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Jensen, Adam G. "Updated interstellar abundance studies and implications for dust models." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256457.
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Ensign, William E. "Multiple-scale habitat models of benthic fish abundance in riffles." Diss., Virginia Tech, 1995. http://hdl.handle.net/10919/38204.
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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.
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Forney, Karin A. "Patterns of variability and environmental models of relative abundance for California cetaceans /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9823699.
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Blanchard, Monica R. "Using Network Models to Predict Steelhead Abundance, Middle Fork John Day, OR." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4477.
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In the management of threatened and endangered species, informed population estimates are essential to gage whether or not recovery goals are being met. In the case of Pacific salmonids, this evaluation often involves sampling a small subset of the population and scaling up to estimate larger distinct populations segments. This is made complicated by the fact that fish populations are not evenly distributed along riverscapes but respond to physical and biological stream properties at varying spatial extents. We used rapid assessment survey methods and the River Styles classification to explore fish-habitat relationships at a continuous network scale. Semi-continuous surveys were conducted across nine streams in the upper Middle Fork John Day River watershed and increased the number of sites surveyed eight-fold over other monitoring methods within the watershed. Using this increased sample size and continuous habitat metrics we improved watershed-wide steelhead (Oncorhynchus mykiss) abundance models.
We first validated the distinctions among River Styles through a classification analysis using physical metrics measured at the rapid assessment sites. Overall classification accuracy, using a combination of reach and landscape scale metrics, was 88.3% and suggested that River Style classification was identifying variations in physical morphology within the watershed that was quantifiable at the reach scale. Leveraging the continuous River Styles classification of physical habitat and a continuous model of primary production improved the prediction of steelhead abundance across the network. Using random forest regressions, a model that included only habitat metrics resulted in R2 = 0.34, while using the continuous variables improved the model accuracy greatly to R2 = 0.65. Random forest allowed for further investigation into the predictor variables through the analysis of the partial dependence plots and identified a gross primary production threshold, below which production might be limiting steelhead populations. This method also identified the rarest River Style surveyed within the watershed, Confined-Valley Step Cascade, as the morphology that had the largest marginal effect on steelhead. The inherent physical properties and boundary conditions unique to each River Style has the potential to inform fish-habitat relationships across riverscapes and improve abundance estimates on a continuous spatial scale.
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Momal, Raphaëlle. "Network inference from incomplete abundance data Accounting for missing actors in interaction network inference from abundance data Tree‐based inference of species interaction networks from abundance data." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASM017.
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Les réseaux sont utilisés comme outils en microbiologie et en écologie pour représenter des relations entre espèces. Les modèles graphiques gaussiens sont le cadre mathématique dédié à l'inférence des réseaux de dépendances conditionnelles, qui permettent une séparation claires des effets directs et indirects. Cependant, les données observées sont souvent des comptages discrèts qui ne permettent pas l'utilisation de ce modèle. Cette thèse développe une méthodologie pour l'inférence de réseaux à partir de données d'abondance d'espèces. La méthode repose sur une exploration efficace et exhaustive de l'espace des arbres couvrants dans un espace latent des comptages observés, rendue possible par les propriétés algébriques de ces structures.Par ailleurs, il est probable que les comptages observés dépendent d'acteurs non mesurés (espèces ou covariable). Ce phénomène produit des arêtes supplémentaires dans le réseau marginal entre les espèces liées à l'acteur manquant dans le réseau complet, ce qui fausse la suite des analyses. Le second objectif de ce travail est de prendre en compte les acteurs manquants lors de l'inférence de réseau. Les paramètres du modèle proposé sont estimés par une approche variationnelle, qui fournit des éléments d'information pertinents à propos des données non observéesNetworks are tools used to represent species relationships in microbiology and ecology. Gaussian Graphical Models provide with a mathematical framework for the inference of conditional dependency networks, which allow for a clear separation of direct and indirect effects. However observed data are often discrete counts and the inference cannot be directly performed with this model. This work develops a methodology for network inference from species observed abundances. The method relies on specific algebraic properties of spanning tree structures to perform an efficient and complete exploration of the space of spanning trees. The inference takes place in a latent space of the observed counts.Then, observed abundances are likely to depend on unmeasured actors (e.g. species or covariate). This results in spurious edges in the marginal network between the species linked to the latter in the complete network, causing inaccurate further analysis. The second objective of this work is to account for missing actors during network inference. To do so we adopt a variational approach yielding valuable insights about the missing actors
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Harris, Danielle V. "Estimating whale abundance using sparse hydrophone arrays." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3463.
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Passive acoustic monitoring has been used to investigate many aspects of marine mammal ecology, although methods to estimate absolute abundance and density using acoustic data have only been developed in recent years. The instrument configuration in an acoustic survey determines which abundance estimation methods can be used. Sparsely distributed arrays of instruments are useful because wide geographic areas can be covered. However, instrument spacing in sparse arrays is such that the same vocalisation will not be detected on multiple instruments, excluding the use of some abundance estimation methods. The aim of this thesis was to explore cetacean abundance and density estimation using novel sparse array datasets, applying existing methods where possible, or developing new approaches. The wealth of data collected by sparse arrays was demonstrated by analysing a 10-year dataset collected by the U.S. Navy's Sound Surveillance System in the north-east Atlantic. Spatial and temporal patterns of blue (Balaenoptera musculus) and fin whale (Balaenoptera physalus) vocal activity were investigated using generalised additive models. Distance sampling-based methods were applied to fin whale calls recorded by an array of Ocean Bottom Seismometers in the north-east Atlantic. Estimated call density was 993 calls/1000 km².hr⁻¹ (CV: 0.39). Animal density could not be estimated because the call rate was unknown. Further development of the call localisation method is required so the current density estimate may be biased. Furthermore, analysing a single day of data resulted in a high variance estimate. Finally, a new simulation-based method developed to estimate density from single hydrophones was applied to blue whale calls recorded in the northern Indian Ocean. Estimated call density was 3 calls/1000 km².hr⁻¹ (CV: 0.17). Again, density of whales could not be estimated as the vocalisation rate was unknown. Lack of biological knowledge poses the greatest limitation to abundance and density estimation using acoustic data.
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Ross, Beth E. "Assessing Changes in the Abundance of the Continental Population of Scaup Using a Hierarchical Spatio-Temporal Model." DigitalCommons@USU, 2012. http://digitalcommons.usu.edu/etd/1147.
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In ecological studies, the goal is often to describe and gain further insight into ecological processes underlying the data collected during observational studies. Because of the nature of observational data, it can often be difficult to separate the variation in the data from the underlying process or `state dynamics.' In order to better address this issue, it is becoming increasingly common for researchers to use hierarchical models. Hierarchical spatial, temporal, and spatio-temporal models allow for the simultaneous modeling of both first and second order processes, thus accounting for underlying autocorrelation in the system while still providing insight into overall spatial and temporal pattern. In this particular study, I use two species of interest, the lesser and greater scaup (Aythya affnis and Aythya marila), as an example of how hierarchical models can be utilized in wildlife management studies. Scaup are the most abundant and widespread diving duck in North America, and are important game species. Since 1978, the continental population of scaup has declined to levels that are 16% below the 1955-2010 average and 34% below the North American Waterfowl Management Plan goal. The greatest decline in abundance of scaup appears to be occurring in the western boreal forest, where populations may have depressed rates of reproductive success, survival, or both. In order to better understand the causes of the decline, and better understand the biology of scaup in general, a level of high importance has been placed on retrospective analyses that determine the spatial and temporal changes in population abundance. In order to implement Bayesian hierarchical models, I used a method called Integrated Nested Laplace Approximation (INLA) to approximate the posterior marginal distribution of the parameters of interest, rather than the more common Markov Chain Monte Carlo (MCMC) approach. Based on preliminary analysis, the data appeared to be overdispersed, containing a disproportionately high number of zeros along with a high variance relative to the mean. Thus, I considered two potential data models, the negative binomial and the zero-inflated negative binomial. Of these models, the zero-inflated negative binomial had the lowest DIC, thus inference was based on this model. Results from this model indicated that a large proportion of the strata were not decreasing (i.e., the estimated slope of the parameter was not significantly different from zero). However, there were important exceptions with strata in the northwest boreal forest and southern prairie parkland habitats. Several strata in the boreal forest habitat had negative slope estimates, indicating a decrease in breeding pairs, while some of the strata in the prairie parkland habitat had positive slope estimates, indicating an increase in this region. Additionally, from looking at plots of individual strata, it seems that the strata experiencing increases in breeding pairs are experiencing dramatic increases. Overall, my results support previous work indicating a decline in population abundance in the northern boreal forest of Canada, and additionally indicate that the population of scaup has increased rapidly in the prairie pothole region since 1957. Yet, by accounting for spatial and temporal autocorrelation in the data, it appears that declines in abundance are not as widespread as previously reported.
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Hanson, John Mark 1955. "Patterns of animal abundance in lakes : the role of competition in the fish-macroinvertebrate relationship." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=71975.
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Data taken from the literature were used to develop and evaluate models predicting fish biomass and yield, crustacean zooplankton biomass, and profundal macrobenthos biomass in lakes. Total phosphorus concentration and macrobenthos biomass/mean depth were the best univariate predictors of fish biomass and yield. Phosphorus concentration was also the best predictor of zooplankton and macrobenthos biomass. In experiments testing for inter- and intraspecific competition, conducted in situ at densities based on measured natural fish densities, growth of yellow perch (Perca flavescens) and pumpkinseed (Lepomis gibbosus) reared alone was inversely related to density. Both species primarily ate macroinvertebrates when reared alone. When reared together: perch growth was significantly depressed compared to that of perch reared alone; pumpkinseed growth was equivalent to that of pumpkinseed reared alone; and the diet of perch changed to include food of inferior quality (microcrustaceans) in the presence of the superior competitor, pumpkinseed, whose diet did not change.
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DuFour, Mark R. "Quantification of Variability, Abundance, and Mortality of Maumee River Larval Walleye (Sander vitreus) Using Bayesian Hierarchical Models." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1351976817.
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Sampson, Mark Robert. "Modelling the distribution and abundance of several demersal fish species on the Agulhas Bank, South Africa." Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1006207.
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The Agulhas Bank supports a speciose fish community, many of which are commercially important. Despite substantial research being conducted on aspects of their biology spatial aspects of their distribution and abundance in relation to environment parameters has been ignored. This study, therefore, addressed aspects related to the distribution and abundance of representative species on the Agulhas Bank within a Geographic Information System (GIS). Four candidate species were chosen due to their importance either in numbers or unit mass to the South African demersal trawl fishery. The species also shared morphological and taxonomic similarities. The candidate species chosen were the two Cape hake species, shallow-water hake Meluccius capensis, and deep-water hake Merluccius paradoxus, and the two pleuronectiform species being Agulhas sole Austroglossus pectoralis and redspotted tonguesole Cynoglossus zanzibarensis. The use of a GIS was appropriate and allowed for hidden spatial patterns be exposed and illustrated visually, while also facilitating the quantification of the relationships between distribution/abundance and certain environmental predictors using statistical methods The Department of Marine and Coastal Management, Cape Town, supplied biological data in the form of length frequency and biomass information from spring (AprillMay) and autumn (September/October) cruises conducted between 1986 and 1993 on the R. V. Africana. The Council for National Geoscience, Cape Town, supplied sediment data for the entire southern African coastline. Initial exploratory data analysis highlighted potential relationships between environmental variables and abundance for each specie's life-history stanzas. Variations in spatial distribution were found to be significantly different between each life-history stanzas within species. Fish density as a function of the additive effects of the various environmental parameters, including temperature, depth and sediment type, was assessed using a Poisson Generalized Additive Model (GAM), while distribution was analysed with a logistic GAM. A predictive logistic model was then created, taking into consideration the importance of the predictor variables for each species, allowing for predictive estimates to be made for each species by inputting environmental information within the study area. The importance of certain environmental variables influencing distribution and abundance were noted. General patterns indicated that sediment was the most important to both the distribution and abundance of the two pleuronectiform species and juvenile life-history stanzas, while the adult gadoids' distribution and abundance appeared to be depth dependent.
