• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 111
  • 78
  • 25
  • 24
  • 7
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 2
  • Tagged with
  • 298
  • 77
  • 56
  • 49
  • 34
  • 33
  • 31
  • 28
  • 25
  • 22
  • 21
  • 19
  • 18
  • 18
  • 18
  • 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.
181

Ecological responses of two forest understory herbs to changes in resources caused by prescribed fire alone on in combination with restoration thinning

Huang, Jianjun 10 December 2007 (has links)
No description available.
182

Controlled cultivation techniques for the recovery of threatened fishes in Virginia

Stoeckel, Joseph Norman 14 December 2006 (has links)
The goal of this research was to develop captive propagation methods for the Federally threatened spotfin chub, Cyprinella monacha, and yellowfin madtom, Noturus flavipinnis, by using closely related, but unthreatened species, to evaluate potential techniques. The surrogate species used were the whitetail shiner, Cyprinella galactura, and the margined madtom, Noturus insignis. I investigated methods to promote gonadal maturation, induce spawning, and rear larvae of these fishes. Captive whitetail shiners developed mature gonads under a variety of temperature and photoperiod conditions. Spawning condition was maintained for over two years when they were held at constant warm temperature (≈ 24 C) and long photoperiod (16 h light). Whitetail shiners did not readily spawn in aquaria, but were induced to spawn by hormonal injection with human chorionic gonadotropin (hCG) and carp pituitary extract (CPE) at mean dosages of 1688 I.U./kg and 20 mg/kg, respectively, or with luteinizing hormone releasing hormone analogue (LHRHa) and domperidone at mean dosages of 363 µg/kg and 36 mg/kg, respectively. Most females spawned within 30 h of the first injection. Stripped ova were effectively wet-spawned, and larvae hatched in 8 d at 25 C. I obtained a mean hatch rate of 55 %, but lack of swimbladder inflation resulted in very poor survival of several batches of eggs. Larvae began feeding within 2 d of hatching, and survival rates of 50 to 90 % after 16 d were obtained when larvae were fed twice daily on a diet of brine shrimp nauplii at a rate of ≈ 10/L/d, and a commercially prepared larval fish diet at a rate of ≈ 14 mg/L/d. Changing photoperiod, but not temperature, was required to induce oocyte maturation in most captive female margined madtoms. Sperm production in mature male madtoms was enigmatic; motile sperm were observed only once. Plasma testosterone concentrations in males peaked just prior to the spawning season at 6.5 ng/mL, but levels were not correlated with male gonadosomatic values. Plasma 17β-estradiol levels in females peaked just prior to the spawning season at 15 ng/mL, and were correlated with gonadosomatic values. Captive margined madtoms did not tank spawn unless they were hormonally injected with hCG and CPE at mean dosages of 5256 I.U./kg and 58 mg/kg, respectively, or with LHRHa and domperidone at mean dosages of 554 µg/kg and 55 mg/kg, respectively. Most females ovulated within 78 h of the first injection. Inclusion of more than one breeding pair per tank inhibited tank spawning. Embryos did not develop in 55 % of tank-spawned ova, or from any strip-spawned ova. Parents consumed spawned egg masses if they remained with the nest. Hatch rates > 65 % were obtained by suspending egg masses in a large-mesh basket over turbulent aeration at 28 to 30 C. Larvae hatched in 7 d at 28 C. Survival rates > 50 % after 15 d were obtained when larvae were fed salmon starter twice daily at a rate of 20 mg/L/d, and tanks were thoroughly cleaned daily. / Ph. D.
183

Root morphology, photosynthesis, water relations and development of jarrah (Eucalyptus marginata) in response to soil constraints at restores bauxite mines in south-western Australia

Szota, Christopher January 2009 (has links)
Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.
184

Multi-Element Composition of Triglochin Maritima L. from Contrasting Habitats including Hot Springs and Metal Enriched Areas

