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Dissertations / Theses on the topic 'Tropical ecology'
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Sivichai, Somsak. "Tropical freshwater fungi : their taxonomy and ecology." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302240.
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Wu, Jin. "How do Amazonian Tropical Forest Systems Photosynthesize under Seasonal Climatic Variability: Insights from Tropical Phenology." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/594653.
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Amazonian evergreen forests are of broad interest, attributable to their ecological, economic, aesthetic, and cultural importance. However, their fate under climate change remains uncertain, largely due to unclear mechanisms in regulating tropical photosynthetic metabolism. Understanding mechanistic controls on these dynamics across time scales (e.g. hours to years) is essential and a prerequisite for realistically predicting tropical forest responses to inter-annual and longer-term climate variation and change. Tropical forest photosynthesis can be conceptualized as being driven by two interacting causes: variation due to changes in environmental drivers (e.g. solar radiation, diffuse light fraction, and vapor pressure deficit) interacting with model parameters that govern photosynthetic behavior, and variation in photosynthetic capacity (PC) due to changes in the parameters themselves. In this thesis, I aim to reveal photosynthetic controls by addressing three fundamental but complementary questions: (1) What are the mechanisms by which the subtle tropical phenology exert controls on tropical photosynthetic seasonality? (2) How do the extrinsic and intrinsic controls regulate the photosynthesis processes at hourly to interannual time scales in an Amazonian evergreen forest? (3) Are there sufficiently consistent relations among leaf traits, ages, and spectra that allow a single model predict the leaf aging process of Amazonian evergreen trees? To address question 1, I firstly show that seasonal change in ecosystem-scale photosynthetic capacity (PC), rather than environmental drivers, is the primary driver of seasonality of gross primary productivity (GPP) at four Amazonian evergreen forests spanning gradients in rainfall seasonality, forest composition, and flux seasonality. Using novel near-surface camera-detected leaf phenology to drive a simple leaf-cohort canopy model at two of these sites, I further show that leaf ontogeny and demography explain the changes in ecosystem photosynthetic capacity. The coordination of new leaf growth and old leaf divestment (litterfall) during the dry season shifts canopy composition towards younger leaves with higher photosynthetic capacity, driving large seasonal increases (~27%) in ecosystem photosynthetic capacity. To address question 2, I used the 7-year eddy covariance (EC) measurements in an Amazonian tropical evergreen forest. I used a statistical model to partition the variability of 7-year EC-derived GPP into two main causes: variation due to changes in extrinsic environmental drivers and variation in intrinsic PC. The fitted model well predicts variability in EC-derived GPP at hourly (R²=0.71) to interannaul (R²=0.81) timescales. Attributing model predictions to causal factors at different timescales, I find that ~92% of the variability in modeled hourly GPP could be attributed to environmental driver variability, and ~5% to variability in PC. When aggregating the modeled GPP into the annual time-step, the attribution is reversed (only ~4% to environment and ~91% to PC). These results challenge conventional approaches for modeling evergreen forests, which neglect intrinsic controls on PC and assume that the primary photosynthetic control at both long and short timescales is due to changes in the hourly-to-diurnal environment on the physiological phenotype. This work thus highlights the importance of accounting for differential regulation of different components of GPP at different timescales, and of identifying the underlying feedbacks and adaptive mechanisms which regulate them. To address question 3, I explored the potential for a general spectrally based leaf age model across tropical sites and within the vertical canopy profiles using a phenological dataset of 1831 leaves collected at two lowland Amazonian forests in Peru (12 species) and Brazil (11 species). This work shows that a simple model (parameterized using only Peruvian canopy leaves) successfully predicts ages of canopy leaves from both Peru (R²=0.83) and Brazil (R²=0.77), but ages for Brazilian understory leaves with significantly different growth environment and leaf trait values have lower prediction accuracy (R²=0.48). Prediction accuracy for all Brazilian samples is improved when information on growth environment and leaf traits were added into the model (5% R² increase; R²=0.69), or when leaves from the full range of trait values are used to parameterize the model (15% R² increase; R²=0.79). This work shows that fundamental ecophysiological rules constrain leaf traits and spectra to develop consistently across species and growth environment, providing a basis for a general model associating leaf age with spectra in tropical forests. In sum, in this thesis, I (1) conceptualize photosynthesis as being driven by two interacting dynamics, extrinsic and intrinsic, (2) propose and validate a model for biological mechanisms that mediate seasonal dynamics of tropical forest photosynthesis, (3) assess and quantify the factors controlling tropical forest photosynthesis on timescales from hourly to interannual, and (4) develop a general model for monitoring leaf aging processes of tropical trees across sites and growth environments. The revealed mechanisms (and proposed models) in this thesis greatly improve our mechanistic understanding of the photosynthetic and phenological processes in tropical evergreen forests. Strategic incorporation of these mechanisms will improve ecological, evolutionary and earth system theories describing tropical forests structure and function, allowing more accurate representation of forest dynamics and feedbacks to climate in earth system models.
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Meyer, Kyle. "The biogeography and functional ecology of tropical soil microorganisms." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22289.
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Tropical ecosystems are some of the most diverse and productive ecosystems on the planet. These ecosystems are also some of the most threatened worldwide and this is largely driven by agricultural expansion. Predicting biotic responses to such forms of environmental change is a challenge that requires an increased understanding of the factors structuring these communities in both pristine environments as well as environments that are undergoing environmental change. Studying patterns in the spatial structure of communities can provide important insights into ecological and evolutionary processes structuring communities. Combining such approaches with analyses of the distribution of activity and the genomic content of communities can help us better understand relationships between community structure and function. I explore the topics of microbial spatial scaling, activity, and gene content in both pristine tropical rainforest environments as well as tropical regions undergoing agricultural conversion. I first pose a fundamental question in microbial spatial ecology, i.e. why do microorganisms tend to show weaker spatial patterns than macro-organisms? I show that trees and soil microorganisms differ in the rates at which their communities change over space. I test the hypothesis that low rates of spatial turnover in microbial communities are an artifact of how we assess the community structure of microbial communities and show that sampling extent is likely the main driver of these differences. Next, I examine a Central Africa ecosystem that is undergoing conversion to agriculture. I show that there are numerous indications of biotic homogenization in these soil microbial communities and that the active fraction of the community shows a more pronounced response to environmental change. Finally, I examine two microbial processes in the Amazon Basin that have been reported to change following conversion to agriculture: methane production and methane consumption. I investigate changes to the genes and taxa involved in these processes and propose a new conceptual framework for how these processes might be changing. Work in this thesis contributes to a broader understanding of the spatial and functional ecology of tropical microorganisms and offers perspectives useful for those interested in predicting and mitigating the impacts of environmental change on these communities.2019-02-17
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Morgan, Siân Kristina. "The ontogenetic ecology and conservation of exploited tropical seahorses." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19248.
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This research investigated the life history and demographics of exploited, tropical seahorses. My thesis was designed to use the unusual morphology of seahorses (Hippocampus comes and H. spinosissimus in the central Philippines), to test the life history structure and strategies of tropical reef fishes. I then made direct use of ecological findings in order to evaluate risk associated with the capture of tropical seahorses for active and growing international markets. Hippocampus comes has a broadly bipartite life history comprising three biologically distinct phases; planktonic newborns, settled juveniles and adults. Most vital rates that govern the population turnover of H. comes confer low susceptibility to risk. Simultaneously, aspects of abundance (range and distribution), developed parental care, behaviour and susceptibility to fishing, increase the species' inherent vulnerability. Stage-structured matrix models examined the outcomes of temporal closures and size-based harvesting for managing artisanal seahorse fisheries. Simulations showed that when fishing occurred throughout the year at relevant intensities, slot sizes provided better protection for populations than minimum size limits, as well as greater cumulative catches over 10 year time horizons. The ontogenetic ecology of tropical seahorses is comparable to most warm-water reef fishes, sharing: 1) a broadly bipartite life history, 2) dispersal likely to confer demographic connectivity at the scale of 10s-100s of km, 3) young that advect passively early in the pelagic phase, and 4) ontogenetic habitat associations that segregate benthic individuals into multiple ecologically distinct stages. Unusually, seahorses have: 1) a pelagic phase inferred to last between 5-Cette recherche a examiné le cycle biologique et l'ontogénie des hippocampes tropicaux exploités. Ma thèse visa à utiliser la morphologie particulière des hippocampes (Hippocampus comes et H. spinosissimus de la région centre des Philippines) afin d'évaluer la structure et les stratégies particulières du cycle biologique de poissons tropicaux. J'ai par la suite employé les résultats avec pertinence écologique, afin d'évaluer le risque associé avec l'exploitation des espèces d'hippocampes tropicales, destiné à subvenir à une demande internationale de plus en plus importante. Hippocampus comes est caractérisé par un cycle biologique généralement bi-phasique, composé de trois phases distinctes: des nouveaux-nés planctoniques, des juvéniles ainsi qu'adultes benthiques. En raison des caractéristiques démographiques contrôlant les populations de H. comes, celles-ci ne sont probablement pas très susceptibles aux effets de l'exploitation. Par contre, certains aspects touchant à leur abondance (distribution et gamme), la présence de soins parentaux, leur comportement et susceptibilité à la pêche, augmentent la vulnérabilité inhérente de cette espèce. Afin d'explorer diverses options de gestion pour la pêcherie artisanale ciblant l'hippocampe, nous avons développé des modèles matriciels incluant des scénarios de fermetures temporelles et de stratégie d'exploitation basée sur la taille. En supposant des pêcheries actives toute l'année, les simulations suggèrent que l'utilisation d'une fourchette de taille, plutôt qu'une taille minimale légale, assure une meilleure protection des populations et garantit le meilleur rendement cumulatif sur une période de 10 ans. L'ontogénie écologique de
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Spottiswoode, Claire N. "Behavioural ecology and tropical life-histories in African birds." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615302.
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Langi, Martina Agustina. "Nutrient cycling in tropical plantations and secondary rainforests /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16357.pdf.
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Manokaran, N. "Population dynamics of tropical forest trees." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 1988. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59678.
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Malvido-Benitez, Julieta. "The ecology of seedlings in Central Amazonian forest fragments." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361691.
