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Dissertations / Theses on the topic 'Species importance'
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Bell, Claire L. "The measurement of radical species of atmospheric importance." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:14933fc6-5272-45b0-a281-6da35c6e42e8.
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The measurement of radical species in the atmosphere has far reaching implications. For example, it is necessary to both understand and improve our knowledge of radicals in the atmosphere to better inform the models which in many cases are the best way of predicting future air quality and climate change. Although many of these models are often not fully representative of all the processes occurring, they are the current best estimate based on the knowledge available, and can be useful in informing and directing future policy. The numerous, varied and interlinked cycles in the atmosphere are complex and only by obtaining data on specific species can accurate concentrations be retrieved and fed back into the models to improve their accuracy. This work is concerned with the development and application of an ultrasensitive absorption spectroscopy technique to the problem of detection of the peroxy radical, HO₂. Noise Immune Cavity Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS) combines cavity enhancement techniques (in order to increase the path length) with frequency and wavelength modulation techniques (in order to reduce the noise). Following a discussion of the current detection methods used by atmospheric scientists to accurately measure and quantitative concentrations, some preliminary work on the detection of ammonia by a simple cavity enhanced absorption setup is presented. Pressure broadening and shift results were obtained for a number of ammonia transitions in the near infrared region, broadened by He, Ne, Ar, Xe, O₂ and N₂. The bulk of the work concentrates on the implementation of the NICE-OHMS technique, presenting the first results with the use of an external cavity diode laser and a ring shaped cavity. A sensitivity of 4 x 10⁻¹¹ cm⁻¹ Hz⁻<sup>1/2</sup> is obtained on an individual rovibrational transition of methane at 6610.063 cm⁻¹, along with a selection of other data from the atmospherically important molecules methane, nitrogen dioxide and carbon dioxide, highlighting the broad wavelength range over which the instrument can operate. Finally, the NICE-OHMS technique is used to probe HO₂ radicals formed through the photolysis of a Cl₂/CH₃OH/O₂ mixture. Following the creation and detection of HO₂ radicals in the cavity, and based on the optimum sensitivity outlined above, a minimum concentration of 1 x 10⁹ molecules cm⁻³ has been demonstrated.
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Heard, Anne C. "Gas-phase reactions of halogen species of atmospheric importance." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293474.
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Hiley, Jonathan Richard. "The importance of protected areas for species undergoing distribution changes." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18782/.
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The value of Protected Areas for wildlife will diminish if the species for which they were originally designated are pushed out of their boundaries by changing temperatures, or if they are infiltrated by invasive species that are harmful to native species. Here, I assess the performance of Protected Areas against this background of distributional change. I found that Protected Areas have facilitated the range expansions of the six wetland bird species that have recently colonised the UK, both as sites at which breeding first occurs and as locations where substantial populations can establish before spreading to unprotected land. In contrast, non-native species did not initially ‘invade’ Protected Areas, but subsequently colonised them as their populations grew. I complemented this analysis with a field research project in a Mexican Biosphere Reserve. Here, Strictly Protected Areas were resistant to non-native species (as in the UK), and important for species undergoing global population declines. However, partially-protected locations with habitat modification provided opportunities for both non-natives and native generalists. Consequently, modified areas were characterised by higher local-alpha diversity than relatively natural areas, although they contained relatively similar suites of species across different biogeographical zones. Thus, evaluating the impact of Protected Areas depended on the metric of biodiversity change considered, and on the level of protection. Similar patterns were revealed on a global scale (considering 118 countries). Range expansions (colonisations and introductions) have outpaced countrywide extirpations over the last two centuries, resulting in a c.4% average net increase in national breeding bird avifaunas, even though gamma- and beta-diversity have decreased. Protected Areas may have promoted ‘beneficial’ change in this context; there were more colonisations and fewer extirpations in countries with more protected land. Protected Areas will remain crucial as a part of future conservation strategies to protect biodiversity in an era of increasing distributional dynamism.
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Wagner, Kirtsen. "Laboratory studies of halogen-containing and organic species of atmospheric importance." Thesis, University of Oxford, 2003. https://ora.ox.ac.uk/objects/uuid:f6009882-ad3e-4627-848d-1042c7d5e72a.
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This thesis describes laboratory studies of the kinetics of some reactions of atmospheric significance. The species of interest were Cl atoms, IO radicals and several organic compounds. In particular, the chemistry of acetone and the acetonylperoxy radical was investigated. These species are of importance in the troposphere and the stratosphere, where they may influence the concentrations of HO<sub>x</sub>, NO<sub>x</sub> and O<sub>3</sub>. The experiments were performed using low-pressure discharge-flow tubes coupled to a variety of detection techniques, including conventional methods such as resonance fluorescence (RF) and electron-impact mass spectrometry (EEVIS). However, much of the thesis is concerned with the development of techniques that offer a greater sensitivity and selectivity, namely, laser-induced fluorescence (LIF) and chemical-ionization mass spectrometry (CIMS). The reactions of Cl atoms with acetone and butanone were monitored with Cl RF. The study of the former reaction was extended in order to obtain information about the chemistry of the acetonylperoxy radical. IO was observed with LIF. This work involved the first reported coupling of IO LIF to a discharge-flow tube. The system was shown to be a suitable method by which to study reactions of IO. The results of these investigations demonstrate that reaction with Cl and IO may be an important sink for several organic compounds in the marine boundary layer. The design, construction and commissioning of the EIMS system is described. The apparatus was used in an attempt to follow the self-reaction of the acetonylperoxy radical by monitoring the products. The complications that arose during the study illustrated the need for a more versatile form of MS. It was decided to convert the instrument to a CMS system that would allow direct observation of the peroxy radical. The construction of two ion sources, one employing a cartridge of polonium-210 and the other a simple discharge, as well as an electrostatic ion guide, is described. The discharge source was shown to be better suited to the low-pressure conditions.
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Sanon, Hadja Oumou. "The importance of some Sahelian browse species as feed for goats /." Uppsala : Dept. of Animal Nutrition and Management, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200784.pdf.
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D'Souza, Richard Joseph. "The importance of reactive oxygen species in determining mesangial cell growth." Thesis, St George's, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283240.
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Forgus, Juan-Jacques. "Functional importance of snakes in a strandveld ecosystem." University of the Western Cape, 2018. http://hdl.handle.net/11394/6449.
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Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv & Cons Biol)<br>Gaps in our knowledge of the functional roles of snakes within ecosystems limit our ability to
predict the potentially cascading effects their removal from an ecosystem might create.
Extirpation of snake species could potentially result in losses of ecosystem functionality if
those taxa are ecologically unique. I used pitfall and funnel trap arrays, artificial cover object
surveys, active searching, and passive camera trapping, as well as pre-existing faunal diversity
data to identify terrestrial tetrapod species within the Koeberg Private Nature Reserve. This
resulted in a list of 265 species, of which 13 were snakes. I then gathered data on dietary and
four additional functional traits for each species from the literature. Next, using hierarchical
and partitioning around medoids clustering, I identified ten broad dietary guilds and 54
functional guilds within the terrestrial tetrapod community. Of the dietary guilds Dasypeltis
scabra was the only snake species that formed a unique single species guild and was one of
four snake species (Pseudaspis cana, Homoroselaps lacteus and Lamprophis guttatus) to form
four unique single species functional guilds. The remaining snakes clustered together within
groups of other vertebrate predators. Functional diversity analysis was then used to simulate
losing eight major taxonomic groups (birds, passerines, non-passerines, mammals, reptiles,
snakes, non-snake reptiles and amphibians) and gauge the effects of those losses on overall
community dietary and functional diversity. Functional diversity analysis revealed that the loss
of certain snake species resulted in disproportionate losses of overall community dietary and
functional diversity while losing others had negligible effects. These findings provide
ambivalent support for the dietary and functional uniqueness of snakes suggesting that certain
snake species are fulfilling unique functional roles within the ecosystem. Additionally, it is
likely that losing those non-redundant species would result in significant losses of ecosystem
functionality.
8
Flugge, Mark. "Laboratory studies of reactions of nitrate radicals with species of atmospheric importance." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413082.
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Green, Timothy J. "A study of chlorine oxide species of potential importance in the stratosphere." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390458.
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Jackson, Emma Louise. "Importance of seagrass beds as a habitat for fishery species around Jersey." Thesis, University of Plymouth, 2003. http://hdl.handle.net/10026.1/521.
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Ware, Suzanne Jane. "The importance of inshore areas on the west coast of Scotland as nursery grounds for commercially important fish species." Thesis, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422344.
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Mangan, Scott A. "Importance of the species composition of arbuscular mycorrhizal fungi to tropical tree seedlings." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3243802.
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Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2007.<br>Title from PDF t.p. (viewed Nov. 18, 2008). Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 6842. Adviser: James D. Bever.
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Kamenos, Nicholas Andreas. "The importance of maerl grounds as nursery areas for commercially important species with emphasis on the Queen scallop (Aequipecten operucularis)." Thesis, University of London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407672.
