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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Optimizing restoration site selection along the Florida Reef Tract for the coral species Acropora cervicornis and Acropora palmata

King, Samantha 26 April 2019 (has links)
The decline of Acropora cervicornis and Acropora palmata populations and consequent listing as endangered species has prompted the need for restoration. Since financial resources are limited, optimal sites for restoration should not only be environmentally suitable for outplant survival, but also have a greater capacity to replenish surrounding reefs with larvae. However, in Florida coral larval dispersal patterns and reef connectivity remain poorly studied. Here, we measured long term larval survival and competency of A. cervicornis to calibrate a high resolution (100m) biophysical larval dispersal model of Acropora in the Florida Reef Tract (FRT). This model revealed that there is potential connectivity between reefs along the FRT, with most source reefs being located in the southern portion of the reef track, and most sinks in the northern part. The connectivity matrix was used then to develop a metapopulation model accounting for larval dispersal patterns, current and historic habitat for the species, growth, fecundity, and density-dependent post-settlement mortality for A. cervicornis and A. palmata, which allows comparing the capacity of suitable restoration sites to recolonize other reefs through sexual recruitment. Furthermore, it can determine optimal mesoscale spatial scaling and temporal planning of restoration project. We found that there was regional variation in the optimal spatial scaling, due to differences in intra-reginal connectivity and exiting coral cover. We also found that temporally staggering outplanting effort is important in poor environmental conditions. Considering ecological processes in restoration will enhance genetic diversity, hasten coral recovery, and boost resilience across the entire reef system.
2

Tigmomorfogênese na rustificação e sobrevivência em mudas de Pinus taeda L. / Thigmomorphogenesis in the hardening and survival in Pinus taeda L. seedlings

