Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "May 2007." Includes bibliographical references (p. 239-253). Also available via the World Wide Web.

During a volcanic eruption, the extrusion of lava onto surfaces destroys biological activity creating virgin land surfaces. Through time this new land will be subject to soil formation and colonisation under relatively similar climatic conditions and parent materials. Soils formed from volcanic deposits present a unique opportunity to study microbial community development. Soils at different developmental stages and differing in vegetation cover were selected from four locations on the slopes of Mount Etna, Sicily. Three main research objectives were determined in order to test the hypothesis that the microbial communities from soils at later stages of development would have a greater biomass, be more diverse, be more efficient at utilising carbon sources and recover from an environmental disturbance at a greater rate. A field experiment was conducted to ascertain the long term in situ catabolic abilities of the microbial communities in each soil and to establish the effects of litter mixing on decomposition rate. Litter bags containing either Genista aetnensis (Etnean Broom), Pinus nigra (Corsican Pine) or a mixture of the two were buried at each of the sites and their decomposition monitored over a 2.5 year period. PLFA diversity, community composition and function was assessed for each of the soils. The soils were also subject to a disturbance and the recovery of key community parameters was monitored over a six month period in order to establish each soil community’s resistance and resilience to disturbance. A laboratory experiment was conducted in order to investigate functional diversity and decomposition functions of each soil community using a range of simple and complex substrates. The relationship between PLFA diversity and functional diversity was also investigated. No correlation was found between soil C and N contents, microbial biomass or soil respiration and soil developmental stage and there was no detectable difference in litter bag mass loss between the soil types. No non- additive effects were noted in mixed litters. The more developed soil had a greater PLFA diversity and PLFA biomass however the more developed soil was not more resistant or resilient to disturbance. Developed soils showed greater catabolic diversity compared with less developed soils broadly correlating with PLFA diversity. Despite increased PLFA diversity and functional diversity in the more developed soils, residue decomposition in situ was unaffected. Reduced PLFA diversity and community complexity did not result in reduced function. Soils at different developmental stages had similar catabolic responses and were able to degrade simple and complex substrates to a similar degree. Microbial diversity in soil has the potential to be very high thus resulting in a high rate of functional redundancy i.e. many species within the same community which have the same functional role. It is possible that only a few key functional groups present within the soil community contribute to the main decomposition function within the soil and were able to maintain function during perturbation. Both Etna soils had similar PLFA’s present in similar concentrations and these groups in general were maintained during disturbance. This suggests that total microbial community diversity may not be as important to community function as the presence of key functional groups.

