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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Campanian-maastrichtian Planktonic Foraminiferal Investigation And Biostratigraphy (kokaksu Section, Bartin, Nw Anatolia): Remarks On The Cretaceous Paleoceanography Based On Quantitative Data

Guray, Alev 01 August 2006 (has links) (PDF)
The aim of this study is to delineate the Campanian-Maastrichtian boundary by using planktonic foraminifers. In this manner, Kokaksu Section (Bartin, NW Anatolia) was selected and the Akveren Formation, characterized by a calciturbiditic-clayey limestone and marl intercalation of Campanian-Maastrichtian age, was examined. 59 samples were emphasized for position of boundary. Late Campanian-Maastrichtian planktonic foraminifers were studied in thin section and by washed samples. Two different biostratigraphical frameworks have been established. Globotruncanid zonation consists of Campanian Globotruncana aegyptiaca Zone, Upper Campanian-Middle Maastrichtian Gansserina gansseri Zone and Upper Maastrichtian Abathomphalus mayaroensis Zone, whereas heterohelicids biozonation includes Campanian Pseudotextularia elegans Zone, Lower Maastrichtian Planoglobulina acervuloinides Zone, Middle Maastrichtian Racemiguembelina fructicosa Zone and Upper Maastrichtian Pseudoguembelina hariensis Zone. Campanian-Maastrichtian boundary was determined as the boundary between Pseudotextularia elegans and Planoglobulina acervuloinides zones and Cretaceous-Tertiary boundary was designated by total disappearance of Late Cretaceous forms. Heterohelicid biozonation has been established in this study for the first time in Turkey. Collecting 300 individuals from each sample, diversity and abundance of assemblages were analyzed in terms of genus and species. ir evaluation of are important in observation of evolutionary trends and ecological changes. Moreover, evolution of different morphotypes is important in this evaluation. Such a study is new in Turkey in terms of examination of responses of planktonic foraminifers to environmental changes. Taxonomic framework has been constructed to define each species and differences of comparable forms have been discussed. Both scanning electron microscope (SEM) photographs and thin section photographs were used in order to show se distinctions.
272

Observer error in identifying species using indirect signs: analysis of a river otter track survey technique

Evans, Jonah Wy 17 September 2007 (has links)
Indirect signs of species presence (e.g., tracks, scats, hairs) are frequently used to detect target species in occupancy, presence/absence, and other wildlife studies. Indirect signs are often more efficient than direct observation of elusive animals, making such signs well suited for long-term and broad-scale monitoring programs. However, error associated with misidentification of indirect signs can be high, and should be measured if meaningful inferences about population parameters are to be made. This study addressed the need for systematic approaches to estimate and minimize variation due to observer error in identifying indirect signs. I reanalyzed data from 4 replicates of a presence/absence survey of northern river otters (Lontra canadensis) that had been conducted by Texas Parks and Wildlife Department (1996-2003). Sixteen observers had recorded tracks at sample points under bridges (n = 250) distributed throughout 27 counties in the Piney-Woods ecoregion of east Texas. My objectives were to 1) determine if observers were a source of bias in the survey, 2) estimate the proportion of error associated with track identification skill, and 3) evaluate the use of an international certification procedure that measured observer tracking skill. The null hypothesis that observers had no effect on the variation in reported sign was rejected. Indeed, binary logistic regression tests indicated that observers were significantly associated with variation in reported track presence. Observers were not randomly distributed among bridge sites, and therefore were significantly correlated with 4 habitat variables that may have influenced heterogeneity in otter occupancy and probability of detection (watershed, vegetation-type, water-type, bridge-area). On average, experienced observers (n = 7) misidentified 44% of otter tracks, with a range of 0% to 100% correct detection. Also, 13% of the tracks of species determined to be 'otter-like' were misidentified as belonging to an otter. During the certification procedure, participants misidentified the tracks of 12 species as otter. Inaccurate identification of indirect signs is a likely source of error in wildlife studies. I recommend that observer skill in identification of indirect signs be measured in order to detect and control for observer bias in wildlife monitoring.
273

Herbivore abundance in simple and diverse habitats [electronic resource] : the direct and indirect effects of plant diversity and habitat structure / by Laura F. Altfeld.

