School of Ecosystem and Forest Sciences - Theses
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ItemImpregnation of wood with stains( 2007)
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ItemEffects of adding nutrients on soil chemistry and tree growth in native Eucalyptus forests of south-eastern Australia( 2007)The decreasing area available for timber extraction in south-eastern Australia, due largely to social pressure to reserve greater areas of forest, has led to the consideration of fertiliser-application to increase wood output from the remaining available forest. Potentially deleterious effects of fertilising on water quality must be assessed before implementation on a wide scale. This is in accordance with relevant forest management policies. This study examined the effects of applying fertilisers containing nitrogen and phosphorus, on soil and soil-water chemistry in two pole-sized stands of mixed Eucalyptus spp in the Wombat Forest, in the Midlands Forest Management Area, Victoria, Australia. The findings are synthesised and discussed in relation to management of regenerating mixed-eucalypt forests in south-eastern Australia. Fertiliser treatments were none (R); 400 kg N ha-1 as ammonium-sulphate (N); or 400 kg ha-1 plus 202 kg P ha-1 as triple superphosphate coated with 10% sulphur (NP). It was calculated that incidental additions of S were 1371 kg ha -1 (N treatments), and 1696 kg ha-1 (NP treatments). It was expected that P would be principally adsorbed on soil surfaces; N immobilised in the soil organic pool and that metallic cations would enter the soil solution to varying degrees. Fertiliser-addition increased both plot-basal-area (BA) growth and the rate of stand self-thinning. In 3.8 years, BA in reference (R) plots at two sites increased by 7.3% and 23.4%. Where N alone was added, BA increased by 14.2% and 27.1%, while in NP plots BA increased by 17.1% and 42.7% respectively. Mortality was 9% in untreated plots compared to 14% in NP plots. Estimated increases in biomass growth equated to additional above-ground nutrient accumulation of 0.4 to 1.5 kg ha-1 of P, and 5.5 to 20.8 kg ha-1 of N. This represented only 0.2 to 0.7% of added P, and 1.4 to 5.2% of added N. Soil solution was extracted from 10 and 50 cm with porous-ceramic-cup tension-lysimeters (-0.6 kPa). Concentrations of P and N were low both before and after adding fertiliser. Across all treatments the maximum median PO43- concentration in soil-water at 50 cm was 0.12 ppm (mean 0.28 ppm). Typically PO43- concentrations were not higher than 0.03 ppm. The 400 kg ha-1 of added N was rapidly immobilised in the soil organic pool. The greatest mean NH4' concentration from a single sampling occasion was 1.1 ppm. The mean NO3 concentration at 50 cm was never higher than 0.26 ppm. After adding N in fertiliser the proportion of NO3- relative to NH4* in soil-water increased and was correlated with decreasing soil-water pH. Less than 1% of added P and N was recovered from soil solution at 50 cm. The largest pool of added P recovered was PO43- adsorbed to soil between 0 and 20 cm, due to the soil adsorption capacity being well in excess of the applied 202 kg P ha-1. Phosphate desorption using sequential extractions with a mild acid extractant (0.3M NH4F, 0.1M HCI) recovered between 25% and 116% of added P. Differences were attributed to both the amount of P added and the effect of time since treatment at different sites. Soil disturbance during sampler installation was found to be more likely to raise soil-water P concentrations at 50 cm than would adding up to 202 kg P ha-1. Among the ions in solution. SO42- and CI' were the dominant anions while Cat+ dominated the cation chemistry. In untreated forest 5042- in soil-water ranged from 7.7 to 16.0 ppm at 10 cm and 7.9 to 12.2 ppm at 50 cm. In fertilised plots up to 100.5 ppm SO42 was measured in soil-water at 50 cm depth. In the N treatment at 50 cm, SO42- in soil-water accounted for 9.4 % of applied S. compared to 14.0 % in NP. In untreated forest, soil-water Cl- and SO42- accounted for over 98% of the total soil-water anions, in roughly equal proportions at 10 cm, and CI- slightly higher at 50 cm. Following fertiliser-application soil-water pH at 10 cm fell from 6.3 in R to as low as 4.81 (N) and 4.45 (NP). At 50 cm pH never dropped below 6 and there were no visible departures from reference concentrations. Relative activities of K+ and Mg2+ in solution increased with decreasing pH, indicating increased leaching potential. Sulphate in soil-water increased total anion charge further in NP than in N. Total charge (cmolc L-1) for cations followed anions. A slight deficit in anion charge was likely due to the unquantified contribution of organic anions. These results confirm that despite the quantity of fertilisers added in this trial being double likely operational quantities, the forest and associated soils had the capacity to retain these nutrients through a variety of processes. The study validates the environmental sustainability of proposed intensive management practices including fertiliser-application in this forest type. It also emphasises the importance of understanding fundamental forest nutrient cycling processes when aiming to carry out intensive forest management practices in an environmentally sensitive manner.