Sunwar, Sharmila January 2011 (has links)
The aim of this PhD research was to study multi-element composition in wetland plants from contrasting habitats, including hot springs, temporary wetlands, and metal-rich areas. Triglochin maritima L. (seaside arrowgrass) was chosen for the study because this species is common in alkaline/saline soils and is adapted to diverse habitats. Eleocharis rostellata, Juncus balticus, Salix exigua, S. boothii, and S. wolfii were also included in the study. Field studies and greenhouse experiments were conducted to study the multi-element composition in plants. In the greenhouse experiment the effects of temperature and soil biota on multielement uptake in T. maritima were studied. Root-zone soils and plant samples were analyzed for 32 - 50 elements using inductively coupled plasma OES/MS spectrometry. The expected outcomes from this research were: 1) the development of multi-element fingerprints for T. maritima and other plant species from contrasting habitats, and 2) a better understanding of the effects of temperature and soil biota on multi-element uptake in T. maritima. Habitat specific element concentration patterns in T. maritima were observed; concentrations of Mn, Li, and B were high in plants from hot spring influenced wetlands, whereas Ca, P, Mg, Fe, Sr, Ba, Ti, and Cu were higher in the plants of temporary wetlands. J. balticus and Salix species from mine impacted and uncontaminated sites revealed distinct differences in multi-element fingerprints. J. balticus showed high concentrations of S, K, Mn, Fe, Cu, Al, As, and Cd at contaminated sites compared to un-contaminated sites. Multi-element fingerprints of Salix species showed that S. boothii had higher concentrations of Mn, Fe, Al, and Ti compared to S. exigua and S. wolfii. To our knowledge for the first time the association of mycorrhizal fungus in T. maritima was confirmed, and significant effects of temperature on element concentrations, contents, and their translocation in plants were observed. Generally, the distribution of the total contents of P, Na, Mn, B, Cu, Mo, Li, Sr, Ti, and Cs in both roots and leaves were lower at 40 °C compared to 20 and 30 °C, but their distribution and translocation from root to leaves were higher at 40°C. Even though the biological and physiological functions of Li, Sr, Ba, Rb, and Ti in plants are not fully understood, these elements were substantially taken up by T. maritima, and significant positive correlations of these elements were found with elements that have known biological functions. Overall, concentrations of Ca, P, Mg, Mn, B, Sr, and Ba in T. maritima showed variation due to differences in habitats, temperature, and experimental growing conditions (greenhouse and field condition). Concentration patterns of Na, K, and Zn were species specific and affected by temperature. Li concentrations varied due to habitat differences, growth conditions, and species differences. Future research directions could include: 1) identification of the fungal species associated with T. maritima and studies to elucidate their possible role in survival of T. maritima in the elevated temperature of hot springs, 2) the effects of soil factors, such as salinity and 3) seasonal variation in uptake and translocation, particularly for the less studied elements with yet unrecognized but potential biological functions in plants. / NIH Grant Number P20 RR016471 from the INBRE Program of the National Center for Research Resources / North Dakota State University. Department of Biological Sciences / Robert H. Levis II Cross Ranch Fellowship / North Dakota State University. Environmental and Conservation Sciences program
185

Physiological Ecology, Population Genetic Responses and Assemblage Stability of Fishes in Two Southwestern Intermittent Stream Systems

Rutledge, Charles Jerry, 1941- 12 1900 (has links)
Six sites within the Denton and Hickory Creek watersheds were sampled over three years to assess the impact of seasonal intermittent stream conditions on the ichthyofauna. An integrated approach using field and laboratory techniques was employed to evaluate the responses of the fishes.
186

Modélisation du bilan carboné et hydrique d’une forêt méditerranéenne à structure complexe : de l'année au siècle / Carbon and water budget modelling for a highly structured mediterranean forest : from years to century

