School of Agriculture, Food and Ecosystem Sciences - Theses
Permanent URI for this collection
Search Results
1 - 6 of 6
-
ItemNo Preview AvailableQuantitative genetics of wood quality traits in Pinus radiata D. Don(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.
-
ItemChemical treatment of wood and its effect on wood/water interactions( 1999)Wood-water interactions including the effect of grain orientation, sample size and water potential in Pinus radiata D.Don were investigated. The influence of various chemical treatments on the wood-water interaction was also evaluated. The uptake of moisture by wood soaking in water was determined using the water soak method developed by Rowell and Banks (1985). Treatments with surfactants such as ammoniacal copper-didecyldimethylammonium chloride (DDAC-ACQ) and linoleate salts increased the initial uptake rates of the wafers, whilst treatment with copper chrome arsenic (CCA), linseed oil (LO) and a combined CCA/LO treatment reduced uptakes of moisture. The length of time used to assess the water repellent effectiveness (WRE) was found to be crucial to the test, with most of the reduction in WRE occurring in the first 15 minutes of soaking. Exposure of wax treated wafers to weathering indicated an initial gradual reduction in efficacy, which decreased more rapidly as the length of exposure time increased Tests on the effectiveness of different wood coatings subjected to high humidity illustrated the importance of a film with low permeability and some elasticity. Wood blocks coated with resorcinol-formaldehyde resin initially inhibited moisture ingress, but failed after prolonged exposure. An extra coat increased the time required before failure. Coating the wood wafer with a silicone resin slightly reduced the uptake of water into the wafer. However, this resin was more permeable than the resorcinol-formaldehyde resin and was not as efficacious. The effect of various oil treatments on the uptake of water vapour indicated that the distribution of the oil is critical to inhibiting vapour uptake. No significant difference was found between the moisture uptake of hardwood and softwood stakes. Treatment with trimethylborate (TMB), DDAC-ACQ and CCA had no significant effect on the extent of vapour taken up by the wood. An experiment designed to investigate the importance of sample size when assessing wood performance was carried out using matched samples of treated and untreated quartersawn and flatsawn Pines radiata D.Don. It was found that samples treated with DDAC-ACQ and exposed outdoors experienced a greater flux in moisture content compared to controls. CCA reduced the extent of moisture uptake, with the incorporation of oil further enhancing the short term weathering performance. Quartersawn wood exhibited a smaller moisture flux than the flatsawn timber.However, the performance of CCA/Oil treated quartersawn wood was only marginally better than the quartersawn controls. Laboratory trials gave an identical treatment ranking as the exterior trial; however the use of the smaller sample size was identified as being inappropriate for the assessment of check formation in the timber. A sample size effect was demonstrated when assessing the efficacy of treatments by the water soak method. A treatment gradient could be demonstrated when whole stakes were impregnated with CCA and linseed oil by a two-stage process. The test indicated that the significance of improvements in the water repellency of treated wafers diminishes when larger sized samples are investigated. The effect of soil water availability on wood moisture content was determined for untreated hardwood and softwood sticks. At low soil moisture contents, hardwood sticks were found to be significantly more saturated than their softwood counterparts. At higher soil water contents (100% water holding capacity (WHC)) the performance of the two species of wood became less significant. Chemical treatment was found to have a significant effect on reducing wood moisture levels when free water was available in the soil. Linseed oil was responsible for a significant reduction in moisture uptake, by blocking the pathways for water uptake as well as by decreasing the void volume available in the wood for water to occupy. Incorporation of a drying agent did not improve the quality of the film formed by the linseed oil as no significant change in water repellent performance was identified. The uptake and movement of water through a horticultural post was simulated using a procedure described by Baines and Levy (1979). The wick action of heartwood and sapwood stakes of Pinus radiata D.Don was investigated with distinct moisture distribution and behaviours found. Heartwood, being less permeable, showed a reduction in the volume of vapour that moved through the wood, as well as a much lower stake moisture content compared to the sapwood. This difference was most pronounced above the air/water interface and helps to explain the difference in decay resistance exhibited by the two wood types. End sealing the stakes with silicone resin was found to have no significant effect on the wick action of the stake. Lumen filling treatments with wax, oil and alkyd resins were found to significantly alter the wick action of the stakes. Treatment with low concentrations of surface active compounds such as DDAC-ACQ and linoleate soaps were found to increase the rate of water uptake. At higher concentrations the presence of the surfactant increased the hydrophobicity of the wood and reduced moisture uptake. Biological testing using a fungal cellar determined that treatment of the wood with CCA/LO, CCA, DDAC-ACQ/LO, LO and DDAC-ACQ significantly improved the resistance of the wood to decay. The incorporation of linseed oil did not cause a significant improvement to the decay resistance of the stakes over the trial period
