Science Collected Works - Theses
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ItemSevere weather forecasting in coastal East Antarctica(University of Melbourne, 1999)
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ItemFire and soil interactions in a Mallee heathland : the generation of heterogeneity in an homogeneous landscape(University of Melbourne, 1999)The soils of Australian heathlands are considered to be markedly nutrient-deficient, with some of the lowest concentrations of nitrogen, phosphorus and other essential nutrients ever recorded. The flora is strongly adapted to nutrient conservation and efficiency of use. Yet these same heathlands are often subject to invasion by tall woody shrubs that eventually come to dominance, at the expense of the presumably �better-adapted� typical heathland species. In an attempt to understand and characterize this change in dominance and species composition, the changes in soil nutrient supply and storage were tracked thru a semi-arid heathland in north-western Victoria. Different species used the available nutrients differently, and their impacts on the soil nutrient pool varied with size and age. Some (such as the dominant Casuarina pusilla) augmented the meagre soil nitrogen supply by nitrogen fixation, particularly when younger. Such fixation decreased or even disappeared as the shrubs aged (�senesced�). In August-September 1992 the �available� ammonium concentration in soil from under C. pusilla canopies (at 4.4 ppm) was over double that from under canopies of Callitris verrucosa (at 1.7 ppm) or from the inter-canopy gaps (1.4 ppm). Available ammonium also varied seasonally (with peaks in the moist soils of early spring, August-September, and troughs in desiccated soils early in autumn, April-May), and with stand age. Vigorous N fixation of young C. pusilla and others contributed to relatively high soil ammonium concentrations in 11-year old regrowth when compared with much lower concentrations in 34-year old regrowth, or older. Other species, notably the deep-rooted C. verrucosa, added to the low capital of circulating phosphorus by accessing supplies deep in the profile and bringing some of this to the surface. The litter of some species was richer in these limiting nutrients than the litter of others - again affecting the nutrient return to the surface soil pool and differential accumulation of nutrients under different species. In particular, long-term nutrient enrichment in surface soils enabled annuals formerly absent from these heathlands to establish and grow, in very old stands only (at least greater than 35 years post-fire). Individual species characteristics affected nutrient use and supply to the soils. The markedly sclerophyllous and nutrient deficient leaf litter from Banksia ornata added little of these nutrient s to the soil in the first few years after fire, in contrast with the nitrogen-rich litter from Casuarina pusilla. There was a post-fire flush of nutrients to the surface soil - assisting regrowth and establishment of seedlings. Nitrogen availability and transformations in the soil soon returned to the pre-bum situation, probably within a year. However, the increased soil concentrations of mineral phosphorus immediately after fire, declined much sooner and there was evidence of a subsequent decline in phosphorus availability, to significantly below that of soils in unburnt heathland. The soil nutrient availability in the community is characterized by relative stasis punctuated by short-term flushes deriving from rainfall events, seasonal changes in ambient temperature and occasional fires. Variability in nutrient availability also has a spatial component, deriving from the different architecture, tissue nutrient concentrations, growth stage and internal recycling capacities of the various dominant species present. The landscape was apparently remarkably uniform. Nevertheless, significant habitat heterogeneity was generated by these differences in nutrient use. There was a variety of regeneration strategies adopted by the component species. Some regenerated successfully in the absence of fire - some by seed and others by vegetative means. Small epacrids and myrtles (such as Astroloma and Brachyloma, Baeckea and Calytrix) successfully established from seed in unburnt heathland. Regeneration of many other shrubs and sclerophyllous monocots appeared to require fire and they were unable to regenerate successfully without the opportunities presented by the post-fire environment. The regeneration strategies adopted by four prominent dominants, Banksia ornata, Callitris verrucosa, Casuarina pusilla and Hakea mitchellii (all serotinous shrubs) were investigated. In spite of this apparent similarity, each had a unique response to fire and the opportunities it provided for seed regeneration. The variability of growth and nutrient responses of the many component species, and their interactive effects with the habitat, produced a far more heterogeneous landscape than might have been expected from the remarkably uniform soils and landscape profile. This heterogeneity enabled many species to co-exist, each exploiting a particular, site- specific combination of features and, in turn, producing a site-specific (even �unique�) set of habitat features. The biological components of the ecosystem generated habitat heterogeneity, permitting many species to co-exist. In return, this biodiversity enabled further micro-habitat specialization and habitat heterogeneity. The heathlands did not reach a �steady state� or climax, but continued to change in the continued absence of fire. Species gradually disappeared from the community (either �retreated� to the soil seed bank or truly disappeared as the few remnant adults, with their elevated seed bank, died without replacement). Other species entered the community as the formerly subordinate and then co-dominant C. verrucosa assumed complete dominance - mimicking the invasion and establishment of woody shrubs in heathlands elsewhere. By this stage, the successional change was irreversible. Whether the change is described as �senescence� or �maturation� is subjective. It depends on the perceptions of the particular observer. Although land management has recently come to recognize the importance of heterogeneity in biodiversity maintenance, it has traditionally had difficulty with managing for heterogeneity in time and space. The problems of managing for habitat heterogeneity are considered and a practical conceptual context is provided for future land management.
