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Дмитренко, Алла Олександрівна, Алла Александровна Дмитренко, and Alla Oleksandrivna Dmytrenko. "Keystones for attainment eco-efficiency of clean production." Thesis, Видавництво СумДУ, 2008. http://essuir.sumdu.edu.ua/handle/123456789/8141.
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The World Business Council for Sustainable Development guideline ‘reduce toxic dispersion’ is the weakest formulation of the seven and reflects the vigour with which some branches of the global industry have defended their products in spite of their prevalent unsafe for environment. Clean production is one way in which eco-efficiency has been put into effect. Yet the pressure to develop green chemicals and alternative non-toxic products has been intense and increasingly successful.
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Visser, Vernon. "Keystone megaherbivore hypothesis - white elephants?" Bachelor's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/26690.
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Pham, Truc T., and Michael J. Sieber. "Positive communications: the keystone of counterinsurgency strategy." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/38993.
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Approved for public release; distribution is unlimited.Over the last decade, the United States military has struggled to develop methodologies to assess success in its execution of counterinsurgency operations. By examining Zabul province, Afghanistan, this study offers a quantitative method to measure the effectiveness of positive communications that counterinsurgents conduct as part of their information strategy to mobilize public support for the incumbent government. We test the hypothesis that positive communications play a significant role in shaping popular attitudes and, when conducted by counterinsurgents, influence the population to support the government and deny safe haven for insurgents. Estimating a variety of regression models, we utilize high-resolution spatio-temporal data to isolate the casual effect of population engagements and radio broadcasts in relation to levels of insurgent violence over time and space. The evidence supports our prediction that positive communications conducted by counterinsurgents reduce insurgent violence.
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Hale, Sarah Luinda, and Sarah Luinda Hale. "Reestablishment of a Keystone Species: Initial Outcomes and Ecosystem Responses." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625853.
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The keystone species concept was introduced in 1969 in reference to top-down regulation of communities by predators, but has expanded to include myriad species at different trophic levels. Keystone species play disproportionately large, important roles in their ecosystems, but human-wildlife conflicts often drive population declines. A prominent example of anthropogenically driven keystone species decline is the prairie dog (Cynomys spp.) in North America. Prairie dogs were once widespread, but were considered pests and eradicated throughout much of the North American west; however, prairie dogs are keystone species that maintain the organization and diversity of their ecosystem, thus their removal can have a cascade of effects on the environment. Population declines have resulted in the necessity of keystone species reintroductions, however, studies of such reintroductions are rare. Managers have reintroduced prairie dogs as a grassland conservation tool, but often do not monitor populations intensively enough following reintroduction to accurately determine success. Furthermore, most studies of keystone species do not assess ecosystem-level effects of reestablishment. I studied four recently reestablished black-tailed prairie dog (Cynomys ludovicianus) colonies to determine if the reestablishment effort was successful, and if keystone roles were resumed after a prolonged absence. I found that two of three prairie dog populations monitored for demography grew, and three of four prairie dog colonies expanded in area. Furthermore, I found that reestablished black-tailed prairie dogs did not immediately influence small mammal diversity, richness, or abundance, but prairie dogs did resume their keystone role of regulating woody plant growth on colonies.
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Cochran-Yu, David Kyle. "A keystone of contention : the Earldom of Ross, 1215-1517." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7242/.
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The earldom of Ross was a dominant force in medieval Scotland. This was primarily due to its strategic importance as the northern gateway into the Hebrides to the west, and Caithness and Sutherland to the north. The power derived from the earldom’s strategic situation was enhanced by the status of its earls. From 1215 to 1372 the earldom was ruled by an uninterrupted MacTaggart comital dynasty which was able to capitalise on this longevity to establish itself as an indispensable authority in Scotland north of the Forth. By the fifteenth century the earldom had passed to an equally powerful dynasty, the MacDonald lords of the Isles, and became a part of one of the most powerful regional hegemonies of medieval Scotland. The earldom and the power of its earls are acknowledged by most scholars, yet it remains a relatively under-analysed subject, as scholarship tends to gravitate towards viewing Ross through the MacDonald lordship of the Isles, or through the Scottish kings. This has led to Ross being treated as a secondary subject. Moreover, little has been done to compare the two principal dynasties that ruled the earldom and explore issues of continuity between the two. This thesis will study Ross through the comital dynasties that ruled it and the important local magnates within it, and will provide a Ross-centred platform from which to analyse the political development of the earldom. The thesis will also address issues of continuity, beginning with the origins of the Mac ant t-sagairt earldom and trace its political evolution until the MacDonald claim to Ross was finally extinguished in the early sixteenth century. This thesis will be the first long duree study of this Scottish earldom, and will increase our understanding of Ross and its earls who were so vital to Scotland’s medieval history.
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Carabello, Damian Anthony. "Koz-ez's of good intention An analysis of the effectiveness, outcomes, & legislative intent of Pennsylvania's keystone opportunity zone & expansion zone programs /." Instructions for remote access, 2009. http://www.kutztown.edu/library/services/remote_access.asp.
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Thesis (M.P.A.)--Kutztown University of Pennsylvania, 2009.Source: Masters Abstracts International, Volume: 47-05, page: 2639. Adviser: Paula A. Holoviak. Includes supplementary digital materials.
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Hitchman, Sean M. "A mosaic approach can advance the understanding and conservation of native biodiversity in natural and fragmented riverscapes." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38559.
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Doctor of PhilosophyDivision of Biology
Martha E. Mather
Understanding the complex relationship between organismal distribution and spatial heterogeneity is central to many ecological questions. This challenge of identifying the biodiversity consequences of spatial patterns is especially critical for resource conservation at the larger riverscape scale because climate- and human-related impacts often act through intricate and spatially-connected organismal-habitat relationships. Specifically, resource managers cannot manage the adverse effects of common disturbances on aquatic ecosystems (e.g. water-withdrawal, dams, urbanization) if the influence of spatial heterogeneity is not recognized and understood. Towards this larger goal, I examined the role of spatial heterogeneity on stream fish biodiversity in the Upper Neosho River, KS in three ways. First, I used a mosaic approach (in which connected, interacting collections of juxtaposed habitat patches were examined) to build the scientific foundation for a general model that aids in the understanding and environmental management of disturbance-related, ecologically-based conservation problems. Second, I examined landscape metrics to quantify the impact of low-head dams on stream habitat and fish diversity. Third, I evaluated multiple quantitative approaches to develop a fuller understanding of how the arrangement of habitats across the riverscape influenced stream fish biodiversity. Related to these questions, the dissertation research provided four key take-home messages that advanced science-based conservation related to stream fish habitat and biodiversity. First, mapping larger-scale patterns of heterogeneity showed that quantitatively-different, physically-distinct pool, riffle, run, and glide habitats were arranged in unique combinations created diverse habitat mosaics across sites. Second, riffles, which comprised < 5% of all habitat patches, acted as keystone habitats that disproportionately increased fish biodiversity (i.e., species richness was significantly higher in mosaics with higher numbers of riffles). Third, mosaic approach metrics provided new insights into the influence of low-head dams on stream fish biodiversity that were not detected with traditional approaches to habitat sampling and statistical analysis. For example, low-head dams dampened the natural habitat diversity that is needed for the maintenance of resilient communities. Furthermore, using path analysis, I found that species richness was higher immediately below low-head dams as mediated through an increase in the proportion of riffle habitat, but this higher species richness was offset by a greater decrease in species richness in the impoundment habitat above low-head dams. Thus, the choice of scale influenced the interpretation of how dams affected habitat heterogeneity and resultant organismal patterns. Finally, landscape approaches to examining compositional and configurational heterogeneity provided new insights about stream fish habitat-biodiversity relationships. For example, riffle patch density had a positive effect on species richness, species richness was higher within shallow, slow flowing riffles, and adjacent neighbor habitats affected riffle species richness as mediated through alterations to within-habitat characteristics. In summary, quantifying the complex patterns of spatial heterogeneity in a range of ways can aid in the understanding of habitat-biodiversity patterns and help conserve stream fishes at a variety of scales.
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Netzer, Gilbert. "Efficient LU Factorization for Texas Instruments Keystone Architecture Digital Signal Processors." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-170445.
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The energy consumption of large-scale high-performance computer (HPC) systems has become one of the foremost concerns of both data-center operators and computer manufacturers. This has renewed interest in alternative computer architectures that could offer substantially better energy-efficiency.Yet, the for the evaluation of the potential of these architectures necessary well-optimized implementations of typical HPC benchmarks are often not available for these for the HPC industry novel architectures. The in this work presented LU factorization benchmark implementation aims to provide such a high-quality tool for the HPC industry standard high-performance LINPACK benchmark (HPL) for the eight-core Texas Instruments TMS320C6678 digitalsignal processor (DSP). The presented implementation could perform the LU factorization at up to 30.9 GF/s at 1.25 GHz core clock frequency by using all the eight DSP cores of the System-on-Chip (SoC). This is 77% of the attainable peak double-precision floating-point performance of the DSP, a level of efficiency that is comparable to the efficiency expected on traditional x86-based processor architectures. A presented detailed performance analysis shows that this is largely due to the optimized implementation of the embedded generalized matrix-matrix multiplication (GEMM). For this operation, the on-chip direct memory access (DMA) engines were used to transfer the necessary data from the external DDR3 memory to the core-private and shared scratchpad memory. This allowed to overlap the data transfer with computations on the DSP cores. The computations were in turn optimized by using software pipeline techniques and were partly implemented in assembly language. With these optimization the performance of the matrix multiplication reached up to 95% of attainable peak performance. A detailed description of these two key optimization techniques and their application to the LU factorization is included. Using a specially instrumented Advantech TMDXEVM6678L evaluation module, described in detail in related work, allowed to measure the SoC’s energy efficiency of up to 2.92 GF/J while executing the presented benchmark. Results from the verification of the benchmark execution using standard HPL correctness checks and an uncertainty analysis of the experimentally gathered data are also presented.Energiförbrukningen av storskaliga högpresterande datorsystem (HPC) har blivit ett av de främsta problemen för såväl ägare av dessa system som datortillverkare. Det har lett till ett förnyat intresse för alternativa datorarkitekturer som kan vara betydligt mer effektiva ur energiförbrukningssynpunkt. För detaljerade analyser av prestanda och energiförbrukning av dessa för HPC-industrin nya arkitekturer krävs väloptimerade implementationer av standard HPC-bänkmärkningsproblem. Syftet med detta examensarbete är att tillhandhålla ett sådant högkvalitativt verktyg i form av en implementation av ett bänkmärkesprogram för LU-faktorisering för den åttakärniga digitala signalprocessorn (DSP) TMS320C6678 från Texas Instruments. Bänkmärkningsproblemet är samma som för det inom HPC-industrin välkända bänkmärket “high-performance LINPACK” (HPL). Den här presenterade implementationen nådde upp till en prestanda av 30,9 GF/s vid 1,25 GHz klockfrekvens genom att samtidigt använda alla åtta kärnor i DSP:n. Detta motsvarar 77% av den teoretiskt uppnåbara prestandan, vilket är jämförbart med förväntningar på effektivteten av mer traditionella x86-baserade system. En detaljerad prestandaanalys visar att detta tillstor del uppnås genom den högoptimerade implementationen av den ingående matris-matris-multiplikationen. Användandet av specialiserade “direct memory access” (DMA) hårdvaruenheter för kopieringen av data mellan det externa DDR3 minnet och det interna kärn-privata och delade arbetsminnet tillät att överlappa dessa operationer med beräkningar. Optimerade mjukvaruimplementationer av dessa beräkningar, delvis utförda i maskinspåk, tillät att utföra matris-multiplikationen med upp till 95% av den teoretiskt nåbara prestandan. I rapporten ges en detaljerad beskrivning av dessa två nyckeltekniker. Energiförbrukningen vid exekvering av det implementerade bänkmärket kunde med hjälp av en för ändamålet anpassad Advantech TMDXEVM6678L evalueringsmodul bestämmas till maximalt 2,92 GF/J. Resultat från verifikationen av bänkmärkesimplementationen och en uppskattning av mätosäkerheten vid de experimentella mätningarna presenteras också.
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Catano, Christopher. "Species and habitat interactions of the gopher tortoise: A keystone species?" Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5153.
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Species-species and species-habitat interactions have been demonstrated to be important in influencing diversity across a variety of ecosystems. Despite generalities in the importance of these interactions, appropriate mechanisms to explain them are absent in many systems. In sandhill systems of the southeast U.S., gopher tortoises have been hypothesized to be a crucial species in the maintenance of diversity and function. However, the mechanisms and magnitude in which they influence their communities and habitats have rarely been empirically quantified. I examined how habitat structure influences tortoise abandonment of burrows and how tortoise densities influence non-volant vertebrate community diversity. Tortoise burrow abandonment is directly influenced by canopy closure, with each percent increase in canopy cover relating to a ~2% increase in the probability of burrow abandonment. In addition, tortoise burrow density was positively correlated with diversity and evenness, but not species richness. This influence was directly proportional to burrow density, supporting a dominance role for this species and rejecting the commonly asserted keystone species mechanism. I also quantified the influence of tortoises in influencing diversity relative to other environmental and habitat variables. Through this research, I have demonstrated that disturbance and habitat structure are important, but diversity responds most to density of burrows in the habitat. These findings demonstrate the intricate relationships interacting to maintaining diversity in sandhill systems. In particular, habitat change leading to declines of gopher tortoises may have drastic negative impacts on vertebrate species diversity.M.S.