-
ItemNutritional physiology of eucalyptus grandis and pinus radiata irrigated with municipal effluent( 1998)The aim of this study is to compare the processes of accumulation and use of N, P, K, Mg and Ca between two and four years of age in plantations of Eucalyptus grandis and Pinus radiata irrigated at several rates with municipal effluent, and with bore water. A series of five harvests over two years was used to estimate above-ground biomass and nutrient content. Growth rate was greater in E. grandis than in P. radiata. Total biomass at 34 months ranged from 34 to 45 t ha-1 in E. grandis and from 21 to 26 t ha-1 in P. radiata, with a trend towards higher rates of growth with increased irrigation rate. Foliage mass and leaf area index (LM) were initially greater in E. grandis than P. radiata. However, the rate of increment in foliage mass and LAI in E. grandis decreased after canopy closure (at about 20 months). At 34 months foliage mass averaged 5.9 t ha-1 in E. grandis and 7.4 t ha-1 in P. radiata. Nutrient accumulation was primarily a function of growth rate, in particular the rate of canopy development. Rate of nutrient accumulation in E. grandis was greatest prior to canopy closure, decreasing thereafter, and in P. radiata it was greatest in the last year. As a result, mean annual increment of nutrient accumulation was maximum in E. grandis at 28 months, and in P. radiata at the end of the study. Implications for management of effluent-irrigated plantations are discussed. The mass of each nutrient accumulated varied greatly and decreased in the order Ca
-
Item
-
ItemAn analysis of radiata pine-pasture agroforestry systems( 1993)Agroforestry, the integration of forestry and agricultural production, requires an understanding of the interactions between trees, agriculture and the environment. This thesis presents an analysis of the effects of a variety of Radiata Pine-pasture agroforestry treatments on soil water, tree growth and form and pasture production together with a series of economic analyses using the FARMTREE model to simulate the various agroforestry regimes established at Carngham in western Victoria. The Carngham study site consists of a replicated randomized block design of five Radiata Pinepasture treatments. The treatments were: open pasture (no trees), 100 trees/ha (8 m x 12 m), 277 trees/ha-wide-spaced (4 m x 9 m), 277 trees/ha-5 row (5 rows, 4 x 3 m, with 10 row gap) and 1650 trees/ha (no pasture). Results, 11 years after tree establishment, show that soil water content under the various treatments has a cyclical pattern of recharge and discharge with an annual amplitude of approximately 100 mm. Within the 100 trees/ha and 277 trees/ha-5 row and 277 trees/ha-wide-spaced treatments, the soil water content was generally significantly less than under open pasture in the upper 170 cm of the upper profile. Within the 1650 trees/ha treatment, the trees utilize water to a depth of at least 270 cm. Tree form was influenced by tree density. Tree diameter decreased but height increased with tree density with the trees of largest volume produced in the 277 trees/ha-wide-spaced treatment. Variable-lift pruning was routinely applied on an annual basis from tree age 6 years, to minimize the internal knotty-core and to maximise the volume of knot-free timber produced. Pruning was virtually completed (to 6 m) after five or six annual treatments, and significant relationships between DOS (diameter over stubs) and various tree parameters were identified as predictors for determining the volume of the knotty-core. Agricultural production was assessed as net pasture production using rising-plate methodology during the major growth seasons. Trees in single rows, as in the 100 trees/ha and 277 trees/ha-wide-spaced treatments, had only a limited effect on net pasture production compared to the zone within 4.5 m from the trees in the 277 trees/ha-5 row treatment where pasture production was significantly less than in open pasture, or in the zone from 4.5 to 18 m from the tree line where there was a possible shelter benefit. Although pasture production was similar between treatments, animal production decreased with increasing tree density. Economic analyses using the FARMTREE model and progressive data from the Carngham trial showed that simulations of the agroforestry regimes at Carngham were more profitable than grazing alone using real discount rates up to 7%. The 277 trees/ha-wide-spaced regime returned the greatest net present values over the range of discount rates used. The optimum rotation length, assuming a 5% real discount rate, was 26 years. Based on the 277 trees/ha-5 row treatment, shelter benefits for agricultural production could be obtained with a distance between belts of 150 to 200 m and by leaving at least 10% of the trees unpruned. The Carngham trial represents one case study of Radiata Pine-pasture agroforestry for south west Victoria. On this basis, the data presented provides information on patterns and trends likely to be encountered in applying agroforestry to other locations in Victoria. The adoption of agroforestry requires ongoing research trials and demonstrations and the Carngham trial has been well planned and maintained and should be seen as a valuable asset for the advancement of agroforestry in Victoria.
