School of Ecosystem and Forest Sciences - Theses

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    Making the connection between history, agricultural diversity and place: the story of Victorian apples
    Christensen, Johanna Annelie ( 2016)
    Apple growing practices are embedded in a productivist mentality aiming for ever higher efficiency and productivity. And while the climate change impacts are to a large extent known, there is little attention given to the coupling of the social and the ecological effects. I use apple growing as a case study to explore the relationship between place, biodiversity and rural change in Victoria. My research is based on historical research; including an analysis of the Museum Victoria’s collection of wax apple models, and in-depth interviews with orchardists. By drawing on environmental history, social-ecological systems thinking and Bourdieu's theory of practice, I highlight the importance of a systems perspective and inform it by emphasis on the critical role of underlying power structures and individual dispositions, or the habitus, of the growers. These dispositions have been shaped and internalised by the growers’ histories and their physical surroundings. Orchardists have been able to respond to intensifying production requirements by utilizing technologies and scientific nous to keep up with the continuous aim for efficiency. Growers are caught up in a self-reinforcing cycle of satisfying the demand for perfect apples by adopting expensive techno-scientific approaches to enable ever more intensive production. The symbolic violence and amplified biophysical pressure orchardists experience has driven many to despair; resulting in a significant decline in small scale apple growing businesses over the last decade. I offer some suggestions for government policy and support measures and argue that any services or support programs need to be tailored to the appropriate level and need of each orchard business and the individuals who are involved. My analysis shows that those growers, who engage more closely with their biophysical place as well as their history and identity as apple growers in that place are (re-)creating another version of what it means to be an apple grower. In some cases this is resulting in resistance to the vortex of agricultural productivism that has been the basis of their existence for many generations.
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    Effects of adding nutrients on soil chemistry and tree growth in native Eucalyptus forests of south-eastern Australia
    Severino, Dean Christopher ( 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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    Photosynthetic responses to light, nitrogen, phosphorus and pruning of Eucalyptus in south-eastern Australia
    Turnbull, Tarryn Louise ( 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.
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    Multiple resources planning and inventory
    Spencer, Raymond Douglas ( 1995)
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    Interregional trade in sawntimber in Australia
    Bigsby, Hugh ( 1989)
    The purpose of this study has been to develop a modelling framework which incorporates the essential features of the sawntimber market in Australia and which is capable of being used to study both the interregional trade patterns within Australia and the impacts of various changes on the sector. This firstly involved the determination of demand and supply relationships for the market and secondly the development of a spatial equilibrium model of trade. The basic structure of sawntimber market was studied with the use of two different approaches. The first was an ad hoc, statistical model of the sawntimber market in Australia. The statistical model provided new results for price elasticity of sawntimber demand in Australia. Elasticity of demand for sawntimber was found to be -0.783, an improvement on previous studies which found no relationship between sawntimber demand and the price of sawntimber. It also provided new information on the structure of the sawntimber market in Australia and the substitution between imported and domestic supplies. In particular, the results showed that domestic and imported sawntimber do not compete on the basis of price in the Australian Market. The second approach was through a theoretical model of the production structure of the sawmilling industry using the translog cost function. The estimation of the cost function served two purposes, the first to provide a measure of the slope of the supply curve for the trade model, and the second to provide information about the production structure of the industry. Although .data problems ultimately prevented the use of the translog cost function in the spatial equilibrium model, it did provide new information on input substitution, technological change and scale economies in the sawmilling sector. In particular, the results found that most inputs are substitutes, there are diseconomies of scale, and that technological change has been capital and energy using, and labour saving. The second component of the study was the development of a spatial equilibrium model of the sawntimber sector. This was done with a non-linear programming framework and based on demand and supply elasticities provided by the statistical model. The result was a model which could be used to study the impacts of demand and supply changes. The model was used to study the impact of the forecast increase in log availability by the year 2000. An important result from the use of this model was to demonstrate that an 11.5 percent price decrease could cause the domestic market to absorb 60 percent of the sawntimber which the increased log availability could allow. To summarise, the research encompassed in this thesis has provided new information on the economic structure and performance of the sawntimber sector in Australia. It has also provided a basis for new research and applications of the results. In this study the results were applied to a spatial equilibrium trade model of the sector in Australia. This in turn has provided a new basis for policy analysis in forest industry, in particular issues involving trade and demand or supply shocks.
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    Limits to recruitment of a rare conifer: Wollemia nobilis
    Zimmer, Heidi Christina ( 2016)
    Wollemia nobilis (Wollemi pine, Araucariaceae) is an Australian conifer and one of the world’s rarest trees, with a known population of 83 mature trees and 200-300 seedlings in the wild. Wollemia nobilis is a high-profile threatened species because of its discovery near a major capital city (Sydney) in 1994. My research began with the observation that the W. nobilis population had few individuals between the seedling and canopy tree size classes (i.e., between 2-20 m in height), and questions about potential recruitment limitation in W. nobilis. I found that inter-annual variation in seed production, estimated from photographs of W. nobilis mature tree canopies, was not likely to limit the recruitment of new seedlings (Chapter 2). Through monitoring W. nobilis seedlings in the wild (Chapter 3), I observed that new seedlings germinated each year, but most of these seedlings died soon after germination (65% of seedlings lived less than one year) and (44% of established juveniles survived the entire 16-year monitoring period). However, for the remaining seedlings, survival rates were much higher, although growth rates remained low. Shade-tolerant trees, such as W. nobilis, commonly need increased light to grow rapidly. Tree rings from established W. nobilis suggested rapid growth from early establishment and greenhouse studies showed W. nobilis increased growth with increased light. It is likely that canopy gap creation is required for increased growth of W. nobilis seedlings in the wild. Fire and drought are key threats to the survival of established W. nobilis seedlings. Through ex situ burning experiments I found that W. nobilis could resprout after fire, providing further evidence to challenge to the historical idea that all rainforests are fire sensitive (Chapter 4). Alternatively, W. nobilis was intolerant of prolonged drought, compared with other species from the Araucariaceae family (Chapter 5). To extend my knowledge of W. nobilis recruitment, I then set about establishing a new W. nobilis population (Chapter 6). I planted 191 W. nobilis into a new site, similar to the wild site, but with a greater range of light availabilities. Two years after planting I found that survival, but not growth, was improved at higher light sites. Monitoring is ongoing. The life history of W. nobilis (particularly slow growth) in conjunction with its environment (deeply shaded rainforest) results in infrequent recruitment – similar to many threatened conifers. Wollemia nobilis differs from most threatened conifers in that it is not affected by human and land-use change threats, such as timber harvesting. However, humans can play a role in the protection and recovery of W. nobilis, such as through the active establishment of new W. nobilis populations in the wild. Beyond its scientific value as a relict population, the high profile of W. nobilis and its potential to raise awareness of biodiversity issues provide further impetus for maintaining W. nobilis population persistence in the wild.