Primary succession on the basaltic lava flows of Mt. Etna was studied usmg chronosequence theory to investigate the first 500 years of ecosystem development. Separate experiments were conducted to look at how plant species, nutrient availability and lichen activity on the lava changed over time under different conditions based on the site location (age, aspect and altitude on the volcano). By comparing the results of these different areas of study, close links were observed between soil development and nutrient availability. Lichens were found to be an important stage in primary succession introducing biomass to form a developing soil as well as weathering the lava surface. The plant species present on the lava were found to change as plants first colonised the lava and were then replaced as further species appeared over time. Nutrient availability was investigated in living plant material by measurement of the enzyme nitrate reductase and also in the developing soil. Two large inputs of nitrogen were observed in the chronosequences. An early input believed to be lichen derived and another steadily increasing input associated with the soil. The biomass of the nitrogen fixing lichen Stereocaulofl vesuvianum on the lava flows was found to change over time with a rapid increase over the first 100 years of the chronosequence followed by a slower decline as competition and shading from vascular plants covered available habitat. S. vesuvianum was also found to be an efficient weathering agent on the lava altering the surface morphology. This weathering was observed qualitatively by detailed visual examination of the lava surface by scanning electron microscopy. Weathering was also measured quantitatively using an intelligent machine vision computer system, to collate the surface changes of many images simultaneously and compare surface change to a baseline chronosequence, allowing discrimination of fine differences in the extent of weathering. Two of the experiments conducted on Mt. Etna (nitrate reductase activity and lichen weathering) were repeated on a second volcano, Mauna Loa (Hawaii). This tested if the trends observed on Etna were typical of primary succession on lava and the impact of a different climate regime (tropical) compared to Etna (temperate). Nitrate reductase activity was found to be very low in the primary colonising species studied on Hawaii indicating that nitrogen is limited on the early lava flows. Lichen weathering by Stereocaulon vulcani on Hawaii was found to occur in a comparable manner to S. vesuvianum on Etna, and was similarly controlled by the lichen biomass and associated climatic conditions.

No description available.

Studies of the evolution of hotspot swells, mantle plumes, and Hawaiian basalts are presented in three parts in this dissertation. In part 1, the evolution of mid-plate hotspot swells are simulated numerically as an oceanic plate rides over a hot, upwelling mantle plume. The transient heat transfer equations, with time- and space-dependent boundary conditions, are solved in cylindrical coordinates. Geophysical data are used to constrain the models. Formation of the Hawaiian swell requires a mechanism of convective thinning of the lithosphere. The models constrain the Hawaiian heat source to have a maximum anomalous temperature of 250-300°C, and a perturbing heat flux 5-6 times the background value. On the other hand, the Bermuda swell is likely produced by heat conduction due to weakness of the heat source. In part 2, an analytic model of axisymmetric mantle plumes is presented. Plume parameters beneath the lithosphere, which are constrained from the swell models, are used to infer the plume source regions. The Hawaiian plume likely originates near the core-mantle boundary, but other hotspots may have shallower sources. Chemical plumes are much narrower than thermal plumes because of low chemical diffusivity in the mantle. For mantle plumes driven by combined thermal-chemical diffusion, the chemical signature of the source regions may only be observed near plume centers. Finally, melt generation and extraction along the Hawaiian volcanic chain are discussed in part 3. As a part of the plate moves over the heat source, melting largely takes place in the region where the lithospheric material is engulfed and swept away by the flow of the heat source. At least three mantle components must be involved in the melt generation: the plume material, the asthenosphere, and the engulfed lithospheric material. Significant amount of melts may also come from direct melting of the upwelling plume at depths below the initial plate-plume boundary. Melt extracts continuously from an active partial melting zone of 10-20 km thick, which moves outward as heating and compaction proceed. The models explain quantitatively the general characteristics of Hawaiian volcanism as the result of plume-plate interaction.

No description available.

By studying volcanoes on Venus, Mark Jellinek is advancing the science of predicting volcanic activity on earth.

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.

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1966. / Bibliography: leaves 156-168. / xiii, 168 l illus. (part mounted), tables

Univ., Diss.--Bremen, 2006.

Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 153-167). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Thesis (M.S.)--Northwest Missouri State University, 2008. / The full text of the thesis is included in the pdf file. Title from title screen of full text.pdf file (viewed on July 25, 2008) Includes bibliographical references.