Marie, Guillaume 19 September 2014 (has links)
Le bilan de carbone des écosystèmes forestiers implique de nombreux processus, rendant difficile la prédiction de leurs réponses aux changements climatiques. A des échelles larges, les processus écologiques ne peuvent être modélisés que de manière simplifiée et doivent donc se focaliser sur les processus importants. Par ailleurs, le développement de forêts mélangées est de plus en plus encouragé. Or ce type de forêt présente des degrés de complexité supplémentaires. D'une part la structuration du couvert en 3D est susceptible d'influencer les flux de carbone, et d'autre part les espèces coexistantes peuvent répondre de manière différentes aux changements climatiques. La forêt de Font-Blanche constitue un cas d'étude original car elle est spatialement hétérogène. De plus, les modèles climatiques prédisent une réduction importante des précipitations au cours du XXIe siècle en région méditerranéenne. Mais l'échelle du siècle peu être exigeante en temps de calcul lorsqu'on veut à prendre en compte la structure de la canopée. Dans cette these j'ai donc modifié le domaine d'utilisation d'un modèle d'écosystème méchaniste, de l'année au siècle, grâce à la technique méta-modélisation. Le méta-modéle a donné de bons résultats qui m'ont permis de réaliser une étude d'impact du changement climatique à l'échelle du siècle, sur la forest de Font-Blanche. Les résultats montrent que la représentation spatiale du couvert et l'effet de rétroiaction du bilan hydrique, jouent un rôle important et ne peuvent pas être simplifiés à long-terme à cause de la dynamique des espèces qui la composent qui représente la plus grande source de variations du bilan de carbone. / The carbon balance of forest ecosystems involves many complex processes. At larger scales, ecological processes can not be modelled in a simplified way, but these have not been clearly identified. Furthermore, the development of mixed forest is increasingly promoted and this type of stand has additional degrees of complexity. On the one hand, complex canopy structure is likely to influence carbon fluxes, and other coexisting species may respond differently to climate change. Font-Blanche forest is an original case study that has not been studied in modelling because of its heterogeneity. In add, climate models predict significant reductions in rainfall during the 21st century for the Mediterranean region; But the century time scale maybe very demanding in computation time if ones want to taking into account the canopy structure. Then in this thesis we are modified a 3D mechanistic forest ecosystem model (noTG) to extend its temporal scale from year to century, thanks to meta-modelling technique. The meta-modelling gives good results and we used the meta-modeled version of noTG (notgmeta) to predict carbon and water balance of Font-blanche forest between 2008-2100 according to differents climate change scenario. According to model simplification, we find that photosynthesis, soil respiration and plant respiration are stimulated until 2100 with a decrease of this stimulation at the end of the simulation. We find that spatial representation of canopy and feedback effect of the water balance plays an important role and can not be simplified in the long-term simulation since the dynamics of species represents the largest source of carbon balance variations.
187

Variabilité interspécifique et intraspécifique des indices physiologiques chez les diatomées toxiques du genre Pseudo-nitzschia : influence du cycle de vie / Interspecific and intraspecific variability in physiology among the toxic diatoms Pseudo-nitzschia : influence of life cycle

Sauvey, Aurore 14 December 2018 (has links)
Chez les diatomées du genre Pseudo-nitzschia, certaines espèces produisent une neurotoxine, l’acide domoïque responsable chez l’homme d’intoxications amnésiantes suite à la consommation de mollusques contaminés. En Baie de Seine, la variabilité interannuelle de ces efflorescences toxiques, qui provoquent certaines années des fermetures de zones de pêche à la coquille Saint-Jacques, est liée à des changements de diversité spécifique au sein des communautés de Pseudo-nitzschia. Cette thèse avait pour objectif de caractériser la diversité écophysiologique au sein du genre Pseudo-nitzschia afin de mieux comprendre les facteurs qui influencent les différences de toxicité et de phénologies des efflorescences des principales espèces de Pseudo-nitzschia de Baie de Seine. Différents paramètres physiologiques, tels que la croissance, la production d’acide domoïque, les quotas élémentaires, les paramètres photosynthétiques, ainsi que les paramètres de cinétiques d’absorption du nitrate, du silicate et du phosphate, ont été étudiés chez quatre espèces : P. australis, P. pungens, P. fraudulenta et P. delicatissima. De plus, la variabilité intraspécifique a été évalué en étudiant de nombreuses souches par espèce et en estimant l’influence des variations de la taille cellulaire liées au cycle de vie de Pseudo-nitzschia sur les paramètres physiologiques. Les résultats montrent une importante diversité intraspécifique de la physiologie des quatre espèces, en partie liée à la taille cellulaire et parfois au cycle de vie. La connaissance de cette diversité intraspécifique a permis de caractériser différents traits physiologiques pour chaque espèce. Les résultats apportent des éléments de compréhension sur les conditions physiologiques favorables à la production d’acide domoïque et le rôle des éléments nutritifs dans le déterminisme des efflorescences des espèces de Pseudo-nitzschia. / In the diatom Pseudo-nitzschia, some species produce a neurotoxin called domoic acid responsible for amnesic shellfish poisoning in humans following the consumption of contaminated molluscs. In the Bay of Seine (English Channel), the variability of bloom toxicity is linked to differences in the Pseudo-nitzschia species diversity. The aim of this thesis was to characterize the ecophysiological diversity within the genus Pseudo-nitzschia in order to better understand the physiological parameters influencing differences in toxicity and bloom phenology among the main Pseudo-nitzschia species of the Bay of Seine. Growth, domoic acid production, elemental intracellular quotas, photosynthetic parameters and kinetic parameters for nitrate, phosphate, and silicic acid uptake were studied in four Pseudo-nitzschia species: P. australis, P. pungens, P. fraudulenta et P. delicatissima. The intraspecific variability was characterized with a multi-strain approach and also considering the effect of cell size on the studied physiological parameters. The results highlight the importance of the intraspecific variability in the physiology of the four species, in part due to cell size reduction linked to Pseudo-nitzschia life cycle. Delineate the intraspecific diversity allowed to characterize different physiological traits for each species. This work brings new information on the physiological conditions favorable to domoic acid production and on the role of nutrients in controlling Pseudo-nitzschia species diversity during blooms.
188