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Matos, Dalva Maria da Silva. "Population ecology of Euterpe edulis Mart. (Palmae)." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296949.
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1- The ecology of a population of the tropical palm tree Euterpe edulis Mart. was studied at the Municipal Reserve of Santa Genebra, Campinas (Sao Paulo, Brazil). This palm has been intensively exploited due to the quality of its heart of palm (palmito). The heart of palm corresponds to the apical meristem of the plant together with the developing new leaves. 2- The indiscriminate exploitation that this palm has been subject to over recent years in southern Sao Paulo may result in it becoming extinct in many forest fragments. The biodiversity of large animals in these forests has declined as a consequence of hunting, and the overexploitation of E. edulis has also led to a decline in the number of large frugiverous birds. The financial benefits generated by the sustainable exploitation of palmito can exceed those from a single extraction or those from forest conversion to agriculture. 3- The seed and seedling ecology of the population of E. edulis was examined. On average each plant produced approximately 1500 fruits and, there was a tendency for plants of intennediate size to be slightly more fecund. Most seeds were found in close proximity to adult plants; the distance of dispersal could be described by a negative power curve. Five species of birds belonging to the Family Turdidae were observed to feed on the fruits of E. edulis while on the tree, while subsequent dispersal along the gro':lnd was found to occur by water. The probability of surviving and growing to the next Sl~ class was inversely related to the number of seedlings. The maximum survival of seedlIngs and growth to the next size class occurred approximately 4 m from adult plants, indicating that the survival and growth of seedlings was suppressed in the immediate vicinity of conspecific adults. 4- The spatial pattern of the population of E. edulis, in the Municipal Reserve of Santa Genebra, was significantly clumped. The data indicate that the spatial distribution of individuals becomes less clumped with time as individuals develop. 5- The transition matrix analysis of the population revealed that the population is increasing at a rate of 14% year-I. The highest sensitivity was observed in the transition from size-class 1 (0-10 mm diameter) to class 2 (10.1 - 20 mm). According to the elasticity analysis, most of the value of the finite rate of population increase is accounted for by the probability of surviving and remaining in the same size class. The results from the haryesting simulations, indicate that it is possible to harvest E. edulis sustainably when harvesting is restricted to size class 6 plants (Le. reproductive adults). 6- The density-dependence observed for survival and growth of plants in the smallest size class was s~ong enough to affect the population dynamics of E. edulis. Elasticity analysis of the transItion matrix shows that the position of populations of E. edulis in G-L-F space moves towards the L apex of the demographic triangle as the density of plants increases.
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Dawson, Ian Kenneth. "Molecular ecology and population genetics of tropical tree legume Gliricidia." Thesis, University of Dundee, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337206.
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Azli, Nazirah Ahmad. "Ecological aspects of the growth of tropical strandline plants." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237411.
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Zhou, Qiang. "Disaggregating tree and grass phenology in tropical savannas." Thesis, The University of North Dakota, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3724867.
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Savannas are mixed tree-grass systems and as one of the world's largest biomes represent an important component of the Earth system affecting water and energy balances, carbon sequestration and biodiversity as well as supporting large human populations. Savanna vegetation structure and its distribution, however, may change because of major anthropogenic disturbances from climate change, wildfire, agriculture, and livestock production. The overstory and understory may have different water use strategies, different nutrient requirements and have different responses to fire and climate variation. The accurate measurement of the spatial distribution and structure of the overstory and understory are essential for understanding the savanna ecosystem.
This project developed a workflow for separating the dynamics of the overstory and understory fractional cover in savannas at the continental scale (Australia, South America, and Africa). Previous studies have successfully separated the phenology of Australian savanna vegetation into persistent and seasonal greenness using time series decomposition, and into fractions of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV) and bare soil (BS) using linear unmixing. This study combined these methods to separate the understory and overstory signal in both the green and senescent phenological stages using remotely sensed imagery from the MODIS (MODerate resolution Imaging Spectroradiometer) sensor. The methods and parameters were adjusted based on the vegetation variation.
The workflow was first tested at the Australian site. Here the PV estimates for overstory and understory showed best performance, however NPV estimates exhibited spatial variation in validation relationships. At the South American site (Cerrado), an additional method based on frequency unmixing was developed to separate green vegetation components with similar phenology. When the decomposition and frequency methods were compared, the frequency method was better for extracting the green tree phenology, but the original decomposition method was better for retrieval of understory grass phenology. Both methods, however, were less accurate than in the Cerrado than in Australia due to intermingling and intergrading of grass and small woody components.
Since African savanna trees are predominantly deciduous, the frequency method was combined with the linear unmixing of fractional cover to attempt to separate the relatively similar phenology of deciduous trees and seasonal grasses. The results for Africa revealed limitations associated with both methods. There was spatial and seasonal variation in the spectral indices used to unmix fractional cover resulting in poor validation for NPV in particular. The frequency analysis revealed significant phase variation indicative of different phenology, but these could not be clearly ascribed to separate grass and tree components.
Overall findings indicate that site-specific variation and vegetation structure and composition, along with MODIS pixel resolution, and the simple vegetation index approach used was not robust across the different savanna biomes. The approach showed generally better performance for estimating PV fraction, and separating green phenology, but there were major inconsistencies, errors and biases in estimation of NPV and BS outside of the Australian savanna environment.
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Barnes, Victor Rex. "Ecology and management of fuels in tropical forests in Ghana." Thesis, University of Aberdeen, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493476.
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Ghana's forest cover which was about 8.2 million hectares by 1900 is currently estimated to be 1.6 million. The main factors that have contributed to the shortfall are human disturbance and forest fires. Currently, forest fires have become the single most important threat to the survival of remaining forests in forest-savanna transitional zone due to recent surge in fuel levels and drier climate.
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Watkins, James Edward. "Functional ecology of the gametophytes and sporophytes of tropical ferns." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013484.
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Oshima, Júlia Emi de Faria. "Movement ecology and spatial distribution of Tayassu pecari in heterogeneous tropical landscapes /." Rio Claro, 2019. http://hdl.handle.net/11449/183519.
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Orientador: Milton Cezar RibeiroResumo: Modificações da cobertura do solo, perturbações antropogênicas e mudanças climáticas na região Neotropical têm sido associadas à crise da biodiversidade. Nesta tese, o objetivo principal foi investigar os efeitos que a estrutura da paisagem (incluindo a perturbação antropogênica) e a qualidade do habitat têm na distribuição espacial, nos padrões de movimento e na seleção de habitat da queixada - Tayassu pecari. Esta espécie é o único ungulado florestal Neotropical que forma grandes bandos e é uma espécie-chave nos ecossistemas florestais, pois sua extinção local pode causar perdas adicionais de biodiversidade por meio de efeitos em cascata. Ainda assim, pouco se sabe sobre uso do espaço e movimentos de queixadas em escala fina. Para tanto, estudamos a distribuição e movimentação da espécie em diferentes escalas e biomas do Brasil, investigando quais variáveis de paisagem influenciaram a mesma em diferentes escalas e ordens de seleção. Nossos resultados mostram fortes efeitos negativos da modificação da paisagem e fragmentação do habitat na distribuição de queixadas, restando apenas 47% do território brasileiro com áreas adequadas para a espécie. Verificamos que menos da metade de todas as áreas protegidas nos biomas Cerrado e Mata Atlântica têm um habitat adequado para a queixada. Para a análise do movimento, rastreamos 30 indivíduos com colares de GPS de julho de 2013 a outubro de 2016 no Pantanal e no Cerrado do estado do Mato Grosso do Sul. Nossos principais resultados mos... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Land cover modifications, anthropogenic disturbances and climate change in the Neotropical region have been linked to the biodiversity crisis. This thesis proposal was to investigate the effects that landscape structure (including anthropogenic disturbance) and habitat quality have in the spatial distribution, in the movement patterns and in the habitat selection of the white-lipped peccary - Tayassu pecari (WLP). This species is the only Neotropical forest ungulate that forms large herds, and it is a keystone species in forest ecosystems because its local extinction may cause additional biodiversity losses through cascading effects. Still, little is known about WLPs space use and fine-scale movement. For that aim we studied the species distribution and movements in different scales and biomes of Brazil, investigating which landscape variables would influence the species in different scales and orders of selection. Our findings show strong negative effects of landscape modification and habitat fragmentation on white-lipped peccary distribution, with only 47% of the Brazilian territory with suitable areas for the species. We also found that less than half of all protected areas in the Cerrado and the Atlantic Forest biomes have suitable habitat for WLP. For the movement analysis we tracked 30 individuals with GPS collars from July 2013 to October of 2016 in the Pantanal and in the Cerrado of Mato Grosso do Sul state. Our main results showed a positive selection of WLP for fore... (Complete abstract click electronic access below)
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Ruiz, Jaen Maria. "The Relationship between Biodiversity and Ecosystem Function in Tropical Ecosystems." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104676.
