School of Ecosystem and Forest Sciences - Theses

Permanent URI for this collection

Search Results

Now showing 1 - 10 of 11
  • Item
    Thumbnail Image
    Effects of adding nutrients on soil chemistry and tree growth in native Eucalyptus forests of south-eastern Australia
    Severino, Dean Christopher ( 2007)
    The decreasing area available for timber extraction in south-eastern Australia, due largely to social pressure to reserve greater areas of forest, has led to the consideration of fertiliser-application to increase wood output from the remaining available forest. Potentially deleterious effects of fertilising on water quality must be assessed before implementation on a wide scale. This is in accordance with relevant forest management policies. This study examined the effects of applying fertilisers containing nitrogen and phosphorus, on soil and soil-water chemistry in two pole-sized stands of mixed Eucalyptus spp in the Wombat Forest, in the Midlands Forest Management Area, Victoria, Australia. The findings are synthesised and discussed in relation to management of regenerating mixed-eucalypt forests in south-eastern Australia. Fertiliser treatments were none (R); 400 kg N ha-1 as ammonium-sulphate (N); or 400 kg ha-1 plus 202 kg P ha-1 as triple superphosphate coated with 10% sulphur (NP). It was calculated that incidental additions of S were 1371 kg ha -1 (N treatments), and 1696 kg ha-1 (NP treatments). It was expected that P would be principally adsorbed on soil surfaces; N immobilised in the soil organic pool and that metallic cations would enter the soil solution to varying degrees. Fertiliser-addition increased both plot-basal-area (BA) growth and the rate of stand self-thinning. In 3.8 years, BA in reference (R) plots at two sites increased by 7.3% and 23.4%. Where N alone was added, BA increased by 14.2% and 27.1%, while in NP plots BA increased by 17.1% and 42.7% respectively. Mortality was 9% in untreated plots compared to 14% in NP plots. Estimated increases in biomass growth equated to additional above-ground nutrient accumulation of 0.4 to 1.5 kg ha-1 of P, and 5.5 to 20.8 kg ha-1 of N. This represented only 0.2 to 0.7% of added P, and 1.4 to 5.2% of added N. Soil solution was extracted from 10 and 50 cm with porous-ceramic-cup tension-lysimeters (-0.6 kPa). Concentrations of P and N were low both before and after adding fertiliser. Across all treatments the maximum median PO43- concentration in soil-water at 50 cm was 0.12 ppm (mean 0.28 ppm). Typically PO43- concentrations were not higher than 0.03 ppm. The 400 kg ha-1 of added N was rapidly immobilised in the soil organic pool. The greatest mean NH4' concentration from a single sampling occasion was 1.1 ppm. The mean NO3 concentration at 50 cm was never higher than 0.26 ppm. After adding N in fertiliser the proportion of NO3- relative to NH4* in soil-water increased and was correlated with decreasing soil-water pH. Less than 1% of added P and N was recovered from soil solution at 50 cm. The largest pool of added P recovered was PO43- adsorbed to soil between 0 and 20 cm, due to the soil adsorption capacity being well in excess of the applied 202 kg P ha-1. Phosphate desorption using sequential extractions with a mild acid extractant (0.3M NH4F, 0.1M HCI) recovered between 25% and 116% of added P. Differences were attributed to both the amount of P added and the effect of time since treatment at different sites. Soil disturbance during sampler installation was found to be more likely to raise soil-water P concentrations at 50 cm than would adding up to 202 kg P ha-1. Among the ions in solution. SO42- and CI' were the dominant anions while Cat+ dominated the cation chemistry. In untreated forest 5042- in soil-water ranged from 7.7 to 16.0 ppm at 10 cm and 7.9 to 12.2 ppm at 50 cm. In fertilised plots up to 100.5 ppm SO42 was measured in soil-water at 50 cm depth. In the N treatment at 50 cm, SO42- in soil-water accounted for 9.4 % of applied S. compared to 14.0 % in NP. In untreated forest, soil-water Cl- and SO42- accounted for over 98% of the total soil-water anions, in roughly equal proportions at 10 cm, and CI- slightly higher at 50 cm. Following fertiliser-application soil-water pH at 10 cm fell from 6.3 in R to as low as 4.81 (N) and 4.45 (NP). At 50 cm pH never dropped below 6 and there were no visible departures from reference concentrations. Relative activities of K+ and Mg2+ in solution increased with decreasing pH, indicating increased leaching potential. Sulphate in soil-water increased total anion charge further in NP than in N. Total charge (cmolc L-1) for cations followed anions. A slight deficit in anion charge was likely due to the unquantified contribution of organic anions. These results confirm that despite the quantity of fertilisers added in this trial being double likely operational quantities, the forest and associated soils had the capacity to retain these nutrients through a variety of processes. The study validates the environmental sustainability of proposed intensive management practices including fertiliser-application in this forest type. It also emphasises the importance of understanding fundamental forest nutrient cycling processes when aiming to carry out intensive forest management practices in an environmentally sensitive manner.