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Pigott, David Michael. "Mapping the global distribution of zoonoses of public health importance." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:962dc1a7-c6c1-4878-ab6f-94dcebf7b1e1.
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Medical cartography can provide valuable insights into the epidemiology and ecology of infectious diseases, providing a quantitative representation of the distribution of these pathogens. Such methods therefore provide a key step in informing public health policy decisions ranging from prioritising sites for further investigation to identifying targets for interventions. By increasing the resolution at which risk is defined, policymakers are provided with an increasingly informed approach for considering next steps as well as evaluating past progress. In spite of their benefits however, global maps of infectious disease are lacking in both quality and comprehensiveness. This thesis sets out to investigate the next steps for medical cartography and details the use of species distribution models in evaluating global distributions of a variety of zoonotic diseases of public health importance. Chapter 2 defines a methodology by which global targets for infectious disease mapping can be quantitatively assessed by comparing the global burden of each disease with the demand from national policymakers, non-governmental organisations and academic communities for global assessments of disease distribution. Chapter 3 introduces the use of boosted regression trees for mapping the distribution of a group of vector-borne diseases identified as being a high priority target, the leishmaniases. Chapter 4 adapts these approaches to consider Ebola virus disease. This technique shows that the West African outbreak was ecologically consistent with past infections and suggests a much wider area of risk than previously considered. Chapter 5 investigates Marburg virus disease and considers the variety of different factors relating to all aspects of the transmission cycle that must be considered in these analyses. Chapters 6 and 7 complete the mapping of the suite of viral haemorrhagic fevers by assessing the distribution of Crimean-Congo haemorrhagic fever and Lassa fever. Finally, Chapter 8 considers the risk that these viral haemorrhagic fevers present to the wider African continent, quantifying potential risk of spillover infections, local outbreaks and more widespread infection. This thesis addresses important information gaps in global knowledge of a number of pathogens of public health importance. In doing so, this work provides a template for considering the global distribution of a number of other zoonotic diseases.
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Schneider, Lea Dominique. "Conservation ecology of the thick-shelled river mussel Unio crassus : The importance of parasite-host interactions." Doctoral thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-47636.
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Unionoid mussels are globally threatened and their conservation requires species-specific knowledge on their ecology and parasite-host interaction. Unio crassus is one of Europe’s most threatened unionoid species and has a temporary obligate parasitic life stage (glochidia) on fish. A lack of suitable hosts is probably a major limitation for mussel recruitment, but host species composition, suitability and availability in time and space have yet to be fully explored. This thesis examines different aspects of the host fish species, including their composition, suitability and ecological importance, in relation to U. crassus, using both field and laboratory studies. The effects of mussel and host density on mussel reproductive potential were considered, as were aspects of evolutionary adaptations between mussels and fish and how climate change may affect their interaction. The results show that U. crassus is a host generalist, parasitizing a variety of fish species. Host suitability and density, which varied among fish species and rivers, affected the level of glochidia encapsulation, hence mussel reproductive potential, more so than the density of mussels taking part in reproduction. Ecologically important hosts included both highly suitable primary hosts, and less suitable hosts that were highly abundant. Whether or not U. crassus has specific adaptations to its hosts to enhance juvenile transformation remains unclear. No distinct pattern of local adaptation was found, nor was there an effect of host fish presence on the timing of glochidia release by adult mussels. Instead, temperature played a major role, with results suggesting that changes in spring water temperature regimes can cause temporal and spatial mismatches in the mussel-host interaction. This thesis indicates that investigations of local mussel-host interactions help in identifying mechanisms important for unionoid conservation management and prioritization.<br>Många sötvattenmusslor har en komplex livscykel där larverna (glochidier) under sin utveckling till frilevande musslor parasiterar på gälarna hos lämpliga värdfiskar. Flera av våra musslor, såsom den tjockskaliga målarmusslan (Unio crassus), är globalt hotade och för att kunna bevara och förvalta dessa arter på bästa sätt behöver vi lära oss mer om deras ekologi och samspelet mellan musslan och dess värdfiskar. Avsaknaden av värdfiskar innebär förmodligen en stor begränsning för rekryteringen av juvenila musslor, men det finns trots detta en begränsad kunskap om hur artsammansättningen i fisksamhället och dess tillgänglighet påverkar musselpopulationer. Min avhandling undersöker olika aspekter av interaktioner mellan U. crassus och dess värdfiskar, som hur värdfisksamhällen och fiskarters värdlämplighet påverkar musslans reproduktionspotential. Jag har även studerat hur tätheter av olika fiskarter och vuxna musslor påverkar rekryteringen, eventuella evolutionära anpassningar samt om en förhöjd temperatur skulle kunna påverka interaktionen mellan U. crassus och dess värdfiskar. Resultaten visar att U. crassus är en generalist som parasiterar på en mängd olika fiskarter. Jag fann dock en stor variation i dominerande fiskarter och lämpliga värdar mellan olika åar, vilket påverkade reproduktionspotentialen hos musslorna mer än vad tätheten vuxna musslor som deltog i reproduktionen gjorde. Som ekologiskt viktiga värdar fanns således både särskilt lämpliga, primära värdarter, men också mindre lämpliga arter som förekom i höga tätheter. Ingen tydlig lokal anpassning kunde observeras, och fiskens närvaro påverkade inte tidpunkten för när de vuxna musslorna släppte sina glochidielarver. Däremot fann jag att temperaturen spelade en viktig roll för musslans reproduktion, där ökad temperatur föreslås ha negativa effekter på interaktionen mellan musslan och dess värdfiskar. Avhandlingen visar på vikten av att studera interaktioner mellan den tjockskaliga målarmusslan och dess värdar på lokal skala för att bättre kunna identifiera och prioritera viktiga naturvårdsåtgärder.<br>UnioCrassusforLIFE (European LIFE+ project: LIFE10 NAT/SE/000046)
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Keller, Michael. "The importance of seed source in programmes to increase species diversity in arable systems /." Zürich, 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13117.
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Beattie, Sally Heather. "Incidence and importance of Bacillus species in raw milk and in the dairy environment." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363155.
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Gray, Alicia E. "Importance and Spatial Distribution of Phytophthora Ramorum Host Species in a Coast Redwood Forest." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500168/.
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Phytophthora ramorum, an exotic forest pathogen known as ‘sudden oak death’ (SOD), has received considerable attention in recent years because of its effects on vegetation structure, composition, and fire disturbance regimes in western U.S. coastal forests. This research examines differences in the importance (e.g., density, dominance, and frequency) and distribution of five host species of P. ramorum–– Umbellularia californica (California bay laurel), Quercus agrifolia (coast live oak), Pseudotsuga menziesii (Douglas fir), Sequoia sempervirens (Coast redwood), and Arbutus menziesii (Madrone)––in Soquel, California. A stratified random sampling design was used to select 66 plots surrounding a managed forest edge in Soquel Demonstration State Forest. Vegetation measurements were conducted in summer 2013. In each plot, all trees ≥3 cm diameter at breast height (DBH) were identified to species, counted, and DBH, height, and canopy position measured. Leaf area index (LAI) of bay laurel was measured to quantify the amount of leaves available for pathogen dispersal with a LiCOR 2200 Plant Canopy Analyzer. In addition, morning (9:00 am) and afternoon (1:00 pm) photosynthetically active radiation (PAR) were quantified using a quantum light sensor. This paper examines the influence of environmental variables, including distance to edge, aspect, slope, and light availability on host species spatial patterns in Soquel, CA. Studying P. ramorum host pattern and importance among managed forest edges is critical for determining hotspots most susceptible to infection and spread, thus relevant for implementing control measures.
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Rosendale, Andrew J. "Importance of Facilitative Urea Transporters in Anuran Osmoregulation." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1313089167.
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Bovy, Helene C. "Understanding and predicting impacts of invasive species : the importance of intraspecific variation and interspecific interactions." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680498.
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Biological invasions continue to alter the structure and functioning of ecosystems worldwide. While the vectors and pathways of establishment of Invasive species are understood, predicting the ecological changes, or impacts, these species can exert on recipient ecosystems is lacking. Using invasive freshwater amphipods as models, this thesis aimed to investigate the role of intraspecific variation and interspecific interactions in understanding and predicting invasive species' impacts. This work first looks at the inherent variation in feeding behaviour within and between populations of an invasive amphipod, and discusses the implications of such variation for the use of functional responses, or the relationship between feeding rate and prey density. in invasion ecology. Secondly, behaviours associated to dispersal and impacts, as well as parasitic profiles, are compared between two UK populations of Dikerogammarus villosus. Differences between the populations show that monitoring population level differences, including behaviour and parasitism, can inform on invasive species' spread and impacts. Thirdly, interspecific interactions are used in order to elucidate the potential impac s of Dikerogammarus haemobaphes. Two aspects in particular are highlighted: predator-prey interactions, using the comparative functional response framework, and interference competition with D. villosus in terms of habitat use. Finally. cross-ecosystem interspecilic interactions are considered and their effects on a critical ecological process: leaf litter degradation. Using two invasive/native plant pairings, the individual leaf shredding abilities of an invasive and a native amphipod are compared in a laboratory setting. While both native plant species were consumed more readily, no difference was detected between the two amphipods. However, an in situ leaf litter bag experiment showed that the indirect effect of the invasive amphipod on macroinvertebrate community diversity may modify the degradation of certain plant species. This thesis therefore provides empirical evidence of the importance of intraspecific variation and interspecific interactions for the furthering predictive ecology
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Massey, Daniel J. "Determining the Clinical Importance of an Unknown Species of Scorpion (Centruroides) Collected in New Mexico." The University of Arizona, 2010. http://hdl.handle.net/10150/623753.