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Experimental studies, in temperate grasslands, assessing the role of biodiversity and its effects on ecosystem functioning have generally shown that a decline in species number has negative effects on ecosystem functioning. Even though, this relationship has been intensively studied in the last ten years, little is known about it in complex and hyperdiverse tropical ecosystems and where species diversity is not manipulated. My research examines the relationship between biodiversity and ecosystem functioning in natural tropical forests with a special focus on scale. This research centers on field studies. The field studies address the relationship between natural tree biodiversity and aboveground biomass, as the ecosystem function of interest, in forest plots of similar physiognomy but different species composition. Specifically, I explored the following questions: (1) How can the relationship between biodiversity and ecosystem functioning be detected in a naturally varying environment and space?, (2) How can different measures of diversity (species versus function) explain tree carbon stocks?, (3) Can we confound the effect of species diversity on tree carbon storage with that of forest structure?, (4) How does this relationship change with different spatial scales?, and (5) Can we extrapolate the results of biodiversity-ecosystem functioning found in experimental plantations to natural forests? Overall, my thesis has found that environmental factors related to topography, soil physical factors, and nutrients have little effect on aboveground biomass in tropical ecosystems. Species richness alone cannot be used as a predictor for aboveground biomass, however, if reduced to functional types, its explanatory power increases. Functional traits can be useful to unveil the relationship of aboveground biomass and tree diversity, by reducing species to functional types. Forest structure correlates strongly with aboveground biomass independently of scale, but forest structure is interlinked with species functional traits. Finally, we have to be cautious in extrapolating results found in experimental plantations to natural forests.Des études expérimentales qui ont été effectuées dans des systèmes expérimentaux herbacés du milieu tempéré afin d'évaluer le rôle de la diversité biologique et ses effets sur le fonctionnement de l'écosystème ont généralement pu montrer que le déclin dans le nombre d'espèces a un effet négatif sur le fonctionnement de l'écosystème. Même si cette relation a été étudiée de façon intensive au cours des dix dernières années, très peu est encore connu à ce propos dans les écosystèmes tropicaux, beaucoup plus complexes et mégadiversifiés. Mes travaux de recherche examinent la relation entre diversité biologique et fonction de l'écosystème dans les forêts naturelles tropicales, en mettant l'emphase sur la question d'échelle. Cette recherche est basée sur une approche de terrain, en opposition avec une approche théorique. L'approche de terrain aborde la relation entre la diversité biologique à l'état naturel et les fonctions d'écosystème dans des parcelles forestières de physionomies similaires mais d'une composition en espèces différente. De façon plus spécifique, j'explore les questions suivantes : (1) Comment la relation entre diversité biologique et fonction d'écosystème peut-elle être détectée dans un environnement et un espace naturel changeant?, (2) Comment différentes mesures de diversité (espèces vs fonction) expliquent-elles les stocks de carbone dans les arbres?, (3) Pouvons-nous confondre l'effet de la diversité en espèces sur l'entreposage du carbone dans les arbres avec l'effet de la structure de la forêt? (4) Comment cette relation change-t-elle avec différentes échelles spatiales? (5) Pouvons-nous extrapoler les résultats obtenus dans des plantations expérimentales aux forêts naturelles dans les tropiques en ce qui a trait à la relation entre biodiversité et fonction d'écosystème? Ainsi, ma thèse montre que pour les écosystèmes tropicaux, les facteurs environnementaux tels que ceux reliés à la topographie, les facteurs physiques et les nutriments des sols ont peu d'effet sur l'entreposage du carbone dans les arbres. De plus, la richesse en espèces ne peut pas à elle prédire de l'entreposage de carbone dans les arbres, cependant lorsque celle-ci est divisée par types fonctionnels, sa puissance explicative augmente. Les traits fonctionnels peuvent donc être utiles pour révéler une relation entre le stockage du carbone et la diversité en arbres en réduisant les espèces en des types fonctionnels. La structure de la forêt est le moteur principal du stockage arboricole du carbone indépendamment de l'échelle, par contre cette dernière est reliée aux traits fonctionnels des espèces. Finalement, nous avons pu montrer que la prudence est de mise en ce qui concerne toute possible extrapolation de résultats provenant de plantations expérimentales à des forêts naturelles dans les tropiques.
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Garpe, Kajsa. "Effects of habitat structure on tropical fish assemblages." Doctoral thesis, Stockholm University, Department of Zoology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6767.
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Rates of habitat alteration and degradation are increasing worldwide due to anthropogenic influence. On coral reefs, the loss of live coral reduces structural complexity while facilitating algal increase. In many coastal lagoons seagrass and corals are cleared to make room for cultivated macroalgae. This thesis deals with reef and lagoon habitat structure and how fish assemblage patterns may be related to physical and biological features of the habitat. It further examines assemblage change following habitat disturbance. Four studies on East African coral reefs concluded that both the abundance and species richness of recruit and adult coral reef fish were largely predicted by the presence of live coral cover and structural complexity (Papers I-III, VI). Typically, recruits were more selective than adults, as manifested by limited distributions to degraded sites. Paper VI compared short- and long-term responses of fish assemblages to the 1997-1998 bleaching event. The short-term response to coral mortality included the loss of coral dwelling species in favour of species which feed on algae or associated detrital resources. Counterintuitively, fish abundance and taxonomic richness increased significantly at one of two sites shortly after the bleaching. However, the initial increase was later reversed and six years after the death of the coral, only a limited number of fish remained. The influence of fleshy algae on fish assemblages was studied in algal farms (Paper IV), and examined experimentally (Paper V). The effects of algal farming in Zanzibar were significant. Meanwhile, manually clearing algal-dominated patch reefs in Belize from macroalgae resulted in short-term increases of abundance, biomass and activity of a few species, including major herbivores. The findings of this thesis demonstrate the significance of habitat as a structuring factor for tropical fish assemblages and predicts that coral death, subsequent erosion and algal overgrowth may have substantial deleterious impacts on fish assemblage composition, abundance and taxonomic richness, with recovery being slow and related to the recovery of the reef framework.
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Faruk, Aisyah. "The impact of oil palm conversion on tropical amphibians." Thesis, Queen Mary, University of London, 2013. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8458.
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Agriculturally-altered habitats, especially oil palm plantations, are rapidly dominating the Southeast Asian landscape. Although recent studies have shown reduced species diversity associated with this commodity, data on amphibian diversity are rare. The following thesis explores the impact of oil palm plantations on amphibians in Peninsular Malaysia based on (1) amphibian biodiversity, (2) quality and use of breeding sites, (3) habitat use and (4) parasitism. Contrary to expectation, not all metrics of biodiversity differed between oil palm plantations and secondary forest sites. Amphibian community composition, however, differed greatly between the two habitat types, with oil palm communities being dominated by species known to prosper in disturbed habitats, indicating that the community is currently of limited conservation value. Within plantations, temporary pools were found to serve as important breeding habitats for amphibians so a focused study on the characteristics of these pools was carried out. Although we found differences between pools, the proportion of occupied pools did not differ significantly between plantation and forest sites. I did observe evidence of breeding site preferences of least concern, plantation amphibians, along with habitat partitioning between species, a similar pattern also seen in forest communities. I compared parasite burdens between habitats by screening for the fungus Batrachochytridium dendrobatidis (Bd) and for nematode parasite load. Bd was not detected in any of my samples and there was no difference in nematode loads between habitat types. However, patterns of nematode prevalence was affected by host type, while nematode intensity was dependent on an interaction between host and body size. The final chapter indicates that in terms of parasite, the host environment is the most important. Additionally, differences in host-parasite patterns between habitats indicate a possible underlying problem that rapid biodiversity censuses would be unable to detect.
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Dibog, Luc. "Biodiversity and ecology of termites (Isoptera) in a humid tropical forest." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322058.
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Husband, Rebecca. "The molecular ecology of arbuscular mycorrhizal fungi in a tropical forest." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274547.
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Sunderland, Terence Christopher Heesom. "The taxonomy, ecology and utilisation of African rattans (Palmae: Calamoideae)." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365084.
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Hoyos, Santillán Jorge. "Controls of carbon turnover in tropical peatlands." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14085/.
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Lowland tropical peatlands can act as sinks and sources of carbon, interchanging greenhouse gases (GHG) with the atmosphere. Despite the importance of lowland tropical peatlands in the past, present and future global carbon cycle, uncertainties exists about the controls regulating the processes of carbon turnover. Therefore, this study examined different controls of carbon turnover, including abiotic, biotic and anthropogenic. For this purpose, six peatlands with different dominant vegetation were selected in the north western region of the Republic of Panama (9° 4' 16.06" N; 82° 6' 28.98" W). Two phasic communities were used as experimental models; Raphia taedigera palm swamps and mixed forest swamps with Campnosperma panamensis. A combination of in situ and ex situ experiments were performed between March 2010 and November 2012: i) ex situ respirometric assays were used to quantify differences in carbon turnover through the peat profile under different redox regimes, ii) litter bags experiments were used to investigate the effect of plant materials with distinct botanical origins on peat accumulation, iii) the effect of vegetation on greenhouse gases emissions was assessed with in situ and ex situ experiments and iv) land use change (LUC) was monitored to evaluate its consequences on the short term carbon turnover processes. Ex situ respirometric assays suggested that organic matter composition of peat plays a major role in controlling the potential CO2 and CH4 production. Under anaerobic conditions, the potential CO2 and CH4 production decreased with depth. The potential CO2 and CH4 productions in the surface peat layers of the anaerobic assays were 7 and 120 fold higher than those in deeper layers of the peat profile respectively. The change in redox regime affected the carbon turnover; the CO2 potential production in the surface layers (< 50 cm depth) increased 20 fold when exposed to aerobic conditions, whilst the deeper layers (> 50 cm depth) increased 47 fold. In contrast, CH4 production was reduced two orders of magnitude under aerobic conditions. Tissue types of R. taedigera and C. panamensis showed different in situ decomposition rates. Decomposition was significantly slower belowground than at the surface, reflecting the importance of the redox regime on the litter decomposition. Roots presented the lowest in situ decomposition rates among tissues both at the surface (R. taedigera: 0.59 ± 0.04 y-1; C. panamensis: 0.45 ± 0.01 y-1) and belowground (R. taedigera: 0.13 ± 0.01 y-1; C. panamensis: 0.17 ± 0.005 y-1). Macromolecular analyses revealed that roots and stems have similar composition to the peat material accumulated in deeper layers. Vegetation exerted a direct control on GHG fluxes from lowland tropical peatlands. In both ex situ and in situ measurements, fluxes of CO2 and CH4 varied with vegetation activity. In terms of CO2eq (Addition of mass flow of GHG, converted with the global warming potential of each gas), the agricultural LUC increased CO2eq emissions from the R. taedigera swamp at Cricamola by ca. 20 t CO2eq ha-1 y-1. At the pristine site, CO2, CH4 and N2O contributed with ca. 90, 9 and 1 % of the TCO2eq respectively. In contrast, in the anthropogenically impacted plot, CO2, CH4 and N2O contributed with ca. 29, 69 and 2 % of the TCO2eq respectively. Water table strongly influenced the carbon turnover. Under flooded conditions (water table at or above the surface; 0 to 0.15 m), the CH4 emissions were ca. 4 times higher in comparison with those where the water table was below the surface (−0.01 to −0.4 m). In contrast, CO2 emissions were ca. 1.5 times higher when the water table was below the surface. It was concluded that the interdependence of hydrology, peat composition and vegetation activity are the main factors controlling carbon turnover in the lowland peatlands of the north western region of Panama. This thesis has shown that fine scale alterations of these three factors can have large scale consequences, demonstrating sensitivity to perturbations and ease shift of lowland tropical peatlands from carbon sinks to carbon sources.
