on the fauna structure. Our results showed that the aquatic macroinvertebrate fauna was structured by the substrate composition, hydraulic conditions and spatial features. All this conditions are noticeable on microhabitat spatial scale. Accordingly, the microhabitat scale can be considered as an effectual perspective to the stream ecology.

The ecosystem services (ES) concept is meant to facilitate consideration of the value of nature in conservation and landscape management processes by translating ecosystem functions into human benefits. Incorporating the ES concept into policy and decision-making has proven difficult due to challenges in identifying, measuring, and locating services and in predicting the impacts of decisions upon them. ES mapping offers a key solution to increase our understanding of the spatial patterns of ES supply and demand and the spatial relationships between them, but may be challenging to implement given a lack of spatial data related to ES or existence of such data at coarse resolution that may not facilitate accurate ES quantification, mapping and modeling. This issue is particularly acute in urban settings where landscapes are highly heterogeneous and fragmented. This research seeks to improve our understanding of urban ES supply, demand and the relationships between them, as well as the impacts of spatial scale, input data quality and method choice on ES mapping in urban landscapes. The dissertation is composed of three studies. In the first study, I introduce a spatially-explicit framework for quantifying and mapping ES supply and demand using carbon storage and sequestration services as an example. This framework assesses supply based on biophysical conditions and demand based on socioeconomic characteristics, allowing for more integrative ES assessments in urban areas. In the second study, I evaluate the sensitivity of ES maps to input spatial data resolution and method choice (ecosystem component-based and land-cover proxy-based methods) in a heterogeneous urban landscape using biomass carbon storage as an example. I find that ES map accuracy is highly dependent on analytical scales and input data representativeness. ES estimates based on ecosystem-component data are more accurate than those based on land-cover proxies. The accuracy of land-cover proxy-based maps, however, can be increased by using high-resolution land-cover maps. The third study aims to increase understanding of ES supply, demand, and supply-demand balance in urban contexts. To this end, I create a high-thematic-resolution land-cover dataset and combine it with the InVEST pollination model to assess the capacity of urban ecosystems to supply pollination services to satisfy the demands of urban agriculture. I find using land-cover dataset at a higher thematic resolution enhances the accuracy of pollination estimates, highlighting the importance of considering scale and land-use dependencies in urban ES mapping. Combined, these studies advance our knowledge of ES supply, demand and the relationships between them, and provide new insight into the impacts of input data spatial and thematic resolution and method choice on the accuracy of urban ES maps.

This study examined modifications made by Pogonomyrmex barbatus, by their processes of granivory and nest construction, to forb and grass dynamics under large-scale disturbances of fire, recent drought and long-term, large-mammalian herbivory using comparative studies, field experimental manipulations, and a simulation model on the Edwards Plateau, Texas. Ant nests are refugia for grass survival during extreme droughts as demonstrated during the drought of 1998 to 2002. Significantly greater cover of grasses and lower abundance and cover of forbs was found beside nests compared with surrounding habitat throughout the drought and recovery. Grasses near nests may be the seed source for surrounding habitats during recovery. Seeds were differentially collected among most forbs and grasses despite seed abundance. Harvest was significantly reduced in the fall relative to spring. During preference experiments, harvest differences were found between grazing treatments for two of four species, but only during the spring. High lipid content seeds were unpreferred in fall compared to high protein and carbohydrate content seeds. Granivory influences on seedling establishment were studied by comparing seedling recruitment among sown and naturally occurring seeds excluded and open to foragers. Exclosures were placed in three nest densities and two burn treatments. Seeds in exclosures produced significantly more seedlings than open arenas only during the first year of drought recovery. Densities of grasses and annual forbs were higher in open arenas the second year due to indirect effects of granivory. By reducing seeds ants release seedlings from competition. Sown seedling abundance was unaffected by colony density and fire. Colony density and distribution were influenced by topography, soil types, soil depth and woody cover, but not by historical grazing treatments. Cleared vegetation on nest disks impacted less than 1% of total surface area and losses were compensated by greater basal cover of grasses next to disks compared to surrounding habitats. Foraging areas influenced 17.3-73.6% of surface area and could diminish seed populations for potential seedlings. Model results agree with experimental observations that communities may be modified by P. barbatus presence due to differential responses of grass species to interaction between nests or granivory and rainfall amounts.