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Class of 2010 Abstract<br>OBJECTIVES: To determine the clinical significance of a population of scorpions, C. sculpturatus, found in New Mexico. This includes the toxicity of the venom as well as the interactions of venom and antivenom.
METHODS: This project will include a descriptive retrospective study of clinical and laboratory data obtained through a patient chart and analytical laboratory procedures to positively identify the species of scorpion responsible for the envenomation.
Scorpion Collection Scorpions from the location of the reported sting will be collected for venom analysis. Specific details and directions will be obtained from the grandparent of the victim regarding the campsite at Caballo Lake State Park.
Human Subject – N/A
Sample Size The sample size of specimens needed should be a minimum of 50 scorpions. This is due to factors which include; extremely small volumes of venom produced by each individual, the possibility of no venom production, damaged telson during collection (anatomical feature used in the delivery of venom), size variation in specimens and short window of opportunity to collect. Since these scorpions are more active during summer months, and travel time must also be accounted for, only a few months a year are acceptable.
Instrumentation and Variables This is primarily laboratory assays rather than clinical. The clinical aspect, a case study involving the victim of a scorpion envenomation, was the reason behind needing to identify this Centruroides species. The analytical laboratory findings will be what will determine the exact species of Centruroides.
A number of laboratory instrumentations and tests will be used or performed. These include; sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), SDS-PAGE with hyaluronic acid, turbidimetric absorbances of hyaluronidase, reverse phase high pressure liquid chromatography (RPHPLC), enzyme-linked immunosorbent assay (ELISA), lethal dose 50 (LD%) and effective dose 50 (ED50).
Variables regarding these findings will include two main factors; the human factor and the instrumentation factor. First the human factor, samples collected must remain free of contaminants up to the point of analysis. The instruments
RESULTS: 104 specimens were collected at Caballo Lake State Park. Four of these specimens were sent to a taxonomist and identified as C. sculpturatus.
SDS-PAGE, turbidimetric HA, and RPHPLC showed no significant difference in venom between the New Mexico and Arizona Centruroides, but did show a significant difference between these two groups and the Mexico Centruroides. SDS-PAGE/HA and ELISA assays showed no significant differences between groups.
LD50 and ED50 data were similar between New Mexico and Mexico Centruroides, both being more potent and more readily reversed by antivenom than the Arizona Centruroides.
CONCLUSIONS: The assays which show possible differences between species, SDS-PAGE, SDS-PAGE-HA, turbidimetric HAase, RPHPLC, and ELISA were all identical between the New Mexico Centruroides species and the Arizona Centruroides sculpturatus. These findings were opposite when comparing New Mexico Centruroides species and the Mexico Centruroides limpidus limpidus. Three of the five assays showed a significant difference. Since the Mexico Centruroides limpidus limpidus is a known different species, this was expected. With this data the scorpion specimens collected in New Mexico have been identified as Centruroides sculpturatus.
An interesting difference between the New Mexico and Arizona Centruroides sculpturatus was toxicity of the venom. The New Mexico groups had close to a two fold increase in toxicity. In fact, the toxicity of the New Mexico groups was equivalent to the Mexico Centruroides limpidus limpidus which is well documented as having an increased toxicity.
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Tavares, Joana Flor R. "Assessing the importance of biological uncertainties to the control of species introductions via ballast water /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 90 p, 2009. http://proquest.umi.com/pqdweb?did=1654487631&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Löfqvist, Zandra. "The importance of vegetation height and flower abundance for Swedish butterfly species in semi-natural grasslands." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-108670.
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Changed management of semi-natural grasslands is thought to be one important factor for explaining the decline of butterfly populations in Sweden and the rest of Europe. This study explores how vegetation height, variation in vegetation height and flower abundance can help predict the occurrence of butterfly species in semi-natural grasslands in southern Sweden. My study is based on data collected by a national environmental monitoring programme (NILS) during 2006-2010. Generalized linear models showed that all three explanatory variables significantly affected 26 of the 41 species of butterflies studied. The study also investigated preferences for three different systems for grouping species but did not find differences among groups. Several of the species would most likely benefit from variation in grazing pressure or rotational grazing as well as flower-rich grasslands. The results may also help when aiming management at the preservation of individual species.
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Saito, Naoki. "Studies on CD1d-NKT system conserved among species : importance of primate models for human disease analysis." Kyoto University, 2007. http://hdl.handle.net/2433/136438.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(人間・環境学)<br>甲第13167号<br>人博第374号<br>新制||人||91(附属図書館)<br>18||D||175(吉田南総合図書館)<br>UT51-2007-H440<br>京都大学大学院人間・環境学研究科相関環境学<br>(主査)教授 小松 賢志, 助教授 三浦 智行, 助教授 倉橋 和義<br>学位規則第4条第1項該当
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Fondom, Nicolas Yebit. "PHYSIOLOGICAL AND BIOCHEMICAL ADAPTATIONS IN SOME CAM SPECIES UNDER NATURAL CONDITIONS: THE IMPORTANCE OF LEAF ANATOMY." Oxford, Ohio : Miami University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1260552594.
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Maire, Eva. "Socio-ecological drivers of fish biomass on coral reefs : the importance of accessibility, protection and key species." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG027/document.
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Les récifs coralliens hébergent la plus grande biodiversité sur Terre et fournissent la nourriture, le revenu économique, la protection côtière et les valeurs culturelles pour des millions de personnes. L'accessibilité des écosystèmes via les réseaux routiers est un déterminant majeur de leurs conditions, les écosystèmes les plus accessibles étant les plus menacées. Longtemps, l’estimation de l'accessibilité par l’Homme s’est limitée à l'utilisation de la distance linéaire qui ignore l’irrégularité des côtes maritimes et les réseaux routiers, facteurs influençant le temps nécessaire pour atteindre les lieux de pêche. Cette thèse présente un double enjeu : (i) développer des indices d'accessibilité intégrant l’hétérogénéité du milieu marin pour quantifier les impacts humains sur les récifs ; (ii) évaluer l'importance de ces nouveaux indices, en interaction avec les mesures de protection, pour expliquer les variations de la biomasse de poissons. Dans un premier temps, j’ai caractérisé la proximité des hommes aux récifs, en tenant compte des surfaces rencontrées (routes, chemin, eau) qui influencent le temps de trajet jusqu’aux récifs. Le temps de trajet a permis de calculer un indice de gravité, défini comme la population humaine divisée par le temps de trajet au carré, pour évaluer le niveau de pression humaine de n'importe quel récif au monde. J'ai trouvé que le temps de trajet et la gravité sont des déterminants majeurs de la biomasse de poissons à l’échelle globale. Dans un second temps, trois applications utilisant ces nouveaux indices ont permis de montrer que (i) la gravité permet de révéler l’efficacité des actions de conservation : les réserves placées là où les impacts humains sont modérés à forts fournissent des gains de conservation élevés pour la biomasse de poissons, mais elles sont peu susceptibles de protéger les prédateurs supérieurs, qui sont uniquement présent dans les réserves soumises à de faibles impacts humains ; (ii) en utilisant un cas d'étude réalisé dans le Nord-Ouest de Madagascar, j'ai illustré comment la proximité du marché peut affecter les communautés de pêcheurs et, finalement, engendrer des changements dans l'exploitation des ressources marines ; (iii) j’ai développé une nouvelle approche, le Community-Wide Scan (CWS), pour identifier les espèces de poissons qui contribuent de manière significative à la biomasse et à la couverture corallienne des récifs de l’Indopacifique, celles-ci pouvant constituer des espèces cibles à protéger. Dans le contexte de changements globaux et de perte de biodiversité, la mesure d’accessibilité constitue un outil puissant et permet de relancer le défi de gestion durable et efficace des socio-écosystèmes coralliens<br>Coral reefs have the greatest biodiversity of any ecosystem on the planet and support ecosystem goods and services to million people who depend directly on them for food, economic income, coastal protection and cultural values. Ecosystem accessibility, through road networks, is the main driver of their conditions, with the most accessible ecosystems being most at risk of resource depletion. To date, measuring accessibility to humans was strictly limited to examining the linear distance which ignores ragged coastlines and road networks that can affect the time required to reach fishing grounds. This thesis presents a double challenge: (i) developing new metrics of accessibility that account for seascape heterogeneity to better assess human impacts on coral reefs; (ii) evaluating the importance of coral reef accessibility, in interactions with their management, to explain variations of fish biomass. First, I developed novel metrics of reef proximity to human populations and markets based on the friction distance which is related to transport surfaces (paved road, dirt road, water) influencing the effective reach of human settlements. Travel time was used to build the gravity index, defined as human population divided by the squared travel time, to assess the level of human pressure on any reef of the world. I found that both travel time and gravity are strong predictors of fish biomass globally. Second, three applications using these new metrics highlighted that (i) gravity identified critical ecological trade-offs in conservation since reserves placed with moderate-to-high impacts may provide substantial conservation gains for fish biomass while reserve locations with low human impacts were more likely to support higher-order predation, (ii) using a study case in Northwest Madagascar, I illustrated how market proximity can affect fishermen communities and, ultimately, trigger changes in marine resources exploitation, and (iii) I implemented a new Community-Wide Scan (CWS) approach to identify fish species that significantly contribute to the biomass and coral cover on Indo-Pacific reefs and which provided tractable conservation targets. Within the context of global changes and biodiversity loss, the thesis challenges the sustainable and efficient management of coral reef socio-ecological systems with accessibility being the cornerstone
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Abubakar, Mohamed Rania. "Tracing a compound with ecological importance for Ficus species and profiling the chemical constituents of Ficus obtusifolia." Thesis, Uppsala universitet, Avdelningen för farmakognosi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-434985.