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Walker, Jonathan S. "Feeding ecology and rarity of frugivorous birds in tropical rain forest." Thesis, Manchester Metropolitan University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400944.
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Jali, Dulima Binti. "Nitrogen mineralisation, litter production and cellulose decomposition in tropical peat swamps." Thesis, Royal Holloway, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269744.
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Wan, Ahmad Wan Juliana. "Habitat specialisation of tree species in a Malaysian tropical rain forest." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368534.
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This thesis investigates the relationship between spatial distribution of tropical trees and variation in edaphic factors, particularly soil nutrient supply, and tests the importance of interspecific differences in growth rates and foliar nutrient concentrations as determinants of habitat specialisation. The distribution of some tree species at Pasoh Forest Reserve, Peninsular Malaysia, was correlated with variation in soil properties, especially available P concentrations, on a 50 ha plot. Seeding relative growth rates were highest on the alluvial soils, which had higher available P than the shale-derived soils in the absence of nutrient addition. The effect of habitat variation (characterised in terms of their nutrient and water availability) on tree growth of 115 species was examined within and between species. Overall, differences in tree growth rates between habitats correspond to variation in the pattern of nutrient supply and not water availability. Despite significant differences in growth rates between habitat types for some of the species, the differences in tree growth were a poor indicator of habitat preferences of tree species as defined by bias in their spatial distribution. Foliar nutrient concentrations of habitat generalists and two kinds of habitat specialists (alluvial and non-alluvial specialists) were compared using phylogenetically controlled comparisons. Sign tests showed only one significant difference in mean foliar nutrient (N, P, K, Ca and Mg) concentrations between distribution categories. The distribution of the differences in foliar mg concentrations between habitat generalists and alluvial specialists was significant at P < 0.05 and suggested that Mg concentrations were significantly greater in the habitat generalists. These results suggest that foliar nutrient concentrations are unlikely to explain differences between species in their habitat associations with respect to soil types at Pasoh.
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Machovina, Brian. "The Role of Agriculture and Food Consumption in Tropical Conservation." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1841.
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A growing human population, shifting human dietary habits, and climate change are negatively affecting global ecosystems on a massive scale. Expanding agricultural areas to feed a growing population drives extensive habitat loss, and climate change compounds stresses on both food security and ecosystems. Understanding the negative effects of human diet and climate change on agricultural and natural ecosystems provides a context within which potential technological and behavioral solutions can be proposed to help maximize conservation. The purpose of this research was to (1) examine the potential effects of climate change on the suitability of areas for commercial banana plantations in Latin America in the 2050s and how shifts in growing areas could affect protected areas; (2) test the ability of small unmanned aerial vehicles (UAVs) to map productivity of banana plantations as a potential tool for increasing yields and decreasing future plantation expansions; (3) project the effects on biodiversity of increasing rates of animal product consumption in developing megadiverse countries; and (4) estimate the capacity of global pasture biomass production and Fischer-Tropsch hydrocarbon synthesis (IGCC-FT) processing to meet electricity, gasoline and diesel needs. The results indicate that (1) the overall extent of areas suitable for conventional banana cultivation is predicted to decrease by 19% by 2050 because of a hotter and drier climate, but all current banana exporting countries are predicted to maintain some suitable areas with no effects on protected areas; (2) Spatial patterns of NDVI and ENDVI were significantly positively correlated with several metrics of fruit yield and quality, indicating that UAV systems can be used in banana plantations to map spatial patterns of fruit yield; (3) Livestock production is the single largest driver of habitat loss, and both livestock and feedstock production are increasing in developing biodiverse tropical countries. Reducing global animal product consumption should therefore be at the forefront of strategies aimed at reducing biodiversity loss; (4) Removing livestock from global pasture lands and instead utilizing the biomass production could produce enough energy to meet 100% of the electricity, gasoline, and diesel needs of over 40 countries with extensive grassland ecosystems, primarily in tropical developing countries.
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Ho, Wai-hong, and 何偉康. "Biodiversity, ecological and ultrastructural observations of Fungi on wood submerged in tropical streams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31237010.
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Mitchell, Thomas Carly. "The ecology of Macaranga (Euphorbiaceae) trees in primary lowland mixed Dipterocarp forest, Brunei." Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/251702.
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Soares, Marcelo de Oliveira. "Ecologia das medusas (CNIDARIA: SCYPHOZOA, CUBOZOA) na enseada do mucuripe, fortaleza, Nordeste do Brasil." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=3256.
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FundaÃÃo de Amparo à Pesquisa do Estado do CearÃAs medusas sÃo importantes componentes do zooplÃncton marinho e de interesse cientÃfico devido a seus impactos ecolÃgicos, econÃmicos e de saÃde pÃblica, entretanto poucos estudos abordam a ecologia das medusas no Nordeste do Brasil. O objetivo geral da dissertaÃÃo foi: analisar a Ecologia das medusas (Cnidaria: Scyphozoa, Cubozoa) na enseada do Mucuripe em Fortaleza, Nordeste do Brasil. Os objetivos especÃficos incluem: analisar a abundÃncia; a freqÃÃncia absoluta e relativa das espÃcies de medusas e o estudo da estrutura populacional das espÃcies Lychnorhiza lucerna, Chrysaora lactea e Chiropsalmus quadrumanus. As coletas foram realizadas de janeiro de 2004 a fevereiro de 2005 atravÃs de arrasto-de-praia na enseada do Mucuripe em Fortaleza, Estado do CearÃ. A dissertaÃÃo està estruturada em 5 capÃtulos para facilitar a submissÃo a periÃdicos cientÃficos. O capÃtulo 1 aborda uma introduÃÃo geral à dissertaÃÃo com aspectos geogrÃficos, metereolÃgicos e oceanogrÃficos. O capÃtulo 2 aborda a estrutura da comunidade de medusas com anÃlise da abundÃncia e freqÃÃncia das espÃcies estudadas e estudo com tÃcnicas de agrupamento e Ãndices de diversidade, dominÃncia e eqÃitabilidade. O capÃtulo 3, 4 e 5 estudam, respectivamente, a estrutura das populaÃÃes das medusas Lychnorhiza lucerna, Chrysaora lactea e Chiropsalmus quadrumanus na enseada do Mucuripe, Nordeste do Brasil.
The jellyfishes are important components of marine zooplancton and they have scientific interest due to its impacts on the ecology, the economy and the public health, althought few studies had approached the ecology of the jellyfishes from north-eastern Brazil. The general objective of the dissertation was: to analyze the Ecology of the jellyfishes (Cnidaria: Scyphozoa, Cubozoa) in the cove of the Mucuripe in Fortaleza, Northeast of Brazil. The specific objectives include: to analyze the abundance; the absolute and relative frequency of the species of jellyfishes and the study of the population structure of the species Lychnorhiza lucerna, Chrysaora lactea and Chiropsalmus quadrumanus. The collections were done from January of 2004 to February of 2005 through trawl in the cove of the Mucuripe in Fortaleza, Cearà state. The dissertation is structured in 5 chapters to facilitate the submission for scientific journals. The chapter 1 approaches general introduction to the dissertation with meteorological, geographical and oceanographic aspects. Chapter 2 approaches the community structure of jellyfishes with the analysis of the abundance and frequency of the studied species; study with cluster, and indices of diversity, dominance and evenness. Chapters 3, 4 and 5 study, respectively, the structure of the jellyfishes populations of Lychnorhiza lucerna, Chrysaora lactea and Chiropsalmus quadrumanus in the cove of the Mucuripe, Northeast of Brazil.
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Soares, Alexandre Goulart. "Sandy beach morphodynamics and macrobenthic communities in temperate, subtropical and tropical regions : a macroecological approach." Thesis, University of Port Elizabeth, 2003. http://hdl.handle.net/10948/293.
