Dissertationen: „Density of trees“

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Hall, Justine Michelle. „Trees in towns : factors affecting the distribution of trees in high density residential areas of Greater Manchester“. Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/trees-in-towns-factors-affecting-the-distribution-of-trees-in-high-density-residential-areas-of-greater-manchester(568b58f3-4524-4a8d-abba-2094c4e21567).html.

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The distribution of trees across urban areas of the UK has been shown to be uneven, with lower density residential areas containing many more trees and much higher tree cover than areas of higher density housing. However, in Greater Manchester, tree number within high density housing areas also varies substantially. This thesis sought to explore the reasons for this variation in tree cover, whether tree cover should be increased and if so, how. The research investigated a potential cause for the variation in number of trees and tree cover within high density housing areas – housing type – for the study area of western Greater Manchester. Eleven different types of high density housing were categorised and all high density housing within the study area was classified as one of these types. Within these housing types, the amount of tree cover was determined, along with the proportions of other surface types. The land uses where the trees were growing were also determined. Finally, the potential increases in tree cover were also calculated for each housing type by a simulated planting technique. Maximum surface temperatures and rainfall runoff were calculated using computer models, for both existing and potential tree cover in each housing type. It was found that urban tree cover varies from 1.6% in pre 1919 terraced housing that opens directly onto the road to 14.8% in 1960s walkway-style housing. Tree cover could theoretically be increased by at least 5% in all housing types, reducing maximum surface temperatures by at least 1°C. In housing types with less than 4% existing tree cover, maximum surface temperatures could be reduced by up to 4.5°C. The views of residents were determined using a postal questionnaire about urban trees sent to residents of 4 different types of street environment. Residents of all street types surveyed were very positive about urban trees; their attitudes were not affected by whether there are trees in their street or not. The vast majority of respondents considered trees important to their quality of life, and that cost to the council should not prevent tree planting. The views and practices around urban trees and greening by practitioners were determined by running a workshop and their recommendations to increase tree cover are presented. These include changes in funding to include money for tree maintenance after planting, the importance of a full tree inventory and innovative ways to raise funding for trees. The effectiveness of a community greening scheme at increasing tree cover was compared with two regeneration schemes. The community tree planting scheme was found to deliver tree planting much closer to the potential than regeneration schemes.

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Agha, N. S. A. „High-density planting system for Bramley's seedling apple trees“. Thesis, University of Reading, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373464.

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3

Smart, Nicholas. „Street Trees Across Culture and Climate : A Comparative Analysis of Density and Distribution“. Thesis, KTH, Urbana och regionala studier, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278520.

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The positive relationship between humans and nature is manifest in the urban greening movement, which has taken root in cities around the world. Street trees are an essential component of urban design and have emerged from a variety of historic legacies, both human and environmental. While the growing body of research on street trees has considered street tree density and distribution across cities, it has not situated these metrics in the broader discussion on the historical legacies of urban greening. This study considers five capital cities (Ottawa, Stockholm, Buenos Aires, Paris, and Washington, D.C.) spanning two climate zones and three continents to analyze the density and distribution of street trees by asking two questions: (1) what is the density and distribution of street trees across a given city and its street hierarchy? (2) how do these metrics compare within and between cities by climate zone? Preexisting datasets from local authorities are used to execute a geospatial analysis of the street tree structure of the central zone of each city. The results of this study shed light on the importance of place-specificity in informing the street tree legacy of cities and questions the existing primacy of the city-wide canopy cover metric as a global norm in planning practice.
Det positiva förhållandet mellan människor och natur är manifest i stadsförgröningsrörelsen (urban greening movement), vilket har etablerat sig i städer runtom i världen. Gatuträd är en essentiell komponent av stadsutformning och har växt fram från en mångfald av historiska arv, båda mänskliga och miljömässiga. Medan allt mer forskning om gatuträd har betraktat gatuträdtäthet och distribution tvärs över städer, har den inte placerat dessa mätmetoder i den större diskussionen om historiska arv av stadsförgröning. Denna studie betraktar fem huvudstäder (Ottawa, Stockholm, Buenos Aires, Paris, och Washington, D.C.) över två klimatzoner och tre kontinenter för att analysera gatuträdtäthet och distribution genom att ställa två frågor: (1) vad är tätheten och distributionen av gatuträd genom en stad och dess gatunätverkshierarki? (2) hur jämförs dessa mätmetoder inom och mellan städer i samma klimatzon? Befintliga data från lokala myndigheter används för att utföra en georumslig analys av gatuträdstrukturen i centralzonen av varje stad. Resultaten belyser platsspecificitetens vikt att inverka stadsgatuträdsarv och ifrågasätter den befintliga dominansen av stadsträdkronstäckning som en global norm inom planeringspraktik.

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Akachuku, A. E. „Intra-Annual Variation in Wood Density in Gmelina Arborea from X-Ray Densitometry and its Relationship with Rainfall“. Tree-Ring Society, 1985. http://hdl.handle.net/10150/261361.

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The variation in wood density within growth rings was determined from X-ray negative images of wood samples of Gmelina arborea. The within-tree and between-tree comparisons showed that no two growth rings had exactly similar patterns of variation in the radial direction. The proportions of wood in four within-ring density classes were estimated. The variations in the proportions of wood in the four classes with age were nonlinear. On the average, the proportion of low density wood decreased with increasing age, while the proportion of high density wood increased with age. Regression analysis testing different curvilinear models showed that 37 to 99 per cent of the variations in the proportions of wood were associated with variations in age. Maximum and minimum ring density were negatively correlated with dry season rainfall. Variations in the proportion of high density wood and mean ring density were not associated with corresponding variation in dry season rainfall. The proportions of low and high density wood, mean ring density, maximum ring density and minimum ring density were not determined by annual rainfall.

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O'Donnell, Alison J., Kathryn J. Allen, Robert M. Evans, Edward R. Cook und Valerie Trouet. „Wood density provides new opportunities for reconstructing past temperature variability from southeastern Australian trees“. Elsevier B.V, 2016. http://hdl.handle.net/10150/621340.

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Tree-ring based climate reconstructions have been critical for understanding past variability and recent trends in climate worldwide, but they are scarce in Australia. This is particularly the case for temperature: only one tree-ring width based temperature reconstruction – based on Huon Pine trees from Mt Read, Tasmania – exists for Australia. Here, we investigate whether additional tree- ring parameters derived from Athrotaxis cupressoides trees growing in the same region have potential to provide robust proxy records of past temperature variability. We measured wood properties, including tree-ring width (TRW), mean density, mean cell wall thickness (CWT), and tracheid radial diameter (TRD) of annual growth rings in Athrotaxis cupressoides, a long-lived, high-elevation conifer in central Tasmania, Australia. Mean density and CWT were strongly and negatively correlated with summer temperatures. In contrast, the summer temperature signal in TRW was weakly positive. The strongest climate signal in any of the tree-ring parameters was maximum temperature in January (mid-summer; JanTmax) and we chose this as the target climate variable for reconstruction. The model that explained most of the variance in JanTmax was based on TRW and mean density as predictors. TRW and mean density provided complementary proxies with mean density showing greater high-frequency (inter-annual to multi-year) variability and TRW showing more low-frequency (decadal to centennial-scale) variability. The final reconstruction model is robust, explaining 55% of the variance in JanTmax, and was used to reconstruct JanTmax for the last five centuries (1530–2010 C.E.). The reconstruction suggests that the most recent 60 years have been warmer than average in the context of the last ca. 500 years. This unusually warm period is likely linked to a coincident increase in the intensity of the subtropical ridge and dominance of the positive phase of the Southern Annular Mode in summer, which weaken the influence of the band of prevailing westerly winds and storms on Tasmanian climate. Our findings indicate that wood properties, such as mean density, are likely to provide significant contributions toward the development of robust climate reconstructions in the Southern Hemisphere and thus toward an improved understanding of past climate in Australasia.

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Rokicki, Jonathan, und Henrik Pira. „Foliage generation tool based on a Lindenmeyer system : A study on branch density of trees in video games“. Thesis, Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18402.

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Context. Procedurally generated content is a common way for companiesto save time and resources when creating modern video games.However, with generation of content there is often many variables controllingthe outcome that is tricky to get right. Objectives. The aim of this thesis is to research how people perceivethe branch density of trees used in video games. This will be done bycreating a foliage generation tool that is based on the functionality ofan L-system. The tool will be used to generate 12 trees with differentbranch densities which will be used for the questionnaire in the userexperiment. Method. A foliage generation tool has been created to be able togenerate trees with different branch and twig densities. The trees generatedwith the tool have been used in a user experiment in order tocome to a conclusion on how people perceive different branch densityin virtual trees. Result. Trees with higher branch and twig densities were rated higherthan trees with lower ones. The best rated tree in all regards was atree in the group with the second most main branches and had 0.6 intwig density. Conclusions. The results show that trees with a higher branch densitymade participants rate it as better looking in the user experiment.Although, trees with a high number of main branches and low twigdensity got the lowest score.

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McDaniel, Virginia. „Density and Age Distributions of Trees in Upland and Lowland Oldfields 60 Years After Abandonment: The Role of Dispersal“. TopSCHOLAR®, 2000. http://digitalcommons.wku.edu/theses/727.

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I attempted to determine whether the patterns of seedling establishment described in the literature for forests and recently abandoned oldfields are maintained in fields sixty years after abandonment. To determine this distribution pattern, as well as to compare patterns of age and density distribution in upland and lowland oldfields, I conducted research at Mammoth Cave National Park. I studied three species, the seeds of which are dispersed by three different modes: Juniperus virginiana, a predominantly bird-dispersed species; Acer rubrum, a predominantly winddispersed species; and Fagus grandifolia, a predominantly mammal-dispersed species. The establishment patterns observed by others in recently abandoned oldfields were not maintained in the sixty-year-old fields analyzed in this study. Age of Juniperus virginiana individuals did not decrease as distance from the edge increased in either uplands or lowlands. Age of Acer rubrum individuals decreased marginally as distance from the edge increased in the upland sites, but slope of the regression was not significant in the lowlands. Ages of Fagus grandifolia individuals decreased significantly as distance from the edge increased in both uplands and lowlands. Migration rate, however, was more rapid than predicted in the literature. Density distribution of stems of each species was even across all oldfields. Rare, long-distance dispersal events are a possible explanation for the establishment patterns observed in these sixty-year-old fields.

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Davies, Nicholas Tuatahi. „Reverse Engineering the Tree“. Thesis, University of Canterbury. Forestry, 2014. http://hdl.handle.net/10092/9600.

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The aim of this thesis was to investigate the typical radial pattern of density and microfibril angle within Pinus radiata with respect to structural stability. In order to investigate changes in mechanical stability with different radial patterns, first experimental work was carried out in order to obtain elastic constants, Poisson ratios and limits of proportionality for green corewood and outerwood, these values, a discussion on their accuracy and the implications of the values are included along with a comparison to previous literature. These constants were used to parametrise a finite element model of a tree stem with different radial patterns, including patterns not observed in nature, wind loadings were applied to the stem and failure evaluated. It was found that patterns consisting of high density stiff wood and/or low density high flexibility wood could withstand the greatest wind speeds for a given stem and canopy, while high density flexible and low density stiff profiles generally performed poorly. The analysis was considered at ages 5, 10 and 15 years, each providing similar results. Why these profiles perform best, what errors need to be considered, and other evolutionary pressures which could narrow this list of profiles were discussed. The need for further research, and the directions for this research are suggested.

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ADU-BREDU, Stephen, Akio HAGIHARA und 秋男萩原. „Sapwood Amount and its Predictive Equations for Young Hinoki Cypress (Chamaecyparis obtusa) Trees“. 名古屋大学農学部付属演習林, 1996. http://hdl.handle.net/2237/8712.