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Mkango, Sara. "Multi-species models of Antarctic krill predators : do competitive effects influence estimates of pre-exploitation whale abundance and recovery?" Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4911.
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Includes bibliographical references (leaves 92-111).Many species of baleen whales and seals in the Southern Hemisphere were subject to intensive overexploitation by commercial harvesting in the last two centuries, and many populations were reduced to very low levels. Krill is the dominant prey item of these species. Harvesting (to near extinction) of the large baleen whales (blue, humpback and fin whales) from the start of the 20th century led to a likely increase in the availability of krill to other krill predators such as the Antarctic minke whales and crabeater seals. This phenomenon is referred to as the “krill surplus” hypothesis and has been a central hypothesis of Antarctic ecosystem studies. This thesis aims to better understand species interactions in the Antarctic through developing and extending multispecies models of the system. The study considered only Region A (IWC Management Areas II, III and IV, 60°W to 130°E) because the numbers of baleen whales harvested in Atlantic/Indian Oceans were far greater than in other Oceans, so that the impacts on the dynamics of these species are likely greater. The simple models of competition between blue and fin whales developed give qualitatively similar results to the Mori-Butterworth Antarctic ecosystem model of an initial number of fin whales before exploitation began that is much lower than single species models suggest. However, there are important features of blue and fin whale CPUE data off Durban over the middle decades of the last century that are not reflected by the model results, and a number of possible reasons for this are advanced. In particular, the introduction of competition in the models predicts a steady fin whale population until 1950, but cannot reproduce the feature in the CPUE data of an increase from the 1920’s to 1950’s. The study then extends the Mori-Butterworth Antarctic ecosystem model by adding squid, which has fast dynamics compared to whales and seals. The model estimates population trends in terms of numbers or biomass. This study indicates that results are particularly sensitive to the density dependence assumed for natural mortality and/or birth rate. The results highlight that the squid biomass trajectory is relatively insensitive to initial squid abundance but depends strongly on the density dependence assumed for squid. Generally, the estimated historical trajectories suggest that the inclusion of squid in the model hardly impacts the maxima reached by other species that benefited from the krill surplus. The model predicts that squid started to increase at about the same time (1920) that the reduction of large baleen whales (blue, humpback and fin whales) commenced under heavy harvesting. This suggests that species with fast dynamics such as squid were possibly the first to benefit from krill surplus, even before minke whales and crabeater seals, which started to increase only about a decade later. The study provides a potential framework for understanding the interplay between species with slow and fast dynamics.
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Clark, Emily. "Quantifying the Relative Abundance of the Relaxin Receptor in Cardiac Tissue from Pre-Menopausal and Post-Menopausal Rat Models." Walsh University Honors Theses / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=walshhonors1587410878183115.
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Gent, John. "Abundance and scarcity : classical theories of money, bank balance sheets and business models, and the British restriction of 1797-1818." Thesis, London School of Economics and Political Science (University of London), 2016. http://etheses.lse.ac.uk/3435/.
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The thesis looks through the lens of bank balance sheet accounting to investigate the structural change in the British banking system between 1780 and 1832, and how classical quantity theorists of money attempted to respond to the ensuing financialisation of the wartime economy with its growing reliance on credit funded with paper-based instruments (the ‘Vansittart system’ of war finance). The thesis combines contributions to three separate fields to construct a holistic historical example of the challenges faced by monetary economists when ‘modelling’ financial innovation, credit growth, ‘fringe’ banking, and agent incentives – at a time of radical experimentation: the suspension of the 80-year-old gold standard (“the Restriction”). First, critical text analysis of the history of economics argues that the 1809-10 debate between Ricardo and Bosanquet at the peak of the credit boom, bifurcated classical theory into two timeless competing policy paradigms advocating the ‘Scarcity’ or ‘Abundance’ of money relative to exchange transactions. The competing hypotheses regarding the role of money and credit are identified and the rest of the thesis examines the archival evidence for each. Second, the core of the thesis contributes to the historical literature on banking in relation to money by reconstructing a taxonomy of bank business models, their relationships with the London inter-bank settlement system, and their responses to the Restriction - drawing on some 17,000 mostly new data points collected from the financial records of London and Country banks. The final section contributes to the economic history of money by constructing aggregated views of total bank liabilities from the firm-level data, scaled to recently available British GDP estimates. These are examined to establish (with hindsight) the relative merits and lacuna of the competing theoretical hypotheses postulated by political economists. It was the period of deleveraging after 1810 that revealed the lacuna of both paradigms.
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Bereng, Mosiuoa Walter. "Understanding environmental factors influencing invasion of Lilium formosanum in Mpumalanga Province and models of its potential distribution in South Africa." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/79711.
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Alien invasive plants are of concern in the world because of their potential to spread into the natural environment. Invasion patterns observed in plant species can be attributed among other things to favourable environmental conditions. Understanding invasion dynamics of alien invasive plants can help in timely intervention initiatives. In Mpumalanga, Lilium formosanum (Liliaceae) appears to be an emerging plant invader and is spreading in the natural environment. The study investigated the invasion extent and predictor variables which could explain abundance patterns of L. formosanum in the invasive range in Mpumalanga province in South Africa and further predict regions of the world that could be climatically suitable. Lilium formosanum was surveyed along 11 major routes leading into the towns of Sabie and Graskop in Mpumalanga from a slow moving vehicle. A total of 241 kilometres was surveyed. Lilium formosanum was found to be invasive from the towns of Sabie and Graskop. Climatically suitable areas were predicted using DIVA-GIS and climate data was obtained from WORLDCLIM database while occurrence records were obtained from the Southern African Plant Invaders Atlas, Australia’s virtual herbarium and the Global Biodiversity Information Facility. In conclusion, distance, altitude and route were found to have an influence on the abundance of L. formosanum in Mpumalanga Province. Climatically suitable areas included the eastern coastal belt, northern provinces and the interior parts of South Africa including major parts of Limpopo and Mpumalanga.Dissertation (MSc)--University of Pretoria, 2014.
Plant Production and Soil Science
MSc
Unrestricted
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Kleisner, Kristin Marie. "A Spatio-Temporal Analysis of Dolphinfish; Coryphaena hippurus, Abundance in the Western Atlantic: Implications for Stock Assessment of a Data-Limited Pelagic Resource." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/137.
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Dolphinfish (Coryphaena hippurus) is a pelagic species that is ecologically and commercially important in the western Atlantic region. This species has been linked to dominant oceanographic features such as sea surface temperature (SST) frontal regions. This work first explored the linkages between the catch rates of dolphinfish and the oceanography (satellite-derived SST, distance to front calculations, bottom depth and hook depth) using Principal Components Analysis (PCA). It was demonstrated that higher catch rates are found in relation to warmer SST and nearer to frontal regions. This environmental information was then included in standardizations of catch-per-unit-effort (CPUE) indices. It was found that including the satellite-derived SST and distance to front increases the confidence in the index. The second part of this work focused on addressing spatial variability in the catch rate data for a subsection of the sampling area: the Gulf of Mexico region. This study used geostatistical techniques to model and predict spatial abundances of two pelagic species with different habitat utilization patterns: dolphinfish (Coryphaena hippurus) and swordfish (Xiphias gladius). We partitioned catch rates into two components, the probability of encounter, and the abundance, given a positive encounter. We obtained separate variograms and kriged predictions for each component and combined them to give a single density estimate with corresponding variance. By using this two stage approach we were able to detect patterns of spatial autocorrelation that had distinct differences between the two species, likely due to differences in vertical habitat utilization. The patchy distribution of many living resources necessitates a two-stage variogram modeling and prediction process where the probability of encounter and the positive observations are modeled and predicted separately. Such a "geostatistical delta-lognormal" approach to modeling spatial autocorrelation has distinct advantages in allowing the probability of encounter and the abundance, given an encounter to possess separate patterns of autocorrelation and in modeling of severely non-normally distributed data that is plagued by zeros.
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Kunz, Simon Michael [Verfasser], and W. de [Akademischer Betreuer] Boer. "Constraints on Transport Models for Galactic Cosmic Rays and their Implications for the Anomalous Positron Abundance / Simon Michael Kunz. Betreuer: W. de Boer." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1064504132/34.
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Young, Alexander L., and Alexander L. Young. "Three Essays on Complex Systems: Self-Sorting in a One-Dimensional Gas, Collective Motion in a Two-Dimensional Ensemble of Disks, and Environment-Driven Seasonality of Mosquito Abundance." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624567.
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Complex systems offer broad, unique research challenges due to their inability to be understood through a classic reductionist perspective, as they exhibit emergent phenomena that arise through the interactions of their components. In this thesis, we briefly review some characteristics of complex systems and the interplay of mathematical and computational methods to study them. We then discuss these approaches, how they are implemented, and how they support one another in three settings. First, we present a study that connects weather data to seasonal population-abundance of mosquitoes, using a microscopic model. Secondly, we consider the collective motions that arise in ensembles of disks interacting through non-elastic collisions and investigate how such behaviors affect macroscopic transport properties. Finally, we consider a 'self-sorting' one-dimensional collection of point-particles. In all of these cases, agent-based models and simulations are used to guide analysis, and in the final example, we explain how the simulations led to new theorems. Articles and molecular dynamics computer codes are provided as appendices.
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Bouziani, Naceur. "Elaboration d'un modèle thermo-chimique de la matière cométaire : contribution à l'étude physico-chimique des milieux poreux hétérogènes." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10190.
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Un des plus importants resultats obtenus lors du dernier passage de la comete p/halley est l'estimation de la densite moyenne du noyau. Cela a conforte les hypotheses emises depuis longtemps sur la nature et la structure interne poreuse des cometes. Ces dernieres sont considerees comme des melanges de glace (h2o, co, co2, hcn, et autres volatiles). Lorsqu'une comete s'approche du soleil, la chaleur qui augmente provoque la production gazeuse des volatiles. C'est au cours de cette course vers le soleil que le fameux phenomene cometaire (coma, gaz et queue de poussiere) s'offre a l'observation. Comment lier les abondances observees a la composition chimique interne du noyau cometaire ? au cours de ce memoire, nous tenterons de repondre a cette question en apportant notre contribution a l'elaboration d'un nouveau modele du materiau cometaire. Nous montrons que notre approche de modelisation ameliore considerablement l'effort consenti jusqu'alors dans ce domaine, par une meilleure prise en compte des differents processus mis en jeu dans ce materiau. De plus, la mise en evidence de l'interface (modelisation/simulations empiriques) permet de tirer partie, d'une maniere optimale, des differentes experiences de laboratoire
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Robin, Geneviève. "Low-rank methods for heterogeneous and multi-source data." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX026/document.
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Dans les applications modernes des statistiques et de l'apprentissage, il est courant que les données récoltées présentent un certain nombre d'imperfections. En particulier, les données sont souvent hétérogènes, c'est-à-dires qu'elles contiennent à la fois des informations quantitatives et qualitatives, incomplètes, lorsque certaines informations sont inaccessibles ou corrompues, et multi-sources, c'est-à-dire qu'elles résultent de l'agrégation de plusieurs jeux de données indépendant. Dans cette thèse, nous développons plusieurs méthodes pour l'analyse de données hétérogènes, incomplètes et multi-source. Nous nous attachons à étudier tous les aspects de ces méthodes, en fournissant des études théoriques précises, ainsi que des implémentations disponibles au public, et des évaluations empiriques. En particulier, nous considérons en détail deux applications issues de l'écologie pour la première et de la médecine pour la secondeIn modern applications of statistics and machine learning, one often encounters many data imperfections. In particular, data are often heterogeneous, i.e. combine quantitative and qualitative information, incomplete, with missing values caused by machine failure or nonresponse phenomenons, and multi-source, when the data result from the compounding of diverse sources. In this dissertation, we develop several methods for the analysis of multi-source, heterogeneous and incomplete data. We provide a complete framework, and study all the aspects of the different methods, with thorough theoretical studies, open source implementations, and empirical evaluations. We study in details two particular applications from ecology and medical sciences
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Sommeria-Klein, Guilhem. "From models to data : understanding biodiversity patterns from environmental DNA data." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30390/document.