-
ItemMethods of improving the preservative treatment of radiata pine and eucalyptus with emphasis on the use of novel boron compounds( 1998)This thesis identifies the effect of raw materials and processing parameters on the application of TMB on wood and wood products. It also describes the effect of TMB on the properties of wood and wood products. This work proposes the application of TMB by momentary immersion following by storage in a close container. The effect of wood moisture content, temperature and time were studied. Low wood moisture content (3%) is required to produce high penetration of the TMB in radiata pine (Pinus radiata D. Don) sapwood. High temperatures (40°C) during storing stage can result in adequate penetration. The storage stage is described in two phases, the emission of chemicals from the wood and the diffusion of the chemical from the head space of the container into the wood. Parameters affecting the process include temperature, wood moisture content and time. Wood moisture contents as low as 3% were found necessary to achieve high penetration of chemicals into wood. During the storage of treated timber, high temperatures reduced the emission and vapour diffusion phases. The levels of TMB and methanol in the headspace of the container were lower at high temperatures. The concentration of TMB and methanol in the head space of the desiccator achieved an equilibrium concentration at 100 hrs for samples stored at 40°C and 200 hrs for samples stored at 20°C. Methanol emission produced by the interaction between water in the wood and TMB was found in low levels. Samples of radiata pine were preconditioned to 3% wood moisture content, treated by momentary immersion in TMB and then stored at 20°C. After vapour diffusion the samples were submitted to an airflow of 0.25 L/min for 24 hrs. Emissions were collected in a water trap. For samples treated at 3% moisture content and stored at 20°C, the analysis showed that only 9.6% of the total production of methanol was found in the emissions. For radiata pine this equals to 28 g/m3/hr. Methanol in the wood is removed easily by water. However a strong bond between wood and methanol is formed. Samples of different species were saturated with methanol and then dried at 105°C for 24 hrs. Twenty nine grams of methanol was found in radiata pine after this process. Pre-conditioning of wood prior to momentary immersion improves the penetration and retention of TMB. Several pre-conditioning processes were studied. Steaming reported better absorption and penetration than microwaving, high temperature and air drying. TMB penetration and a retention of 2.48L/m3 was achieved when steamed radiata pine samples were immersed in TMB for 30 secs. These values were statistically different from values obtained with other processes. Momentary immersion of particleboards in TMB following by a storing stage in a close container was studied. Wood moisture content required to achieve total penetration was 8% for particleboards of thickness 12 and 18 mm. Thicker panels required lower moisture contents. Stiffness (MOE) and strength (MOR) was reduced as maximum as 13 and 17% respectively. Momentary immersion in TMB following by vapour diffusion in a close container was successfully trialed in sapwood of radiata pine, messmate (Eucalyptus obliqua L'Herit), jarrah (Eucalyptus marginata Donn. Ex Sm) and blue gum (Eucalyptus globulus Labill). The effect of non-polar solvents as carriers upon vacuum-pressure impregnation of timber with TMB was studied. Total penetration in sapwood of radiata pine was achieved at wood moisture contents below 14%. The rate of hydrolysis of TMB in non- polar systems was measured and compared with other systems. Non-polar systems have a rate of hydrolysis 26 times slower that polar systems. This allows TMB to penetrate deeper into the timber before hydrolysis begins. Different polymers of trymethylborates were also tested in these systems. Methylpolyborates, a polymer of TMB, were used in the manufacture of pastes and rods for remedial treatments of wood. Methylpolyborates in combination with copper and fluoride compounds were used as active in the manufacture of pastes and rods. Diffusion in stubs of red gum (Eucalyptus camaldulensis Dehnh.) after 60 days demonstrate the feasibility of these TMB polymers as diffusible wood preservatives.