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A comprehensive study involving 52 microtidal beaches spanning from reflective to dissipative states and located in tropical, subtropical and temperate regions in the Atlantic, Pacific and Indian oceans was carried out to unravel the relative roles of latitude and beach morphodynamics in determining beach macrobenthic species richness, abundance, biomass and mean individual body sizes. Since beach slope is one of the most important factors controlling beach fauna, a model based on beach geometry was applied to the sub-aerial beach deposit to understand the role of physical factors in predicting equilibrium beach slopes. Additionally, it was tested if the occurrence of beach types is related to latitude, and how physical factors change with morphodynamics and latitude. The beach morphometric model makes three assumptions: 1) that the cross-section of a beach deposit is equivalent to a right-angled triangle, 2) that the physical hydrodynamic factors (wave height and spring tide amplitude) and the beach deposit characteristics (sand grain size, beach slope and width) are interchangeable with their geometric counterparts producing an equation to explain beach geometry, and 3) that the predicted beach slope is in equilibrium with the hydrodynamic and sedimentological forces. The equation for predicting beach slope was derived and then tested against field data collected over 52 beaches. The predicted slopes were not significantly different from the observed slopes of the studied natural beaches. However some estimated slopes were different than observed ones. Possible sources of deviation between calculated and observed slopes may be the systematic sampling errors associated with field data. Alternatively, observed slopes could be the result of past hydrodynamic conditions, explaining the differences with the slopes calculated by the beach morphometric model, which assumes a state of equilibrium between beach slope and hydrodynamic conditions. A higher correlation of beach faunal structure with observed slopes rather than with present hydrodynamic conditions could then be indicative of faunal responses to previous hydrodynamic conditions in the same way was the observed slopes. The beach morphometric model could therefore be also useful in predicting faunal responses to changing hydrodynamic conditions. Since the model does not consider wave period, it is concluded that further tests should be done using laboratory and time-series field data and incorporating the role of wave period and beach permeability to ascertain its predictive value. Tropical regions had significantly more beaches in a reflective state than temperate and subtropical regions. Some tropical beaches were fronted by coral reefs, which not only provided coarse carbonate particles, but also additionally dissipated the low wave energy present in these climatic areas. Only one dissipative beach with high energy was found in the tropics, in southeast Madagascar. Temperate and subtropical regions, on the other hand, were dominated by dissipative beaches with medium to fine sands. Open oceanic reflective beaches were non-existent in the subtropics and rare in temperate regions, only occurring in estuaries, enclosed bays or on islands facing the continent. Intermediate beaches were more common in the subtropics but also occurred frequently in the other two regions, having higher energy in temperate regions. Reflective beaches had significantly steeper slopes, coarser sands, smaller waves and shorter swash lengths when compared to dissipative beaches. Additionally, reflective beaches were narrower, had deeper water tables and in consequence shorter saturation zones. Wave periods and surfzone widths were on average larger on dissipative than on reflective beaches. The frequency of occurrence of beach types is therefore related to the climatic signature of each latitude. Mid latitudes would be predicted to have more dissipative beaches with large and long waves because of their proximity to the storm generating belt around 50-60° S - these beaches will have a predominantly finer sands because of the input by rivers in rainy areas. Lower latitudes will have more reflective beaches due to a modal low energy wave climate and also because of the presence of inshore and offshore biotic structures such as coral reefs that dissipate even more the energy from the waves. Tropical and subtropical regions had larger marine species pools than temperate regions. After controlling for biogeographical differences in total species pool, dissipative beaches were on average significantly richer than intermediate and reflective beaches. Crustaceans were also more diverse on dissipative beaches, this difference being not significant for either molluscs or polychaetes. Significant relationships were found between total beach species richness (with or without terrestrial species), crustacean and mollusc species richness with beach morphodynamics as represented by the Dean’s index. Indices incorporating the role of tide, such as BSI, were less important in predicting species richness on the microtidal beaches studied here. Several other physical factors were also significantly correlated with species richness, the most important being the Beach Deposit Index, i.e. BDI, a composite index of beach slope and grain size. The highest correlation was between BDI and relative species richness, i.e. local beach species richness / regional species richness. Total regional marine species richness was higher in Madagascar and North Brazil (tropical beaches) than in Southeast Brazil (subtropical), or the West Coast of South Africa and South-Central Chile (temperate beaches). Not only was the pool of species capable of colonizing beaches richer in tropical and subtropical regions, but also local diversity of each morphodynamic beach type was higher among tropical beaches than their temperate counterparts. Although the results of this study agree with the predictions of the swash exclusion hypotheses, several reflective and intermediate beaches had higher species richness than predicted before and this seems to be linked to the presence of finer sediments and a less turbulent flow for larvae to settle. It is concluded that beach species richness is not necessarily controlled by one major morphodynamic parameter; this control is complex and probably involves multiple interacting biotic (biological interactions) and abiotic (e.g. grain size, wave height, beach slope and width, water table) factors. Species richness seems to be controlled on two different scales: on an evolutionary one where tropical and subtropical regions have higher regional and local diversity due to higher speciation rates; and on an ecological scale, where fine grained sand beaches have their carrying capacity enhanced by higher larval settlement rates and survival of recruits towards adulthood. On average dissipative beaches had higher total densities and macrofaunal abundances than reflective ones. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. were also more abundant on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between total abundance, crustacean species richness and beach morphodynamics as represented by the Dean’s index. Again, BSI was less important than individual physical factors in determining faunal abundance on the studied microtidal beaches. Several other physical factors were also significantly correlated with abundance, the most important being the Beach Deposit Index (BDI). The highest correlation was between BDI and total macrofaunal abundance. Factors related to surf zone processes, and possibly productivity, were highly correlated with total community, crustaceans, Excirolana spp. and terrestrial species abundances. The abundances of polychaetes and molluscs were better correlated with factors related to the beach deposit (BDI, slope, grain size and water table depth). Significant differences were observed between latitudinal regions for the average beach and also for each beach type. In general temperate beaches harboured larger community densities and abundances, and also crustacean, Excirolana spp. and terrestrial abundances. Mollusc and polychaete abundances were larger on subtropical and tropical beaches. The control of abundance on a sandy beach is complex and involves multifactorial processes at evolutionary and ecological scales. At evolutionary scales animals seem to attain higher abundances in the region where they first evolved, e.g. amphipods and isopods in temperate regions. At ecological scales they attain higher abundances where productivity is higher (total macrofaunal, crustaceans, Excirolana spp., terrestrial spp.) or where the settlement environment is more benign (molluscs and polychaetes). Dissipative beaches supported larger average and total community biomass than reflective beaches. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. also had larger biomass on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between the biomass of community and taxonomic groups with beach morphodynamics as represented by the Dean’s morphodynamic index. On the microtidal beaches studied here, BSI was less important than other morphodynamic indices and single physical factors in determining faunal biomass and mean individual body size. Surf zone characteristics such as wave height, period and surf zone width had the highest correlations with community, crustacean.
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Dislich, Ricardo. "Análise da vegetação arbórea e conservação na Reserva Florestal da Cidade Universitária \"Armando de Salles Oliveira\", São Paulo, SP." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/41/41134/tde-23012006-225920/.
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Este trabalho analisa aspectos, em diversas escalas temporais e espaciais, da estrutura e dinâmica da comunidade arbórea na Reserva da Cidade Universitária Armando de Salles Oliveira (CUASO) (23º33\' S, 46º43\' W), em São Paulo, SP. A partir dos dados obtidos são sugeridas ações de manejo para fins de conservação da comunidade arbórea no local. A Reserva é uma mancha de floresta secundária com cerca de 10 ha de área. O histórico (1930-1994) das modificações da paisagem no entorno (330 ha) da Reserva é descrito, e evidencia o processo de urbanização ocorrido no período, com conseqüente diminuição de área coberta por vegetação herbácea e aumento da área coberta por construções. As áreas florestadas sofreram declínio e posterior recuperação parcial. Cerca de 40% da Reserva tem vegetação com mais de 70 anos de idade, e 22% são áreas com menos de 27 anos de idade, localizadas próximo às bordas. Foi realizado o mapeamento, medição de DAP e identificação de todas as 1157 árvores com DAP > 25 cm em 8,58 ha (Área 1, a área total da Reserva com exceção do lago e uma porção de 1,5 ha dominada por Eucalyptus sp.) e de todas as 1270 árvores com DAP > 9,5 cm em 2 ha (Área 2) no interior da Reserva. Na Área 1 foram encontradas 91 espécies (10,9% exóticas) e índice de Shannon H\' = 3,34 nats/ind., com 33,7% das espécies sendo representadas por apenas um indivíduo. Espécies exóticas e nativas introduzidas estão, em geral, restritas às porções próximas à borda, com exceção de Archontophoenix cunninghamiana. Não existem áreas na Reserva a mais de 110 m de distância da borda, devido ao seu tamanho e formato. Análises de correspondência mostram variação importante na comunidade (DAP > 25 cm) com a distância da borda até cerca de 50 m, mas sugerem maior importância da idade da vegetação na determinação da composição da comunidade. Na Área 2, foram encontradas 103 espécies (10,7% exóticas) e H\' = 3,54 nats/ind. Foram descritas as mudanças na estrutura e composição da comunidade arbórea (DAP ≥ 15,9 cm) ocorridas entre 1992 e 1997 em uma área de 100 x 50 m no interior da Reserva. Densidade e área basal da comunidade total aumentaram consideravelmente no período; diversidade e equabilidade permaneceram praticamente as mesmas, mas diversidade e equabilidade de espécies nativas diminuíram. Entre as árvores com DAP ≥ 9,5 cm, em uma área de 2,1 ha, A. cunninghamiana foi a espécie com maior densidade, com 305 indivíduos (22,5% do total). A espécie mostra preferência por estabelecimento em locais sombreados. A análise da estrutura de tamanhos indica um aumento futuro da densidade relativa da espécie. Dois levantamentos com 2,5 anos de intervalo (DAP ≥ 9,5 cm) mostraram a morte de três dos 154 indivíduos iniciais e o recrutamento de mais 89, levando a um crescimento populacional de 19,4 %.ano-1, muito elevado. CUAKIA, um gap model derivado de KIAMBRAM, foi parametrizado para simular o estado atual da floresta na Reserva. O modelo previu uma fase sucessional inicial dominada por Piptadenia gonoacantha, seguida por uma fase de dominância de Croton floribundus e Alchornea spp. e, posteriormente, por Ficus insipida e outras espécies de dossel tolerantes à sombra e de grande longevidade. A distribuição espacial de árvores em múltiplas escalas espaciais foi analisada usando a função L (modificação de K de Ripley) e g uni e bivariada. O conjunto de indivíduos com DAP > 25 cm apresentou distribuição regular em pequenas escalas (r < 6 m) e agregada em escalas maiores (17 m < r < 115 m). Quase todas as espécies analisadas apresentaram distribuição agregada em alguma escala espacial. Os resultados sugerem competição em pequena escala e limitação de dispersão de sementes como os principais fatores determinantes dos padrões encontrados. Os dados de mapeamento das árvores com DAP > 25 cm foram usados para a divisão da Reserva em áreas de vegetação relativamente homogênea. Análise de correspondência foi usada como ferramenta de ordenação de parcelas circulares (r = 10 m) dispostas em uma grade regular com espaçamento de 10 m. Os valores de cada parcela foram mapeados e com base nestes mapeamentos foram definidas nove zonas de manejo no interior da Reserva. Uma das zonas é quase exclusivamente ocupada por Eucalyptus sp.. Outras apresentam predominância de espécies exóticas e/ou plantadas na Reserva. Sugere-se a introdução de espécies nativas e o controle de exóticas, especialmente A. cunninghamiana, no interior e no entorno da Reserva.This work analyses the structure and dynamics, at several spatial and temporal scales, of the arboreal community in the Reserve of the Cidade Universitária Armando de Salles Oliveira (CUASO) (23º33\' S, 46º43\' W), São Paulo, SP. Based on these data, management actions are suggested, aiming at the conservation of the arboreal community at the site. The Reserve is a secondary forest patch with an area of approximately 10 ha. We describe the 1930-1994 changes in landscape structure in the surroundings (330 ha) of the Reserve, showing the urbanization process in the region. As a consequence, the area covered by grasslands was reduced and the area covered by buildings increased. Forested areas declined and recovered partially afterwards. Roughly 40% of the Reserve encompasses vegetation more than 70 years old and 22% are areas less than 27 years old, located near the edges. We mapped, measured the dbh and identified all 1157 trees with dbh > 25 cm in 8.58 ha (Area 1, the total area of the Reserve excluding the lake and a 1.5 ha-area dominated by Eucalyptus sp.) and all 1270 trees with dbh > 9.5 cm in 2 ha (Area 2) in the Reserve. In Area 1 we found 91 species (10.9% being exotic) and a Shannon index H\' of 3,34 nats/ind., with 33.7% of the species being represented by only one individual. Exotic species and introduced natives were generally restricted to the regions near the edge, with the exception of Archontophoenix cunninghamiana. No place inside the Reserve is more than 110 m away from the edge, due to the size and shape of the Reserve. Correspondence analyses showed important variation of the community (dbh > 25 cm) with distance to the edge up to 50 m, but suggest that age of vegetation is more important in defining the composition of the community. In Area 2 we found 103 species (10.7% exotic) and H\' = 3.54 nats/ind. We analysed structural and compositional changes of the arboreal community (dbh ≥ 15.9 cm) between 1992 and 1997 within a 100 x 50 m plot. Density and basal area of the total community increased considerably in the period; species diversity and evenness remained almost the same, but diversity and evenness of native species decreased. In a 2.1 ha area inside the Reserve, A. cunninghamiana was the species with the highest density among trees with DBH ≥ 9.5 cm, with 305 individuals (22.5% of total). The species shows preference for establishment in shady sites. The size structure analysis indicates a future increase in the relative density of the species. Two surveys with a 2.5 years interval (DBH ≥ 9.5 cm) showed the death of three of the initial 154 individuals and the recruitment of 89 more, leading to a population growth of 19.4 %.year-1, a very high rate. CUAKIA, a gap model derived from KIAMBRAM, was parameterized to simulate the present state of the forest in the Reserve The model predicted an initial sucessional phase dominated by Piptadenia gonoacantha, followed by a phase dominated by Croton floribundus and Alchornea spp. and, later, by Ficus insipida and other shade-tolerant and long-living canopy species. The spatial distribution of trees was analysed using the L (modification of Ripley\'s K) and g functions, in their univariate and bivariate forms. The total pool of individuals with dbh > 25 cm showed uniform distribution at small scales (r < 6 m) and clumped distribution at bigger scales (17 m < r < 115 m). Almost all species showed clumped distribution at some scale. The results suggest competition at small scales and seed dispersal limitation as the main determinants of the patterns found. The data from the mapping of trees with dbh > 25 cm were used to divide the Reserve into areas covered with relatively homogeneous vegetation. Correspondence analysis was used to ordinate circular plots (r = 10 m) laid out on a regular 10 m-interval grid. Scores of each plot were mapped and this mapping was used to define nine management zones inside the Reserve. One of the zones is almost exclusively occupied by Eucalyptus sp.. Others are dominated by exotics or trees which were planted in the Reserve. We suggest the introduction of native species and the control of exotics, especially A. cunninghamiana, inside the Reserve and in its surroundings.