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10

DeGomez, Tom, Christopher J. Fettig, Joel D. McMillin, John A. Anhold und Christopher Hayes. „Managing Slash to Minimize Colonization of Residual Leave Trees by Ips and Other Bark Beetle Species Following Thinning in Southwestern Ponderosa Pine“. College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008. http://hdl.handle.net/10150/146727.

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12 pp.
Pine Bark Beetles, THE PIÑON IPS BARK BEETLE, FIREWOOD AND BARK BEETLES IN THE SOUTHWEST, USING INSECTICIDES TO PREVENT BARK BEETLE ATTACKS ON CONIFERS, GUIDELINES FOR THINNING PONDEROSA PINE FOR IMPROVED FOREST HEALTH AND FIRE PREVENTION
Various techniques to reduce brood production of Ips and Dendroctonus spp. in ponderosa pine slash are discussed.

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Motinyane, Teboho R. „The influence of structure, density and direct use benefits on the harvesting of trees in the rural village of Pikoi, Eastern Cape, South Africa“. Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1007705.

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The people of Pikoli in the Peddie district of the Eastern Cape are mostly unemployed and earn most of their income from old-age allowances. The place is remote and 'modern' amenities such as paraffin and petroleum gas are expensive. Electricity and transport are unavailable. There is heavy reliance on woody plants for fuel and for materials for construction and fencing and to some extent medicinal and ritual uses. Indigenous trees in this rural area are threatened by over-utilisation and the absence of clear government management policies. The over-utilisation of these resources is leading to deforestation. It was proposed at the beginning of this study that people who harvest trees cause similar results to the piosphere effect caused by the herbivores on the rangeland. Ecological-economic analysis was performed to find a common ground between the people's income and needs so that effective sustainable management strategies can be developed. A combination of semi-structured interviews, direct observations and ecological surveys were used to gather information about: Tree species used, and for what purpose in Pikoli; Individual tree species preference by inhabitants; Change in tree density in response to changes in utilisation intensity at varying distances away from the village; The local direct use benefits inhabitants derive from utilising indigenous tree resources. The study showed that the people of Pikoli use a variety of 23 indigenous trees and that they have marked preferences regarding the tree species they use for fuelwood and construction purposes. Although Ptaeroxylon obliquum is a highly preferred species for fuelwood and construction, its popularity can also be linked to its high relative abundance in this area. Other species such Maytenus undata and Pappea capensis are also highly preferred although they are harvested at much greater distances from thecentre of the village. Change in individual tree density in response to changes in utilisation intensity at varying distances away from the village showed clearly that a piosphere effect also applies to human harvesting. The average number of individual trees closer (1 200 m) to the village centre was 2 trees per 100 m², and their numbers increase to approximately 35 trees per 100 m² at a distance of about 3 000 m from the village centre. The study reports on the direct use benefits derived by the people of Pikoli from harvesting tree resources. The average total net value of trees harvested for fuelwood was R4089.09 (US$ 359.01) per household per annum. The value of tree resources harvested represents a large percentage of average households' annual income. Therefore, the economic benefits households derive from utilising tree resources are high. Indigenous tree resource use in this rural village seems to be unsustainable and the inhabitants seem to be aware of it. However, they have few alternatives. Their economic conditions do not allow them to afford alternative resources available in the formal market.

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Bergqvist, Göran. „Stand and wood properties of boreal Norway spruce growing under birch shelter /“. Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5642-8.pdf.

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Pape, Rolf. „Effects of thinning on wood properties of Norway spruce on highly productive sites /“. Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5622-3.pdf.

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Hannrup, Björn. „Genetic parameters of wood properties in Pinus sylvestris (L.) /“. Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5628-2.pdf.

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Donno, Patrick. „Contribuição para o estudo da utilização da poda mecânica de verão em pomares superintensivos de amendoeira“. Master's thesis, Universidade de Évora, 2020. http://hdl.handle.net/10174/30145.

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Este trabalho insere-se num ensaio de avaliação de diferentes alternativas de poda num pomar superintensivo de amendoeiras que foi iniciado em 2017. O presente trabalho decorreu durante 2019 e consideraram-se as seguintes alternativas de poda: tratamento T0 (poda do agricultor) – poda mecânica de verão seguida de complemento manual, efetuadas em junho; tratamento T1- poda manual de inverno; tratamento T3 – poda manual no inverno para controlo da distância da base da copa ao solo e poda mecânica de verão em julho. Avaliaram-se: dimensão das árvores, tempos de poda, lenha retirada pela poda, produção e perdas de amêndoa para o solo. As intervenções de poda mecânica de verão realizadas julho permitiram maior controlo da dimensão da copa das árvores, nomeadamente em altura. As maiores perdas de amêndoa verificaram-se nas alternativas de poda que tinham as árvores maiores. Não se verificaram diferenças na produção total de amêndoa entre os tratamentos; Abstract: Contribution for the study of mechanical summer pruning in superhigh density almond orchards This work is part of an evaluation trial of different pruning alternatives in a super high density almond orchard that was started in 2017. The present work took place during 2019 and the following pruning alternatives were considered: T0 (farmer pruning) treatment - pruning summer mechanics followed by manual complementation, carried out in June; T1 treatment - manual winter pruning; T3 treatment - manual in winter to control the distance from the base of the canopy to the ground and summer mechanical pruning in July. Tree size, pruning times, pruning firewood, almond yield and soil losses were evaluated. The summer mechanical pruning interventions carried out in July allowed greater control of the treetop size, particularly in height. The highest almond losses were found in the pruning alternatives that had the largest trees. There were no differences in total almond yield between treatments.

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Link, Roman Mathias [Verfasser], Christoph [Akademischer Betreuer] Leuschner, Christoph [Gutachter] Leuschner, Bernhard [Gutachter] Schuldt, Holger [Gutachter] Kreft, Hermann [Gutachter] Behling, Dirk [Gutachter] Hölscher und Erwin [Gutachter] Bergmeier. „The role of tree height and wood density for the water use, productivity and hydraulic architecture of tropical trees / Roman Mathias Link ; Gutachter: Christoph Leuschner, Bernhard Schuldt, Holger Kreft, Hermann Behling, Dirk Hölscher, Erwin Bergmeier ; Betreuer: Christoph Leuschner“. Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1212660773/34.

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Beyer, Robert Maria [Verfasser], Paul-Henry [Akademischer Betreuer] [Gutachter] Cournède, Hans [Akademischer Betreuer] [Gutachter] Pretzsch, Youcef [Gutachter] Mammeri und Anja [Gutachter] Rammig. „Spatial Leaf Density-based Modelling of Teleonomic Crown Dynamics of Crops and Trees / Robert Maria Beyer ; Gutachter: Youcef Mammeri, Anja Rammig, Hans Pretzsch, Paul-Henry Cournède ; Paul-Henry Cournède, Hans Pretzsch“. München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1121206727/34.

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Hazelwood, Kirsten. „The role of trophic interactions in shaping tropical tree communities“. Thesis, University of Stirling, 2018. http://hdl.handle.net/1893/28637.

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Tropical rainforests contain exceptionally high biodiversity and account for >30% of the world's carbon fixed by photosynthesis. Consequently, there are compelling reasons to deepen our understanding of the mechanisms that maintain these highly diverse forests and of the potential long-term threats to their preservation. An important process shaping tropical plant communities is negative density dependence (NDD). NDD occurs when plant performance is negatively impacted by increased neighbourhood density. Reduced performance at high neighbourhood density is thought to arise through ecological interactions between plants and their natural enemies. Thus in a healthy ecosystem, trophic interactions play vital roles as mechanisms driving NDD and are important as dispersers facilitating escape from NDD mortality. However, interruption to ecological processes caused by human activities, such as hunting, can perturb NDD interactions and cause cascading effects throughout an ecosystem. In my thesis I investigate the role of dispersal and mortality in NDD dynamics of tropical tree communities, as well as investigating local and global impacts of removing ecological interactions in tropical rainforests. In my thesis, I begin by addressing the presence and variation in strength of NDD among tree species and ontogenetic stages, the mechanisms driving NDD, and the role of trophic interactions in this process. The Janzen-Connell hypothesis predicts that host-specific natural enemies drive NDD by selectively reducing conspecific density, and increase diversity by suppressing competitive exclusion, thus allowing heterospecifics to persist. In chapters 2 and 3 of this thesis, I show that mortality driven by conspecific NDD is prevalent at the early life stages, and this effect is considerably stronger during the year after germination. Furthermore, this process is driven exclusively by host-specific fungal pathogens, which cause mortality selectively among conspecifics and drive diversity. As seedlings age beyond their first year, NDD interactions become less impacted by conspecifics but are impacted by closely related neighbours or by general neighbourhood density, representing changes in the mechanism driving NDD as seedlings age, and a decline in host-specificity of natural enemies. Equally, relative growth rates (RGR) are reduced under high neighbourhood density irrespective of species identity. Results suggest insect herbivores are the strongest driver of reduced RGR but not mortality under increased neighbourhood density. As a consequence of stronger inter than intra-specific NDD effects on RGR, insects had no impact on seedling diversity in the short term. This study supports assertions that regionally rare species experience stronger NDD than common species, accounting for the high variability in species relative abundance in the tropics. In the second part of my thesis, I address the role of large vertebrate dispersers in shaping tropical tree communities and the consequences of defaunation for tree assemblage and carbon storage. Dispersal allows seeds to escape NDD and persist to reproductive maturity and is therefore vital for the maintenance of diversity. Vertebrates disperse the seeds of more than 70% of neo-tropical tree species. However, many large vertebrates are becoming scarce due to widespread hunting. The decline of large vertebrates and their role as dispersers is predicted to alter tree community composition. Additionally, large vertebrates are responsible for the dispersal of large-seeded species, which are linked to species with high wood density. With wood density positively associated with carbon storage, there is a potential cascading influence of defaunation on global carbon storage. We investigate the consequences of declining large vertebrate mortality agents in chapter 3, and the consequences of declining large vertebrate dispersers in chapters 4 and 5. Although community composition is altered in a defaunated forest, species dispersed by extirpated fauna do not appear to drive this. In fact we find that many species thought to be heavily reliant on extirpated fauna manage to persist. Although it is thought that the simultaneous loss of seed predation from large terrestrial vertebrates may create compensatory effects, we found little support for this, with an absence of large terrestrial vertebrates driving only temporary changes to species diversity. Neither a loss of large frugivores or large-seeded species lead to declines in species with high wood density, but we detect a worrying decline in large stemmed species, which has negative implications for carbon storage. Overall, my thesis highlights the importance of NDD and trophic interactions, particularly fungal pathogens, at the early life stages in shaping tropical tree communities and in maintaining diversity. I provide evidence that the removal of trophic interactions among larger natural enemies and dispersers does not impact community assemblage in the directional manner found in previous studies. I provide evidence for the variability in response to trophic interactions among species and ontogenetic stages. I show disproportionate relative importance among natural enemies and dispersers in the maintenance of tropical tree assemblage, with implications for conservation and for assessing the consequences for tree diversity under the influence of degradation.

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Weyenberg, Grady S. „STATISTICS IN THE BILLERA-HOLMES-VOGTMANN TREESPACE“. UKnowledge, 2015. http://uknowledge.uky.edu/statistics_etds/12.

