School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemStain development in Victorian hardwoods( 1996)Fungal stain in value added hardwood has resulted in the loss of millions of dollars in downgraded timber over the past few years in Victoria (Vinden 1994). The causes of fungal stain in Victorian hardwoods, particularly Eucalyptus regnans and Eucalyptus delegatensis, were determined at J.L. Gould Sawmill in Alexandra, Victoria. Systematic sampling of the logs in the log pile under sprinklers revealed a complex ecological niche of fungi, many of which are capable of causing stain. Further studies on logs with incipient decay identified Penicillium glabra as the fungus potentially responsible for the yellow stain and Ophiostoma sp. as the fungus potentially responsible for the black stain. A mill audit pinpointed areas in the processing procedure in need of improvement. Log storage times must be radically reduced and storage facilities must be improved to provide an environment that does not encourage fungal growth. A study concentrating on the moisture content of logs in the log pile also revealed the need for an improved water sprinkling system. Proposals to counter the stain problem include improving control measures, implementation prophylactic treatment after log sawing, and further research into biological control in the log pile.
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ItemVariation of some vessel characteristics of plantation Eucalyptus regnans F. Muell( 1993)Some vessel characteristics of six 15-year old plantation grown Eucalyptus regnans F. v. Muell. trees from a progeny trial in Narbethong, Victoria were studied. The within and between tree variation of vessel frequency and percent tyloses with distance from the pith, between six heights and between the six trees was examined. Vessels and vessels containing tyloses present on the cross-sectional surface of 7 mm by 7 mm wood blocks taken from pith to bark were counted using a stereo zoom microscope. Analysis of variance was used to examine the variation of vessel frequency and percent tyloses with: distance from the pith; between the north and south axes; between the base, breast height, 20%, 40%, 60% and 80% of total tree heights; and between the six trees. Data in graphical form coupled with microscopic observations were used to examine the within and between growth ring variation. The overall mean vessel frequency for the six 15-year old trees was 7.885 vessels/mm2. Variation of mean vessel frequency with distance from the pith, between heights and between trees was statistically significant. However, after area weighting the vessel frequency values, there was not a significant difference between trees. Mean vessel frequency generally increased with height, with means of 7.100 vessels/mm2 at the base and 10.722 vessels/mm2 at the 80% height, and decreased from the pith to the bark. The variation between axes and with all interactions between the main factors were not significant. Vessel frequency was observed to vary within and between growth rings. Vessel frequency was lowest in the region at the latewood to earlywood boundary and highest in the central portion of the growth ring. Vessels containing tyloses were found at all six heights of all six trees and the mean percent tyloses for the six trees ranged between about 7 to 18%. The variation of mean percent tyloses with distance from the pith, between heights, between trees and the interaction between height and tree was statistically significant. The percent tyloses was lower in the region near the pith and in the sapwood region near the bark and highest in the central region between the pith and the bark. The percent tyloses varied between about 10 and 40% in a cyclic or wave-type manner over distances of about 10 to 15 mm from pith to bark but did not appear to be related to vessel frequency. The mean percent tyloses showed a general decrease with height, with the base height having a mean of 20.387% and the 80% height a mean of 6.448%. The largest tree mean was 17.568% and the lowest was 7.219%. The relative magnitude of the mean percent tyloses at each height and the ranking between heights varied between trees. For all six trees the frequency of vessels was greater toward the top of the trees but fewer vessels contained tyloses at these upper heights. It may be that timber removed from the upper portions of the stem might be more permeable to liquids such as in the preservation and pulping processes and may release moisture upon drying more easily.