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Francis, Matthew D. "Interspecific Competition Between Hygrophila polysperma and Ludwigia repens, Two Species of Importance in the Comal River, Texas." Thesis, University of North Texas, 1999. https://digital.library.unt.edu/ark:/67531/metadc278133/.
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Hygrophila polysperma is a plant native to Asia that has been introduced into the Comal River, TX and is thriving while Ludwigia repens, a species native to the river appears to be declining. Both plants have similar morphologies and occupy similar habitats in the river. Two plant competition experiments were conducted to examine the competitive interactions between the two species. First, an experimental design was developed in which established Ludwigia plants were 'invaded' by sprigs of Hygrophila to determine if established Ludwigia populations would be negatively impacted by invasion. The second experiment focused on establishment and growth of sprigs of each species under three competition scenarios. Results show that the continued growth of well-established Ludwigia plants was significantly depressed by the invasion of Hygrophila in comparison with those that had not been invaded. Furthermore, the growth of Hygrophila sprigs was uninhibited by the presence of Ludwigia, but the presence of Hygrophila negatively impacted the growth of Ludwigia sprigs. There was no difference in the growth of Hygrophila sprigs whether planted alone, with Ludwigia sprigs or even if planted into stands of established Ludwigia.
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Lidén, Marlene. "Restoration of endangered epiphytic lichens in fragmented forest landscapes the importance of habitat quality and transplantation techniques /." Umeå : Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 2009. http://epsilon.slu.se/200982.pdf.
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Nghidinwa, Kirsti C. "Why are some species invasive? : determining the importance of species traits across three invasion stages and enemy release of southern African native plants in New Zealand." Lincoln University, 2009. http://hdl.handle.net/10182/1438.
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There are many factors that have been proposed to contribute to plant invasiveness in nonnative ecosystems. Traits of invading species are one of them. It has been proposed that successful species at a certain invasion stage share particular traits, which could be used to predict the behaviour of potentially invasive plants at the respective stage. Three main stages of invasion are distinguished: introduction, naturalization, and invasion. I conducted a stageand trait-based analysis of available data for the invasion of New Zealand by the flora of southern Africa. Using 3076 southern African native vascular plant species introduced into New Zealand, generalised linear mixed model analysis was conducted to assess association of several species traits with the three invasion stages. The results showed that plant traits were significantly associated with introduction but fewer traits were associated with naturalization or invasion, suggesting that introduction can be predicted better using plant traits. It has been also hypothesized that species may become invasive in non-native ecosystems because they are removed from the regulatory effects of coevolved natural enemies (Enemy Release hypothesis). A detailed field study of the succulent plant Cotyledon orbiculata var. orbiculata L. (Crassulaceae) was conducted in the non-native New Zealand and native Namibian habitats to compare the extent of damage by herbivores and pathogens. C. orbiculata is a southern African species that is currently thriving in New Zealand in areas seemingly beyond the climatic conditions in its native range (occurring in higher rainfall areas in New Zealand than are represented in its native range). As hypothesised, C. orbiculata was less damaged by herbivores in New Zealand but, contrary to expectation, more infected by pathogens. Consequently, the plant was overall not any less damaged by natural enemies in the non-native habitat than in its native habitat, although the fitness impacts of the enemy damage in the native and invaded ranges were not assessed. The results suggest that climatic conditions may counteract enemy release, especially in situations where pathogens are more prevalent in areas of higher rainfall and humidity. To forecast plant invasions, it is concluded that species traits offer some potential, particularly at the early stage of invasion. Predicting which introduced plants will become weeds is more difficult. Enemy release may explain some invasions, but climatic factors may offset the predictability of release from natural enemies.
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Verschuyl, Jacob Pieter. "Biodiversity potential in the Pacific and Inland Northwest the relative importance of forest structure and available energy in driving species diversity /." Diss., Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/verschuyl/VerschuylJ0507.pdf.
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Ennis, Courtney. "Spectroscopic identification of complex species containing water and ammonia and their importance to icy outer solar system bodies." University of Western Australia. Chemistry Discipline Group, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0110.
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[Truncated abstract] This thesis examines the bonding interactions and chemical processes associated with irradiated water (H2O) and ammonia (NH3) molecules. The experiments conducted in the present study are designed to replicate the surface chemistry of outer Solar System bodies, particularly the icy surfaces of Saturn's inner moons. Infrared (IR) spectroscopy is used to identify the H2ONH3 complex isolated in an argon (Ar) matrix. An electric discharge is then applied to the H2O and NH3 species to produce the hydroxyl-ammonia (OHNH3) complex and the water-amidogen (H2ONH2) complex. Finally, the ammonia-oxygen (NH3O2) complex is formed in an Ar matrix, complementing previous studies performed by the Quickenden research group, which investigated the conversion of OH radicals into molecular O2 on icy planetary surfaces. ... An electric discharge is applied to the NH3 in Ar mixture, producing the NH2 radical subunit of the complex. Two absorption bands are assigned to the H2O subunit vibrational frequencies of the complex; at 1616.1 cm-1 for the ¿2 HOH bending fundamental and at 3532.1 cm-1 for the ¿1 OH bonded stretching fundamental. Two absorption bands are also assigned to the NH2 radical subunit vibrational frequencies of the complex; at 1498.5 cm-1 for the ¿2 HNH bending fundamental and at 3260.8 cm-1 for the ¿3 NH asymmetric stretching fundamental. These assignments are verified by the isotope substitution method, involving the formation of the deuterated D2OND2 complex analogue in an Ar matrix and the measurement of the isotope induced shifts in peak position in the IR region. The isotopic shifts displayed by the IR absorption bands are in good agreement with the theoretically calculated shifts in vibration frequency when going from the H2ONH2 complex fundamentals to the D2OND2 complex fundamentals. The theoretical calculations also derived an interaction energy of 5.2 kcal mol-1 for the HOHNH2 structure of the H2ONH2 complex. This HOHNH2 structure is also confirmed as the preferred structure of the H2ONH2 complex in the IR experiments, by the observation of a large shift in position of the absorption band associated with the H2O subunit ¿1 OH stretching fundamental, away from the position of the H2O monomer ¿1 OH stretching fundamental. This indicates that the H2O subunit donates a hydrogen for the complex bond in the HOHNH2 complex. The NH3O2 complex is identified in solid Ar matrices at 10.5 K by IR analysis. The NH3O2 complex is formed by the co-deposition of gaseous NH3 in Ar mixtures with O2 in Ar gas mixtures. An absorption band is assigned to the ¿1 OO stretching fundamental for the O2 subunit of the NH3O2 complex at 1552.0 cm-1. This assignment is verified by the isotope substitution method, involving the formation of the deuterated ND3O2 complex analogue in an Ar matrix and the measurement of the isotope induced shift in peak position in the IR region. The isotopic shift displayed by the IR absorption band is in good agreement with the theoretically calculated shift in vibration frequency when going from the NH3O2 complex fundamental to the ND3O2 complex fundamental. The theoretical calculations also derived an interaction energy of 0.28 kcal mol-1 for the NH3O2 complex.
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Estrada, Hector. "Importance of the subsurface limestome and pockets of soil as sources of water for tree species in Yucatan, Mexico." Diss., UC access only, 2009. http://proquest.umi.com/pqdweb?index=84&did=1914305761&SrchMode=1&sid=1&Fmt=7&retrieveGroup=0&VType=PQD&VInst=PROD&RQT=309&VName=PQD&TS=1270233485&clientId=48051.
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Rose, Jonathan Patrick. "The importance of micro-topographic heterogeneity in determining species diversity of alpine plant communities of Glacier National Park, MT." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/731.
