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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Potentiel d'établissement d'essences forestières et fruitières en tourbières résiduelles

Bussières, Julie 11 April 2018 (has links)
La plantation d'arbres ou d'arbustes fruitiers figure parmi les options de réaménagement complémentaires à la restauration des tourbières résiduelles. Aucune étude n'avait toutefois été effectuée concernant le potentiel de telles plantations dans l'est du Canada. Le présent projet avait pour principal objectif de dresser un portrait des plantations existantes en tourbières résiduelles canadiennes, afin de connaître le potentiel de différentes essences forestières et d'une espèce d'arbuste fruitier (l'Aronia noir) à croître sur substrat tourbeux. Les essences forestières montrant de bonnes croissances sont l'Épinette noire et le Mélèze laricin. L'Érable rouge, le Pin gris, le Pin sylvestre et l'Aronia noir ont présenté certaines difficultés d'implantation ou de croissance, mais demeurent potentiellement intéressants. Les plantations de Peupliers hybrides sur tourbière résiduelle se sont avérées un échec. Une régie de la fertilisation comportant de faibles doses d'azote, de phosphore et de potassium est un atout pour des plantations forestières ou fruitières de ce type. Le présent projet a donc permis de mettre en évidence le réel potentiel d'établissement de certaines espèces forestières et fruitières en tourbières résiduelles dans l'Est du Canada.
42

Le blues des prisonniers à Angola (1930-1960) : mécanisme de survie, d’émancipation et d’espoir

Garriss, Jacqueline January 2017 (has links)
Cette recherche vise l’étude des chants de style blues enregistrés à la plantation pénale Angola (Pénitencier d’État de la Louisiane) en 1934 par l’ethnomusicologue John Avery Lomax et en 1959 par l’ethnomusicologue Harry Oster. Angola est synonyme de violence, d’abus et de racisme à l’endroit des prisonniers afro-américains, tout en répliquant le modèle esclavagiste. Les détenus travaillent de longues heures dans les champs, sous le soleil brûlant de la Louisiane. Ils y sont mal nourris, mal logés, fouettés et ne sont pas rémunérés pour leur labeur. Lorsque Lomax et Oster visitent le pénitencier, ils trouvent un système calqué sur l’esclavage, et documentent le blues qui y est joué. Cette musique, comme les chants des esclaves sur les anciennes plantations, témoigne de la réalité afro-américaine dans le Sud des États-Unis. Elle parle du désespoir, de la violence, de l’injustice, de l’abandon et de l’impuissance, mais elle est aussi un puissant témoignage de l’espoir et de la résilience afro-américaine. Ces chants permettent de reconstruire partiellement la vie de certains détenus, pour qui les enregistrements réalisés par Oster demeurent les seules preuves tangibles de leur existence. Cette recherche vise à redonner une voix, par le biais de la musique, à ces hommes marginalisés et oubliés de la prison Angola.
43

Le bois mort et les Coléoptères associés dans les plantations de pin maritime (Pinus pinaster, L.) : implications possibles pour la gestion durable des forêts et l’élaboration d’indicateurs de biodiversité

Brin, Antoine 10 December 2008 (has links)
Le bois mort a été retenu comme l’un des indicateurs de biodiversité pour la gestion durable des forêts. L’objectif de la thèse est de tester la pertinence de cet indicateur dans le contexte des forêts de plantation grâce à l'acquisition de données expérimentales. L’approche est focalisée sur les Coléoptères qui représentent 20% des espèces saproxyliques. La richesse spécifique et la composition des assemblages sont influencées par des variables à 3 échelles: la pièce de bois mort (diamètre, stade de décomposition et type), le peuplement (volume de bois mort, densité, couvert) et le paysage (% de couvert en pin maritime, feuillus et coupe rase). La diversité des pièces de bois mort de diamètre supérieur à 15cm constitue un bon indicateur de la richesse locale en Coléoptères saproxyliques. Un modèle de dynamique du bois mort a été développé, permettant d’évaluer les incidences potentielles de nouvelles pratiques sylvicoles sur la biodiversité des Coléoptères saproxyliques. / Dead wood has been selected as one of the biodiversity indicators for the assessment of sustainable forest management. We investigated the relevance of this indicator in forest plantations with experimental data. Our approach was focus on beetles which represent 20% of saproxylic species. Effects of environmental variables on species richness and composition of assemblages occurred at three spatial scales : the piece of wood (diameter, decomposition stage and type), the stand (volume of dead wood, density of stems, canopy cover) and the landscape (% of maritime pine stands,% of deciduous stands and % of clear-cut areas). Diversity of dead wood above 15 cm in diameter appeared to be a good indicator of the local species richness of saproxylic beetles. A model of dead wood dynamic has been proposed so as to assess impacts of new forestry practices on saproxylic beetles diversity.
44