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This dissertation is an effort to adapt two classical non-parametric statistical techniques, kernel density estimation (KDE) and principal components analysis (PCA), to the Billera-Holmes-Vogtmann (BHV) metric space for phylogenetic trees. This adaption gives a more general framework for developing and testing various hypotheses about apparent differences or similarities between sets of phylogenetic trees than currently exists. For example, while the majority of gene histories found in a clade of organisms are expected to be generated by a common evolutionary process, numerous other coexisting processes (e.g. horizontal gene transfers, gene duplication and subsequent neofunctionalization) will cause some genes to exhibit a history quite distinct from the histories of the majority of genes. Such “outlying” gene trees are considered to be biologically interesting and identifying these genes has become an important problem in phylogenetics. The R sofware package kdetrees, developed in Chapter 2, contains an implementation of the kernel density estimation method. The primary theoretical difficulty involved in this adaptation concerns the normalizion of the kernel functions in the BHV metric space. This problem is addressed in Chapter 3. In both chapters, the software package is applied to both simulated and empirical datasets to demonstrate the properties of the method. A few first theoretical steps in adaption of principal components analysis to the BHV space are presented in Chapter 4. It becomes necessary to generalize the notion of a set of perpendicular vectors in Euclidean space to the BHV metric space, but there some ambiguity about how to best proceed. We show that convex hulls are one reasonable approach to the problem. The Nye-PCA- algorithm provides a method of projecting onto arbitrary convex hulls in BHV space, providing the core of a modified PCA-type method.

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Tan, Arie Hadipriono. „The Integration of Fuzzy Fault Trees and Artificial Neural Networks to Enhance Satellite Imagery for Detection and Assessment of Harmful Algal Blooms“. The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574773012023708.

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21

González, Alejandro Danilo Venegas. „Tree growth response to climate change in two threatened South American Biomes: Brazilian Atlantic Forest and Chilean Mediterranean Forest“. Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-22032018-154156/.

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Biomes classified as Brazilian Atlantic Forest (BAF) and the Chilean Mediterranean forest (CMF) have been affected by anthropic pressure that has caused a considerable decrease of their forest surfasse. However, they are rich in biodiversity and they provide many ecosystem services and were, therefore, classified as \"hotspots\" (forests in risk). Therefore, is essential to study the natural dynamics and the climatic response of the trees of these forests to include conservation projects and strategic measures. To achieve these objectives, the scientific literature reports that tree growth rings are the only ecological indicators with annual resolution that can be efficient and highly accurate to obtain this information. In this context, the research project has as main objective the retrospective analysis of radial growth of forest species in different vegetation communities of BAF and CMF in response to climatic changes. To achieve this goal, four key questions were elaborated: 1) Which variable explains betterthe variability of radial growth at different spatial and temporal scales? 2) What is the growth resilience to recent climate changes? 3) Is there some more vulnerable population to expected climatic changes?. A total of five sites (seven populations) of Cedrela odorata and C. fissilis in BAF from the State of São Paulo in Brazil, and five sites (10 populations) of Nothofagus macrocarpa (FMC) from the central region of Chile were sampled, using a non-destructive method. Four chapters were developed to answer these questions. Chapter I seek to analyze the resilience in radial growth to changes in regional climate variability and droughts, in temporal and spatial scale, on Atlantic forest remnant forests of biogeographic region Serra do Mar. Results show that radial growth in wet sites (winter rains exceed 240 mm) depend on the moisture conditions in dry season, while the higher population is more sensitive to the favorable summer water condition, which would be explained because this population received a lower temperature than the other Cedrela spp. populations studied. Chapter II analyzed how recent climatic variability affected the radial growth in N. macrocarpa populations. It is observed that all the populations are closely linked to the precipitations of May-November (end of autumn/end of spring) and average temperature of October-December (mid-spring/early summer). In Chapter III, we continued exploring the growth responses to climate in the FMC populations in order to find biogeographic differences. In this sense, we evaluated if this significant decrease in tree growth is differentiated between populations and age classes, and determine if the positive effect of CO2 fertilization compensates the precipitation decrease and temperature increase in the last decades in the growth of older, maturer and younger trees . Results show a significant negative trend in all classes from the year 2000, which would be associated to a decrease in precipitation in all populations while temperature was more associated with the northern and southern populations (distribution limit). We did not find a positive effect of rising CO2. Finally, chapter IV integrated the results of the two biomes comparing the projections of aboveground trees biomass under two climatic scenarios of CMIP5 project (light and severe), in order to know which populations are more vulnerable to rising temperature forecasted by year 2100, using ring width data, wood density and allometric equations. This study will provide an overview of adaptation to recent and projected climatic changes of two hotspot neotropical biomes. Although they are different in structure-biodiversity-climate are in risk. Thus, we can understand the vulnerability of threatened forests in South America to global warming that, although they are in protected areas, does not guarantee their persistence.
Os biomas classificados como Mata Atlancia Brasileira (MAB) e da Floresta Mediterrânea Chilena (FMC) têm sido afetados pela pressão antrópica que tem causado uma diminuição considerável de sua superfície florestal. No entanto são ricas em biodiversidade e providenciam muitos serviços ecossistêmicos, pelo que foram classificadas como hotspot (florestas em risco). Portanto, é fundamental estudar a dinâmica natural e a resposta climática das árvores dessas florestas para incluir em projetos de conservação. Para atingir esses objetivos, a literatura científica reporta que os anéis de crescimento das árvores são os únicos indicadores ecológicos com resolução anual que podem ser eficientes e de elevada precisão para obter essas informações. Neste contexto, o projeto de pesquisa tem como objetivo geral a analise retrospectivo de crescimento radial de espécies florestais em diferentes comunidades vegetacionais da MAB e FMC em resposta às mudanças climaticas. Para atingir esse objetivo foram elaboradas quatro perguntas-chave: 1) Que variable explica melhor a variabilidade do crescimento radial a diferentes escalas espaciais e temporais? 2) Qual é a resiliência em crescimento das árvores às mudanças climáticas recentes? 3) Há alguma população mais vulnerável respeito às mudanças climaticas esperadas?. Foram coletadas amostras de lenho, através de método não destrutivo, de cinco sitios (sete populações) de Cedrela odorata e C. fissilis na MAB no estado de São Paulo em Brasil, e cinco sitios (10 populações) de Nothofagus macrocarpa na FMC na região central do Chile, para aplicação de tecnicas dendrocronologicas. Para responder essas questões foram desenvolvidos quatro capitulos. O capitulo I busca analisar a resiliência em crescimento radial às mudanças na variabilidade climática regional e secas, em escala temporal e espacial, em florestas remanentes da região biogeográfica Serra do Mar da Mata Atlântica, usando as especies bioindicadoras Cedrela fissilis and C. odorata. Os resultados mostram que o crescimento radial dos sítios mais úmidos (chuvas no inverno superam os 240 mm) dependem das condições hidricas da estação seca, enquanto que a população mais alta é mais sensível à condição hídrica favorável do verão, qual seria explicado porque essa população recebi uma menor temperatura respeito às outras populações de cedrela estudadas. No capitulo II analisou-se como a variabilidade climática recente estaria afeitando o crescimento radial in N. macrocarpa populations. Observa-se que todas as populações estão estreitamente ligadas às precipitações de Maio-Novembro (fim de outono/fim de primaveira) e temperatura média de Outubro-Dezembro (mediados de primaveira/inicios do verão). Especificamente, há uma tendencia negativa significativa no crescimento radial apartir de 1980 que esta associada a uma variação do clima regional. No capitulo III, continuo-se explorando as respostas do crescimento radial ao clima nas populações da FMC com objetivo de encontrar diferencias biogeográficas. Neste sentido, foi avaliado se essa diminuição significativa de crescimento é diferenciada entre populações e classes de idade, e analisar se o efeito positivo da fertilização de CO2 compensa a diminuição da precipitação e aumento da temperatura nas ultimas decadas no crescimento de árvores velhos, maduros e jovens. Os resultados mostram uma tendencia negativa significativa em todas as clases apartir do ano 2000, qual estaria associada a diminuição da precipitação em todas as populações enquanto a temperatura teve mais associada às populações do sul. Não foi encontrado um efeito positivo do aumento de CO2. Finalmente, o capitulo IV integrou os resultados dos dois biomas comparando as proyeções de biomasa arborea sob dois escenarios climáticos do projeto CMIP5 (leve e severo), com objetivo de conocer quais populações são mais vulneraveis ao aumento da temperature previsto para o ano 2100, usando crescimento radial, densidade de madeira e ecuações alométricas. Os resultados mostram que a população com maior influencia urbana e a mais seca são as mais vulneráveis ao aumento exarcerbado de temperatura nas regiões de MAB and FMC, respectivamente. O presente estudo permitiu-nos apresentar uma visão da adaptação às mudanças climáticas recentes e projetadas de dois biomas hotspot. Embora sejam diferentes em estrutura-biodiversidade-clima estão em risco. Assim, podemos entender a vulnerabilidade de florestas neotropicais ao aquecimento global, embora estejam em áreas protegidas, não garante sua persistência.

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Sevillano, Garcia Mayeya Lucero. „The Effects of Biological Control Agents on Population Growth and Spread of Melaleuca quinquenervia“. Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/406.

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The main goal of this study was to evaluate the effectiveness of two biological control agents in reducing population growth and spread of the invasive tree Melaleuca quinquenervia, a subtropical tree native to Australia, and invasive in Florida, Puerto Rico, and the Bahamas. While in Florida two insects Oxyops vitiosa (weevil), and Boreioglycaspis melaleucae (psyllid) have been established as biocontrol agents, in Puerto Rico only psyllids are present, and in the Bahamas no biocontrol agents are present. This study combined demographic data, experiments and mathematical models to investigate the influence of the biocontrol agents on M. quinquenervia's spatial population dynamics. In the field, permanent plots were established and demographic data was collected in populations in the native and exotic ranges. Australian populations are comprised mostly of tall adult trees, while in the exotic ranges populations are comprised mostly of short trees (<1.3m in height), and small adult trees. In a shade-house, I performed an experiment to investigate the effects of insect type and density on survival and growth of M. quinquenervia seedlings. I found that high density of insects, independently or in combination, reduce seedling performance, thus having the potential to alter the seedling-short plant transition of the M. quinquenervia life cycle. Based on the demographic data, I developed integral projection models (IPMs) to determine population growth rates in each region. Populations in Australia and the Bahamas are increasing, while populations in Florida and Puerto Rico are decreasing. Population growth is most sensitive to the seedling-short plant transition in all regions, except Florida, where it is most sensitive to survival of tall plants. Simulations combining the results of the IMPs and experiment indicated the biocontrol damage results in reductions in population growth rate in Puerto Rico and the Bahamas. Seed dispersal and demographic data was combined to develop an integrodifference structured model of population spread. Simulations indicated that by reducing seedling performance, insects have the potential to reduce the rate of population spread. Overall this study shows that individual-level effects of biocontrol agents have translated into reductions in population growth rate and rate of spread of M. quinquenervia.

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Esler, William Kevin. „On the development and application of indirect site indexes based on edaphoclimatic variables for commercial forestry in South Africa“. Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20145.