Masters
Biology
Sciences
Biology
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Montenegro, Olga Lucia. "Natural licks as keystone resources for wildlife and people in Amazonia." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008440.
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Gleason, Leigh. "Canvassed and delivered : direct selling at Keystone View Company, 1898-1910." Thesis, De Montfort University, 2018. http://hdl.handle.net/2086/16270.
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This thesis addresses an under-studied aspect of the stereoscopic photograph industry: the business and sales practices employed by American stereograph publishers at the dawn of the twentieth century, as exemplified by Keystone View Company. Stereographic sales practices are an essential element in understanding stereoscopy’s ubiquity and place in American culture, but have been too frequently oversimplified or wholly overlooked in existing scholarship. Using concepts from business history, this thesis addresses the ways in which Keystone’s structure and scale allowed it to function as a national and international entity, and examines the role of communication in the sale of photographs. Keystone’s success hinged on the corporate communications between the company and its direct-selling sales agents, communication between sales agents and prospective consumers, and the communication between consumers and the company (both tacitly through purchase and directly through written praise of the products). Furthermore, this thesis considers the affective qualities and social claims of stereoscopy by proposing the role of aspiration as a motivating factor in the images’ consumption. Aspiration was woven into the company’s prescribed sales pitch, the character of the sales agents employed by Keystone, and in recommendations and testimonials from Keystone users. Consumers’ emotional response to stereography, and especially the way that stereography was sold, served as a significant influence in the sales process. Successful sales were Keystone’s motivation, and its business practices propelled the company’s success, especially through corporate communication and framing stereographs aspirationally. This thesis concludes that the role of business practices in stereoscopic production contributes to the understanding of the cultural phenomenon of stereoscopy, and permits a more complete sense of the market in which these photographs circulated.
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Haussmann, Natalie Suzette. "The biogeomorphology associated with a keystone plant species in the sub-Antarctic." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6909.
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Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2011.AFRIKAANSE OPSOMMING: Min aandag is al gegee aan biogeomorfologiese interaksies in glasiale en periglasiale omgewings. Nietemin is hierdie interaksies, wat op die skeidingsvlak tussen ekologie en geomorfologie fokus, baie belangrik in hierdie omgewings, waar organismes in noue verband met die abiotiese omgewing saamleef. In hierdie tesis bestudeer ek die interaksies tussen die vaskulêre plantspesies met die hoogste voorkoms op sub-Antarktiese Marion Eiland, Azorella selago Hook. (Apiaceae), en die omringende geomorfologiese landskapsvorme, -prosesse en meettegnieke. Verder verskaf die tesis voorstelle om toekomstige geïntegreerde biogeomorfologiese navorsing te vergemaklik. Om die gevolge van A. selago-plante vir sedimentbeweging en -verspreiding te verstaan, het ek die verspreiding van sedimentgroottes om hierdie plante gemeet deur middel van 'n kombinasie van fotografiese analise-metodes. Deur as sedimentbewegingsobstruksies te dien, het plante 'n waarneembare effek op die omringende sedimentverdeling. Dit is veral belangrik om hierdie interaksies tussen A. selago en sy omgewing te verstaan in die lig van onlangse klimaatsverandering op die eiland, omdat sedimentgrootte belangrike grondeienskappe soos waterretensiekapasiteit en vriesgevoeligheid beïnvloed. Om die effek wat A. selago plante op die omringende mikroklimaat het beter te verstaan, is die kleinskaalse variabiliteit in grondtemperature om A. selago plante bestudeer. Grootskaalse grondligting as gevolg van fors is gemeet, ten spyte van relatief ligte forseienskappe. Dit dui daarop dat naaldys ook by temperature bo -2°C kan vorm. Wintergrondtemperature aan die oostekant van plante was effens laer en minder veranderlik as aan die westekant van plante, waarskynlik as gevolg van laer windsnelhede en/of sneeu wat ophoop aan die oostelike, lykant van plante. Die resultate benadruk dat A. selago plante 'n belangrike rol speel in die verandering van mikroklimate en dat dit belangrik is om die gevolge van sulke veranderings, soos die skep van mikrohabitatte vir grondorganismes, te verstaan. Daar word vermoed dat positiewe plantinteraksies negatiewe interaksies oorheers in omgewings met hoe abiotiese druk. Gevolglik wys ek dat daar 'n positiewe verband bestaan tussen A. selago plante en saailinge van beide A. selago self, asook van die meerjarige gras Agrostis magellanica Lam. (Poaceae). Ek stel voor dat beide plante en klippe sade, wat deur wind, reenval en/of afdraande sedimenttransportering as gevolg van vriesprosesse vervoer word, opvang. Verder dui verhoogde A. selago saailinggetalle om plante, maar nie om klippe nie, daarop dat plante een of ander biologiese voordeel aan A. selago saailinge bied. Dit is bekend dat die verspreidingspatrone van plantspesies as gevolg van abiotiese stresgradiente varieër. Met hierdie bevinding in gedagte, is moontlike faktore verantwoordelik vir A. selago saailinggetalle en -verspreidingspatrone, soos hoogte bo seespieël en substraatbedekking, bestudeer. Alhoewel dit wil voorkom asof daar 'n verband tussen saailinggetalle en hoogte bo seespieël is, is saailinggetalle en verpreidings meestal afhanklik van ongemeette perseel-spesifieke eienskappe. Plante kan die omringende geomorfologie beïnvloed, maar ook geomorfologiese meettegnieke. Om die potensiaal van kosmogeniese dateringsmetodes as geomorfologiese hulpmiddels in fellfield habitatte te verken, is die akkumulasietempo van die kosmogeniese isotoop ¹ºBe onder en langs 'n A. selago plant bepaal. Die resultate dui daarop dat ¹ºBe nie ten volle in die grondprofiel behoue bly nie en verskeie potensiële redes word bespreek. Verder dui die resultate daarop dat ¹ºBe konsentrasies in fellfield habitatte versigtig geïnterpreteer moet word, aangesien A. selago plante effektief ¹ºBe opvang in hulle grondryke kern. Om vordering in biogeomorfologie te vergemaklik, is dit belangrik om bewus te wees van die verskillende metodes wat geomorfoloë en ekoloë volg. Ekologiese benaderings is dikwels op strenger statistiese tegnieke gebaseer, terwyl geomorfoloë eerder fokus op 'n meer beskrywende benadering en teoretiese beredenering. Ek verduidelik hoekom die twee velde sulke uiteenlopende benaderings volg, benadruk moontlike struikelblokke en verskaf voorstelle om samewerking te vergemaklik.
ENGLISH ABSTRACT: There are few scientific publications that relate to biogeomorphological interactions in glacial and periglacial environments. Interactions that focus on the interface between ecology and geomorphology are very important in these environments, as a tight coupling often exists between organisms and their abiotic surroundings. In this thesis the interactions between the dominant vascular cushion plant species on sub-Antarctic Marion Island, Azorella selago Hook. (Apiaceae), and the surrounding geomorphological landforms, processes and measuring techniques were studied. In addition, the thesis provides suggestions to facilitate future integrated biogeomorphological research. To understand the consequences of A. selago cushions for substrate movement and sorting, the grain size distribution of sediment surrounding these cushions was quantified using a combination of image analysis approaches. Through obstructing frost-related sediment transport, A. selago cushions are shown to affect the grain size sorting of the surrounding sediment. Particle size affects soil properties such as water-holding capacity and frost susceptibility. It is therefore important to understand the interactions between A. selago cushions and sediment distributions, especially in the light of recent warming and drying on the island. Fine scale variability in soil temperature parameters was studied around cushions to improve understanding on how A. selago affects the surrounding soil microclimate. Despite the mild frost climate, extensive frost heave occurred in the study area, indicating that needle ice forms above the previously suggested required temperature of -2°C. Lower and less variable winter temperatures were found on eastern than on western cushion sides, probably as a result of lower wind speeds or leeside snow accumulation on eastern cushion sides. These research findings highlight the importance of A. selago cushions in modifying site microclimates. Such modifications could have important potential consequences, such as providing microhabitats for soil microorganisms and seedlings. Positive plant interactions have been suggested to dominate over negative interactions in environments with high abiotic stress. Positive associations were found between A. selago and both its own seedlings and those of the perennial grass, Agrostis magellanica Lam. (Poaceae) on Marion Island. It is suggested that both cushions and rocks trap seeds dispersed by wind, runoff and/or downslope sediment transport through frost creep. In addition, increased A. selago seedling numbers around cushions, but not around rocks, suggest that cushions provide a biological nurse effect to seedlings of their own kind. Plant species' distributions have been known to vary in response to abiotic stress gradients. In light of this, determinants of A. selago seedling distributions and abundance, such as altitude and substrate cover, were explored. Although there appears to be some altitudinal trend, seedling distributions and abundance patterns were largely attributed to unaccounted variation between sites. Plants can affect the surrounding geomorphology, but also geomorphological measuring techniques. To explore the potential of cosmogenic dating techniques as geomorphological tools in fellfield habitats, accumulation rates of the cosmogenic isotope ¹ºBe were assessed underneath and adjacent to an A. selago cushion. The results show that ¹ºBe is not fully retained in the soil profile and various reasons are discussed. Furthermore, the results suggest that ¹ºBe concentrations should be interpreted cautiously in fellfield habitats, as A. selago cushions effectively intercept the isotope in their soil-rich core. To facilitate the integration of geomorphological and ecological principles, as was attempted in this thesis, it is important to understand the philosophies behind the different research approaches that ecologists and geomorphologists employ. Ecologists often employ a more statistics-based approach, whereas geomorphologists focus on a more descriptive approach and reasoning based on established theories. I attempt to explain why the two fields follow such different approaches, highlight some potential challenges and provide suggestions to facilitate progress in the interdisciplinary field of biogeomorphology.
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Cayias, Jennifer. "A Strategic Analysis of the Chechen Wars: The Keystone of Good Leadership." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339684125.
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Berg, Sofia. "Community Robustness Analysis : Theoretical Approaches to Identifying Keystone Structures in Ecological Communities." Doctoral thesis, Linköpings universitet, Teoretisk Biologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-88055.