Atlantic Bodies: Health, Race, and the Environment in the British Greater Caribbean

Johnston, Katherine Margaret January 2016 (has links)
This dissertation examines the relationship between race and bodily health in the British West Indies and the Carolina/Georgia Lowcountry from the late seventeenth through the early nineteenth century. In the eighteenth century, planters often justified African slavery by claiming that Africans, unlike Europeans, had bodies particularly suited to labor in warm climates. Historians have tended to take these claims as evidence of a growing sense of biological race in plantation societies. Much of this work, though, relies on published sources. This dissertation examines these public sources, including medical manuals, natural histories, and political pamphlets, alongside private sources, particularly the personal correspondence of planters and slaveholders to uncover a different story of race and slavery. These two source types reveal significant discrepancies between planters’ public rhetoric and private beliefs about health, race, and the environment in plantation societies. First, correspondence between the Greater Caribbean and Britain demonstrates that health and disease did not contribute to the development of racial slavery in the Atlantic. Second, these sources show how and why planters manipulated public conceptions of climate and health to justify and maintain a system of racial slavery. Planters insisted on climate-based arguments for slavery in spite of their experiences in the Americas, rather than because of them. Slaveholders contributed to the construction of a biological concept of race by making arguments about health differences between Africans and Europeans that they neither experienced nor believed. Nevertheless, their arguments entered the public record and consciousness, and the resultant development of racial thinking had profound consequences that continue to the present day. This dissertation demonstrates the critical importance of the environment to the history of race.
45

The enchanted plantation: literature, speculation, and the credit economy in Virginia, 1688-1754”

McLoone, Jr., Robert Bruce 01 May 2013 (has links)
"The Enchanted Plantation: Literature, Speculation, and the Credit Economy in Virginia, 1688-1754" examines the beginnings of a regionally-based literary culture in colonial Virginia and focuses specifically on texts that either originate from, or have close ties to, the colony's political and administrative capital at Williamsburg. The dissertation argues that literary practices and literary production in Virginia at this time were crucial to the imagination and material construction of Virginia's unevenly-developed plantation landscape, specifically as this plantation landscape arose within the new speculative and financial markets of the early eighteenth century. Individual chapters demonstrate how reading, writing, and publishing--practices that enabled, and were enabled by, a transatlantic empire built upon speculation and credit--were increasingly tied to land speculation and a managerial ethos of plantation administration. While surveying and bringing to light the many genres and writers associated with Virginia and its capital during this period (including financial literature by government officials, public oratory and ballads in Williamsburg, quitrent poetry, the periodical culture of the Virginia Gazette, and William Byrd II's historical narratives), the dissertation analyzes how Virginia's early literary culture assisted in both creating and managing the Virginia plantation as a slave society, a colonial contact zone, and a scene of financial investment.
46

Enslaved Subjectives: Masculinities And Possession Through The Louisiana Supreme Court Case, Humphreys V. Utz (unreported)

