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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Thermal ecology of the Glanville Fritillary butterfly (Melitaea cinxia)

Advani, Nikhil Kishore 08 October 2012 (has links)
Anthropogenic climate warming is predicted to accelerate over the next century, with potentially dramatic consequences for wildlife. It is important to understand as well as possible how different organisms will respond to this stress. This project seeks to gain a better mechanistic understanding of the thermal biology of the Glanville Fritillary butterfly (Melitaea cinxia) at the latitudinal and elevational extremes of its range. Investigation of the temperatures at which adult butterflies took spontaneous flight revealed a significant difference between populations from the elevational extremes, with insects from high elevation taking flight at lower thoracic temperatures than those from low elevation. Contrary to expectation, there was no systematic effect of latitude on takeoff temperature. If these measures represent adaptation to climate, then these effects are not simple and the influences of elevation and latitude are not the same. Investigation of thermal tolerance across all life cycle stages found no difference in larval performance between the populations tested. There was however an effect of treatment. This suggests that in M. cinxia, even populations from different extremes of the range may not differ in their thermal tolerance. The effect of treatment suggests that there is temperature-induced plasticity. The adaptive significance of this has been explored to some extent. Investigation of heat shock protein expression between the latitudinal extremes finds no difference in Hsp21.4 expression when exposed to heat stress, however both Hsp20.4 and Hsp90 were upregulated in response to heat stress. For Hsp20.4, there were significant differences in expression between the populations. Finally, a species distribution model using maximum entropy techniques was conducted for M. cinxia, predicting both the current and future (2100) distributions of the species. The model closely matches the known current distribution, and predicts a clear northward range shift in response to climate change. / text
32

Distributed Photovoltaics, Household Electricity Use and Electric Vehicle Charging : Mathematical Modeling and Case Studies

Munkhammar, Joakim January 2015 (has links)
Technological improvements along with falling prices on photovoltaic (PV) panels and electric vehicles (EVs) suggest that they might become more common in the future. The introduction of distributed PV power production and EV charging has a considerable impact on the power system, in particular at the end-user in the electricity grid. In this PhD thesis PV power production, household electricity use and EV charging are investigated on different system levels. The methodologies used in this thesis are interdisciplinary but the main contributions are mathematical modeling, simulations and data analysis of these three components and their interactions. Models for estimating PV power production, household electricity use, EV charging and their combination are developed using data and stochastic modeling with Markov chains and probability distributions. Additionally, data on PV power production and EV charging from eight solar charging stations is analyzed. Results show that the clear-sky index for PV power production applications can be modeled via a bimodal Normal probability distribution, that household electricity use can be modeled via either Weibull or Log-normal probability distributions and that EV charging can be modeled by Bernoulli probability distributions. Complete models of PV power production, household electricity use and EV home-charging are developed with both Markov chain and probability distribution modeling. It is also shown that EV home-charging can be modeled as an extension to the Widén Markov chain model for generating synthetic household electricity use patterns. Analysis of measurements from solar charging stations show a wide variety of EV charging patterns. Additionally an alternative approach to modeling the clear-sky index is introduced and shown to give a generalized Ångström equation relating solar irradiation to the duration of bright sunshine. Analysis of the total power consumption/production patterns of PV power production, household electricity use and EV home-charging at the end-user in the grid highlights the dependency between the components, which quantifies the mismatch issue of distributed intermittent power production and consumption. At an aggregate level of households the level of mismatch is shown to be lower.
33

Untersuchung der Lebensraumansprüche des Grauspechts Picus canus und seiner Verbreitungsgrenze in Niedersachsen / Investigating the habitat demands of the Grey-headed Woodpecker Picus canus and its distribution border in Lower Saxony

Schneider, Mareike 06 June 2018 (has links)
No description available.
34

Effects of Climate Change and Urban Development on the Distribution and Conservation of Vegetation in a Mediterranean Type Ecosystem