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Most of the world’s ecosystems suffer from stress caused by human activities such as habitat destruction, fragmentation, overexploitation of species and climate change. These factors affect the reproduction and/or survival of individual species as well as interactions between species in ecological communities. Forthcoming effects of this are altered abundances, direct species loss, and indirect cascading extinctions, with yet largely unknown consequences on community structure and functioning. Today, biodiversity loss is of global concern since human society and welfare depend upon resources and services provided by ecosystems. The importance of considering entire ecological communities as a target for conservation and management has been increasingly recognized due to the interdependencie of species. Our ability to make predictions of the response of ecological communities to stress and biodiversity loss is in need of a deeper understanding of how structure and dynamical processes contributes to the functioning and stability of a community. In this thesis I use mathematical theory and dynamical models to study the response of community structure and resilience to a variety of disturbances affecting species and species interactions, ranging from small perturbations (Papers I-II) to large perturbations (species extinctions, Papers IIIIV). In Paper I we develop Community Sensitivity Analysis (CSA) as an analytical tool to study how a small permanent perturbation to the intrinsic growth rate, or mortality rate, of species is expected to affect i) the resilience (return rate) and ii) the structure (distribution of species equilibrium abundances) of an ecological community. Species interactions are described using Lotka-Volterra predator-prey dynamics. We apply CSA on the pelagic food webs of Lake Vättern and the Baltic Sea, respectively, and find that a change in the mortality rate of large-bodied species has a higher impact on community resilience and structure, compared to a perturbation to small-bodied species. However, analyzing the effect of a proportional change to the growth or mortality rate of species (elasticity analysis) shows that smallbodied species have proportionally larger effects on species equilibrium abundances, but not on resilience. CSA can also be used to study the effect of permanent (absolute or proportional) changes to inter- and intraspecific interaction strengths. For the two pelagic systems used in this study, CSA reveal that changes in the effect of a prey on its consumer tend to affect community structure and resilience significantly more than changes in the effect of a predator on its prey. In Paper II we assess the importance of rare species for the structure and resilience of ecological communities. First we show analytically, for a two species predator-prey system, that a change in the intrinsic growth rate of the rare species affect resilience more than a change in the growth rate of the common species. To test the generality of these results we next apply CSA on complex model food webs. In the analysis we distinguish between four trophic groups, each including only species with a similar trophic position, to separate the effect of abundance from the trophic position of species. Using mixed effect models we find support for our analytical predictions. More precisely, we find a strong negative relationship between the importance (sensitivity) of a species and its equilibrium abundance within all consumer groups and a weaker, but significant, relationship for producer species. The results from this study suggest that rare species can act as keystones through their effect on both community resilience and community structure, regardless of its trophic position. In Paper III we evaluate the risk of food web collapse caused by different trait-based extinction scenarios. In previous studies, groups of species, e.g. rare species, large-bodied species and top predators, have been identified to be relatively more prone to extinctions and other studies have found that extinctions of such species have comparably small effects on the remaining community. Using mathematical models of species dynamics we study the response of ecological communities to species removal (i.e. the proportion of species needed to be primarily removed to cause a 50% reduction in species richness, R50) when species are sequentially removed from the food web based on eight different traits. We show, contrary to some previous studies of sequential extinction simulations, that communities can be very vulnerable to realistic species loss. We furthermore find that the response of communities seems to depend on whether the extinction sequence follows a bottom-up or top-down direction, making it difficult to identify one particular extinction sequence as the most important/severe sequence. Finally, in Paper IV we aim to identify traits of species that can be used to identify keystone species, in terms of causing the highest proportion of secondary extinctions following their loss, in food webs with different degree of disassembly. Moreover, we analyze if the loss of a species that triggers a cascade of many secondary extinctions are the same species being identified as a keystones using Community Sensitivity Analysis. To answer these questions we randomly remove species from a set of 100 model communities. We analyze the relationship between the number of secondary extinctions following the randomly removed species and a range of species traits in communities where i) 75-100% of the initial number of species remain, ii) 50-75% of all species remain, iii) 25-50% of all species remain and iv) only 0-25% of all species remain. We find that the variation in secondary extinctions explained using species traits increases when the degree of food web disassembly and food web connectance are taken into account. The most important trait varies for different degrees of food web disassembly and also depends on whether basal species can go primarily extinct or not. However, due to correlation between most important traits, we conclude that the key status of different traits is rather robust against structural changes in the model food webs. Interestingly, food webs seem to be most sensitive to a random species loss after the loss of more than 25% of all initial species, suggesting that there is a threshold from which secondary extinctions increases. We also conclude that species being identified as keystones, based on the effect of their loss, are to some extent the same species being identified as having the largest effect on community structure and resilience, respectively, following a small perturbation.
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Wilder, Elisabeth. ""Game Over" for the Climate: The Keystone XL Pipeline on TV News." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1438.
Full textAbstract:
The overwhelming consensus of the world's climate scientists is that we must rapidly reduce our greenhouse emissions if we are to avoid catastrophic and irreversible climate change. Yet the proposed Keystone XL pipeline, which would carry tar sands oil that emits three to four times the carbon emissions of conventional gasoline across the U.S., is supported by a solid majority of Americans. This level of support for a project a proposal that would dramatically increase greenhouse gas emissions, pollute sensitive lands and water sources, and threaten the health and safety of communities along the way begs the question: what kind of information have Americans received about the pipeline?
Relying on theoretical perspectives developed by scholars who examine power structures, ideology, and the political economy of the mass media, I analyze 177 national network and cable news broadcasts in order to determine what kind of information leading media sources provide to the public about the Keystone XL pipeline proposal and the context in which this information is presented. Content analysis of broadcast transcripts reveals that television news stations exhibit biased coverage that encourages viewers to support pipeline construction. Furthermore, television news stations marginalize environmental and social concerns and disproportionately rely on business and government sources for information. Finally, the dominant frame employed by the news media is informed by neoliberal ideology and offers no challenge to the preferences of corporate and government elites--including the continued dominance of the fossil fuel industry. This type of coverage affords viewers a very limited basis for understanding the environmental and ultimately social threats posed by Keystone XL.
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Martins, Gustavo M. "Community structure and dynamics of the Azorean rocky intertidal : exploitation of keystone species." Thesis, University of Plymouth, 2009. http://hdl.handle.net/10026.1/1064.
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Experimental work has shown the importance of grazing by patellid limpets in structuring intertidal assemblages. Little is known, however, about the effects of a largescale and chronic removal of limpets. Here I investigate the ecology of Patella candei, a seldom-studied limpet endemic to Macaronesia, and how its long-term fishery impacts the Azorean rocky intertidal. The specific aims of this thesis are to: examine the processes that affect the distribution of limpets in the Azores at a range of spatial scales; investigate the role of grazing by P. candei in structuring the Azorean rocky intertidal and if its harvesting has impacted the dynamics and functioning of this ecosystem. The distribution of limpets was variable at a range of spatial scales. At the scale of islands, inter-island variation in harvesting intensity affected the abundance and size structure of populations of limpets as well as the balance between grazers, algae and barnacles. Stocks of limpets showed clear signs of exploitation and there was evidence that current legislation, including limpet protected zones, have been largely ineffective in protecting these populations. At smaller spatial scales, substratum micro-topography influenced the distribution and sui-vival of limpets. I also showed that the experimental provision of microhabitats could be used as a measure to mitigate the effects of coastal urbanisation, whilst promoting a local enhancement of the stocks of limpets. Overall my results provide evidence for the population and community level effects of limpet harvesting and show that limpet harvesting has a strong impact on the structure and fiinctioning of the Azorean rocky intertidal.
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Siegel, Eric Mitchell. "Reading the public comment : the keystone XL pipeline and future of environmental writing." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4754.
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In the lead up to the 2011 official U.S. State Department decision on the proposed Keystone XL pipeline--running from the Alberta, Canada Tar Sands to the Gulf of Mexico--the Department held nine public meetings in Fall 2011 in the six U.S. states through which the proposed Keystone XL pipeline project would pass (the Department rejected the proposal; however, a new proposal is under consideration as of this writing). The transcripts of these public meetings are publicly accessible.
Understanding the pipeline as a project of trans-national trade and the global circulation of petrochemicals--including global emissions of carbon dioxide--this paper hones in on one region within one U.S. state: the Nebraskan Sandhills, a cattle ranching region of grass-stabilized sand dunes and inter-dunal valleys stretching 20,000-square miles across the north-central part of the state, under which rests a vast hydrological network, including the largest freshwater aquifer in the world - the Ogallala Aquifer.
This essay argues that we can read the Public Comments as a form of poetic expression, paying attention to the ways the State Department transcription process formatted the oral testimonies into an "official" and sanctioned public document -- instituting line-breaks and other syntactical procedures. Using the tools of literary-critical analysis, this paper makes a case that we can read the Comments as a form of documentary poetry - in the tradition of such American modernist poets as Charles Reznikoff, Muriel Rukeyser, and George Oppen - that explore ecological questions while experimenting with lyric structures. The Comments reveal competing environmental stakeholders' stances - on such topics as Prairie systems ecology and the neoliberal economics of private-public capital markets. In doing so, they subsequently express citizens' various understandings of themselves in relation to landscape, ecology, technology, and geo-politics.
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Arnold, Paul. "The role of keystone species in driving microbial community diversity in U.K. lowland heaths." Thesis, University of Southampton, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580597.
Full textAbstract:
Myrmica ruginodis ants and the gorse species U. europaeus have a national distribution in the U.K. and are considered important keystone species within British lowland heaths. These two species boost and maintain biodiversity by increasing habitat heterogeneity through ecosystem engineering of the soil physical and chemical environment, and are generally considered Keystone species in lowland heaths. Both species have been shown to increase limiting nutrients in the soil such as Nitrogen and Phosphorus. Here, for the first time in a single study, the extent to which these species augment soil chemistry and the resulting impacts on microbial communities is quantified. It was hypothesized that abiotic changes brought about by the action of keystone species directly and indirectly will lead to differences in both bacterial and fungal community diversity and composition, and such changes will be likely to modify ecosystem function. Analysis of soil cores taken from three U.K. lowland heath habitats representing a national distribution found that dissimilarities in microbial community structure (determined by T-RFLP) were largely attributable to differences in soil pH. However, pH was an imperfect predictor. To fully understand abiotic drivers and to identify the soil nutrients involved in augmenting microbial communities in heathlands, a data mining exercise was conducted using the large Countryside Survey 2007 bacterial data. The findings from this showed that as the soil pH gradient was shortened by focusing on low soil pH, and then by looking at a single type of vegetation cover (dwarf shrub heath), soil pH became less effective in explaining differences in the communities; other soil chemical properties then become more important, such as Carbon to Nitrogen (C:N) ratio and soil Phosphorus (P). The identification of these chemical attributes and the known impacts that the keystone species have on them led to the development of a controlled mesocosm experiment using Aberdeenshire lowland heath soil. In this experiment keystone species were isolated and found to impact upon soil chemistry and microbial diversity. Soil pH was identified as having an important defining role on communities, however soil P and C:N and Potassium (K) were also related to microbial community composition. Differences in respiration were also linked to the presence of the keystone species. A final field experiment was performed to test the mesocosm observations in the field site, but sampling specific soil regions (ant nest structures and rhizospheres). Less marked microbial community differentiation was found compared with the initial field experiment. Fungi had no responses to soil chemistry except for Dorset communities which responded to soil pH. Bacteria responded to all soil measures of chemistry for pooled region data and for Aberdeenshire. Cumbria communities responded P and Dorset to C:N. Soil chemistry and microbial communities were not affected by the same keystone species in the same way in any of the regions. Finally, community T-RFLP profiles for fungi and bacteria were directly compared for.any correlation; interaction was found to be limited, partly due to fundamental differences in the bacterial 16S rDNA and fungal ITS rDNA T-RFLP profiles and partly due to these microbes responding in different ways to their environment.
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Moscato, Derek. "Plains Spoken: A Framing Analysis of Bold Nebraska's Campaign Against the Keystone XL Pipeline." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22780.
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This dissertation focuses on the use of strategic communication in the context of contemporary environmental activism. It examines the case of Bold Nebraska, a grassroots advocacy group opposing the construction of TransCanada’s Keystone XL oil pipeline in the state of Nebraska. Such an analysis of activist communication informs several areas of research, including public relations theory and practice, social movement theory, and environmental communication. To understand the construction of strategic communication within such activism, this study employs a movement framing analysis, a media framing analysis, and a rhetorical analysis. A quantitative framing analysis of Bold Nebraska’s website communication against the pipeline during the five-year period of 2011 to 2015 assesses how activists craft and project strategic messages. A framing analysis of Bold Nebraska’s national media coverage during the same timeframe highlights the relationship between activist framing and mainstream news coverage. Finally, a rhetorical analysis of Bold Nebraska’s 2014 Harvest the Hope concert is provided to understand the role of rhetorical appeals in building an environmental activism metanarrative or master frame.
Taken together, these three approaches provide both a more holistic means to considering environmental activism campaigns in the context of strategic communication, and fill in the gaps for understanding the interplay of social movement organizations, public relations, and persuasion. This study brings a framework of strategic advocacy framing to the realm of environmental politics, and builds upon this framework by considering the dynamic of populism in activism. It also explores the role of strategic communication in evolving a movement organization’s metanarrative as it toggles between short- and long-term goals. Finally, it identifies a civic environmental persuasion built upon the attributes of narrative, hyperlocalization, engagement, and bipartisanship in order to build broad support and influence public policy.
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Poluga, Sara Lindsay. "Rock Mass Characterization and Stability Evaluation of Mount Rushmore National Memorial, Keystone, South Dakota." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1498239487032982.
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Deaner, Larry Scott. "Home in the McDowell County Coalfields: The African-American Population of Keystone, West Virginia." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1089820789.
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Carroll, Matthew John. "The ecology of British upland peatlands : climate change, drainage, keystone insects and breeding birds." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3296/.
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Northern peatlands provide important ecosystem services and support species adapted to cold, wet conditions. However, drainage and climate change could cause peatlands to become drier, threatening ecosystem functions and biodiversity. British blanket bogs occur towards the southern extent of northern peatlands and have been extensively drained, so present an excellent opportunity to examine climate change and drainage impacts. Craneflies (Diptera: Tipulidae) are a major component of upland peatland invertebrate communities and provide a key food resource to breeding birds. However, larvae are highly susceptible to desiccation, so environmental changes that dry peat surfaces could harm cranefly populations and, in turn, bird populations. This thesis aims to examine effects of soil moisture, drainage and climate change on craneflies, and the relationship between craneflies and birds. A large-scale field experiment showed that adult cranefly abundance increased with soil moisture. Areas with blocked drainage ditches showed significantly higher soil moisture and cranefly abundance than areas with active drainage. A model of monthly peatland water tables driven by simple climate data was developed. The model accurately predicted water table position, and predicted up to two thirds of water table variation over time. Performance declined when modelling drained sites. The water table model was combined with empirical relationships to model cranefly abundance under climate change. Falling summer water tables were projected to drive cranefly population declines. Drain blocking would increase abundance and slow declines, thus aiding population persistence. Finally, modelled cranefly abundance was found to be a significant predictor of observed Golden Plover abundance, extinctions and colonisations on a large spatial scale. Across multiple species, variation explained by cranefly abundance was positively correlated with the proportion of craneflies in the diet. Managing peatlands to maintain and increase cranefly abundance could be an important part of conserving upland bird populations.
