Resource Management and Geography - Theses
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ItemHow does deforestation affect the functional links between riparian zones and stream channels?( 2018)Riparian vegetation is essential for headwater streams, as it regulates allochthonous inputs of coarse particulate organic matter (CPOM) delivered into streams. CPOM accumulates in patches across the streambed, these patches are sources of energy and shelter where ecological linkages between aquatic populations occur. This group of studies evaluate such relationships in Hughes Creek, Victoria, southern Australia. The first of these studies evaluates the evidence documented in 45 studies which were undertaken mostly in temperate or subtropical regions of the U.S.A., Canada, Spain and Australia. The main focus of these works was to evaluate the effect of deforestation upon allochthonous inputs of CPOM, often in first and second order streams. Most studies addressed airborne inputs only, while lateral surface inputs, or downstream transport of CPOM were not commonly studied. Hedges’ effect size (g) was calculated for allochthonous inputs data from the 45 articles and plotted against deforestation. A threshold for airborne inputs and benthic organic matter (BOM) standing stock was observed when deforestation reached 70%. At that level of deforestation, effect sizes decreased by up to -5 standard deviations. The second study encompassed a field survey where forested and low forested sites along the one stream were evaluated. The survey required the collection of allochthonous inputs monthly for one year, where airborne, lateral surface transfer (LST), and drifting CPOM fractions were collected in sites with contrasting forest cover. Sites with intact vegetation showed high inputs (14 kg m-2 DW year-1), while deforested reaches showed lower airborne inputs (9.25 kg m-2 DW year-1). LST inputs represented 42% of allochthonous inputs in forested reaches, and 37.5% in deforested sites. The transport of CPOM downstream was similar between forested and deforested sites (23-25 kg DW year-1). Given this similarity in CPOM transportation, and that the majority of streams in Victoria are deforested, patches of riparian forest might be an attractive management option for restoration/management of streams. However, it is necessary to be mindful of the scope and limitations of forested patches along streams, as they might not provide resources to neighbouring areas. Rather, forested sections tend to retain most of their allochthonous inputs within their boundaries. The third study of this thesis comprises a field survey where patches of CPOM, located on the streambed of forested and deforested reaches, were collected in Summer, Spring and Winter. CPOM was separated intro fractions of leaves, bark and twigs. It was found that the type of cover did not modify the mass of CPOM fractions between forested and deforested reaches (p > 0.05). However, the results show significant differences between Sites within Forest Cover for all fractions, with exception of leaf material. The dominant patterns suggest high variation between sites and shifts between seasons. In relation to the contribution of each fraction provided to CPOM benthic standing stock, it was found that during the three sampling seasons, benthic CPOM composition was dominated by, in decreasing order, twigs, bark, leaf, and grass. Additionally, macroinvertebrates found in CPOM patches were separated and sorted into genus and species when possible. The analysis of species densities between forested and deforested sites show that Simulium ornatipes and Ecnomina F sp. densities differed between the two types of forest cover, while the remaining species showed no differences. However, Simulium ornatipes showed strong differences between sites. Ecnomina F sp. was the only taxon to show a significant difference related to forest cover, without having a substantial difference between sites within the same forest cover. On the other hand, Ecnomus continentalis, Notalina sp., Chemautopsyche sp, Hydroptila, Berosus (larvae), and Micronecta sp. showed higher significant differences in summer; whereas Chemautopsyche sp. and Hydroptila sp. densities were minimal in patches during spring. The regressions between the mass of CPOM and density of species showed that some presented negative relationships between specimens’ density and the increase of CPOM mass, as illustrated by Ecnomia F sp., Cheumatopsyche sp., and Nousia sp. The last study of this thesis was a field experiment where the size and spatial distribution of CPOM patches was manipulated, due to small-scale fragmentation being predicted to affect species densities, particularly where patches are ephemeral or organisms are transported advectively. CPOM patches were deployed in two possible configurations (a) one big patch treatment (BPT), comprised of 12 smaller sub-patches of the same size, and (b) 12 split patches (SPT), which were distributed across the streambed. Patches from the split treatment were of two sizes, double (300 cm2) and single (150 cm2). BPT and SPT patches from both treatments were oriented randomly on the stream (parallel or perpendicular) with respect to water flow. After 10 days, samples were collected of 13 common macroinvertebrates which had colonised the patches. It was found that the genera Offadens spp. and Notriolus spp. had responded to the orientation of patches in both treatments. Moreover, in SPT sites Offadens spp., Cheumatopsyche spp., and Notriolus spp. showed significantly higher densities in small patches, suggesting that species densities, which show no searching strategies for resources, are likely to be affected by patch size. The knowledge generated in this thesis provides a greater understanding of the effect upon macroinvertebrates densities by deforestation of a creek that flows through agricultural lands in southern Australian.
