School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemNo Preview AvailableThe chemical modification of Pinus radiata (D.Don.) with furfuryl alcohol(University of Melbourne, 2006)Wood blocks impregnated with furfuryl alcohol required a standing time of 48 hours to ensure complete swelling of the wood. Total penetration of the blocks was required for maximum swelling and water resistance in treated blocks. The presence of water in the treatment solution caused rapid swelling of the wood block, whereas 100% furfuryl alcohol created a slow rate of swelling. The presence of water in the cell walls accelerated the rate of swelling of 100% furfuryl alcohol, but not to the extent as when the water was present in the treatment solution. Dimensional stability decreased as the water content in the treating solution increased, but compared to the controls (6 - 8%) there was significant improvement in dimensional stability (2.5 - 4%). The resin forming efficiency varied with the amount of water present, but never dropped below 85%. Treated wood samples compressed to a density of 1200 � 1400 kg/m3 were more stable when exposed to water, and had increased hardness and MOE compared to untreated compressed samples. The curing of furfuryl alcohol in beakers gave a clear indication of catalyst performance with variable catalyst concentration and curing temperature. An increase in catalyst concentration increased the resin forming efficiency which was dependant upon the catalyst strength and number of pKa values. Of the catalysts stable at room temperature, oxalic acid, maleic acid and zinc chloride were the best performed for wood impregnation, with respect to the parameters investigated. The higher the resin forming efficiency the lower the volumetric swelling. The initial moisture content of the wood had a direct effect upon the swelling of wood blocks. All samples with an initial moisture content of 12% performed better than the corresponding treatments used with oven-dried blocks. Further, higher catalyst concentrations and curing temperatures improved performance. Oxalic acid at a 4% concentration with furfuryl alcohol and a 2% concentration with furfuryl alcohol � formaldehyde formulations produced the best resin forming efficiency, permanent swelling and water property results. Conditioning time between pressure impregnation and curing was unnecessary with no improvement in properties with the cured wood block. Furfuryl alcohol with a 4% oxalic acid concentration produced the most desirable overall results with resin forming efficiency (111%), permanent swelling (8%), water uptake (8%) and dimensional stability (2.8%), when cured for 24 hours at 120�C. Analysis of leachate by GCMS suggested that a minimum curing time of 12 hours is required with furfuryl alcohol and 6 hours with a furfuryl alcohol � formaldehyde formulation to substantially reduce the amount of leachable material from a treated wood block, confirmed by dimensional stability trials.
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ItemNo Preview AvailableThe chemical modification of Pinus radiata (D.Don.) with furfuryl alcohol(University of Melbourne, 2006)Wood blocks impregnated with furfuryl alcohol required a standing time of 48 hours to ensure complete swelling of the wood. Total penetration of the blocks was required for maximum swelling and water resistance in treated blocks. The presence of water in the treatment solution caused rapid swelling of the wood block, whereas 100% furfuryl alcohol created a slow rate of swelling. The presence of water in the cell walls accelerated the rate of swelling of 100% furfuryl alcohol, but not to the extent as when the water was present in the treatment solution. Dimensional stability decreased as the water content in the treating solution increased, but compared to the controls (6 - 8%) there was significant improvement in dimensional stability (2.5 - 4%). The resin forming efficiency varied with the amount of water present, but never dropped below 85%. Treated wood samples compressed to a density of 1200 � 1400 kg/m3 were more stable when exposed to water, and had increased hardness and MOE compared to untreated compressed samples. The curing of furfuryl alcohol in beakers gave a clear indication of catalyst performance with variable catalyst concentration and curing temperature. An increase in catalyst concentration increased the resin forming efficiency which was dependant upon the catalyst strength and number of pKa values. Of the catalysts stable at room temperature, oxalic acid, maleic acid and zinc chloride were the best performed for wood impregnation, with respect to the parameters investigated. The higher the resin forming efficiency the lower the volumetric swelling. The initial moisture content of the wood had a direct effect upon the swelling of wood blocks. All samples with an initial moisture content of 12% performed better than the corresponding treatments used with oven-dried blocks. Further, higher catalyst concentrations and curing temperatures improved performance. Oxalic acid at a 4% concentration with furfuryl alcohol and a 2% concentration with furfuryl alcohol � formaldehyde formulations produced the best resin forming efficiency, permanent swelling and water property results. Conditioning time between pressure impregnation and curing was unnecessary with no improvement in properties with the cured wood block. Furfuryl alcohol with a 4% oxalic acid concentration produced the most desirable overall results with resin forming efficiency (111%), permanent swelling (8%), water uptake (8%) and dimensional stability (2.8%), when cured for 24 hours at 120�C. Analysis of leachate by GCMS suggested that a minimum curing time of 12 hours is required with furfuryl alcohol and 6 hours with a furfuryl alcohol � formaldehyde formulation to substantially reduce the amount of leachable material from a treated wood block, confirmed by dimensional stability trials.
