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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.
11

Metapopulation viability of swamp rabbits (Sylvilagus aquaticus) in southern Illinois

Robinson, Christopher 01 August 2013 (has links)
Swamp rabbits (Sylvilagus aquaticus) in southern Illinois exist as a metapopulation due to loss and fragmentation of the bottomland hardwood forests in which they live, making their persistence in the state uncertain. I ran a spatially-explicit population viability analysis (PVA) on the metapopulation, using a habitat suitability map I created and life history parameters drawn from the literature. I varied parameters related to reproduction, survival, catastrophes, dispersal, and carrying capacity from 50 to 150% of the initial value of each parameter to compare their effects on extinction risk. I modified the map to test the effects of potential habitat loss, fragmentation, and the addition of dispersal corridors on the swamp rabbit metapopulation in southern Illinois. Under baseline conditions, the model suggested about a 20% chance of quasi-extinction (90% metapopulation decline) in 25 years. Changes in fecundity values and the effects of catastrophic flooding had the greatest effect on the risk of extinction, causing quasi-extinction probabilities to range from 0 to 100% and 0 to 87%, respectively. In contrast, changing dispersal values yielded the least impact on the risk of extinction (18-24%), and all other parameters had moderate impacts on the model. Removing groups of the largest habitat patches increased the risk of extinction, whereas removing groups of the smallest habitat patches decreased the risk of extinction, suggesting that small patches could act as population sinks with a negative impact on swamp rabbit persistence. Decreasing patch fragmentation per se reduced the risk of extinction slightly. The addition of dispersal corridors made no significant impact on the probability of extinction. My findings indicate that more research estimating fecundity and the effect of catastrophic floods on swamp rabbits in Illinois is required to more accurately predict swamp rabbit persistence in the state. I also suggest that managers should work to decrease the effect of flooding on the population by improving upland habitat, or decrease fragmentation by increasing the area of bottomland hardwood forests around existing habitat patches. Lastly, I suggest managers focus on preventing further habitat fragmentation into small patches, which will mitigate the creation of potential sink populations and will enable current populations to persist.
12

Proposição de um método para analisar a viabilidade da implantação de uma cadeia produtiva em um novo local: o caso da citricultura no pólo Petrolina-Juazeiro / The purpose of a method to analyze the viability of implanting a productive chain in a new place: the case of citriculture in Petrolina-Juazeiro.

