School of Agriculture, Food and Ecosystem Sciences - Theses

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Salinity control, water reform and structural adjustment : the Tragowel Plains Irrigation District

Barr, Neil F. (University of Melbourne, 1999)
Epidemiology of mint rust and variation in the Pathogen, Puccinia menthae Pers

Edwards, Jacqueline. (University of Melbourne, 1998)
Genetics of resistance to Heterodera avenae in Triticum tauschii and its transfer to bread wheat (Triticum aestivum)

Eastwood, Russell Francis. (University of Melbourne, 1995)
Nitrogen dynamics after application of biosolids to a Pinus radiata plantation

Robinson, Michael Barrett. (University of Melbourne, 1999)

The application of biosolids (sewage sludge) to forests has the potential to increase plantation productivity. Environmental damage may result from pollution of nutrients, heavy metals or pathogens contained in biosolids, leaching of nitrogen (N) to groundwater is of particular concern. This thesis examines the rate of release of N from biosolids, its subsequent fate, and those factors controlling storage and loss of N. Integral to the release of N is the decomposition of biosolids, which is examined through the loss of mass, organic matter and carbon. The potential for increased productivity and environmental risk is assessed through comprehensive N budgeting in the ecosystem. The objectives were addressed through a series of field and laboratory experiments. To compare N dynamics, biosolids were obtained from three sewage treatment plants with contrasting processes (one aerobically- and two anaerobically-digested). The core work was carried out in a major field trial, where biosolids were applied to the forest floor of a 22 year-old Pinus radiata D. Don plantation. The experimental rate of application supplied between 965 and 1425 kg ha-1 of N. More than 85% of the NH4+-N applied in biosolids was volatilised in the first three weeks after application. Subsequent rates of volatilisation were small. The magnitude and temporal patterns were confirmed in a separate study. Volatilisation losses reported in the literature are generally much less, highlighting the variability of losses due to differing biosolids chemistry and environmental conditions at application. About 35% of the organic N was released from anaerobically-digested biosolids in the first year after application, and 54% from the aerobically-digested biosolids. These rates are considerably higher than those used in guidelines of the NSW Environment Protection Authority. There were no significant increases in total N in soil after application, but natural variability in soil precluded detection of increases of the order of 100 kg ha-1. Amounts of NH4+-N in soil increased immediately after application, the size and longevity of increases differing among biosolids. One year after application only very small amounts of inorganic N remained in soil. Throughout the trial, concentrations of NO3--N in soil solution at 60 cm in soil remained consistently below drinking water standards under the anaerobically-digested biosolids and consistently exceeded drinking water standards under the aerobically-digested biosolids. Loss of N in drainage below 60 cm depth in soil in the first year after application was about 20 kg ha-1 under anaerobically-digested biosolids and about 100 kg ha-1 under aerobically-digested biosolids. A controlled incubation study demonstrated that patterns of N mineralisation in the field could not be predicted from laboratory incubations. However relative rates of N mineralisation correlated with amounts of N leached in drainage. Application of biosolids significantly increased tree growth (20 - 34% in basal area) by the second growing season after application. Such a response is likely to be maintained for several years. Rates of volatilisation and mineralisation need to be considered when determining rates of application to ensure that the capacity of soil and plants to store N is not exceeded. Application of anaerobically-digested biosolids at 30 dt ha-1 can increase plantation productivity with minimal risk of groundwater contamination by N. Repeat applications at the same rate concomitant with plantation thinning operations should improve productivity and soil fertility with minimal risk of groundwater contamination.
Quantitative genetics of wood quality traits in Pinus radiata D. Don

Nyakuengama, John Gwinyai. (University of Melbourne, 1997)

