School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemTree growth modelling of Eucalyptus delegatensis (R. T. Bak.) and other eucalyptus species utilising early-aged stand measurements( 1999)Growth modelling methods for Eucalyptus species that can make use of minimal measurement information are scarce but necessary for those involved in small-scale forestry to make informed decisions about investment and management options. A computer program, FARMTREE, is available for evaluating the costs and benefits of trees on farms, however its growth modelling functions could be improved. This thesis achieves this for Eucalyptus delegatensis (R. T. Bak.) and provides a series of stand basal area, survival, diameter distribution and individual tree diameter increment models that could be incorporated into a FARMTREE-like program. While not a major farm forestry species, the models have been related to other Eucalyptus species and when more later-age data become available, the methods used here could be fully applied to more suitable species. A systematic series of growth predictions were made, with estimates from the earlier processes being used in the next. Initially, the Gompertz function was selected as the best of five non-linear equations and used to model stand basal area based on two, early-age measurements, while keeping the asymptotic parameter constant. Survival was modelled using a modified logistic function with basal area and age as the predictor variables. The results from the above procedures were then used to model diameter distributions using a percentile-based parameter recovery procedure. The predicted distributions were assessed by comparing them to the actual cumulative density functions. Comparing the predicted estimates of basal area, mortality and diameter distributions to those produced by FARMTREE showed that the new estimates were better, both for the stands for which the models were developed, and for an independent data set. Individual tree diameter increment models based on distance-independent competition indices were also studied. Overall, the predictions for two-year diameter increment were not as good as for the previously studied areas of growth. This was especially noticeable when observing the results for the verification data set. These poorer results for diameter increment may be because of the less flexible methods used or perhaps partially due to the accumulation of previous prediction errors. The research approaches and functions used are easy to apply, efficient, accurate and require minimal actual growth measurement information. They could be applied to other species in greater detail when more information becomes available and could be incorporated into FARMTREE or a similar package for use by owners and managers of small farm forests with the expectation of providing improved growth predictions.
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ItemThe effect of growing location and time of sowing on the production of premium quality oilseeds in south-eastern Australia( 1998)New Brassica oilseeds with modified fatty acid profiles tailored to specific end-uses are being developed in southern Australia. However, the fatty acid composition of Brassicas are known to vary markedly with environmental conditions during growth. A series of experiments were conducted to establish the most appropriate regions and sowing times within south-eastern Australia for the production of high oleic acid canola (HOAC), low linolenic acid canola (LLAC) and high erucic acid rapeseed (HEAR). Controlled experiments were conducted to evaluate the, effects of water deficit and temperature stress on fatty acid composition of conventional canola, HOAC, LLAC and HEAR. Ten years of data from the advanced canola trials of Agriculture Victoria were analysed, and a three-year trial was undertaken to identify the south-eastern Australian locations which produced specialty cultivars with the highest oil and seed protein content, lowest glucosinolate concentration, and premium oil quality (i.e. most appropriate fatty acid composition). Two glasshouse trials were performed to determine the separate effects of severe water deficit and three days of high (32C) and very high temperatures (37C) at 10, 20 and 30 days after flowering (DAF) on the oil composition of a HEAR cultivar and HOAC cultivar. In contrast to earlier work on the effects of sustained high postflowering temperatures, three hot days had no effect on oil composition or yield of the two cultivars, except that 37/25C (day/night) from 30-33 DAF reduced erucic acid content of HEAR from 52% to 44%. Severe drought reduced the quality and yields of both cultivars. Erucic acid content of the HEAR cultivar decreased by up to 10% and the oleic acid content decreased by up to 4% with post-flowering drought. Within each year, most variation in the quality components of the three year field trial was due to site. Oil ,content and seed yield were highest, and seed protein content and glucosinolate concentration were lowest, in the cooler and wetter sites and years. Generally, warmer post-flowering conditions enhanced oleic acid content at the expense of linoleic and linolenic acids in the canola quality cultivars, although all regressions between quality and weather variables were fairly weak. In 1995, for. every 5C increase in the average temperature between flowering and maturity, oil content decreased and seed protein content increased by an average 4%, glucosinolate concentration increased by 4.0 ?mol/g, and the linoleic and linolenic acid content each decreased by 1-2% in the different canola quality types. Each 100 mm increase in rainfall between flowering and maturity increased yields by 0.4 t/ha and oil content by 1.6%, and reduced seed protein content by 0.5% and glucosinolate concentration by 1.1 ?mol/g, on average. Oil content was strongly negatively correlated with seed protein content (r=-0.75 for conventional canola). Upon removing the effects of year and cultivar from the ten year dataset, the mean oleic acid content, of conventional canota was very stable across regions, but varied more between years. Canola grown in - central Victoria and the Wimmera produced consistently high levels (>60%) of oleic acid. Canola consistently achieved a low linolenic acid content in central Victoria (<10.8%), and a moderate to low: linolenic acid content in the Wimmera. The Mallee produced canola with highly variable levels of oleic acid and linolenic acid, despite warm post-flowering temperatures which are known to increase oleic acid content. In the three year trial, time of sowing did not have a consistent effect. on the fatty acid composition of canola, probably due to the interactions between temperature and rainfall. These results identified central Victoria and the Wimmera as the most appropriate locations for the production of HOAC and LLAC cultivars. One year of data indicated that Wagga Wagga is capable of producing canola with extremely high oleic acid and low linolenic acid levels. The results of the three year trial identified lower south-eastern South Australia and the Victorian Wimmera as regions most conducive to the production of HEAR with consistently high levels of erucic acid. The erucic acid content of HEAR was often reduced by late sowing. However, this trend was not always observed, and possible reasons for deviations from trends have been discussed. One year of data demonstrated high levels of erucic acid in HEAR produced in the southern part of central Victoria. As the time of sowing did not have a consistent effect on the erucic acid content of HEAR, or the oleic and linolenic acid content of HOAC and LLAC, it was recommended that growers sow at the same time as recommended for conventional canola, to maximise yield and oil content.
