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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.
321

Disturbance and succession on the Krakatau Islands, Indonesia

Schmitt, Susanne F. January 1997 (has links)
This thesis set out to investigate the influence of disturbance on the succession of the Krakatau islands (Rakata, Sertung, Panjang). The hierarchical model of succession by S. Pickett and colleagues (1987) was adopted as a research framework, and provided the basis for an alternative model of succession on Krakatau that focuses on processes rather than successional pathways. Investigations were conducted on (i) the meso-scale, and (ii) the patch-scale, (i) quantified the recent disturbance regime, and inter- and intra-island differences in diversity, (ii) compared sapling performance (growth, mortality and recruitment), and species compositional patterning in space and time for saplings and the seed bank with respect to island, gap size and severity of disturbance. Multivariate techniques were used, and amongst other attempts at characterising the light environment, hemispherical photography was employed. For the first time the effect of a continuous period of volcanic activity (1992-1995) of Anak Krakatau could be directly quantified and compared between Panjang and Sertung (ash-affected) and Rakata (receiving no ash). Increased rates of gap formation in the volcanically active period in comparison to the previous decade were found for all islands. This supports the disturbance-driven model of Whittaker and colleagues. However, an extension is required, because, contrary to expectation, Rakata also experienced more disturbance. This increase is argued to be a result of more severe weather conditions, and an increased number of earth tremors, during times of volcanic activity. The disturbance factors of extreme climatic events (e.g. ENSO events) and human impact are also proposed for inclusion in the alternative model. Drought associated with the 1994 El Niño is of relevance to short-term and potential long-term impact on regeneration dynamics and succession. Attention was drawn to the local human influence of pumice mining on the coastal forests. Supporting previous findings on the plot- and whole island scales, data from species presence/absence transects established that species richness and beta-diversity on the ash- affected islands was also lower on the meso-scale. Panjang's canopy composition is less uniform, and locally more species-rich than Sertung's. More evidence of the suggested decline of the mono-dominant species Neonauclea calycina and Timonius compressicaulis was gathered. The third dominant, Dysoxylum gaudichaudianum, is expanding in the lowlands of all islands. This is aided by its ability to regenerate in moderate shade, to grow rapidly in gap environments, and its tolerance of ash-fall, drought and herbivory. However, on Rakata, it is not expected to become generally mono-dominant because a considerable number of other potential canopy species are present. Sapling performance and species composition and its changes were in general strongly affected by ash-fall and drought. These factors tended to override effects of gap size and severity of disturbance. Advance regeneration, and the composition of the local forest type were identified as important factors influencing the composition of the early stages of gap-fill. The local forest type also seemed to contribute most to seed bank composition. As rarer species tended to have clumped distributions, and 'safe sites' for regeneration seemed not to be limiting, dispersal constraints were argued to be the most likely factors slowing diversification, unless further severe volcanic disturbance leads to successional set-back. The latter also strongly limits the predictability of succession on Krakatau.
322

Probabilistic cellular automata and competition across tropic levels

Pilling, Mark Andrew January 2001 (has links)
This thesis investigates a resource driven probabilistic cellular automata (PCA) model of plant competition in terms of local interactions, spatial distributions, and invasion. The model also incorporates herbivores and carnivores and examines their effect on plant populations and community structure. Comparisons are drawn between the model, field studies and other mathematical models. Chapter 1 provides a background of relevant concepts from plants and animal ecology, details a number of mathematical models used in this field and describes the model relevant models and results in the literature. It concludes with a comparison of the features of the most germane models and field studies. Chapter 2 primarily focuses on plants, argues for the model we have chosen, recaptures previous results which are similar to some natural phenomena, and makes a preliminary investigation of community behaviour and disturbance. It then describes the effect of introducing biomass for plants on species behaviour, and their spatial distributions. Chapter 3 deals with competition between different species, and aspects of invasion. Coexistence between functionally different plants can occur, join count statistics and measures for patch location on the torus are developed and applied. Chapter 4 derives a generalised probabilistic model for ruderal monocultures, finds numerical solutions for these and investigates models for vegetatively growing species of plants. Chapter 5 examines the population effects of herbivory (i.e. importance of spatial correlation of disturbance) and analogies to competitor-stress tolerator-ruderal (CSR) primary plant types, as well as plant successional rates and factors affecting community composition. Equilibrium species composition corresponded to CSR theory when plant immigration was introduced. Chapter 6 investigates the basic effects of carnivory, and discusses parallels between probabilistic cellular automata and field studies.
323