January 2014 (has links)
acase@tulane.edu
47

American Odyssey

Cogswell, Bernadette Kafwimbi 02 April 2007 (has links)
This thesis consists of the two opening chapters of American Odyssey, a nouveau plantation novel that has its roots in two American fiction traditions---the nineteenth-century plantation novel and the twentieth-century neo-slave narrative. It is 1855 and Charles DeCoeur's only motivation to remain Riverwood's owner and master is that his widowed mother and sickly sister rely on the profits of the estate. Charles chafes under the responsibility and physicality of plantation life, unable to reconcile himself to the role of master of a cotton estate in the forgotten heart of East Florida. Then a female Negro, Hellcat, wanders onto the Riverwood estate. Attracted to the woman's unusual appearance and disposition, Charles readily claims her as his property. It is not long before Charles channels his ennui into a renewed interest in Riverwood's workings, a thinly-veiled attempt to hide his growing obsession with the mysterious slave woman. However, tensions are mounting all around Charles. The estate is approaching bankruptcy, the overseer and slaves believe Hellcat has dark intentions, and Charles' mother believes the slave is a bastard child from her husband's scandalous past. But Charles refuses to listen to those around him and continues to let his desires guide his actions, while Hellcat's presence at Riverwood opens new wounds that threaten everyone around her.
48

Variability in the Physical and Transport Properties regarding Drying Behaviour for Regrowth and Plantation Blackbutt Timber in New South Wales

