School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemThe dynamics of growth in even-aged stands of Eucalyptus obliqua (l'herit)( 1968)The genus Eucalyptus contains a large number of species suitable for the commercial production of timber, but the history of their forest management is comparatively recent, being initially founded on traditional European experience. Despite this tradition and the fact that many species have certain silvicultural properties in common distinguishing them from other timber producing genera (Jacobs, 1955), there already exists a diversity in silvicultural systems, even for the one species or species association in a single region. This diversity appears to be associated with the development history of the forest region, because there has been a general tendency to perpetuate the characteristic forest structure of a particular area at the time that planned management was commenced. This structure has varied from extensive areas of even-aged stands of a single species to intimate mixtures of species of all ages and sizes in association. The variation in forest structure appears to have developed largely from a diversity in the history of settlement and early exploitation. Fire history, access history, intensity and frequency of past utilization have all played a prominent role in forming the characteristic forest structure of a particular area. Regardless of whether growing in regular or irregular forests, the determination of tree and stand age for the majority of eucalypts is extremely difficult or even impossible. The identification of annual rings is reasonably reliable only for those species growing in subalpine and alpine climatic zones of Australia. Therefore, in the absence of adequate compartment and stand history records, management planning in the eucalypts must be based on methods which do not require precise knowledge of tree and stand age. While age is not normally required for the management of irregular forests, it has been fundamental to the planned management of even-aged forests. The ability to distinguish sites of differing productive capacities is an important aid in forest management. The most popular method of site classification is the site index, which gives stand height at a particular reference age. If age is unknown this method cannot be used and alternative methods of site quality determination have not yet been developed for the eucalypts. (From Introduction)
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ItemGrowth and yield models for South Australian radiata pine plantations: incorporating fertilising and thinning( 2001)This thesis describes the development of models to predict the volume growth response of South Australian radiata pine plantations to the interaction of the silvicultural tools of thinning and fertiliser used in combination. Some years ago this issue was identified as the component of the ForestrySA yield regulation system most in need of addressing and as a result a large thinning and fertiliser experiment was established. This was designed to determine whether a thinning and fertiliser interaction existed and to enable this interaction to be modelled. At the time it was established it was believed to be the only experiment of its kind in the world and this still appears to be the case. The thinning and fertiliser interaction models described in this thesis were designed to integrate with the models already implemented in the ForestrySA yield regulation system so that more precise predictions of future log availability can be provided, and improved management decisions can be made. Three sets of component sub models are described which operate at a stand level to: • predict the total volume growth of the main crop between the time of fertilising and the next thinning, approximately seven years hence; • predict the total volume growth of the portion of the stand which will be thinned (known as the thinnings elect) at the next thinning, between the time of fertilising and the next thinning; • predict the annual volume growth response of the stand between the time of fertilising and the next thinning. Further research is described to identify the data sets that are likely to be required for future analysis and revision of the South Australian growth and yield models. Adopting the future research recommendations will ensure that the consideration of the financial and economic benefit of alternative silvicultural prescriptions is broadened to include a more diverse range of sites and include log and wood quality considerations.
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ItemThe effects of fertilisation and wastewater irrigation on the biomass and nutrient content of Pinus radiata D. Don( 1985)Detailed measurements were made of soil and stand characteristics before experimental plots were designed and laid out by collaborators from CSIRO. Fertiliser and irrigation were applied in a 2 x 2 factorial design, giving four treatment combinations. Irrigation commenced when the stand was 15 years old, and continued for 29 months; phosphorus at the rate of 5 g m- 2 was evenly broadcast as superphosphate when the stand was 16 years old. The study of biomass and nutrient uptake was comprehensive. Above-ground biomass was estimated by regression analysis of weights and dimensions of 24 sample trees, six trees being selected from each treatment. Standing litter was sampled, and root biomass estimated from core samples and by excavating the roots of one tree per treatment. Uptake of nine nutrients was estimated after measuring their concentrations in all components of the stand. Fertilisation with phosphorus had no effect on total above-ground biomass over a two-year period. Foliar analysis at the start of the study indicated that the trees were mildly deficient in phosphorus, but there was no increase in foliage biomass after fertilisation, despite substantial uptake of the applied nutrient. The lack of growth response was attributed to limiting soil moisture. This finding reinforces results of studies elsewhere that fertiliser responses are site-specific. (From Summary)