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ItemA study of the creep performance of microwave-modified radiata pine in different external environments( 2007)A new innovative timber treatment developed at the CRC Wood Innovations, which involves high intensity microwave application and resins impregnation, is intended to provide products for a range of applications including structural engineering members. This study has been undertaken to obtain experimental data and provide better understanding of the creep performance and long-term behaviour of the new products. In the experiment, fifteen samples, five untreated, five treated with MUF resin and five treated with Isocyanate resin were loaded in four-point bending at 30 percent of the matched samples' failing stress, in a protected external environment in Brisbane, Australia for a period of nine months to date. The treated samples were found to produce lower relative creep deformations than the untreated sample. The samples treated with MUF resin showed better creep resistance than the samples treated with Isocyanate resin. Data from the first 90 days were used to obtain parameters for the two chosen models: the power law model and the 5- parameter model. While both models provided good fitting for the data, the 5-element model was found to possess better extrapolation capacity beyond the regression period. An increase in the period of regression data from 90 days to 150 days significantly lowered the errors in both of the models.
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ItemTowards association studies in Pinus radiata D.Don - populations and wood property candidate-genes( 2006)In Australia and New Zealand Pinus radiata D. Don wood quality is receiving increasing interest from tree breeders. This is partly due to declining resource wood quality associated with more advanced generation breeds leading to increased rejection and product downgrading in processing. While log segregation and wood grading at mill-door yields immediate benefits to processors the underlying cause is not addressed. The only long-term solution is to include wood quality in breeding programs. Wood quality traits are costly and difficult to measure. Marker-assisted selection offers a potential solution and quantitative trait loci (QTL) mapping studies have been undertaken with the aim of facilitating this. It is becoming increasingly clear that in widely outcrossing species with long generation times and very large genomes these approaches will not work. The identification of the underlying genetic sites, or tightly linked marker sites, would rectify this and in model species linkage-map based cloning has been used extensively. This approach is also not practical in species such as P. radiata. Association testing combined with a candidate-gene approach is therefore widely believed to be one of the only methods remaining. This approach uses a priori information to select and then test the phenotypic effects of variants within candidate-gene loci. Implementation of these studies relies heavily on the results of other investigations, especially those that generate DNA sequence information. Also required is detailed knowledge of the genetic population structure, the patterns of nucleotide diversity and the patterns of linkage disequilibrium. On a more practical level suitable populations need to be identified while the current methods for the collection and handling of samples for molecular investigations are limiting. The selection of candidate genes is also a non-trivial process. For candidate-gene association studies to be successful in P. radiata all these factors need to be addressed. This formed the main aim of this thesis. A multi-pronged approach was used. Firstly, at the population level, the genetic resources available for association studies were identified and the underlying genetic population structure of these resources and the patterns of nucleotide diversity and linkage disequilibrium were investigated. Secondly, improved methods for the collection and isolation of genomic DNA were developed and thirdly, a small set of wood quality candidate-genes were selected and further characterised with the aim of identifying those with the most promise of harbouring causative variation for inclusion in future association studies. This was achieved by literature based review, linkage mapping onto wood property QTL maps and neutrality testing. Results include support for previous population genetic studies showing P. radiata to have a complex genetic structure compared to most pine species. This study also indicated significant levels of migration between the three mainland populations. Within the candidate-genes two, cinnamyl alcohol dehydrogenase and sucrose synthase, showed interesting patterns of population differentiation and/or nucleotide diversity while the results for one other gene, korrigan, did not agree with previous investigations.