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ItemSilurian trilobites of central Victoria(University of Melbourne, 1996)
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ItemTerritorial behaviour and mating success in male New Zealand fur seals, Arctocephalus Forsteri(University of Melbourne, 1997)Fur seals are polygynous marine mammals that breed in high densities in terrestrial colonies. Female fur seals deliver and nurse their pups within the breeding colony and male fur seals fight vigorously to acquire and defend territories in the areas of breeding colony that are used by females. The breeding season is extended over 6-8 weeks and some males retain a territory within the breeding colony throughout the season, during which time they fast. Male fur seals are thought to have highly variable reproductive success relative to that of females; some males mate up to 30 times within one season and may hold a territory for several seasons, while others never mate. In contrast, females may produce a maximum of approximately 20 offspring in their lifetime. The factors underlying the mating success of adult male New Zealand fur seals, Arctocephalus forsteri, were examined at Cape Gantheaume, Kangaroo Island, South Australia. Individually marked adult male fur seals were observed whilst ashore during three annual breeding seasons and during the intervening non-breeding seasons. The territorial behaviour and mating success of individually marked adult male fur seals were measured over three successive breeding seasons (1992-1994) and terrestrial behaviour was also measured during the intervening non-breeding seasons. Data on morphology and age were also collected for each male. Larger males gained territories during the breeding seasons and male mass correlated with the duration of territorial tenure, but mass was not correlated with mating frequency among males that mated within their territories. The maximum mass of adult males was 160 kg. The age range of adult male seals was 7 - 15 years. The males that held territories following the birth of the first pup were older than the males that did not, but age was only correlated with mating success in one of the three breeding seasons. The youngest of these males was eight years old. All of the marked males visited the colony outside the breeding season. Some males simply hauled-out in the haul-out areas of the colony while some visited the territories that they had held during the previous breeding season that were within the sections of the colony used by females and pups (breeding areas). The males that visited their territories spent more time in social behaviour than those that were in the haul-out areas and also tended to spend less time resting. The behaviour of these males was also compared to that in their territories during the breeding season: outside the breeding season they spent more time resting overall but were significantly more alert during the mornings than they were during the breeding season. Males were more reluctant to leave their territories when threatened than they were to leave the haul-out areas. The terrestrial behaviour of males outside the breeding season was associated with mating success because males that visited their territories in the non-breeding season were more likely to hold a territory the following season than those that did not.