Vinicius Gustavo Trombin 26 March 2007 (has links)
A todo momento as organizações precisam se adaptar às constantes mudanças do macroambiente. A ampliação da unidade de processamento ou, ainda, o transplante total ou parcial dessa unidade para um outro local é uma das respostas a essas freqüentes alterações. No entanto, sabe-se que a unidade de processamento é apenas um dos elos de uma cadeia produtiva com dependência vital entre os mesmos. Nesse sentido, o remanejamento ou a instalação de uma unidade de processamento num novo local não é apenas um problema de escolha da área para a instalação dessa unidade, também não pode ser analisado desconectado dos demais elos da cadeia produtiva que participam da produção, transformação e distribuição, pois, como mostra a literatura, o bom desenvolvimento de uma cadeia produtiva depende de que várias condições a montante e a jusante se combinem. Assim, o objetivo central deste trabalho é a proposição de um método de análise de viabilidade para a implantação de uma cadeia produtiva num local completamente novo para esta cadeia. O método foi realizado a partir da revisão de autores clássicos sobre o tema, e pretende-se que sirva de ferramenta para outras cadeias produtivas interessadas em projetos dessa natureza. O método contempla as seguintes etapas: (1) Estudo de Mercado, (2) Lições da Cadeia Produtiva, (3) Tamanho e Localização, (4) Produção Agrícola e Produção Industrial, (5) Sistemas de Distribuição, (6) Análise de Investimentos, Custos Operacionais e Receitas, (7) Avaliação Financeira e Macroeconômica, (8) Arranjos Institucionais e Estrutura de Governança, (9) Diferenciação do Produto. O método proposto foi aplicado num estudo para analisar a implantação da citricultura no Pólo Petrolina-Juazeiro, localizado no Vale São Francisco. Pôde-se com essa experiência constatar que o método pode ser utilizado por qualquer cadeia produtiva interessada em analisar novas áreas para se instalar, podendo ser necessário algum ajuste ou adaptação às especificidades da empresa ou do setor. / Being adapted to all the constant changes of the macro environment is a need to all the organizations nowadays. The extension of a processing unit or its partial or total exchange to another place are examples of these common changes. Having a crucial dependency, it is known that the processing unit is one of the links in a productive chain. Considering this fact, for a relocation or installation of a new processing unit in another place, a new area must be chosen and both transformation and distribution, elements of a productive chain, must be considered as well. As it is learned in the literature, a good development of a productive chain depends of different combinations. The main purpose of this work is to suggest a method of viability analysis for the implantation of a productive chain in a new place. The method was used after a severe revision based on expert authors of this subject and intends to help any productive chain which might be interested in the same projects. The method contemplates the following stages: (1) Market Study, (2) Studies of the productive chain, (3) Size and location, (4) Industrial and Agricultural production, (5) Distribution Systems, (6) Analyze of Investments, Operational costs and incomes, (7) Macroeconomic and Financial evaluation, (8) Governance Structures, (9) Product Differentiation. The method was tested and analyzed during the implantation of citriculture in the regions of Petrolina and Juazeiro, localized in the São Francisco Valley. To conclude with, the use of this method reveled that it can be used in any productive chain willing to test new areas to install, however, some adjustments or adaptations may be necessary to attend some specification of the business.
13

Population status and habitat use of Indian Ocean humpback dolphins (sousa plumbea) along the south coast of South Africa

Conry, Danielle Shanè January 2017 (has links)
Long-lived, top-level predators, such as some marine mammals, serve as important indicators of ecosystem health. Assessing the abundance and habitat use of such marine top predators is essential for the formulation of effective conservation and management actions. There is considerable concern over the viability of small humpback dolphin opulations across a global scale and a number of studies have raised concerns over their vulnerability to extinction. In light of the recent uplisting of Indian Ocean humpback dolphins (Sousa plumbea) to ‘Endangered’ on the South African Red Data list, there is an urgent need for a greater understanding of the abundance and spatial distribution of this species along the South African coastline. Using small vessels as survey platforms between March 2014 and June 2015, this study attempted to determine the abundance, spatial distribution and habitat preferences of Indian Ocean humpback dolphins along 150 km of South Africa’s south coast. A further aim was to assess the utilisation of the current Marine Protected Area network by humpback dolphins along this coastline relative to areas outside of formal protection. Mark-recapture methods applied to photo-identification data produced abundance estimates of 84 individuals (95% CI: 72-115) within the study area for both open and closed models. An average group size of 3.94 individuals (range 1-12; SD = ± 2.82) was observed during the study, indicating a decrease in average group size of ~45 % from a previous assessment in 2002/03. Such a decline in group size could potentially be a result of a change in social structure in response to reduced prey availability. Spatial analyses of humpback dolphin geographic positions, using a kernel density estimator (KDE) and effort-weighted density grid analyses, indicate that the species is unevenly distributed over the coastal zone within the area. Sightings occurred at the highest densities within Buffels Bay and along Goukamma MPA, followed by Plettenberg Bay, Nature’s Valley, and around the Bloukrans, Elandsbos and Groot River East mouths. Habitat preference was assessed using a standard classification-based method and the results indicate a strong preference, in particular, for Dissipative Intermediate Sandy Coast habitat, followed by Very Exposed Rocky Coast, Intermediate Sandy Coast, Estuarine Shore, Mixed Shore and Inshore Reef habitats. Areas of high humpback dolphin densities appear to be associated with these habitat types, especially with Dissipative-Intermediate Sandy Coast habitat. Humpback dolphins were sighted at relatively low densities along stretches of coastline consisting predominately of Exposed Rocky Shore habitat. Long expanses of this habitat type may limit humpback dolphin movements along the coast. The observed patterns in distribution and habitat preferences may be linked to the availability of prey and/or the avoidance of predators. Average sightings per kilometer travelled (SPUE) indicate that the utilisation of the Robberg and Tsitsikamma MPAs by humpback dolphins was low, most likely due to the low availability of sandy coastline in these areas. In contrast, the utilisation of the Goukamma MPA, which is characterised by a high availability of Dissipative-Intermediate Sandy Coast, was very high. The low population numbers and declines in average group size of Indian Ocean humpback dolphins within the study area warrant concern and call for effective conservation and management measures. In light of ever-increasing levels of anthropogenic threats to coastal areas, future research and long-term monitoring of the population is essential to broaden our knowledge of the species and to detect population trends.
14