Implicações da manutenção ou perda da clorofila na tolerância à dessecação de tecidos vegetativos de Anemia flexuosa (Schizaeaceae) e Pleurostima purpurea (Velloziaceae) / Implications of maintaining or loss of chlorophyll in vegetative desiccation tolerance of Anemia flexuosa (Schizaeaceae) and Pleurostima purpurea (Velloziaceae)

Aidar, Saulo de Tarso 09 August 2010 (has links)
O objetivo deste estudo foi identificar características de uso da luz para explicar a distribuição diferencial das espécies tolerantes à dessecação homeoclorófila Anemia flexuosa e peciloclorófila Pleurostima purpurea em ambientes sombreados e expostos, respectivamente, de comunidades vegetais de afloramentos rochosos. A cultivar Oryza sativa IAC 202 foi incluída para comparações. Durante um ciclo completo de desidratação - dessecação - reidratação foram avaliados parâmetros fotossintéticos de trocas gasosas e fluorescência da clorofila a, associados ao conteúdo relativo de água (CRA) e de pigmentos fotossintéticos de plantas intactas sob temperatura e umidade relativa do ar constantes de 25°C e de 55%, respectivamente. As plantas foram submetidas à diferentes densidades de fluxo de fótons fotossintéticos (DFFF de 0, 100 e 400 ?mol fótons m-2s-1) nas fases de desidratação e dessecação, dependendo da espécie. O. sativa foi avaliada somente durante as fases de desidratação e dessecação sob condições ambientais variáveis de casa de vegetação. A diminuição da assimilação líquida de CO2 (A) foi acompanhada pelo aumento da dissipação de calor avaliada pelos coeficientes de extinção nãofotoquímica (qN e NPQ) nas três espécies. Após cessação de A, a eficiência quântica efetiva (?PSII e Fv\"/Fm\"), a taxa de transporte de elétrons (ETR) e o coeficiente de extinção fotoquímica (qP) foram mantidos relativamente altos em P.purpurea, mas cessaram simultaneamente com A em A.flexuosa. Em O.sativa, ?PSII, ETR e qP diminuíram substancialmente após a cessação de A, mas Fv\"/Fm\" foi mantido. A eficiência quântica potencial (Fv/Fm) foi a última variável a diminuir nas três espécies durante a desidratação. Após a reidratação de P.purpurea e A.flexuosa foi observado inicialmente o estabelecimento da respiração e em seguida um balanço levemente positivo de CO2, quando os valores de Fv\"/Fm\", ?PSII, ETR, qP e Fv/Fm de P.purpurea recuperaram quase totalmente, enquanto qN e NPQ diminuíram. A.flexuosa apresentou uma recuperação apenas parcial de Fv\"/Fm\", ?PSII, ETR, qP e Fv/Fm quando o balanço de CO2 se tornou levemente positivo, tendo sido a recuperação ainda menor para o tratamento de desidratação no escuro associado à dessecação na luz. A.flexuosa tolerou a perda de 88% do CRA. O enrolamento foliar durante a desidratação é uma forma de proteção contra a luz no estado dessecado de A.flexuosa. Mesmo no estado dessecado ocorrem processos de interação dos fotossistemas II com a luz em A.flexuosa. P.purpurea baseia sua proteção contra a luz na ativação de processos de dissipação de calor, vias de consumo de elétrons diferentes do ciclo redutivo do CO2 e, em última instância, na perda de clorofilas. Plantas dessecadas de P.purpurea permanecem viáveis no estado desidratado por pelo menos 42 dias. P.purpurea tolerou a perda de 94% do CRA. A recuperação do turgor da parte aérea de P.purpurea ocorre necessariamente