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Coelho, de Souza Fernanda. "The evolution of carbon cycle in tropical forests : integrating ecology and evolution." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/20880/.
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Present-day patterns of species diversity and their ecological characteristics in the tropics result from more than 100 million years of evolution. The environmental conditions in which species evolved have left a fingerprint on their functional traits, so investigating this legacy may improve our understanding of current patterns of ecosystem function and potentially guide us in managing our resources more wisely as the climate changes. Amazonian forests are ideal for such a study as they play a major role in the global carbon cycle and harbour a remarkable diversity of angiosperm lineages and species with a broad range of ecologies. Here, I linked data from long-term forest inventory plots, environmental conditions, and a newly constructed phylogeny in order to investigate the legacy of evolution on modern-day patterns of ecosystem function and diversity. I show first that evolutionarily related taxa are more similar in their demography and carbon storage and processing ability (i.e. wood density, potential size, growth and mortality-rates) than expected by chance. Thus, the degree of evolutionary history shared between lineages is a good proxy for their carbon traits. Next, using the evolutionary relationships among lineages I find a legacy of evolutionary history on current patterns of whole ecosystem productivity across the Amazon, such that communities with more evolutionarily distinct lineages have greater wood productivity. Finally, I compare the role of heritability versus selection on shaping lineages preferences for certain environments (i.e. soils and climate). I show that there is a tendency for evolutionarily related taxa to have more similar environmental preferences than expected by chance, but that certain kinds of habitat specialisation have also occurred repeatedly and independently in many lineages. These findings are important for understanding the future of Amazonian forests under global change and support an evolutionary perspective as an important component of conservation strategies.
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Stewart, Christopher Gill. "Ecology and physiology of light-demanding trees in a tropical montane forest." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624529.
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Shaffer, Justin Park, and Justin Park Shaffer. "Endohyphal Bacteria of Tropical Plant-Associated Fungi: Diversity, Evolutionary Relationships, and Ecology." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625601.
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A growing understanding of complex biotic interactions clarified the importance of symbioses with respect to the ecology and evolution of life. In particular, knowledge of symbioses between eukaryotes and microorganisms such as bacteria and fungi has revolutionized the fields of medicine and agriculture, and made clear the roles of microbes in fostering human and environmental sustainability. For example, diverse fungi associate with the seeds of plants following dispersal. These fungi can influence seed survival and germination in a host-specific and spatially explicit manner, thus influencing plant community dynamics in agricultural and natural systems. In species-rich tropical forests, seed-fungus interactions are emerging as one of the most important aspects of plant demography and community ecology. However, even closely related fungi can have opposing effects on seeds of particular plants, such that mechanisms influencing host-specific effects require further attention. Such mechanisms can include genomic traits of fungi and hosts, and the environmental context of interactions. However, studies have shown that many fungi also harbor endosymbionts than can influence their functional traits. In particular, fungi often harbor endohyphal bacteria that influence fungal phenotypes. This suggested the potential for similar, co-occurring microbes to influence the ecology of seed-associated fungi. Here, I explore the diversity, evolutionary relationships, and influence on fungal phenotypes of endohyphal bacteria inhabiting seed- and leaf-associated fungi with a focus that begins in tropical forest ecology and expands to include gene expression in an emerging model system from the temperate zone.
To determine the occurrence, abundance, taxonomic diversity, and phylogenetic diversity of endohyphal bacteria among tropical seed-associated fungi, my coauthors and I used PCR and fluorescence microscopy to screen members of two common orders of seed-associated fungi, comparing their communities to those in closely related foliar endophytic fungi. We revealed a high frequency and diversity of endohyphal bacteria among both groups of fungi. We then used phylogenetic and community ecological analyses to show a lack of congruence between phylogenies of bacteria and fungi. Although seed-associated and foliar endophytic fungi share evolutionary histories, they harbor distinct endohyphal bacterial communities.
To explore the influence of endohyphal bacteria on fungal phenotypes important for interactions with seeds, my coauthors and I examined a single fungus-bacterium pair consisting of a member of a well-known group of pathogenic fungi found to harbor an endohyphal bacterium closely related to those with known chitinolytic activity. We created fungal clones that were free of endohyphal bacteria, and carried out a phenotypic microarray assay comparing use of 95 unique carbon sources by cured and uncured clones. Across the majority of substrates, the fungal clones harboring endohyphal bacteria grew more rapidly and to a greater extent than the cured clones. Thus the endohyphal bacterium was associated with broader substrate use and more effective use of a variety of substrates relevant to plant biology, including seed germination.
To assess the influence of endohyphal bacteria with respect to the outcomes of seed-fungus interactions, my coauthors and I examined six fungus-bacterium pairs and their interactions with the seeds of five tropical pioneer tree species. We showed that although endohyphal bacteria have little impact on colonization of seeds by fungi, they significantly altered the survival and germination of infected seeds. In most cases, endohyphal bacteria reduced the negative impacts of fungi on seeds: strains harboring them responded more similarly to uninoculated controls, whereas strains cured of them exhibited significantly reduced survival and germination. Seeds infected by fungi of the same genotype that differ with respect to the identity of their endohyphal bacteria exhibited differences, but so did seeds infected by strains of those isolates not harboring bacteria, suggesting that factors in addition to the presence of endohyphal bacteria can drive variation in the outcomes of seed-fungus interactions. Together these analyses suggest intricate interactions between fungi and bacteria that result in context-dependent outcomes. This turned our focus to gene expression as a means to understand mechanisms of interactions between endohyphal bacteria and their fungal hosts.
Last, my coauthors and I describe methods we developed to co-culture fungi and their endohyphal bacteria for downstream analysis of differences in gene expression among a fungus-bacterium pair and axenic cultures of each symbiont. We focused on an emerging model system: a foliar endophytic strain of Pestalotiopsis aff. neglecta (Ascomycota) known to harbor an endohyphal bacterium in the genus Luteibacter (Xanthomonadaceae). The focal bacterium is in part reliant on its host fungus for acquisition of certain sulfur-containing compounds such as sulfate. We showed that inoculating a low-methionine growth medium with bacteria recovered in exponential phase from a high-methionine medium supports growth suitable for comparing axenic growth with that in co-culture with its host fungus. Although bacterial cell density in co-cultures was significantly greater than that in axenic cultures, the opposite was true for the host fungus. We expect results from transcriptomics analyses to reflect partial reliance on– and antagonism of Pestalotiopsis by Luteibacter, and here present the first pipeline of methods for examining gene expression for a facultatively symbiotic endohyphal bacterium and its host, a member of the most species-rich and economically important fungal phylum.
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Ilstedt, Ulrik. "Soil degradation and rehabilitation in humid tropical forests (Sabah, Malaysia) /." Umeå : Swedish University of Agricultural Sciences, 2002. http://diss-epsilon.slu.se/archive/00000233/.
Full textAbstract:
Thesis (doctoral)--Swedish University of Agricultural Sciences, 2002.Abstract inserted. Appendix reprints four papers and manuscripts co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.
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Brown, N. D. "Dipterocarp regeneration in tropical rain forest gaps of different sizes." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279886.
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Ulloa, chacón Juan. "Estimation de la diversité acoustique animale en forêt néotropicale." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS120.