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ItemNitrogen fixation by Casuarina oligodon agroforestry in the Papua New Guinea central highlands( 2006)Casuarina oligodon L. Johnson is a multipurpose tree species grown in the highlands of Papua New Guinea (PNG). The integration of C. oligodon into agricultural systems is seen by villagers as means of restoring soil fertility, controlling soil erosion, providing shade for crops and producing fuel wood and building materials. Biological nitrogen fixation by C. oligodon through symbiotic relationships with Frankia (micro-organism) under field conditions in short (5-10 years) and long (11-15 years+) fallows in the PNG central highlands was investigated using the 15N natural abundance technique. Results from the study showed that as much as 70% of N in C. oligodon was derived from the atmosphere. The rate of N2 fixation was relatively low in short fallows of casuarina and increased as the trees aged in the long fallows. A rate of N2 fixation up to a maximum of 36 kg N ha -1 year -1 was estimated based on commonly practiced tree stocking rates and field conditions in the PNG highland areas. Although casuarina fallows tend to accumulate higher total N and C compared with equivalent period of grass fallows, the amounts of N and C in the surface soils of all systems under the study showed no significant difference. The amounts of total N and C under long fallows of casuarina (11-15 years+) were generally greater than short fallows of casuarina (5- 10 years). A significant proportion of the total N was stored in the above ground biomass of trees that were more than 10 years of age. Management of the standing biomass, particularly when the fallow is converted back to the cropping phase, is therefore critical in ensuring that the farmers are able to gain maximum benefit from the fixed N. Whilst the removal of stem wood for use as fuel or building material may be an important product of the agroforestry system, retaining the foliage, small branches and bark on the site is vital in sustaining agricultural productivity.
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ItemThe 'Boxing Day' tsunami - effects and responses among farmers in Maldives( 2006)The `Boxing Day' tsunami of 26 December 2004 devastated coastal areas of eight countries within and surrounding the Indian Ocean, including Maldives. More than 200,000 coastal inhabitants in the affected countries lost their lives; those remaining in the affected areas faced severe disruptions and hardships. Maldives is an atoll island nation in the Indian Ocean. The exclusively low-lying nature of the islands of Maldives make them vulnerable to natural hazards such as tsunamis, wave surges from tropical storms and potential sea-level rise. Agriculture plays an important role as a source of income for the rural population of Maldives. It is carried out in mixed home gardens, settled rain-fed cropping fields, bush fallow shifting cultivation areas and year-round horticultural production fields across agricultural islands of Maldives. Waves of over four metres in height, resulting from the tsunami, swept across the atolls and islands of Maldives. The islands suffered massive physical destruction to structures and facilities. Farming communities, in particular, lost homestead trees, crops, buildings and infrastructure through wave action and inundation. Agricultural lands were inundated, and inland soils and water reservoirs were contaminated with seawater and detritus. This study, undertaken a year after the tsunami, sets out to determine the main effects of the tsunami on the livelihoods of the farming communities of Maldives. Social research methods were used to catalogue the immediate and long-term strategies that affected farmers adopted to deal with losses of food, income and productivity of lands. Case studies of three affected islands were used to explore the effects the tsunami had on livelihoods of farmers on these islands, according to the residents. Assessments were carried out on soils and groundwaters of case study islands to measure the possible long-term effect of the tsunami on farming areas. The study revealed that continued disaster aid, and improvement of people's awareness of natural hazards and disaster relief processes among farmers and agency staff are important for the sustainability of agricultural livelihoods in Maldives. Building institutional capacity in monitoring and assessment of soil and groundwater quality were also noted to be essential. Suggestions for assisting recovery of farming households are discussed, based on views of farmers, and these could be of use to international development organizations and local institutions, to assist in future planning and development of areas that are vulnerable to natural hazards in Maldives.