January 2012 (has links)
abstract: Climate and land use change are projected to threaten biodiversity over the coming century. However, the combined effects of these threats on biodiversity and the capacity of current conservation networks to protect species' habitat are not well understood. The goals of this study were to evaluate the effect of climate change and urban development on vegetation distribution in a Mediterranean-type ecosystem; to identify the primary source of uncertainty in suitable habitat predictions; and to evaluate how well conservation areas protect future habitat in the Southwest ecoregion of the California Floristic Province. I used a consensus-based modeling approach combining three different species distribution models to predict current and future suitable habitat for 19 plant species representing different plant functional types (PFT) defined by fire-response (obligate seeders, resprouting shrubs), and life forms (herbs, subshurbs). I also examined the response of species grouped by range sizes (large, small). I used two climate models, two emission scenarios, two thresholds, and high-resolution (90m resolution) environmental data to create a range of potential scenarios. I evaluated the effectiveness of an existing conservation network to protect suitable habitat for rare species in light of climate and land use change. The results indicate that the area of suitable habitat for each species varied depending on the climate model, emission scenario, and threshold combination. The suitable habitat for up to four species could disappear from the ecoregion, while suitable habitat for up to 15 other species could decrease under climate change conditions. The centroid of the species' suitable environmental conditions could shift up to 440 km. Large net gains in suitable habitat were predicted for a few species. The suitable habitat area for herbs has a small response to climate change, while obligate seeders could be the most affected PFT. The results indicate that the other two PFTs gain a considerable amount of suitable habitat area. Several rare species could lose suitable habitat area inside designated conservation areas while gaining suitable habitat area outside. Climate change is predicted to be more important than urban development as a driver of habitat loss for vegetation in this region in the coming century. These results indicate that regional analyses of this type are useful and necessary to understand the dynamics of drivers of change at the regional scale and to inform decision making at this scale. / Dissertation/Thesis / M.S. Biology 2012
35

Distribuição potencial e impacto de mudanças climáticas sobre a praga de girassol Chlosyne lacinia (Lepidoptera: Nymphalidae) / Potential distribution and climate change impact over the sunflower pest Chlosyne lacinia (Lepidoptera: Nymphalidae)

Fortes, Juliana Chagas 29 July 2009 (has links)
Made available in DSpace on 2015-03-26T13:30:25Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2387526 bytes, checksum: 1c1a1ee21f9822c506e9add7896843e9 (MD5) Previous issue date: 2009-07-29 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The existence of global climate change caused by anthropogenic impacts and the importance of predicting its biological effects have revived the interest in understanding abundance and distribution determining factors. Several methods that allow the creation of climate based ecological niche models can be used to predict species potential distribution and the effects that climate change can have over distributional areas. Building such models can help the understanding on how climate can determine species distributions, as well as indicating pest infestation risk areas. Chlosyne lacinia caterpillars are a major sunflower (Helianthus annuus) pest on Brazil, and its attacks at 50 and 70 days old plants can reduce the productivity up to 80%. This work aimed at areas with suitable climate for the current and future potential occurrence of C. lacinia and its subspecies at the American continent, and for sunflower culture in Brazil. The models were created using Mahalanobis distance and Maximum Entropy (Maxent) methods, for C. lacinia and the subspecies C. l. adjutrix, C. l. crocale, C. l. lacinia and C. l. saundersii. According to AUC (area under the sensibility versus specificity curve) values, model performance were great, which explains the similarity of results from both methods. The results showed that it is possible that the whole species distribution may not be altered by climate changes, but the intra-specific variation will be largely affected. C. l. saundersii distribution is expected to shrink and be isolated, and C. l. adjutrix can loose all suitable areas. However, hese results can be affected by the gene flow between subspecies. The areas with suitable climates for sunflower culture in Brazil are expected descrease, although it is possible that genetic improvement efforts can surpass climatic limitations, allowing the occupancy of areas not predicted by the modeling, and avoiding the effect of the pest. Even though distribution modeling methods are seldom used for pest distribution predictions, its usage proved to be an interesting method for obtaining information about the species and the intra-specific variation. / A existência de alterações climáticas globais como conseqüência de impactos antropogênicos e a importância de prever seus efeitos biológicos reavivaram o interesse em compreender os fatores que determinam a abundância e a distribuição dos organismos. Existem vários métodos que permitem a criação de modelos de nicho ecológico baseados em clima, que podem ser usados para prever a distribuição potencial de espécies e os potenciais efeitos de mudanças climáticas em sua área de distribuição. A construção destes tipos de modelos pode auxiliar a compreender como o clima pode controlar a distribuição das espécies, como também indicar áreas de risco para a infestação de pragas. Lagartas de Chlosyne lacinia, no Brasil, são uma das principais pragas de girassol, Helianthus annuus, e o seu ataque aos 50 e 70 dias de idade das plantas reduz a produtividade em até 80%. O objetivo desse trabalho foi determinar as áreas com clima favorável para a ocorrência potencial atual e futura de C. lacinia e de suas subespécies no continente americano, e para a plantação de girassol no Brasil. Os modelos foram criados utilizando-se os métodos de distância de Mahalanobis e Maximum Entropy (Maxent), para a distribuição da espécie C. lacinia, e das subespécies C. l. adjutrix, C. l. crocale, C. l. lacinia e C. l. saundersii. De acordo com os valores de AUC (área sob a curva de sensibilidade versus especificidade) os modelos foram bastante satisfatórios, o que também justifica a semelhança na distribuição das espécies entre ambos os modelos. Os resultados mostram que é possível que a distribuição de uma espécie não se altere como função das mudanças climáticas, mas que a variação intra-específica seja largamente afetada. A subespécie C. l. saundersii apresenta uma possível diminuição da áreas de distribuição potencial e um isolamento geográfico, enquanto a subespécie C. l. adjutrix, futuramente, não apresentará áreas de adeqüabilidade. No entanto, esses resultados podem ser alterados devido ao fluxo gênico existente na espécie. As áreas de clima adequados para a plantação de girassol no Brasil devem sofrer uma diminuição, embora os esforços na realização de melhoramento genético nessa cultura possa transpor as limitações climáticas, fazendo com que haja plantações em áreas não previstas pelos modelos e a diminuição do efeito da praga na cultura. Embora esses métodos não sejam muito utilizados para a predição de áreas adequadas para pragas, o uso de modelos de distribuição mostrou-se uma ferramenta interessante para a obtenção de dados sobre a espécie e de variações intra-específicas.
36