Dranski, João Alexandre Lopes 04 March 2013 (has links)
Made available in DSpace on 2017-07-10T17:40:44Z (GMT). No. of bitstreams: 1 Joao_Alexandre_Lopes_Dranski.pdf: 1387311 bytes, checksum: e0d0c6141cd57f35175f1e8208b56884 (MD5) Previous issue date: 2013-03-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Thigmomorphogenesis is the adopted term to describe the growth response of plants to mechanical stimuli, naturally triggered by abiotic factors or artificially, by agroclimatic adverse event simulation. In the implantation of forest stands, such adversities limit of the seedlings establishment, and condition it to the recognize the limiting factor is the role in the hardening. It is speculated that the thigmomorphogenesis induced by stem bending become's more tolerant by forces exerted by the wind through the activation of mechanisms that alter the growth and accumulation of organic compounds. However, little is known if the employment of mechanical perturbations during seedlings hardening phase results in greater success in the implantation of forest stands. This present work aimed to evaluate morphophysiological alterations in Pinus taeda L. seedlings resulting from thigmomorphogenesis induced and its reflections about establishing in the field. For both, three experiments were conducted with the intention of quantify morphophysiological alterations resulting from stem bending and its reflections about establishing in the field; the partition and the buildup dry weight and carbon; and the correlation between lignin contente with field survival. P. taeda seedlings were produced by the nursery belonging to the company Sbaraini Agropecuária S.A., in Cascavel, PR. When reached the target size, were submitted to different intensities of stem bending during 60 days. At the end, were quantified morphophysiologic attributes, nutritionals, the dry weight and carbon partition between components, and lignin content. Additionally, the seedlings quality was measured by the root electrolyte leakage (REL). Posteriorly, part of the seedlings was planted in a commercial área of Pine monocropping in Cascavel, PR. Was quantitated by the survival, and increases of growth shoot at 90 and 360 days after planting. The increased intensity of the stem bendings reduced linearly of the stem height growth, the leaf area, resulting in the reduction in absolute growth rate and in the phosphorus content. Moderate intensities with up to 20 stem bending increased the secondary growth, the stem volume and the lignin content both in the root system how much aerial. The alteration in the primary and secondary growth was resulting of the carbon redistribution and of the dry weight accumulation in stem and in the root system, mostly in lateral roots, to the detriment of the leaf area reduction in terms of surface and dry matter. On the field, seedlings stimulated with that intensity showed higher survival and growth velocity, observed at 90 days after planting. After this period, he difference in growth velocity between seedlings stimulated or not has reduced, indicating acclimation of the seedlings unstimulated at the environment condition. There was correlation between the lignin content of the root system with the survival percentage at the 90 days, as well as the seedling quality measured by REL test proved to be predictive of field performance. Therefore, the application of 20 stem bendings applied during hardening of the P. taeda seedlings promoted greater success in implanting of the population in the experimental conditions analyzed. / Tigmomorfogênese é o termo adotado para descrever o crescimento dos vegetais em resposta ao estímulo mecânico, desencadeado naturalmente por fatores abióticos ou artificialmente, por simulação de eventos agroclimáticos adversos. Na implantação de povoamentos florestais, tais adversidades limitam o estabelecimento das mudas, e condicioná-las ao reconhecimento do fator limitante é o papel da rustificação. Especula-se que a tigmomorfogênese induzida por flexões caulinares tornam-as mais tolerantes às forças exercidas pelo vento, por meio da ativação de mecanismos que alteram o crescimento e o acúmulo de compostos orgânicos. Contudo, pouco se sabe se o emprego de perturbações mecânicas na fase de rustificação de mudas resulta em maior sucesso na implantação de povoamentos florestais. O presente trabalho objetivou avaliar as alterações morfofisiológicas em mudas de Pinus taeda L. resultantes da tigmomorfogênese induzida e seus reflexos sobre o estabelecimento no campo. Para tanto, três experimentos foram conduzidos com o intuito de: quantificar alterações morfofisiológicas resultantes de flexões caulinares e seus reflexos no desempenho das mudas a campo; a partição e o acúmulo de massa seca e carbono; e a correlação entre o teor de lignina com a sobrevivência no campo. Mudas de P. taeda foram produzidas pelo viveiro pertencente à empresa Sbaraini Agropecuária S.A., no município de Cascavel, PR. Quando atingiram altura maior que 15 cm, foram submetidas a diferentes intensidades de flexões caulinares durante 60 dias. Ao final, foram quantificados atributos morfofisiológicos, nutricionais, a partição de massa seca e carbono entre componentes da parte aérea (acículas, casca e cerne) e radicular (raízes laterais e pivotante), e o teor de lignina nas raízes e na parte aérea. Adicionalmente, a qualidade das mudas foi aferida pelo teste da perda eletrólitos de raízes (PER). Posteriormente, parte das mudas foi plantada em uma área comercial de monocultivo de Pinus em Cascavel, PR. Quantificou-se a sobrevivência, e os incrementos no crescimento aéreo aos 90 e 360 dias após o plantio. O aumento da intensidade de flexões caulinares reduziu linearmente o crescimento em altura, a área foliar, resultando em redução na taxa de crescimento absoluto e no teor de fósforo no sistema radicular e na parte aérea. Intensidades moderadas com até 20 flexões caulinares aumentou o crescimento secundário, o volume do caule e o teor de lignina tanto no sistema radicular quanto na parte aérea. A alteração no crescimento primário e secundário foi resultante da redistribuição de carbono e do acúmulo de massa seca no caule e no sistema radicular, principalmente em raízes laterais, em detrimento a redução de área foliar em termos de superfície e matéria seca. No campo, mudas estimuladas com 20 flexões caulinares externaram maior sobrevivência e velocidade de crescimento, observado aos 90 dias do plantio. Após este período, a diferença na velocidade de crescimento entre mudas estimuladas ou não reduziu, indicando aclimatação das mudas não estimuladas à condição do ambiente. Houve correlação entre o teor de lignina do sistema radicular com a porcentagem de sobrevivência aos 90 dias, assim como a qualidade da muda aferida pelo teste da PER mostrou ser preditivo ao desempenho no campo. Portanto, a aplicação de 20 flexões caulinares aplicadas na fase de rustificação de mudas de P. taeda promoveu maior sucesso na implantação do povoamento
3

Identifying Disease-Resistant and Thermal-Tolerant Genotypes in the Threatened Staghorn Coral, Acropora cervicornis