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La distribution de l'abondance des espèces en un site, et la similarité de la composition taxonomique d'un site à l'autre, sont deux mesures de la biodiversité ayant servi de longue date de base empirique aux écologues pour tenter d'établir les règles générales gouvernant l'assemblage des communautés d'organismes. Pour ce type de mesures intégratives, le séquençage haut-débit d'ADN prélevé dans l'environnement (" ADN environnemental ") représente une alternative récente et prometteuse aux observations naturalistes traditionnelles. Cette approche présente l'avantage d'être rapide et standardisée, et donne accès à un large éventail de taxons microbiens jusqu'alors indétectables. Toutefois, ces jeux de données de grande taille à la structure complexe sont difficiles à analyser, et le caractère indirect des observations complique leur interprétation. Le premier objectif de cette thèse est d'identifier les modèles statistiques permettant d'exploiter ce nouveau type de données afin de mieux comprendre l'assemblage des communautés. Le deuxième objectif est de tester les approches retenues sur des données de biodiversité du sol en forêt amazonienne, collectées en Guyane française. Deux grands types de processus sont invoqués pour expliquer l'assemblage des communautés d'organismes : les processus "neutres", indépendants de l'espèce considérée, que sont la naissance, la mort et la dispersion des organismes, et les processus liés à la niche écologique occupée par les organismes, c'est-à-dire les interactions avec l'environnement et entre organismes. Démêler l'importance relative de ces deux types de processus dans l'assemblage des communautés est une question fondamentale en écologie ayant de nombreuses implications, notamment pour l'estimation de la biodiversité et la conservation. Le premier chapitre aborde cette question à travers la comparaison d'échantillons d'ADN environnemental prélevés dans le sol de diverses parcelles forestières en Guyane française, via les outils classiques d'analyse statistique en écologie des communautés. Le deuxième chapitre se concentre sur les processus neutres d'assemblages des communautés.[...]Integrative patterns of biodiversity, such as the distribution of taxa abundances and the spatial turnover of taxonomic composition, have been under scrutiny from ecologists for a long time, as they offer insight into the general rules governing the assembly of organisms into ecological communities. Thank to recent progress in high-throughput DNA sequencing, these patterns can now be measured in a fast and standardized fashion through the sequencing of DNA sampled from the environment (e.g. soil or water), instead of relying on tedious fieldwork and rare naturalist expertise. They can also be measured for the whole tree of life, including the vast and previously unexplored diversity of microorganisms. Taking full advantage of this new type of data is challenging however: DNA-based surveys are indirect, and suffer as such from many potential biases; they also produce large and complex datasets compared to classical censuses. The first goal of this thesis is to investigate how statistical tools and models classically used in ecology or coming from other fields can be adapted to DNA-based data so as to better understand the assembly of ecological communities. The second goal is to apply these approaches to soil DNA data from the Amazonian forest, the Earth's most diverse land ecosystem. Two broad types of mechanisms are classically invoked to explain the assembly of ecological communities: 'neutral' processes, i.e. the random birth, death and dispersal of organisms, and 'niche' processes, i.e. the interaction of the organisms with their environment and with each other according to their phenotype. Disentangling the relative importance of these two types of mechanisms in shaping taxonomic composition is a key ecological question, with many implications from estimating global diversity to conservation issues. In the first chapter, this question is addressed across the tree of life by applying the classical analytic tools of community ecology to soil DNA samples collected from various forest plots in French Guiana. The second chapter focuses on the neutral aspect of community assembly.[...]
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Bigaton, Ademir Durrer. "Diversidade de bactérias e arquéias em solos cultivados com cana-de-açúcar: um enfoque biogeográfico." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-10042015-111904/.
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A cana-de-açúcar é atualmente a cultura de maior importância agrícola do Estado de São Paulo e tem papel de destaque entre as principais culturas do Brasil. Dentro de um contexto de maior produtividade unida a sustentabilidade, o papel da comunidade microbiana presente nos solos pode ter fundamental importância, auxiliando no melhor desenvolvimento da planta, suprindo a mesma com nutrientes ou diminuindo a ocorrência de doenças e pragas. Contudo, pouco se sabe sobre a comunidade microbiana existente nos solos cultivados com cana-de-açúcar, sendo que um conhecimento da distribuição espacial desta comunidade pode auxiliar para uma melhor compreensão dos processos aos quais estes microrganismos estão envolvidos. Dessa forma, este trabalho teve como objetivo estudar, em um enfoque biogeográfico, a diversidade de bactérias e arquéias existente em solos de cana-de-açúcar do Estado de São Paulo, focando nos grupos de arquéias e bactérias. Uma análise de 285 amostras de solos, obtidas em 10 regiões produtoras distintas, foi realizada utilizando técnicas independentes de cultivo como: quantificação da abundância total por meio da aplicação de PCR em tempo real (qPCR), análises da estrutura da comunidade por polimorfismo de comprimento de fragmentos de restrição terminal (T-RFLP), e determinação da sua afiliação filogenética por sequenciamento em larga escala de genes ribossomais. Os resultados obtidos demonstraram que o principal modulador destas comunidades foram as características física e química do solo (pH, granulometria, matéria orgânica). Além disso, a comunidade de arquéias demonstrou ser influenciada por práticas de manejo (colheita mecanizada e adição de vinhaça e torta de filtro). Adicionalmente, foi observada uma relação inesperada da estruturação destas comunidades com a distribuição geográfica das amostras analisadas. Os resultados demonstram a complexidade da comunidade de bactérias e arquéias ao longo de um gradiente espacial, sugerindo que estudos posteriores devem considerar uma amostragem mais ampla em distintas regiões. Este trabalho é embasador de estudos futuros que visem desenvolver práticas agrícolas baseadas na exploração da funcionalidade dos microbiomas dos solos.Sugarcane is currently the most important culture of the State of São Paulo and has a prominent role among the crops in Brazil. Into the context of a better productivity with greater sustainability, the role of the microbial community present in the soil could have huge importance, aiding a better plant development, supplying it with nutrients or reducing the occurrence of diseases and pests. However, little is known about the microbial community existing in soils cultivated with sugarcane, where a knowledge of the spatial distribution of this community could be helpful to a better understanding of the processes that these organisms are involved. This project aimed to study in a biogeographic approach, the bacteria and archaea diversity in soils of sugarcane in the São Paulo State, focusing on the groups of archaea and bacteria. Analyses of a total of 285 soil samples, obtained in 10 producing distinct regions was performed using independent cultivation techniques such as quantification of total abundance by applying quantitative PCR (qPCR), analysis of the community structure by terminal restriction of length polymorphism (T-RFLP) and determination of its phylogenetic affiliation by high-throughput sequencing of 16S ribosomal genes. The results showed that the main drivers of these communities were the physical and chemical characteristics of the soil (pH, granulometry and organic matter). In addition, the results have shown that archaea community was influenced by management practices (mechanical harvest, vinasse and filter cake adding). Additionally, an unexpected relationship between the structures of these communities with the geographic distribution of the samples was observed. The results demonstrate the complexity of the community of bacteria and archaea along a spatial gradient, suggesting that future studies should consider a broader sampling of the distinct regions. This work supports upcoming studies that aim at developing agricultural practices exploring the soil microbiomes functionality.
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Monsarrat, Sophie. "Reconstruction de la distribution et de l'abondance historiques des mammifères marins : établir un niveau de référence pour comprendre le passé, renseigner le présent et planifier l'avenir." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS277/document.
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La mise en place d'objectifs de conservation adéquats repose sur la définition d'états de référence appropriés pour la distribution et l'abondance des espèces. Cependant, l'étendue des impacts cumulés de l'homme sur les écosystèmes est aujourd'hui largement sous-estimée. Dans ce projet, je m'intéresse aux opportunités qu'offre l'utilisation de données historiques combinées à différentes méthodes analytiques pour définir ces états de référence ainsi qu'aux défis posés par ce type d'approche. Des données de présence ont été recueillies pour sept espèces de cétacés et trois espèces de pinnipèdes à partir de sources archéologiques, historiques et industrielles, révélant des réductions dans la distribution et l'abondance des espèces depuis la préhistoire à nos jours. Des modèles de distribution d'espèces ont été développés pour cinq espèces de cétacés, combinant des données de chasse baleinière du 19ème siècle à des variables environnementales afin d'estimer la distribution historique des espèces avant qu'elles n'aient été chassées. J'ai obtenu pour la baleine franche de l'Atlantique Nord (Eubalena glacialis) une estimation détaillée de sa distribution et de son abondance avant qu'elle ne soit exploitée, en extrapolant des connaissances sur la distribution et l'abondance d'une espèce congénérique, la baleine franche du Pacifique Nord (E. japonica). Ces résultats suggèrent que la baleine franche de l'Atlantique Nord occupe une portion réduite de sa distribution historique, et que son abondance actuelle ne représente qu'une infime portion (<5%) de son abondance passée. Plus généralement, ces résultats soulignent l'importance de considérer des données historiques pour comprendre le niveau d'impact par l'homme sur les espèces, évaluer leur niveau de déplétion et renseigner leur potentiel de rétablissement dans l'avenirRelevant baselines on the historical distribution and abundance of species are needed to support appropriate conservation targets for depleted species, but the full scale of cumulative human impacts on ecosystems is highly underestimated. In this project, I investigated the challenges and opportunities of combining historical data with analytical methods to improve these historical baselines. Occurrence data from archaeological, historical and industrial sources were reviewed for seven cetacean and three pinniped species, revealing range contractions and population depletions from prehistorical times to today. For five whale species, I used species distribution modelling to combine 19th Century whaling records with environmental data, to estimate pre-whaling distributions. For the highly depleted North Atlantic right whale, (Eubalaena glacialis), I obtained a detailed estimate of pre-whaling distribution and abundance by inferring from the historical distribution and abundance of its congeneric North Pacific right whale (E. japonica). These results suggest that the North Atlantic right whale occupies a small fraction of its historical range and that its current population represents <5% of its historical abundance, with implications for the management, monitoring and conservation targets of this species. More generally, these results emphasize the utility of considering historical data to understand the extent to which species have been impacted by humans, assess their current level of depletion, and inform the options available for their future recovery
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Cahen, Sébastien. "Deux enigmes de l'evolution stellaire : les neutrinos solaires et la supernova 1987a." Paris 7, 1987. http://www.theses.fr/1987PA077271.
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Les modeles solaires standards recents, bases sur les tables d'opacite de los alamos, sont compares. Les resultats, notamment l'abondance solaire solaire d'helium et le flux de neutrinos sont presentes et discutes. Un modele semi-analytique de courbe de lumiere de supernovae a ete developpe suivant le schema d'arnett. Les caracteristiques principales de l'emission lumineuse des supernovae, y compris celle des supernovae de type ib ainsi que celle de la supernova 1987a, sont correctement reproduites a l'aide de ce modele
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Koladjo, Babagnidé François. "Estimation non paramétrique du nombre d'espèces : Application à l'étude de la faune ichtyologique du bassin du fleuve Ouëmé." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112153.