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Volk, Carol J. "Nutrient and biological responses to red alder (Alnus rubra) presence along headwater streams : Olympic Peninsula, Washington /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5470.
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Gottardelli, Chiara <1991>. "FOG COMPUTING: THE KEYSTONE FOR THE FUTURE OF INDUSTRIAL IoT. IMPACTS ON LEAN PRODUCTION ENVIRONMENTS." Master's Degree Thesis, Università Ca' Foscari Venezia, 2018. http://hdl.handle.net/10579/13667.
Full textAbstract:
The Fourth Industrial revolution dominates the current discussion of researchers on manufacturing.
At the same time, worldwide companies are becoming aware of the importance of Industrial IoT (IIoT) for competitive advantages.
Even Governments have assumed an important role in the field and set themselves as promoters of technological change with policies in favor of industrial digitalization.
In this scenario, Industrial IoT is driving the need for extensive adoption of advanced IT features across multiple Industry verticals. Moreover, in companies that apply Lean production concepts, IIoT accelerates Lean benefits.
The research gives an overview over existing combination of Industry 4.0 and Lean production, through Fog computing technology.
Fog computing brings many Cloud IT features close to industrial processes and merges those with real-time features, increasing production efficiency.
Fog Computing was introduced by Cisco in 2014 and a startup located in Silicon Valley, Nebbiolo Technologies, was the first pioneer on developing this new technology.
This company is deploying it in different industrial applications.
Considering the industrial automation, this thesis wants to underline the improvements and changes within corporate organizational structure resulting from the application of Fog computing.
Furthermore, this paper wants to validate the quantitative and qualitative data from two case studies deployed in worldwide companies: one in food industry and the other in the cosmetic and pharmaceutical sector.
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Mendes, Calebe Pereira [UNESP]. "Patch size, shape and edge distance influences seed predation in a keystone palm in tropical rainforests." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/122104.
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000814781.pdf: 508841 bytes, checksum: 114537088394da2fa462089c26ce1a78 (MD5)A predação de sementes é um importante tipo de processo ecológico, que afeta a abundância, diversidade e distribuição de espécies vegetais. Uma vez que esse processo ecológico depende da presença, abundancia e comportamento dos predadores de sementes, o que é afetado pelas características da paisagem, o processo de predação de sementes também acaba sendo afetado pelas características da paisagem. A maioria dos estudos em paisagens antrópicas não levam em conta as diferentes escalas em que esse processo opera. Aqui, nós avaliamos como a estrutura da paisagem afeta a predação de sementes de uma palmeira espécie-chave (Syagrus romanzoffiana) em 13 paisagens que variam em cobertura florestal, número e tamanho de fragmentos na Mata Atlântica brasileira. Nós observamos que a predação total de sementes é explicada pelo tamanho, forma e distância até a borda do fragmento. A predação de sementes pelo principal vertebrado predador de sementes (esquilos) também é relacionada com o tamanho e forma dos fragmentos, e eles interagem com os invertebrados de modo que a predação de sementes por estes é explicada principalmente pela predação por esquilos e pela distância até a borda mais próxima. Por sua vês, roedores não arborícolas são mais correlacionados com a quantidade de habitat na paisagem, predando mais sementes em paisagens com menos de 30% de habitat. Nossos resultados indicam que a predação de sementes de Syagrus romanzoffiana é mais afetada por variáveis do fragmento do que por variáveis da paisagem, e que o tamanho, a forma do fragmento e o efeito de borda são melhores preditores da predação de sementes dessa espécie-chave do que a quantidade de habitat na paisagem. Nossos resultados também ressaltam que a geometria do fragmento, uma variável negligenciada na maioria dos estudos, é importante para sistemas ecológicos
Seed predation is an important kind of ecological process that affect the abundance, diversity and distribution of plant species. Since this ecological process depends on the presence, abundance and behavior of seed predators, what it is affected by the landscape characteristics, the process of seed predation becomes also affected by the landscape characteristics. Most of studies on seed predation in human-modified landscapes do not take into account the different scales in which this process operates. Here we evaluate how landscape structure affects seed predation in a palm (Syagrus romanzoffiana) that provide a keystone resource to the frugivory community in 13 landscapes that vary in forest cover, fragment number and size in the Brazilian Atlantic forest. We found that the overall seed predation is explained by the fragment size, shape and the distance to the edge. Seed predation by the dominant vertebrate seed predator (squirrels) is also related with the fragment size and shape, and they interact with the invertebrates in such way that the invertebrate seed predation is mainly explained by the squirrel predation and by the distance to the edge. In turn, seed predation by terrestrial rodents is correlated with the habitat amount in the landscape, preying upon more seeds in landscapes with less than 30% of habitat. Our results indicate that the Syagrus romanzoffiana seed predation is more affected by the fragment variables than by landscape ones, and that patch size, shape and edge effect are more important predictors of seed predation of this palm than habitat amount in the landscape. Our results also highlights that the fragment geometry, a neglected variable in most of studies, is importance to ecological systems
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Halsband, Megan Claire Magee Carol L. "The Keystone Tour of the World 400 series stereographic images of Africa and American self-representation /." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,1600.
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Thesis (M.A.)--University of North Carolina at Chapel Hill, 2008.Title from electronic title page (viewed Sep. 16, 2008). "... in partial fulfillment of the requirements for the degree of Master of Arts in the Department of Art." Discipline: Art; Department/School: Art.
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Boom, Arthur. "Diversification, evolution and population dynamics of the genus Brachystegia, a keystone tree of African miombo woodlands." Doctoral thesis, Universite Libre de Bruxelles, 2021. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/331717.
Full textAbstract:
Miombo woodlands are vast wooded savannas covering 2 million km2 in East and Southern Africa. The main feature of these landscapes with closed but not overly dense canopy is the dominance of Brachystegia, Isoberlina, and Julbernardia legume trees genera. The timing of the onset of such vegetation, mainly understood through pollen fossils remains unclear. Dated molecular phylogeny calibrated with fossils for the aforementioned genera has the potential to provide details regarding the origin of species that nowadays dominate the current woodlands and possibly of miombo vegetation as a whole. The Brachystegia is a taxonomically complex genus and is compared to the other aforementioned genera, rich in species with 21 savanna species and eight species in the African Guineo-Congolian rain forests. We aim through the thesis to identify the diversification history of Brachystegia using dated phylogenies.We first reconstruct the Brachystegia phylogeny using nearly full plastome sequences in addition to ribosomal DNA sequences. Both sequences were obtained using a genome- skimming approach. In plastid phylogeny, species represented by multiple specimens appear rarely monophyletic while plastid clades display strong geographical structuring, independently of the species. Ribosomal phylogeny conversely allowed to identify morphological clades, but the lack of DNA polymorphism prevents the reconstruction of a well-resolved Brachystegia phylogeny. The strong spatial structure detected in plastid phylogeny suggests hybridization among the different species leading to recurrent chloroplast captures. Plastomes proved very informative for tracking the past dynamics of the genus and suggest a historical westwards expansion of miombo Brachystegia during the Plio-Pleistocene. We subsequently reconstructed the evolutionary history of the genus using targeted enrichment sequencing. Phylogenetic inferences were conducted using supermatrix and summary-method approaches on a dataset encompassing around 200 individuals loci for more than 200,000 base pairs. Opposite to previous reconstructions, most species appear as monophyletic groups even if high levels of gene tree conflict between the species trees and individual gene trees are reported, suggesting either incomplete lineage sorting (ILS) and/or reticulate evolution. Introgressed plastomes, and signature of ILS and reticulation for nuclear genes when species are nevertheless relatively well delineated by nuclear genome support to some extent that Brachystegia may behave a group of interfertile but still relatively well-delineated species (i.e. syngameon). Molecular dating analysis supports a Pliocene origin for the genus, with most of the diversification events occurring during the Plio-Pleistocene. We also conducted preliminary investigations to explore the potential of the genomics approaches used in this thesis to delineate problematic species or to reconstruct the past spatial dynamic of Brachystegia in current miombo regions.Overall, through this thesis, we clarified many aspects of the taxonomically complex Brachystegia genus. Genomic data support hybridization and plastid introgression on large spatial scales, giving credit to a Brachystegia syngameon that remains yet to be furthered characterised and validated. Moreover, results indicate a fairly recent origin of dominant species of the miombo congruently with their spatial expansion documented by plastid data, giving possibly insights into the temporal and spatial evolution of the miombo woodlandsDoctorat en Sciences
info:eu-repo/semantics/nonPublished
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Mendes, Calebe Pereira. "Patch size, shape and edge distance influences seed predation in a keystone palm in tropical rainforests /." Rio Claro, 2014. http://hdl.handle.net/11449/122104.
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Orientador: Mauro Galetti RodriguesCoorientador: Milton Cezar Ribeiro
Banca: Paulo Roberto Guimarães Junior
Banca: Marco Aurelio Pizo Ferreira
Resumo: A predação de sementes é um importante tipo de processo ecológico, que afeta a abundância, diversidade e distribuição de espécies vegetais. Uma vez que esse processo ecológico depende da presença, abundancia e comportamento dos predadores de sementes, o que é afetado pelas características da paisagem, o processo de predação de sementes também acaba sendo afetado pelas características da paisagem. A maioria dos estudos em paisagens antrópicas não levam em conta as diferentes escalas em que esse processo opera. Aqui, nós avaliamos como a estrutura da paisagem afeta a predação de sementes de uma palmeira espécie-chave (Syagrus romanzoffiana) em 13 paisagens que variam em cobertura florestal, número e tamanho de fragmentos na Mata Atlântica brasileira. Nós observamos que a predação total de sementes é explicada pelo tamanho, forma e distância até a borda do fragmento. A predação de sementes pelo principal vertebrado predador de sementes (esquilos) também é relacionada com o tamanho e forma dos fragmentos, e eles interagem com os invertebrados de modo que a predação de sementes por estes é explicada principalmente pela predação por esquilos e pela distância até a borda mais próxima. Por sua vês, roedores não arborícolas são mais correlacionados com a quantidade de habitat na paisagem, predando mais sementes em paisagens com menos de 30% de habitat. Nossos resultados indicam que a predação de sementes de Syagrus romanzoffiana é mais afetada por variáveis do fragmento do que por variáveis da paisagem, e que o tamanho, a forma do fragmento e o efeito de borda são melhores preditores da predação de sementes dessa espécie-chave do que a quantidade de habitat na paisagem. Nossos resultados também ressaltam que a geometria do fragmento, uma variável negligenciada na maioria dos estudos, é importante para sistemas ecológicos
Abstract: Seed predation is an important kind of ecological process that affect the abundance, diversity and distribution of plant species. Since this ecological process depends on the presence, abundance and behavior of seed predators, what it is affected by the landscape characteristics, the process of seed predation becomes also affected by the landscape characteristics. Most of studies on seed predation in human-modified landscapes do not take into account the different scales in which this process operates. Here we evaluate how landscape structure affects seed predation in a palm (Syagrus romanzoffiana) that provide a keystone resource to the frugivory community in 13 landscapes that vary in forest cover, fragment number and size in the Brazilian Atlantic forest. We found that the overall seed predation is explained by the fragment size, shape and the distance to the edge. Seed predation by the dominant vertebrate seed predator (squirrels) is also related with the fragment size and shape, and they interact with the invertebrates in such way that the invertebrate seed predation is mainly explained by the squirrel predation and by the distance to the edge. In turn, seed predation by terrestrial rodents is correlated with the habitat amount in the landscape, preying upon more seeds in landscapes with less than 30% of habitat. Our results indicate that the Syagrus romanzoffiana seed predation is more affected by the fragment variables than by landscape ones, and that patch size, shape and edge effect are more important predictors of seed predation of this palm than habitat amount in the landscape. Our results also highlights that the fragment geometry, a neglected variable in most of studies, is importance to ecological systems
Mestre
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Swigert, Tamra Ann. "A comparative evaluation of the influence the Boys & Girls Club and Keystone Club programs had on alumni in regards to career and life experiences." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2633.
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Williams, Thomas James. "Estimating organic carbon on avalanche paths in Glacier National Park, Montana." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4795.
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Avalanche paths are unique ecosystems that represent a significant portion of the landscape in the northern Rocky Mountains. Frequent avalanche disturbance results in vegetative cover that is unlike the adjacent coniferous forest. These high relief environments have the potential to remove carbon from the atmosphere at rates differing from those of the surrounding forest, and to regulate matter and/or energy fluxes to downslope ecosystems.