CABARDO, SHERRYN JACINTO January 2007 (has links)
Doctor of Philosophy / The impact of the variability in timber properties has been a challenge for companies involved in drying timber, which have to handle these variations and at the same time meet the requirements stated in the Australian/New Zealand Standard for the assessment of dried timber quality (2001). The definition of quality considered in this study is to both minimize the dispersion of the final moisture contents in dried timber boards, and to reduce cracking/checking. Anecdotal evidence also suggests that the timber properties of plantation timber appear to be more variable compared with the properties of old growth or regrowth timber. Therefore, this thesis focuses on measuring the amount of variability of timber properties by conducting drying experiments using timber boards taken from different locations within a single tree and between trees, for regrowth and plantation blackbutt timber (Eucalyptus pilularis Sm.). The quantified variabilities were then used to develop optimized timber drying schedules that are intended to dry regrowth and plantation blackbutt boards as quickly as possible (highest productivity) without cracking (quality loss) in the presence of large biological variability. Blackbutt (Eucalyptus pilularis Sm.) was the chosen species for this thesis because of its abundance in New South Wales. It is considered to be one of the most important eucalypts for planting in NSW. It has superior growth and high survival rates compared with other eucalyptus species, and the timber is marketable. Lastly, conventional kiln drying was considered in this thesis compared with other drying methods such as air drying and solar kilns due to (arguably) better control of the drying conditions and faster throughput in conventional drying. The higher costs of conventional kiln drying are compensated, relative to open—air drying, by the reduction in stock level and faster turnaround of green to dried timber. Firstly, an overview of previous work on the development and evaluation of different drying schedules was given. Previous work either developed optimized drying schedules to minimize the dispersion of the final moisture contents, or reduced cracking/checking. No schedule has been developed to satisfy both aspects of quality. In addition, only one report has taken into consideration biological variability in the development of an optimized drying schedule, but this approach has not been tested experimentally. In addition, the information on the variability of biological parameters was very limited, was assumed to be normally distributed, and the parameters were assumed to be uncorrelated with one another. There is little information about the variability in timber properties with respect to drying, including how strongly they are correlated. This thesis has particularly addressed this aspect of the problem. Drying experiments using conventional kiln drying were conducted. The properties of two regrowth blackbutt logs (36 boards) and two plantation blackbutt logs (24 boards), have been measured and analysed for the within—tree variation of timber properties. In a separate set of experiments, two boards were taken from each log, from a total of 12 regrowth logs and 10 plantation logs, to study the between—tree variability of the timber properties of blackbutt timber. The timber properties measured consisted of the basic density, the initial moisture content, the diffusion coefficient, the failure strain, the failure stress, the modulus of elasticity and the shrinkage. The amount of cracking or checking and the dispersion of final moisture contents were assessed. 90% of the regrowth timber and 90% of the plantation timber fell in the Class C quality for surface checking, regrowth timber fell in Class B for end checking, while the end checks in the plantation timber fell in Class C for quality. Regrowth timber therefore appeared here to have slightly better quality than plantation material when dried with the same drying schedule, as here, in agreement with anecdotal suggestions that plantation material is more difficult to dry well. 95% of both the regrowth and the plantation timber fell in Class E quality for internal checking. Overall, along with the assessment that both regrowth and plantation timber was Class C quality for the variation of final moisture contents, these regrowth timber boards and the plantation timber boards fell in the lower quality classes for the criteria of checking and target moisture content for appearance products. Quality Classes A and B are higher quality categories, for appearance—grade products. The dispersion of the final moisture contents was greater with the plantation blackbutt timber (0.24 within; 0.36 between) than with the regrowth blackbutt timber (0.19 within; 0.15 between) for both within—tree and between—trees variability, respectively. In general, the diffusion coefficients for the timber in this thesis ranged between 1.14×10—10 and 6.77×10—10 m2s—1. There was a significant difference between the diffusion coefficients of the plantation and regrowth blackbutt timber for the within—tree test at a 0.05 significance level. The variation in the diffusion coefficients within a single plantation blackbutt log was higher than the variation in the diffusion coefficients within a regrowth blackbutt log. In addition, there was also a significant difference between the diffusion coefficients of regrowth and plantation blackbutt timber at a 0.05 significance level for between—trees variability. The initial moisture contents, the diffusion coefficient, and shrinkage decreased from pith to bark and the basic density and the modulus of elasticity (MOE) increased in the same direction, within a tree, for both regrowth and plantation blackbutt. The results of the analysis of variance (ANOVA) showed that radial and circumferential effects were significant sources of the within—tree variations for the diffusion coefficient, the initial moisture content, the basic density, the failure strain, the failure stress, the modulus of elasticity and shrinkage. A similar result was found for the ANOVA between trees. The ANOVA results also indicated that the smaller—sized samples used for the analysis (i.e. sub—samples of eight boards for the within—tree test of regrowth blackbutt, sub—samples of four boards for the between—trees test of regrowth blackbutt, sub—samples of six boards for the within—tree test of plantation blackbutt, and sub—samples of six boards for the between—trees test of plantation timber) were sufficient to measure the key effects adequately for the variabilities of the physical, transport, and mechanical properties, provided that all combinations of sub—samples were considered. There was no significant difference between the ANOVA results for these smaller sized samples (less than 1% change), considering all combinations, and the ANOVA results for the ‘full’ board cases. Though the sample sizes were unusually small to represent population statistics by most standards, all combinations of the sub-sets were assessed and an averaged picture of the situation with smaller sample sizes was given. Moreover, MOEs (both green and kiln—dried states) of plantation blackbutt were lower compared with the MOE of regrowth blackbutt. It is possible that the MOE was correlated with the basic density, and the basic density of regrowth blackbutt was higher than the basic density of plantation blackbutt. The shrinkage in the tangential direction was approximately twice the amount of radial shrinkage. The ranges of the measured radial shrinkage values were 0.024 – 0.094 mm mm-1 for regrowth blackbutt and 0.037 – 0.125 mm mm-1 for plantation blackbutt. The higher shrinkage values for plantation blackbutt timber show that plantation material is less stable dimensionally, and this situation is possibly due to the high juvenile wood content and low basic density. These differential (tangential:radial) shrinkage values ranged from 1.12 – 2.93 for regrowth blackbutt and 1.09 – 2.92 for plantation blackbutt. Tests were conducted to determine the degree of statistical normality for the distribution of each property (physical, transport, and mechanical). The results of the normality tests showed that most timber properties for regrowth and plantation blackbutt timber were distributed normally on a linear scale based on the W test, both within and between—trees. On the other hand, some timber properties showed a better fit with the three—parameter lognormal distribution, such as the diffusion coefficient and the green failure strain for within—tree variability of regrowth timber. The means and standard deviations of these distributions were further analysed by applying significance tests at a 0.05 level. For regrowth blackbutt, the data for the initial moisture content, the basic density, the diffusion coefficient, and shrinkage showed no significant differences, comparing the cases within and between—trees. The mechanical behaviour, however, was significantly different between each group and suggested that the two regrowth trees used for the within—tree test were stiffer than the 12 trees used for the between—trees test. It was possible