Distribuição potencial e atual do tamanduá-bandeira (Myrmecophaga tridactyla) e indicação de áreas prioritárias para sua conservação / Potential and current distribution of giant anteater (Myrmecophaga tridactyla) and identification of priority areas for its conservation

Vinicius Alberici Roberto 11 December 2017 (has links)
O tamanduá-bandeira (Myrmecophaga tridactyla) se distribui amplamente ao longo da região Neotropical, porém é provável que esteja extinto da maior parte de sua extensão original, notadamente na América Central e nos limites austrais de sua distribuição. O táxon está ameaçado de extinção globalmente (IUCN) e também em âmbito nacional. Embora historicamente a espécie ocorra em todos os biomas brasileiros, hoje é considerada extinta nos Pampas, quase extinta na Mata Atlântica, sendo que na Caatinga sua presença necessita de confirmação e no Cerrado suas populações vem sofrendo drásticas reduções. Atualmente não há estudos de revisão da distribuição da espécie nos biomas brasileiros, tão pouco foi avaliado se as áreas mais adequadas à espécie estão sendo protegidas e o conhecimento existente é insuficiente para adotar estratégias de conservação adequadas. Dessa maneira, o presente estudo teve como principal objetivo modelar a distribuição potencial e atual do tamanduá-bandeira no Brasil e nos biomas brasileiros, a fim de identificar quais variáveis preditoras melhor explicam a ocorrência da espécie em diferentes escalas. Além disso, a partir dos modelos de distribuição atual, os biomas foram avaliados quanto à adequabilidade ambiental (i.e. probabilidade de presença) e foram realizadas uma análise de lacunas e a identificação de áreas prioritárias para a conservação. A distribuição potencial do tamanduá-bandeira foi melhor explicada em escala continental, por variáveis bioclimáticas (sazonalidade de temperatura e precipitação) e topográficas (altitude), enquanto que a distribuição atual foi bem explicada nas duas escalas, por variáveis de uso e cobertura da terra (porcentagens de cobertura arbórea, de silvicultura e de cana-de-açúcar). O Cerrado foi o bioma de maior adequabilidade ambiental à espécie, seguido da Amazônia, Pantanal, Mata Atlântica e Caatinga, sendo que não foram obtidos registros recentes para os Pampas. Menos de 10% da distribuição atual do tamanduá-bandeira no Cerrado e Pantanal encontra-se protegida por Unidades de Conservação, existindo uma lacuna parcial de conservação. Áreas prioritárias para a espécie incluem um corredor central no Cerrado, grande parte do Pantanal e áreas de transição (ecótonos) com outros biomas. Os resultados obtidos neste estudo permitiram preencher lacunas de conhecimento acerca da distribuição do tamanduá-bandeira, bem como dar suporte para o planejamento de sua conservação. / The giant anteater (Myrmecophaga tridactyla) is widely distributed throughout the Neotropical region, but is probably extinct from most of its range, notably in Central America and the southern limits of its distribution. The species is listed as Vulnerable on the IUCN and national Red Lists. Although historically present in all Brazilian biomes, there are no studies reviewing its distribution, nor has it been evaluated if the Brazilian federal conservation units are protecting the areas most suitable to the species. Thus, the aim of this study was to model the potential and current distribution of the giant anteater in Brazil and Brazilian biomes, to identify which predictor variables best explain the occurrence of the species at different scales. Current distribution models were used to evaluate the biomes environmental suitability (i.e. probability of presence) and a gap analyses were performed. Also, priority areas for conservation were identified. The potential distribution of the anteater was better explained on a continental scale by bioclimatic (seasonality of temperature and precipitation) and topographic (altitude) variables, while the current distribution was well predicted in both scales, by land cover variables (percentages of tree cover, silviculture, and sugarcane). The Cerrado was the biome of greater environmental suitability to the species, followed by the Amazon, the Pantanal, the Atlantic Forest and the Caatinga. No recent records were obtained for the Pampas. Conservation units protect less than 10% of the current distribution of the giant anteater in the Cerrado and Pantanal. Priority areas for the species include a central corridor in the Cerrado, much of the Pantanal and ecotones. The results obtained in this study helped to fill knowledge gaps on the distribution of the giant anteater in Brazil, supporting actions for its conservation.
37