This thesis attempts to estimate organic carbon on south-facing avalanche paths in the southern portion of Glacier National Park, Montana. I am specifically interested in total organic carbon density, compartmental carbon density, and change in organic carbon over time as a function of shrub and tree diameter. Using an integrated sampling method, estimates of total organic carbon on avalanche paths appear to be different than those of the adjacent forest and similar to those of other shrub formation types in the area. However, the potentially moveable litter compartment is consistently larger. Organic carbon from shrub and trees growing on paths appears to be increasing at a continuous rate leading up to disturbance, while a typical individual's rate of increase appears to be slowing. The organic material temporarily stored on avalanche paths could serve as an important outside carbon source for near and distant aquatic ecosystems.
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Baeta, Alacio Marc. "Ecology of some keystone invertebrates inhabiting shallow soft bottom communities of the Maresme coast (NW Mediterranean Sea)." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/295965.
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Bivalves living in large aggregations of individuals (reefs or beds), such as mussels, clams, cockles and some high trophic predators such as sea stars, play an essential ecological role in the structure, integrity, stability, and diversity of the biological communities; being usually considered as keystone species. Their disappearance or decline could lead to disproportionate effects in their communities, even affecting the survival of other species. Although keystone species are crucial for maintaining the Earth biodiversity, often their study has not taken enough attention. The main aim of this Doctoral Thesis was to study the ecology of some keystone invertebrates inhabiting shallow soft bottom communities of the Maresme coast (Northwestern Mediterranean Sea). The results enhance the knowledge of the smooth clam (Callista chione) and also of its potential predators, several species of sea stars (Astropecten spp.) co-occurring in the area. But at the same time, our findings help to understand their trophic interactions, the status of their populations and propose guidelines for their conservation. Maresme coast is close to Barcelona and it has concentrated historically a high anthropogenic pressure that has altered and modified its environment. Our results have showed the critical status of the smooth clam bed as a consequence of the combination of different human coastal uses: sand dredging and clam fisheries. These anthropogenic pressures have also led to significant changes in Astropecten populations. A. aranciacus has been shown to be the most vulnerable, and consequently the most affected, to the extent that its population suffers an important and worrying decline. Moreover, A. aranciacus reproductive cycle, growth and depth segregation between size classes along the continental shelf have been described for the first time. Our results have documented Astropecten species niche segregation, which allow them to co-occur within a biological community scale, without compete for the same available recourses. Sea stars showed a partitioning of the prey (species) and microhabitats in the Maresme coast. This Doctoral Thesis aims to provide a valuable background to improve the conservation of these keystone invertebrates, as well as to promote the sustainable exploitation of shellfish.Els bivalves que viuen en grans agregacions d'individus, com ara algunes espècies de musclos, cloïsses i escopinyes; i alguns predadors que ocupen elevats nivells tròfics com ara les estrelles de mar juguen un paper fonamental en l'estructura, integritat, estabilitat i diversitat de les comunitats biològiques, sent habitualment considerats com espècies clau. La seva desaparició o declivi pot conduir a efectes desproporcionats sobre el conjunt de les comunitats on habiten, fins i tot afectant la supervivència d'altres espècies. Tot i que les espècies clau són essencials per mantenir la biodiversitat al planeta Terra, sovint no s'ha prestat prou atenció al seu estudi. El principal objectiu d'aquesta Tesi Doctoral ha estat l'estudi de l'ecologia d’algunes d’aquestes espècies clau que habiten els fons tous poc profunds de la costa del Maresme (nord-oest del Mar Mediterrani). Els resultats obtinguts milloren de manera significativa el coneixement de la població de petxinot de sang (Callista chione) i dels seus potencials depredadors, diferents espècies d'estrelles de mar (Astropecten spp.) que cohabiten a la zona. Al mateix temps ajuden a entendre les seves relacions tròfiques, l'estat de les seves poblacions i es proposen pautes per a la seva conservació. La costa del Maresme és molt propera a la ciutat Barcelona, i per això ha concentrat històricament una elevada pressió antropogènica que ha modificat i alterat el seu medi ambient. Els resultats d'aquesta Tesi Doctoral mostren com l'estat crític de la població de petxinot de sang (C. chione) és conseqüència de la combinació de diferents pressions antropogèniques: dragatges de sorres i la pesca de bivalves amb dragues. També s'ha observat que aquestes mateixes pressions han produït canvis significatius en les poblacions d'estrelles de mar Astropecten. A. aranciacus ha resultat ser l'estrella més vulnerable a aquestes pressions i en conseqüència ha estat la més afectada, veient-se la seva població disminuir a un ritme preocupant. A més, s'ha descrit per primera vegada la reproducció, el creixement i la segregació batimètrica per mida de A aranciacus. Els resultats obtinguts també mostren que les diferents espècies de Astropecten poden cohabitar per la segregació dels seus nínxols ecològics permeten-los no competir pels recursos disponibles (preses i hàbitat). Aquesta Tesi Doctoral pretén proporcionar un rerefons valuós per a millorar la conservació d'aquestes espècies clau, així com promoure l'explotació sostenible dels mol·luscs bivalves.
Los bivalvos que viven en grandes agregaciones de individuos, como por ejemplo algunas especies de mejillones, almejas y berberechos; y algunos predadores que ocupan elevados niveles tróficos como por ejemplo las estrellas de mar juegan un papel crucial en la estructura, integridad, estabilidad y diversidad de la comunidades biológicas, siendo habitualmente considerados como especies clave. Su desaparición o declive puede conducir a efectos desproporcionados sobre el conjunto de sus comunidades, incluso afectando la supervivencia de otras especies. Aunque las especies clave son esenciales para mantener la biodiversidad en el planeta Tierra, a menudo no se ha prestado suficiente atención a su estudio. El principal objetivo de esta Tesis Doctoral fue el estudio de la ecología de algunas especies clave que habitan los fondos blandos y someros de la costa del Maresme (noroeste del Mar Mediterráneo). Los resultados obtenidos mejoran de forma significativa el conocimiento sobre la concha fina (Callista chione) y sus depredadores potenciales, distintas species de estrellas de mar del género Astropecten que cohabitan en la zona. Al mismo tiempo ayudan a entender sus relaciones tróficas, el estado de sus poblaciones y se proponen pautas para mejorar su conservación. La costa del Maresme se halla cerca de la ciudad Barcelona, y por ello ha concentrado históricamente una elevada presión antropogénica que ha modificado y alterado su medio ambiente. Los resultados de esta Tesis Doctoral muestran como el estado crítico de la población de concha fina (C. chione) es consecuencia de la combinación de distintas presiones antrópogenicas: dragados de arenas y pesquerías de moluscos bivalvos. También se ha observado que estas mismas presiones han producido cambios significativos en las poblaciones de estrellas de mar Astropecten. A. aranciacus ha resultado ser la estrella más vulnerable a dichas presiones y en consecuencia ha sido la más afectada, viéndose su población disminuir a un rito preocupante. Además, se ha descrito por primera vez la reproducción, el crecimiento y la segregación batimétrica por tallas de A. aranciacus. Los resultados documentados también muestran que las distintas especies de Astropecten pueden cohabitar por la segregación de sus nichos ecológicos permitíendoles no competir por los recursos disponibles (presas y hábitat). Esta Tesis Doctoral pretende proporcionar un trasfondo valioso para mejorar la conservación de estas especies clave, así como promover la explotación sostenible de los moluscos bivalvos.
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Buwa, Ziphokazi Siyasanga. "The interaction between a keystone plant species and its dominant epiphyte on Marion Island : climate change implications." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/17743.
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Thesis (MSc)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: Climate has shown some remarkable changes over the past century, especially at the polar and sub-polar regions. Southern Ocean Islands provide good models for studies related to climate change effects, since effects may be evident in the short term and may also be clearer. Marion Island is an example of such a system with a harsh abiotic environment, and low species richness often vulnerable to change. Climate change is predicted, and also reported, to have biological consequences on plant communities, affecting the phenology, morphology, and the interaction between individuals and species. This study examines the association between the keystone plant species, Azorella selago Hook. (Apiaceace), and its dominant epiphyte Agrostis magellanica Lam. (Poaceae). Two complimentary approaches were used, one observational and the other experimental. The main objective for the observational study was to quantify bioticallyrelevant microclimate temperature, as well as the morphology, epiphyte load and phenology of A. selago at three different altitude sites on Marion Island. This provided information on baseline variation for understanding specific variability in plant response to the experimental part of this study, against which future patterns arising from biological monitoring can be compared. Studying plants at different altitudes provides a possible analogue for temperature-related climate change consequences for the ecology of A. selago, and its interaction with A. magellanica. The microclimate temperature associated with A. selago differed between the three sites examined. This difference was related to local topographic conditions and altitude differences. Cushion size differed distinctively between the three altitude sites, with this difference related to environmental heterogeneity such as differences in age and substrate structure. Azorella selago annual growth rate was estimated through stem length and the number of leaves on both exposed and shaded stems. Within-site variability, as well as epiphyte cover were found to be the contributing factors on A. selago annual growth rate. This highlights the importance of site-specificity when estimating growth rate within and between different altitude sites. Leaf characteristics differed between the sites, with this attributed to local habitat conditions, such as topography, as well as epiphyte cover. As expected, the difference in leaf size between exposed and shaded leaves demonstrated a larger specific leaf area on leaves shaded by A. magellanica. Agrostis magellanica abundance and density were altitudinally related, with A. selago demonstrating facilitation effects on A. magellanica. The trend shown in this study suggests that in spite of general facilitative effect of A. selago on A. magellanica towards higher altitudes, the abiotic environmental threshold for A. magellanica occurs at lower altitudes than it does for A. selago. Phenological differences were also apparent between the three sites. The objectives of the experimental part of this study were to quantify the effect of the dominant epiphyte, A. magellanica on biotically-relevant microclimatic temperatures, as well as on the phenology and physical condition of A. selago. Different treatments were applied to cushions at the three altitude sites to examine the shading effect of epiphytic A. magellanica on cushion plants, as well as the effect of treatment-related disturbance. Azorella selago microclimate temperature showed no significant difference between treatments, suggesting that on average epiphytic A. magellanica cover has no effect on cushion microclimate temperature. The percentage of flower budding and flowering of A. selago was negatively related to epiphyte cover. Cushion vitality was also responsive to epiphyte cover, with higher vitality scores on low grass covered cushions than on high grass cushions. This shows that A. magellanica competes with A. selago, while A. selago facilitates A. magellanica. Heavy epiphyte numbers impose negative effects on A. selago vegetative and reproductive performance, as well as cushion vitality. Therefore, the results of this research show that the vegetative and reproductive performance of A. selago and cushion vitality are likely to be negatively affected under ongoing climate change on Marion Island if this brings about heavier epiphyte loads on this keystone cushion plant species.