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Thesis (MScFor)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Site Index is used extensively in modern commercial forestry both as an indicator of current and future site potential, but also as a means of site comparison. The concept is deeply embedded into current forest planning processes, and without it empirical growth and yield modelling would not function in its present form. Most commercial forestry companies in South Africa currently spend hundreds of thousands of Rand annually collecting growth stock data via inventory, but spend little or no money on the default compartment data (specifically Site Index) which is used to estimate over 90% of the product volumes in their long term plans. A need exists to construct reliable methods to determine Site Index for sites which have not been physically measured (the socalled "default", or indirect Site Index). Most previous attempts to model Site Index have used multiple linear regression as the model, alternative methods have been explored in this thesis: Regression tree analysis, random forest analysis, hybrid or model trees, multiple linear regression, and multiple linear regression using regression trees to identify the variables. Regression tree analysis proves to be ideally suited to this type of data, and a generic model with only three site variables was able to capture 49.44 % of the variation in Site Index. Further localisation of the model could prove to be commercially useful. One of the key assumptions associated with Site Index, that it is unaffected by initial planting density, was tested using linear mixed effects modelling. The results show that there may well be role played by initial stocking in some species (notably E. dunnii and E. nitens), and that further work may be warranted. It was also shown that early measurement of dominant height results in poor estimates of Site Index, which will have a direct impact on inventory policies and on data to be included in Site Index modelling studies. This thesis is divided into six chapters: Chapter 1 contains a description of the concept of Site Index and it's origins, as well as, how the concept is used within the current forest planning processes. Chapter 2 contains an analysis on the influence of initial planted density on the estimate of Site Index. Chapter 3 explores the question of whether the age at which dominant height is measured has any effect on the quality of Site Index estimates. Chapter 4 looks at various modelling methodologies and compares the resultant models. Chapter 5 contains conclusions and recommendations for further study, and finally Chapter 6 discusses how any new Site Index model will effect the current planning protocol.
AFRIKAANSE OPSOMMING: Hedendaagse kommersiële bosbou gebruik groeiplek indeks (Site Index) as 'n aanduiding van huidige en toekomstige groeiplek moontlikhede, asook 'n metode om groeiplekke te vergelyk. Hierdie beginsel is diep gewortel in bestaande beplanningsprosesse en daarsonder kan empiriese groeien opbrengsmodelle nie in hul huidige vorm funksioneer nie. SuidAfrikaanse bosboumaatskappye bestee jaarliks groot bedrae geld aan die versameling van groeivoorraad data deur middel van opnames, maar weinig of geen geld word aangewend vir die insameling van ongemete vak data (veral groeiplek indeks) nie. Ongemete vak data word gebuik om meer as 90% van die produksie volume te beraam in langtermyn beplaning. 'n Behoefte bestaan om betroubare metodes te ontwikkel om groeiplek indeks te bereken vir groeiplekke wat nog nie opgemeet is nie. Die meeste vorige pogings om groeiplek indeks te beraam het meervoudige linêre regressie as model gebruik. Alternatiewe metodes is ondersoek; naamlik regressieboom analise, ewekansige woud analise, hibriedeof modelbome, meervoudige linêre regressie en meervoudige linêre regressie waarin die veranderlike faktore bepaal is deur regressiebome. Regressieboom analise blyk geskik te wees vir hierdie tipe data en 'n veralgemeende model met slegs drie groeiplek veranderlikes dek 49.44 % van die variasie in groeiplek indeks. Verdere lokalisering van die model kan dus van kommersiële waarde wees. 'n Sleutel aanname is gemaak dat aanvanklike plantdigtheid nie 'n invloed op groeiplek indeks het nie. Hierdie aanname is getoets deur linêre gemengde uitwerkings modelle. Die toetsuitslag dui op 'n moontlikheid dat plantdigtheid wel 'n invloed het op sommige spesies (vernaamlik E. dunnii en E. nitens) en verdere navorsing kan daarom geregverdig word. Dit is ook bewys dat metings van jonger bome vir dominante hoogtes gee aanleiding tot swak beramings van groeiplek indekse. Gevolglik sal hierdie toestsuitslag groeivoorraad opname beleid, asook die data wat vir groeiplek indeks modellering gebruik word, beïnvloed. Hierdie tesis word in ses hoofstukke onderverdeel. Hoofstuk een bevat 'n beskrywing van die beginsel van groeiplek indeks, die oorsprong daarvan, asook hoe die beginsel tans in huidige bosbou beplannings prosesse toegepas word. Hoofstuk twee bestaan uit ń ontleding van die invloed van aanvanklike plantdigtheid op die beraming van groeplek indeks. In hoofstuk drie word ondersoek wat die moontlike invloed is van die ouderdom waarop metings vir dominante hoogte geneem word, op die kwaliteit van groeplek indeks beramings het. Hoofstuk vier verken verskeie modelle metodologieë en vergelyk die uitslaggewende modelle. Hoofstuk vyf bevat gevolgtrekkings en voorstelle vir verdere studies. Afsluitend, is hoofstuk ses ń bespreking van hoe enige nuwe groeiplek indeks modelle die huidige beplannings protokol kan beïnvloed.

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Sorba, Olivier. „Pénalités minimales pour la sélection de modèle“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS043/document.

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Dans le cadre de la sélection de modèle par contraste pénalisé, L. Birgé and P. Massart ont prouvé que le phénomène de pénalité minimale se produit pour la sélection libre parmi des variables gaussiennes indépendantes. Nous étendons certains de leurs résultats à la partition d'un signal gaussien lorsque la famille de partitions envisagées est suffisamment riche, notamment dans le cas des arbres de régression. Nous montrons que le même phénomène se produit dans le cadre de l'estimation de densité. La richesse de la famille de modèle s'apparente à une forme d'isotropie. De ce point de vue le phénomène de pénalité minimale est intrinsèque. Pour corroborer et illustrer ce point de vue, nous montrons que le même phénomène se produit pour une famille de modèles d'orientation aléatoire uniforme
L. Birgé and P. Massart proved that the minimum penalty phenomenon occurs in Gaussian model selection when the model family arises from complete variable selection among independent variables. We extend some of their results to discrete Gaussian signal segmentation when the model family corresponds to a sufficiently rich family of partitions of the signal's support. This is the case of regression trees. We show that the same phenomenon occurs in the context of density estimation. The richness of the model family can be related to a certain form of isotropy. In this respect the minimum penalty phenomenon is intrinsic. To corroborate this point of view, we show that the minimum penalty phenomenon occurs when the models are chosen randomly under an isotropic law

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Nugent, Rebecca. „Algorithms for estimating the cluster tree of a density /“. Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8963.

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Paterson, James. „Drivers of Density in Ornate Tree Lizards (Urosaurus ornatus)“. Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36892.

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Explaining spatial and temporal variation in the abundance of species is one of the primary goals of ecology. Habitat selection, the behaviour that organisms use to choose habitat patches that maximize fitness, can explain patterns in abundance between patches at small spatial scales within the dispersal capacity of the species. However, habitat selection models assume there is a reduction in individual fitness as population density increases due to increased competition between individuals. Ectotherms, which often select habitats based on temperature, a density-independent resource, may not display density-dependent responses if temperature limits energy assimilation more than finite food resources limit energy acquisition. As predicted by their dependence on environmental temperatures, some ectotherms select habitat largely independently of population density when temperatures are far from the optimal temperature for performance. But, is density-dependence prevalent in ectotherm populations when temperatures are close to the optimal temperature for performance? Habitat selection models also assume that all individuals of a population exhibit the same strategy for maximizing fitness through habitat selection. However, differences in morphology and behaviour (e.g., reproductive strategy) can modify the optimal habitat selection strategy for different phenotypes. Finally, observed patterns in habitat selection and abundance can also be modified by competition with other species. Quantifying the relative importance of these different factors that affect habitat selection behaviour will improve our ability to predict the spatial distribution and relative abundance of organisms. The objective of my thesis was to explain spatial variation in the abundance of ectotherms, using the ornate tree lizard (Urosaurus ornatus) as a study species. In chapter one, I tested whether density-dependent habitat selection explained patterns in abundance and fitness of lizards between two habitats differing in suitability. In chapter two, I tested whether density dependent habitat selection in tree lizards was caused by intraspecific competition for food that limited body size and growth. In chapter three, I tested whether variation in reproductive strategy, as indicated by throat colour phenotype, affected space use and habitat selection in male tree lizards. Finally, in chapter four, I tested whether interspecific competition with another lizard species affected habitat selection, fitness, and abundance of tree lizards. My thesis emphasizes the importance of intraspecific competition in shaping patterns of habitat selection and abundance in terrestrial ectotherms. I show that habitat selection is strongly density-dependent despite differences in thermal quality between habitats. I show that density-dependent mortality and growth lower the fitness of individuals when populations reach high densities, and this likely caused habitat selection to be density-dependent. Despite this evidence for density-dependent habitat selection, I show considerable variation between individuals in habitat selection and space use. Males with different throat colour phenotypes select habitats differently, demonstrating that variation in morphology can influence habitat selection patterns within a population. Finally, I show that interspecific competition with another lizard affects space use and how frequently tree lizards switch habitats, but this does not lead to differences in fitness or in the relative abundance of tree lizards in habitats. Therefore, intraspecific competition for resources was the dominant force shaping the relative abundance of tree lizards in different habitats.

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Wang, Yi. „Latent tree models for multivariate density estimation : algorithms and applications /“. View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CSED%202009%20WANGY.

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Borrow, Christopher Andrew. „The diversity of sequence alignment and tree space at high parameter density“. Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10170.

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When attempting to characterise communities by their phylogenetic diversity, Scarabaeinae provide an ideal model system. Historically three genes, cox1, 28S and 16S, have been widely used in phylogenetic studies for members of the Coleoptera and this is also the case for the Scarabaeinae. Two of these genes, 28S and 16S, are length variable. The alignment of nucleotide sequence data containing multiple insertion and deletion events is a notoriously difficult problem to resolve. Accurately doing so is important, as the accuracy of the alignment is thought to play a crucial role in determining phylogenetic tree topology. Therefore it is necessary to find a way to accurately align the sequence data before communities can be accurately characterised across a hypothesised phylogenetic tree. Little guidance is available on how the users of alignment programs should go about this task. In the following chapters an understanding of how alignment parameters act on the alignment of 16S data from Coleoptera species is reported along with a method for using members of the Clustal program family. The use of two scoring systems for judging the quality of alignments is also explored. Selecting alignments based on minimising overall alignment diversity appears to minimise synapomorphy and homoplasy, while maximising taxonomic consistency. Therefore, using the Shannon- Wiener or Simpsons Index of diversity to score alignment quality may prove useful to phylogeneticists.

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Horne, Jennifer Anne. „Cardinal functions on pseudo-tree algebras and a generalization of homogeneous weak density“. Diss., Connect to online resource, 2005. http://wwwlib.umi.com/dissertations/fullcit/3165824.

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DIOURY, KARIM. „Analyse temporelle hierarchique des circuits vlsi a tres haute densite d'integration“. Paris 6, 1998. http://www.theses.fr/1998PA066096.

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L'analyse temporelle s'inscrit dans la phase de verification d'un circuit vlsi numerique. Avec l'avenement des technologies fortement submicroniques, l'analyse temporelle statique s'impose comme la seule methode possible pour la verification temporelle de circuits pouvant atteindre aujourd'hui plusieurs dizaines de millions de transistors. Neanmoins, cette methode genere des volumes de donnees trop importants. Pour pallier ce probleme, nous avons defini une methode fondee sur le decoupage hierarchique de la phase de conception, afin de representer les temps de propagation dans un circuit, grace a une vue temporelle hierarchique multi-niveaux. Les temps de propagations dus aux portes et aux reseaux rc sont representes par un graphe de causalite dont les sommets sont les evenements sur les signaux, et les arcs les temps de propagation entre deux evenements sur deux signaux. Chaque instance de l'arbre hierarchique est representee par une figure temporelle contenant l'information relative au graphe de causalite qui ne peut etre decrite dans les figures temporelles associees aux sous-blocs instancies par chacune de ces instances. Une methode de parcours du graphe de causalite a ete definie afin de limiter la recherche des chemins entre les registres et les connecteurs a une petite partie du graphe. L'approche integre egalement un nouveau concept dans l'analyse temporelle, la factorisation des chemins critiques. Cela permet, par la resolution du probleme de la croissance quadratique du nombre de ces chemins, d'accelerer la recherche de chemins critiques dans le graphe de causalite ainsi reduit. La vue temporelle multi-niveaux que nous avons definie a permis de concevoir l'outil d'analyse temporelle hierarchique hitas ainsi que l'outil interactif de visualisation des chemins xtas. L'experimentation de ces outils a montre que notre approche permet de traiter des circuits a tres haute densite d'integration.

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Sciauveau, Marion. „Asymptotiques de fonctionnelles d'arbres aléatoires et de graphes denses aléatoires“. Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1127/document.