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Alpine plant communities can be exceptionally diverse at a fine scale, and they often exhibit fine scale topographic variability. High species diversity is often attributed to spatial and temporal heterogeneity in the environment. The goal of this study was to test for a positive relationship between microtopographic heterogeneity and species diversity of alpine plants. Species diversity of vascular plants was sampled at 8 sites in Glacier National Park, MT during the summer of 2009. Species richness was assessed both within a 1 x 1 m plot and at 100 points spaced 10 cm apart within the plot. To quantify topographic heterogeneity and variability, the relative elevation was measured for all 100 points in the plot as well. Similarity in species composition between study plots was investigated using Non-Metric Multidimensional Scaling. The study plots separated into two groups based on the presence/absence of Dryas octopetala. This difference is most likely due to plots occupying different positions along the mesotopographical gradient and therefore experiencing different moisture regimes. Regression for all 1 m2 plot data found a negative relationship between topographic heterogeneity and species richness, and no relationship between topographic variability and species richness. Quantile regression was used to assess the relationship between point measures of species richness and topographic variability. There is evidence for topographic variability imposing a limit on species richness for all sites grouped together and for sites that do not contain D. octopetala. This limit is most likely due to the interaction of soil disturbance and the productivity of a site.
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Kirkpatrick, Ryan Scott. "Nocturnal light and temperature influences on necrophagous, carrion-associating blow fly species (Diptera: Calliphoridae) of forensic importance in Central Texas." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1104.
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It is commonly thought that blow flies are nocturnally inactive. Blowflies are often important in helping to estimate post mortem intervals (PMI) for corpses found at death scenes. If blow flies oviposit during nocturnal hours, there could possibly be up to 12-hour discrepancies for estimates of PMI.
Two blow fly species, Phaenicia eximia (Wiedemann) and Cochliomyia macellaria (F.), oviposited nocturnally on ground beef baits in 2003, during the onset of low-atmospheric pressure (an air mass with lower atmospheric pressure than that of the air surrounding it) at rural study sites near Snook (Burleson County), Texas, under artificial lighting of at least 1500 footcandles when temperatures were at 26?C or higher. Trials conducted under similar conditions during the same year without a low-pressure system moving into the area resulted in no nocturnal blow fly oviposition.
Nocturnal blow fly oviposition went undetected once low-atmospheric pressure systems settled into the study area, irrespective of temperature and lighting conditions. Thus, this study illustrates that there is a connection between the onset of low-atmospheric pressure and nocturnal blow fly oviposition on baits under artificial lighting of 1500 footcandles or more when temperatures are 26 ?C or above.
After concluding 2003 experiments, statistical analyses supplied evidence that woodland habitat was more favorable for blow fly oviposition than prairieland habitat throughout the 2003 study, irrespective of species or time of year. Furthermore, statistical analyses conducted on nocturnal and diurnal temperature ranges furnished evidence to support the hypothesis that 2003 nocturnal temperatures had more of an effect on daily ovipositing than diurnal temperatures for P. eximia and Cynomyopsis cadaverina (Robineau-Desvoidy).
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Morales, Ernesto J. "Self-recruiting species in farmer managed aquatic systems : their importance to the livelihoods of the rural poor in Southeast Asia." Thesis, University of Stirling, 2007. http://hdl.handle.net/1893/250.
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The self-recruiting species (SRS) are aquatic animals that can be harvested regularly from a farmer managed system without regular stocking as described by Little (2002a, b). The potential and current role of self-recruiting species from farmer managed aquatic systems (FMAS) is often overlooked, whilst much attention has been given to stocked species (often associated in conventional culture ponds and cages) as well as the fisheries sector (often relates to large water bodies i.e. river lakes and reservoirs). Using the combination of qualitative and quantitative research approaches, the current status, the important contribution of SRS and factors undermining this contribution to the livelihoods of rural households in mainland Southeast (SE) Asia were investigated. The overall analysis of this research was done based from the sustainable livelihood (SL) framework (Scoones, 1998; DFID, 1999) in order to have a broader understanding of the importance of SRS as well as the rural livelihoods in selected areas of mainland SE Asia which often benefit from this resource. The research was carried out in rural villages of southeast Cambodia (SEC), northeast Thailand (NET) and Red River Delta in northern Vietnam (RRD). The sites (region of the country) were selected based from the intensity of aquaculture practices (less established and mainly relying on natural production, aquaculture established but also relying on natural production and mainly aquaculture dependent) as well as the agriculture i.e. intensiveness of rice production. Eighteen villages (6 villages/ country) were selected to represent the two agro-ecological zones (i.e. LOW and DRY areas) of the study sites. In order to fully assess the situation and meet the objectives of the research, the study was carried out using three stages which dealt with different approaches and sets of participants/respondents; i) participatory community appraisal (PCA), ii) baseline survey and iii) longitudinal study. The different stages of the research were carried out during the period of April 2001 until September 2004. During the first stage, a series of community appraisals using participatory methods were conducted in all of the participating villages in the three study sites. The participatory appraisal was conducted in order to understand the general rural context in the villages as well as the importance of aquatic resources. Moreover, the PCA in a way helped build rapport between the researcher and the communities. The series of appraisals were conducted with different wellbeing and gender groups (better-off men, better-off women, poor men and poor women). The various shocks, trends and seasonality that influenced the status of living in the community, diversified livelihoods and the differences in preference of socioeconomic and gender groups were analysed in this stage. The important aquatic animals (AA) and the local criteria for determing their importance were the highlights of this stage of the research. The important AA identified were composed of large fish (Channa spp., Clarias spp., Hemibagrus sp, Common, Indian, Silver and Grass carps), small fish (Anabas testudineus, Rasbora spp., Mystus spp., Carassius auratus) as well as non-fish (Macrobrachium spp., Rana spp., Somanniathelpusa sp., Sinotaia spp.) which were particularly important to poorer groups in the community. The local criteria used were mainly food and nutrition related (good taste, easy to cook, versatility in preparation), abundance (availability, ease of catching) as well as economic value (good price). Significant differences were found between various interactions of sites, agro-ecological zones, gender and wellbeing groups. The second stage of the research was the baseline survey (cross-sectional survey) which was also carried out in the same communities and collected information from a total of 540 respondents (30 respondents per village or 180 per country). This stage of the study was carried out in order to generate household level information (mostly quantitative) regarding the socio-economic indicators to triangulate the information generated during the participatory appraisal and the different aquatic systems that existed in the community as well as the various management practices used (not limited to stocking hatchery seed and feeding). The different livelihood resources (human, physical, financial, natural and social capital) and the diversified strategies of rural households in SE Asia were analysed in this phase. Another highlight of this phase was the understanding of the various aquatic systems that rural farmers managed and how they related to the existence of self-recruiting species. The common aquatic resources identified during this phase included farmer managed aquatic systems (FMAS) and openwater bodies (OWB) where rural households usually obtained their aquatic products. The various types of FMAS which included ricefields, trap ponds, household ponds, culture ponds and ditches were identified as important aquatic resources which mainly provide food as well as additional income to the rural poor. All of these FMAS were being managed at various levels which directly affected the SRS population. Different types of farmers were identified based on their attitudes towards and management of SRS: i) SRS positive, farmers who allow and attract SRS into the system, ii) SRS negative, farmers who prevent or eliminate SRS and iii) SRS neutral, farmers doing nothing that would encourage or prevent SRS from entering into the system. Variations were related to the main factors (i.e sites, agroecological zones, wellbeing groups) and their interactions. The final stage of this study was the year-long household survey (longitudinal study) that investigated the seasonality of various aspects of rural livelihoods, status of the different aquatic systems and the important contribution of AA in general, and SRS in particular, to the overall livelihood strategies employed by rural farmers. This phase involved a total of 162 households (9 per village or 54 per country) selected based on the aquatic systems they managed and had access to. Other socio-economic factors (gender and wellbeing) were also considered during the selection of participants in this phase of the study. The results of the year long household survey highlighted the important contributions of SRS: i) to the total AA collections which were utilised in various ways, ii) contribution to overall food consumption in general and AA consumption in particular (which was found to be the most important contribution of SRS), iii) contribution to household nutrition (as a major source of animal protein and essential micro nutrients in rural areas), iv) contribution to income and expenditures, and v) improving the social capital of rural households (through sharing of production and mobilizing community in local resources user group management). Moreover, the social context and the dynamics of inter and intra household relationships were understood, especially the gender issues on division of labour (where women and children played an important part on the production), access and benefits (how women and children were being marginalised in terms of making decision and controlling benefits). The various results of the combined approaches that were utilised in all stages of the research were analysed and presented in this thesis. The results of the community appraisals and the baseline survey were used in setting the context (background) of each topic (e.g. livelihood activities, AA importance, etc). Meanwhile, the results of the longitudinal survey were used in illustrating the trends and highlighted the seasonality of particular issues. Overall the study contributed to knowledge by elucidating the status and roles of self-recruiting species in maintaining/ improving the overall livelihoods of rural farmers in Southeast Asia.