  • Item
    Thumbnail Image
    Effects of salinity on growth and wood and fibre properties in eucalypts
    Catchpoole, Stephen John ( 2001)
    Salinity, the presence of soluble salts in soils or waters, can be separated into naturally occurring primary salinity, and secondary salinity resulting from human activities such as land development and agriculture. Secondary salinity involving high, saline water-tables affects large areas, estimated between 4.7 and 6.1 'ha (Williamson 1990, Robertson 1996), of agricultural land in Australia, and tree planting is one approach to lower saline watertables. Such plantations could become a significant fibre source for the pulp and paper industry, but it is not known whether growth in salt-affected environments influences key fibre properties important in paper production. This work therefore examined the wood and fibre properties of Tasmanian blue gum, Eucalyptus globulus ssp. globulus, and river red gum, E. camaldulensis, grown under various conditions of soil salinity. Eucalyptus globulus was studied in trial plantations in the Shepparton region of north-central Victoria. The plantations were established in 1993, and field sampling was carried out from 1995 to 1997. Salinity in the top 20 cm of soil over the period of study (1994 to 1997), according to the soil salinity classes set lutin Marcar et al. (1995), ranged from non-saline at the fresh-channel water-irrigated plot to slightly saline for the saline groundwater-irrigated plots. Tree size generally did not differ significantly between plots at any age. Differences in foliar [Na±], {K±] and [Cl-] occurred between the field plots but were not consistent between years. The highest concentrations of foliar ions were also not always associated with the plot receiving the highest salinity irrigation water, suggesting that in only some years was the soil salt level sufficient to cause a plant response. Wood basic density differed between the plots, but it could not be attributed to salinity, and may have reflected other site-specific effects. Fibre morphology parameters did not differ significantly between the plots. There were some differences between the plots in the increase in fibre length from year to year but the differences were not consistent over the entire survey period and could not conclusively be attributed to differences in soil salinity. A pilot salinity pot trial was conducted on E. camaldulensis plants, as a precursor to a more elaborate experiment planned for potted E. globulus plants. The E. camaldulensis pot trial comprised a single concentration salt (NaCl) treatment and a control (freshwater) treatment applied over a 60 day period. A marked reduction of growth occurred with salt-treated seedlings relative to control seedlings. Concomitant with the reduction in growth, salt-treated seedlings produced significantly shorter, thicker-walled fibres than the control seedlings. The pot-trial on 18-month-old Eucalyptus globulus ssp. globulus trees applied different concentration salt (lRlaCi) solutions over a 10-week period. The salinity of the potting mixture increased markedly in the salt-treated trees relative to the controls. Foliar chloride and sodium were also significantly greater in trees on the higher salt treatments than in the control trees. Diameter growth decreased with the higher salt treatments, and five trees under high salt treatments had to be harvested prior to the planned completion of the experiment, due to their poor state of health. These results indicated the salt treatments had influenced some aspects of tree physiology. A wound made to the cambium allowed pre-treatment fibres (fibres formed prior to the start of the experiment) to be distinguished from post-treatment fibres (fibres formed during the experiment) in the E.globulus pot trial. Trees on higher salt treatments produced significantly longer, thinner-walled fibres compared to controls, but this pattern also occurred in fibres formed before treatments were imposed, implying that these differences were due to preexisting differences in the trees unrelated to the salt treatment. Statistical analysis of fibres formed during treatments, taking account of pre-existing differences, found that there was no significant effect of salt treatment on fibre length or wall thickness, although this was possibly because of the low sample size relative to the variation of the experimental material. The controlled application of salt for 10 weeks during the E. globulus pot trial thus had some effect on tree physiology, but no significant effects on fibre dimensions or wood formation. This was consistent with the observation in the field trial that fibre dimensions and wood formation were not influenced by factors that did not also reduce tree growth, at least in trees up to 4 years old. Higher levels of salt could cause rapid tree decline due to the inability of the trees to exclude the salt, and processes associated with fibre formation would then also cease. The combined results from the field and pot trials indicated that E. globulus, a slightly to moderately salt-tolerant species, suffered negligible or minor growth reductions on soils irrigated to a slightly saline level, and produced fibres of similar morphology to trees grown under non-saline conditions. If soil salinity increased above the moderate level, the trees would continue to grow provided sufficient water is still available, but internal salt levels would increase to the point where tree death would result. Based on the pot trial, where such internal salt levels were achieved, the decline and death of the trees would occur before the salt affects fibre morphology. Eucalyptus camaldulensis adopted a different strategy to cope with salt stress than E. globulus. Eucalyptus globulus continued to grow provided it was supplied with water, despite its saline nature. Finally, when salt levels within the plant reached a critical level, plant health rapidly declined. When E. camaldulensis was watered with solution of a similar salinity to the highest salt treatments in the E. globulus pot trial, there was a rapid cessation in extension growth, but there was no other sign of a deterioration in plant health. The mechanism by which E. camaldulensis was able to quickly cease shoot