In order to understand the variability of traits important in pulping and sawn timber (heartwood formation, moisture status, density and fibre cross-sectional dimensions, fibre coarseness and fibre specific surface), wood from 4 radiata pine (Pines radiata D. Don) plustrees, including parent 80055, and their progeny comprising of a small 4 x 4, 23 year-old, unthinned, diallel progeny test was studied. 80055 progeny is renowned for consuming low energy and producing bright newsprint during thermomechanical pulping. However, the newsprint is of low tear strength. No reciprocal or maternal effects were found in all the traits, probably because of the small number of reciprocal pairs in the diallel experiment. Otherwise, results imply that future wood quality experiments could be simplified by excluding reciprocal crosses. The study found that the o-anisidine and sodium nitrite method was useful to differentiate heartwood formation from sapwood in studies involving a large number of samples. A low narrow sense heritability (NSH) was found for heartwood and its formation was accompanied with a decrease in moisture content. This accounted for a strong inverse correlation found between heartwood formation and moisture content. 80055 progeny had the most heartwood and this explained why its corewood was the driest in the diallel experiment. Technologically, drier heartwood is undesirable in refining because its pulp fibres have a lower wettability, are more brittle and produce newsprint of inferior strength and lower brightness than wetter sapwood. Wood microstructure was studied using a recently commissioned Silviscan 1 system which incorporates an X-ray densitometer and video-microscope. Protocols were set up in this pioneer study for future CSIRO-Forestry and Forest Products progeny tests (and silvicultural studies). Area-weighted fibre size (ie., fibre perimeter, fibre radial and tangential diameters) and density had the highest NSH among traits but these had large standard errors due to a narrow genetic base. The NSH of fibre coarseness was intermediate while those of area-weighted fibre wall thickness and ring width were the lowest. Additive genetic variance was high in all arbitrary classes of fibre diameters, unlike in density and fibre coarseness where it was high in all but an intermediate class representing the transition zone between earlywood and latewood. 80055 progeny had the least dense wood and the highest fibre coarseness in the diallel experiment on account of possessing the largest amount of fibres with large diameters (tangential and radial) or earlywood (as defined as wood with a density less than 400 kg m-3). Technologically, this wood microstructure could translate to low strength in sawn timber. Density and fibre traits had different genetic structures, which accounted for difference in age-age correlations and selection efficiencies at a juvenile age in relation to those at a mature age in these traits. Results indicate that fibre coarseness increased with fibre size only, in 80055 progeny. Fibre coarseness increased directly with increases in fibre wall thickness only in progeny of other parents. Technologically, this implies that fibres of 80055 progeny have thinner fibre walls at a comparable fibre coarseness than non-80055 progeny. This finding could explain why make 80055 fibres make somewhat weak refiner pulp. NSH estimates of density and fibre traits calculated in whole-cores and individual growth rings from parent-offspring regressions were generally more conservative than those from sib analysis of the diallel progeny test but the magnitude of estimates was comparable. Despite large standard errors associated with NSH estimates which were caused by the narrow genetic base of the study material, estimates tended to differ between traits and with physiological and chronological age of parents and offspring. A holistic study based on principal component analysis concluded that fibre diameter and fibre coarseness, but not density, were directly related to tree height and diameter (growth traits). Heartwood formation was directly related to the growth traits, implying that selection of one trait would influence the other.
Sexual dimorphism of the somatotropic axis in growing lambs

Gatford, Kathryn Leanne (University of Melbourne, 1995)
Soil water and nitrogen dynamics of dryland wheat in the Victorian Wimmera and Mallee

O'Leary, G. J. (Garry John), 1953- (University of Melbourne, 1994)