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L'objectif de cette thèse est l'étude des approximations et des vitesses de convergence pour des fonctionnelles de grands graphes discrets vers leurs limites continues. Nous envisageons deux cas de graphes discrets: des arbres (i.e. des graphes connexes et sans cycles) et des graphes finis, simples et denses. Dans le premier cas, on considère des fonctionnelles additives sur deux modèles d'arbres aléatoires: le modèle de Catalan sur les arbres binaires (où un arbre est choisi avec probabilité uniforme sur l'ensemble des arbres binaires complets ayant un nombre de nœuds donné) et les arbres simplement générés (et plus particulièrement les arbres de Galton-Watson conditionnés par leur nombre de nœuds).Les résultats asymptotiques reposent sur les limites d'échelle d'arbres de Galton-Watson conditionnés. En effet, lorsque la loi de reproduction est critique et de variance finie (ce qui est le cas des arbres binaires de Catalan), les arbres de Galton-Watson conditionnés à avoir un grand nombre de nœuds convergent vers l'arbre brownien continu qui est un arbre réel continu qui peut être codé par l'excursion brownienne normalisée. Par ailleurs, les arbres binaires sous le modèle de Catalan peuvent être construits comme des sous arbres de l'arbre brownien continu. Ce plongement permet d'obtenir des convergences presque-sûres de fonctionnelles. Plus généralement, lorsque la loi de reproduction est critique et appartient au domaine d'attraction d'une loi stable, les arbres de Galton-Watson conditionnés à avoir un grand nombre de nœuds convergent vers des arbres de Lévy stables, ce qui permet d'obtenir le comportement asymptotique des fonctionnelles additives pour certains arbres simplement générés. Dans le second cas, on s'intéresse à la convergence de la fonction de répartition empirique des degrés ainsi qu'aux densités d'homomorphismes de suites de graphes finis, simples et denses. Une suite de graphes finis, simples, denses converge si la suite réelle des densités d'homomorphismes associées converge pour tout graphe fini simple. La limite d'une telle suite de graphes peut être décrite par une fonction symétrique mesurable appelée graphon. Etant donné un graphon, on peut construire par échantillonnage, une suite de graphes qui converge vers ce graphon. Nous avons étudié le comportement asymptotique de la fonction de répartition empirique des degrés et de mesures aléatoires construites à partir des densités d'homomorphismes associées à cette suite particulière de graphes denses
The aim of this thesis is the study of approximations and rates of convergence for functionals of large dicsrete graphs towards their limits. We contemplate two cases of discrete graphs: trees (i.e. connected graphs without cycles) and dense simple finite graphs. In the first case, we consider additive functionals for two models of random trees: the Catalan model for binary trees (where a tree is chosen uniformly at random from the set of full binary trees with a given number of nodes) and the simply generated trees (and more particulary the Galton-Watson trees conditioned by their number of nodes).Asymptotic results are based on scaling limits of conditioned Galton-Watson trees. Indeed, when the offspring distribution is critical and with finite variance (that is the case of Catalan binary trees), the Galton-Watson trees conditioned to have a large number of nodes converge towards the Brownian continuum tree which is a real tree coded which can be coded by the normalized Brownian excursion. Furthermore, binary trees under the Catalan model can be built as sub-trees of the Brownian continuum tree. This embedding makes it possible to obtain almost sure convergences of functionals. More generally, when the offspring distribution is critical and belongs to the domain of attraction of a stable distribution, the Galton-Watson trees conditioned to have a large number of nodes converge to stable Levy trees giving the asymptotic behaviour of additive functionals for some simply generated trees. In the second case, we are interested in the convergence of the empirical cumulative distribution of degrees and the homomorphism densities of sequences of dense simple finite graphs. A sequence of dense simple finite graphs converges if the real sequence of associated homomorphism densities converges for all simple finite graph. The limit of such a sequence of dense graphs can be described as a symmetric measurable function called graphon.Given a graphon, we can construct by sampling, a sequence of graphs which converges towards this graphon. We have studied the asymptotic behaviour of the empirical cumulative distribution of degrees and random measures built from homomorphism densities associated to this special sequence of dense graphs

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Svensson, Magnus. „Embryonic Mortality and Sex Ratios in the Tree Sparrow“. Doctoral thesis, Uppsala University, Department of Ecology and Evolution, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7426.

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Tree sparrows (Passer montanus) have been studied in two areas in Sweden since 1997. At both sites, tree sparrow eggs had remarkably low hatching success. On average only 60% of the eggs hatched. Analyses have shown that this was caused by embryonic mortality, which was highly sex biased. About 70 % of the dead embryos were males, while about 65 % of all fledged nestlings were females. Impaired hatching success here related to two factors. Hatching success was lower for pairs with a male in poor body condition, and it was lower in areas with a high local population density.

A sex bias in the mortality early in life has been demonstrated in several species. Since the competitive ability of males is determined by conditions early in life, parents with poor provisioning capacity should prefer to produce female offspring in broods reared under poor conditions. The body condition of a tree sparrow during the nestling stage was well correlated to the condition as an adult, and pairs in which the male parent was in poor condition produced chicks in poor condition. Since the breeding success of a pair depended more on the condition of the male, females appear less affected by conditions early in life. Parents with poor provisioning capacity appear to bias offspring survival towards females, and a difference in the early susceptibility may be adaptive.

Changes in birth sex ratios have in some cases been suspected to result from exposure to estrogenic environmental pollutants. This was examined by exposing great- and blue tit embryos to a synthetic estrogen. Although there was a difference in the mortality rate, the difference was present also in the control groups, why this could not be attributed to estrogen exposure.

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Aouragh, M’bark. „Dynamique des paysages de l'arganeraie du Sud-Ouest marocain : apport des données de télédétection et perspectives de les intégrer dans un SIG“. Thesis, Paris 4, 2012. http://www.theses.fr/2012PA040135.

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L’Arganier [Argania spinosa (L.) Skeels] est un arbre de la famille des Sapotacées, endémique du sud-ouest marocain. C’est un arbre multi-usages, qui constitue une ressource primordiale pour les populations de cet espace semi-aride et aride du Maroc. Il constitue la clef-de-voûte de l’agro-écosystème traditionnel de l’arganeraie reposant sur un équilibre entre ressources et exploitation humaine, et joue également un rôle important dans la lutte contre la désertification et l’érosion. Actuellement, la menace de dégradation de l’arganeraie est une préoccupation majeure aussi bien pour la population que pour les scientifiques. On assiste en effet depuis plusieurs décennies à une diminution du couvert arboré, à la fois en surface occupée et en densité d’arbres. Face à cette préoccupation, nous avons étudié l’espace multidimensionnel de l’arganeraie en cherchant à identifier les principales caractéristiques de cet espace, ainsi que les facteurs responsables de sa dégradation. Ensuite, nous avons dévoilé l’originalité de cet espace à partir de son organisation sociale et spatiale, ainsi que le mode de fonctionnement et de gestion de ce territoire. Dans la deuxième partie nous avons montré l’apport de la télédétection spatiale et des systèmes d’information géographique pour la caractérisation de l’occupation du sol et l’identification des changements à partir d’un suivi diachronique, en utilisant une série d’images SPOT, Landsat, Google Earth, Ikonos. Nous avons également testé la possibilité d'évaluer la densité des arganiers à partir des images à haute résolution spatiale Ikonos et Google Earth. Nous concluons à la nécessité d’un suivi de ce territoire afin de pouvoir évaluer les changements et prendre les mesures d’aménagement et de protection nécessaires
The Argan [Argania spinosa (L.) Skeels] is a species of tree endemic to the calcareous semi-desert Sous valley of southwestern Morocco. It is the sole species in the genus Argania (family of Sapotaceae). It is a multi-purpose tree, and the main resource provider for the population of this semi-arid and arid area (source of forage, oil, timber and fuel). Argan is the keystone species of the traditional agro-ecosystem of the Berber society, ensuring a meta-stable equilibrium between resource availability and anthropic use; it plays a major role in preventing erosion and desertification damages.Currently, in spite of the Biosphere Reserve label attributed by UNESCO in 1998, the threat of degradation of the sparse Argan forest is a main concern for both local population and scientists. Since several decades, a decrease of extension area of the species and of tree density has been observed. According to this preoccupation, we have studied the multidimensional space of the Argan forest, in view of identifying its main features and the potential drivers of degradation processes. Then the originality of this area has been demonstrated through the assessment of its social and spatial organization, and of land-use and management practices.In the second part, we have shown the possible use of remotely sensed data and of Geographic Information Systems for surveying land-use/land-cover and for monitoring changes through a multi-temporal analysis of satellite images: SPOT, Landsat, Ikonos and Google Earth imagery. The evaluation of tree density has been performed through object-oriented classification of high spatial resolution satellite imagery (Ikonos, Google Earth). In conclusion, we recommend the effective use of a monitoring system to follow environmental changes in the Argan tree area, and to produce the detailed information needed for implementation of management and conservation strategies ensuring a sustainable development of the area

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Wood, Heather. „EU tree density limits in wooded pastures and their effects on bat populations within traditional agricultural landscapes“. Thesis, Stockholms universitet, Institutionen för naturgeografi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-131796.

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The European Union’s Common Agricultural Policy (CAP) recommends subsidies are only granted for wooded pastures with less than 100 trees per hectare. This arbitrary guidance exists despite these habitats being among the most biodiverse in rural Europe. To date, most biodiversity research in agricultural landscapes has focused on plants, birds and invertebrates. Bats are also important bio-indicators of agricultural landscapes, but to my knowledge no study has explicitly focused on bat diversity in relation to this policy. In this thesis, I investigate how bat activity, foraging and species richness is affected in twenty-six wooded pastures along a gradient of tree density, from open to dense pastures. In parallel, nearby open fields and deciduous woodlands were sampled, creating a triplet of habitats being surveyed simultaneously. Bat species were divided into feeding guilds to explore how functional diversity affects response to habitat and landscape configuration. The overall contribution of wooded pastures to the species pool of bats within a heterogeneous, low intensity agricultural landscape was also explored. I found a consistent increase in bat activity and species richness within wooded pastures along the tree density gradient and across most feeding guilds. This in combination with shrub density was the strongest predictor of total bat activity and foraging; whilst structural diversity of pastures was most strongly correlated with species richness. Wooded pastures contributed more to total species richness than forested habitats. Interestingly, higher activity levels of forest feeding specialists were observed in pastures compared to forests. At the landscape level, amount of water and deciduous forest were the strongest predictors of bat activity. This study demonstrates that tree density within wooded pastures is not a limiting factor of bat activity and that other habitat and landscape parameters are important. Wooded pastures may also be an important component of current landscapes with little remaining deciduous forest. In conclusion, focusing solely on tree density limits will not help to preserve the ecological requirements for bats within agricultural landscapes.

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Campbell, Rochelle, Danny McCarroll, Iain Robertson, Neil J. Loader, Håkan Grudd und Björn Gunnarson. „Blue Intensity In Pinus Sylvestris Tree Rings: A Manual For A New Palaeoclimate Proxy“. Tree-Ring Society, 2011. http://hdl.handle.net/10150/622639.

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Minimum blue intensity is a reflected light imaging technique that provides an inexpensive, robust and reliable surrogate for maximum latewood density. In this application it was found that temperature reconstructions from resin-extracted samples of Pinus sylvestris (L.) from Fennoscandia provide results equivalent to conventional x-ray densitometry. This paper describes the implementation of the blue intensity method using commercially available software and a flat-bed scanner. A calibration procedure is presented that permits results obtained by different laboratories, or using different scanners, to be compared. In addition, the use of carefully prepared and chemically treated 10-mm-diameter cores are explored; suggesting that it may not be necessary to produce thin laths with the rings aligned exactly perpendicular to the measurement surface.