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Ce manuscrit est structuré en deux parties. La première partie composée des chapitres 2à 4 aborde le problème d'estimation du nombre de classes dans une population avec une application en écologie. La deuxième partie, correspondant au chapitre 5,concerne la mise en oeuvre de méthodes statistiques pour analyser des données de pêche. Dans la première partie, nous considérons une population hétérogène subdiviséeen plusieurs classes. À partir d'un échantillon, les effectifs d'individus observés parclasse, encore appelés abondances, sont utilisés pour estimer le nombre total declasses dans la population. Dans la littérature consacrée à l'estimation du nombrede classes, les méthodes basées sur un mélange de distributions de Poisson semblentêtre les plus performantes (voir par exemple les travaux de Chao and Bunge (2002)dans le cadre paramétrique et celui de Wang and Lindsay (2005) dans un cadrenon paramétrique). La mise en oeuvre de ces approches sur des données réellesmet en évidence que la distribution des abondances peut être approchée par unedistribution convexe. Nous proposons une approche non paramétrique pour estimerla distribution des abondances sous contrainte de convexité. Cette contrainte définitun cadre théorique d'estimation d'une densité discrète. Le problème d'estimation dunombre de classes est donc abordé en deux volets. Nous montrons d'une part l'existenceet l'unicité d'un estimateur d'une densité discrète sous la contrainte de convexité.Sous cette contrainte, nous démontrons qu'une densité discrète s'écrit comme un mélange de densités triangulaires. À partir de l'algorithme de réduction du supportproposé par Groeneboom et al. (2008), nous proposons un algorithme exact pourestimer les proportions dans le mélange. D'autre part, la procédure d'estimationd'une densité discrète convexe nous sert de cadre pour l'estimation de la distributiontronquée en zéro des observations d'abondance. L'estimation de la loi tronquée obtenue est ensuite prolongée en zéro pour estimer la probabilité qu'une classe ne soit pasobservée. Ce prolongement en zéro est fait de façon à annuler la proportion dela première composante dans le mélange de densités triangulaires. Nousaboutissons à une estimation du nombre de classes à l'aide d'un modèle binomial ensupposant que chaque classe apparaît dans un échantillon par une épreuve deBernoulli. Nous montrons la convergence en loi de l'estimateur proposé. Sur le plan pratique, une application aux données réelles en écologie est présentée. La méthode est ensuite comparée à d'autres méthodes concurrentes à l'aide de simulations. La seconde partie présente l'analyse des données de pêche collectées dans le fleuveOuémé au Bénin. Nous proposons une démarche statistique permettant de regrouperles espèces selon leur profil temporel d'abondances, d'estimer le stock d'une espèceainsi que leur capturabilité par les engins de pêche artisanaleThis manuscript is structured in two parts. The #rst part composed of Chapters 2to 4 deals with the problem of estimating the number of classes in a population withan application in ecology. The second part, corresponding to Chapter 5, concernsthe application of statistical methods to analyze fisheries data.In the first part, we consider a heterogeneous population split into several classes.From a sample, the numbers of observed individuals per class, also called abun-dances, are used to estimate the total number of classes in the population. In theliterature devoted to the number of classes estimation, methods based on a mix-ture of Poisson distributions seem to be the most effcient (see for example the workof Chao and Bunge (2002) in the parametric framework and that of Wang and Lind-say (2005) in a non-parametric framework). Applications of these approaches to realdata show that the distribution of abundances can be approximated by a convexdistribution. We propose a non-parametric approach to estimate the distribution ofabundances under the constraint of convexity. This constraint defines a theoreticalframework for estimating a discrete density. The problem of estimating the numberof classes is then tackled in two steps.We show on the one hand the existence and uniqueness of an estimator of adiscrete density under the constraint of convexity. Under this constraint, we provethat a discrete density can be written as a mixture of triangular distributions. Usingthe support reduction algorithm proposed by Groeneboom et al. (2008), we proposean exact algorithm to estimate the proportions in the mixture.On the other hand, the estimation procedure of a discrete convex density is usedto estimate the zero-truncated distribution of the observed abundance data. Thezero-truncated distribution estimate is then extended at zero to derive an estimateof the probability that a class is not observed. This extension is made so as tocancel the first component in the mixture of triangular distributions. An estimateof the total number of classes is obtained through a binomial model assuming thateach class appears in a sample by a Bernoulli trial. We show the convergence inlaw of the proposed estimator. On practical view, an application to real ecologicaldata is presented. The method is then compared to other concurrent methods usingsimulations.The second part presents the analysis of fisheries data collected on the Ouémériver in Benin. We propose a statistical approach for grouping species accordingto their temporal abundance profile, to estimate the stock of a species and theircatchability by artisanal fishing gears
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Kada, Sara. "Sources d'hétérogénéité dans la circulation d'agents infectieux transmis par les vecteurs : le cas des tiques et maladies à tiques dans des systèmes d'hôtes structurés spatialement." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT139.
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Tous les hôtes ne contribuent pas également à la transmission de parasites. Certains individus ou espèces peuvent par exemple être davantage infectés que d'autres, une observation qui a mené à la proposition de la règle des `20/80', selon laquelle 20 % des individus seraient responsables de 80 % de la transmission. Cependant, les études qui se sont intéressées à l'hétérogénéité de la transmission se sont principalement focalisées sur les sources d'hétérogénéité intrinsèques à l'espèce ou à l'individu, telles que la susceptibilité ou l’infectivité, tandis que les facteurs extrinsèques, comme la connectivité entre espèces au sein de la communauté d'hôtes et le rôle de différents types de mouvements des hôtes ont été relativement négligés. Dans ce contexte, cette thèse aborde le rôle des causes extrinsèques de l'hétérogénéité de transmission sur la propagation d'infections dans les systèmes multi-hôtes, en utilisant notamment les systèmes tiques-oiseaux marins-microparasites comme support empirique à des approches de modélisation théorique. Quatre principales sources d'hétérogénéité dans les systèmes à transmission vectorielles ont ainsi été considérées : (i) l'hétérogénéité de l'abondance des vecteurs, de leur distribution, et l'estimation des paramètres de la dynamique de leurs populations, (ii) l'hétérogénéité de contact entre espèces de communautés multi-hôtes et multi-vecteurs, (iii) l'hétérogénéité de la propagation d'infections en raison de différents types de comportements des hôtes (avec en particulier, l'importance de considérer les mouvements de prospection entre groupes d'hôtes chez les espèces sociales) et (iv) l'hétérogénéité dans les capacités de dispersion et de transmission d'infections entre vecteurs à traits d'histoire de vie contrastés (dispersion en fonction du stade de vie). Nous soulignons d'abord l'importance potentielle d'une estimation fiable des abondances d'ectoparasites, à l'aide d'approches hiérarchiques susceptibles de prendre en compte à la fois l'hétérogénéité de leur probabilité de détection et leur distribution agrégée. Ensuite, nous utilisons une approche permettant d'étudier l'impact des caractéristiques du réseau d'interactions au sein de la communauté d'hôtes sur la transmission et le maintien d'infections. Nos résultats indiquent que la structure de la communauté mais aussi les propriétés locales des espèces modèlent l'émergence d'espèces qui contribuent disproportionnellement à la transmission de l'infection (`superspreader') et d'espèces qui contribuent disproportionnellement au maintien de l'infection (`keystone') dans les communautés d'infections multi-hôtes, multi-vecteurs. Nous avons également exploré le rôle de la contribution de différents comportement de déplacement des hôtes et des traits d'histoire de vie des vecteurs sur la propagation d'agents infectieux. Une revue de la littérature nous a permis de souligner l'importance potentielle, relativement aux autres comportements de déplacement plus communément considérés, des mouvements de prospection entre groupes d'hôtes sur le rôle dans la transmission d'infections. Les résultats d'un travail théorique nous on également permis de montrer l'importance des caractéristiques des traits d'histoire de vie des vecteurs (notamment la durée de repas sanguins) et des contraintes démographiques (effet Allee) sur le potentiel de colonisation des tiques. Cette différence de dispersion en fonction du stade est ainsi susceptible d'avoir une incidence sur la propagation d'infections à transmission vectorielle et la structure génétique des populations de tiques. Dans l'ensemble, les travaux menés ont permis de mettre en évidence l'importance de l'étudie des déterminants des hétérogénéités de transmission et leurs conséquences dans les systèmes à transmission vectorielles, pour une meilleure compréhension de l’écologie et l’évolution des interactions entre hôtes et parasites, avec des implications potentielles pour le contrôle des maladiesDifferent hosts may not contribute equally to parasite transmission. For instance, some individuals or species may be more heavily infected than others, an observation that lead to the `20/80' rule, stating that in many cases 20% of individuals are responsible for 80% of the transmission. However, studies on heterogeneity in transmission have primarily focused on intrinsic factors of transmission, such as susceptibility and infectivity, while the impact of extrinsic factors, such as connectivity network among individuals or species of the host community and the role of various host movements has been relatively neglected. This thesis investigates the role of extrinsic transmission heterogeneities on the spread of infectious disease in multi-host systems, using tick-seabird-microparasite system as empirical models for theoretical investigations. Four main causes of heterogeneity in transmission of vector-borne diseases were considered : (i) heterogeneity in vector abundance, distribution, and estimation thereof (ii) heterogeneity in contact among species in a multi-host, multi-vector community, (iii) heterogeneity in infection spread caused by different host mouvement behaviors (notably the potential role of ‘prospecting’ by host individual among host groups), and (iv) heterogeneity in dispersal ability and transmission competence among vectors with different life-history traits (stage-dependent dispersal). First, we highlight the need to accurately estimate ectoparasite abundances with hierarchical modeling approaches that can take into account both heterogeneity in their detection probability and their aggregated distribution among hosts. Next, using network theory to examine the impact of community context on disease transmission and maintenance, we found that network structure (modularity, nestedness) and node-based measures (e.g., centrality) both shape the emergence of ‘super-spreader’ species (i.e., species that contribute disproportionally to disease transmission) and keystone species (i.e., species that contribute disproportionally to disease maintenance) in multi-host, multi-vector pathogens communities. Finally, we explored the contribution of host behavior and vector life-history traits to the spread of infectious agents. By reviewing the recent literature, we highlight the fact that prospecting, relative to various other types of host movement, may be of key importance to disease transmission among host groups, notably in social species. We also show how vector life history characteristics (e.g. length of bloodmeals) and demographic constraints (Allee effects) affect their colonization potential. Soft ticks, which take a single, long bloodmeal at only the larval stage, should have much lower colonization rates than hard ticks, which take a single, long bloodmeal at every life stage. These stage-dependent dispersal discrepancies may have direct consequences for the genetic structure of their populations and the spread of vector-borne infectious agents. Overall, these findings highlight the importance of studying the causes and consequences of transmission heterogeneity in multi-host, multi-vector systems. A series of potentially important sources of heterogeneity in parasite transmission are outlined, together with perspectives of empirical and theoretical studies to further explore their implications for understanding ecology and evolution of host-parasite interactions and for disease management purposes
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Nishioka, Shuichiro. "Technology, productivity and knowledge in the factor abundance model." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273684.
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Mortara, Sara Ribeiro. "Abundância de samambaias em metacomunidades: relacionando padrões e processos com modelos estatísticos." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/41/41134/tde-17082016-141523/.