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ItemAnalysis of growth and yield in uneven-aged, mixed species eucalypts at Mt. Cole State Forest( 1994)Continuous forest inventory (CFI) is an effective method for studying forest changes over time; it provides growth and yield information which forest planners and managers can use for planning and managing forests to meet long-term sustained yield. This thesis reports results from a 30 year series of successive CFI measurement at Mt. Cole State Forest in west-central Victoria, commencing in 1963. With an area of 12,352 ha, Mt. Cole State Forest consists of three sub areas; the northern and southern Blocks totalling 11,250 ha, and the Mt. Lonarch Block comprised of 1,102 ha. Permanent sample plots (CFI plots) were first established in the Mt. Cole Blocks in 1963 and these have been measured on seven occasions, including the most recent 1994 assessment. During this period, various changes to the inventory data-base have occurred, which have impacted on the analysis and interpretation of the data. Since 1983 the forest area of the Mt. Cole Blocks have been classified according to land use and management zoning, resulting in a reduction of the net productive area available for sawlog production to 2,758 ha. This area has also been stratified into four homogenous areas (strata) and the number of CFI plots has been reduced from an initial 114 to 66 plots. In the latest (1994) remeasurement, the 66 permanent sample plots for the four strata of the Northern and Southern Mt. Cole Blocks were rechecked and the data has been analysed to determine current growth and yield, and to estimate future volume growth and an available cut for the forest. The above analyses show that the structure and yield of the forest have changed from time to time, with a trend towards decreasing levels of available growing stock over time. The current (1994) growing stock levels of the Mt. Cole Blocks are approximately 80,676 m2�27% (P=0.95) or 28.6�3.7 m2 /ha for basal area, and 237,684 m3�36% (P=0.95) or 83.7�13.9 m3/ha for 'sawlog plus potential sawlog volume'. The current available sawlog volume is approximately 177,672 m3�44% (P=0.95) or 63.5�12.5 m3/ha. Additional analyses of periodic and annual growth rates of the growing stock for each stratum and the whole forest (Mt. Cole Blocks) show that the average diameter increment (underbark) of the forest is approximately 0.51�0.03 cm/yr; the net annual increment including ingrowth (Gn+i) of the growing stock in the Mt. Cole Blocks is approximately 0.63�0.11 m2 /ha/yr for basal area, 2.16�0.75 m3 /ha/yr for sawlog, and 1.78�0.68 m3/ha/yr for sawlog plus potential sawlog. The net annual changes in growing stock levels (Gd) are approximately 0.11�0.29 m2 /ha/yr for basal area, -0.15�1.52 m3 /ha/yr for sawlog, and -0.65�1.52 m3/ha/yr for sawlog plus potential sawlog. Models for predicting the current and future growing stock levels were developed using multiple regression based on the three parameters of initial basal area (BO), initial volume (Yo), and the interval of time between successive measurements (t ). Regulating forests to obtain long-term sustained yields requires a continuous flow of information on growth and yield and the development of comprehensive management strategies based on this information. In this study, such growth and yield information have been used to determine an annual available cut for the Mt. Cole Blocks of approximately 5,364�1,854 m3/yr.