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Wan, Mohd Jaafar Wan Shafrina Binti. „Individual tree detection and modelling above-ground biomass and forest parameters using discrete return airborne LiDAR data“. Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31143.

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Individual tree detection and modelling forest parameters using Airborne Laser Scanner data (Light Detection and Ranging (LiDAR) is becoming increasingly important for the monitoring and sustainable management of forests. Remote sensing has been a useful tool for individual tree analysis in the past decade, although inadequate spatial resolution from satellites means that only airborne systems have sufficient spatial resolution to conduct individual tree analysis. Moreover, recent advances in airborne LiDAR now provide high horizontal resolution as well as information in the vertical dimension. However, it is challenging to fully exploit and utilize small-footprint LiDAR data for detailed tree analysis. Procedures for forest biomass quantification and forest attributes measurement using LiDAR data have improved at a rapid pace as more robust and sophisticated modelling used to improve the studies. This thesis contains an evaluation of three approaches of utilizing LiDAR data for individual tree forest measurement. The first explores the relationship between LiDAR metrics and field reference to assess the correlation between LiDAR and field data at the individual-tree level. The intention was not to detect trees automatically, but to develop a LiDAR-AGB model based on trees that were mapped in the field so as to evaluate the relationships between LiDAR-type metrics under controlled conditions for the study sites, and field-derived AGB. A non-linear AGB model based on field data and LiDAR data was developed and LiDAR height percentile h80 and crown width measurement (CW) was found to best fit the data as evidenced by and Adj-R2 value of 0.63, the root mean squared error of the model of 14.8% and analysis of the residuals. This paper provides the foundation for a predictive LiDAR-AGB model at tree level over two study sites, Pasoh Forest Reserve and FRIM Forest Reserve. The second part of the thesis then takes this AGB-LiDAR relationship and combines it with individual tree crown delineation. This chapter shows the contribution of performing an automatic individual tree crown delineation over the wider forest areas. The individual tree crown delineation is composed of a five-step framework, which is unique in its automated determination of dominant crown sizes in a forest area and its adaption of the LiDAR-AGB model developed for the purpose of validation the method. This framework correctly delineated 84% and 88% of the tree crowns in the two forest study areas which is mostly dominated with lowland dipterocarp trees. Thirdly, parametric and non-parametric modelling approaches are proposed for modelling forest structural attributes. Selected modelling methods are compared for predicting 4 forest attributes, volume (V), basal area (BA), height (Ht) and aboveground biomass (AGB) at the species level. The AGB modelling in this paper is extracted using the LiDAR derived variables from the automated individual tree crown delineation, in contrast to the earlier AGB modelling where it is derived based on the trees that were mapped in the field. The selected non-parametric method included, k-nearest neighbour (k-NN) imputation methods: Most Similar Neighbour (MSN) and Gradient Nearest Neighbour (GNN), Random Forest (RF) and parametric approach: Ordinary Least Square (OLS) regression. To compare and evaluate these approaches a scaled root mean squared error (RMSE) between observed and predicted forest attribute sampled from both forest site was computed. The best method varied according to response variable and performance measure. OLS regression was to found to be the best performance method overall evidenced by RMSE after cross validation for BA (1.40 m2), V (1.03 m3), Ht (2.22 m) and AGB (96 Kg/tree) respectively, showed its applicability to wider conditions, while RF produced best overall results among the non-parametric methods tested. This thesis concludes with a discussion of the potential of LiDAR data as an independent source of important forest inventory data source when combined with appropriate designed sample plots in the field, and with appropriate modelling tools.

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Werner, Ute. „Simulation of nonadiabatic dynamics and time-resolved photoelectron spectra in the frame of time-tependent density functional theory“. Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16351.

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Ziel dieser Arbeit war die Entwicklung einer allgemein anwendbaren Methode für die Simulation von ultraschnellen Prozessen und experimentellen Observablen. Hierfür wurden die Berechnung der elektronischen Struktur mit der zeitabhängigen Dichtefunktionaltheorie (TDDFT) und das Tully-Surface-Hopping-Verfahren für die nichtadiabatische Kerndynamik auf der Basis klassischer Trajektorien miteinander kombiniert. Insbesondere wurde eine Beschreibung der nichtadiabatischen Kopplungen für TDDFT entwickelt. Diese Methode wurde für die Simulation noch komplexerer Systeme durch die Tight-Binding-Näherung für TDDFT erweitert. Da die zeitaufgelöste Photoelektronenspektroskopie (TRPES) ein exzellentes experimentelles Verfahren für die Echtzeitbeobachtung von ultraschnellen Prozessen darstellt, wurde eine TDDFT-basierte Methode für die Simulation von TRPES entwickelt. Der Methode liegt die Idee zu Grunde, das System aus Kation und Photoelektron näherungsweise durch angeregte Zustände des neutralen Moleküls oberhalb der Ionisierungsgrenze zu beschreiben. Um diese Zustände mit TDDFT berechnen zu können wurde eine Beschreibung der Übergangsdipolmomente zwischen angeregten TDDFT-Zuständen entwickelt. Des Weiteren wurden Simulationen im Rahmen des Stieltjes-Imaging-Verfahrens, das eine Möglichkeit der Rekonstruktion des Photoelektronenspektrums aus den spektralen Momenten bietet, durchgeführt. Diese spektralen Momente wurden aus den diskreten TDDFT-Zuständen berechnet. Die breite Anwendbarkeit der entwickelten theoretischen Methoden für die Simulation von komplexen Systemen wurde an der Photoisomerisierung in Benzylidenanilin sowie der ultraschnellen Photodynamik in Furan, Pyrazin und mikrosolvatisiertem Adenin illustriert. Die dargestellten Beispiele demonstrieren, dass die nichtadiabatische Dynamik im Rahmen von TDDFT bzw. TDDFTB sehr gut für die Untersuchung und Interpretation der ultraschnellen photoinduzierten Prozesse in komplexen Molekülen geeignet ist.
The goal of this thesis was the development of a generally applicable theoretical framework for the simulation of ultrafast processes and experimental observables in complex molecular systems. For this purpose, a combination of the time-dependent density functional theory (TDDFT) for the description of the electronic structure with the Tully''s surface hopping procedure for the treatment of nonadiabatic nuclear dynamics based on classical trajectories was employed. In particular, a new approach for the calculation of nonadiabatic couplings within TDDFT was devised. The method was advanced for the description of more complex systems such as chromophores in a solvation shell by employing the tight binding approximation to TDDFT. Since the time-resolved photoelectron spectroscopy (TRPES) represents a powerful experimental technique for real-time observation of ultrafast processes, a TDDFT based approach for the simulation of TRPES was developed. The basic idea is the approximate representation of the combined system of cation and photoelectron by excited states of the neutral species above the ionization threshold. In order to calculate these states with TDDFT, a formulation of the transition dipole moments between excited states within TDDFT was devised. Moreover, simulations employing the Stieltjes imaging (SI) procedure were carried out providing the possibility to reconstruct photoelectron spectra from spectral moments. In this work, the spectral moments were calculated from discrete TDDFT states. The scope of the developed theoretical methods was illustrated on the photoisomerization in benzylideneaniline as well as on the ultrafast photodynamics in furan, pyrazine, and microsolvated adenine. The examples demonstrate that the nonadiabatic dynamics simulations based on TDDFT and TDDFTB are particularly suitable for the investigation and interpretation of ultrafast photoinduced processes in complex molecules.

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McGuire, Raymond. „Does the invasive tree, Falcataria moluccana facilitate high population density of the invasive Puerto Rican frog, Eleutherodactylus coqui? /“. University of Hawai'i at Hilo, 2009. http://proquest.umi.com/pqdweb?did=1666865381&sid=1&Fmt=2&clientId=23658&RQT=309&VName=PQD.

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Norgrove, Lindsey Ann. „Crop, weed and soil response to tree density and implications for nutrient cycling in a tropical agrisilvicultural system“. Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324993.

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Marappullige, Priyantha Kumara. „The impacts of tree density on the physical and biological characteristics of planted Mangrove stands in Sri Lanka“. Thesis, Edinburgh Napier University, 2011. http://researchrepository.napier.ac.uk/Output/4467.

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Survival, growth, aboveground biomass production, belowground biomass production, sediment accretion, soil surface elevation dynamics, sediment carbon and C/N ratio, sediment N and P, sediment 13C and 15N, sediment texture and macrofauna community structure, were studied in experimental treatments planted with four different densities (6.96, 3.26, 1.93 and 0.95 seedlings m-2) of the mangrove Rhizophora mucronata in Palakuda, Puttalam Lagoon, Sri Lanka. The first three parameters were also studied at a replicated experiment at Rekawa Lagoon, Sri Lanka. For both Palakuda (1,171days) and Rekawa (702 days) sites, the highest tree density (6.96 seedlings m-2) showed significantly higher % survival: means (±S.E.) of 93.4 (± 1.1) and 91.2 (± 1.38) respectively. The measures of individual trees (tree height, stem diameter, number of leaves, leaf area, number of branches, number of prop roots ) did not differ among treatments (p>0.05) for both sites. In contrast, the aboveground biomass responded significantly to planting density with higher plantation densities equating to greater biomass: 10772 ± 24 and 9904 ± 18.1g dry weight m-2 for Palakuda (1,171days) and Rekawa (702 days) respectively. The belowground biomass at Palakuda (1370 days) varied significantly between the densities with the highest belowground biomass (105.41 ± 6.98 g m-2) in the highest tree density. The same tree density had the highest numbers of fine roots m-2 for efficient absorption of nutrients. Higher tree densities accumulated more N in their sediments while the sediment phosphate was not different between the densities. Sediment ‰ 13C, ‰ 15N and C/N ratios ranged between -16.41 to -14.58, 2.80 to 2.40 and 9.32 to 7.85 respectively and were independent of the planting density. The 13C values indicated a potential mix of seagrass C and mangrove C in sediments of the treatments; the highest tree density (6.96 seedlings m-2) had significantly higher % sediment carbon (0.68 ± 0.04) compared with the unplanted controls (0.46 ± 0.05). Rates of surface accretion were 13.0 (± 1.3), 10.5 (± 0.9), 8.4 (± 0.3), 6.9 (± 0.5) and 5.7 (± 0.3) mm year-1 at planting densities of 6.96, 3.26, 1.93, 0.95, and 0 (unplanted control) seedlings m-2 respectively, showing highly significant differences among treatments. Mean (± SE) rates of surface elevation change were much lower than rates of accretion at 2.8 (± 0.2), 1.6 (± 0.1), 1.1(± 0.2), 0.6 (± 0.2) and -0.3 (± 0.1) mm year-1 for 6.96, 3.26, 1.93, 0.95, and 0 seedlings m-2, respectively. The community structure of the sediment macrofauna was unchanged between the treatments; that is likely to be the result of unchanged sediment texture and unavailability of mangrove derived carbon as the major food source. This study demonstrated the role of higher mangrove densities in enhancing the rates of sediment accretion and surface elevation processes that may be crucial in mangrove ecosystems' adaptation to sea-level rise. There was no evidence that increasing plant density evoked a trade-off with growth and survival of the planted trees during their early 1171 days of growth. While these potential processes need further research, the enhanced survival at high densities suggests the potential to use high plantation densities to help mitigate sea-level rise effects by encouraging positive sediment surface elevation. Higher biomass production in higher densities would also help faster sequestration of atmospheric carbon dioxide.

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Ghashim, Ehssan. „Une classe d'intervalles bay??siens pour des espaces de param??tres restreints“. Mémoire, Universit?? de Sherbrooke, 2013. http://savoirs.usherbrooke.ca/handle/11143/52.