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Entender como comunidades são estruturadas a partir de um pool de espécies é uma questão central em Ecologia de Comunidades. Diversas abordagens foram propostas para estabelecer a ligação entre os padrões de estrutura de comunidades e os processos que os geram. As regras de assembleia e a abordagem filogenética em ecologia de comunidades são alguns exemplos. Entretanto, o que estas abordagens não levam em conta é o efeito de processos neutros na estruturação de comunidades. Há um consenso de que tanto nicho como neutralidade afetam a estrutura de comunidades e que se deve avaliar a importância relativa de cada um destes processos. A ideia desta tese foi usar modelos estatísticos para representar como processos neutros e de nicho geram padrões em comunidades. No Capítulo 2 propus uma abordagem baseada em modelos hierárquicos através da qual é possível expressar processos neutros e de nicho. A partir disso, foi possível representar hipóteses em que apenas processos neutros afetam a estrutura da comunidade, apenas processos de nicho ou diferentes combinações entre ambos. Usando seleção de modelos, identifiquei qual a combinação de processos melhor explica as abundâncias observadas das espécies. Com isso, mostrei que as comunidades de samambaias em gradientes altitudinais na Serra do Mar no Paraná, Brasil são estruturadas por uma mistura de filtro ambiental, deriva ecológica e limitação de dispersão. O filtro ambiental define as abundâncias das espécies selecionando as melhores estratégias ecológicas das espécies dependendo da altitude. A variação de abundância entre as espécies que compartilham as mesmas estratégias ecológicas é explicada em parte por deriva ecológica e limitação de dispersão e, em parte, por filtro de habitat independente dos atributos das espécies incorporados no modelo. Com isso, delimitei como processos baseados em nicho e neutralidade afetam a abundância das espécies de samambaias ao longo de gradientes altitudinais. No Capítulo 3 usei um estudo de caso para explorar a ideia central da abordagem filogenética em ecologia de comunidades de que é possível inferir os processos que afetam as comunidades com base em padrões locais de estrutura filogenética. Usei a abordagem de modelos proposta no Capítulo 2 para simular comunidades geradas por processos puramente neutros, puramente de nicho e uma combinação hierárquica entre os dois. Encontrei que comunidades geradas apenas por processos de nicho geram estruturas filogenéticas aleatórias na maioria dos casos. A detecção de estruturas filogenéticas aleatórias foi ainda mais frequente nas comunidades geradas por processos puramente neutros e pela combinação de processos neutros e de nicho, não sendo possível a distinção entre estes dois cenários. Desse modo, o estudo de caso mostrou que estruturas filogenéticas não aleatórias são muito pouco plausíveis e que os processos neutros geram uma forte assinatura nos padrões de estrutura filogenética. Com a abordagem proposta nesta tese foi possível delimitar a influência de processos de nicho e neutralidade em comunidades e entender suas consequências em termos dos padrões por eles gerados. A tradução dos diferentes processos em modelos mistos mostrou-se uma ferramenta poderosa para quantificar padrões e construir explicações de como os processos operam juntosUnderstanding how communities are assembled from a species pool is a central question in community ecology. Different approaches to link pattern and processes in community ecology were proposed. Some examples are assembly rules and the community phylogenetic approach. However, one aspect not accounted in those approaches is how neutral processes affect community patterns. There is a consensus that both niche and neutral processes affect community assembly and that the goal should be assess the relative importance of each process. The general idea if this thesis was to use statistical models to represent how niche and neutral generate community patterns. In Chapter 3, I proposed a framework based on hierarchical models to express niche and neutral processes. I used this approach to represent hypothesis in which only niche processes affect community structure, only neutral processes or a hierarchical combination of both explains species abundance. By using model selection, I identifyied which combination of processes better predicts observed abundances on local communities. I showed that fern communities across altitudinal gradients at Serra do Mar in Paraná, Brazil are structured by a mixture of environmental filtering, ecological drift and limited dispersal. Environmental filtering defines species abundance, selecting the best ecological strategies of species depending on altitude. Variation on species abundance sharing the same ecological strategies is explained in part by drift and limited dispersal, and in part by habitat filtering independent of species traits considered in the models. Hence, I refined how niche and neutral processes affect fern abundance on altitudinal gradients. In Chapter 3, I used a case study to explore the idea from community phylogenetics of inferring processes affecting communities based on patterns of phylogenetic structure. I used the modeling framework from Chapter 3 to simulate communities built by niche, neutral and combination of both processes. I found that communities based on niche processes are likely to generate a random phylogenetic structure. The detection of random phylogenetic strucure was even more common on communities built solely by neutral processes and combination of both niche and neutral processes. Therefore, the case study showed that a non random phylogenetic strucure is unlikely and that neutral processes strongly affect the outcome of phylogenetic patterns. Based on the framework proposed on this thesis it is possible to delimit the influence of niche and neutral processes on community assembly and to understand what are the consequences in terms of community patterns. Translating different processes into mixed models can be a powerful tool to quantify patterns and built explanations on how the processes operate together
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Whiting, Michael Lawrence. "Soil moisture model to improve mineral abundance estimates from hyperspectral data /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Pereira, Caroline. "A multiwavelength abundance analysis of sdB stars using new model atmospheres." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557885.
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SdB stars provide a number of challenges in stellar astronomy. Their evolution along the extreme horizontal branch is well-known, but their formation remains a uncertain. Moreover, sdB stars show peculiar photospheric abundances due to diffusion processes and non-radial oscillation have been detected in approximately 10% of sdB stars. Thus, improved knowledge of fundamental parameters of sdB stars through high-quality observations and improved modelling, will allow us to gain a better understanding of these stars, and eventually help address these issues. We have carried out a detailed abundance analysis on a sample of sdB stars, using high quality multiwavelength spectroscopic data from optical telescopes and the HST/STIS and FUSE satellites. The multiwavelength approach allows us verify the consistency of our derived atmospheric parameters, and also allows us to probe elemental abundances of species not readily accessible in the optical region. In addition, we have also used the latest generation of LTE models which implement full metalline blanketing, opacity sampling and updated opacity values from the Opacity Project and IRON Project. Our model grids included OS_m1O models, where abundances were scaled to one-tenth of solar values (as is normally used in sdB studies), and OS_sdB models, where Z < 20 are underabundant by a factor of ten, and Z ~ 20 are overahundant by a factor of ten with respect to solar values. Finally, we have compared our results over the three wavelength regions, to verify the consistency, and we have tri'ed to find any correlations between abundances and sdB properties such as pulsation and evolution.
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Sakr, Ziad. "Cosmology beyond ΛCDM model in the light of cluster abundance tension." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30346.
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Le modèle ΛCDM permet de décrire avec une grande précision la plupart des présentes observations cosmologiques. Cependant, l'un de ses paramètres, σ 8, mesurant l'amplitude de fluctuations de la matière, présente une discordance entre sa valeur contrainte par le spectre de puissance angulaire du CMB de la mission Planck, les Cls, et celle déterminée à partir des amas SZ dans l'univers proche. Dans le présent travail on explore divers extensions du modèle ΛCDM comme origines possibles de cette anomalie. Pour tester les effets de ces extensions, nous avons effectué une analyse Monte Carlo on l'on compare les contraintes sur σ 8 à partir de ΛCDM avec celles résultantes de ces extensions, et ceci en utilisant principalement le spectre de puissance CMB seul ou combiné avec des comptages d'amas. Ces derniers sont basés sur différentes relations masse observables et couvrent différents redshift : des amas de rayons X dans l'univers local, des amas de la mission SZ Planck dans l'univers proche ou une estimation des amas détectés par leur richesse photométrique à partir du la future mission Euclid. Du fait qu'une mauvaise détermination de l'étalonnage de la masse des amas pourrait également être la raison de cette divergence, notre approche consistait, lorsqu'on combinait les deux sondes issues des amas et du CMB, à laisser le facteur d'étalonnage libre afin qu'il soit contraint comme les autres paramètres cosmologiques par les deux données. Dans le cas d'introduction de trois neutrinos massifs dégénérés, nous avons trouvé qu'ils n'ont aucun effet significatif sur la correction de l'écart entre les contraintes issues de comptage CMB et ceux issues des Xray ou SZ cluster. Nous avons ensuite permis à l'indice de croissance ƴ de varier. Nous trouvons une corrélation entre ƴ et le paramètre de calibration masse-observable des amas détectés par rayons X qui n'est pas affecté par la présence ou non des neutrinos massifs. [...]The ΛCDM model has proved successful in describing to a high precision most of nowadays cosmological observations. However, one of its parameters, σ 8, measuring the present matter amplitude fluctuations, constrained from CMB angular power spectrum, the Cls, was found by the Planck mission, in significant tension with value constrained by SZ galaxy cluster counts in the near universe. In the present work we investigate extensions to ΛCDM model as possible origins behind this discrepancy. To test these extensions, we performed a Monte Carlo analysis to compare constraints on σ 8 in ΛCDM with constraints under these extensions, using mainly CMB Cls combined with cluster counts sample. The later were based on different mass observables relations and covered different redshift ranges: X-ray cluster in the local universe, SZ Planck mission clusters from the near universe or photometric richness estimated detected clusters from future high redshift upcoming Euclid alike mission. Because an improper determination of the calibration of cluster mass function could also be behind this discrepancy, our approach was, when combined with CMB, to leave the calibration factor free to vary and be constrained by data. Introducing three degenerate massive neutrinos, we found that they have no significant effect on fixing the discrepancy between CMB and Xray or SZ cluster counts. We then allowed the growth index ƴ to vary. We find a correlation in the confidence space between ƴ and the X-ray mass observable factor not affected by the presence of massive neutrinos, indicating that a modifying gravity is favored over massive neutrinos as a way to alleviate the tension. However, when a SZ cluster sample covering a larger redshift range was used, we found that the correlation between ƴ and the calibration factor, is constrained by the evolution of the growth through redshift and limited to a region where it cannot fix the discrepancy. [...]
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Pereira, Tiago Mendes Domingos, and tiago@mso anu edu au. "Confronting the new generation of stellar model atmospheres with observations." The Australian National University. Research School of Astronomy and Astrophysics, 2009. http://thesis.anu.edu.au./public/adt-ANU20100701.165106.
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Stellar model atmospheres are a fundamental tool for our understanding of stars. Because the chemical composition of stars cannot be measured directly, the inferred stellar parameters are model dependent. In recent years great progress has been made in the modeling of stellar atmospheres, allowing the relaxation of simplifying assumptions made in previous models. The use of new 3D model atmospheres to infer the solar chemical composition has resulted in a decrease of the solar metallicity. This result has caused some controversy and is being challenged.
The main aim of this thesis is to ascertain if the new models of stellar atmospheres are realistic and can be trusted to derive the chemical composition of stars in general, and the Sun in particular. Other objectives also include the study of line formation in the Sun at high spatial resolution, and possible implications in the modeling.
The Sun is the ideal test-bench for detailed analyses of stellar atmospheres. With the solar surface being resolved in great detail and at different viewing angles, a wealth of information can be gathered that allows for very robust tests of atmosphere models. The testing detailed here addresses several fronts. On one hand, the model�s temperature structure is directly tested with the classical tests of continuum centre-to-limb variations and absolute fluxes. On the other hand, the line formation is tested at different viewing angles and high spatial and spectral resolution. Here the main focus is on oxygen lines, as oxygen has an important contribution for the total solar metallicity. However, other lines are also tested. High quality data were specifically obtained for these line formation tests, using the Swedish 1-m Solar Telescope.
For the temperature structure tests we find a surprisingly good agreement between the 3D model and the observations, surpassing even semi-empirical models. The solar 1D non-LTE models have a very similar behaviour to 1D LTE models, confirming that LTE is a good approximation in the solar photosphere. The 3D theoretical model performs consistently better than its 1D counterparts. The oxygen line formation tests are carried out in great detail, with a careful wavelength calibration, revised atomic data, and allowing for departures from LTE. Again we find a reassuring agreement between the 3D model predictions and the observations, both for the centre-to-limb variation of the lines and the line formation at high spatial resolution. The observations at different viewing angles also allowed the empirical determination of the role of hydrogen collisions with oxygen, important when deriving the oxygen abundance.
The tests undertaken here show that the 3D model atmospheres are indeed very realistic. Their predicted temperature structure and velocity fields compare very favourably with observations of the Sun. Together with previous tests, this indicates they can be relied upon to derive the chemical composition of the Sun and similar late-type stars.
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Campbell, S. W., T. N. Constantino, V. D'Orazi, C. Meakin, D. Stello, J. Christensen-Dalsgaard, C. Kuehn, et al. "Towards 21st century stellar models: Star clusters, supercomputing and asteroseismology." WILEY-V C H VERLAG GMBH, 2016. http://hdl.handle.net/10150/621500.
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Stellar models provide a vital basis for many aspects of astronomy and astrophysics. Recent advances in observational astronomy - through asteroseismology, precision photometry, high-resolution spectroscopy, and large-scale surveys - are placing stellar models under greater quantitative scrutiny than ever. The model limitations are being exposed and the next generation of stellar models is needed as soon as possible. The current uncertainties in the models propagate to the later phases of stellar evolution, hindering our understanding of stellar populations and chemical evolution. Here we give a brief overview of the evolution, importance, and substantial uncertainties of core helium burning stars in particular and then briefly discuss a range of methods, both theoretical and observational, that we are using to advance the modelling. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Jorge, Marcelo Haidar. "Assessing the Influence of Prescribed Fire on Faunal Communities in a Pyric Landscape." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/104395.