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Kozak, Kenneth H., and John J. Wiens. "What explains patterns of species richness? The relative importance of climatic-niche evolution, morphological evolution, and ecological limits in salamanders." WILEY-BLACKWELL, 2016. http://hdl.handle.net/10150/621556.
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A major goal of evolutionary biology and ecology is to understand why species richness varies among clades. Previous studies have suggested that variation in richness among clades might be related to variation in rates of morphological evolution among clades (e.g., body size and shape). Other studies have suggested that richness patterns might be related to variation in rates of climatic-niche evolution. However, few studies, if any, have tested the relative importance of these variables in explaining patterns of richness among clades. Here, we test their relative importance among major clades of Plethodontidae, the most species-rich family of salamanders. Earlier studies have suggested that climatic-niche evolution explains patterns of diversification among plethodontid clades, whereas rates of morphological evolution do not. A subsequent study stated that rates of morphological evolution instead explained patterns of species richness among plethodontid clades (along with "ecological limits" on richness of clades, leading to saturation of clades with species, given limited resources). However, they did not consider climatic-niche evolution. Using phylogenetic multiple regression, we show that rates of climatic-niche evolution explain most variation in richness among plethodontid clades, whereas rates of morphological evolution do not. We find little evidence that ecological limits explain patterns of richness among plethodontid clades. We also test whether rates of morphological and climatic-niche evolution are correlated, and find that they are not. Overall, our results help explain richness patterns in a major amphibian group and provide possibly the first test of the relative importance of climatic niches and morphological evolution in explaining diversity patterns.
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Wilkins, Keiko W. "The Importance of Dissolved Organic Matter Source on the Survival and Growth of Juvenile Daphnia." Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami1578699709430677.
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Towner, Ronald H., Matthew W. Salzer, James A. Parks, and K. Renee Barlow. "Assessing The Importance Of Past Human Behavior In Dendroarchaeological Research: Examples From Range Creek Canyon, Utah, U.S.A." Tree-Ring Society, 2009. http://hdl.handle.net/10150/622611.
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Dendroarchaeological samples can contain three kinds of information: chronological, behavioral, and environmental. The decisions of past people regarding species selection, beam size,
procurement and modification techniques, deadwood use, and stockpiling are the most critical factors influencing an archaeological date distribution. Using dendrochronological samples from prehistoric and historic period sites in the same area of eastern Utah, this paper examines past human behavior as the critical factor in dendroarchaeological date distributions.
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Schimanski, Kate Bridget. "The importance of selective filters on vessel biofouling invasion processes." Thesis, University of Canterbury. School of Biological Sciences, 2015. http://hdl.handle.net/10092/11299.
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The spread of exotic species is considered to be one of the most significant threats to ecosystems and emphasises the need for appropriate management interventions. The majority of marine non-indigenous species (NIS) are believed to have been introduced via ship biofouling and their domestic spread continues to take place via this mechanism. In some countries, biosecurity systems have been developed to prevent the introduction of NIS through biofouling. However, implementing biosecurity strategies is difficult due to the challenges around identifying high-risk vectors. Reliable predictors of risk have remained elusive, in part due to a lack of scientific knowledge. Nonetheless, invasion ecology is an active scientific field that aims to build this knowledge. Propagule pressure is of particular interest in invasion ecology as it describes the quantity and quality of the propagules introduced into a recipient region and is considered to be an important determinant in the successful establishment of NIS. Environmental history affects health and reproductive output of an organism and, therefore, it is beneficial to examine this experimentally in the context of biofouling and propagule pressure. The aim of this thesis was to examine how voyage characteristics influence biofouling recruitment, survivorship, growth, reproduction and offspring performance through the ship invasion pathway. This was to provide fundamental knowledge to assist managers with identifying high-risk vessels that are likely to facilitate the introduction or domestic spread of NIS, and to understand the processes affecting biofouling organisms during long-distance dispersal events. Chapter One provides an introduction to the issues addressed in this thesis. Each data chapter (Chapters Two – Five) then focused on a stage of the invasion process and included field experiments using a model organism, Bugula neritina. Finally, Chapter Six provides a summary of key findings, discussion and the implications to biosecurity management. Throughout this thesis, the effect of donor port residency period on the success of recruits was highlighted. Chapter Two focused on recruitment in the donor region. As expected, recruitment increased with residency period. Importantly, recruitment occurred every day on vulnerable surfaces, therefore, periods as short as only a few days are able to entrain recruits to a vessel hull. The study presented in Chapter Three showed that there was high survivorship of B. neritina recruits during 12 translocation scenarios tested. In particular, the juvenile short-residency recruits (1-8 days) survived voyages of 8 days at a speed of 18 knots; the longest and fastest voyage simulated. Interestingly, variation in voyage speed and voyage duration had no effect on the survivorship of recruits, but did have legacy effects on post-voyage growth. Again, B. neritina which recruited over very short residency periods of 1 day continued to perform well after translocation and had the highest level of reproductive output after the voyage scenarios (Chapter Four). Recruits that were older (32-days) and reproductively mature at the commencement of the scenarios failed to release any propagules. Even though the number of ‘at sea’ and ‘port residency’ days were equal, reproductive output was higher after short and frequent voyages than after long and infrequent voyages. Finally, the study presented in Chapter Five examined transgenerational effects of B. nertina. Results showed that although the environmental history of the parent colony had a carry-over effect on offspring performance, it was the offspring environment that was a stronger determinant of success (measured by reproductive output and growth). Although cross-vector spread is possible (i.e. parent and offspring both fouling an active vessel), offspring released from a hull fouling parent into a recipient environment will perform better. In combination, these studies have provided new insights into NIS transport via vessel biofouling. Although shipping pathways are dynamic and complex, these results suggest that juvenile stages that recruit over short residency periods and are then translocated on short voyages, may pose a higher risk for NIS introduction than originally assumed. This has implications for marine biosecurity management as short residency periods are common and short, frequent voyages are typical of domestic vessel movements which are largely unmanaged.
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Susset, Eline. "Importance des agrégations de diapause dans la reproduction de la coccinelle Hippodamia undecimnotata (Schneider) : (Coleoptera Coccinellidae)." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30146/document.
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Les causes évolutives de certaines formes de vie en groupe sont bien identifiées mais pas celles des agrégations de diapause des arthropodes (rassemblements monospécifiques d'adultes dans des sites à localisation constante). Dans cette thèse, j'ai testé si, selon l'hypothèse du lek caché, les arthropodes se rassemblent pour trouver leurs partenaires sexuels chez la coccinelle Hippodamia undecimnotata. J'ai montré que les coccinelles se rassemblent dans des endroits avec un repère proéminent et où le risque de pesticides est faible, puis que les conditions abiotiques dans les sites sont défavorables à la survie des coccinelles. Ensuite, j'ai mis en évidence l'occurrence de nombreux accouplements dans les sites d'agrégation. Enfin, j'ai montré que ces accouplements sont peu coûteux en énergie pour les femelles, qui conservent de l'énergie pour les comportements post-agrégation. Cette thèse atteste que les agrégations de diapause font partie du système de reproduction des arthropodes<br>The evolutionary significance of some kinds of group living are well-known, some others such as the diapause aggregations remain poorly known although widespread. In this thesis, I tested if the arthropods form diapause aggregations to find their mates according to the hidden lek hypothesis with the ladybird Hippodamia undecimnotata. By using a Species Distribution Model, I showed that ladybirds aggregate in places with a prominent object and where the risk of being sprayed by pesticides is low. Then, I highlighted that abiotic conditions are unfavourable to ladybirds' survival. In a third part, I found that mating is widespread activity in the aggregation sites. Finally, I showed that energetic costs linked to mating are low, and thus allow the ladybirds to disperse and display post aggregations behaviour. This thesis shows that the diapause aggregations are part of the mating system of the arthropods and that sexual selection can be a driver of the evolution of diapause aggregations
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Dahlsjö, Cecilia A. L. "Termite assemblage structure and function : a study of the importance of termites in lowland equatorial forests." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:28a37283-4013-4c5a-be2e-aac26d97f838.