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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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ItemPerceptions of ecoforestry in selected project sites in Papua New Guinea( 2005)Land and forest resources in Papua New Guinea are held under customary ownership by clans. But clans have participated little in decision-making processes in any major forest resource development projects, although these have often had major effects on their areas and lives. The decisions about industrial logging have been made mainly by the government and multinational logging companies - though royalties have been paid to clans for extraction of the timber. Past logging operations have provided some infra-structural benefits but have also led to many environmental and socio-economic problems that affect the livelihoods of rural people. In an attempt to halt the further spread of large-scale logging, and under pressure from the World Bank, the European Union Commission to PNG and the Government of Papua New Guinea entered into a bilateral agreement to initiate the Papua New Guinea Ecoforestry Program in 1995. This was to be implemented through the involvement of clans as the forest resource owners. This study explores the experiences and views of clan members in two ecoforestry projects in West New Britain Province. The aims of the study were to describe the ecoforestry program in general and the two project study sites, and then to explore clan members' perceptions of the ecoforestry approach being promoted, based on their experience. The study was conducted with a view to identifying ways of improving the effectiveness of ecoforestry development projects in Papua New Guinea. Two ecoforestry project sites were chosen as case studies. The main data collection techniques were in-depth interviews with clan members participating in the ecoforestry projects, and observations of activities. The qualitative data collected were analysed using elements of a 'grounded theory' approach, which involved transcription of interviews from PNG Pidgin/English to word processed files in English, then examining and coding the transcripts for main themes. From these themes theory was developed about the way clan people viewed ecoforestry, and the prospects for the future of the approach. Data from secondary sources were used in description of the sites, and in the analysis and interpretation of data from interviews. The findings revealed strong views among some respondents about their gains in mechanical and management skills through the ecoforestry projects, and also on problems of transparency in financial management of projects, the hard work involved in ecoforestry, and difficulties faced by their female members left at home alone. Other difficulties mentioned were those of maintaining equipment and of sourcing spares for machines and securing reliable markets. Despite the many negative views expressed on ecoforestry, there was quite wide acceptance that the approach had major potential advantages in terms of self-determination for clans, learning skills, employment and income, village infrastructure and environmental care of the forest - when compared to industrial logging. In the final chapter a Force Field Analysis is used as a framework to discuss the implications of the main finding - for future efforts in ecoforestry in PNG. In general, the clan members were reluctant to give definite views on the future prospects of ecoforestry after withdrawal of the supporting aid agency. In answer to questions on this topic they tended to express views on the need for certain types of support in the future, and other ways for overcoming the difficulties of the past. There was a general desire to be given the opportunity to continue with the ecoforestry approach, in the hope that there would be improvement in community participation, skills and hence in benefits to their clans and communities.
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ItemCardamom cultivation, livelihoods and biodiversity in a H'mong farming system in Northwest Vietnam( 2005)The recovery of the cardamom market in northwest Vietnam since the mid-1980s has seen many new groups of small farmers engage in the cultivation of this crop. A particular type of cardamom (Amomum tsao-ko) has a long history of cultivation by H'mong people in the Hoang Lien Mountains of northwest Vietnam. This thesis examined the implications of cardamom cultivation for H'mong livelihoods and forest biodiversity in those mountain farming systems, and explored options for improving farmer livelihoods through cultivation of this crop. Cardamom is in demand for both its aromatic and medicinal properties. It is providing a key source of income for H'mong ethnic farmers living at higher altitudes, people typically isolated from many other markets. The perennial crop requires partial shade and cool temperatures and for these reasons farmers utilize montane forest for its cultivation. These forests are also important for their biological diversity. Some cardamom cultivation practices (including tree felling to allow light to the crop) have been identified as having potentially negative effects on biodiversity. In this study a (partial) Farming Systems Research approach was adopted, which involved describing the farming systems at three (case study) villages, and identifying implications of cardamom cultivation for livelihoods and biodiversity at each site. Farmers were making transition from upland crops (rice and maize) to wet rice cultivation through the use of terraces to meet subsistence requirements, and had adopted cardamom as a cash crop despite the major labour inputs required in establishment. Extensive areas of forest and/or grassland on steep slopes dominated village sites. Cardamom was found to provide a key source of cash income for almost all farmers in the study area and had raised household income levels above the government-defined poverty level. Growers were committing significant labour resources over the initial five years of cardamom establishment, prior to receiving income. This labour on cardamom production competed with, but did not entirely replace, labour input towards improving subsistence income, i.e. establishing terraced fields for rice. Market uncertainty for cardamom presented some risk to small-scale farmers' livelihoods. If the cardamom market were to become flooded or depressed, the outcome would be a major setback for a large proportion of households, given the modest income from other cash crops and low total current incomes. Future inquiry aimed at better market understanding and ensuring stable income levels is recommended. Cardamom fields contained a higher number of plant species representative of montane forest, and in general much more favourable habitat for forest dwelling fauna than existed in alternative agricultural land-use types such as rice fields, upland fields or grassland. Tree cover was reduced by 25-50 per cent as a result of cardamom field establishment in forest, but there was no selective tree species removal. The lack of knowledge of the effect of forest thinning for cardamom cultivation on fauna habitat and animal movement means the abundance of some fauna species may be decling without our knowledge. However, farmers' involvement in cardamom growing ensured that forest would not be removed for other (less biologically diverse) types of land use. Farmers from certain villages have asserted de facto local use rights over particular areas of montane forest through their establishment of cardamom fields. As a result, some farmers had gained access to montane forest for cardamom cultivation - where they had no access to land previously. Research on cardamom production should focus on providing opportunities for farmers without access to montane forest, to grow cardamom in agroforestry systems on suitable land types near their villages. Farmers could be involved in `adaptation' trials aimed at developing new agroforestry systems using shade from planted tree species - as has been achieved in India and other regions. Such agroforestry systems on existing agricultural land may also make a positive contribution to forest biodiversity by increasing total vegetation.
