School of Agriculture, Food and Ecosystem Sciences - Theses
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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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ItemPhosphorus and potassium sorption characteristics and their relation to seedling growth in a highly weathered kaolinite soil( 1993)P and K sorption characteristics for a highly weathered kaolinite soil are studied in this thesis and related to growth responses in a three month seedling glasshouse experiment, using E. globulus spp. pseudoglobulus. The phosphorus supplying capacity of the soil was estimated using the principle of amount sorbed versus solution concentration. P sorption characteristics were described according to the Langmuir sorption isotherm. The sorption maximum of 70.4 ?g/g was low, indicating that large applications of P fertilizers are not required to overcome unfavourable sorption of P for this soil. Exchangeable and solution potassium of the soil were characterized by Quantity/Intensity relations utilizing activity ratios. The potential buffering capacity for the soil obtained from the Q/I curve of 8.28 (me/100g)/(M/I)1 /2 was low showing the soil to be poorly buffered against potassium depletion. Seedling growth under factorial additions of P and K showed response to P but not to K addition. There was no significant interaction between P and K addition. Concentration of P in foliage, stems and roots increased with increasing P addition, with over 90% of the increase occurring at the rate of addition equivalent to the Langmuir sorption maximum (70.4 ?g/g). The soption isotherm approach was found to be of value to predicting P fertilizer requirement over the first three months of growth. K concentration in the tissues were not related to rate of K fertilizer addition.