Altfeld, Laura F. January 2003 (has links)
Document formatted into pages; contains 46 pages. / Title from PDF of title page. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Herbivore abundances are determined by a set of interacting factors that vary among different habitat types. Specifically, herbivore abundances in monocultures and polycultures may be governed by the same set of factors but with varying influences in the different habitats. In addition, monophagous and polyphagous herbivores may respond differently to the same set of influencing factors. I examined several abiotic and biotic factors in manipulated monocultures and polycultures of Borrichia frutescens in a west central Florida salt marsh. The experimental plots differed in both plant diversity and aboveground habitat structure to see how each component of diversity contributed to variability in the abiotic and biotic factors and how those factors were related to differences in herbivore abundances. The monoculture treatment involved clipping all above ground non-host plant material to achieve a host plant monoculture. The polyculture treatments involved pinning all non-host plant material to achieve a polyculture with reduced above ground habitat structure. The second polyculture treatment was a control in which the naturally diverse plots were unmanipulated. Two monophagous and one polyphagous herbivores were chosen for this study because of their abundance and availability in the field. The two monophagous herbivores on the host plant Borrichia frutescens were Pissonotus quadripustulatus (Homoptera:Delphacidae) and Asphondylia borrichiae (Diptera: Cecidomyiidae) both of which have been well studied in the field where the current experiment took place. The polyphagous herbivore was Cyarda acutissima (Homoptera: Flatidae), a poorly known invasive from Cuba. Soil salinity and host plant leaf nitrogen content were the abiotic factors measured. Herbivore abundances, percent egg and gall parasitism by parasitoids, spider abundances on host plant stems and ground spider abundances were the biotic factors measured. Both salinity and host plant leaf nitrogen were significantly different among the different treatments with clipped plots having the highest salinity and leaf nitrogen content. Population densities of both of the monophagous herbivores were not significantly different between treatments. The polyphagous herbivore had significantly higher abundances in the pinned and control plots than in the clipped plots. Stem spider abundances were not significantly different among treatments. Ground spiders, however, were significantly more abundant in control and pinned plots than clipped plots. Parasitism of both monophagous herbivores was not significantly different between treatments but was generally higher in the control plots. The results suggest that for monophagous herbivores bottom-up and top-down factors act antagonistically in monocultures but for the polyphagous herbivore, the presence of multiple host plants is more influential in diverse plots even given the higher abundances of generalist predators. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.
274

Response of Phytoplankton to Climatic Changes during the Eocene-Oligocene Transition at the North Atlantic ODP Site 612 / Fytoplanktons respons till klimatförändringar under Eocen-Oligocen övergången vid Nordatlanten ODP Site 612