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ItemLooking for expansins : a molecular approach to the investigation of tylose development and heartwood formation in Eucalyptus nitens( 2006)Advanced stages of stem development in many tree species, including eucalypts, are marked by the transition of conductive sapwood to non-conductive heartwood. Heartwood formation follows a characteristic sequence of events involving the accumulation of phenolic compounds in ray parenchyma cells, the occlusion of vessels by tylose and/or gum formation, cell death and the subsequent release of phenolic compounds into the surrounding tissue. These events are dependent upon the activity of ray parenchyma cells, but the molecular processes involved, particularly with regard to tylose formation, remain largely unknown. The identification of molecular pathways leading to tylose formation might yield insights into heartwood formation. A molecular approach to the investigation of tylose formation is hampered by the paucity and inaccessibility of ray parenchyma cells and the asynchronous nature of tylose formation. Based on the assumption that wound-induced tyloses and those formed during the transition of sapwood to heartwood develop via a common mechanism, these difficulties were overcome by using the wounding response of the tree (a 12-year-old Eucalyptus nitens sapling) to induce extensive and simultaneous development of tyloses. Tylose formation involves the marked extension of a primary cell wall structure. Elsewhere, such wall extension has been closely associated with the activity of expansins. These constitute a large, multi-gene family of proteins which are widely distributed throughout higher plants and which have been shown to induce relaxation and extension of primary cell walls, often in a cell- and tissue-specific manner. It is proposed that expansins are likely to be involved in tylose formation. Ray and axial parenchyma cells are the only living cells found in sapwood, and primary cell wall extension is only possible through tylose formation. Thus, gene expression associated with wall extension occurring in sapwood is likely to be associated with tylose formation. Cellular material from outer sapwood showing extensive wound-induced tylose development was successfully harvested and partial cDNA sequences displaying significant homology with a-expansins were identified. This provides circumstantial evidence that expansin gene expression is associated with tylose formation and should encourage further investigation of the molecular pathways involved in this process.
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ItemImpacts of national park on local communities : a case study of Jigme Singye Wangchuck National Park, Bhutan( 2006)Bhutan has a rich and varied biodiversity that has both regional and global significance. It has been declared one of the world's ten most important global biodiversity `hotspots'. In order to protect and preserve this mega-diversity, Bhutan has devoted 26 per cent of its total land area to designated Protected Areas (PAs). Another nine per cent is set aside for biological corridors connecting all PAs in the country. Empirical evidence worldwide indicates that the establishment of PAs such as National Parks can impact on populations through restrictions on traditional resource use and crop and livestock losses to wild animals. No studies have yet been conducted in Bhutan but anecdotal evidence suggests that similar stories of constraint and restriction are emerging in the country. The aim of this research is to explore how the establishment of PAs in Bhutan is impacting on local residents. Using a qualitative case study approach, this study explores the perceptions of villagers, local elected leaders and government officials residing in two districts of Jigme Singye Wangchuck National Park (JSWNP). The results suggest that declaring a National Park has been perceived by rural communities as yielding a number of negative consequences. These include the restriction of access to traditionally-used resources and increased depredation of crops and livestock by Park animals. However, many respondents expressed their support for the protection of remaining natural resources for the benefit of future generations. Residents also recognise and appreciate the support provided by the Park management in the form of supplies such as seeds, seedlings, breeding bulls, machinery and budget for school and clinic improvement. Respondents expressed their desire for continued or even increased support in future. Residents' perceptions of the Park and its impacts appear to be particularly influenced by their level of dependence on natural resources, family wealth and proximity to markets and Park offices. The study also shows that the whole process of Park conceptualisation, establishment and management is seen as having been imposed. Residents do not understand how the Park was conceptualised and established. Their participation in Park related planning and decision-making processes is limited to small elites. Furthermore, the authorities of JSWNP are seen to be placing too much emphasis on the enforcement of Park rules, to deter people from extracting natural resources. This has led to resentment among the local residents. Enforcement of rules is also said to be inconsistent across the villages studied. While there is some concern amongst residents about the imposition of restriction, there exists a strong local conservation ethic and traditional resource management institutions in rural communities within the Park. However, these are largely unacknowledged by conventional conservation strategies, which are based on western scientific knowledge. The conventional conservation strategies need rethinking. They provide limited opportunity for long-term success of the Park as they disengage local residents from the conservation processes. Successful Park management will require a shift from an imposed conservation ethic - which retains external control of the management and end-uses of Park resources - to an approach which devolves more responsibility and decision-making authority to local communities. This would mean increasing engagement with local people, a shift from `policing' to monitoring and research, an acknowledgement of the local conservation ethic and the provision of alternative economic opportunities. Finally, more research is needed to increase our understanding of residents' perceptions and attitudes about National Parks, the ecological footprints of residents on Park resources and the role of local conservation ethic and institutions. Such understanding will enable future policy and decision makers to develop informed decisions and policies that are more likely to engage local people in the conservation process.