Análise de viabilidade financeira para obtenção de créditos de carbono em projetos de eficiência energética. / Analysis of financial viability to obtain carbon credits in energy efficiency projects.

Gedra, Ricardo Luís 07 May 2009 (has links)
O presente trabalho tem por objetivo analisar a viabilidade financeira para obtenção de créditos de carbono em projetos de eficiência energética, por meio dos indicadores financeiros Valor Presente Líquido (VPL) e Taxa Interna de Retorno (TIR). A partir do desenvolvimento de uma modelagem analítica composta de despesas e receitas existentes em um determinado horizonte de tempo, obtém-se o fluxo caixa resultante do projeto, sobre o qual é calculado o VPL e a TIR em diferentes cenários de receitas advindas da venda dos créditos de carbono. Desta forma, pretende-se apresentar em quais condições a obtenção dos créditos de carbono aumenta o desempenho financeiro de um projeto de eficiência energética e em quais condições este desempenho é reduzido. / The present work has for objective to analyze the financial viability to obtain carbon credits in energy efficiency projects, through the financial indicators Net Present Value (NPV) and Internal Rate of Return (IRR). From the development of an analytical model composed of existing expenditure and revenue in a defined period of time, the cash flow resulting from the project is obtained, which is calculated on the NPV and IRR at different scenarios of revenue resulting from carbon credits. In such a way, it is intended to present in which conditions to obtain the carbon credits grow up the financial performance of a energy efficiency project and in which conditions this performance is reduced.
15

A comparison of body proportions in juvenile sea turtles: how shape may optimize survival in a vulnerable life stage

Unknown Date (has links)
Marine turtles produce many offspring which offsets the high mortality experienced by turtles during early development. Juvenile mortality might be reduced by evolving effective behavioral as well as morphological anti-predator defenses. Body proportions of three species (Caretta caretta, Chelonia mydas, Dermochelys coriacea) of turtles were measured in the first fourteen weeks of development to examine how growth may mitigate predation by gape-limited predators. Growth was categorized as isometric if shape did not change during development or allometric if body shape did change. All three species showed allometric growth in carapace width; however it was less pronounced in the larger D. coriacea turtles. Allometric growth in carapace width decreased as all three species grew in size. When high predation occurs in early development, many species will favor rapid growth into a size refuge. Juvenile sea turtles may optimize their survival by growing allometrically when predation risk is the greatest. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
16

Viabilidade Populacional de Sotalia guianensis (van BÉNÉDEN, 1864) (Cetacea, Delphinidae) no Complexo Estuarino-Lagunar de Cananéia, Estado de São Paulo / Population viability of Sotalia guianensis (van BÉNÉDEN, 1864) (Cetacea, Delphinidae) in the Estuarine-Lagoon Complex of Cananéia, São Paulo State