Rivero Cuesta, Lucía January 2015 (has links)
The development of modern glacial climates occurred during the Eocene-Oligocene transition (34 to 35.5 Ma) when a decrease of atmospheric CO2 led to a global temperature fall. The ocean was deeply affected, both in the surface and the deep-sea, suffering a strong reorganization including currents and phytoplankton distribution. Spanning that time, 35 samples from the North Atlantic Ocean Drilling Program Site 612 have been analyzed by counting coccoliths abundance in different size groups (< 4 µm, 4 to 8 µm and > 8 µm) and silica fragments abundance. Absolute coccoliths abundance were estimated with two different methods, the “drop” technique and microbeads calibration. In addition, a fragmentation index was calculated to assess the preservational state of the samples. The results obtained fit in the global picture of a decrease in phytoplankton abundance across theEocene-Oligocene boundary, although coccolith and silica fragments abundances show slight different patterns. Absolute abundances estimates showed a large difference between the “drop” and the microbeads methods. The temperature at which samples are dried seems to affect microbeads distribution, leading to an underestimation at temperatures higher than 60º C. In future work the current dataset will be updated with additional calibration and replicate counts to confirm that the “drop” estimates are the more valid results. As the fragmentation index was fairly constant in all samples, no major differences in nannofossil preservation were inferred. Coccoliths abundance drops are thought to be triggered by global temperature fall, general decrease of atmospheric CO2, changes in oceanic circulation, pulses of nutrients or a combination of those. / Under tidsspannet som täcker övergången mellan eocen och oligocen, för ungefär 35.5 till 34 miljoner år sedan, genomgick jordens klimat en stor förändring. Under eocen hade vår planet ett varmare klimat och var i ett så kallat ”greenhouse state”. Mot slutet av denna period och i början av oligocen skiftade emellertid klimatet till en kallare regim, ett så kallat ”icehouse state”. Under detta tillstånd minskade andelen koldioxid i atmosfären vilket medförde att den globala temperaturen minskade. Vidare påverkades också havet och speciellt de fytoplankton som levde där, då de påverkas av temperatur och inflödet av näringsämnen. Fytoplankton står för en betydande del av jordens pågående fotosyntes samt är basen av den organiska matkedjan. Syftet med denna undersökning är att studera förekomsten av coccoliter, små kalcitplattor som produceras av en typ av nannoplankton som kallas coccolitoforider. Coccoliter från en djuphavskärna härstammande från norra Atlanten har därför samlats in och för-ändringen av mängden fytoplankton över nämnda tidsspann mätts. Vidare har också bitar av kisel från andra växtplankton räknats. Resultatet av denna studie var att båda grupperna var rikligare under den sista delen av eocen men mängden sjönk snabbt i början av oligocen. Det finns inte tillräckligt med information för att reda ut orsakerna av detta, men det är troligt att minskningen i temperatur och CO2-tillgängligheten för fotosyntesen är viktiga faktorer.
275

Factors regulating the population dynamics and damage potential of pollen beetle (Meligethes aeneus F.) on crops of oilseed rape