Full textAbstract:
La communication par émission sonore est un trait comportemental répandu chez les animaux terrestres. Les riches textures sonores de la forêt neotropicale nous suggèrent que la faune est non seulement abondante, mais aussi diverse et dynamique. Cette facette de la biodiversité peut révéler des informations précieuses sur les communautés animales qui habitent les milieux tropicaux, mais reste largement méconnue. Comment mesurer la diversité acoustique tropicale pour aborder des questions écologiques ? Dans le cadre de l'écoacoustique, nous avons cherché à révéler des structures dissimulées dans le paysage sonore de la forêt neotropicale, et tenter d’expliquer leurs présences à travers les processus écologiques sous-jacents. Tout d’abord, nous avons suivi la dynamique spatio-temporelle d’une empreinte sonore amazonienne, le chant de l’oiseau tropical Lipaugus vociferans, montrant une activité liée à des caractéristiques spécifiques d’habitat. Puis, nous nous sommes intéressés aux communautés d’amphibiens. L’analyse de variables acoustiques et météorologiques nous a permis de mieux comprendre les causes, patrons et conséquences du comportement reproductif explosif. Enfin, nous avons adapté de nouveaux outils de calcul, issus des disciplines de l'apprentissage automatique et de la reconnaissance de formes, pour proposer une analyse efficace, objective et facilement reproductible de grands jeux de données acoustiques. L’écoacoustique, renforcée par des algorithmes informatiques, émerge comme une approche clé pour les programmes de suivis de biodiversité à large échelle, permettant de mieux comprendre et valoriser la diversité de formes de vies unique abritée par la forêt tropicaleAcoustic signalling is a common behavioural trait among terrestrial animals. The rich sound textures of neotropical forest echo that wildlife is not only abundant, but also diverse and dynamic. This facet of biodiversity can reveal valuable insights of animal communities inhabiting tropical environments, yet remains poorly understood. How to best measure tropical acoustic diversity to address ecological questions? Based on the ecoacoustic framework, we explored the soundscape of neotropical forest, revealing patterns and investigating the ecological underlying processes. First, we tracked the spatiotemporal dynamics of an amazonian soundmark, the song of the bird Lipaugus vociferans, showing activity patterns related to specific habitat features. Then, we investigated amphibian communities with very brief reproduction periods. Coupling acoustic and environmental variables, we shed light on the causes, patterns and consequences of explosive breeding events. Finally, we adapted novel computational tools from the machine learning and pattern recognition disciplines to provide an efficient, objective and replicable analysis of large acoustic datasets. Ecoacoustics, powered with computer algorithms, emerge as a suitable approach to scale-up biodiversity monitoring programs, allowing to better understand and cherish the unique diversity of life sustained by tropical forest
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Newmann, Sarah McCarthy. "Plant-soil feedbacks in temperate and tropical forests." Diss., Connect to online resource - MSU authorized users, 2008.
Find full textAbstract:
Thesis (Ph.D.)--Michigan State University. Dept. of Forestry Program in Ecology, Evolutionary Biology and Behavior, 2008.Title from PDF t.p. (viewed on July 13, 2009) Includes bibliographical references (p. 170-184). Also issued in print.
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Gibbons, James M. "Water relations, phenology and drought adaptation of understorey trees in tropical lowland rain forest." Thesis, University of Stirling, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298566.
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Chan, Ka-wang Eric. "Riparian insects and predation by insectivores : energy transfers across tropical land-water ecotones /." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/b40203918.
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Singh, Daljeet. "Comparative studies on the ecology of bottom macrofauna in seasonal and perennial fish ponds and in the adjacent backwaters." Thesis, Central Marine Fisheries Research Institute, 1987. http://eprints.cmfri.org.in/11045/1/Daljeet%20Singh.pdf.
Full textAbstract:
The flora and fauna inhabit at or near the bottom
or sub-bottom layer of aquatic ecosystem may be broadly
considered as benthos. The studies on benthic communities
their distribution and abundance in space and time form an
exciting field of brackishwater studies. The faunestic
composition of tropical estuaries is represented by a wide
spectrum of animals belonging to groups such as Polychaetes,
Crustaceans, Molluscs, Nematodes, fishes etc. Benthos, for
many years, has been a stepchild of ecology depending upon
the thoughts generated by terrestial and water column
colleagues. But with the increasing awareness on the
complex relationship of benthic communities and the
surrounding environment, in which they live, benthic ecologists
have broken these feters and produced original research
and hypothesis, now available to whole ecological world.
As the tropical estuary is a special ecological niche with a
complex dynamic mixture of transitional conditions, the
faunestic composition and their abundance too showed very
Interesting community structures and vary often with wide
seasonal fluctuations.
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Turco, Aldo. "Comparisons of habitat use and diet of herbivorous kyphosids (Genus Kyphosus) in tropical and temperate reefs." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2017. https://ro.ecu.edu.au/theses/1947.
Full textAbstract:
Kyphosids are a well-represented group of mainly herbivorous fishes distributed worldwide. Species within the genus Kyphosus are commonly found in both tropical and temperate areas, with Western Australia having especially high Kyphosus diversity and abundance compared to other regions. Despite being common fishes, much of the ecology of this Genus has not been described. The aim of this study is to compare habitat and food resource use of Kyphosus species in both tropical and temperate reef areas of Western Australia to provide new information about their ecological roles in these systems. To achieve this, the relationship between the abundances of three temperate species (K. sydneyanus, K. gladius, and K. cornelii) and environmental characteristics has been investigated across 20 sites within Marmion Marine Park, on the south-west coast of Australia. All temperate Kyphosus species were found to be significantly more abundant in high-relief reef areas (P < 0.01) and particularly inshore areas (0 to 1 nm from the coast). Juveniles (Lt < 30 cm) were present only in shallow reefs (0 to 6 m) and mostly inshore. Distance-based redundancy analysis showed that most of the variability in juvenile abundance (72-77%) was explained by reef structures (i.e. number of arches, caves, drop-offs, and general vertical relief) and algal assemblages (i.e. E. radiata, green algae, and Sargassum spp.). Changes in abundance of adult fish (Lt ≥ 30cm) were less strongly related to environmental variables (52- 58%), although the number of caves and drop-offs was positively correlated with all three species.
Analysis of the stomach contents of K. sydneyanus, K. gladius, and K. cornelii showed strong differences in diet composition between all species (p < 0.001). An ontogenetic shift in was also present in the first two species (p < 0.001). K. sydneyanus and K. gladius consumed mostly brown macroalgae. However, K. sydneyanus consumed more Sargassum spp. (up to 44% in adults), while K. gladius generally had a higher content of E. radiata in their stomachs (up to 47% in adults). Juveniles of both species consumed less kelp and Sargassum than adults and more green epiphytes (e.g. Derbesia sp.) and red algae (Hypnea sp.). Conversely, the diet of K. cornelii consisted almost entirely of red and green epiphytes, such as Hypnea sp. (30-33%) and Ulva sp. (15- 31%) at both life stages. These results indicate that both K. sydneyanus and K. gladius act as browsers as adults, whilst K. cornelii are grazers. The analyses of the head, mouth, and teeth morphological traits, although showing significant (p < 0.001) differences among species, are not good predictors of diet.
In the coral reef area of Ningaloo Reef, situated in the north-west corner of Western Australia, all Kyphosus species had a higher number of adults on shallow reef slopes exposed to prevailing waves, while juveniles were found predominantly inshore. Environmental variables explained much of the variation in abundances of all surveyed species, in particular of adult K. bigibbus (92%), and K. vaigiensis (91%). Dietary analysis across the two most common Kyphosus species in this tropical area (K. bigibbus and K. cinerascens) found K. bigibbus feed predominantly on brown macroalgae and K. cinerascens on red epiphytes and turf algae. These results suggest a different functional role for these two species, with K. bigibbus acting as a browser and K. cinerascens as a grazer. As with temperate species, morphological traits were significantly different between the two species, but did not explain interspecific variability in diet.
The general differentiation in both distribution and diet among Kyphosus species showed that sympatric species can represent different functional roles (i.e. browsers and grazers). This implies that species need to be identified in monitoring and research programs to avoid erroneous estimates of herbivory activity. Thus, the results here offer a more defined description of the role of Kyphosus species, in both temperate and tropical reef habitats as an essential group of fish participating in different functional groups and at different latitudes in one of the fundamental processes of marine ecosystems which is herbivory.
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Kamau, Peris Wangari [Verfasser]. "Systematic Revision of Pteris L. in Tropical Africa and Ecology of Ferns and Lycophytes in Lowland Tropical Rainforests / Peris Wangari Kamau." Koblenz : Universitätsbibliothek Koblenz, 2012. http://d-nb.info/1029224129/34.
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Trembath, Dane F., and n/a. "The comparative ecology of Krefft's River Turtle Eydura krefftii in Tropical North Queensland." University of Canberra. Resource, Environmental & Heritage Sciences, 2005. http://erl.canberra.edu.au./public/adt-AUC20060711.113815.
Full textAbstract:
An ecological study was undertaken on four populations of Krefft�s River Turtle
Emydura krefftii inhabiting the Townsville Area of Tropical North Queensland. Two sites
were located in the Ross River, which runs through the urban areas of Townsville, and two
sites were in rural areas at Alligator Creek and Stuart Creek (known as the Townsville
Creeks). Earlier studies of the populations in Ross River had determined that the turtles
existed at an exceptionally high density, that is, they were superabundant, and so the
Townsville Creek sites were chosen as low abundance sites for comparison.
The first aim of this study was to determine if there had been any demographic
consequences caused by the abundance of turtle populations of the Ross River. Secondly, the
project aimed to determine if the impoundments in the Ross River had affected the freshwater
turtle fauna. Specifically this study aimed to determine if there were any difference between
the growth, size at maturity, sexual dimorphism, size distribution, and diet of Emydura krefftii
inhabiting two very different populations.
A mark-recapture program estimated the turtle population sizes at between 490 and
5350 turtles per hectare. Most populations exhibited a predominant female sex-bias over the
sampling period. Growth rates were rapid in juveniles but slowed once sexual maturity was
attained; in males, growth basically stopped at maturity, but in females, growth continued
post-maturity, although at a slower rate. Sexual maturity was at 6-7 years of age for males,
which corresponded to a carapace length of 150-160 mm, and 8-10 years of age for females,
which corresponded to a carapace length of 185-240 mm. The turtles were omnivorous,
although in the Ross River they ate more submerged vegetation (by percent amount and
occurrence) than those of the Townsville Creeks. Turtles in Townsville Creeks ingested more
windfall fruit and terrestrial insects.