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Ce m??moire traite d'une m??thode bay??sienne, analys??e par Marchand et Strawderman (2013), pour la construction d'intervalles bay??siens pour des mod??les de densit??s continues avec contrainte sur l'espace des param??tres ??. Notamment, on obtiendra une classe d'intervalles bay??siens I??0,??(.), associ??s ?? la troncature d'une loi a priori non informative ??0 et g??n??r??s par une fonction de distribution ??(.), avec une probabilit?? de recouvrement born??e inf??rieurement par 1-??/1+??. Cette classe inclut la proc??dure HPD donn??e par Marchand et Strawderman (2006) dans le cas o?? la densit?? sous-jacente d'un pivot est sym??trique. Plusieurs exemples y illustrent la th??orie ??tudi??e. Finalement, on pr??sentera de nouveaux r??sultats pour la probabilit?? de recouvrement des intervalles bay??siens appartenant ?? la classe ??tudi??e pour des densit??s log-concaves. Ces r??sultats ??tablissent la borne inf??rieure ?? 1- 3??/2 et g??n??ralisent les r??sultats de Marchand et al.(2008) tenant sous une hypoth??se de sym??trie.

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Grudd, Håkan. „Tree Rings as Sensitive Proxies of Past Climate Change“. Doctoral thesis, Stockholm University, Department of Physical Geography and Quaternary Geology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-1034.

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In the boreal forests of the Northern Hemisphere, time series of tree-ring width (TRW) and maximum density in the latewood (MXD) are highly correlated to local instrumental summer-temperature data and are thus widely used as proxies in high-resolution climate reconstructions. Hence, much of our present knowledge about climatic variability in the last millennium is based on tree-rings. However, many tree-ring records have a lack of data in the most recent decades, which severely hampers our ability to place the recent temperature increase in a longer-timescale perspective of natural variability.

The main objective of this thesis is to update and extend the Torneträsk TRW and MXD records in northern Sweden. Local instrumental climate-data is used to calibrate the new tree-ring records. The results show that TRW is mainly forced by temperature in the early growing season (June/July) while MXD has a wider response window (June – August) and has a higher correlation to temperature. Two reconstructions of summer temperature are made for (i) the last 7,400 years based on TRW, and (ii) the last 1,500 years based on a combination of TRW and MXD. The reconstructions show natural variability on timescales from years to several centuries. The 20th century does not stand out as a notably warm period in the long timescale perspective. A medieval period from AD 900 – 1100 is markedly warmer than the 20th century.

The environmental impact from a large explosive volcanic eruption in 1628/1627 BC is analysed in the tree rings of 14C-dated bog pines in south-central Sweden and in absolutely-dated subfossil pines from Torneträsk. The results show evidence of an impact in the southern site at approximately this time but no detectable impact in the North.

Subfossil trees of Fitzroya cupressoides in southern Chile were 14C-dated to approx. 50,000 years BP and amalgamated into a 1,229-year TRW chronology. This tree-ring record is the oldest in the world. The variability in this Last-glacial chronology is similar to the variability in present-day living trees of the same species. These results suggest that the growth–forcing mechanisms 50,000 years ago were similar to those at present.

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DeYoung, Clara. „Biomass Estimation Using the Component Ratio Method for White Oak“. Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50421.

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With higher demands on biomass, the ability to accurately estimate the amount in a stand is more important now than ever before. Existing models currently in use by the Forest Inventory and Analysis (FIA) program of the United States Department of Agriculture (USDA) Forest Service include the Component Ratio Method (CRM). However, testing of the CRM models is needed to validate and calibrate them. The objective of this research was to test and develop a system of equations capable of producing consistent volume and biomass estimates for standing trees of commercially important hardwood species in the southeastern United States. Testing and comparing was done through use of new and legacy data to establish component ratios of trees and contrast these results to those from existing models. Specifically, analyses were completed for models of merchantable and whole stem volume, wood densities models and averages, and the component ratios for wood, bark, branches, and foliage. The existing models were then calibrated and adjusted. Results on accuracy and fitted results of updated models are reported, along with testing the effects of applying updated models over the state of Virginia.
Master of Science

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OZANNE, LAURENT. „Interferences spectrales a tres haute densite dans les spectres infrarouge de co 2. Mesures et modelisation ecs“. Paris 6, 1998. http://www.theses.fr/1998PA066269.

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Ce travail nous a permis d'observer et d'interpreter les effets des interferences spectrales dans les bandes v 3 et 3v 3 de co 2 sous tres haute pression d'helium et d'argon, a temperature ambiante. Une dependance non lineaire en densite de l'absorption, clairement mise en evidence dans l'aile, est interpretee comme un effet un volume fini des molecules. Nous avons observe des deplacements globaux significatifs que nous avons relie au dephasage vibrationnel et un effet de retrecissement des bandes, phenomene observe pour la premiere fois pour des bandes -, dont nous avons montre qu'il etait directement relie a l'importance des couplages interbranches. Enfin, nous avons pu confronter les sections efficaces de base, extraites des experiences par une inversion basee sur le modele ecs, avec celles deduites des calculs ab initio bases sur un potentiel intermoleculaire propose recemment. Ceci nous a permis de determiner le degre de precision de cette methode d'inversion et de valider le formalisme ecs, qui s'avere en conclusion de cette etude capable de predire le profil spectral des bandes de co 2 sur une tres vaste gamme de conditions experimentales.

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Mercenne, Frédéric. „Influence de la composition des lipoproteines de haute densite sur les echanges de lipides avec les lipoproteines de tres basse densite en presence de cetp in vitro“. Dijon, 1995. http://www.theses.fr/1995DIJOPE03.

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Lima, Antonio Jose Temistocles de. „CARACTERÍSTICAS AGRONÔMICAS, MORFOGÊNICAS, ESTRUTURAIS E DEMOGRÁFICAS DO CAPIM-MARANDU EM SISTEMAS SILVIPASTORIS E MONOCULTURA NA REGIÃO PRÉ-AMAZÔNICA“. Universidade Federal do Maranhão, 2015. http://tedebc.ufma.br:8080/jspui/handle/tede/554.

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Made available in DSpace on 2016-08-17T17:11:01Z (GMT). No. of bitstreams: 1 DISSERTACAO ANTONIO JOSE TEMISTOCLES DE LIMA.pdf: 715020 bytes, checksum: 68b49623ce4ed62a176b2b2a66b4f47d (MD5) Previous issue date: 2015-03-04
FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO
The objective of this work was to evaluate the agronomic characteristics, morfogenicas and structural, in addition to the tiller density and dynamics of tillering palisadegrass in silvopastoral systems with three densities of palms of babassu and in monoculture. The experiment was conducted in the municipality of de Matinha-MA. The experimental design was a completely randomized design, with the arrangement in split plot design with 6 repetitions for the evaluation of agronomic characteristics and 30 repetitions for the characteristics morfogenicas and structural, and factorial 4x5 being (four densities of palm trees and five generations of tillers and ten repetitions) for demographic characteristics. The plots were composed of the densities (80, 131, 160 adult palm trees/ha) and monoculture and the subplots stations (rainy and dry season). For total production of fodder, leaf production, the density with 80 palm/ha presented values equal and/or higher than the monoculture and the other densities. While that for rate of leaf appearance, phyllochron, leaf elongation rate, rate of elongation of the stem, the results obtained in SSP's during the dry period were higher than the monoculture, while that in the rainy season, the SSP with 131 palm/ha was higher than the other densities and monoculture for the characteristics of rate of leaf appearance and leaf elongation rate. Already for the structural characteristics; the duration of life of leaf did not differ between periods and between treatments, with respect to the final length leaf, in the dry season the system with 160 palm/ha was greater than the monoculture, however, did not differ from other SSP's, for the rainy season, the SSP's showed similar results to monoculture. For the tiller density live, during the rainy season the systems 80 and 131 palm/ha differed from monoculture, however, the system of 131 palm/ha obtained the highest number of tillers killed. For the rate of appearance, the system of 80 palm/ha showed similar results to monoculture and different to other SSP's in generations one, two, three and five. For the mortality rate, the system with 131 palm/ha was the only treatment the highest rate in all generations in relation to monoculture. For the rate of survival, it was observed that the treatment with 160 palm/ha that equated to the results obtained in monoculture in five generations. In relation to the index of stability of tillers, in the first two generations the system with 80 palm/ ha was higher than the other densities, to the following generations the values obtained were equaled. For the volumetric density, in the rainy season, the system of 80 palm/ha was superior to the systems 131 and 160 palm/ha, however, did not differ in monoculture. Silvopastoral Systems with 80 palm/ha of babassu promote higher total production of grass, leaves, stalks and lower rate of senescence, however for some characteristics as TApF, TAIF and CFF pastures with 131 palm/ha had a better performance. Monoculture and SSP with 80 and 131 palm/ha have higher rate of renewal of tissues, with high rates of occurrence and mortality of tillers, resulting in greater tiller density. However, the pasture with 80 and 160 palm/ha and the monoculture showed high survival rates of suckers along the generations as compensation mechanism. Thus, densities of palm trees between 131 and 160 palm/ha can compromise the renewal of the canopy, due to low TApPb.
Objetivou-se com presente trabalho avaliar as características agronômicas, morfogênicas e estruturais, além da densidade populacional de perfilhos e dinâmica de perfilhamento do capim-Marandu em sistemas silvipastoris com três densidades de palmeiras de babaçu e em monocultura. O experimento foi conduzido no Município de Matinha-MA. O delineamento adotado foi o inteiramente casualizado, com o arranjo em parcelas subdivididas com 6 repetições para a avaliação das características agronômicas e 30 repetições para as características morfogênicas e estruturais e, arranjo fatorial 4x5 sendo (quatro densidades de palmeiras e cinco gerações de perfilhos e dez repetições) para as características demográficas. As parcelas foram constituídas pelas densidades (80, 131, 160 palmeiras adultas/ha) e monocultura e nas subparcelas as estações (Chuvosa e Seca). Para produção total de forragem, produção de folhas, a densidade com 80 palm/ha apresentou valores iguais e/ou superiores a monocultura e as demais densidades. Enquanto que para taxa de aparecimento foliar, filocrono, taxa de alongamento foliar, taxa de alongamento do colmo, os resultados obtidos nos SSP s no período seco foram superiores a monocultura, enquanto que no período chuvoso, o SSP com 131 palm/ha foi superior as demais densidades e a monocultura para as características de taxa de aparecimento foliar e taxa de alongamento foliar. Já para as características estruturais; a duração de vida da foliar não diferiu entre períodos e entre tratamentos, com relação ao comprimento final foliar, no período seco o sistema com 160 palm/ha foi superior a monocultura, entretanto, não diferiu do demais SSP s, para o período chuvoso, os SSP s apresentaram resultados semelhantes a monocultura. Para a densidade populacional de perfilhos vivos, no período chuvoso os sistemas de 80 e 131 palm/ha diferiram da monocultura, entretanto, o sistema de 131 palm/ha obteve maior número de perfilhos mortos. Para a taxa de aparecimento, o sistema de 80 palm/ha apresentou resultados semelhantes a monocultura e diferentes aos demais SSP s nas gerações um, dois, três e cinco. Para a taxa de mortalidade, o sistema com 131 palm/ha foi o único tratamento a apresentar maior taxa em todas as gerações em relação a monocultura. Para a taxa de sobrevivência, observou-se que o tratamento com 160 palm/ha que equiparou-se aos resultados obtidos na monocultura nas cinco gerações. Já em relação ao índice de estabilidade de perfilhos, nas duas primeiras gerações o sistema com 80 palm/ ha foi superior as demais densidades, para as gerações seguintes os valores obtidos foram igualando-se. Para a densidade volumétrica, no período chuvoso o sistema de 80 palm/ha foi superior aos sistemas de 131 e 160 palm/ha, entretanto, não diferiu da monocultura. Sistemas silvipastoris com 80 palm/ha de babaçu promovem maior produção total de forragem, folhas, colmos e menor taxa de senescência, no entanto para algumas características como TApF, TALF e CFF as pastagens com 131 palm/ha tiveram melhor desempenho. Monocultura e SSP com 80 e 131 palm/ha possuem maior velocidade de renovação de tecidos, com altas taxas de aparecimento e de mortalidade de perfilhos, resultando em maior densidade populacional de perfilhos. No entanto, as pastagens com 80 e 160 palm/ha e a monocultura apresentaram altas taxas de sobrevivência de perfilhos ao longo das gerações como mecanismo de compensação. Dessa forma, densidades de palmeiras entre 131 e 160 palm/ha podem comprometer a renovação do dossel, devido à baixa TApPb.