Ecology has been devoted to defining the content of a species’ environment. Defining the extent, or size, of a species’ environment is also pivotal to elucidating species-habitat relationships. More than a home range, this extent integrates an individual’s lifetime experiences with resources, competition, and predators. I theorised that a species’ habitat extent is identifiable from its characteristic spatial scale of habitat selection, which in turn is predicted by body size. I reviewed scale-dependent mammalian habitat selection studies and found that a characteristic scale was typically not identified, but identifiable. Of several ecological predictors tested, only body mass was a significant predictor of the relative size of a species’ characteristic habitat selection scale. Tests of existing data are confounded by differing approaches, so I empirically tested the scale-body mass hypothesis using a standardised survey of 12 sympatric terrestrial mammal species from the Canadian Rocky Mountains. For each species, support for habitat models varied across 20 scales tested. For six species, I found a characteristic selection scale, which was best predicted by species body mass in a quadratic relationship. Occurrence of large and small species was explained by habitat measured at large scales, whereas medium- sized species were explained by habitat measured at small scales. The relationship between body size and habitat selection scale is congruent with the textural-discontinuity hypothesis, and implies species’ evolutionary adaptation to landscape heterogeneity as the driver of scale-dependent habitat selection. I applied this principle to examine wolverine habitat selection, and found that anthropogenic fragmentation of the landscape influences that species’ occurrence in space at large spatial scales. Finally, I contended that the prevailing paradigm equating habitats to resources omits interspecific interactions that are key predictors of a species’ occurrences. I examined habitat selection of martens and fishers in terrestrial environments, and sea otters in marine coastal environments, and tested whether the presence of heterospecifics could explain spatial occurrence beyond landscape structure and resources. In both cases, the presence of heterospecifics explained species occurrence beyond simple resource selection. Interspecific interactions are key drivers of a species’ distribution in space; this is the spatial expression of the concepts of fundamental and realized niches. Body size interacts with landscape structure to determine the scale of a species’ response to its environment, and within this habitat extent, interspecific interactions affect the species’ pattern of occurrence and distribution. / Graduate

Source water protection is a key component of the multiple barrier approach to drinking water. The management of contamination within source water ecosystems is associated with many benefits but also several challenges. By its very nature, source water protection is site specific and requires the cooperation of numerous watershed stakeholders to ensure sufficient financial resources and social will. This work focused on two critical aspects of source water protection: 1) The facilitation of effective communication to promote cooperation among watershed stakeholders and aid in public education programs. A drinking source water quality index presents a potential communication and analysis tool to facilitate cooperation between diverse interest groups as well as represent composite source water quality. I tested the effectiveness of the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) in capturing expert assessments of surface drinking source water quality. In cooperation with a panel of drinking water quality experts I identified a core set of parameters to reflect common Canadian surface source water concerns. Based upon existing source water guidelines, drinking source water target values were drafted for use in the index corresponding to two basic treatment levels. Index scores calculated using the core parameter set and associated source water target values were strongly correlated with expert assessments of source water quality. Amended with a modified index calculation procedure to accommodate parameters measured at different frequencies within any particular study period, the CCME WQI provides a valuable means of monitoring, communicating, and understanding surface source water quality. 2) The application of source water protection strategies to the appropriate spatial scale in order to manage contaminants of concern in a cost effective manner. Using data gathered from 40 Canadian rivers across 4 western Canadian ecozones I examined the spatial scales at which landuse was most closely associated with drinking source water quality metrics. Linear mixed effects models revealed that different spatial areas of landuse influence drinking source water quality depending on the parameter and season investigated. Microbial risk, characterized using E. coli measures, was only associated with landuse at the local spatial scale. Turbidity measures exhibited a complex association with landuse suggesting that the landuse areas of greatest influence can range from the local to the watershed scale. Total organic carbon concentrations were only associated with landuse characterized at the entire watershed scale. The validated CCME WQI was used to provide a composite measure of seasonal drinking source water quality but did not provide additional information beyond the analyses of individual parameters. These results suggest that entire watershed management is required to safeguard drinking water sources with more focused efforts at targeted spatial scales to reduce identified risk parameters. The source water protection tools and knowledge that I present have immediate application within Canada. Practitioners must be aware of the limitations of the CCME WQI however it provides a validated means of communicating complex source water quality information to non-specialized end users. Combined with the scale dependency of landuse-source water relationships that I elucidated, water quality managers can target contaminant reduction strategies in a more cost-effective manner and relay water quality status and trends to concerned groups. / Graduate

Florida’s seagrasses are ecologically important marine environments which have suffered major degradation caused by increasing anthropogenic pressures. A 2011 seagrass die-off event caused by an algal bloom in the Florida Indian River Lagoon (IRL) was particularly severe with a majority of seagrass lost in areas such as the Banana River. An understanding of how this coastal marine environment changed is an important step toward better managing resources for conservation. Modern tools and methods provide new opportunities to study these changes at the landscape scale, a scale that informs on the larger more comprehensive state of a system. Classified satellite imagery and spatial landscape metrics were used to quantify changes in IRL Banana River seagrass landscape patterns following the die-off event. Thirty-six landscape metrics in four categories (Area-Edge, Shape, Core Area and Aggregation) were used to discern the spatial complexities of habitat changes over space and time in the IRL study area. Seagrass loss from 2011 to 2013 based on image classifications was as high as 91% in the Banana River study areas. Landscape metrics indicate that following the seagrass die-off in the IRL, meadows became more fragmented, patches became more isolated, and the amount and spatial complexity of meadow edge was reduced. For the most part, these landscape structural changes in the IRL increased with more severe amounts of seagrass loss. The metrics were evaluated and scored for their effectiveness in detecting seagrass landscape changes and their ability to provide consistent detection with variable resolution imagery. The top metrics in order of highest evaluation score were Total Edge, Splitting Index, Total Core Area, Effective Mesh Size, Landscape Shape Index, Edge Density, Perimeter-Area Ratio Distribution, Average Core Area, Disjunct Core Area Distribution Mean and Patch Shape Index. Area-edge and aggregation type metrics were identified as the best metrics for evaluating landscape changes under different degrees of seagrass loss in the IRL. Landscape metrics applied to classified images have the ability to provide quantitative and informative techniques for monitoring seagrass health.