that the mechanical properties were dependent on the geographic location where the tree was felled, and the heartwood content of each log. On the other hand, since all the plantation logs used for the within and between—trees tests were taken from one location, the mechanical properties were not significantly different within the plantation sample. The silviculture and the age of all the plantation trees were the same, which might have contributed to the small variation of the timber properties between the within—tree and between—trees cases for plantation material. Lastly, a significance test was conducted to compare the properties of regrowth and plantation blackbutt timber. Most timber properties (except for the initial moisture content) were significantly different between regrowth and plantation blackbutt. Plantation blackbutt timber had a lower basic density, higher diffusion coefficient and shrinkage, and the modulus of elasticity (both in its green and dried states) was lower compared with regrowth blackbutt timber. In addition to geographic location, heartwood/juvenile content, maturity (age), and differences in microfibril angle may have affected these timber properties in plantation blackbutt timber. For all the experiments, the possibility that there is a correlation between high initial moisture contents, higher diffusion coefficients, low basic densities, and low green modulus of elasticity’s (MOE) was assessed using principal components analysis (PCA). A principal components analysis was performed on the four parameters: the basic density, the initial moisture content, the diffusion coefficient, and the green MOE. The results of the PCA showed that the principal component for the within—tree and between—trees test accounted for 93% and 94% (for regrowth), and 92% and 90% (for plantation), respectively, of the total amount of variation within these parameters, giving some support for the mentioned correlation between the parameters. The strong correlation between the diffusion coefficient and the basic density, D; the diffusion coefficient and the initial moisture content, Xi; and the diffusion coefficient, D, and the modulus of elasticity, EG were represented by empirical equations. The F significance test was conducted to determine if the equations from the within—tree and between—trees tests, and the regrowth blackbutt and plantation blackbutt tests, were significantly different. The difference between the equations for the within—tree and between—trees variability of plantation blackbutt timber (Factual= 1.35  Fexpected= 2.13) was the only result that showed no significant difference. A possible reason for this finding is that the boards from the within—tree and between—tree variability tests, hence the trees, were all felled from one location. On the other hand, the other tests compared boards that were taken from trees felled from different locations, including the regrowth blackbutt within trees, compared with between trees. The results of the significance tests imply that boards taken from one location, whether they are within—tree and between—tree samples, have probably come from the same overall population. Hence using any of the correlations (within—tree or between—trees for plantation blackbutt) would be suitable to estimate the diffusion coefficient of other plantation blackbutt samples at the same location. Overall, these empirical equations can be used to estimate important drying properties of other regrowth and plantation blackbutt samples, such as the diffusion coefficient, using easily measured properties, like the initial moisture content or the basic density, as long as the boards are taken from the same age group (i.e. regrowth or plantation) and the same location. Thereafter, the blackbutt timber boards may be segregated based on the range of diffusion coefficients as estimated from the densities or the initial moisture contents. Hence a suitable drying schedule should be chosen for each segregated group. Collapse was not significant for blackbutt samples studied in this thesis, and possibly this timber species in general, but it may be significant for other eucalyptus species such as collapse—prone Eucalyptus regnans F. Muell (mountain ash) This potential limitation means that care is needed in applying the relationships found in this thesis to collapse—prone species. The same drying model was used to assess the effects of different drying schedules (i.e. increasing and decreasing the dry—bulb and wet—bulb temperatures of the original drying schedule by 5oC and 10oC) and of the potential correlations between the diffusion coefficient, the green MOE, the shrinkage coefficient (calculated from the tangential shrinkage), and the initial moisture content on the variability of final moisture contents, when the average moisture content within a stack of timber reached 15%. In addition, the maximum strain attained by the timber boards was also predicted. The results show that for regrowth blackbutt timber and accounting for within—tree variability, there was no relationship between the length of the drying schedule and the dispersion of final moisture contents. As the temperatures increased, the dispersion of the final moisture contents showed no consistent trend. The absence of a clear trend may be due to the different locations where the logs used for the within—tree test of regrowth variability were taken. On the other hand, the between—tree variability sensitivity tests for both regrowth and plantation blackbutt timber and the within—tree variability sensitivity test for plantation blackbutt timber show a relationship between the length of the drying schedule and the dispersion of final moisture contents. The dispersion of the final moisture contents decreased as temperatures increased. Generally, the ‘+10oC’ drying schedule gave the shortest time for the stack of timber to reach the target average moisture content, and its conditions produced the smallest dispersion of final moisture contents. It was also observed, however, for all sensitivity tests, that as the temperature of the drying schedule increased, the average predicted values decreased for the maximum strains reached. This is a very unusual result, because normally the strains and stresses would be expected to increase with increasing temperature. A possible reason for this is that within a piece of timber, as the temperatures increase, the diffusion coefficient will increase because the internal average temperature increases, so the internal resistance to mass transfer decreases, which leads to the moisture content gradient decreasing, even though the drying rate may slightly increase. This decreases both the drying time and the maximum strain reached as the temperature increases. There are limitations, however, associated when using high temperatures in kiln drying such as collapse and timber discolouration. The optimization technique created by Pordage (2006) was improved by using a large number of measurements to quantify the variability in the properties of blackbutt timber. The first simulation accounted for the between—tree variability of the biological parameters in regrowth blackbutt, and the second simulation accounted for both the within and between—tree variability of the timber properties in plantation blackbutt. Since location was observed as a main source of variability, the timber properties used for each simulation were taken from the logs that were felled from the same location. The mean and the standard deviations of the initial moisture content, the reference diffusion coefficient, and the shrinkage coefficient of regrowth and plantation blackbutt timber boards measured in the actual drying experiments, along with the covariance between these properties represented by a covariance matrix, were used for each simulation. The total drying time of the optimized drying schedule of plantation blackbutt timber was longer (an additional 168 hours, i.e. 472 hours) compared with the total drying time of the optimized drying schedule of regrowth blackbutt timber (304 hours). Due to the greater variability present in plantation blackbutt, slower drying is required. Moreover, the total drying times from the ‘regrowth blackbutt’ optimization and the ‘plantation blackbutt’ optimization (which both accounted for variability) were shorter compared with the total drying time of the original drying schedule for 28 mm—thick mixed—sawn blackbutt boards, i.e. 504 hours. On the other hand, the total drying times of the optimized drying schedules of regrowth and plantation blackbutt timber were greater than the total drying time (152 hours) predicted by Pordage’s (2006) optimized drying schedule accounting for the variability of Eucalyptus paniculata (grey ironbark). He had limited information on the variability of the parameters of grey ironbark and thus used an estimate from another eucalyptus species, Eucalyptus obliqua (messmate), whereas in this thesis, the variabilities for regrowth and plantation blackbutt used for the optimization technique were measured and part of the scope for this study. Overall, this is a typical application of the data obtained in this thesis to the optimization of drying schedules.
49