Tölle, Marie-Luise 12 May 2011 (has links)
No description available.
276

Elninių žvėrių (Cervidae) populiacijų tyrimas Jurbarko rajono savivaldybės teritorijoje / Analysis of deer animals (Cervidae) populations in Jurbarkas district municipality forests

Lingaitis, Linas 21 June 2012 (has links)
Magistro darbe tiriama elninių žvėrių populiacijos Jurbarko rajono savivaldybės teritorijoje. Darbo objektas – Jurbarko rajono savivaldybės teritorijos miškų elniniai žvėrys. Darbo tikslas – Įvertinti Jurbarko rajono savivaldybės teritorijojos elninių žvėrių populiacijų gausos ir tankio dinamiką, kokybę pagal ragus ir sumedžiojimo dinamiką. Darbo metodai – Žvėrių gausos ir sumedžiojimo duomenys paimti iš Aplinkos ministerijos oficialių ataskaitų. Elninių žvėrių vertinimo pagal atrankos grupes metodas. Leidinių, literatūros šaltinių analizės metodas, lyginamosios analizės metodas. Darbo rezultatai – Tyrimo metu nustatyta elninių žvėrių popukiacijos dinamika. Nuo 2008 iki 2011 metų briedžių populiacija padidėjo 32%, taurių elnių – 32%, stirnų – 29%. Visų trijų elninių žvėrių lyčių santykis atitinka mėsinės krypties medžioklės ūkio organizavimo principus. Briedžių populiacija nesudaro mažiausio leistino tankio, todėl medžioklė draudžiama, tauriųjų elnių populiacija viršija ekologinį tankį, todėl tikslinga jų gausą reguliuoti intensyviau, kad nebūtų padaryta didelė žala miškų ir žemės ūkiui, stirnų populiačija artėja prie ekologinio tankio ribos, todėl tikslinga gausą reguliuoti intensyviau. Per praėjusius keturis medžioklės sezonus sumedžiota santykinai daugiau atrankinių tauriųjų elnių patinų, o atrankinių stirninų sumedžiojimas padidėjo net 41%, nei prieš 10 metų. Tauriųjų elnių daugiausiai buvo sumedžiota 5–8 ragais, rugsėjo mėnesį, o stirninų daugiausiai buvo sumedžiota 3–5... [toliau žr. visą tekstą] / In master thesis there were made analyzes about populations of deer animals of Jurbarkas district municipality. Object of work– Deer animals of Jurbarkas district municipality forests. Aim of work– To evaluate dynamic of deer (Cervidae) populations abundance and density in Jurbarkas district municipality forests, quality by horns and entrapment’s dynamic. Research methods– Information of deer abundance and entrapment is collected from official reports of the Ministry of Environment. Deer animals‘ evulation method by selection groups. Publications, literature sources‘ analysis method, comparative analysis method. Results– It was found dynamic of deer animals populations. Population of moose raised by 32 %, red deer – 32 %, roe – 29 % since 2008 until 2011 years. Ratio of all three deer animals sex matches principles of meat hunting organization. Moose hunting is forbidden because of low population. Population of red deer exceeds ecological density so there is necessary to control more intensive to avoid damage in husbandry and forestry. Population of roes is near to the limit of ecological density so there is necessary to control more intensive. There were hunted more selective red deer males. Entrapment of roebucks was increased even by 41% during 10 years. Much of red deers were hunted with 5-8 horns in Septembers. Most of hunted roebucks had 3-5 horns and entrapment is almost identic every month of hunting season.
277