L’objectif général de cette thèse est d’étudier la prise de décision des individus en situation de catastrophe naturelle, en l’occurrence d’origine volcanique, et d’aboutir à des applications possibles, notamment à une amélioration de la prise de décision des populations exposées. Nous nous sommes intéressés à l’incertitude, dimension essentielle des situations de catastrophe naturelle, qui présente un impact important sur les émotions et la prise de décision des individus. D’une part, l’incertitude situationnelle est déterminante quant aux émotions prospectives comme la peur, et, d’autre part, l’incertitude des conséquences influence l’utilisation des heuristiques émotionnelles (émotions comme éléments pertinents à la décision) dans la prise de décision (système 1). Ce travail de thèse a été traité selon trois axes complémentaires. Dans le premier axe, intitulé Incertitude situationnelle, effet de cadrage et prise de décision, nous avons montré que la simple exposition à l’incertitude situationnelle impliquerait une absence d’effet de cadrage, qui, selon les travaux précédents, pourrait provenir d’une augmentation du traitement systématique (système 2), liée au processus de régulation fronto-amygdalienne. Dans le second axe, Incertitude des conséquences, information à la population et prise de décision, nous avons mis en évidence le fait qu’une réduction de l’incertitude des conséquences dans l’information donnée à la population permettait, dans certains cas précis, d’aboutir à de meilleures prises de décision. L’effet obtenu n’a néanmoins été identifié que dans les situations impliquant de fortes émotions anticipatoires (domicile, dilemmes moraux), situations fréquentes au cours des catastrophes naturelles. Enfin, dans le troisième axe, Création d’une base de stimuli pour l’étude du comportement humain face aux risques naturels, nous avons présenté la construction et la validation d’une base d’images liées aux catastrophes naturelles et au volcanisme, nommée « Natural Disasters Picture System » (NDPS). / The overall aim of this thesis is to examine the decision-making of individuals at risk of natural disaster, specifically related to volcanism, and to achieve potential applications, notably to improve the decision-making of individuals at risk. We focused on the uncertainty, an essential aspect of natural disaster events, which greatly impacts individuals’ emotions and decision-making. On the one hand, the situational uncertainty is an essential component for prospective emotions such as fear, and on the other hand, the uncertainty of consequences determines the use of affect heuristics (emotions used as relevant aspects of the decision) in decision-making (system 1). This doctoral thesis followed three complementary axes. In the first axis, namely Situational Uncertainty, Framing Effect and Decision-Making, we exhibited that the mere exposure to situational uncertainty could negate the framing effect, which could be explained, based on previous works, by an increase of systematic processing (system 2), stemming from the processes of the fronto-amygdala regulation. In the second axis, Uncertainty of Consequences, Information to Population and Decision-Making, we have evidenced that a reduction of the uncertainty of consequences applied to the information to population could improve, under certain circumstances, the individuals’ decisions. This effect was only identified in situations of highly charged anticipatory emotions (home environment, moral dilemmas), which are frequently encountered situations during natural disasters. Lastly, in the third axis, Creation of a Stimuli Dataset for the Study of the Human Behavior Facing Natural Hazard, we detailed the conception and validation of an image dataset dedicated to natural disasters and volcanism, named “Natural Disasters Picture System” (NDPS).

Achieving an understanding of the nature of monogenetic volcanic fields depends on identification of the spatial and temporal patterns of volcanism in these fields, and their relationships to structures mapped in the shallow crust and inferred in the deep crust and mantle through interpretation of geochemical, radiometric and geophysical data. We investigate the spatial and temporal distributions of volcanism in the Abu Monogenetic Volcano Group, Southwest Japan. E-W elongated volcano distribution, which is identified by a nonparametric kernel method, is found to be consistent with the spatial extent of P-wave velocity anomalies in the lower crust and upper mantle, supporting the idea that the spatial density map of volcanic vents reflects the geometry of a mantle diapir. Estimated basalt supply to the lower crust is constant. This observation and the spatial distribution of volcanic vents suggest stability of magma productivity and essentially constant two-dimensional size of the source mantle diapir. We mapped conduits, dike segments, and sills in the San Rafael sub-volcanic field, Utah, where the shallowest part of a Pliocene magmatic system is exceptionally well exposed. The distribution of conduits matches the major features of dike distribution, including development of clusters and distribution of outliers. The comparison of San Rafael conduit distribution and the distributions of volcanoes in several recently active volcanic fields supports the use of statistical models, such as nonparametric kernel methods, in probabilistic hazard assessment for distributed volcanism. We developed a new recurrence rate calculation method that uses a Monte Carlo procedure to better reflect and understand the impact of uncertainties of radiometric age determinations on uncertainty of recurrence rate estimates for volcanic activity in the Abu, Yucca Mountain Region, and Izu-Tobu volcanic fields. Results suggest that the recurrence rates of volcanic fields can change by more than one order of magnitude on time scales of several hundred thousand to several million years. This suggests that magma generation rate beneath volcanic fields may change over these time scales. Also, recurrence rate varies more than one order of magnitude between these volcanic fields, consistent with the idea that distributed volcanism may be influenced by both the rate of magma generation and the potential for dike interaction during ascent.

Thesis (Ph. D.)--University of Canterbury, 2007. / Title from PDF title page (viewed on Feb. 23, 2008). Includes bibliographical references (p. 239-253).

Graduation date: 2005