Methylmercury (MeHg) is a potent vertebrate neurotoxin and a contaminant of global concern. Increased anthropogenic emissions of mercury (Hg) to the atmosphere have led to increased bioaccumulation of MeHg in top predatory organisms such as fish, the consumption of which is the main exposure pathway of this toxin to humans and other animals. Forest canopies significantly increase the deposition of Hg in general to watersheds, but sources and fates of MeHg deposition in particular remain poorly understood. In this study, wet and dry loadings of MeHg to a watershed were quantified, and the retention and (photo)reduction of MeHg on foliage were measured using unique stable isotope experiments. We found that traditional methods of quantifying net deposition underestimate incoming sources of MeHg, and that retention of MeHg on forest canopies results in delayed transport of a significant portion of newly deposited MeHg from terrestrial catchments into adjacent lakes. / Ecology

Thesis (PhD)--University of South Australia, 1998

Factors relating to natural regeneration and tree community recovery after slash and burn agricultural practices were investigated in secondary seasonally dry tropical forests (SDTF) of varying land use intensity and post-disturbance management. Patterns and processes of regeneration were explored by collecting community composition data at secondary and primary sites, by conducting seedling experiments, and by investigating existing forest rehabilitation efforts in both Lao PDR (Laos) and Vietnam. In the forests surveyed in Laos, forest recovery in terms of the composition of primary forest tree species juveniles in fallow forests was high at most sites regardless of previous land use intensity. While community compositional studies indicated significant differences between primary and secondary communities, little or no significant differences were found in terms of primary tree species or family diversity, evenness, or dominance of regenerating juveniles. Significant differences appeared to be due to changes in the relative abundances of different species rather than the absence of primary forest obligate species in the secondary communities. This effect is expected to be due to the relatively common resprouting ability of SDTF species, the wide range of ecological conditions that these species can persist under, and the mosaic pattern of land-uses across the landscape. Evidence of environmental filtering affecting composition patterns in secondary communities was found for two plant traits; dispersal syndrome and plasticity of specific leaf area (SLA). Ecological strategies of primary SDTF tree species were investigated in two ways. Within the narrow range of species capable of regenerating within the primary forest environment, evidence of different life history strategies was found, indicated by significant correlations between continuous plant traits of seed size, fruit size, maximum tree height, SLA, leaf size and wood density. The correlations found largely mirrored patterns found in similar studies in Neotropical forests. Evidence of different seedling regeneration strategies was investigated by comparing species of two different successional preference groups in a seedling/light experiment. Seedlings of non-pioneer later successional species responded differently than species more associated with disturbed environments (long-lived pioneers) when exposed to both increasing absolute light treatments, and to light received under various sunfleck treatments. Earlier successional species demonstrated greater plasticity of SLA, leaf area ratio (LAR), stem elongation, and root mass ratio to increasing light. Regeneration under minimally managed monoculture and pair-wise plantations of both native and exotic species at the Laos field site was not significantly different when compared with nearby remnant primary forest in terms of diversity, evenness, and richness. Therefore, plantation overstoreys did not appear to be suppressing the regeneration of primary forest species. Seedlings grown in enrichment designs nearby had survival rates of approximately 50%, and diameter increments of less than 0.2 cm/yr after 6 to 9 years of growth. The performance of seedlings in such plantings is expected to be sufficient for conservation aims but is unlikely to encourage private investment for forestry purposes due to long expected rotation lengths. At Hai Van Pass in central Vietnam, the combination of a fast growing exotic species to capture a degraded site and ameliorate site conditions, followed by enrichment planting of native species was demonstrated to be a successful approach to reforesting degraded land, whilst funding itself through the sale of timber. The results indicate the high regeneration potential of the studied secondary forests, both in terms of observed patterns of regeneration in slash and burn fallow forests, and in terms of the general regenerative abilities of SDTF species. Decisions regarding future land-uses and secondary forest management should have consideration of this possible high level of recovery, and simple diversity sampling techniques should be included in any related processes to confirm the regeneration potential of a particular secondary forest.