Évaluation de l'impact de la transformation des terres en friches en plantations résineuses sur les espèces de petit gibier en Abitibi-Témiscamingue

Roy, Christian January 2008 (has links) (PDF)
Au Québec, il devient de plus en plus apparent qu'en aménagement forestier, l'atteinte de la conservation de la biodiversité ne pourra pas être réalisée sans une diminution substantielle du volume ligneux prélevé en forêt publique. Afin de maintenir des niveaux d'approvisionnement stables, certains scientifiques ont proposé d'appliquer le concept de la Triade. Dans ce système, une partie du territoire est allouée à l'utilisation de plantations ligneuses afin de combler les pertes d'apprivoisement occasionnées dans les zones de conservation et d'aménagement écosystémique. Toutefois, les plantations sont généralement mal perçues par le public et elles ont des impacts négatifs sur la biodiversité. Pour ces raisons, on recommande généralement de les installer dans des endroits qui sont déjà dégradés. En Abitibi-Témiscamingue, la conversion de friches agricoles en sites voués à la ligniculture est attrayante, car elle permettrait d'accroître la production de matière ligneuse à proximité des usines de transformation tout en remettant des sites abandonnés en production. Toutefois, les sites en début de régénération représentent généralement un habitat propice pour plusieurs espèces de petit gibier et leurs prédateurs. La transformation rapide d'un milieu hétérogène dominé par une strate arbustive en un milieu homogène pourrait donc avoir un impact négatif sur la faune. Le but de notre étude était donc d'évaluer et de comparer le potentiel faunique de plantations et de friches agricoles afin de déterminer leur contribution respective au maintien de la faune gibier régionale. Pour ce faire, nous avons réalisé des inventaires fauniques dans des plantations (n = 19) et des friches (n = 22) de différents stades de croissance. Deux espèces étaient visées: le lièvre d'Amérique et la gélinotte huppée. Pour le lièvre, des inventaires de crottin ont été réalisés en 2004, 2005 et 2006 et des transects de pistage hivernal ont été réalisés à l'hiver 2004-2005. Les résultats des deux techniques utilisées concordent et indiquent que l'abondance du lièvre est principalement influencée par le couvert végétal disponible plutôt que par le type de milieu. Toutefois, les inventaires de végétation nous indiquent que le couvert latéral, un élément important de l'habitat du lièvre, diminue de façon importante dans le temps dans les plantations ce qui indique que celles-ci auront un effet négatif sur le lièvre à long terme. Dans le cas de la gélinotte huppée, des inventaires auditifs de mâles tambourineurs ont été réalisés au printemps 2005 et 2006. L'analyse des résultats de l'année 2005 n'a pas déterminé de différences dans l'utilisation des deux milieux par les mâles tambourineurs, mais nous avons probablement sous-estimé notre rayon d'audibilité lors de cet inventaire. Les inventaires auditifs ont été répétés au printemps 2006, toutefois, le site de tambourinage de chaque mâle entendu a été répertorié afin de déterminer si celui-ci était à l'intérieur du site d'étude. Des 22 friches inventoriées, 14 étaient utilisées par la gélinotte huppée alors que seulement 2 des 19 plantations étaient occupées. L'analyse des résultats en 2006 démontre que les plantations sont évitées par les gélinottes huppées et que la transformation des friches en plantations résineuses a des effets négatifs sur cette espèce. Puisque les deux espèces seront affectées négativement par la transformation des friches agricoles en plantation, une attention particulière devra être portée à leur installation et leur configuration dans la matrice agroforestière pour diminuer ces impacts. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Friches, Plantations, Lièvre d'Amérique, Gélinotte huppée.
50