Almeida, Inaê Guion de 06 October 2014 (has links)
Sotalia guianensis é um pequeno cetáceo costeiro encontrado ao longo do Oceano Atlântico Sul-Ocidental. Está exposta a inúmeras ameaças, tais como captura acidental em redes de pesca, tráfego de embarcações e turismo. A análise de viabilidade populacional (AVP) é uma forma de prever as flutuações e a probabilidade de persistência ou extinção de uma espécie ou população ao longo do tempo, incorporando dados demográficos, ecológicos e ambientais de populações reais em simulações computacionais de modelos estocásticos e determinísticos. O presente estudo teve como objetivos estimar densidade, abundância e realizar uma AVP para S. guianensis no Complexo Estuarino-Lagunar de Cananéia, São Paulo. Estimativas de abundância e densidade foram obtidas entre 2011 e 2012, utilizando o método de transecção linear com amostragem de distâncias, com 1.339,91 km percorridos e 83h05min em esforço. Avistou-se 241 grupos, compostos por 1 a 20 indivíduos. O programa Distance, com modelo half-normal e ajuste coseno e menor valor de AIC, estimou uma abundância de 193 indivíduos (95%IC: 158 - 237) e densidade de 2,5538 ind/km2 (95%IC: 2,0812 - 3,1337). A média de tamanho de grupo é 4,1504 indivíduos (95%IC: 3,7666 - 4,5734). De forma geral, a espécie apresenta grandes variações ao longo de sua distribuição com relação ao tamanho populacional, densidade, tamanho de grupos, distribuição nos habitats e residência. Tais diferenças estão associadas possivelmente às características físicas e ambientais de cada habitat, que interferem direta ou indiretamente na distribuição e dinâmica populacional da espécie e suas presas. Para a AVP a população foi tratada como não suplementada, sem dispersão, sem remoção, sem depressão endogâmica e a extinção foi definida como a permanência de apenas um sexo. O valor inicial da população é 193 indivíduos e demais parâmetros demográficos e reprodutivos foram estimados com base na literatura disponível. Variações de parâmetros específicos (mortalidade, capacidade de suporte do ambiente (K), variação ambiental na reprodução e catástrofe) foram inseridas nos cenários para avaliar as tendências populacionais sob diferentes ameças. Utilizou-se o programa VORTEX 9.99b. A AVP apontou para o declínio e extinção (P(E) = 1,000) da população em menos de 300 anos em todos os cenários, com taxas de crescimento de -0,082 (SD = 0,120), - 0,049 (SD = 0,107) e -0,086 (SD = 0,062), para os cenários 1, 2 e 3 respectivamente. O tempo médio para extinção foi estimado em 39,6 anos para o cenário 1, 57,3 anos para o cenário 2 e 3,3 anos para o cenário 3. As projeções geradas pela AVP apontaram cenários pessimistas, o que pode estar relacionado ao pequeno tamanho da população. As análises mostram que variações no tamanho populacional, mortalidade, K e catástrofes podem influenciar fortemente a persistência de pequenas populações. O estuário de Cananéia é um ambiente favorável e bem preservado que oferece recursos suficientes para S. guianensis, entretanto, o aumento das atividades antrópicas na área pode levar a mudanças na dinâmica populacional e alterações no habitat, comprometendo sua persistência ao longo do tempo. / Sotalia guianensis is a small coastal cetacean found along the south-western Atlantic Ocean. Through its range, is exposed to numerous threats, such as bycatch in fishing nets, vessel traffic and tourism. Population viability analysis (PVA) is a way to predict the trends and the probability of persistence or extinction of a species or population over time, incorporating demographic, ecological and environmental data of real populations in computer simulations of stochastic and deterministic models. The present study aimed to estimate density, abundance and population viability of S. guianensis in the estuarine-lagoon complex. Estimates of abundance and density were obtained between 2011 and 2012, using the distance sampling method and linear transects, with 1,339 .91 km and 83h05min in effort. It were recorded 241 groups (n) with group size between 1 to 20 individuals. The Distance program, with half-normal model and adjust cosine with the lowest AIC, estimated an abundance of 193 individuals (95% CI: 158-237) and density of 2.5538 ind/km2 (95% CI: 2.0812 - 3.1337). The average group size is 4.1504 individuals (95% IC: 3.7666-4.5734). In general, the species presents large variations throughout its distribution regarding population size, density, groups size, distribution in habitat and residence. Such differences are possibly associated with the physical characteristics of each habitat and environmental conditions that interfere directly or indirectly in the distribution and population dynamics of the species and its prey. For the PVA population was treated as not supplemented, without dispersion, without removal, without inbreeding depression, and extinction was defined as the presence of only one sex. The initial population size was 193 individuals and other demographic and reproductive parameters were estimated based on available literature for the species. Variations of specific parameters (mortality, carrying capacity of the environment, environmental variation on reproduction and catastrophe) were used to evaluate population trends under different threats and scenarios. It was used the VORTEX program v. 9.99 b. AVP pointed to the decline and extinction (P(E) = 1,000) of the population in less than 300 years in all scenarios, with growth rates of -0.082 (SD = 0.120), -0.049 (SD = 0.107) and - 0.086 (SD = 0.062), for scenarios 1, 2 and 3 respectively. The average time to extinction was estimated at 39.6 years for scenario 1, 57.3 years for scenario 2 and 3.3 years for scenario 3. The projections generated by the AVP showed pessimistic scenarios, which may be related to the small size of the population. The analyses show that variations in population size, mortality, carrying capacity and disasters can strongly influence the persistence of small populations. Cananéia estuary is a well preserved environment that offers sufficient resources to S. guianensis, however, the increase in anthropogenic activities in the estuary may lead to changes in population dynamics and habitat quality, compromising their persistence over time.
17