Ensemblemodellering av piggvarens habitat utgående från provfiske- och miljödata / Ensemble modelling of the habitat of turbot based on video analyses and fish survey data

Erlandsson, Mårten January 2016 (has links)
Piggvarens (Scophthalmus maximus) val av habitat i Östersjön har modellerats utifrån provfiskedata och miljövariabler. Vid totalt 435 stationer i Östersjön har data samlats in i form av provfiske, CTD-mätningar (konduktivitet, temperatur och djup) och videofilmer. Genom att analysera videofilmerna från havsbotten i Östersjön har den klassificerats efter fyra olika förklaringsvariabler: täckningsgrad mjukbotten, strukturbildande växter, övriga alger och täckningsgrad blåmusslor. Ytterligare sex förklaringsvariabler har samlats in från mätningar och befintliga kartor: bottensalinitet, bottentemperatur, djup, siktdjup, vågexponering och bottenlutning. Dessa tio förklaringsvariabler har använts i tio olika enskilda statistiska modelleringsmetoder med förekomst/icke-förekomst av piggvar som responsvariabel. Nio av tio modeller visade på bra resultat (AUC > 0,7) där CTA (Classification Tree Analysis) och GBM (Global Boosting Model) hade bäst resultat (AUC > 0,9). Genom att kombinera modeller med bra resultat på olika sätt skapades sex ensemblemodeller för att minska varje enskild modells svagheter. Ensemblemodellerna visade tydligt fördelarna med denna typ av modellering då de gav ett mycket bra resultat (AUC > 0,949). Den sämsta ensemblemodellen var markant bättre än den bästa enskilda modellen. Resultaten från modellerna visar att största sannolikheten för piggvarsförekomst i Östersjön är vid grunt (< 20 meter) och varmt (> 10 oC) vatten med hög vågexponering (> 30 000 m²/s). Dessa tre variabler var de med högst betydelse för modellerna. Täckningsgrad mjukbotten och de två växtlighetsvariablerna från videoanalyserna var de tre variabler som hade lägst påverkan på piggvarens val av habitat. Med en högre kvalitet på videofilmerna hade de variablerna kunnat klassificeras i mer specifika grupper vilket eventuellt gett ett annat resultat. Generellt visade modellerna att denna typ av habitatmodellering med provfiske och miljödata både är möjlig att utföra. / The turbots’ (Scophthalmus maximus) selection of habitat in the Baltic Sea has been modeled on the basis of fish survey data and environmental variables. At a total of 435 stations in the Baltic Sea, data was collected in the form of fish survey data, CTD (Conductivity, Temperature and Depth) measurements and videos. By analyzing the videos from the seabed of the Baltic Sea, four different explanatory variables have been classified: coverage of soft bottom, structure-forming plants, other algae and coverage of mussels. Another six explanatory variables have been collected from measurements and existing rasters: salinity, temperature, depth, water transparency, wave exposure and the bottom slope. These ten explanatory variables have been used in ten different species distribution modeling methods with the presence/absence of turbot as a response variable. Nine out of ten models showed good results (AUC > 0.7) where the CTA (Classification Tree Analysis) and GBM (Global Boosting Model) performed the best (AUC > 0.9). By combining the models with good performance in six different ensemble models each individual models’ weaknesses were decreased. The ensemble models clearly showed strength as they gave a very good performance (AUC > 0.94). The worst ensemble model was significantly better than the best individual model. The results of the models show that the largest probability of occurrence of turbot in the Baltic Sea is in shallow (< 20 m) and warm (> 10 ° C) water with high wave exposure (> 30,000 m²/s). These three variables were those with the highest significance for the models. Coverage of soft bottom and the two vegetation variables, from the video analyzes, had the lowest impact on the turbots’ choice of habitat. A higher quality of the videos would have made it possible to classify these variables in more specific groups which might have given a different result. Generally, the models showed that this type of modeling of habitat is possible to perform with fish survey and environmental monitoring data and generates useful results.
38