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Termites are important ecosystem engineers in tropical and sub-tropical terrestrial regions where they influence ecosystem processes by altering the physical and chemical structure of the habitat. Termites affect nutrient availability by decomposition and comminution (shredding) of organic matter and act as agents of bioturbation as they re-work substrates during the construction of nests, tunnels and runways. At present we have a relatively good understanding of termite diversity patterns in the tropics through the extensive use of the standardised transect sampling protocol by Eggleton et al. (1995). These diversity data suggest that there is a functional difference in termite assemblage structure, and potentially in termite abundance and biomass, among comparable habitats across continents. However due to the lack of comparable abundance and biomass data from South America this has not previously been confirmed. In this thesis I, therefore, collected extensive data on termite taxonomic and functional assemblage structure in a South American site in Peru. The data were used to compare termite abundance and biomass from two comparable sites in Africa (Cameroon) and south east Asia (Malaysia) in order to gain better understanding of the role termites play in ecosystem processes. I found that there was an intercontinental difference in the abundance and biomass of termite feeding-groups mainly due to the dominance of soil-feeding termites in Cameroon and the absence of fungus-growing termites from Peru. The impact of certain lineages on the intercontinental differences suggests that the differences may be due to biogeographical evolution. Moreover, Eggleton et al. (1998) show that larger-bodied soil-feeding termites in Cameroon process more energy per unit area than predicted by their body size. Due to the need for an examination of the allometric relationships in termite assemblages outside Africa and the development of a more sophisticated feeding-group classification I explore the findings in Eggleton et al. (1998) further using population density - body mass relationships in three termite feeding-groups among the three continental sites in Cameroon, Peru and Malaysia. I found that large-bodied soil-feeding termites in Cameroon and large-bodied wood-feeding termites in Peru had higher population densities than expected by their body masses. As the population density - body mass relationship is inverse to that of the energy - body mass relationship the results suggest that the two feeding-groups also use more energy than expected by their body masses. Further, we have a relatively good understanding of the role termites play as ecosystem engineers e.g. in nutrient cycling and distribution, however, compared with our understanding of wood and litter decomposition in tropical forests quantitative data on the impact of termites in soil processes is poorly understood. In this thesis I conducted, to our knowledge, the first in situ soil macrofauna exclusion experiment using translocated soil in Peru to examine the impact of termites on soil C and N loss. I found that termites promote soil C and N loss which may be linked to the increase in microbial activity due to the passage of soil through the termite gut as well as the affect termites have on bioturbation and nutrient distribution. To conclude, in this thesis I present the first intercontinental comparison of abundance and biomass as well as the first in situ soil macrofauna exclusion experiment to date. The link between termite ecology, biogeography and evolution is discussed as well as the contribution of this thesis to the field of termite ecology.
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Näslund, Johan. "The importance of biodiversity for ecosystem processes in sediments : experimental examples from the Baltic Sea." Doctoral thesis, Stockholms universitet, Systemekologiska institutionen, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38893.
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Aquatic sediments are, by surface, the largest habitat on Earth. A wide diversity of organisms inhabit these sediments and by their actions they have a large influence on and also mediate many ecosystem processes. Several of these processes, such as decomposition and remineralisation of organic matter are important on a global scale and are essential to sustain life on Earth. The main aim of this thesis was to use an experimental ecosystem ecology approach in order to study some of these ecosystem processes in marine sediments and how they are linked to biodiversity. Paper I and II found that an increased species richness of sediment deposit feeders increases the processing of organic matter from phytoplankton settled on the sea-floor, and that species-rich communities have a more efficient resource utilization of deposited organic matter. The results in paper IV and V also suggest that there is a link between microbial diversity in sediments and the degradation of organic contaminants. Paper V also shows that antibiotic pollution is a potential threat to natural microbial diversity and microbially mediated ecosystem services. The introduction of invasive species to ecosystems is another major threat to biodiversity and was studied in Paper II and III, by investigating the ecology of Marenzelleria arctia, a polychaete worm recently introduced in the Baltic Sea. Paper II suggests that M. arctia mainly utilize food resources not used by native deposit feeders, thus potentially increasing the benthic production in the Baltic Sea by increasing resource use efficiency. Paper III, however, show that M. arctia is protected from predation by the native benthic invertebrate predators, due to its ability to burrow deep in the sediment, suggesting that predation on M. arctia by higher trophic levels is restricted, thereby limiting trophic transfer. In conclusion, this thesis gives some examples of the importance of marine biodiversity for the generation of a few key ecosystem processes, such as organic matter processing and the degradation of harmful contaminants.<br>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: In press.
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Santos, Ícaro Gonçalves. "Diversidade florística e fitossociológica dos quintais agroflorestais do reassentamento Mariana, Tocantins." Universidade Federal do Tocantins, 2017. http://hdl.handle.net/11612/389.
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Objetivou-se caracterizar a composição florística e fitossociológica do componente arbustivo-arbóreo de quatro quintais agroflorestais (QAs) no reassentamento Mariana, Tocantins, a fim de conhecer a estrutura dessas áreas e as suas contribuições para a manutenção, proteção e conservação da biodiversidade. Além disso, buscou-se subsidiar a formação de uma base de dados referentes aos quintais agroflorestais no estado do Tocantins. O levantamento foi realizado em quatro quintais agroflorestais no reassentamento Mariana, que se encontra entre os municípios de Palmas e Porto Nacional, no estado do Tocantins. Foram instaladas três parcelas de 20x30m em cada quintal, perfazendo um total de 0,72 ha de área amostral, sendo amostrados todos os indivíduos arbustivo-arbóreos com circunferência altura do peito 1,30 cm do solo (CAP) ≥ a 10 cm. Foram amostrados nos quatro QAs um total de 477 indivíduos, 81 espécies, 34 famílias e 73 gêneros. O valor encontrado para o índice de diversidade (Shannon) foi de 3,68 e para equabilidade (Pielou) foi de 0,83, valores esses encontrados em 0,72 ha de área amostral. Individualmente, os quintais agroflorestais apresentaram os seguintes valores de diversidade de Shannon (H’) QA1 2,52; QA2 3,27; QA3 2,66 e QA4 2,94; e equabilidade de Pielou (J’) QA1 0,78; QA2 0,90; QA3 0,77 e QA4 0,85. A altura média da vegetação no QA1 foi de 4,79m e área basal total de 120,17m²/ha, no QA2 a altura media foi de 5,14m com área basal total de 18,49m²/ha, no QA3 a altura media foi de 3,66m e área basal total de 27,42m²/ha, no QA4 a altura media foi de 5,54m com área basal total de 33,98m²/ha. As dez espécies mais importantes dos quintais agroflorestais representaram juntas 44,26% do valor de importância total, com destaque para as espécies Malpighia glabra, Psidium guajava e Mangifera indica que alcançaram posições de destaque em mais de um quintal. As dez famílias mais importantes somaram juntas 67,63% do IVI total as famílias que mais se destacaram foram Arecaceae, Anacardiaceae e Fabaceae para todos os (QAs) avaliados. Assim, pode-se inferir que os quintais agroflorestais do reassentamento Mariana demonstraram alta riqueza e diversidade, evidenciando grande heterogeneidade ambiental e baixa dominância ecológica.<br>The objective of this study was to characterize the floristic and phytosociological composition of the shrubby-arboreal component of four quintals agroforestry (QAs) in the Mariana resettlement, Tocantins, in order to know the structure of these areas and their contributions to the maintenance, protection and conservation of biodiversity. In addition, it was sought to subsidize the formation of a database of agroforestry quintals in the state of Tocantins. Three 20x30m plots were installed in each quintal, making a total of 0,72 ha of sample area, and all shrub-arboreal individuals with chest height circumference 1,30 cm (CAP) ≥ 10 cm were sampled. A total of 477 individuals, 81 species, 34 families and 73 genera were sampled in the four QAs. The value found for the diversity index (Shannon) was 3,68 and for equability (Pielou) was 0,83, values found in 0,72 ha of sample area.Individually, agroforestry quintals had the following Shannon diversity values (H '): QA1 2,52; QA2 3,27; QA3 2,66 and QA4 2,94; And Pielou equability (J ') QA1 0,78; QA2 0,90; QA3 0,77 and QA 40,85. The average height of the vegetation in QA 01 was 4,79m and total basal area was 120,17 m²/ ha, in QA 02 the average height was 5,14m with a total basal area of 18,49 m²/ ha, in QA 03 a mean height was 3,66 m and total basal area was 27,42 m²/ ha; in QA 04 the mean height was 5,54m with a total basal area of 33,98 m²/ha.The ten most important agroforestry species together represented 44.26% of the value of total importance, especially the species: Malpighia glabra, Psidium guajava and Mangifera indica that they reached prominent positions in more than one quintal.The ten most important families together accounted for 67.63% of the total IVI, and the families that stood out were Arecaceae, Anacardiaceae and Fabaceae for all (QAs) evaluated. Thus, it can be inferred that the agroforestry quintals of the Mariana resettlement demonstrated high richness and diversity, evidencing great environmental heterogeneity and low ecological dominance.
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Pirathiban, Ramethaa. "Improving species distribution modelling: Selecting absences and eliciting variable usefulness for input into standard algorithms or a Bayesian hierarchical meta-factor model." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/134401/1/Ramethaa_Pirathiban_Thesis.pdf.
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This thesis explores and proposes methods to improve species distribution models. Throughout this thesis, a rich class of statistical modelling techniques has been developed to address crucial and interesting issues related to the data input into these models. The overall contribution of this research is the advancement of knowledge on species distribution modelling through an increased understanding of extraneous zeros, quality of the ecological data, variable selection that incorporates ecological theory and evaluating performance of the fitted models. Though motivated by the challenge of species distribution modelling from ecology, this research is broadly relevant to many fields, including bio-security and medicine. Specifically, this research is of potential significance to researchers seeking to: identify and explain extraneous zeros; assess the quality of their data; or employ expert-informed variable selection.
