Resource Management and Geography - Theses
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ItemA northward shift of the Southern Westerlies during the Antarctic cold reversal: evidence from Tasmania, Australia( 2018)The Southern Hemisphere Westerlies are one of the most important components of the Earth’s climate system: they are the primary driver of Southern Hemisphere climate, they modulate global ocean circulation patterns, and they are a critical natural driver of atmospheric CO2 variation. Despite their clear importance, their dynamics in response to rapid changes in climate boundary conditions are poorly understood. Critical to this lack of understanding is (1) an absence of robust proxy-data from the Australian sector of the Southern Hemisphere, which hampers attempts at predictive modelling, and (2) a lack of consensus within the palaeoclimate literature as to how the Southern Westerlies have responded to past periods of rapid climate change. A case in point is the behaviour of the Southern Westerlies during the Antarctic Cold Reversal (ACR; 14,000 – 13,700 years ago), a millennial-scale climate event that punctuated the termination of the Last Ice Age in the Southern Hemisphere. A thorough understanding of how this critical climate component changed during the ACR is hampered by the only available proxy-dataset from the Australian sector of the Southern Hemisphere, which disagrees with records from other regions, and with the leading conceptual understanding of Southern Westerly dynamics. To address this discord, this thesis sought to reconstruct the dynamics of the Southern Westerlies in the Australian sector by developing two robust terrestrial proxy-datasets from Tasmania, Australia, covering the ACR. The results from this thesis demonstrate that the Southern Westerlies responded to the climatic changes of the ACR as predicted by the leading conceptual understanding of their dynamics, and also revealed that they responded symmetrically across the Southern Hemisphere, coincident with substantial changes in atmospheric CO2 variation. This thesis supports the hypotheses that the Southern Westerlies are the primary determinant of long-term Tasmanian climate variation and are a critical regulator of long-term global atmospheric CO2 variation.
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ItemThe disposal choices for small household electrical appliances in Linfen, China( 2017)There is minimal literature on how small household electronic appliances are being disposed post-consumer use despite the risk of environmental pollution that can arise from the improper disposal of these items. Larger electronic waste items and mobile phones have been more extensively researched and as a result a wider availability of disposal options are available for these items. China imports significant quantities of electronic waste items from around the world while its own large population is rapidly consuming more electronic items every year, which together results in a high rate of small household appliances being disposed that has not yet been investigated. This research thesis investigated how small household electronic waste are being disposed by households in China. Research on small household electronic waste has typically been concerned with the components of sWEEE rather than its disposal. Of the limited disposal studies of these items that have been undertaken in Europe, results show that individuals are most commonly storing the items, disposing of these items in their household general waste bin, or recycling them through collection schemes. Results for mobile phone disposal across Europe, Japan China are similar. Household surveys and semi-structured interviews were used to collect results and assess whether similar disposal trends are being used for small household electrical waste in a small prefectural-level city in China. In particular, the household bin was the most popular disposal choice for all items and irrespective of any age, education, gender or income. Informal collectors and storage in the home were the second and third most popular disposal choices and the use of these alternative disposal streams differed depending on the item. The choice by households to dispose of small household electronic waste in the bin is the result of few disposal choices for households, the cheap retail price of these items, and a lack of information that leads them to choosing the convenient choice of putting the item in their nearest disposal choice which is the household bin. Improvements to recycle small household electronic waste will need to be delivered through amendments to existing government regulation and the introduction of new government recycling schemes.