Population viability analysis for plants : practical recommendations and applications

Ramula, Satu January 2006 (has links)
<p>Population viability analysis (PVA) is commonly used in conservation biology to predict population viability in terms of population growth rate and risk of extinction. However, large data requirements limit the use of PVA for many rare and threatened species. This thesis examines the possibility of conducting a matrix model-based PVA for plants with limited data and provides some practical recommendations for reducing the amount of work required. Moreover, the thesis applies different forms of matrix population models to species with different life histories. Matrix manipulations on 37 plant species revealed that the amount of demographic data required can often be reduced using a smaller matrix dimensionality. Given that an individual’s fitness is affected by plant density, linear matrix models are unlikely to predict population dynamics correctly. Estimates of population size of the herb <i>Melampyrum sylvaticum</i> were sensitive to the strength of density dependence operating at different life stages, suggesting that in addition to identifying density-dependent life stages, it is important to estimate the strength of density dependence precisely. When a small number of matrices are available for stochastic matrix population models, the precision of population estimates may depend on the stochastic method used. To optimize the precision of population estimates and the amount of calculation effort in stochastic matrix models, selection of matrices and Tuljapurkar’s approximation are preferable methods to assess population viability. Overall, these results emphasize that in a matrix model-based PVA, the selection of a stage classification and a model is essential because both factors significantly affect the amount of data required as well as the precision of population estimates. By integrating population dynamics into different environmental and genetic factors, matrix population models may be used more effectively in conservation biology and ecology in the future.</p>
18

Population viability analysis for plants : practical recommendations and applications

Ramula, Satu January 2006 (has links)
Population viability analysis (PVA) is commonly used in conservation biology to predict population viability in terms of population growth rate and risk of extinction. However, large data requirements limit the use of PVA for many rare and threatened species. This thesis examines the possibility of conducting a matrix model-based PVA for plants with limited data and provides some practical recommendations for reducing the amount of work required. Moreover, the thesis applies different forms of matrix population models to species with different life histories. Matrix manipulations on 37 plant species revealed that the amount of demographic data required can often be reduced using a smaller matrix dimensionality. Given that an individual’s fitness is affected by plant density, linear matrix models are unlikely to predict population dynamics correctly. Estimates of population size of the herb Melampyrum sylvaticum were sensitive to the strength of density dependence operating at different life stages, suggesting that in addition to identifying density-dependent life stages, it is important to estimate the strength of density dependence precisely. When a small number of matrices are available for stochastic matrix population models, the precision of population estimates may depend on the stochastic method used. To optimize the precision of population estimates and the amount of calculation effort in stochastic matrix models, selection of matrices and Tuljapurkar’s approximation are preferable methods to assess population viability. Overall, these results emphasize that in a matrix model-based PVA, the selection of a stage classification and a model is essential because both factors significantly affect the amount of data required as well as the precision of population estimates. By integrating population dynamics into different environmental and genetic factors, matrix population models may be used more effectively in conservation biology and ecology in the future.
19

