Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"Environmental Gradient"”.
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The impact of grazing along an environmental gradient in the Kamiesberg, South Africa
The Kamiesberg Mountain range, which is situated within the arid Succulent Karoo biome, South Africa, is internationally-recognised for its high conservation value and forms the study site for this project. The Kamiesberg is straddled by the Leliefontein communal area, which has been stocked for …
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Landscapes of the apes: modelling landscape use of chimpanzees and early hominins across an environmental gradient.
… anamensis/ afarensis) landscape use along an environmental gradient from forests to savannahs to determine their adaptability to change. Based on literature review, this thesis first quantitatively defined chimpanzee landscapes as dense forests, forest mosaics and savannahs using vegetation …
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Diazotroph Assemblages of Salt Marsh Plants Growing Along An Environmental Gradient: Assemblage Composition and Responses to Environmental Conditions
… of the US typically occur along an elevation gradient that results in a distinctive pattern of plant zonation. This study examined the diazotroph assemblages associated with salt marsh plants in discrete zones along this elevation gradient in Crab Haul Creek Basin, North Inlet, SC, and their …
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Variation of echolocation pulse source levels and detection distances for bat assemblages across an environmental gradient: “a test of the acoustic adaptation hypothesis”
… derived from echolocation pulse reflects these environmental challenges. Hence, echolocation pulses within or between species may vary from one habitat to the next due to variable selection pressure, resulting in local adaptation as formalised in the Acoustic Adaptation Hypothesis, which …
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The effects of heuweltjies and Microhodotermes viator (Isoptera: Hodotermitidae) on invertebrate assemblages and species turnover in the succulent Karoo, Western Cape
… species composition along a spatial, temporal or environmental gradient. One such environmental gradient that has been shown to affect species turnover is local edaphic variation. This is seen in the Western Cape Province of South Africa, where the unique edaphic character of large earth mounds, …
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Some nonlinear problems in plankton ecology
… pattern. A common approach to identifying key environmental forcings is to match scales of variability: fluctuations of a biological variable at a particular frequency are attributed to forcing by the physical environment at a similar frequency. In nonlinear systems, however, different scales …
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Patterns of plant species richness and diversity across two habitat types in the Upper Karoo, South Africa
… It also investigated the role of several environmental and climatic variables as drivers of species richness, relative cover, and growth form diversity in two habitat types (i.e. plains and rocky dolerite hillslopes), and along a longitudinal environmental gradient. A pairwise floristic …
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Latitudinal Gradient Facilitates Adaptive Population Differentiation of Campanulastrum americanum (American Bellflower)
… americanum as a model for assessing whether an environmental gradient can facilitate local adaptation. In particular, I determined if a latitudinal gradient across eastern United States has influenced the phenology and reproductive fitness of five northern and four southern C, americanum …
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Assessing genomic variation in the hopbush, Dodonaea viscosa, to investigate micro-evolution and adaptation
… Dodonaea viscosa ssp. angustissima along an environmental gradient within South Australia. Firstly, I generated a transcriptome reference genome by sequencing RNA from several individuals and used a range of bioinformatic tools to assemble and annotate it (chapter four). This transcriptome …
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A Spatio-temporal Phylogenetic Approach to Community Ecology
… small spatial scales, which then transitions to environmental filtering at broad spatial scales. Therefore studies which select communities at a fixed spatial size are biased toward observing certain patterns and may subsequently overlook spatially-dependent processes. Finally, for angiosperm …
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The Macroecology of Microorganisms: From Pattern to Process
… considerably different responses to the same environmental gradient, hinting that regional communities play an important role in determining microbial community composition at local scales. Finally, I investigate whether regional-scale climatic variables determine the distributions of …
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The influence of water and light on the physiology and spatial distributions of three shrubs in the Southern Appalachian Mountains
In order to understand vegetational gradients which develop in response to environmental gradients, the physiological capabilities of each species must be examined in relation to the observed environmental gradient. The distributions of three temperate zone shrub species which occupy different …
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Characterization Of Arctic Soils: Interrelationships With Site And Vegetation
… profiles, and between profiles along a micro-environmental gradient. A suite of soils forming a catena in north central Keewatin (65(DEGREES)27' N, 96(DEGREES)38' W) was investigated. Forty-five variables representing particle size properties, bulk density, moisture content, pH and …
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Biogeographical Approaches for Studying Species Invasion
… I also examined the evolution of latitudinal gradients in native and invasive genotypes of P. australis in relation to plant-herbivore interactions in North America. Common garden experiments revealed that the native and invasive genotypes of P. australis have evolved latitudinal clines on …
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Crop Yields Response To Conservation Farming And Spatial-Temporal Effects In Zambia
We examined crop yields along a wide environmental gradient and spatial dynamics in soil organic matter in response to conservation farming (CF) in Zambia. Maize yields from farmer managed CF and traditional farming (TF) were not significantly different with over 280 on-farm trials with varying …
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Evolution at the edge: how hibernation, heat waves, and hybridization impact a range expansion
… an ongoing natural range expansion across an environmental gradient. Through the following four chapters, I document evolution of dispersal ability and life history traits (Chapter 1), evolution of seasonal dormancy and genetic variation of that trait (Chapter 2), evolution of phenotypic …
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The Effects of Geography, Environment and Phylogeny on Community Assembly and Gene Flow Dynamics
… influences how plants respond to spatial and environmental gradients and interact with each other is less clear. In this dissertation I leverage evolutionary tools and thinking to understand how space and environment affect community composition and patterns of gene flow in a unique system of …
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Structure, distribution and phenology of perennial plant species in the Worcester Veld Reserve, in the arid winter rainfall region of the Southwestern Cape
… within and between arid ecosystems. and of the environmental factors that may be responsible for any variations found. Nor is much information available on how phenological behaviour relates to the structural attributes of plant species. This study examined structural attributes of perennial …
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The Genomics of Divergence and Adaptation in Sister Reef Fishes Separated by the Isthmus of Panamá
… the genetic basis of adaptation to changing environmental conditions is challenging. This is especially true in marine systems where connectivity between populations may be high and past conditions difficult to reconstruct. The emergence of the Isthmus of Panamá provides a unique, natural …
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Effects of Management Practices on Grassland Plant and Bird Community Composition in Kane County Forest Preserves
… Species evolution based on these particular environmental conditions has caused many species to be mapped onto various environmental gradients which can be defined as niche separation. This study attempted to determine what environmental gradients had the strongest impact upon grassland bird …
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