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Strauß, Axel [Verfasser], and Miguel [Akademischer Betreuer] Vences. "Community ecology and diversity of tropical anuran larvae / Axel Strauß ; Betreuer: Miguel Vences." Braunschweig : Technische Universität Braunschweig, 2010. http://d-nb.info/1175826146/34.
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Campbell, Justin E. "The Effects of Carbon Dioxide Fertilization on the Ecology of Tropical Seagrass Communities." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/693.
Full textAbstract:
Increasing atmospheric CO2 concentrations associated with climate change will likely influence a wide variety of ecosystems. Terrestrial research has examined the effects of increasing CO2 concentrations on the functionality of plant systems; with studies ranging in scale from the short-term responses of individual leaves, to long-term ecological responses of complete forests. While terrestrial plants have received much attention, studies on the responses of marine plants (seagrasses) to increased CO2(aq) concentrations remain relatively sparse, with most research limited to small-scale, ex situ experimentation. Furthermore, few studies have attempted to address similarities between terrestrial and seagrass responses to increases in CO2(aq). The goals of this dissertation are to expand the scope of marine climate change research, and examine how the tropical seagrass, Thalassia testudinum responds to increasing CO2(aq) concentrations over multiple spatial and temporal scales.
Manipulative laboratory and field experimentation reveal that, similar to terrestrial plants, seagrasses strongly respond to increases in CO2(aq) concentrations. Using a novel field technique, in situ field manipulations show that over short time scales, seagrasses respond to elevated CO2(aq) by increasing leaf photosynthetic rates and the production of soluble carbohydrates. Declines in leaf nutrient (nitrogen and phosphorus) content were additionally detected, paralleling responses from terrestrial systems. Over long time scales, seagrasses increase total above- and belowground biomass with elevated CO2(aq), suggesting that, similar to terrestrial research, pervasive increases in atmospheric and oceanic CO2(aq) concentrations stand to influence the productivity and functionality of these systems. Furthermore, field experiments reveal that seagrass epiphytes, which comprise an important component of seagrass ecosystems, additionally respond to increased CO2(aq) with strong declines in calcified taxa and increases in fleshy taxa.
Together, this work demonstrates that increasing CO2(aq) concentrations will alter the functionality of seagrass ecosystems by increasing plant productivity and shifting the composition of the epiphyte community. These results have implications for future rates of carbon storage and sediment production within these widely distributed systems.
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de, Putron Samantha Julie. "The reproductive ecology of two corals and one gorgonian from sub-tropical Bermuda." Thesis, Swansea University, 2003. https://cronfa.swan.ac.uk/Record/cronfa42702.
Full textAbstract:
This study examines the sexual reproductive ecology of three species of corals common on the sub-tropical reefs of Bermuda: the scleractinians Porites astreoides and Madracis mirabilis, and the gorgonian Pseudoplexaura porosa. The reproductive biology of corals in Bermuda is of particular interest because low winter seawater temperatures and geographical isolation make it an extreme of distribution for many of the species there. In addition, the Bermuda platform comprises reef zones that experience gradients of temperature, sediment loading and wave intensity at the different depths. The objectives are twofold; firstly, information is presented on the reproductive mode, sexuality and fecundity of the corals, and the occurrence of lunar periodicity to gamete development, planula release or spawning. The second objective addresses the question of whether environmental variability across the Bermuda platform and between years alters the reproductive cycles of these species. The study species varied in reproductive mode and sexuality. The scleractinian Porites astreoides is a brooder with a mixed sexuality; the gorgonian Pseudoplexaura porosa exhibits gonochorism with broadcasting, and the scleractinian Madracis mirabilis has hermaphroditic colonies with a proposed intermediate 'pseudo-brooding' reproductive mode. Fecundity was variable within and between Po. astreoides colonies but was not related to colony size. There was a relationship between polyp size and gamete production in Ps. porosa. The synchrony of lunar periodicity to spawning or planulae release varied between the species and this is related to the different reproductive modes. The extent that planula release of Po. astreoides was synchronised to the lunar cycle also varied according to the reef zone in Bermuda, a proposed consequence of variable turbidity levels from inshore to offshore. Observed differences in the reproductive effort of Po. astreoides and Ps. porosa, both at the different reef zones within Bermuda, as well across study years, are related to spatial and inter-annual variations in temperature profiles.
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Boucek, Ross E. "Investigating Sub-tropical Community Resistance and Resilience to Climate Disturbance." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2993.
Full textAbstract:
Changes in global climate will likely increase climate variability. In turn, changes in climate variability have begun to alter the frequency, intensity, and timing of climate disturbances. Continued changes in the climate disturbance regime experienced by natural systems will undoubtedly affect ecological processes at every hierarchical scale. Thus, in order to predict the dynamics of ecological systems in the future, we must develop a more mechanistic understanding of how and in what ways climate disturbance affects natural systems. In South Florida, two climate disturbances recently affected the region, a severe cold spell in 2010, and a drought in 2011. Importantly, these disturbances affected an ecosystem of long-term, comprehensive, and persistent ecological study in the Shark River estuary in the Everglades National Park. The aims of my dissertation were to (1) assess the relative severity of these two climate disturbances, (2) identify effects of these disturbances on community structuring, (3) compare community change from the 2010 cold spell with community change from another extreme cold spell that affected sub-tropical China in 2008, (4) assess the effects of the drought on predator prey interactions in the Shark River and (5) apply a spatial approach to predicting population resistance to these events. My results show that the 2010 cold spell was the most severe cold event to affect the Shark River in the last 80 years, while the drought was the worst drought to occur in the last 10 years. The cold spell drove community change that was predictable based on the traits of component species, whereas community change was less predictable using trait-based approaches. When comparing community change from the extreme 2010 event in Florida with the event in China, I identified three consistencies related to community change from extreme cold events that occurred across both events that will help build generalized understanding of community resistance to increasingly extreme climate events in the future. From the trophic study, I found that the drought reduced prey for estuarine piscivores. Not only was prey biomass reduced, the drought drove a compositional shift in prey communities from fish to invertebrates, which are lower in calories. Last, I found that animal movement may create temporally dynamic resistance scenarios that should be accounted for when developing predictive models.
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Hawley, Tanya Joy. "Mechanisms Underlying Frog Occupancy Patterns in a Landscape Mosaic of Tropical Forest and Pasture." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/86.
Full textAbstract:
Habitat modification is the primary cause of amphibian population declines worldwide. Some species survive in modified habitats whereas others become restricted to small, isolated forest patches. Although many studies compare species richness and composition between modified and intact habitats, the factors and mechanisms that maintain biodiversity in these landscapes are poorly understood. I asked how life history traits and habitat features influence interspecific variation in frog occupancy patterns in tropical pasture and forest. To identify mechanisms underlying occupancy patterns, I used experiments to examine how abiotic conditions in different habitats influence the vital rates of tadpoles. I also explored whether tadpoles use a carnivorous foraging strategy to improve performance in nutrient-poor, ephemeral pools in pasture. Although modified and intact habitats offer abiotic environments that differ in quality for frogs, pastures contribute to the maintenance of biodiversity in fragmented landscapes. I detected an equal number of species but substantially different assemblage composition in forest and pasture. Species that occurred in pasture had different traits than those in forest, including larger body sizes, larger clutch sizes, larger geographic ranges, and reproductive modes that depend on water. The occurrence of pasture-specialists was associated with habitat features at small spatial scales, whereas the occurrence of forest-specialists was associated with habitat features at small and large spatial scales. An experiment indicated that abiotic conditions in pastures may deter or facilitate adult movements to breeding sites. Behavioral selection of sites by two model species was consistent with tadpole performance. Tadpoles of a pasture-specialist performed well across the pasture-forest gradient, but abiotic conditions in pasture facilitated faster growth and development than in edge or forest. In contrast, tadpoles of a forest-specialist performed well only in edge and forest. Most tadpoles occupying ephemeral pasture pools were facultative carnivores or cannibals of eggs and hatchlings. Tadpoles may contribute to the regulation of assemblages in pasture pools, influencing the relative abundance and composition of species through differential predation on eggs and hatchlings. The study of factors and mechanisms that contribute to population growth or decline of species can facilitate understanding of assemblage-level patterns of amphibian diversity in modified landscapes.
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Layman, Craig Anthony. "The role of piscivores in a species-rich tropical river." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1224.
Full textAbstract:
Much of the world's species diversity is located in tropical and sub-tropical ecosystems, and a better understanding of the ecology of these systems is necessary to stem biodiversity loss and assess community- and ecosystem-level responses to anthropogenic impacts. In this dissertation, I endeavored to broaden our understanding of complex ecosystems through research conducted on the Cinaruco River, a floodplain river in Venezuela, with specific emphasis on how a human-induced perturbation, commercial netting activity, may affect food web structure and function. I employed two approaches in this work: (1) comparative analyses based on descriptive food web characteristics, and (2) experimental manipulations within important food web modules. Methodologies included monthly sampling of fish assemblages using a variety of techniques, large-scale field experiments, extensive stomach content and stable isotope analyses. Two themes unite the information presented: (1) substantial spatial and temporal variability in food web structure, and (2) how body-size can be used to generalize species-interactions across this complexity. Spatial variability occurred at various scales, from among small fish assemblages on seemingly homogeneous sand banks, to differences among landscape scale units (e.g. between lagoons and main river channel). Seasonal variability was apparent in predation patterns, with relative prey availability and body size primarily resulting in decreasing prey sizes with falling water levels. Body size was also related to functional outcomes of species interactions, for example, a size-based response of prey fishes to large-bodied piscivore exclusion. This pattern was further substantiated at the landscape-scale, as differences in assemblage structure among netted and un-netted lagoons were largely size-based. Trophic position of fish and body size was not found to be related, likely due to the diversity of prey available to consumers, and may signify that commercial netting activity will not decrease food chain lengths. In sum, by describing human impacts within a food web context, I endeavor to provide predictive power regarding a specific human-induced environmental problem, yet still allowing for generality that will broaden the theoretical foundations and applications of food web ecology.