AFRIKAANSE OPSOMMING: In die afgelope eeu het die klimaat in die Antarktiese en sub-Antarktiese gebiede merkwaardige verandering getoon. Die Suidelike See Eilande dien as goeie modelle vir studies verwant aan die gevolge van klimaatsverandering, aangesien die kort termyn effekte in die gebiede duideliker mag wees in die toekoms. Marion Eiland is ‘n voorbeeld van so ‘n sisteem, met ‘n ruwe abiotiese omgewing en lae spesies rykheid, wat vatbaar is vir verandering. Daar word voorspel, en is reeds bevind dat klimaatsverandering biologiese gevolge op plant gemeenskappe het, in terme van morfologie, fenologie en die interaksie tussen individue en spesies. Hierdie studie ondersoek die assosiasie tussen die hoeksteen plant spesie, Azorella selago (Apiaceace), en sy dominante epifietiese gras, Agrostis magellanica Lam. (Poaceae). Die studie is op twee komplimentêre maniere benader, naamlik deur waarneming en eksperiment. Die hoof doel van die studie was om die biotiese belang van mikroklimaat temperatuur te kwantifiseer, en die hoeveelheid epifiete, die morfologie en die fenologie van A. selago te bepaal by drie verskillende hoogtes op Marion Eiland. Laasgenoemde het inligting verskaf oor die variasie in die reaksie van plante tot die eksperimentele aspek van die studie, waarteen patrone vanaf toekomstige biologiese beheer vergelyk kon word. Deur plante te bestudeer by verskillende hoogtes bo seespieël word ‘n moontlike analoog vir die gevolge van temperatuur-verwante klimaatverandering in terme van die ekologie van A. selago, en laasgenoemde se interaksie met A. magellanica verskaf. Die mikroklimaat temperatuur geassosieer met A. selago verskil tussen dié drie liggings. Die versil was verwant aan die plaaslike topografiese toestande en die verskillende hoogtes bo seespieël. Die grootte van die kussingplante het duidelik versil tussen die drie liggings, met die verskille verwant aan die omgewing se heterogeneïteit, byvoorbeeld die verskille in ouderdom en substraat struktuur. Azorella selago se jaarlikse groeitempo was bepaal deur die stingel lengte en die aantal blare, op beide die wat oorskadu is deur die gras, en die was nie oorskadu is nie. Daar is gevind dat die faktore wat bygedra het tot die jaarlikse groeitempo van A. selago, varieër binne die verskillende liggings, en bedekking deur epifiete. Dit beklemtoon die belang van spesifisiteit van ligging wanneer groeitempo in en tussen die liggings van verskillende hoogtes bepaal word. Die blaar eienskappe het verskil tussen verskillende liggings, as gevolg van plaaslike habitat toestande, soos topografie en bedekking deur epifiete. Soos verwag, het die blare wat oorskadu was deur A. magellanica ‘n groter spesifieke blaar area getoon as blare wat blootgestel was. Die hoeveelheid en digtheid van Agrosits magellanica was verwant aan hoogte bo seespieël, met A. selago wat fasiliterende effekte toon op A. magellanica. Die tendens waargeneem in hierdie studie is dat ten spyte van die algemene fasiliterende effek van A. selago op A. magellanica, die abiotiese omgewingsdrempel op ‘n laer hoogte is vir A. magellanica as vir A. selago. Fenologiese verskille was ook duidelik tussen die drie liggings. Die doel van die eksperimentele deel van die studie was om die effek van die dominante epifiet, A. magellanica, te bepaal op bioties relevante mikroklimaat temperature, asook op die fenologie en fiesiese toestand van A. selago. Verskeie behandelings is aangewend op die kussingplante by die drie liggings om die effek van skaduwee van die epifietiese A. magellanica op die plante te bepaal, asook die effek van versteurings versoorsaak deur die behandelings. Azorella selago se mikroklimaat temperatuur het geen betekenisvolle verskille tussen behandelings getoon nie, wat voorstel dat epifitiese A. magellanica oor die algemeen geen effek op die kussingplante se mikroklimaat temperatuur het nie. Daar was ‘n negatiewe verwantskap tussen die hoeveelheid epifiete op A. selago en die persentasie blomme en blomknoppe op die kussingplante. Die plante se vitaliteit was ook afhanklik van epifiet bedekking, met ‘n hoër vitaliteit telling vir kussingplante bedek met lae gras as die bedek met hoë gras. Dit toon dat A. magellanica met A. selago wedywer, terwyl A. selago vir A. magellanica fasiliteer. Hoë epifiet getalle het negatiewe effekte op A. selago se vegetatiewe en reproproduktiewe nakoming, asook die kussingplante se vitaliteit. Die resultate van hierdie studie toon dus dat die vegetatiewe en reproduktiewe nakoming van A. selago en kussingplant vitaliteit heel moontlik negatief geaffekteer sal word indien klimaatsverandering op Marion Eiland hoër epifiet getalle op die sleutel kussingplant spesie tot gevolg sal hê.
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Kourdougli, Nazim. "Hippocampal structural reactive plasticity in a rat model of temporal lobe epilepsy : chloride homeostasis as a keystone." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4091.
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Cette thèse a pour objectif spécifique d’explorer les événements précoces pouvant être à l’origine du bourgeonnement aberrant des fibres moussues (FM) du gyrus denté, une réorganisation majeure dans l’Epilepsie du Lobe Tempora (ELT). Nous avons utilisé le modèle pilocarpine d’ELT chez le rat afin de montrer que la transmission GABAergique jouait un rôle prépondérant dans la formation des FM aberrantes au cours de l’épileptogenèse. Ceci étant due à une altération de l’homéostasie chlore, suite à une augmentation de l’expression du co-transporteur NKCC1 et une diminution du co-transporteur KCC2. Nos résultats ont démontré que le récepteur aux neurotrophines p75NTR était un médiateur de l’action trophique de la réponse GABAergique dépolarisante sur le bourgeonnement aberrant des FM. Le blocage de l’action dépolarisante de la transmission GABAergique via l’utilisation de la bumétanide, a permis de réduire le bourgeonnement aberrant des MF en réduisant l’expression de p75NTR. Enfin, l’application transitoire de la bumétanide au cours de l’épileptogenèse a abouti à la réduction du nombre de crises récurrentes et spontanées au cours de la phase chronique d’ELT chez le rat. Ce travail a permis de dévoiler les mécanismes moléculaires sous-jacents de la réorganisation du réseau neuronal glutamatergique consécutif à une crise inaugurale dans un modèle d’ELT. Dans l'ensemble, cette thèse apporte un éclairage nouveau sur l’importance de l’interaction de la signalisation GABAergique avec les neurotrophines afin d’orchestrer la plasticité réactive au sein de l’hippocampe dans TLEThe present dissertation undertakes to investigate the early triggering events of the mossy fiber sprouting (MFS) in the dentate gyrus, a hallmark of hippocampal reactive plasticity in Temporal Lobe Epilepsy (TLE). We used the rat pilocarpine model of TLE to show that altered GABAA receptor-mediated transmission play a key role in the formation of early ectopic MFS during epileptogenesis. This is likely due to a compromised chloride homeostasis, as a result of increased expression of chloride loader NKCC1 and downregulation of the neuronal chloride extruder KCC2. We next addressed the mechanistic action of depolarizing GABAAR responses with regard to neurotrophin signaling. Our findings uncovered that the pan neurotrophin receptor p75 (p75NTR) mediated the sculpting action of depolarizing GABAAR responses on the ectopic MFS. Blockade of depolarizing GABAAR responses using the loop diuretic bumetanide reduced abnormal p75NTR subsequently decreased the ectopic MFS. Finally, transitory application of bumetanide during epileptogenesis resulted in reduction of spontaneous and recurrent seizures during the chronic phase of TLE. The rationale of this work is that unveiling the molecular mechanisms underlying the hippocampal post-seizure glutamatergic network rewiring will help to drive future novel therapeutic avenues involving chloride homeostasis and neurotrophin interplay. Overall, this dissertation shed a new light on how GABAergic transmission and neurotrophin signaling crosstalk can orchestrate reactive hippocampal plasticity in TLE
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Tanner, Justin Rogers. "Antimicrobial Producing Bacteria as Agents of Microbial Population Dynamics." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/30038.
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The need for new antibiotics has been highlighted recently with the increasing pace of emergence of drug resistant pathogens (MRSA, XDR-TB, etc.). Modification of existing antibiotics with the additions of side chains or other chemical groups and genomics based drug targeting have been the preferred method of drug development at the corporate level in recent years. These approaches have yielded few viable antibiotics and natural products are once again becoming an area of interest for drug discovery.
We examined the antimicrobial â Red Soilsâ of the Hashemite Kingdom of Jordan that have historically been used to prevent infection and cure rashes by the native peoples. Antimicrobial producing bacteria were present in these soils and found to be the reason for their antibiotic activity. After isolation, these bacteria were found to excrete their antimicrobials into the liquid culture media which we could then attempt to isolate for further study. Adsorbent resins were employed to capture the antimicrobial compounds and then elute them in a more concentrated solution.
As part of a drug discovery program, we sought a way to quickly characterize other soils for potential antibiotic producing bacteria. The community level physiologic profile was examined to determine if this approach would allow for a rapid categorizing of soils based on their probability of containing antimicrobial producing microorganisms. This method proved to have a high level of variability that could not be overcome even after mixing using a commercial blender.
The role of these antimicrobial producing bacteria within their natural microbial community has largely been confined to microbe-plant interactions. The role of antimicrobial-producing microorganisms in driving the diversity of their community has not been a focus of considerable study. The potential of an antimicrobial-producing bacterium to act as a driver of diversity was examined using an artificial microbial community based in a sand microcosm. The changes in the microbial assemblage indicate that antimicrobial-producing bacteria may act in an allelopathic manner rather than in a predatory role.Ph. D.
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Brown, Elin. "Datamigration av Content Management Systems (CMS) för Multi-siteapplikationer : En studie på SQL-till-NoSQL migration." Thesis, Högskolan i Skövde, Institutionen för informationsteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-15549.
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Detta arbete undersöker om existerande Multi-siteapplikationer i CMS-systemet WordPress kan uppnå bättre prestanda genom att övergå från WordPress till det nya CMS-systemet Keystone JS genom en datamigration. Denna migrationsprocess utvärderas med ett vetenskapligt experiment, för att undersöka om migrationsprocessen i sig eventuellt kan medföra prestandaproblem, men också kring när en migration är relevant och i slutändan värd att genomföra. Experimentet mäter svarstider för olika databasoperationer av den originella WordPress-applikationen samt den migrerade Keystone JS-applikationen. Resultatet av mätningen visade att den migrerade applikationen kan uppnå upp till 59% förbättrade svarstider för subdomänrendering, vilket bekräftar att Multi-siteapplikationer kan gynnas av en migration till Keystone JS. Migrationsprocessen ansågs heller inte ha någon individuell negativ prestandapåverkan.
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Axline-Minotti, Brooke A. "The Role of Threespot Damselfish (Stegastes planifrons) as a Keystone Species in a Bahamian Patch Reef." Ohio : Ohio University, 2003. http://www.ohiolink.edu/etd/view.cgi?ohiou1069441971.
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Dawson, Amanda. "Uptake dynamics and effects of traditional and emerging persistent environmental pollutants to the Antarctic keystone species, Antarctic krill." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/373031.
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The schooling Euphausiid, Antarctic krill (Euphausia superba) is considered a keystone species in the Southern Ocean due to its abundance, prominent role in nutrient cycling, and dependency of almost all Antarctic predatory species on this single species. It has often been postulated that polar species may be more sensitive to anthropogenic contaminants on account of their evolutionary isolation from exposure. Despite geographical isolation, anthropogenic contaminants have frequently been detected in the Southern Ocean and Antarctica biota, including, heavy metals, petroleum products, persistent organics pollutants (POPs) as well as microplastic (plastics <5 mm diameter) marine debris. This thesis examined the response of Antarctic krill exposed to two common pollutants; the POP compound para, para-Dichlorodiphenyldichloroethylene (p,p’-DDE), a metabolic by-product of the pesticide Dichlorodiphenyltrichloroethane (DDT); and polyethylene (PE) microplastics.
To investigate the fate of microplastics ingested by a grazing crustacean of high dietary plasticity, commercial microplastic PE beads were offered to Antarctic krill as a proportion of their diet. Krill were exposed to either a low (20%) or high (80%) dose plastic diet for four days, after which the faecal pellets and internal body burdens were examined. Antarctic krill were found to mechanically alter ingested microplastic beads into irregular fragments and nanoplastics. The capacity for fragmentation was found to be dependent on the concentration ingested. Further, the krill displayed size dependant depuration of the altered beads. This is the first time pristine microbeads have been noted to be physically altered by ingestion. With regards to the fate of commercial PE beads ingested by Antarctic krill, it appears that larger microplastics are fragmented into pieces that are small enough to cross biological barriers after ingestion, or are egested as a mixture of irregular triturated particles. These findings suggest that the current literature, based on observations from laboratory-based feeding studies, may be oversimplifying the way in which zooplankton interact with microplastics.
To investigate the uptake and depuration kinetics, bioaccumulation potential and detrimental health effects of irregular triturated microplastics Antarctic krill were exposed to commercial microplastic PE beads in a range of concentrations (10, 20, 40 and 80% plastic mixed diet). Toxicological endpoints of mortality and weight loss were both found to be non-sensitive for acute exposure in Antarctic krill. The depuration of particles large enough to be detected was found to be extremely fast, with krill eliminating 80% of their accumulated body burden in a matter of hours. Effective depuration was proposed to be the primary mechanism for mitigation of bioaccumulation and toxicity in krill, with bioaccumulation over 10 days of exposure found to be negligible. However, as uptake rates were similarly fast, and organisms in the marine environment are unlikely to experience microplastic free conditions to depurate their accumulated burden, chronic exposure over the lifetime of the organism with a continuous, yet variable, uptake and egestion is suggested to be a more likely scenario. Further, particles small enough to cross biological barriers were not quantified in this study, and the bioaccumulation potential of these particles remains to be evaluated.
To investigate sublethal p,p’-DDE exposure and identify potential biomarkers of sub cellular damage Antarctic krill were aqueously exposed to five treatments (1, 5, 10, 15 and 20 μg L-1) of p,p’-DDE. The response of enzymes with known roles in exogenous compound metabolism (glutathione S-transferase, GST and cytochrome P450 2B, CYP2B), neurotoxicity (acetylcholinesterase, AChE) and oxidative stress (glutathione peroxidase GPx) were quantified. CYP2B was not detectable in Antarctic krill. None of the enzymes detected induced linear concentration-dependant responses. GST was elevated at all exposure concentrations compared to the control, however no treatments were significantly different. GPx and GST followed similar trends throughout the treatment responses suggesting that an underlying biological factor may be influencing both enzymes. AChE activity was not correlated with p,p’-DDE exposure concentration, but all concentrations displayed lower activity than the solvent control however no treatment was significantly inhibited by p,p’-DDE in Antarctic krill. These findings did not provide evidence for an activated detoxification response to p,p’-DDE via the targeted biochemical pathways in Antarctic krill. These findings provide an important baseline for future work to establish the mechanisms of organochlorine toxicity and further our understanding of Antarctic krill detoxification capabilities.