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Casties, Isabel [Verfasser], Elizabeta [Akademischer Betreuer] Briski, and Ulrich [Gutachter] Sommer. "Non-indigenous species in Northern Europe and the Great Lakes-St. Lawrence River: the importance of geographic origin / Isabel Casties ; Gutachter: Ulrich Sommer ; Betreuer: Elizabeta Briski." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1236572726/34.
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Malone, Meredith B. "Abundance, Fruit Presence, and Growth Enhancement of Prestoea montana and Roystonea borinquena, Two Palm Species of Importance to Amazona vittata (Puerto Rican Parrot), in Río Abajo Forest, Puerto Rico." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-05012007-121725/.
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The endangered Puerto Rican parrot (Amazona vittata) has been bred in captivity for decades, and since 2000, over 50 parrots have been released into native habitats to rebuild wild populations in Puerto Rico. One group of 21 parrots was released into Río Abajo Forest in the karstic region of Puerto Rico in November 2006, where high quality habitat resources exist, but the management of sustainable food resources, such as the fruit of Prestoea montana (sierra palm) and Roystonea borinquena (royal palm), is imperative. An inventory of accessible regions in Río Abajo Forest was conducted to assess differences in size and abundance of P. montana and R. borinquena palms between three forest community types and fruiting patterns under differing growing conditions. Twenty palms in each of three size classes of both palm species were located in Río Abajo Forest and approximately half were supplied with a controlled-release formula of inorganic NPK fertilizer with micronutrients to investigate potential soil nutrient limitations to growth of palms. Thirty R. borinquena seedlings were located in artificial canopy gap plots previously created in abandoned Hibiscus elatus (mahoe) plantations in Río Abajo Forest and approximately half were supplied with the same fertilizer formula to evaluate combined soil and light limitations on seedling growth. In the size and abundance inventory, seedlings were the most abundant size class of both palm species. No significant difference in size or abundance existed between any size classes of either palm species in different forest community types. P. montana seedling size and abundance were correlated with moderate shade, available soil P and other micronutrients, and relatively alkaline soils. Seedling height and diameter significantly increased with the addition of NPK and micronutrients to surrounding soil. Wet soils appeared most important to fruit production of mature P. montana. In the size and abundance inventory, R. borinquena seedling success was correlated to sites containing relatively high soil micronutrient concentrations and seedlings and mature R. borinquena palms exhibited larger size, abundance, and fruit production in open canopies. R. borinquena seedling height significantly increased with the addition of N-P-K and micronutrients to surrounding soil. Diameter significantly increased with the addition of fertilizer to soil surrounding seedlings in artificial canopy gap plots. Mortality was decreased in R. borinquena seedlings with the addition of fertilizer, under the full canopies of fertilizer experiments and in the open canopies of artificial canopy gap plots. Management to increase abundance and fruit production of these palm species in RAF may initially include techniques to provide increased light availability and nutrients to mature R. borinquena. Strategic management objectives may include provision of the same resources to smaller R. borinquena and increased soil moisture and nutrients to P. montana of all sizes.
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Patsias, Kathrin [Verfasser], Helge [Akademischer Betreuer] Bruelheide, Isabell [Akademischer Betreuer] Hensen, and Jitka [Akademischer Betreuer] Klimešová. "The importance of gap dynamics for the reproduction of clonal plant species in natural forests in the Harz National Park / Kathrin Patsias. Betreuer: Helge Bruelheide ; Isabell Hensen ; Jitka Klimešová." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2011. http://d-nb.info/1025301463/34.
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Thomas, Marc Merlin. "The effects of defoliation on seasonal growth dynamics, the importance of internal nitrogen-recycling and the availability of soil nutrients: implications for the invasive potential of Buddleia davidii (Franch.)." Thesis, University of Canterbury. Biological Sciences, 2007. http://hdl.handle.net/10092/1477.
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ABSTRACT Assessing the impact of herbivory on plant growth and reproduction is important to predict the success of biocontrol of invasive plants. Leaf area production is most important, as photosynthesis provides the foundation for all plant growth and fitness. High levels of defoliation generally reduce the productivity of plants. However, leaf area production fluctuates during the season and compensational growth may occur, which both complicate accurate estimations of defoliation impacts. Under field conditions the interaction with neighbouring species and the availability of soil nutrients need to be assessed in order to gauge long term effects of weed invasions on natural environments. In this thesis I have investigated seasonal leaf area dynamics in Buddleia davidii following repeated artificial defoliation, to quantify compensational leaf production and to understand the regulatory mechanisms involved. The impact of defoliation on photosynthesis, seed production, germination and nitrogen translocation patterns were analysed. Finally, possible facilitation between B. davidii and a native nitrogen fixer, Coriaria arborea, and the impact of B. davidii on soil nutrient availability were investigated. In defoliated B. davidii, increased node production (34%), leaf size (35%) and leaf longevity (12%) resulted in 52% greater total emergent leaf area in the short term. However, with time and diminishing tissue resources the compensation declined. No upregulation of photosynthesis was observed in pre-existing leaves. Compensational leaf area production occurred at the expense of reproduction but the germination capacity of individual seeds was unaffected. In B. davidii, nitrogen reserves are stored in old leaves. Thus, the defoliation-induced decline in tissue reserves led to changes in the remobilisation pattern and increased the importance of soil uptake but biomass production especially that of roots had declined significantly (39%). Slight facilitation effects from the neighbouring nitrogen fixer and VA-mycorrhizae were observed on B. davidii in the field, while its impact on soil chemistry during spring was negligible. Defoliation of B. davidii resulted in priority allocation of resources to compensational leaf growth and a concomitant reduction in flower and seed production. The compensational leaf production greatly increased the demand for nitrogen, while continued leaf removal decreased the pool of stored nitrogen. This led to changes in nitrogen remobilisation and an increased importance of root uptake. However, the significant decline in root growth will likely impair adequate nutrient uptake from the soil, which is especially important where B. davidii invades nutrient poor habitats and will increase the success of biocontrol of the species. While mycorrhizae increase nutrient accessibility for B. davidii, it is likely that the additional stress of defoliation will negate the small facilitative effects from nitrogen-fixing species like C. arborea. This research provides new insights into the mechanisms regulating leaf area dynamics at the shoot level and systemic physiological responses to defoliation in plants, such as nitrogen translocation. The compensation in leaf area production was considerable but only transitory and thus, the opportunity to alleviate effects of leaf loss though adjustment of light capture limited. However, to ascertain that photosynthesis at whole plant level does not increase after defoliation, more detailed measurements especially on new grown leaves are necessary. In general, defoliation had greatly reduced plant growth and performance so that an optimistic outlook for controlling this species can be given. Conclusions about the wider impacts of B. davidii on soil chemistry and community function will require further research.
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Monteiro, Lúcia Maria Oliveira. "Modelação e parametrização de índices de importância ecológica (IIE): um contributo para gestão e conservação da natureza." Master's thesis, Universidade de Évora, 2013. http://hdl.handle.net/10174/16080.
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Modelação e parametrização de Índices de Importância Ecológica (IIE): um contributo para gestão e conservação da natureza
Uma das principais estratégias necessárias para reduzir a perda de biodiversidade é a criação e gestão adequada de áreas protegidas bem como a definição de prioridades de conservação através da valorização das espécies. O objetivo deste trabalho foi cartografar a importância ecológica avifaunística no território continental, avaliando o grau de correspondência entre as áreas de maior importância ecológica e as áreas classificadas como Zona de Proteção Especial (ZPE). Para o efeito, calculou-se a importância ecológica das espécies de aves nidificantes em Portugal Continental através de quatro índices diferentes. Verificou-se que os quatro índices calculados responderam de formas diferentes na hierarquização das espécies. Qualquer priorização de espécies depende muito da disponibilidade e qualidade dos dados. As três ZPE estudadas apresentaram delimitações congruentes com as áreas de valores elevados de cada índice e pode-se afirmar que há uma tendência global para que estes valores se tornem progressivamente mais baixos para locais mais distantes das ZPE; ABSTRACT: Modelling and parameterization of Ecological Importance Index (EII): a contribution to management and nature conservation
One of the most important strategies needful to reduce the loss of biodiversity is the creation and proper management of protected environmental areas and the definition of conservation priorities through the appreciation of the species. The objective of this work was mapping the ecological importance of avifauna in the mainland, evaluating the degree of equivalence between the areas of greatest ecological importance and areas classified as ZPE. For both, we evaluated the ecological importance of the species of breeding birds in mainland of Portugal through four different indexes. We verified that the four indexes evaluated showed different relevances in the hierarchy of species. Any prioritization of species depends much of the way that qualifies and systematizes of data. The three ZPE studied had boundaries congruent with areas of high values of each index and showed that there is a global trend for these values become progressively lower as moving away from ZPE.