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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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ItemFloodplain avulsion channels: understanding their distribution and how they reconnect to the parent channel( 2018)This study is concerned with new river channels that develop on floodplains. These channels can develop gradually, or they can develop more rapidly (avulsions). This study concentrates on the relatively more rapid channel changes known as avulsions. An avulsion specifies the gradual abandonment of an existing river-channel and in response to this, the processes of development of a new channel on a floodplain nearby. The study addresses two specific knowledge gaps: 1) how common are river floodplain avulsions globally, and 2) what are the detailed processes that occur at the up and downstream points where avulsions connect to the main channel? Using random sampling from a global spatial layer I discovered that developing avulsions are extremely common on alluvial floodplains globally, wherever the floodplain is wider than several channel widths. Avulsions are most common on single thread meandering floodplain types, but a review of avulsion literature shows that research is biased to relatively less common floodplain types. Avulsions increase the rate of valley widening, particularly in narrow floodplains. There is a relationship between floodplain width and the number of avulsion channels. The rest of the thesis is focussed in the major process knowledge gap which is how avulsion channels connect into the main channel at the up and downstream ends. The focus of the process component of this study is the broad Murray river floodplain from Yarrawonga to Echuca, SE Australia. I mapped and classified developing channels on the floodplain and found that the avulsion connection point here develops in an unusual way, involving the development and coalescence of low points (depressions) on the levee (this mechanism is very different from normal crevasse splay development). The chain of low points on the alluvial levee coalesce to form a levee channel. Rather than forming by erosion as expected from the literature, form progressively by locally reduced vertical accretion. This identifies a new process by which topography is developed on floodplains. Initially the levee channels are not connected with the Murray main stream and slope away from the river. The connection occurs by lateral migration of the river bank into the levee channel, but also by progressive upslope (river ward) migration of the deepest part of the levee channel towards the river, narrowing the gap between the river and the levee channel. Following connection, the levee channel captures flow from the river, and hydraulic modelling shows that shear stress is sufficient to erode the upstream end of the levee channel. As the channel erodes the shear stress declines, but the proportion of back-flow from the flood recession increases. The result is that the slope of the levee channel reverses to slope towards the river. This is a new mechanism, and it is critical in the sequence of avulsion development. The final stage of the development of avulsion is when a knickzone moves up the levee channel joining another levee channel that is leaving the river upvalley. This is new mechanism of avulsion likely to operate in low energy river systems dominated by fine-grained sediments.
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ItemJust adaptation at resource frontiers: climate and empowerment in post-Soviet northern Russia( 2018)Despite an emerging interest in integrating climate policy and development goals, little is known about the potential synergies and trade-offs in resource extraction regions, particularly for Indigenous and rural communities that host resource projects. This thesis explores the institutional and political context in two resource extraction regions that shape resource development and climate change outcomes and mediate planning and implementation of initiatives to support adaptation decisions. The aim of the thesis is to identify the potential of climate change adaptation to contribute to the development of more equitable outcomes and processes for host communities. I present a conceptual framework called ‘just adaptation at resource frontiers’ that seeks to explicate the cross-scale political economy and ecological forces acting in the context of a changing global economy and climate change. The framework is applied and refined based on an empirical study, using interviews, purposive observations, focus groups and document analysis, in four cases in the Republic of Komi and the Republic of Sakha in Arctic and sub-Arctic Russia. Here, Indigenous subsistence-based and rural livelihoods face 'double exposure' to expanding oil exploitation and the impacts of climate change. Host communities bear the impacts inequitably, and they lack recognition of their rights and effective participation in governance. Despite different contexts between case study communities in Komi and Yakutia, the findings show that a) the impacts of oil exploitation and climate change intersect and manifest in altering the dynamics of environmental degradation, resulting in adverse societal outcomes; b) community responses incorporate traditional orders, reproducing governance patterns from the Soviet era, hindered by the state and private interests that favour oil exploitation; c) expansion of oil exploitation is determined by power and politics cutting across the legacies of the past, imaginative geographies of hydrocarbon resources, struggles for resource rents, and struggles over authority and recognition; d) relational injustice mediates the power of communities to shape adaptation decisions in relation to oil projects; e) collective action to fight environmental pollution and inequitable outcome and processes has emerged, and increasingly using climate change narratives rather than opposing the hydrocarbon sector directly. The thesis argues that there is a need to conceptualise and develop adaptation pathways (and pathways towards development) that avoid 'double exposure' in resource frontiers, and this can be achieved by a more nuanced understanding of cross-scale power dynamics and justice as a starting point. The thesis contributes to knowledge by offering conceptual, methodological and policy insights into a more holistic understanding of adaptation in resource extraction regions, specifically in northern Russia.