Overall, the results of the work described in this thesis characterise several key interactions between anthropogenic pollutants and Antarctic krill. This work provides a comprehensive foundation for further investigation on the combined effect of p,p’-DDE and polyethylene microplastic stressors, as well as other microplastics and POPs in isolation and as mixtures, which may better reflect environmental conditions.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Cuenca, Cambronero Maria. "Documenting long-term impact of eutrophication and climate change on the keystone species Daphnia using resurrection ecology and paleogenomics." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8275/.
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Dramatic loss of biodiversity in the last two decades has been associated with human activities. Yet, we understand little of the mechanisms that enable species persistence to anthropogenic environmental changes over evolutionary time. Here, we measured ecological and evolutionary responses of a population of Daphnia magna to multiple anthropogenic stressors over evolutionary time, and assessed the role of historical exposure in adaptive response to recurring environmental stress. D. magna is a keystone grazer in freshwater standing waters and a driver of ecosystem dynamics. As part of its life cycle, Daphnia produces dormant embryos that arrest their development entering dormancy and creating a long-term documentation of evolutionary responses to environmental change. Resurrected dormant stages are maintained as clonal lines in the laboratory, providing us with the unique opportunity of disentangling the role of phenotypic plasticity and genetic adaptation in population responses to environmental stress. We studied phenotypic, physiological, and molecular responses that enabled a population of D. magna to persist across major pollution events. We found that adaptive responses to multiple environmental stressors are not predictable from the responses to single stressors. We also discovered that historical exposure to stress prior to dormancy provides an evolutionary advantage when the stress recurs. However, this advantage is contingent upon the type and severity of environmental stressor. We discovered that response to environmental stress is underpinned by extensive epistasis and pleiotropy, suggesting that standing genetic variation is the clay of evolution in this species.
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Combrinck, Madeleine Lelon. "A computational fluid dynamic analysis of the airflow over the keystone plant species, Azorella selago, on sub-antarctic Marion Island." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2314.
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MScEngThesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.
Research conducted on Marion Island aims at predicting the consequence of climate change in the Subantarctic region, as well as for other terrestrial ecosystems. The island has the ideal ecosystem, due to its size, isolation and relative simplicity, to be studied as a prediction model for the consequence of climate change and the interaction between various climate related parameters. The cushion plant, Azorella selago, is the focal point of this project due to the important functional roles it fulfils as well as its wide spread distribution over the island. A. selago grows in three different shapes; hemispherical, elliptical and crescent. The changes in airflow due to varying plant size are investigated as well as the exertion of force on the plant. The grass species Agrostis magellanica has the tendency to grow on top of A. selago. In addition it has been observed that the grass species grows more vibrantly on the leeward side of the cushion plant. In the light of this observation the particle deposition of grass seeds on A. selago is also investigated. Computational fluid dynamic analyses are conducted for various sizes of each shape of the plant. These studies are augmented by wind tunnel and in situ measurements and observation and experimental determining of particle drag coefficients. Time independent, incompressible, turbulent flow is modelled by means of a high Reynolds number turbulence model with a modified Law-of-the- Wall to accommodate for the significant surface roughness. Nine different dimensions over the various shapes were identified. Each shape is analysed and the patterns that emerged discussed. The windward pattern for all shapes display similar qualities. On the leeward side the shapes display distinctly different airflow patterns. The hemisphere shows two trailing lines typically associated with the horseshoe vortex phenomenon. The ellipse displays one distinctive trailing line. The most interesting flow patterns are found when analysing the crescent shape. Three trailing lines are observed, the side lines quickly dissipates with increasing height while the middle line remains distinctive. The complex recirculation patterns that emerge are further visualized by means of air particle tracks. The furthermost number of light particle deposition of A. magellanica seeds on A. selago are found at the windward location while physical evidence clearly indicates growth primarily on the leeward position. The leeward location on A. selago is protected from the harsh environmental conditions; wind speeds are minimal in this area. It will therefore be a more suitable site for the fostering of a vulnerable seedling that on the exposed windward side. A force analysis done on the plants reveals that the total force is two orders of magnitude higher that the shear force. Furthermore, the magnitude of the total force is directly proportional to the size of the plant. Three critical areas on the plant are common irrespective of shape or size: the stagnation point at the windward side, the apex region at the top and the leeward side of the plant.
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Seymour, Colleen. "The influence of size and density of the Camelthorn (Acacia erioloba Meyer) on its keystone role in the Xeric Kalahari." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/12408.
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Includes bibliographical references.Within the savannas of the southern Kalahari, land use practices can change habitat structure profoundly, so that rangelands either became densely wooden through bush thickening or are cleared completely using arboricides or manual tree felling and bush clearance, or are at some stage in between. Demands for the wood of camelthorn trees (Acacia reioloba), (the largest tree species growing on semi-arid and arid Kalahari sands) for firewood has also impacted habitat structure. Large trees are important in the Kalahari ecosystem because they provide shade, nesting and foraging sites for birds and mammals, as well as microhabitats that facilitate the existence of a suite of subcanopy plants. Indeed, large A. erioloba tress have been mooted as a context-depend keystones species, important to other biota and ecological prcesess. The primary aim of this study was to investigate the importance of A. erioloba to biodiversity, focusing on plants and birds.
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Oakes, Claudia Lea. "History and consequence of keystone mammal eradication in the desert grasslands : the Arizona black-tailed prairie dog (Cynomys ludovicianus arizonensis) /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Posthumus, Erin Elizabeth. "Do Red Squirrel Middens Promote Vertebrate Species Diversity?" Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/294022.
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The modifications animals make to their environments can be critical to species diversity. Red squirrels (Tamiasciurus hudsonicus) create large piles of conifer cone debris (middens) and are hypothesized to function as a keystone species due to positive associations between middens and other vertebrate species. We assessed vegetation and landscape structure at middens with a resident red squirrel for varying consistencies over the prior 5 years and surveyed mammals and birds at the community and population level. After accounting for vegetation and landscape characteristics, red squirrel-created resources positively influenced species richness of medium and large mammals and ground foraging birds, abundance of deer mice (Peromyscus maniculatus) and ground foraging birds, and activity of cliff chipmunks (Tamias dorsalis). Increased knowledge of the interaction strength of the red squirrel with its environment may be used to inform decisions in forest management and restoration and offer insight on the conservation value of larderhoarding mammals.
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McCoy, Neil L. "The Geographical Mosaic of Myrmecochory in a Global Biodiversity Hotspot and the Fate of Myrmecochorous Seeds Dispersed by a Keystone Seed Disperser." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-12112008-142107/.
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Seed dispersal mutualisms are important ecological interactions that can shape plant communities by influencing species distributions, community composition, and the regeneration of populations following a disturbance. Considering the fundamental role seed dispersal mutualisms play in many plant communities, it is important to understand, both generally and for individual seed dispersal mutualisms, what determines when animal partners successfully disperse seeds and when they do not. Myrmecochory, the dispersal of seeds by ants, is the most common form of zoochory in Western Australia. Myrmecochore plant diversity is richest in the Kwongan sandplains of the south-west, where ant-dispersed species can make up as much as 36% of the plant community. Here, I studied the determinants of seed dispersal rates to understand local variation in myrmecochorous seed dispersal rates. At a series of 30 sites, we sampled the ant and plant communities, measured aspects of the community structure (vegetation height, openness, topography, soil), measured seed removal rates and observed ant-seed interactions. The most significant factor that governed seed removal rates was the presence of the ant species Rhytidoponera violacea. Additionally, during seed dispersal observation trials, R. violacea removed 95% of all seeds taken. To better understand the fate of Acacia blakelyi seeds dispersed by R. violacea, we simulated variable seed burial depths and elaiosome removal by ants, followed by a bushfire to stimulate germination. Seed burial depth had a significant effect on seedling emergence, with the proportion of emerged seedlings declining with burial depth. The effect of depth was due to the strength of a fire-cue (heat) declining with depth. Seed burial depth also had a fitness cost, with a greater proportion of ârobustâ seedlings emerging from seeds buried closer to the surface. Seeds buried too deep to receive fire-cues remained dormant, adding to a long-lived soil seed bank.
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Sandom, Christopher. "Wild boar, wolves and fences : managing ecosystem engineers and keystone species to restore ecological processes, a case study in the Scottish Highlands." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542969.
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Shadwell, Eleanor. "Top-down or bottom-up?: Impacts of giraffe browse and water abstraction on two keystone tree species of the Kgalagadi Transfrontier Park." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22908.
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In this thesis I determine how an emphasis on tourism may have both a top-down and bottom-up affect on the two most dominant tree species in the southern Kalahari Desert of central southern Africa. Both tree species are considered as keystone species especially along ephemeral rivers. My focus is on the impact of the introduction of an extralimital megaherbivore, Giraffa camelopardalis, (top-down) and anthropogenic water abstraction (bottom-up) on the reproductive output and vegetation structure of Acacia erioloba and Acacia haematoxylon in the Kgalagadi Transfrontier Park. I determine the impact of giraffe on canopy structure and reproductive potential of the two tree species by comparing three zones of giraffe density (high, medium and low) along the Auob River. I do this through a series of transects through the river to determine both giraffe and tree density and also photographed several trees to determine change in canopy width, percentage canopy death and change in the number of flowers and pods between the three zones and between species. My results show a significant negative impact of giraffe browse on canopy structure, specifically for A. haematoxylon. I did not however find any significant differences in recruitment between the different giraffe density zones. However, a noticeable decrease in numbers of flowers and pods in the giraffe browse height of trees (2 - 5 m) between zones suggest that giraffe will have a negative effect on the A. haematoxylon population but not the A. erioloba population in the future. I use stable hydrogen and oxygen isotope ratios to determine the water source for the two tree species. I do this relative to the stable isotope ratio of the water extracted from nearby boreholes. I also determine how close to physiological stress the trees are (using specific leaf area, leaf δ¹³C values, canopy death and midday xylem pressure potentials) both upstream and downstream of active boreholes used for two tourist camps. One camp, Nossob, in the Nossob River is abstracting at a high rate while the other camp, Urikaruus, in the Auob River is abstracting at a lower rate. My results for water isotope ratios show that both A. erioloba and A. haematoxylon are using deep groundwater. My results also show that in the dry season, A. erioloba in the Nossob are losing contact with groundwater and have to rely on some as yet unmeasured water source in the soil profile. This 'stress' is not reflected in canopy dieback as yet. The trees continue to transpire in the dry season suggesting that they are physiologically able to adapt to fluctuations in the water table of between 4.5 - 5.2 m between the wet and dry season by closing their stomata but are prone to drought-induced carbon starvation, specifically for trees in the Nossob. Overall, my results show that the impact of giraffe on vegetation structure is already evident for A. haematoxylon, indicative of future negative effects on reproduction. My research also shows that although current levels of water abstraction are as yet not affecting vegetation structure below the abstraction points, the trees are edging closer to thresholds of water stress that would be exacerbated with drought. These findings are discussed within the context of ecosystem health and management implications for the giraffe population and water use within the Park.
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Åhman-Persson, Charlotte, and Elin Langeveld. "The effect of Parvimonas micra on gingipain activity in different strains of Porphyromonas gingivalis." Thesis, Malmö universitet, Odontologiska fakulteten (OD), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-19987.
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Syfte: Syftet med denna studie var att experimentellt bestämma om Parvimonas micra ökar tillväxt och gingipainaktiviteten hos olika stammar av Porphyromonas gingivalis. En ökning av gingipainaktiviteten indikerar att P. micra skulle kunna öka virulensen i P. gingivalis.Material och metod: Fem stammar av P. gingivalis 1A, 16A, 50A, 33F och W50 odlades med P. micra och jämfördes med kontrollen som endast innehöll P. gingivalis. Arginin gingipain (Rgp) och lysin gingipain (Kgp) aktivitet mättes med hjälp av Bikkam-16 respektive Bikkam-14. Bakterietillväxt mättes genom att mäta optisk densitet.Resultat: Experimenten visade en ökad tillväxt av stammarna 1A, 16A och 50A när de odlades med P. micra, 33F visade måttlig tillväxt och W50 ingen tillväxt.Rgp aktiviteten ökade i vissa P. gingivalis-stammar (1A och 16A) i närvaro P. micra men ökade inte i andra (W50, 33F och 50A)Kgp aktiviteten ökade i P. gingivalis lA i närvaro av P. micra men ingen ökning skedde i de andra stammarna (16A, W50, 33F och 50A).Slutsats: Resultaten från denna studie visade att P. micra påverkar tillväxten och gingipainaktiviteten hos vissa stammar av P. gingivalis men inte alla.Aim: The aim of this study was to experimentally determine if Parvimonas micra increase growth and gingipain activity in different strains of Porphyromonas gingivalis. An increase in gingipain activity could indicate that P. micra induces pathogenic expression of P. gingivalis.Material and method: Five strains of P. gingivalis 1A, 16A, 50A, 33F and W50 was cultivated together with P. micra while control samples contained only P. gingivalis. Activity of arginine gingipain (Rgp) and lysine gingipain (Kgp) was measured using Bikkam-16 respectively Bikkam-14. Bacterial growth was determining by measuring the optical density.Results: The experiments show an increased growth of some strains (1A, 16A and 50A) of P. gingivalis when grown with P. micra, one showed moderate growth (33F) and one showed no growth (W50).The gingipain activity (Rgp) increased in P. gingivalis strains (1A and 16A) in the presence of P. micra but did not increase in other strains (W50, 33F and 50A)The gingipain activity (Kgp) increased in one P. gingivalis strains (1A) when mixed with P. micra and did not increase in others (16A, W50, 33F and 50A). Conclusion: The results from this study indicates that P. micra effect the growth and gingipain activity in certain strains of P. gingivalis but not all.