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Understanding the link between environmental factors such as disturbance events, land cover, and soil productivity to spatial variation in animal distributions and vital rates is fundamental to population ecology and wildlife management. The Longleaf pine (Pinus palustris; hereafter, LLP) ecosystem is an archetypal fire-mediated ecosystem, which has seen drastic reductions in land area due to fire suppression. Current restoration utilizes prescribed fire and hardwood removal, but more research is needed to understand the influence of these restoration efforts on the wildlife that exist in that ecosystem. As such, we conducted field surveys on Camp Blanding Joint Training Center and Wildlife Management Area to understand how fire influences relative abundances of mammalian predators, occupancy and species richness of avian species, guilds and communities, and vital rates of white-tailed deer (Odocoileus viginianus) fawns.
Our results indicated that mammalian predator space use, and avian species richness were influenced by fire and land cover. Mammalian predator space use was altered by fire conditions and land cover. This mechanism may support predator management strategies that utilizes commonly management techniques for the restoration and conservation of the LLP ecosystem to indirectly alter predator distributions, which has the potential to positively affect the management of important species within this ecosystem. Some mammalian mesocarnivores historically common throughout the southeastern United States were rarely detected, suggesting more research is needed to identify the cause of the potential decline in mesocarnivores in the Southeastern United States.
Avian species richness at the community level was positively influenced by the heterogeneity of post fire conditions, or pyrodiversity. Avian species richness of the cavity nesting guild was negatively influenced by increasing time-since-fire. Our results suggest that managers can promote avian community diversity by reducing the size of burn units to create areas with multiple adjacent burn units, with unique fire histories and a mosaic of post-fire conditions.
Lastly, fawn recruitment was greater on the higher productivity site than the low productivity site on CB. However, within sites soil productivity did not have a demonstrable effect. In fact, we observed differences between sites, but did not observe any effects of covariates on spatial variation in density or survival of fawns within sites. Although we did not explicitly test the factors influencing our parameters between sites, we hypothesize that the variation in coyote activity rates as well as soil productivity and its subsequent effects (i.e. forage availability, concealment cover, and land cover type) likely drove the differences we saw between sites. These results are relevant to local managers and provide support for unit-specific, deer management on CB.
In conclusion, understanding the influence of fire in a frequently burned landscape allows us to better inform management of predators and avian communities using prescribed burns, and the differences in deer populations between areas allowed us to better in inform managers on harvest quotas so that the magnitude of the effect of harvest can better match the population vital rates of each area.Master of Science
Understanding the link between environmental factors such as fire, land cover and soil productivity is essential for wildlife managers to maintain healthy wildlife populations. The Longleaf pine (Pinus palustris) ecosystem requires frequent fire and has seen drastic reductions in land area due to fire suppression. Current restoration utilizes prescribed fire, controlled burning of an area, and hardwood removal, logging hardwood trees such as oaks, but more research is needed to understand how this restoration influences the wildlife in the longleaf pine ecosystem. As such, we collected data collected from Camp Blanding Joint Training Center and Wildlife Management Area to understand how fire influences the relative numbers of mammalian predators, the distribution and species richness (i.e. number of unique species) of avian species, guilds and communities, and vital rates (i.e. births, survival to a certain age) of white-tailed deer fawns. Our results indicated that mammalian predator distributions, and avian species richness were influenced by fire and land cover. Mammalian predator space use was altered by fire conditions and landcover, which supports a predator management strategy that utilizes prescribed burning and hardwood removal used in restoration and conservation of the LLP ecosystem to indirectly alter predator distributions. Some mammalian mesocarnivores (i.e. foxes, skunks, weasels, etc.) historically common throughout the southeastern United States were rarely detected, suggesting more research is needed to identify the cause of the potential decline of cryptic mesocarnivores in the Southeastern United States. Avian species richness, number of unique species, at the community level was positively influenced by pyrodiversity, the number of unique burn years in an area. This supports and further extends the 'pyrodiversity begets biodiversity' hypothesis for avian species, which states that greater pyrodiversity increases the diversity of bird species in that area. Avian species richness of cavity nesting birds decreased with increasing time since fire. Our results suggest that managers can promote avian community diversity by reducing the size of burn units to create areas with multiple adjacent burn units, with unique fire histories and a mosaic of post-fire conditions. Lastly, fawn recruitment was greater on the higher productivity site than the low productivity site, however, within sites soil productivity did not seem to influence birth and recruitment. Although we did not statistically test the factors influencing our parameters between sites, we hypothesize that the variation in coyote activity rates as well as soil productivity and its subsequent effects (i.e. forage availability, concealment cover, and land cover type) likely drove the differences we saw between sites. These results are relevant to local managers and provide support for managing deer differently across both sites. In conclusion, understanding the influence of fire in a frequently burned landscape allows us to better inform management of predators and avian communities using prescribed burns, and the differences in deer populations between areas allowed us to better in inform managers on harvest quotas so that the magnitude of the effect of harvest can better match the population vital rates of each area.
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Dussán-Duque, Beatriz Salomé. "Ecology of the Guiana dolphin (Sotalia guianensis) in the Southern area of the Gulf of Morrosquillo, Colombia : implications for conservation." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4153.
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Sotalia guianensis is listed as “Data Deficient” by the IUCN and as “Vulnerable” in Colombia. This study aimed to advance understanding of the ecology of this species and its habitats, and to provide information to conservation management in the southern Gulf of Morrosquillo, Colombia. Systematic boat-based surveys were conducted during 395 days in 2002-2006 and 2009-2010, following established routes. Total survey effort was 15,199 km in an area covering ~ 310km². Fine scale habitat use and behavioural modelling, photo-identification and mark-recapture techniques were used to analyze the ecological patterns for this species. The most recent abundance estimate of dolphins using the study area during dry and rainy seasons, varied from 225 (CV = 0.34; 95% CI: 118-426) to 232 (CV = 0.32; 95% CI: 127-246). Annual survival rate is estimated at 0.948 (95% CI = 0.876-0.980). Overall density was 0.74/km². Dolphins were present year-round in the whole study area. Results indicate that they do not use the study area uniformly and that the use of particular zones is related to eco-geographic variables. Dolphins showed a preference for waters greater than 3m in depth with a slightly increased preference for waters about 5m and 15-25m deep. The average group size was nine individuals. Some individuals show long-term high site fidelity to some zones within the study site boundaries. Even though the site fidelity to feeding areas varied individually, all the individuals focused primarily on one specific area. Foraging was among one of the most predominant behaviours observed. The individual movements show that some dolphins use both bay and gulf waters. Dolphins show a range of surface cooperative foraging and feeding strategies. These cooperative behaviours were influenced by zone, group size and prey type. Based on these results an area of special management for the species will be created in Colombia.
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Wessling, William T. "Institutional quality, economic development, and natural resource abundance| Towards and interactive model of development." Thesis, Webster University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1525314.
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The study of institutions (i.e., "the rules of the game" in a society) has grown from a small fringe subject in the late 1980s to a massive pillar in the current study of International Political Economy. Two thing has become clear during the course of this growth and the involved research it entails: (1) institutional Quality (especially quality of governance and rule of law) has a determinant effect on the GDP development of a given countries economy and (2) institutional quality has a determinant effect on whether a country is either "cursed" or "blessed" with natural resource abundance (i.e., whether they are growth "winners" or "losers" in terms of GDP development. The purpose of this study is to determine whether the presence of abundant natural resources amplifies this determinant effect when controlled for nonresource abundant states, and if so to what extent. The study ultimately finds amplification of the effect of institutional quality on GDP per capita when controlling for natural resource abundance, ultimately suggesting that resource abundance can be either a "blessing" or a "curse" depending on preexisting institutional quality. Secondary findings indicate the existence of a "slippage" effect in institutional quality once natural resources are introduced to a given state's economy.
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Zahid, Saman. "Comparing Resource Abundance And Intake At The Reda And Wisla River Estuaries." Thesis, Linköpings universitet, Statistik och maskininlärning, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-172770.
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The migratory birds stop at different stopover sites during migration. The presence of resources in these stopover sites is essential to regain the energy of these birds. This thesis aims to compare the resource abundance and intake at the two stopover sites: Reda and Wisla river estuaries. How a bird's mass changes during its stay at an estuary is considered as a proxy for the resource abundance of a site. The comparison is made on different subsets, including those which has incomplete data, i.e. next day is not exactly one day after the previous capture. Multiple linear regression, Generalized additive model and Linear mixed effect model are used for analysis. Expectation maximization and an iterative predictive process are implemented to deal with incomplete data. We found that Reda has higher resource abundance and intake as compared to that of Wisla river estuary.
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Watson, L. Scott. "Solar models including revised abundances and dark matter : constraints from helioseismology and neutrino observations." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491613.
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This thesis presents several topics in both standard and non-standard solar models using the Iben Stellar Evolution Code. First, a set of standard solar models are developed using the abundance determination of Grevesse & Noels (1993) and the more recent determination of Asplund et al. (2005a,b). This recent solar photospheric abundance analysis reduces the abundances of heavy elements, most notably C, N, 0, Ne and Ar, by 0.15 to 0.20 dex, lowering the solar Z/X to 0.0165, compared to the previous Grevesse & Noels value of Z/X = 0.0245. A comparison study between these models show evolutions based on newer determinations with reduced heavy-element abundances break the previously excellent agreement between the standard solar model and the helioseismic inferences of sound speed profile, convection zone base radius and surface Y abundance. Multiple approaches taken to reconcile the new abundances with helioseismology are discussed, and models with selective enhancements to diffusion given special attention. The results of all attempts provide an incomplete and unsatisfactory solution. Evolution, helioseismic and g-mode calculations were done in a separate study of nonstandard solar models for spin-dependent interactions with 5 - 20 GeV mass WIMPs in a parameter space loosely constrained by detection experiments. Results for models with 10-40 ::; (O''annV) ::; 10-27 cm3 s-l show that solar modelling can only constrain parameters for \VIMP background densities Px > 103 GeV cm-3 if their annihilation is dominated by scalar interactions; the case for neutralinos. For dark matter annihilating through vector interactions, such as scalar dark matter, the solar model can be used to place constraints on WHviP parameters at a background density of Px ,...., 0.3 GeVcm-3, which is predicted for the Sun.
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Vasilyev, Valeriy [Verfasser], and Norbert [Akademischer Betreuer] Christlieb. "Dynamical model atmospheres for the abundance analysis of pulsating stars / Valeriy Vasilyev ; Betreuer: Norbert Christlieb." Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/117769171X/34.
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Rethwisch, Michael D., Charles McDaniel, and Manuel Peralia. "Seasonal Abundance and Field Testing of a Citrus Thrips Temperature Development Model in Arizona Citrus." College of Agriculture, University of Arizona (Tucson, AZ), 1998. http://hdl.handle.net/10150/220568.
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Citrus thrips populations (adults and nymphs) were monitored through the spring of 1991-1992 in several locations throughout most of the commercial citrus production areas in Yuma County to determine if citrus thrips seasonality was similar to that previously reported in California. Study findings indicate that seasonality is similar throughout the winter and very early spring. Adult thrips numbers increase rapidly in groves due to attractive foliage, whether it is weeds or citrus. High nymph numbers did not always follow adult peaks, and were not statistically correlated. Predatory mites and rains may have affected 1992 results.
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Condé, Paula Alves. "Modelos teóricos de distribuição de abundância das espécies para caracterização da diversidade biológica e a utilização de diferentes medidas de abundância." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/41/41134/tde-17122012-145930/.