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ItemWood characteristics and properties of plantation mountain ash (E. regnans) and their variation( 1992)Six 15-year old Eucalyptus regnans F.Muell trees from three seedlots in a progeny trial in Narbethong, Victoria were examined in this study. Wood discs were removed from the base, breast height, 20 %, 40 %, 60 % and 80 % of the total tree height. Three methods used to demarcate the boundary between the sapwood and heartwood on the disc cross sectional surface were examined. The first method was based on the difference between sapwood and heartwood. The second method which was based on the difference in pH between sapwood and heartwood used 0.1 % methyl orange stain. The third method which was based on the presence or absence of tyloses in the vessels used a light table. Measurements were also made on the cross sectional surfaces of the discs to determine the sapwood width, heartwood percent, and the number, length and year of formation of each kino vein. The presence of decay and discolouration was also noted. Sapwood and heartwood wood blocks were cut from discs along the four cardinal directions. The basic density and moisture content of all wood blocks from the four axes and the remaining pie shaped pieces from each disc were determined. Mean basic density and moisture content based on the wood blocks from only the four axes were also computed. No difference was found in the demarcation of the sapwood-heartwood boundary between the methods based on natural colour and stain. Demarcation of the boundary using the light table method gave significantly different results to those found for the colour and stain methods. Based on the light table results, the presence of the tyloses appears to vary greatly between the base and breast height while at the 20 %, 40 and 60 heights they are more uniformly distributed. The mean sapwood width varied significantly between trees with values ranging from 24.2 mm to 28.7 mm with on average about four to five growth rings present in the sapwood zone. The mean sapwood also varied significantly with height. The lowest mean sapwood width of 21.0 mm was found at breast height and the mean sapwood width increased to 33.9 mm at the 80 height and increased from breast height to 29.9 mm at the base of the tree. The mean heartwood percent varied significantly between trees and with height. Two trees from seedlot number 13 had a mean heartwood percent of about 42 which was about 6 % lower than the mean heartwood percent of about 48 for the two trees from from seedlot number 23. The largest heartwood percent of 69.51 was found at the breast height and decreased to 0 (zero) at the 80 height and also decreased from the value at breast height to 65.75 at the base of the trees. A correlation of 0.967 was found between heartwood diameter and disc diameter. Kino veins were found in all six trees with the earliest formed vein at the tree age of 4 years. For the six trees, the total number and average length of kino veins decreased with height. The average length varied greatly between trees while the total number of kino veins was relatively uniform in five out of six trees. The presence of decay and discolouration was noted in five out of six trees. Basic density varied significantly between trees and with height but not between the sapwood and heartwood which had mean basic density values of 0.430 g/cm3 and 0.435 g/cm3 respectively. The mean basic density of 0.408 g/cm3 was lowest at breast height and highest at 80 height where the mean basic density was 0.468 g/cm3. Tree number 2 from seedlot number 13 had the highest mean density of 0.486 gm/cm3 and this was significantly greater than the lowest value of 0.422 g/cm3 found for tree number 4 from seedlot number 23. The interactions between trees and heights and between heights and axes were also found to be significant. Moisture content varied significantly between trees and with height but not between the north, south, east and west cardinal directions which had mean values of 146.98 148.47 %, 148.91 and 151.15 respectively. The mean moisture content at breast height was the highest with a value of 161.14 and the lowest value of 134.33 was found at the 80 height. Tree number 2 had the lowest mean moisture content of 127.65 and tree number 5 had the highest value of 161.05%. The interactions between heights and locations (sapwood or heartwood) and between axes and locations were significant. A correlation of -0.923 was found between moisture content and basic density. The mean basic density values and the mean moisture content values determined from blocks removed along only the four axes were strongly correlated to the weighted disc values based on virtually all the wood from each disc.
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ItemEfficiency of mechanised ash thinning( 1993)This is a study of the fully mechanised thinning of young (15 to 25 years old), regrowth stands of high quality ash species. The study quantifies the productivity of the harvesting operation, the amount and distribution of traffic across the coupes, as well it describes the changes that occur to components of the forest floor. Strategies are put forward, that if implemented would provide gains in the economic and environmental efficiency of similarly executed ash thinning operations.