Hightshoe, Morgan V 27 April 2018 (has links)
Since the 1970s, loss of herbivores, coral bleaching, pollution, and disease epidemics have reshaped the ecological framework of coral reefs. Staghorn coral, Acropora cervicornis, was a major reef-building scleractinian coral found throughout Florida and the Caribbean that experienced unprecedented population declines primarily due to disease and coral bleaching. These two stressors are coupled; the highest coral disease prevalence occurs after periods of thermal stress caused by increased sea surface temperature. Previous research documented three disease-resistant A. cervicornis genotypes in Panama, but it is unknown if disease-resistant genotypes exist in the Florida Keys. Thermal tolerance has been found to be variable among different species of corals and is relatively unknown in A. cervicornis. To investigate disease resistance and thermal tolerance in corals collected from the Florida Keys, pathogen transmission, thermal tolerance experiments, and coral outplanting studies were conducted, along with histological work to assess the condition of coral tissues. Corals were challenged in situ with exposure to rapid tissue loss (RTL) and bleaching resistance was evaluated ex situ in temperature-controlled seawater tanks, using 39 A. cervicornis genotypes. Disease and bleaching were further characterized in the wild using outplanted colonies. In a pathogen transmission pilot study, 7 out of 39 genotypes developed signs of rapid tissue loss transmission. An expanded transmission experiment that used 12 potentially disease resistant genotypes (based on anecdotal information and results from the pilot study), all genotypes developed signs of RTL transmission. However, susceptibility was variable but not statistically different among genotypes (p>0.05), ranging from 40-100% transmission. Histological analyses revealed significant (p0.05) related to photosynthetic efficiency and tissue condition metrics. No significant differences in mortality, disease, or predation were found between disease resistant and disease susceptible genotypes in outplanting experiments (p>0.05). This study reports the first evidence that disease resistance is present in Florida A. cervicornis genotypes. The variability of disease resistance found within genotypes suggests that genotype is not the only factor influencing disease transmission. Short-term exposure to thermal stress revealed heat tolerant A. cervicornis genotypes, which corroborates with recent published studies. Taken together, these results provide insights into how Caribbean Acropora and other scleractinian species persist through multiple disease and coral bleaching events.
4

Ectomycorrhizal communities associated with a Pinus radiata plantation in the North Island, New Zealand

Walbert, Katrin January 2008 (has links)
Aboveground and belowground ectomycorrhizal (ECM) communities associated with different age classes of the exotic plantation species Pinus radiata were investigated over the course of two years in the North Island of New Zealand. ECM species were identified with a combined approach of morphological and molecular (restriction fragment length polymorphism (RFLP) and DNA sequencing) analysis. ECM species richness and diversity of a nursery in Rotorua, and stands of different ages (1, 2, 8, 15 and 26 yrs of age at time of final assessment) in Kaingaroa Forest, were assessed above- and belowground; furthermore, the correlation between the above- and belowground ECM communities was assessed. It was found that the overall and stand specific species richness and diversity of ECM fungi associated with the exotic host tree in New Zealand were low compared to similar forests in the Northern Hemisphere but similar to other exotic plantations in the Southern Hemisphere. Over the course of this study, 18 ECM species were observed aboveground and 19 ECM species belowground. With the aid of molecular analysis the identities of Laccaria proxima and Inocybe sindonia were clarified. In the aboveground study, five species were found associated with P. radiata that were previously not reported with this host in New Zealand (Inocybe sindonia, Lactarius rufus, Lycoperdon gunii, Rhizopogon pseudoroseolus and Wilcoxina mikolae). Belowground, the species Psudotomentella sp., P. tristis, R. luteorubescens, Tomentella sp., Wilcoxina mikolae were found as new associates of P. radiata in New Zealand, additionally nine ECM types were found that could not be identified with molecular analysis. There was little correlation between the species fruiting and the species colonising root tips. Only seven species were found in common between the above- and belowground communities, furthermore the dominant species aboveground were not observed in the belowground ECM communities. The influence of host age on the above- and belowground ECM communities of different age classes of P. radiata plantations was investigated. The aboveground species richness increased from the nursery to the oldest age group investigated (26 yrs), while diversity increased to the 15 yr old age group and decreased slightly to the oldest stand. A clear sequence of ECM species changes was observed to be related to stand age with a growing complexity over the chronosequence. The belowground ECM communities showed a different picture and richness and diversity initially decreased from the nursery to the outplanting but increased thereafter. Belowground no change in ECM composition that was directly related to the age of the host was observed, but two distinct groups of ECM species were found – a 'young' and a 'plantation forest' group, with the respective discriminating species being Rhizopogon rubescens and Type unknown Basidiomycete/Amanita muscaria. Another aspect of the study was the fate of the nursery ECM species in the outplanting and the arrival of non-nursery species. The ECM communities of seedlings in the nursery were investigated in 2006 and these seedlings were followed up over eight assessments in the field for one year, furthermore data from the 1-, 2 and 8 yr old plantation stands was analysed. It was found that the nursery species do survive the first year of outplanting and are dominant in the first year. The first non-nursery species occurred six months after outplanting but was only in minor abundance. Nursery ECM were dominant for two years after the seedlings were planted, and were completely replaced after seven years. Rhizopogon rubescens was found to be the most persistent and dominant species in the outplanting, facilitating the successful establishment of the seedlings in the plantation forest.

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