Thesis (PhD)--University of South Australia, 1998

The Devonian Taylor Group, in the Olympus Range area, southern Victoria Land (SVL), Antarctica, is separated from the basement by a regional nonconformity (Kukri Erosion Surface). A second localized unconformity within the Taylor Group called the Heimdall Erosion Surface separates the New Mountain Sandstone and older units from the younger Altar Mountain Formation. The depositional environment of the New Mountain Sandstone has long been under contention. The New Mountain Sandstone Formation is a predominantly quartzose cross-bedded sandstone. Its newly defined Mt Jason Member is a coarse arkosic small scale cross-bedded pebbly sandstone that grades up section into the rest of the quartzose New Mountain Sandstone with large scale cross beds. The New Mountain Sandstone has been divided into five lithofacies including the Basal Conglomerate Lithofacies, Pebbly Sandstone Lithofacies, Granule Cross-bedded Lithofacies, Pinstripe Cross-bedded Lithofacies and Cross-bedded Sandstone Lithofacies. Deposition was in a shoreface environment with minor coastal aeolian deposition. The environment changed from upper shoreface to lower shoreface up section, forming transgressive to highstand systems tracts. The Heimdall Erosion Surface truncates the Cross-bedded Sandstone Lithofacies and the Pinstripe Cross-bedded Lithofacies and was formed due to relative sea level fall leading to exposure and erosion of underlying sedimentary and basement rocks. It forms a type 1 sequence boundary. The New Mountain Sandstone was partially or totally lithified before erosion as shown by the jagged morphology of the eroded cross beds on the surface. It is not known when cementation of the NMS took place or how much of the formation has been eroded. The Heimdall Erosion Surface and Kukri Erosion Surface converge locally due to erosion on the Heimdall Erosion Surface and relief on the Kukri Erosion Surface. The Heimdall Erosion Surface became a shore platform and the site of deposition as relative sea level rose. The Altar Mountain Formation with its Odin Member is a cross-bedded, massive and bedded feldspathic and quartzose sandstone that fines up section and is deposited on the erosion surface. The Altar Mountain Formation is divided into four lithofacies including the Conglomerate Lithofacies, Trough Cross-bedded Lithofacies, Cross-bedded Bioturbated Lithofacies and Bedded Fine Lithofacies. Deposition was in a shoreface environment, changing up section to an inner shelf environment with minor estuarine/tidal influence near the top of the section forming transgressive to highstand to regressive system tracts. The sedimentary rocks are derived mainly from the Granite Harbour Intrusives and Koettlitz Group, which underlie the sandstones, but were exposed elsewhere in SVL. The sandstone clasts within the Conglomerate Lithofacies could be derived from underlying older Taylor Group rocks or exotic sources from outside the field area. Correlation with data from adjacent areas suggests deposition of the New Mountain Sandstone occurred in a shallow sea that existed from the Olympus Range, southwards into the Asgard Range and included Vashka Crag. The area around Sponsors Peak and to the north was exposed and supplying feldspathic and quartzose sediment and pebbles into the depositional basin. As relative sea level fell due to either tectonic uplift or eustatic processes a large area of southern Victoria Land was exposed including the Olympus and Asgard Ranges and Bull Pass-St Johns Range area. This lead to erosion of the New Mountain Formation and basement rocks. Deposition of the New Mountain Sandstone continued further south shown by the gradational contact between it and the overlying Altar Mountain Formation. Relative sea level rise led to deposition of the Altar Mountain Formation. Shallow seas once more dominated the southern Victoria Land with deltas in the east (in the Bull Pass-St Johns Range area) feeding feldspathic sediment into the depositional basin (Odin Member). Further sea level rise drowned the delta region and a shallow marine to inner shelf environment led to deposition of the rest of the Altar Mountain Formation.

Thesis (Ph.D.) -- University of Western Sydney, 2001. / "A thesis submitted for the degree of Doctor of Philosophy" Bibliography : leaves 187-217.

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 1999. / Thesis submitted for the degree of doctor of philosophy. Includes bibliographical references (leaves 341-369).

Thesis--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (p.107-118).

Thesis (M.S.)--Brigham Young University. Dept. of Geography. / Bibliography: leaves 55-57.

Thesis (Ph.D.)--University of Alberta, 1997. / Submitted to the Faculty of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Doctor of Philosophy, Department of Anthropology. Also available online.