In semi-arid environments where water supply is the major factor limiting grain yield, the agronomic option of fallowing provides a way to increase water and nitrogen (N) supply. A study was carried out for four years at two sites in semiarid, north-west Victoria, Australia to examine the effect of fallow management on water and N supply at sowing and their subsequent effect on growth and yield of wheat. The fallow treatments comprised the four combinations of stubble management (retention - SR, removal - NS) and tillage (frequent - CT, none - NT) in year-long fallows of a fallow-wheat rotation (i.e. SRNT, SRCT, NSNT and NSCT), together with a tilled summer fallow prior to alternating pea and wheat crops (PeCT). The two sites, which have different rainfall, represent the major soil types of the region; a chromic vertisol at Dooen and a calcic xerosol at Walpeup. At Dooen, grain yield provided a diverse response to fallow method that generally reflected biomass response and water use. NSCT increased yield every year over PeCT by an average of 0.9 t ha-1 (range 0.5 to 1.3 t ha-1). Stubble retention (SRNT and SRCT) further increased yield above the non-stubble fallows (NSNT and NSCT) in three of the four years, averaging an additional 0.56 t ha-1 (range; 0.24 to 1.04 t ha-1). At Walpeup, NSCT increased yield above PeCT in two years, by 0.7 t ha-1 from 2.6 to 3.2 t ha-1 in 1990 and by 0.6 t ha-1 from 1.7 to 2.3 t ha-1 in 1991. Stubble retention increased yield by 0.45 t ha-1 in only one year, 1988, and that was without tillage (SRNT). Zero tillage did not have any independent overall effect on yield. Crops responded differently to the distinct soil conditions at each site. At Dooen, NSCT increased soil water storage at sowing by an average of 76 mm (range 24-122 mm) above PeCT. Stubble retention added a further 52 mm (range 36-65 mm). Zero tillage was slightly beneficial, and was enhanced by the presence of stubble. Similarly, at Walpeup, NSCT provided an average of 37 mm (range 23-56 mm) more water at sowing than PeCT. SRNT increased water storage by 27 mm in only one year. Fallow and its surface treatments provided large differences in soil mineral nitrogen (SMN) accumulation, but levels were generally sufficiently high (66-222 kg N ha-1) to not greatly affect yield. At Dooen, NSCT accumulated 46 kg N ha-1 more SMN than PeCT, whereas at Walpeup PeCT increased SMN in two years by an average of 46 kg N ha-1 above NSCT. At Dooen stubble retention depressed SMN by an average of 26 kg N ha-1 in two years and in one, increased it by 20 kg N ha-1. Stubble retention had little effect on SMN at Walpeup. A simulation model was developed to apply the responses of the field experiment to a wider range of weather conditions. It includes soil carbon (C) and N and crop N submodels. The model showed a pattern consistent with observed response. Validation showed that soil water was simulated more accurately than SMN (R2=0.95 cf. R2=0.61), and there was no significant bias in any fallow treatment. Crop biomass followed the general pattern of observations throughout the season well (R2 =0.77). Grain yield was simulated with less accuracy than biomass (R2 =0.42) and was shown to be largely due to poor simulation of grain number (R2 =0.07) because accuracy of yield prediction was markedly increased (R2 =0.59) when predictions were made on observed grain numbers. Grain [N] was simulated with fair accuracy (R2 =0.29), pointing to the need for improvements not only in the simulation of grain size (R2=0.61), but also in the partitioning of N to grain. Overall, the performance of the model is comparable to the CERFS-Wheat-N model even though it is less complex. Analyses with the model over long-term weather conditions supported the field observations of the advantage of stubble retention in predicting a median increase in yield of 0.8 and 0.6 t ha-1 at Dooen and Walpeup, respectively. However, at Walpeup, field observations indicate that other factors may limit this advantage. Zero tillage had a small advantage in the presence of stubble (0.2 t ha-1) with no consistent advantage without stubble at Dooen nor under any system at Walpeup. The model displays a general level of behaviour known to occur in the field and provides a useful tool, not previously available, to examine water and N interactions in conservation tillage systems in north-west Victoria. The model should have relevance in other semi-arid environments where wheat is grown.
Villager participation in native forest development : the impact of social forestry in Fiji

Vize, Susan Maree (University of Melbourne, 1993)

As owners of extensive forest resources, the Fijian people have an opportunity to utilise these resources for village development. Villagers are very conscious of their low living standards compared with urban areas. It is widely accepted that expanding local employment and business opportunities is necessary to improve rural living standards, and rural Fijians hope that the forest industry will help them to achieve this. The object of this research project is to evaluate the success of social forestry as a methodology for achieving village development in Fiji, particularly the contribution of Fijian villager participation in the native forest industry. Forestry activities earn cash benefits for rural villagers in the forms of land rentals and timber royalties. Social forestry programmes involving villager participation in planting projects were seen as way to enhance rural development. To further increase the benefits obtained from forestry many Fijians have become actively involved in forest harvesting and timber processing. Though there is a high potential for achieving significant benefits by Fijian participation in the forestry industry, the actual benefits received are determined by the type of activity, the level of participation and the performance of the participants. The study involved surveying in seven villages on the islands of Viti Levu and Vanua Levu, as well as short interviews with many Fijians involved in the forest industry. The villages covered a range of villager forestry participation types, including casual and contract employment in logging or planting, village community fund-raising contracts, a proposed joint venture logging project and a small logging company. 'Development' appears to be fairly consistently interpreted across rural Fiji as the improvement of village services and homes; hence in the eyes of the villagers, forestry does contribute to development. The surveys show that forestry can make a significant contribution to the village economy in the form of cash and employment, but the contribution of forestry towards village development is dependent upon the use of the income generated from forestry. These uses vary between the villages, but commonly include the purchase of consumables, such as food and tobacco, paying school fees, home improvements, roads, churches, schools, and other communal amenities. There is a significant difference in the contribution of forestry to employment and income between the two islands; forestry is more important in rural development on Vanua Levu. Social structure in the village, village leadership, assistance from government or financial advisers, and the level of integration of the village into the market economy, all appear to affect the investment and management of forestry funds. These aspects exert the most influence on the amount of 'development' that can be achieved through forestry programmes involving Fijian landowners. Logging businesses achieved higher cash returns than other types of Fijian forestry participation, but were plagued by difficulties. Businesses in logging, sawmilling and manufacturing of higher value-added products such as veneer and furniture are the most profitable area of the forest industries in Fiji. The potential for Fijian villagers to become involved in these enterprises is severely limited by access to credit as well as their paucity of management and administrative skills. But where the potential for forestry participation exists and motivation is provided by a community leader or individual, social forestry activities can effectively promote rural development and viable village communities in Fiji.
Estimation of timber volumes in eucalypt forest using large-scale aerial photography and ground samples