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ItemThe importance of Tetrarrhena juncea R. Br. in the ecology of Eucalyptus regnans stands in Sherbrooke Forest Park(University of Melbourne, 1985)The native, climbing grass Tetrarrhena juncea (forest wiregrass) exhibits unusually prolific growth in Sherbrooke Forest Park. The distribution and abundance of this species within stands of Eucalyptus regnans and related forest types was investigated in relation to the range of vegetation in order to elucidate factors responsible for this prolific growth. Computer based techniques of pattern analysis were used to describe and compare the range of variation in vegetation floristics and structure, and in environmental features within the E. regnans and related forest types, for an area of approximately 290 ha located in the western section of the park. The major themes of variation in the vegetation parallel a suite of environmental changes. These are the maturity of the E. regnans over storey, an underlying topographical moisture gradient and the levels of light which are likely to penetrate to the forest floor. The fire history of the area is such that the majority of sites may be arranged along a multivariate environmental gradient. Mature forests, with dense small tree strata generally occur in the wetter sites, while younger (spar) forests with less dense small tree strata occur in drier areas. However, a small proportion of spar stands are associated with riparian environments. Changes in the abundance of T. juncea parallel the multivariate environmental gradient; this species is least abundant in moist sites dominated by mature E. regnans and most abundant in the drier sites where spar-aged stands predominate. Whilst the environmental pattern present is characterised by a suite of characters, the majority of the variation (91%) in the cover of T. juncea within the study area may be accounted for in terms of the level of light which penetrates the combined cover of the small tree stratum and the ground fern Polystichum proliferum. The activity of lyrebirds and wombats was investigated in relation to the cover of T. juncea. Dense cover of T. juncea excludes lyrebirds from feeding in certain areas, but provides an important food source for a small population of wombats. Field trials showed that grazing by wombats has potentially damaging effects upon the structure and regenerative capacity of dense swards, suggesting that recurrent grazing is likely to limit sward formation. However, the wombat population was shown to be small and the effects of their grazing to be localised. The development of the dense swards in Sherbrooke Forest Park is discussed in relation to the likely effects of grazing upon the post-wildfire development of vegetation in even-aged stands of E. regnans and the increasing pressures of urbanisation of the Dandenong Ranges during the post-war period.
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ItemMean curvature evolution of graphs in Riemannian manifolds(University of Melbourne, 1999)
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ItemX-ray optics using capillary arrays(University of Melbourne, 1992)
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ItemIdentification and characterization of a style specific glycoprotein from Nicotiana alata Link et Otto(University of Melbourne, 1988)Monoclonal antibodies were raised to an extract from Nicotiana alata Link et Otto (genotype S1S3) styles. The cell lines which produced antibodies that bound to N. alata style extracts but which did not recognize AGPs were partially characterized and one cell line was chosen for further study. This cell line (cell line 58 (766)) secreted an antibody which specifically bound to a major style glycoprotein (120 kD). The antibody was directed to the carbohydrate moiety of the glycoprotein; binding between the antibody and style extract was preferentially inhibited by ?-D- Galp-(l?6)-D-Gal. The N. alata style component that bound the monoclonal antibody 58 (766) is style specific, but does not segregate with self-incompatibility genotype. It is localized in the extracellular matrix of the style and is concentrated in the top section of the style. The concentration of the 120 kD component is developmentally regulated, increasing with maturation of the style. A polyclonal antiserum raised to a commercial preparation of Solanum tuberosum (potato) tuber, lectin also binds to the 120 kD component and the possibility that the 120 kD component is a lectin was investigated. Although style extracts contained no haemagglutinating activity and the 120 kD component did not bind to either fetuin or chitin oligomers, the strong cross-reactivity between the anti-potato lectin antibody and the 120 kD component indicates at least partial structural homology. Approaches were also made to purify the 120 kD component. This component can be substantially purified using a combination of (NH4)2SO4 precipitation, and hydroxylapatite and immunoaffinity chromatography. The final preparation does not contain contaminating proteins or AGPs. However, the yield using this procedure is low and hence, other purification techniques were also investigated. Preliminary amino acid data has been obtained from material which was electroeluted from a SDS-polyacrylamide gel. The 120 kD component has a relatively high concentration of glycine, alanine, 1/2-cysteine and methionine, and a low amount of hydroxyproline and the basic amino acids, lysine, arginine and histidine. Finally, an algal biliprotein from the cryptomonad, Proteomonas sulcata was isolated and partially characterized. The purified pigment has a single absorption peak at 549 nm with a slight shoulder at 555 nm and a single fluorescent emission peak at 583 nm. It has two subunits with the apparent molecular weights of 11 kD and 19 kD on SDS-PAGE. This pigment is potentially useful as a fluorescent marker in immunocytochemistry.