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As distribuições de abundância das espécies (SADs) são consideradas uma maneira informativa e sintética de descrever a diversidade biológica, e revelam um dos padrões mais bem estabelecidos da ecologia, que é a predominância de espécies raras nas comunidades biológicas. A generalidade deste padrão o torna relevante para a análise de outros parâmetros das comunidades. Além disso, ele levou ao desenvolvimento dos modelos teóricos de SAD. Os modelos estatísticos de SAD, por sua vez, passaram a ocupar um papel central na biologia, como principio empírico que sustenta várias teorias ecológicas. Preston sugeriu em 1948 que as SADs das comunidades naturais teriam uma distribuição aproximadamente Lognormal, porém apareciam truncadas devido ao efeito do tamanho amostral, cuja forma real só seria revelada, portanto, em amostras grandes. Esta ideia vai de encontro à propriedade estatística da consistência, que implica que o acúmulo de evidência causado pelo aumento do tamanho amostral favorece a aproximação ao modelo verdadeiro, bem como às estimativas de seus parâmetros. Além do efeito do tamanho amostral, os padrões de distribuição de abundância podem diferir dependendo da medida de abundância utilizada. Estudos sugerem que a biomassa seria uma medida de abundância mais adequada para revelar a distribuição subjacente de uma comunidade biológica em amostras ou escalas menores (differential veiling). Neste contexto, nosso objetivo principal neste trabalho foi investigar e discutir a vantagem de considerarmos a biomassa como medida de abundância nos modelos teóricos de distribuição de abundância das espécies. Avaliamos, então, o efeito do tamanho da amostra sobre a qualidade dos ajustes dos modelos sob duas diferentes medidas de abundância: biomassa e número de indivíduos. Simulamos amostras de diferentes tamanhos a partir de amostragens aleatórias de uma base de dados empírica e as ajustamos a diferentes modelos de SADs . Com isso, pudemos avaliar a eficiência das amostras - com cada medida de abundância - em revelar o modelo correto, bem como a acurácia e precisão das estimativas dos parâmetros desses modelos. Para o presente estudo, utilizamos um grupo com reconhecido potencial indicador e relevância para estudos ecológicos, os besouros Scarabaeinae. Os resultados encontrados neste estudo mostram que a maior eficiência da biomassa para revelar a distribuição subjacente não é tão geral quanto sugerem os trabalhos anteriores Os critérios de análise utilizados não favoreceram consistentemente a biomassa como medida mais eficiente em revelar o modelo correto e apresentar maior acurácia e precisão nas estimativas de seus parâmetros. Assim, a afirmativa de que a SAD de biomassa não é oculta (veiled) em escalas e amostra menores não parece ser geral. Os resultados obtidos no presente estudo também indicam que o padrão de differential veiling entre as SADs de biomassa e número de indivíduos podem variar dependendo da escolha do modelo e do conjunto de dados avaliados. No entanto, se a causa do differential veiling entre as SADs de biomassa e número de indivíduos for principalmente devido ao efeito de escala, uma explicação alternativa é que a escala do presente estudo teria que ser ampliada para podermos demonstrá-lo. Considerando então, os efeitos de amostragem apontados pelos nossos resultados sobre a medida de diversidade, destacamos que, apesar da importância do assunto, há uma escassez de estudos que investiguem o uso da biomassa como medida de abundância nas SADs, cujas implicações de diferentes efeitos sobre esta medida destacam a necessidade de estudos adicionais que possibilitem isolar o efeito de escala do efeito de tamanho amostralThe species abundance distributions (SADs) are considered an informative way to describe the biological diversity revealling one of the most wellestablished patterns in ecology: the predominance of rare species in biological communities. The generality of such pattern made it relevant to the analysis of other biodiversity parameters an to induce the development of theoretical models of SAD. On the other hand statistical models of SAD occupied a central role in biology as an empirical principle that underlies many ecological theories. Preston suggested in 1948 that SADs follow an approximately lognormal distribution, but that may appear truncated by the effect of sample size, being completely revealed only in large samples. This idea is associated with the statistical property of consistency, which implies that the accumulation of evidence - represented by the increase in sample size - approaches the samples distribution to the true model, as well as the estimates of the parameters to their real values. Beyond the effect of sample size, the SADs may differ depending on the measure of abundance adopted. Studies suggest that biomass could be a more efficient measure of abundance to reveal the underlying distribution of biological communities in smaller samples or scales (differential veiling). In this context, our aim in this study was to investigate and discuss the advantage of considering biomass in theoretical models of SAD. Thus we evaluated the effect of sample size on the quality of models fitness under two different measures of species abundance: biomass and number of individuals. We simulated samples of different sizes taken from an empirical database of Scarabaeinae beetles - recognized as a potential and relevant indicator in ecological studies. Further we adjusted the simulated samples to different SAD models and evaluated the efficiency of each kind of abundance index to reveal the correct model, as well as the accuracy and precision of the parameters estimates. Our results show that the efficiency of biomass to reveal the underlying distribution is not as general as suggested by previous works. According to our analysis criteria, biomass was not consistently as far more efficient in revealing the correct model or in providing greater accuracy and precision in parameters estimates than the number of individuals. Thus, the statement that the SAD biomass is not veiled on small scales or samples does not seem to be general. Moreover our results also indicate that the effect of differential veiling on SADs using biomass and number of individuals depends on the choice of the evaluated model and data set. However, if the cause of the differential veiling - between the biomass and number of individuals SADs - is mainly due to scale effects. An alternative explanation is that the scale of this study was not wide enough to show it. Considering the sampling effects studied here in biodiversity evaluation we highlight the lack of studies investigating the use of biomass as a measure of abundance in SADs which the implications of different effects on this measure indicate the urgent call by further studies on this subject, enablying us to isolate the effect of scale from the sample size
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anderson, kaylee. "Using Linear Mixed Models to Analyze Native and Non-Native Species Abundances in Coastal Sage Scrub." Scholarship @ Claremont, 2016. http://scholarship.claremont.edu/scripps_theses/807.
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Coastal Sage Scrub (CSS) is a low scrubland plant community native to the coasts of California, housing many threatened and endangered species. Due to the invasion of non-native plants, many areas of CSS have type converted to annual grasslands and the fire frequency has accelerated; fire in turn, may facilitate further invasion, leading to a loss of biodiversity. While many studies document post-fire succession in these communities, pre-fire data are rarely available for comparison, especially data on seedling emergence. I analyzed post-fire recovery of a type-converted grassland community, comparing seedling emergence data for the first and third year after fire to the three years preceding the fire. Non-native species abundances declined more after the fire than did native abundances. This pattern was still present in 2015, three years post-fire. Two native species, Amsinckia menziesii var. intermedia (Amsinckia) and Phacelia distans (Phacelia), were subjects of seed addition treatments pre-fire, but I found no evidence that past seeding increased their abundances post-fire. Amsincki did recover to its pre-fire density three years after the fire, while the density of Phacelia declined over 75% in both the year immediately post-fire and three years after the fire. However, a third native species, Lupinus bicolor (Lupinus), was both much more abundant and also more spatially widespread both immediately after the fire and two years later. This supports the hypothesis that Lupinus is stored in the soil seed bank and the fire may have given this species the opportunity to recover by lowering abundances of non-native competitors. This analysis will inform future conservation efforts by improving our understanding of how seed banks impact the post-fire recovery of native species.
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Flesch, Aaron D., Philip C. Rosen, and Peter Holm. "Long-term changes in abundances of Sonoran Desert lizards reveal complex responses to climatic variation." Wiley, 2017. http://hdl.handle.net/10150/626024.
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Understanding how climatic variation affects animal populations and communities is essential for addressing threats posed by climate change, especially in systems where impacts are projected to be high. We evaluated abundance dynamics of five common species of diurnal lizards over 25 years in a Sonoran Desert transition zone where precipitation decreased and temperature increased across time, and assessed hypotheses for the influence of climatic flux on spatiotemporal variation in abundances. We repeatedly surveyed lizards in spring and summer of each year at up to 32 sites, and used hierarchical mixture models to estimate detection probabilities, abundances, and population growth rates. Among terrestrial species, abundances of a short-lived, winter-spring breeder increased markedly by an estimated 2375285% across time, while two larger spring-summer breeders with higher thermal preferences declined by up to 64%. Abundances of two arboreal species that occupy shaded and thus sheltered microhabitats fluctuated but did not decline systematically. Abundances of all species increased with precipitation at short lag times (151.5 yrs) likely due to enhanced food availability, but often declined after periods of high precipitation at longer lag times (254 yrs) likely due to predation and other biotic pressures. Although rising maximum daily temperatures (Tmax) are expected to drive global declines of lizards, associations with Tmax were variable and weak for most species. Instead, abundances of all species declined with rising daily minimum temperatures, suggesting degradation of cool refugia imposed widespread metabolic or other costs. Our results suggest climate warming and drying are having major impacts on lizard communities by driving declines of species with traits that augment exposure to abiotic extremes and by modifying species interactions. The complexity of patterns we report indicate that evaluating and responding to the influence of climate change on biodiversity must consider a broad array of ecological processes.
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DuFour, Mark R. "Hydroacoustic Quantification of Lake Erie Walleye (Sander vitreus)Distribution and Abundance." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1483715286731694.
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Reynolds, Julia Mae. "Effects of Model Design and Environmental Variables on Juvenile U.S. South Atlantic King Mackerel (Scomberomorus cavalla) Abundance." Thesis, College of Charleston, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10746023.
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As growing human populations put an increasing demand on finite ocean resources, fisheries management tools rely ever more on high quality inputs and a comprehensive understanding of model factors. Stock assessment modeling for South Atlantic (SA) King Mackerel, Scomberomorus cavalla , uses inputs such as abundance indices, growth parameters, and fisheries landings. However, one underlying assumption in this modeling system is there are measurable connections among life stages. A juvenile abundance index developed from the SEAMAP-SA Coastal Trawl Survey (CTS) is presumed to represent ecological recruitment. Very weak correlations to other life stage proxies suggested a deficiency with the juvenile abundance index accuracy and indicated data exploration into the index formulation was needed. Examination of CTS juvenile length frequencies support that the smallest juveniles appear in the summer and spring juveniles are from overwintering of the previous year class. Juvenile abundance indices developed using year class (year in which a fish is spawned) rather than year of sampling (as done for previous assessments) showed substantial differences, in particular lowering AIC values indicating an improvement in model accuracy. Evidence of seasonal and regional variation with CTS juveniles prompted the development of separate age 0 and age 1 indices. Correlations of these indices to fisheries-derived year class strength suggested the age 0 index to be the best indicator of initial juvenile king mackerel abundance while the age 1 index reflects abundance after high early life stage mortality. Data exploration also was conducted for potential environmental variables impacting age 0 and age 1 abundance. Relationships were found between age 0 abundance and freshwater input, the Gulf Stream, hurricane activity, and predator abundance and between age 1 abundance and freshwater input and hurricane activity. This research provides not only valuable baseline knowledge for SA king mackerel juveniles, but also findings pertinent for their management.
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Fässler, Sascha M. M. "Target strength variability in Atlantic herring (Clupea harengus) and its effect on acoustic abundance estimates." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1703.
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Acoustic survey techniques are widely used to quantify abundance and distribution of a variety of pelagic fish such as herring (Clupea harengus). The information provided is becoming increasingly important for stock assessment and ecosystem studies, however, the data collected are used as relative indices rather than absolute measures, due to the uncertainty of target strength (TS) estimates. A fish’s TS is a measure of its capacity to reflect sound and, therefore, the TS value will directly influence the estimate of abundance from an acoustic survey. The TS is a stochastic variable, dependent on a range of factors such as fish size, orientation, shape, physiology, and acoustic frequency. However, estimates of mean TS, used to convert echo energy data from acoustic surveys into numbers of fish, are conveniently derived from a single metric - the fish length (L). The TS used for herring is based on TS-L relationships derived from a variety of experiments on dead and caged fish, conducted 25-30 years ago. Recently, theoretical models for fish backscatter have been proposed to provide an alternative basis for exploring fish TS. Another problem encountered during acoustic surveys is the identification of insonified organisms. Trawl samples are commonly collected for identification purposes, however, there are several selectivity issues associated with this method that may translate directly into biased acoustic abundance estimates. The use of different acoustic frequencies has been recognised as a useful tool to distinguish between different species, based on their sound reflection properties at low and high frequencies. In this study I developed theoretical models to describe the backscatter of herring at multiple frequencies. Data collected at four frequencies (18, 38, 120 and 200 kHz) during standard acoustic surveys for herring in the North Sea were examined and compared to model results. Multifrequency backscattering characteristics of herring were described and compared to those of Norway pout, a species also present in the survey area. Species discrimination was attempted based on differences in backscatter at the different frequencies. I examined swimbladder morphology data of Baltic and Atlantic herring and sprat from the Baltic Sea. Based on these data, I modelled the acoustic backscatter of both herring stocks and attempted to explain differences previously observed in empirical data. I investigated the change in swimbladder shape of herring, when exposed to increased water pressures at deeper depths, by producing true shapes of swimbladders from MRI scans of herring under pressure. The swimbladder morphology representations in 3-D were used to model the acoustic backscatter at a range of frequencies and water pressures. I developed a probabilistic TS model of herring in a Bayesian framework to account for uncertainty associated with TS. Most likely distributions of model parameters were determined by fitting the model to in situ data. The resulting probabilistic TS was used to produce distributions of absolute abundance and biomass estimates, which were compared to official results from ICES North Sea herring stock assessment. Modelled backscatter levels of herring from the Baltic Sea were on average 2.3 dB higher than those from herring living in northeast Atlantic waters. This was attributed to differences in swimbladder sizes between the two herring stocks due to the lower salinity Baltic Sea compared to Atlantic waters. Swimbladders of Baltic herring need to be bigger to achieve a certain degree of buoyancy. Morphological swimbladder dimensions of Baltic herring and sprat were found to be different. Herring had a significantly larger swimbladder height at a given length compared to sprat, resulting in a modelled TS that was on average 1.2 dB stronger. Water depth, and therefore the increase in ambient pressure, was found to have a considerable effect on the size and shape of the herring swimbladder. Modelled TS values were found to be around 3 dB weaker at a depth of 50 m compared to surface waters. At 200 m, this difference was estimated to be about 5 dB. The Bayesian model predicted mean abundances and biomass were 23 and 55% higher, respectively, than the ICES estimates. The discrepancy was linked to the depth-dependency of the TS model and the particular size-dependent bathymetric distribution of herring in the survey area.