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ItemEnvironmental determinants influencing woody plant persistence: implications for wetland forest restoration using ‘infill’ planting and ‘cryptic’ planting( 2016)Background: Wetlands around the world are in a state of decline due to various processes that threaten wetland cover, soil and water quality, and hydrological flow. To aid the recovery of these threatened ecosystems, large-scale revegetation programs have been undertaken in south-east Australia. ‘Infill’ planting, planting within canopy gaps, and ‘cryptic’ planting, hiding plants within the outer foliage of unpalatable plants, are two revegetation methods used by land managers, and are based on gap dynamics and plant associational effects respectively. However, little is known about the efficacy of these techniques in wetland forests, particularly with respect to flooding, canopy cover and browsing. Question: This study aims to examine the environmental determinants influencing woody plant persistence at infill and cryptic planted sites, and to more specifically determine the effectiveness of cryptic planting to deter browsing. Location: Wetland forests in Yellingbo Nature Conservation Reserve (Victoria, Australia) Methods: To examine environmental determinants, I surveyed 352 two-year-old revegetated plants consisting of Eucalyptus camphora, Melaleuca squarrosa, and Leptospermum lanigerum, across three wetland forest sites in flooded and non-flooded areas. For each surveyed plant, the percentage of canopy cover, presence of flooding, whether the plant was cryptically planted or not, plant height and browsing damage were recorded. To further assess cryptic planting, a trial was established whereby 144 six-month-old tubestock of the same three species were cryptically and non-cryptically planted at the same sites and left for four weeks before being scored for browsing damage. Results: Survey results showed that flooding increased L. lanigerum plant height; cryptic planting increased M. squarrosa plant height and decreased browsing damage, and the interaction between cryptic planting and flooding influenced E. camphora plant height. E. camphora plants were particularly vulnerable to browsing damage, experiencing a mean 77% biomass loss across all surveyed sites. Overall, canopy cover had a weak influence on plant height and browsing damage. Furthermore, the results of the trial showed that cryptic planting reduced browsing of woody plants by 33% for E. camphora, 20% for L. lanigerum, and 12% for M. squarrosa. Conclusions: Various environmental determinants influence the plant height and browsing damage to woody species at infill and cryptically planted sites in wetland forests, with browsing appearing to be a key underlying determinant of plant persistence, particularly for the highly palatable E. camphora. The results of the trial suggest that cryptic planting can be used to reduce, but not prevent the browsing of revegetated plants. However, the suitability of these methods at a site needs to be carefully evaluated before they are implemented, especially in areas of severe browsing. Overall, the knowledge from this study improves our understanding of factors that influence the persistence of revegetated plants in wetland forests, provides support for plant associational defence, as well as evidence for land managers on the effectiveness of these revegetation methods.
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ItemSpatial distribution and scaling of avulsions on the King and Ovens River, Victoria, Australia( 2015)Anabranching is a multi-channel river system identified by in-stream vegetated islands or stable alluvial sediment. Avulsions require the abandonment of a river course in favour of a new, more efficient path, generally on the lowest point on the flood plain. Two styles of avulsions exist, progradational and incisional with the former requiring significant flood plain deposition (usually crevasse splays). The Ovens and King River of Northeast Victoria display characteristics of incisional avulsions which need overbank flooding to scour a new channel through surrounding flood plain. The study area of this paper provides a region, unaltered by human interference, to measure all avulsions and their relative distance downstream, an angle which previous literature has not taken up as yet. Results of longitudinal slope, stream discharge, relative flood plain height and sinuosity were based on analysing LiDAR data. Avulsion lengths and distance downstream showed very little correlation (R=2%) and although maximum lengths of avulsions showed greater correlation (R=54%) it still was not strong. Longitudinal slope decreased rapidly from -1.50 m/km to -0.29 m/km after approximately 70 km which correlated to the plateauing for maximum length avulsions. Although shear stress was not measured in this study, its ability to induce knickpoint migration is greater in lower slope regions, providing potential for longer avulsions. Valley-lengths of avulsions also exhibited similar patterns between the Ovens and the King with maximum in lengths at approximately 55 km, which correlated to a plateau in valley-length longitudinal slope. In conclusion, longitudinal slope was the main factor affecting avulsion length. Sinuosity of the Ovens River increased (1.34 to 1.65) whilst avulsion sinuosity decreased suggesting the current channel may avulse to new courses, or existing paleo-channels. The presence of paleo-channels on the wide expanse of flood plain of the lower regions, have a high tendency to attract flow into old conduits instead of scouring new channels for avulsions. Therefore, likelihood is high of reoccupation for avulsions along the Ovens River approximately from Wangaratta preventing the creation of long, whole-system avulsions. Finally, scale invariance of this study can be applied to expectations of avulsion lengths in other anabranching systems which must be considered for town-planning and risk-management. Therefore, providing the tools for predicting avulsions are necessary for future systems.