Ecological analysis of large floristic and plant-sociological datasets – opportunities and limitations

Goedecke, Florian 04 May 2018 (has links)
No description available.
39

Predicting Glass Sponge (Porifera, Hexactinellida) Distributions in the North Pacific Ocean and Spatially Quantifying Model Uncertainty

Davidson, Fiona 07 January 2020 (has links)
Predictions of species’ ranges from distribution modeling are often used to inform marine management and conservation efforts, but few studies justify the model selected or quantify the uncertainty of the model predictions in a spatial manner. This thesis employs a multi-model, multi-area SDM analysis to develop a higher certainty in the predictions where similarities exist across models and areas. Partial dependence plots and variable importance rankings were shown to be useful in producing further certainty in the results. The modeling indicated that glass sponges (Hexactinellida) are most likely to exist within the North Pacific Ocean where alkalinity is greater than 2.2 μmol l-1 and dissolved oxygen is lower than 2 ml l-1. Silicate was also found to be an important environmental predictor. All areas, except Hecate Strait, indicated that high glass sponge probability of presence coincided with silicate values of 150 μmol l-1 and over, although lower values in Hecate Strait confirmed that sponges can exist in areas with silicate values of as low as 40 μmol l-1. Three methods of showing spatial uncertainty of model predictions were presented: the standard error (SE) of a binomial GLM, the standard deviation of predictions made from 200 bootstrapped GLM models, and the standard deviation of eight commonly used SDM algorithms. Certain areas with few input data points or extreme ranges of predictor variables were highlighted by these methods as having high uncertainty. Such areas should be treated cautiously regardless of the overall accuracy of the model as indicated by accuracy metrics (AUC, TSS), and such areas could be targeted for future data collection. The uncertainty metrics produced by the multi-model SE varied from the GLM SE and the bootstrapped GLM. The uncertainty was lowest where models predicted low probability of presence and highest where the models predicted high probability of presence and these predictions differed slightly, indicating high confidence in where the models predicted the sponges would not exist.
40

Ecology of Rare and Abundant Raptors on an Oceanic Island the Sharp-Shinned Hawk and Red-Tailed Hawk in Puerto Rico

Gallardo, Julio C 10 August 2018 (has links)
Reliable estimates of species abundance, distribution, and population trajectories are critical in conservation and management. However, for many tropical species that information is missing. We conducted Sharp-shinned Hawk (SSHA) searches during the breeding seasons of 2013, 2014, and 2016 in eight montane forest reserves and their adjacent private lands of Puerto Rico. Further, we developed a maximum entropy model (MaxEnt) of the SSHA’s potential distribution using the following environmental variables: aspect, canopy closure, elevation, rainfall, slope, and terrain roughness. Elevation accounted for 89.8% of model fit, predicting the greatest probability of occurrence (> 60%) at elevations above 900 m. The model estimated 0.6% Puerto Rico (56.1 km2) has the greatest probability of occurrence. We developed a periodic population matrix model to describe influence of early life stages on population growth of the Red-tailed Hawk (RTHA) in eastern Puerto Rico. Our results suggest that the RTHA population has an average annual population increase of 5%, with rates differing between highlands (λh = 1.05) and 27% lowlands (λl = 1.27). Adult survival was the most important population growth parameter, with more effect in highlands (elasticity = 0.86) than in lowlands (elasticity = 0.53). Sensitivity of λ to changes in nestling survival was greater than for other life-stages (sensitivity lowlands = 0.46, sensitivity highlands = 0.48). I developed an open population N-mixture model to estimate abundance, availability, and detection probability of RTHA in the Luquillo Mountains and western Cordillera Central. The abundance estimates were 0.05 RTHA/ha, with an availability of (ϕ) = ~1 RTHA/per survey point and a detection probability (r) = ~0.25. In Luquillo Mountains, abundance was positively influenced by slope and elevation. In the western Cordillera Central, abundance of RTHA was constant across elevation, slope, and canopy closure. Detection probability decreased with increasing slope and wind conditions and showed a gradual small negative decrease with slope with reduced winds conditions. My findings are a contribution to our knowledge to how population traits and ecological constraints imposed by insular environments are influencing distribution, abundance, and population dynamics of raptors to propose management or conservation schemes.

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