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Chen, Wei-Ching. "Selective Oxidation of Lignin Models and Extracts with Earth-Abundant Transition Metals and Hypervalent Iodine." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32181.
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As a significant component of lignocellulosic biomass, lignin represents a potential source of value-added aromatic chemicals. In this thesis, catalytic systems with earth-abundant metal catalysts such as molybdenum(VI) and hypervalent iodine complexes were developed to selectively break down lignin models into lower molecular weight chemicals under mild conditions. Due to the complexity of lignin, simple lignin model substrates (A to E), representing common linkages in lignin, were used to investigate the catalytic activity/selectivity of these catalysts. With the molybdenum catalysts [7– 11]/SPC/Adogen®464 system (SPC = sodium percarbonate), oxidation of simple β-1 model compound A in acetonitrile showed primarily C-H bond cleavage to form the ketone product, benzoin methyl ether, whereas the Cα-Cβ bond cleavage product, methyl benzoate, was obtained by switching the reaction solvent to benzonitrile. Preference for generating the Cα-Cβ bond cleavage product, i.e. benzaldehyde, can also be achieved with other early to middle transition metal catalysts using H2O2(aq) as the terminal oxidant. Stoichiometric amounts of hypervalent iodine/Lewis acid systems [20a-c] were able to selectively cleave Cα-Cβ bonds to aldehydes with both simple β-1 model compound A and β-O-4 model compound C. In contrast, other lignin model compounds with different linkages were unable to be oxidized to a great extent using these Mo- or iodine-based complexes. The catalytic activity and selectivity of the reported vanadium complexes, copper salts and non-metal system 1-5 on non-volatile organosolv (NVO) lignin was investigated under basic condition. Details of the depolymerisation of lignin were determined by using Gel Permeation Chromatography (GPC) and the two-dimensional NMR technique, quantitative HSQC (q-HSQC) spectroscopy. Vanadium [2] and copper systems were found to be the most active for depolymerization of NVO lignin.
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Gosse, John W. "Relative abundances of birds of prey in different forest habitats in the Western Newfoundland Model Forest /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25845.pdf.
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Falcao, de Jesus Manuel Jose Romao Xavier. "Civil war and natural resources : a quantitative approach." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1140.
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Marchetto, Camila. "Estimativas de abundância do boto-cinza (sotalia guianensis) (cetacea, delphinidae) no complexo estuarino de paranaguá utilizando modelos de captura-recaptura." Universidade do Vale do Rio dos Sinos, 2011. http://www.repositorio.jesuita.org.br/handle/UNISINOS/3970.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
FAPESP - Fundação de Amparo à Pesquisa do Estado de São Paulo
Estimativas de abundância populacional são consideradas importantes parâmetros ecológicos. Estudos envolvendo estes parâmetros são escassos e concentrados em regiões específicas da distribuição do boto-cinza (Sotalia guianensis). O objetivo deste estudo foi obter a estimativa da abundância populacional desta espécie em um setor do Complexo Estuarino de Paranaguá (PR) (25º22’S – 25º27’S; 48º12’W – 48º40’W). Foram realizadas saídas a campo para aplicação da técnica de fotoidentificação no período compreendido entre o inverno de 2006 e o inverno de 2008. Uma área total de 110 km² foi dividida em três subáreas menores para que cada parte selecionada fosse amostrada em um dia. Para as saídas a campo utilizou-se uma embarcação de alumínio realizando um deslocamento em zig-zag pelo estuário a fim de aumentar a chance de encontro com os grupos de botos. A fotoidentificação foi realizada com uma câmera digital reflex 35 mm, acoplada a lentes zoom de 400 mm. As fotos tomadas foram classificadas em categorias de acordo com o foco, contraste e tamanho da nadadeira dorsal em relação à distância do fotógrafo. Para a estimativa de abundância da população utilizaram-se modelos de captura-recaptura para populações fechadas. Durante o período de estudo foram realizadas 39 saídas a campo com 227 grupos de botos que variaram de dois a 100 indivíduos (média ± DP: 12,7 ± 16,6 indivíduos). Um total de 40.340 fotografias foi tomado, sendo 13.522 (33,5%) consideradas de qualidade suficiente para serem analisadas. Dentre as fotografias de excelente qualidade, 3.114 ou 23,03% foram de indivíduos que possuíam marcas conspícuas nas nadadeiras dorsais e que permitiram uma identificação individual, totalizando 109 indivíduos diferentes identificados ao longo das temporadas de estudo. A estimativa do tamanho da população variou de 200 a 441 indivíduos dependendo do modelo utilizado. Esta pode ser considerada uma estimativa mínima, visto que somente uma parte do Complexo Estuarino de Paranaguá foi amostrada neste estudo. Em vista disso, recomenda-se amostrar toda a extensão do CEP para obter a estimativa total da população local. Do mesmo modo, este dado é importante para compor o banco de informações da Área de Proteção Ambiental de Guaraqueçaba, contribuindo para o desenvolvimento de estratégias de conservação do boto-cinza e de outros recursos biológicos locais.
Population abundance estimates can be considered one of the most important ecological parameters. Studies on Guiana dolphin (Sotalia guianensis) estimates are scarce and concentrated in specific areas of its distribution. The objective of the present study was to estimate the population size of this species in a sector of the Paranaguá Estuarine Complex (PEC) (25º22’S – 25º27’S; 48º12’W – 48º40’W), state of Paraná, Brazil. Surveys were conducted to apply the technique of photo-identification from winter 2006 to winter 2008. An area of 110 km² was divided into three smaller subareas to allow each selected portion of the estuary to be surveyed in a day. Boat-based surveys followed a random zig-zag pattern in the estuary in order to maximize the chance of encountering groups of dolphins. The photoidentification was performed using a 35 mm reflex digital camera with a 400 mm zoom lens. Photographs were classified into categories according to the focus, contrast and size of the dorsal fin in relation to distance from the photographer. Capture-recapture models for closed populations were used. A total of 39 surveys was conducted and 227 groups of dolphins were recorded, ranging from two to 100 individuals (mean ± SD: 12.7 ± 16.6 individuals). A total of 40.340 photographs was taken, from which 13.522 (33.5%) were considered useful for identification purposes. A total of 3.114 (23.03%) photographs allowed individual identification, resulting in 109 individuals identified through different seasons. The estimates gathered ranged from 200 to 441 individuals depending on the selected model. This is a minimum estimate, since only a part of the Paranaguá Estuarine Complex was sampled. It is recommended to survey the whole estuarine area where dolphins can be found in order to reach an accurate estimate of the total population size. This study adds another information to the database of the Environmental Protection Area of Guaraqueçaba, contributing to the development of conservation strategies of estuarine dolphins and other local biological resources.
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Dénes, Francisco Voeroes. "Abundância de aves de rapina no Cerrado e Pantanal do Mato Grosso do Sul e os efeitos da degradação de hábitat: perspectivas com métodos baseados na detectabilidade." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/41/41133/tde-15012015-152016/.
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A urbanização e a expansão das fronteiras agrícolas na região Neotropical estão entre as principais forças causadoras da degradação ambiental em hábitats abertos naturais. Inferências e estimativas de abundância são críticas para quantificação de dinâmicas populacionais e impactos de mudanças ambientais. Contudo, a detecção imperfeita e outros fenômenos que causam inflação de zeros podem induzir erros de estimativas e dificultar a identificação de padrões ecológicos. Examinamos como a consideração desses fenômenos em dados de contagens de indivíduos não marcados pode informar na escolha do método apropriado para estimativas populacionais. Revisamos métodos estabelecidos (modelos lineares generalizados [GLMs] e amostragem de distância [distance sampling]) e emergentes que usam modelos hierárquicos baseados em misturas (N-mixture; modelo de Royle-Nichols [RN], e N-mixture básico, zero inflacionado, espacialmente explicito, visita única, e multiespécies) para estimar a abundância de populações não marcadas. Como estudo de caso, aplicamos o método N-mixture baseado em visitas únicas para modelar dados de contagens de aves de rapina em estradas e investigar como transformações de habitat no Cerrado e Pantanal do Mato Grosso do Sul afetaram as populações de 12 espécies em uma escala regional (>300.000 km2). Os métodos diferem nos pré-requisitos de desenho amostral, e a sua adequabilidade depender da espécie em questão, da escala e objetivos do estudo, e considerações financeiras e logísticas, que devem ser avaliados para que verbas, tempo e esforço sejam utilizados com eficiência. No estudo de caso, a detecção de todas as espécies foi influenciada pela horário de amostragem, com efeitos congruentes com expectativas baseadas no comportamentos de forregeamento e de voo. A vegetação fechada e carcaças também influenciaram a detecção de algumas espécies. A abundância da maioria das espécies foi negativamente influenciada pela conversão de habitats naturais para antrópicos, particularmente pastagens e plantações de soja e cana-de-açúcar, até mesmo para espécies generalistas consideradas como indicadores ruins da qualidade de hábitats. A proteção dos hábitats naturais remanescentes é essencial para prevenir um declínio ainda maior das populações de aves de rapina na área de estudo, especialmente no domínio do CerradoUrbanization and the expansion of agricultural frontiers are among the main forces driving the degradation of natural habitats in Neotropical open habitats. Inference and estimates of abundance are critical for quantifying population dynamics and the impacts of environmental change. Yet imperfect detection and other phenomena that cause zero inflation can induce estimation error and obscure ecological patterns. We examine how detection error and zero-inflation in count data of unmarked individuals inform the choice of analytical method for estimating population size. We review established (GLMs and distance sampling) and emerging methods that use N-mixture models (Royle-Nichols model, and basic, zero-inflated, temporary emigration, beta-binomial, generalized open-population, spatially explicit, single-visit and multispecies) to estimate abundance of unmarked populations. As a case study, we employed a single visit N-mixture approach to model roadside raptor count data and investigate how land-use transformations in the Cerrado and Pantanal domains in Brazil have affected the populations of 12 species on a regional scale (>300,000 km2). Methods differ in sampling design requirements, and their suitability will depend on the study species, scale and objectives of the study, and financial and logistical considerations, which should be evaluated to use funds, time and effort efficiently. In the case study, detection of all species was influenced by time of day, with effects that follow expectations based on foraging and flying behavior. Closed vegetation on and carcasses found during surveys also influenced detection of some species. Abundance of most species was negatively influenced by conversion of natural Cerrado and Pantanal habitats to anthropogenic uses, particularly pastures, soybean and sugar cane plantations, even for generalist species usually considered poor habitat-quality indicators. Protection of the remaining natural habitats is essential to prevent further decline of raptor populations in the study area, especially in the Cerrado domain