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ItemPhotosynthetic responses to light, nitrogen, phosphorus and pruning of Eucalyptus in south-eastern Australia( 2005)Eucalypts frequently grow faster after additions of fertiliser, but more slowly in the shade or following `green pruning'. The coupling of rates of growth to environmental factors is at least partly due to acclimation of photosynthetic processes. Photosynthesis rarely proceeds at maximum rates in natural environments as photosynthetic processes and the supply of basic requirements of photosynthesis (CO2, H20, light, phosphorus and nitrogen) vary at both short (minutes to hours) and longer (days to months) time scales. Currently we lack mechanistic explanations for how these variables, alone and in combination underpin changed growth rates in Eucalyptus. This study examined growth and photosynthetic characteristics in glasshouse-grown seedlings and field-grown trees of Eucalyptus species that are commonly planted for forestry and revegetation purposes in central Victoria. Acclimation to light (among seedlings and within canopies), nutrient availability (phosphorus and nitrogen) and increased sink-strength for photosynthates were the primary foci of the study. In each instance I examined distribution of leaf nutrients within a canopy and allocation of N to Rubisco and chlorophyll to assess the degree to which nutrients limit photosynthesis in Eucalyptus. A novel technique was introduced to quantify the allocation of inorganic phosphorus within cells (cytoplasm versus vacuole), followed by an assessment of inorganic phosphorus allocation in response to a long-term reduction in phosphorus supply. In all circumstances, rates of growth were responsive to environmental conditions. Growth responses were underpinned by altered patterns of biomass partitioning and changed leaf morphology more than by rates of photosynthesis per se. There was little difference in adaptive strategies implemented by seedlings and trees: both were oriented towards the accumulation of nutrients rather than increasing rates of photosynthesis. Photosynthesis was reduced by shading (among different plants and within the canopy of a tree) and reduced phosphorus supply whereas N had little effect on photosynthesis. Analysis of pools of inorganic P revealed that adequate supplies were maintained for photosynthetic processes regardless of P supply, therefore reduced photosynthesis follows, rather than leads, a more general leaf-level response to reduced P. Similarly, changed partitioning of nitrogen between Rubisco and chlorophyll was unnecessary as leaf nitrogen concentrations were consistently maintained at well above published minimum levels. Hence, photosynthesis was not up-regulated following increased nitrogen or phosphorus supply; instead excess nutrients were accumulated and used to support increased biomass. One exception was after defoliation, when up-regulation of photosynthesis was observed, presumably to ensure the demand for photosynthates could be met by a reduced leaf area. Sensitivity analyses consistently revealed variation in photosynthetic rates owed more to altered biochemical activity (e.g. Jmax and Vcmax) rather than stomatal conductance regardless of growth condition (glasshouse versus field). Hence, whilst Eucalyptus has considerable photosynthetic potential, faster rates of carbon fixation are only exhibited in the short-term. In part, this is due to the multiplicity of factors involved in `optimisation' of photosynthesis and their individual and collective responses to environmental conditions. In the long term however, increased canopy photosynthetic capacity follows only an increased photosynthetic area.