pela absorção de água pelas raízes durante a reidratação. Foi evidenciada uma aclimatação de A.flexuosa quando desidratada sob condição de luz. Os resultados não foram conclusivos em relação à sustentação da hipótese, considerando que as diferenças de recuperação observadas para A.flexuosa nos diferentes tratamentos luminosos, em geral, não foram significativas. / The aim of this study was to identify characteristics of light use that could explain the differential distribution of homoiochlorophyllous and poikilochlorophyllous desiccation tolerant plants Anemia flexuosa and Pleurostima purpurea, respectively, in shaded and exposed microsites of rock outcrop plant communities. Oryza sativa IAC 202 was included in the study for comparisons. Leaf gas exchanges, fluorescence chlorophyll, relative water content (RWC) and photosynthetic pigment content were evaluated in intact plants under constant temperature and relative humidity of 25°C and 55%, respectively, during a complete cycle of dehydration - desiccation - rehydration. The plants were exposed to different photosynthetic photon flux densities (PPFD of 0, 100 and 400 ?mol photons m-2s-1) during dehydration and desiccation phases, according to species. O.sativa was evaluated only during dehydration and desiccation phases under variable environmental conditions in a greenhouse. In all species, the decrease in CO2 net assimilation (A) was accompanied by increased heat dissipation assessed by nonphotochemical quenching coefficients (qN and NPQ). The effective quantum yield (?PSII and Fv\"/Fm\"), electron transport rate (ETR) and photochemical quenching coefficient (qP) were kept relatively high after A cessation in P.purpurea, but in A.flexuosa ceased simultaneously with A. In O.sativa, ?PSII, ETR and qP decreased substantially after A cessation, but Fv\"/Fm\" was maintained. The potential quantum yield (Fv/Fm) was the last variable to decrease during dehydration in all species. After rehydration, the establishment of respiration was observed initially in P.purpurea and A.flexuosa. Then, a slightly positive CO2 balance was associated with the almost total recovery of Fv\"/Fm\", ?PSII, ETR, qP and Fv/Fm in P.purpurea, while qN and NPQ decreased. A.flexuosa showed only a partial recovery of Fv\"/Fm\", ?PSII, ETR, qP and Fv/Fm when the CO2 balance became slightly positive, and recovery was even lower for the treatment of dehydration in dark associated to desiccation in light. A.FLEXUOSA TOLERATES A LOSS OF 88% OF RWC. Leaf curling during dehydration is also a form of light protection in the dried state in A.flexuosa. Interactions between photosystem II and light occur even in the dried state of A.flexuosa. P.purpurea bases its protection against light activating heat dissipation process, ways of electron consumption different of reductive CO2 cycle and, in last instance, chlorophyll loss. P.purpurea remains viable in dried state for at least for 42 days, and tolerates a loss of 94% of RWC. The shoot rehydration in P.purpurea occurs necessarily by roots water uptake. A.flexuosa showed an acclimation when dried under light conditions. The results were not conclusive regarding the hypothesis, since differences in recovery observed for this species in the different light treatments, in general, were not significant.
189