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Carroll, Mark. „A stereological study assessing the validity of using endobronchial biopsies to assess mast cell density in the central and peripheral bronchial tree“. University of Western Australia. School of Medicine and Pharmacology, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0005.

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[Tuncated abstract] There has been longstanding concern over whether endobronchial biopsies adequately represent inflammation throughout the bronchial tree in diseases such as asthma, despite the endobronchial biopsy technique having been used frequently to assess airway inflammation in research settings. There has also been ongoing debate about whether endobronchial biopsies should be assessed by new, unbiased, three-dimensional (3D) stereological techniques instead of traditional, two-dimensional (2D) non-stereological techniques. Therefore, the aims of this study were: (i) to investigate whether endobronchial biopsies represent the density of mast cells in the large and small airways, in alveolar walls and in the lung as a whole (ii) to use both stereological and non-stereological methods to address this question, and where possible, to compare the results of these two approaches. '...' Mast cell density in biopsies was not related to mast cell density immediately adjacent to the biopsy site or to mast cell density in the total airway wall in the large airways, the inner airway wall in the small airways, the walls of the alveoli or the lung as a whole. In general, measurements of mean mast cell density on biopsies to a depth of 100µm below the basement membrane were poorly related to mean mast cell density in other compartments of the lung. Mean 3D and 2D mast cell densities were strongly correlated (r 0.9, p < 0.005) and where both methods were used, results were similar. The mean height and area profile of a mast cell were approximately 12µm and 68µm2 respectively. In disk-shaped IUR lung samples, percent shrinkage in height due to paraffin processing was systematically greater than percent radial shrinkage by an average of approximately 4 times. Cavalieri lung volumes were systematically smaller than displacement volumes by an average of 14%. Any given endobronchial biopsy is unlikely to represent mast cell density around the airway wall generally in the vicinity of the biopsy site. However, the average of at least 4 biopsies from different sites in the proximal airways can be used to both represent mean mast cell density in the inner airway wall of the large airways, and act as the basis for inter-subject comparisons of mean mast cell density in the total airway wall of the small airways. On biopsies, mast cell counts should be measured over the entire inner airway wall not just to a depth of 100µm or less below the basement membrane. 3D mast cell densities obtained by stereological methods are closely related to 2D mast cell densities obtained by non-stereological methods and are likely to result in similar conclusions. Lung volumes are smaller when measured by the Cavalieri method than when measured by fluid displacement. Shrinkage of isotropic uniform random samples of human lung tissue due to paraffin processing is anisotropic. The mean volume of a mast cell in the human lung is likely to be much smaller than that reported previously for monkey lungs.

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48

Wenzel-Bartens, Julia. „Development of Urban Tree Growth Models Based on Site and Soil Characteristics“. Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/29625.

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Trees provide numerous benefits crucial to urban environments, yet poor growing conditions often prevent trees from reaching their genetic potential for growth, longevity, and ecosystem function. To overcome these limitations, greater understanding of tree growth in the urban environment is needed. The goal of this research project was therefore to characterize a broad suite of soil characteristics associated with urban tree plantings and evaluate their suitability for modeling physical dimensions and growth rates of urban trees. A series of observational studies and experiments was conducted on urban soils inhabited by two tree species (Zelkova serrata (Thunb.) Mikano and Quercus phellos L.) in Washington, DC and one tree species (Quercus virginiana Mill.) in Jacksonville, FL – two major metropolitan areas of the eastern United States with contrasting climate and soils. Characterization of urban soil attributes within cities revealed low variability for some properties (soil texture, pH, and certain plant nutrients with coefficients of variation (CV) below 0.5), but high variability (CV>1.0) for others (nitrate, ammonium, copper, and zinc). This is dependent on the location. These findings suggest that tree planting site evaluations may not require measurements for all soil properties and that representative sampling may be sufficient to accurately characterize most soil properties within a city. Field assessment of urban tree soils also revealed that conventional measures of soil compaction are difficult to obtain due to obstructions by roots and other foreign objects. To address the critical need for efficient and reliable assessment of soil compaction around urban trees, an experiment was conducted to develop bulk density estimation models for four common soil texture classes using soil strength and soil moisture as predictor variables. These models provided medium (0.42) to high (0.85) coefficients of determination when volumetric water content (VWC) was log transformed, demonstrating that measurements of soil texture, strength, and moisture can provide rapid, reliable assessment of soil compaction. Tree growth modeling focused on three response variables: canopy projection (CP), canopy volume (CV), and peak-increment-area age (PIA). To calculate PIA, tree-ring analysis was used to determine the age at which maximal trunk diameter growth occurred between transplanting and time of sampling. Because Q. virginiana has difficult-to-distinguish growth rings, an intensive tree-ring analysis of cores collected from these trees was conducted. The analysis revealed interseries correlation coefficients of up to 0.66, demonstrating that Q. virginiana can be aged with fairly high confidence in an urban setting. Empirical models developed for all three tree species using the suite of soil and site variables explained 25% – 83% of the observed variability in tree physical dimensions and growth rates. Soil pH was found to be a significant predictor variable for the majority of growth models along with nutrients such as Fe, B, Mn, and Zn, which are also associated with soil alkalinity. Models for PIA possessed the highest coefficient of determination, suggesting that measurements of soil conditions can be used confidently to predict the age at which growth rate subsides in these species. CV and CP were not predicted as well by soil-related variables, presumably because above-ground constraints such as pruning and building encroachment can affect canopy size without necessarily affecting growth rate. Certain prediction models for all three species included predictor variables with counterintuitive influences on tree growth (e.g., negative influences of soil depth on Q. phellos and soil volume on Q. virginiana), suggesting that either these urban trees are responding to these variables in a novel manner or that variables unaccounted for in these models (perhaps related to urbanization or high vehicular traffic) are concomitantly influencing tree growth.
Ph. D.

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Veatch, William Curtis. „Quantifying the Effects of Forest Canopy Cover on Net Snow Accumulation at a Continental, Mid-Latitude Site, Valles Caldera National Preserve, NM, USA“. Thesis, The University of Arizona, 2008. http://hdl.handle.net/10150/193352.

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Although forest properties are known to influence snowpack accumulation and spring runoff, the processes underlying the impacts of forest canopy cover on the input of snowmelt to the catchment remain poorly characterized. In this study I show that throughfall and canopy shading can combine to result in maximal snowpacks in forests of moderate canopy density. Snow depth and density data taken shortly before spring melt in the Jemez Mountains of New Mexico show strong correlation between forest canopy density and snow water equivalent, with maximal snow accumulation in forests with density between 25 and 45%. Forest edges are also shown to be highly influential on local snow depth variability, with shaded open areas holding significantly deeper snow than either unshaded open or deep forest areas. These results are broadly applicable in improving estimates of water resource availability, predicting the ecohydrological implications of vegetation change, and informing integrated water resources management.

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Tarelkin, Yegor. „Radial Patterns of Wood Features Reveal Site-Specific Tree Growth Dynamics in the Congo Basin“. Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/273503.

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Les forêts tropicales couvrent environ 7% de la surface terrestre et stockent environ 25% du carbone terrestre. Elles jouent un rôle important dans les cycles biogéochimiques et fournissent divers services écosystémiques. Cependant, elles sont menacées par l’activité anthropique et le changement climatique. Il y a un besoin pressant de mieux comprendre les effets du changement climatique sur la croissance des arbres afin de mieux estimer son impact sur la composition des forêts et leur capacité à fournir leurs services.Jusqu’à récemment, les réponses des forêts aux changements climatiques ont été étudiées via des expérimentations en laboratoire ou en rapportant les changements à l’échelle des populations. Cependant, notre connaissance de l’influence des changements climatiques graduels sur la croissance ligneuse reste limitée. L’étude des cernes de croissance a permis la reconstruction du climat passé et l’étude de son influence sur la dynamique de croissance des arbres dans les régions tempérées. Son application dans un contexte tropical reste cependant limitée par l’absence d’une saisonnalité marquée des facteurs limitants la croissance. La distinction des cernes de croissance chez les espèces tropicales est très variable et des études supplémentaires sont nécessaires pour correctement les identifier et les utiliser dans les études dendrochronologiques.Dans cette thèse, nous explorons le potentiel d’utilisation de l’anatomie et de la densité du bois dans l’étude des réponses des arbres aux changements climatiques. Nous évaluons la variabilité anatomique du coeur à l’écorce et la manière dont le climat l’influence. Le travail est subdivisé en trois chapitres, chacun répondant à une question spécifique. Plus particulièrement, nous avons étudié (i) la variabilité de la distinction et de l’anatomie des cernes de croissance dans les tropiques, (ii) la relation entre l’anatomie et la densité du bois ainsi que son potentiel d’utilisation comme un proxy pour estimer variabilité anatomique et (iii) l’influence de la saisonnalité des précipitations sur la rythmicité de la croissance des arbres via leurs profils de densité du bois.En premier lieu, nous avons décrit les traits anatomiques impliqués dans la démarcation des limites des cernes de croissance et évalué leur contribution à la distinction des cernes. Nous avons constaté une grande variabilité intra et interspécifique et mis en avant le fait que les définitions actuelles de la distinction des cernes ne décrivent pas suffisamment la complexité de l’anatomie du bois dans les tropiques. Au lieu de se concentrer sur la détection des cernes, nous proposons d’étudier la variabilité des traits anatomiques depuis le coeur jusqu’à l’écorce dans le but de reconstruire la croissance ligneuse passée et estimer les effets du climat.Ensuite nous avons automatisé les mesures de proportions de parenchyme et de vaisseaux ainsi que le ratio lumen/diamètre total des fibres dans le plan transversal de la moelle à l’écorce. Nous les avons étudiés en parallèle avec des profils à haute résolution de la densité du bois de huit espèces. Nous avons montré que la densité du bois est influencée par l’anatomie des fibres et que la relation entre l’anatomie et la densité du bois dépend de l’espèce. Notre étude suggère qu’il est possible d’utiliser les profils de la densité du bois comme un proxy pour étudier la variabilité de l’anatomie du bois.Finalement, nous avons utilisé les profils de densité afin de comparer les patterns de croissance ligneuse de 13 espèces le long d’un gradient de précipitation. Nous avons utilisé l’analyse en ondelettes afin de dériver trois descripteurs de croissance :la régularité, la périodicité et l’amplitude des variations. Nous avons montré que la saisonnalité de précipitations influence la régularité de la croissance ligneuse et que les variations sont plus abruptes dans les sites avec une saisonnalité plus marquée. Nous avons aussi montré que les espèces décidues et sempervirentes ne réagissent pas de la même façon aux variations des patterns de précipitations.Nous pensons que ces résultats vont favoriser l’émergence d’outils prometteurs pour étudier la croissance des arbres et sa relation avec le climat. L’automatisation des mesures des traits anatomiques et l’utilisation des profils de densité du bois comme proxies vont aider à diminuer le temps de traitement des échantillons et augmenter leur nombre ainsi que la puissance des traitements statistiques. Par la description très fine des signaux cycliques qu’elle permet, l’analyse en ondelettes ouvre de nouvelles perspectives pour la description des profils de variation de la densité du bois et donc l’interprétation de la dynamique de croissance des arbres.
Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished

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