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Simon, Kallstenius Ivan. "Patterns of Collaboration for Sustainability in the Global Clothing Industry." Thesis, Stockholms universitet, Stockholm Resilience Centre, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-169781.
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Global industries are characterized by complex networks of organizations, which are often dominated by a few disproportionately large transnational corporations. While industry consolidation is not a new phenomenon, the scale and speed at which global industries now impact diverse social-ecological systems is unprecedented. In this thesis, I combine the interconnected perspective of business ecosystems with the sustainability focus of the social-ecological systems literature through the concept of keystone actors. Adopting a network perspective, I apply this framing to the global clothing industry, and specifically analyze the patterns of coordination and collaboration among actors working to address systemic sustainability challenges facing the industry. While keystone actors wield significant influence over both the industry’s biophysical and socio-economic impacts, I find it is the presence of key brokers – actors who mediate indirect connections between keystone actors in the clothing industry – that possess the potential to coordinate action around sustainability challenges into a collective industry-wide effort. I conclude the thesis by discussing how the empirical findings, and network perspective more generally, can advance the study of keystone actors in global business ecosystems.
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Cole, Nigel. "Arguing Assurance in Trusted Execution Environments using Goal Structuring Notation." Thesis, Linköpings universitet, Programvara och system, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-177923.
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A trusted execution environment (TEE) is an isolated environment used for trusted execution. TEE solutions are usually proprietary and specific for a certain hardware specification, thereby limiting developers that use those TEEs. A potential solution to this issue is the use of open-source alternatives such as the TEE framework Keystone and the Reduced Instruction Set Computer V (RISC-V) hardware. These alternatives are rather young and are not as well established as the variants developed by ARM and Intel. To this end, the assurance in Keystone and RISC-V are analysed by studying a remote attestation assurance use case using the goal structuring notation (GSN) method. The aim is to investigate how GSN can be utilised to build assurance cases for TEEs on RISC-V. This thesis presents a process of how GSNs can be created to argue assurance for a TEE solution. Furthermore, Keystone operates under a specific threat model with made assumptions that may have a large impact depending on the use case. Therefore, Keystone is analysed to understand whether the framework mitigates existing vulnerabilities in TEEs. It is concluded that GSN is a viable method for arguing assurance in TEEs, providing great freedom in the creation of the GSN model. The freedom is also its weakness since the argument composition has a high impact on the argument. Furthermore, we conclude that Keystone mitigates multiple known vulnerabilities primarily through made assumptions in its threat model. These cases need to be considered by developers utilising Keystone to determine whether or not the assumptions are valid for their use case.
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Vice, President Research Office of the. "Species Showdown." Office of the Vice President Research, The University of British Columbia, 2006. http://hdl.handle.net/2429/2700.
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Suvarnaraksha, Apinun. "Biology of two keystone fish species and fish assemblage patterns and modeling approaches in tropical river basin : case study of Ping river basin, Thailand." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1537/.
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La région Indo-Birmane est un formidable hotspot de diversité biologique, mais il existe un manque évident de connaissances fiables sur la diversité des poissons, la biologie et l'histoire de vie des communautés, ainsi que des approches de modélisation des données. Ce travail de thèse apporte des informations sur la diversité des poissons et de la distribution dans une zone de montagne de haute et de basse altitude dans la partie supérieure du bassin du fleuve Chao Phraya, en Thaïlande. Des données de terrain ont été collectées sur quatorze années entre Janvier 1996 et avril 2009, couvrant 272 enquêtes dans 10 sous-bassins hydrographiques fournissant la richesse spécifique et des indices de diversité. Cette thèse a été divisée en 3 niveaux principaux : le niveau taxonomique (niveau descriptif), la biologie des poissons (niveau descriptif et prédictif), et la diversité des assemblages de poissons en fonction des facteurs environnementaux (niveau prédictif). Tout d'abord, concernant l'étude de la diversité des poissons (publication 1, P1): la raréfaction a été utilisée pour extrapoler la richesse spécifique et le nombre optimal d'espèces dans le bassin supérieur du fleuve Chao Phraya. Deux cent une espèces réparties dans 104 genres et 34 familles ont été collectées, dont 16 espèces exotiques. Les poissons sont dominés par la famille des Cyprinidae, suivie par les Balitoridae et les Cobitidae, caractéristiques de la zone de haute altitude. Le taux d'endémisme global dans la zone a été estimé à environ 10%. La plupart des espèces de poissons est particulièrement caractéristique des habitats rhithroniques. Ensuite, nous avons étudié la dynamique de population des espèces de poissons clefs de la zone d'étude à savoir, (1) l'histoire de vie d'un cyprinidae Henicorhynchus siamensis (Sauvage, 1881) d'un petit réservoir (Publication 2; P2) et (2) la biologie de la reproduction et la conservation de l'espèce vulnérable des cours d'eau thaïlandais Oreoglanis siamensis aux contreforts de l'Himalaya (Publication 3; P3). Les deux espèces sont des représentants de l'état écologique des écosystèmes lentiques et lotiques. H. Siamensis est une espèce riverine migratrice qui s'adapte bien à des conditions de réservoir (eau stagnante) et c'est un poisson économiquement important en apportant une source de protéines à des populations rurales de la région. La reproduction, le régime alimentaire et la croissance de H. Siamensis ont été étudiés. Par exemple, on sait que la ponte est en saison humide, la taille de maturité est d'environ 200 mm, et l'espèce se nourrit de phytoplancton, etc. Par contre, O. Siamensis est une espèce vulnérable et endémique, qui vit dans eaux rapides froides de haute montagne. La période de frai est la saison sèche. La taille de maturité est de 68,9mm pour mâles et de 82,4mm pour les femelles et le taux de fécondité est d'environ 31 œufs de grande taille (arphi ~= 3 mm). Enfin, nous avons étudié les relations entre paramètres biologiques et paramètres environnementaux, visant à expliquer les assemblages des poissons dans la zone d'étude (Publication 4; P4). Les patrons de diversité des assemblages de poissons dans la zone amont du bassin de la rivière Ping-Wang ont été étudiés. Des outils mathématiques (par exemple, SOM, ANN) ont été utilisés pour analyser les relations entre paramètres environnementaux (physico-chimiques et paramètres géomorphologiques dans le bassin de la rivière longitudinal et la diversité des poissons. Les arbres de classification et de régression (CART) ont montré que les paramètres géo-morphologiques ont été plus importants dans le modèle de prédiction à la fois pour la richesse spécifique et l'indice de diversité de Shannon. Les paramètres physico-chimiques sont moins importants, et exprimés surtout par l'altitude. Les poissons ont été classés dans 4 groupes d'assemblage à savoir, montagne, piémont, zone de transition et de plaine. Enfin, les effets de barrage sur les assemblages de poissons de rivière ont été montrés dans la Publication 5 (P5). Le SOM (self-organizing map) a été utilisé pour classer les communautés de poissons. Trois communautés de poissons ont été obtenues, à savoir de réservoir, de ruisseau et de la zone intermédiaire. Les communautés des réservoirs caractérisées par des espèces adaptées aux conditions lentiques sont par exemple Labiobarbus lineatus, (Sauvage, 1878) et Puntioplites proctozysron (Bleeker, 1865), alors que les espèces rhéophiles sont par exemple Rasbora paviana Tirant, 1885 et Channa gachua (Hamilton, 1822). La communauté de la zone intermédiaire contenait un mélange d'espèces des deux autres communautés. Le pourcentage global de bonne prédiction par le modèle a été de 66,0% : le modèle a correctement prédit 100% des communautés de réservoir, mais très peu de communautés rhéophiles (40%). Les communautés de poissons dans la zone d'étude sont menacées par la déforestation, la collecte des poissons d'aquarium, et la présence des espèces exotiques dans la partie supérieure. La présence des espèces évadées de l'aquaculture devrait être un facteur important en termes d'hybridation génétique. Toutefois, dans le bassin du fleuve Chao Phraya, les travaux sur l'écologie aquatique et la diversité des poissons sont peu nombreux et plus d'études scientifiques sont nécessaires pour atteindre le but ultime de l'utilisation rationnelle et durable des ressources aquatiques de cette régionIndo-Burma hotspot is an incredibly rich biological diversity area, but lack of reliable fish diversity, biology and life history, fish assemblage, and modeling approaches data. This present works on fish diversity and distribution in a unique high altitude mountain to lowland area in the upper part of the Chao Phraya river basin, Thailand. Fourteen years of field dataset in the basin were used, collected between January 1996 and April 2009, covering 272 surveys of 10 sub-river basins to produce species richness and diversity indices. This thesis was divided into 3 main levels viz. , taxonomic level (descriptive level), biology and life history of fishes (descriptive level to predictive level), and assemblages of fish diversity as function of environmental factors (predictive level). Firstly, fish diversity study (Publication 1; P1): the rarefaction was employed to extrapolate species richness and optimum species numbers in the upper Chaophraya river basin. Two hundred and one species in 104 genera and 34 families were collected, including 16 exotic species. Cyprinidae fish family was dominated, followed by Balitoridae and Cobitidae, implying the characteristic of high altitude area. The overall endemism in the area was found to be about 10%. Most of the fish communities were especially characterized by rhithronic habitants. Second, there were studies investigating life history and population dynamics of the keystone fish species in the study area i. E. , (1) life history of riverine cyprinid Henicorhynchus siamensis (Sauvage, 1881) in a small reservoir (Publication 2; P2) and (2) reproductive biology and conservation approaches of a vulnerable species Siamese Freshwater batfish (Oreoglanis siamensis) from foothill Himalayan, Thailand (Publication 3; P3), both species were the representative of lentic and lotic ecosystem conditions. H. Siamensis has a well adaptation from riverine species to reservoir conditions (stagnant water) and it was an important economic fish providing protein source to rural people around the reservoir. The reproductive, feeding aspects and growth of H. Siamensis were studied e. G. Spawning season in wet season, the length of 50% maturity (about 200 mm), and feed on phytoplankton, etc. Meanwhile, O. Siamensis is a vulnerable species and endemic species, which inhabits cold swift of high mountain streams. The spawning time occurred in dry season. Meanwhile, the length of 50% maturity were 68. 9 (males) and 82. 4 (females) mm and it was a few fecundity (31. 41 ± 7. 67 eggs) and large eggs (arphi ~= 3 mm). Thirdly, there were studies about the relationships between biological parameters and environmental parameters which were also beneficial to investigate fish diversity and assemblage patterns in the studied area (Publication 4; P4). Fish diversity and assemblage patterns in the rhitral environment of the Ping-Wang river basin were investigated. Mathematics tool models (e. G. SOM, ANN) were used for analysing of the relationship between environmental parameters (physicochemical and geo-morphological parameters and fish diversity in longitudinal in the river basin, and the prediction of its diversity. The classification and regression trees showed that the geo-morphological parameters were more significant in controlling and predicting both species richness and Shannon diversity index than the physicochemical parameters, in which altitude was the most significant. The fish assemblages were organized into 4 assemblage patterns viz. , mountainous, piedmont, transitory and lowland species. And lastly, the investigation of the effects of dam to the riverine fish assemblages was showed in Publication 5 (P5). A self-organizing map (SOM) was used to cluster the fish community; three fish communities were obtained characterizing reservoir-, stream- and intermediate- communities. The reservoir communities were characterized by "lentic-adapted" fish i. E. Labiobarbus lineatus, (Sauvage, 1878) and Puntioplites proctozysron (Bleeker, 1865), whereas rheophilic species, i. E. Rasbora paviana Tirant, 1885 and Channa gachua (Hamilton, 1822), were dominant in the stream community. The intermediate community contained a mixture of species from both the other communities. The overall percentage of successful prediction by the model was 66. 0 %: the model was 100% accurate for the prediction of the reservoir community but very low for the stream community (40%). Threats to fish communities were deforestation, collection for aquarium fish, and the distribution of the exotic species in the upper reaches. Meanwhile distribution of aquaculture escapes should be a concerned in terms of genetic hybridization. However, in the Chao Phraya river basin, research on the aquatic ecology and fish diversity are few and need more scientific information to reach the ultimate goal of wise and sustained uses of aquatic resources