Modelling early plant primary succession on Mount St. Helens

Marleau, Justin 11 1900 (has links)
Understanding the mechanisms that control the rate and trajectory of primary succession can lead to insights for ecosystem rehabilitation. Proposed mechanisms include life history traits and nutrient limitation. To explore how these mechanisms can drive successional dynamics, I devised a stoichiometric ecosystem-level model that considered the role of nitrogen and phosphorus limitation in plant primary succession in conjunction with life history traits. This model was applied to the plant community on Mount St. Helens to check the validity of the mechanisms. The results show the competitive hierarchy of plants at the local scale can be explained by nutrient limitation and plant stoichiometry. At regional scales, life history traits interact with local processes to shape community structure and successional dynamics. At all scales, the presence of Lupinus lepidus, a nitrogen-fixer, significantly altered community dynamics and succession. This study suggests that primary succession can be examined within the framework of ecological stoichiometry. / Ecology
324

The effects of natural and anthropogenic disturbances on the structure and composition of early-successional plant communities in the Interior Cedar-Hemlock (ICH) zone of southern British Columbia

Corriveau, Brit Madelaine 11 1900 (has links)
Wildfire is the primary natural disturbance in Interior Cedar-Hemlock (ICH) forests, and since the mid-20th century, forest harvesting (clearcutting, in this case) has become the primary anthropogenic disturbance type. Forest management in British Columbia is currently governed by a paradigm that maintains that biological diversity can be preserved by utilizing forest harvesting regimes that closely mimic "natural" disturbance regimes, but a question remains as to how closely these regimes mimic wildfire disturbances. More specifically, how do clearcutting and wildfires compare in their effects on the structure and composition of early-successional ICH plant communities? This study compares vegetation structure, composition, relative abundance and diversity among 39 sites that experienced either a stand-replacing fire or a clearcut within the last 40 years. Sites of different ages and disturbance types were located within the wet cool ICHwkl and very-wet cool ICHvk I biogeoclimatic variants near Revelstoke, B.C. For each site, overstory structural characteristics (tree and snag diameters, basal area and density), overstory composition, and surface fuels (volume of coarse woody debris (CWD)) were assessed. Understory vegetation percent cover, species richness, composition and diversity were also determined. Linear regression analysis was used to examine differences in each of these variables between disturbance types, over time. The trends in structural legacies (especially snag and CWD dynamics) varied greatly between wildfire and clearcut sites. Compared to burned sites, clearcut sites exhibited patterns of accelerated succession in several characteristics (overstory tree regeneration, vegetation cover and understory species richness) due to planting treatments and pre-disturbance relicts. Understory species composition also varied between disturbances, with clearcut sites containing more shade-tolerant survivors initially. Both disturbance types had similar levels of floristic diversity during early succession. These results suggest that clearcut harvesting may not emulate stand-replacing fires in terms of impact on early ICH plant succession in any aspect but diversity. However, it is unclear if these early-successional differences will continue through time. There is a need for further research in this ecosystem, as well as any other ecosystems where emulation silviculture is applied, in order to confirm that silvicultural effects mimic those of natural disturbance regimes.
325

Succession planning for middle managers in US subsidiaries in Hong Kong

Neirynck, Baudouin C R January 2003 (has links)
During the 1990's, most Hong Kong companies experienced extremely high Voluntary Turnover among middle managers. This thesis attempts to find the causes of such turnover through quantitative analysis and at the same time assess the state of Succession Planning implementation in 10 subsidiaries of US multinational companies as a potential remedy to such turnover. Lack of career advancement and promotion opportunities was found by employees to be the leading cause of voluntary turnover whereas employers believe basic salary and other remuneration components are the main causes. In 9 companies out of 10, Succession Planning is found to be short on basic success criteria such as formalization, buget, support from top management, I.T. support, integra- tion with strategic HR planning, accountability and continuous review process / thesis (PhDBusinessandManagement)--University of South Australia, 2003.
326

Administration of foreign estates

Burgin, Edward Leslie January 1913 (has links)
"Thesis approved for the degree of doctor of laws in the University of London." / Includes bibliographical references. - Includes indexes. - RLIN, CTRG97-B383. - Reproduction of original from York University Law School Library pt. I. Estates of deceased British subjects leaving property abroad -- pt. II. Estates of deceased foreigners leaving property within the United Kingdom
327

Using ecological theory to guide the implementation of augmentative restoration

Bard, Erin Christina. January 2004 (has links) (PDF)
Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Roger L. Sheley. Includes bibliographical references.
328

Nitrogen and phosphorus availability, ecosystem processes and plant community dynamics in boreal wetland meadows /

Erickson, Heather E. January 1994 (has links)
Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [110]-119).
329

Predicting late-successional fire refugia from physiography and topography /

Camp, Ann Elizabeth. January 1995 (has links)
Thesis (Ph.D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves [119]-128).
330

Landscape analysis of post-burn succession in a Great Basin pinyon-juniper woodland

Condon, Lea A. January 2007 (has links)
Thesis (M.S.)--University of Nevada, Reno, 2007. / "December 2007." Includes bibliographical references. Online version available on the World Wide Web.

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