Study Of Effects Of Selective Hunting On A Bear Population Through Pva Simulation

Agzitemiz, Mehmet Melih 01 October 2008 (has links) (PDF)
Management of big wildlife such as bears can be a difficult task, especially in the face of human-wildlife conflict and demands of the hunting industry. The Brown Bear (Ursus arctos) population at Yusufeli County (Artvin, northeastern Turkey) has recently been the focus of scientific, social and economic concerns. This study population of c. 140 individuals occurs within 800 km2 of forested and alpine land. Legal hunting of male bears was allowed in 2007 after an interval of four years. This study aims to find out through a population viability analysis the level and frequency of trophy hunting this population can tolerate for the next 50 years. A matrix model with six age-classes for each sex was constructed using observed and literature-based parameter values. RAMAS Metapop was used to simulate four different scenarios where numbers of hunted bears and hunting frequency changes. The model was highly sensitive to maximum growth rate and adult survival. Interval extinction probabilities for the next 50 years ranged between 0% and 26% depending on the scenario. Viable scenarios (with an extinction probability &lt / 0.05) were only possible with either no trophy hunting or hunting of 4 subadult/adult males and 1 adult female every other year. Legal and illegal hunting jointly impact the bear population in a strong way, and when they occur simultaneously every year, they lead to extinction in the long run. Avoidance of illegal killing and a close supervision of trophy hunting are crucial in the management of this bear population.
20

Identification Of Demographic Structure And Population Viability Analysis Of Gazella Subgutturosa In Sanliurfa

Cobanoglu, Aziz Emre 01 February 2010 (has links) (PDF)
Goitered gazelle (Gazella subgutturosa) is an Asian antelope species and it is classified as Vulnerable by IUCN. They have an economic, esthetic and cultural value / therefore, they had been hunted and domesticated for a long time. Additional human disturbance over years nearly led goitered gazelle populations in Turkey to extinction. Today in Turkey, only natural population of goitered gazelle lives in Sanlurfa. In this theses, demographic structure and population parameters of natural population goitered gazelle in Sanliurfa is studied. Line transect and regular surveys are performed to collect data about demographic structure of the population such as sex ratio and group composition. Line transect sampling, which is a distance sampling technique, is used to estimate population size and density of the population. GPS collared goitered gazelles are monitored for fecundity and survival rate. Data is collected for 18 from July 2008 to December 2009 during 32 field surveys. Four main transect samplings have been performed and including transect samplings that are done during regular surveys, 90 line transects are walked. Population sizes and densities were estimated to be (average &plusmn / standard error) 242 &plusmn / 184 and 2.302 &plusmn / 1.590 individual per km2 for July 2008 / 365 &plusmn / 179 and 3.476 &plusmn / 1.707 individual per km2 for January 2009 / 319 &plusmn / 111 and 3.039 &plusmn / 1.059 individual per km2 for June 2009 and lastly, 317 &plusmn / 243 and 3.019 &plusmn / 2.315 for November 2009. Survival rate is estimated to be 0.276, 0.540 and 0.585 for calves, 1 year old and 2+ years olds respectivelty, and fecundity is estimated to be 0.4. This preliminary study shows that according to Population Viability Analysis results, natural goitered gazelle population in Turkey will be extinct in next 10 years if more effective conservation is not performed.

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