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ItemEffect of lupins on the performance of young calves( 1994)This study was conducted to examine the performance of young calves early weaned off milk replacer and fed on starter concentrates containing 0% to 100% lupins. Thirty male Friesian calves aged up to one week old were involved in the experiment. Due to the outbreak of scours, 4 calves died prior to the actual start of measuring at week 4. The rest were allocated at random based on stratified liveweight to 4 treatment diets containing 0, 33, 67 and 100% steamed-flaked lupins fed ad libitum during 28 days of period 1 (preweaning) and 35 days of period 2 (post-weaning). Calves fed 100% lupins completely lost appetite and grew slowly after 6 weeks of receiving experimental diet although the reason for that was not fully elucidated. However, including lupins up to 67% in diets of young calves did not affect the health status, feed intakes, feed efficiency and growth rates (P>0.05). Calves fed diets containing 0, 33, and 67% lupins consumed about 2.5 kg DM/day and grew at approximately 1 kg/day with feed conversion ratios of approximately 2.5 kgDM/kg liveweight gain during the post-weaning period. Plasma and ruminal metabolic measurements were fairly uniform (P>0.05) for these calves indicating they had similar degrees of ruminal development and fermentation. Digestibility of DM, N and NDF decreased (P<0.05) with the increase in proportion of lupins in diets whereas that of ADF showed no significant (P>0.05) difference among treatment diets. The result indicated that steamed-flaked lupins can be satisfactorily included up to 67% in calf starter rations without adverse effect on calf performance. Including lupins at these levels helped cut the feed cost per unit gain weight by 10% compared with using 100% commercial calf pellets.
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ItemGrowth and yield of rice cultivars of differing growth duration in New South Wales( 1993)The growing season for rice in New South Wales is limited by low temperatures in Spring and Autumn. With current cultivars, almost all of the possible growing season is used in producing a crop. Cultivars with short growth duration have been sought by rice growers in southern New South Wales for reasons of decreased water use, increased flexibility in designing rotations and added time for rice field preparation in the event of a wet spring. This study examines the growth and yield of a short-duration cultivar compared with commercial long-duration cultivars, when subjected to a range of fertiliser applications and sowing times. Biomass accumulation of the short-duration cultivar was smaller than that of the long-duration cultivars, however yield potential was similar. This was achieved by the production of similar number of florets/m2 despite smaller biomass at flowering, and greater harvest index. Early sowing resulted in smaller yield due to restricted biomass accumulation and floret production of the short-duration cultivar. The short-duration cultivar had a greater proportion of filled grains and thus yielded more than the other cultivars when sown late. While yield of all cultivars was reduced with late sowing, the short-duration cultivar was affected least. Cultivars of this type are therefore recommended when late-sowing is unavoidable. Variation in yield was not due entirely to low-temperature damage at the critical growth stages of pollen microspore development and anthesis. Yield was also associated with growth after anthesis. A summary model of post-anthesis growth, which included the effect of low temperature on growth, predicted growth with an accuracy similar to that of the growth measurements. Thus, in determining yield, the importance of environmental conditions during grain filling was highlighted. It was concluded that the yield of short-duration cultivars may be less stable when stress occurs during grain filling, because there is less reserve available to fill the grain. Continued work on short-duration cultivars is advocated, with emphasis on faster growth to provide greater biomass production in the shorter vegetative stage. Incorporation of tolerance to low temperatures during the grain-filling stage is also suggested, to give greater yield stability.
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ItemThe effect of fertilizer application on the growth of Eucalyptus globulus( 1992)Blue Gum (Eucalyptus globulus Labill.) fertilizer trials in Gippsland, Victoria were used to relate tree growth to soil chemical parameters and foliar nutrient concentrations. The effects of combinations of N, P, K and trace elements, on selected chemical characteristics of soils and foliage nutrients were compared across three sites covering a range of soil types and climates. The effect of site on soil chemical parameters; soil pH, oxidizable carbon, available phosphorus, available nitrogen, total soil nitrogen, carbon to nitrogen ratio and soil nitrate, was highly significant (p < 0.001). Similarly, the effect of site on foliar phosphorus and potassium was highly significant (p <0 001). Site did not significantly (p < 0.05) influence foliar nitrogen concentration. Height, diameter and basal area were significantly (p < 0.001) influenced by site. Fertilizer addition significantly (p < 0.05) increased available phosphorus in the topsoil of gradational clay loam soils but not in coarse sandy soils. N and P fertilizer addition significantly (p< 0.001) increased foliar nitrogen at all the three sites. Foliar N concentrations are useful in prescribing NP fertilizer requirement across the range of sites studied. Foliar K concentrations were significantly (p < 0.01) increased by NPK fertilizer addition in one of the sites only (Maryvale). Height and diameters of individual trees were significantly (p < 0.001) increased by NP and NPK fertilizer addition in all sites. There was a trend for the response in absolute terms to increase with site quality. Overall, foliar nutrient concentrations were better correlated with growth than soil chemical parameters, and showed great potential for predicting E. globulus response to fertilization at 29 months of age.