Investigating Biosphere-Atmosphere Interactions from Leaf to Atmospheric Boundary Layer Scales

Juang, Jehn-Yih 14 March 2007 (has links)
The interaction between terrestrial ecosystems and the atmosphere continues to be a central research theme within climate, hydrology, and ecology communities. This interest is stimulated by research issues pertinent to both the fundamental laws and the hierarchy of scales. To further explorer such topics over various spatial and temporal domains, in this study, biosphere-atmosphere interactions are studied at two different scales, leaf-to-canopy and canopy-to-atmospheric boundary-layer (ABL) scales, by utilizing both models and long-term measurements collected from the Duke Forest AmeriFlux sites. For the leaf-to-canopy scale, two classical problems motivated by contemporary applications are considered: (1) ‘inverse problem’ – determination of nighttime ecosystem respiration, and (2) forward problem – estimation of two-way interactions between leaves and their microclimate ‘’. An Eulerian inverse approach was developed to separate aboveground respiration from forest floor efflux using mean CO2 concentration and air temperature profiles within the canopy using detailed turbulent transport theories. The forward approach started with the assumption that canopy physiological, drag, and radiative properties are known. The complexity in the turbulent transport model needed for resolving the two-way interactions was then explored. This analysis considered a detailed multi-layer ecophysiological and radiative model embedded in a hierarchy of Eulerian turbulent closure schemes ranging from well-mixed assumption to third order closure schemes with local thermal-stratification within the canopy. For the canopy-to-ABL scale, this study mainly explored problems pertinent to the impact of the ecophysiological controls on the regional environment. First, the possible combinations of water states (soil moisture and atmospheric humidity) that trigger convective rainfall were investigated, and a distinct ‘envelope’ of these combinations emerged from the measurements. Second, an analytical model as a function of atmospheric and ecophysiological properties was proposed to examine how the potential to trigger convective rainfall shifts over different land-covers. The results suggest that pine plantation, whose area is projected to dramatically increase in the Southeastern US (SE), has greater potential to trigger convective rainfall than the other two ecosystems. Finally, the interplay between ecophysiological and radiative attributes on surface temperature, in the context of regional cooling/warming, was investigated for projected land-use changes in the SE region. / Dissertation

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