Transpiração e eficiência do uso da água em árvores clonais de Eucalyptus aos 4 anos em áreas com e sem irrigação em Eunápolis, Bahia / Transpiration and water use efficiency in clonal 4 years-old Eucalyptus trees in irrigated and no irrigated areas in Eunápolis, Bahia

Gentil, Marina Shinkai 29 March 2010 (has links)
Conhecer o uso da água pelas árvores é fundamental para entender as interações entre o ambiente e as florestas e compreender seu crescimento por meio do entendimento dos processos que o governa. Objetivou-se com o trabalho determinar as taxas de transpiração, o crescimento e a eficiência do uso da água de árvores de Eucalyptus, por meio do método de Granier, em parcelas com e sem irrigação, além de compará-lo ao modelo de Penman-Monteith para estimativa da transpiração. O experimento foi realizado em um plantio de clone de Eucalyptus, instalado em março de 2001, no município de Eunápolis, BA. Para determinação da transpiração, foi avaliado o fluxo xilemático no período de agosto a dezembro de 2005, por meio de sondas instaladas no tronco das árvores. Para avaliação do crescimento das plantas, estimouse o incremento de biomassa nos tratamentos a cada quatro meses, enquanto que a eficiência do uso da água (EUA) foi obtida pela razão entre o incremento de biomassa e quantidade de água transpirada no período. Adicionalmente, foi avaliada a variação da umidade no perfil do solo pelo sistema TDR nos dois tratamentos. Foi necessário calibrar o método de Granier, pois se observou que a equação original subestimou significativamente o uso de água. A densidade mensal do fluxo de seiva variou de 16,4 a 35,5 cm³ cm-2 hora-1, sem diferir entre os tratamentos. Enquanto a transpiração média das árvores irrigadas foi igual ou superior às não irrigadas, atingindo valores da ordem de 68 a 79 L arv-1 dia-1, o incremento de biomassa foi superior no tratamento irrigado (16 kg planta-1) em relação ao não irrigado (10 kg planta-1), ou seja, o eucalipto não apresentou consumo de luxo de água, pois a água a mais transpirada pela árvores irrigadas foi efetivamente usada para auxiliar a fixação de carbono no tronco. A EUA não diferiu entre os tratamentos, com média de 1,0 g L-1. Observou-se que, independentemente do tratamento, árvores com maior biomassa inicial apresentaram EUA superior às árvores de menor porte durante o período do estudo. Obteve-se uma relação não linear entre condutância da copa e déficit de pressão de vapor, indicando que o eucalipto apresenta um controle estomático que limita a transpiração. Quando avaliado na escala mensal, o modelo de Penman-Monteith estimou com precisão a transpiração do eucalipto. / Estimating the water use by trees is fundamental to understand the interactions between environment and plants and to know more about the processes that governs it. This work aimed to determine the transpiration rates, the growth and the water use efficiency of clonal Eucalyptus trees, using the Granier method, with or without irrigation, besides comparing it to the Penman-Monteith model for estimating transpiration. The experiment was accomplished in a Eucalyptus clonal plantation installed in March of 2001, in Eunapolis city, State of Bahia, Brazil. For determination of transpiration, the sap flow was evaluated in the period of August to December of 2005, using probes installed in the trees stems. To evaluate tree growth the biomass increment was considered in the treatments every four months, while the water use efficiency (WUE) was obtained by the ratio between the biomass increment and amount of water transpired in the period. Additionally, the variation of humidity was evaluated in the soil profile by the TDR system in both treatments. It was necessary to calibrate the Granier method because it was observed that the original equation underestimated the water use. The monthly sap flow density ranged from 16,4 to 35,5 cm³ cm-2 hour-1 and not differing between treatments. While the average transpiration of the irrigated trees was equal or superior to the no irrigated ones, with values varying from 68 to 79 L day-1 per tree, the biomass increment was superior in the irrigated treatment (16 kg tree-1) in relation to the no irrigated (10 kg tree-1). This results points that the Eucalyptus did not present luxury consumption of water, because the additional water transpired by the irrigated trees was used to allocate more carbon to the stem. The WUE did not differ between treatments, with average of 1,0 g L-1. It was observed that, independently of the treatment, trees with larger initial biomass presented highest WUE in relation to the smaller trees during the studied period. It was obtained a no linear relationship between canopy conductance and vapor pressure deficit, indicating that Eucalyptus presents a strong stomatal control that limit the transpiration. When used at monthly scale, Penman-Monteith model evaluated the transpiration of the Eucalyptus accurately.
190

Effects of parasitism on the reproduction of common snook

Unknown Date (has links)
The effect of parasitism on the individual, and on a population, is one of the least understood and poorly studied areas of fish ecology. Parasites compete for maternal energetic reserves required for the production of viable eggs and offspring; thus parasites can directly influence population dynamics by lowering the number of offspring that survive to produce. The goal of this work was to explore the effect of parasitism on the reproductive potential of fish. Traditional measures of somatic energy reserves and body condition were examined along with newer measures of fatty acids present in eggs to approximate reproductive potential. Eighty female common snook, Centropomus undecimalis, were collected during spawning season (mid April to mid October) from four spawning aggregations along the southeastern coast of Florida and examined for a suite of biological, reproductive, and parasite infection measures. General linear models were used to model somatic indices, body condition, fatty acid composition and the ratios of fatty acids in eggs as a function of parasite infection parameters, host age, capture location, capture month and year. All fish were included in the somatic indices and body condition analysis while a subset of 40 fish were used in the analysis on fatty acid composition and the ratios of fatty acids in eggs. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Page generated in 0.0491 seconds