Biggs, Paul Haydn (University of Melbourne, 1991)

This study investigated the use of large-scale aerial photographs (1:1200) for estimating timber volumes in eucalypt forest in Western Australia. The aims were to determine the optimum photography system for estimating timber volumes in jarrah forest, to derive appropriate aerial volume functions, and to investigate the efficiency of different sampling designs using aerial photographs. Photographs were acquired using a fixed-base photographic system, the cameras being mounted on a transverse boom on a helicopter. Two types of cameras, Vinten and Hasselblad, were tested. Measurement of the Vinten photographs using simple stereometers provided estimates of tree heights with a standard deviation of 1.7 m, while the standard deviation of measurements on Hasselblad photographs was about 2.0 m. These results are slightly poorer than results achieved by others in coniferous forests, the reason being attributed to imprecision of the ground "truth" rather than poor quality in the photographs. The accuracy of species interpretation was 85 percent on all photographs. It is expected that more precise measurements could be obtained using analytical plotters to measure Hasselblad photographs. Hasselblad 500 EL/M cameras used in the present study were fitted with reseau plates and were calibrated to facilitate analytical measurement. Results showed, however, that further research is required into the process of exterior orientation with such large-scale photographs with a very small air-base/flying height ratio. A system of navigation and camera-control was built specially for this project using a Global Positioning System (GPS) receiver and a laptop computer. This system was used to navigate during photography and to determine the location of each pair of photographs on maps and in the field. Its use led to efficient in-flight navigation and ensured that photographs were taken on a fixed-distance interval. Ground plots could be located quickly in the forest using this system, as the actual photo-centres were generally within 50 m of their surveyed position based on GPS coordinates. Sample data from both photo and ground plots were stored in a Geographic Information System (GIS) database, which allowed them to be linked with other spatial data. Using this system, volume statements could be derived for any part of the forest by defining the relevant geographical zone and then identifying the plots within that zone. Any change in the available land base could also be accomodated, simply by redefining the zone of interest and reselecting the sample plots. Aerial tree volume functions derived for different species in the jarrah forest used the total height of each tree and the dominant height of the stand as independent variables. Separate functions were derived for different areas of forest by applying a nominal dominant height value in a general volume function, while another set was derived by stratifying the original sample plots. It was found that the volumes of very large trees were greatly underestimated when their crowns had been damaged, and that this factor swamped the difference between the two types of volume functions. The underestimates of photo volume caused by the damaged crowns of large trees had the effect of reducing the correlation between the photo and ground samples to about r=0.65. The cost of each photo plot was about $30 and the cost of each ground plot was $280. The combination of these costs and correlation meant that double sampling for regression could provide estimates of volume at the same cost and precision as ground sampling. Further research should, however, investigate ways to improve this correlation to about r=0.75, which would then make double sampling with large-scale photographs cheaper than ground sampling.
Tribes and territories : aspects of Aboriginal political geography in the Northern Territory of Australia

Davis, Stephen, 1951- (University of Melbourne, 1989)

School of Agriculture, Food and Ecosystem Sciences - Theses

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