Interactions between Chaoborus spp. and Mysis relicta and their impact on pelagic crustacean zooplankton in mesocosms at the Experimental Lakes Area

Seckar, Dalila 13 April 2009 (has links)
The objectives of this study were: 1) to compare and contrast the effects of variations in natural densities of two common freshwater predators of crustacean zooplankton, Chaoborus spp. and Mysis relicta; and 2) to determine whether the combined impacts of these predators together differed from their effects when alone. In deep (>10m) mesocosms, additions of Chaoborus and Mysis at natural densities did not result in large changes in zooplankton abundances, lengths, or biomass. Significant decreases in abundance were observed only for Bosmina longirostris and Daphnia spp. In small (~20L) enclosures, higher predator densities caused zooplankton declines over three days. Strong interactive effects between Chaoborus and Mysis were not detected in either the large or small enclosures. This suggests that the combined effects of these two predators can be predicted from their effects determined in isolation.
278

Ilgalaikio supaprastinto žemės dirbimo ir tiesioginės sėjos įtaka žieminių kviečių agrocenozei / Effects of long-term reduced tillage and direct seeding on winter wheat agrocenoses

Baltrušaitytė, Ernesta 13 June 2012 (has links)
Magistrantūros studijų baigiamajame darbe pateikiami ilgalaikio supaprastinto žemės dirbimo ir tiesioginės sėjos įtaka žieminių kviečių agrocenozei tyrimo rezultatai. Darbo objektas – pagrindinio žemės dirbimo būdai žieminiams kviečiams. Darbo metodai: buvo tirti tokie žemės dirbimo būdai: 1) įprastinis arimas 23–25 cm gyliu; 2) seklusis arimas 12–14 cm gyliu; 3) gilusis purenimas 23–25 cm gyliu; 4) seklusis purenimas 12–15 cm gyliu; 5) tiesioginė sėja į neįdirbtą dirvą. Atlikti šie stebėjimai: Dirvos agrocheminių savybių nustatymas, piktžolėtumo nustatymas, žieminių kviečių daigų tankumas, sliekų kiekis dirvoje, produktyvių stiebų tankumas, derliaus apskaita, bei 1000 grūdų masė. Darbo rezultatai. Nustatyta, kad tiesioginė sėja, bei gilusis purenimas esmingai padidino trumpaamžių piktžolių daigų tankumą žieminių kviečių pasėlyje, o taikant seklaus purenimo būdą esmingai padidėjo daugiamečių piktžolių daigų tankumas lyginant su įprastai suarta dirva. Žieminių kviečių vegetacijos pabaigoje esmingai padidėjo daugiamečių piktžolių masė sekliai artuose, giliai purentuose ir sekliai purentuose laukeliuose, lyginant su įprastiniu arimu. Įprastinį arimą pakeitus giliu purenimu, sekliu purenimu ir tiesiogine sėja į neįdirbtą dirvą, atsinaujinus žieminių kviečių vegetacijai nustatyta esmingai didesnis dirvinio garstuko daigų tankumas. Taikant ilgalaikę tiesioginę sėją žieminių kviečių vegetacijos pabaigoje nustatyta esmingai didesnis paprastosios rietmenės daigų skaičius ir masė... [toliau žr. visą tekstą] / Master's thesis presents the results of the investigation of effects of long-term reduced tillage and direct seeding on winter wheat agrocenoses. Object of work – are the main methods of tillage for winter wheat. Research methods: the following tillage methods were investigated: 1) conventional ploughing at the depth of 23–25 cm, 2) shallow ploughing at the depth of 12–14 cm, 3) deep loosening at the depth of 23–25 cm, 4) shallow loosening at the depth of 12–15 cm; 5) direct seeding into uncultivated soil. The following sampling were performed: soil agrochemical properties, weed abundance, winter wheat seedling density, quantity of earthworms in soil, productive stems density, yield and 1000 grain weight. Results. It was found that direct seeding and deep loosening substantially increased the annual weed seedling density of winter wheat crop, while the shallow method of loosening significantly increased weed seedling density compared to normal ploughing soil. The mass of perennial weeds has increased substantially at the end of the winter wheat growing season in shallow ploughing, deeply loosened and shallow ploughing plots compared to conventional ploughing. When normal ploughing was replaced with deep loosening, shallow loosening and direct seeding in the uncultivated soil after the recurrence of winter wheat vegetation, the density of Sinapis arvensis L. shoots increased significantly. When applying long-term direct seeding at the end of winter wheat growing season, the... [to full text]
279

Interactions between Chaoborus spp. and Mysis relicta and their impact on pelagic crustacean zooplankton in mesocosms at the Experimental Lakes Area

Seckar, Dalila 13 April 2009 (has links)
The objectives of this study were: 1) to compare and contrast the effects of variations in natural densities of two common freshwater predators of crustacean zooplankton, Chaoborus spp. and Mysis relicta; and 2) to determine whether the combined impacts of these predators together differed from their effects when alone. In deep (>10m) mesocosms, additions of Chaoborus and Mysis at natural densities did not result in large changes in zooplankton abundances, lengths, or biomass. Significant decreases in abundance were observed only for Bosmina longirostris and Daphnia spp. In small (~20L) enclosures, higher predator densities caused zooplankton declines over three days. Strong interactive effects between Chaoborus and Mysis were not detected in either the large or small enclosures. This suggests that the combined effects of these two predators can be predicted from their effects determined in isolation.
280

Sampling methods in Northwest Coast household archaeology: a simulation approach using faunal data from the Ozette site

Gray, Brendan S. 27 January 2009 (has links)
The methodological and theoretical considerations that must be addressed when excavating the traditional longhouses of the First Nation peoples who lived in the Pacific Northwest region are the foci of this thesis. The large amount of faunal data contained within the remains of houses require the use of explicit, justifiable sampling strategies; however, the methods used to sample these dwellings are not generally a central research focus. A sampling simulation of faunal data recovered from the excavation of numerous houses from the village site of Ozette is the empirical basis of this research. Specifically, the effects of sample size and sample method on richness, relative abundance and the interpretation of status using faunal data are investigated. The results are of heuristic value for future household archaeology on the Northwest Coast and suggest alternative sampling methods which attempt to cope with the labour-intensive research generally required for shell-midden archaeology.

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