growth, which presumably allowed it to tolerate saline conditions by restricting salt uptake, was not investigated here. Material from Eucalyptus camaldulensis that had been growing for 14 years on a dryland plantation site in southwest Western Australia was also investigated. Trees from the high salinity area did not differ significantly in average height, diameter and volume from those from the low salinity area. Basic density were significantly greater in the high salinity group of trees than in the low salinity group, but no relationship with tree growth was established. The absence of a relationship between growth and basic density was not unusual, as natural variation in basic density makes it difficult to establish environmental or experimental effects (Downes and Raymond 1997). Fibre fractional wall coverage was greater in the high salinity group of trees than in the low salinity group, as was also the case for the E. camaldulensis pot trial. In the pot trial, however, a significant growth reduction due to salinity was recorded. There were no other differences in fibre morphology between the high and low salinity groups of the Western Australian plantation. Eucalyptus globulus is less salt and waterlogging tolerant than E. camaldulensis (Bennett and George 1995a; Bennett and George 1995b) but in the field studies the growth and wood and fibre properties for each species was similar across the range of salinities encountered. The exception was basic density and fibre fractional wall coverage in the 14-year-old E. camaldulensis, both of which were greater in the high salinity group of trees. It was expected that the growth of E. globulus would be adversely affected if irrigation with the saline groundwater continued for several more years, allowing a build up in soil salinity. Based on the results from the E. globulus pot trial, once soil salinity levels exceed the tolerance limits of this species, a rapid decline in tree health will occur, and fibre formation will cease. Eucalyptus camaldulensis, with its greater salt and waterlogging tolerance, will grow in areas where other commercial species, such s E. globulus, would not thrive. However, E. camaldulensis has disadvantages for farm forestry in Australia, due to low percentage pulp yields by comparison with E. globulus (Arnold et al. 1999), and poor growth rates and tree form (Mazanec 1999). In the USA, E. camaldulensis has equalled the pulp yield of the commercially proven E. globulus (Arnold et al. 1999). Further research into improving pulp yields, growth rates and tree form of E. camaldulensis in Australia, would allow expansion of eucalypt plantations for pulp and wood production, as well as land and water care, onto previously unsuitable land.
  • Item
    Thumbnail Image
    Physiological aspects of root growth of Eucalyptus pauciflora, subsp. pauciflora and Eucalyptus nitens
    Halter, Reese ( 1997)
    This thesis examined i) morphological and physiological effects of low soil temperatures on root growth of subalpine Eucalyptus pauciflora Sieber ex Sprengel subsp. pauciflora and montane Eucalyptus nitens (Deane & Maiden) Maiden, ii) determined the variability, and in particular the day/night variability, in root elongation, and iii) explored the physiological basis for such variability. A series of experiments were undertaken with seedlings of E. pauciflora and E. nitens grown at soil temperatures of 3, 7, and 13C, and where seedlings were transferred from one temperature to another. E. nitens grew faster than E. pauciflora at 7 and 13C, but E. pauciflora grew faster than E. nitens at 3C. E. pauciflora always produced greater total and white root length than E. nitens. E. nitens roots browned faster in response to lowering soil temperatures than E. pauciflora. The osmotic potential of the roots decreased with soil temperature, but more so in E. pauciflora than E. nitens. Proline was a prominent osmoregulant in roots of E. pauciflora and arginine in E. nitens roots. It is suggested that E. pauciflora is better adapted than E. nitens to root growth at low soil temperatures because it can keep roots white longer and can maintain lower root osmotic potentials. Root growth of E. pauciflora was examined for 31 months (December 1992 - June 1995) in a mature stand at an elevation of 1545 m on Mt Stirling, Victoria, Australia. Greater night than day root elongation was recorded from eight in situ rhizotrons during the summer and early autumn of 1993. Shoot growth was also monitored during part of this study (April 1994 - June 1995). It was found that root growth commenced in the spring at soil temperatures 5 1.5C, under 550 mm of snow, at least one month before the onset of shoot growth and continued at least two months longer that shoot growth during the autumn. A period of root dormancy for at least one month a year occurred in roots of E. pauciflora. The seasonal variability in root numbers of E. pauciflora appeared to be related mainly to soil temperature and to a lesser extent to soil water content. Moreover, there appeared to be some internal periodicity in root growth which was independent of the external environment on Mt Stirling. Greater night than day root elongation was recorded in seedlings of both eucalypts in a glasshouse. Root elongation rates were greatest in E. nitens, and root elongation of both eucalypt seedlings were greater than that of the mature E. pauciflora on Mt Stirling. The zones of day and night elongation were determined in root marking experiments. Histological studies of the zone of elongation showed that cell division occurred mainly during the day and cell elongation mainly at night. Night root elongation rates were increased by increasing day-time air temperatures, light-period, and light intensity; and by decreasing water stress during the night. The turgor pressure of the root tips was greater during the night than the day. It is suggested that the amount of root growth during the night is determined directly by turgor pressure during the night and indirectly by processes during the day (light duration and intensity, and temperature during the light period) which determine the extent of cell division during the day. A greater rate of cell division during the day will be translated into a greater rate of root elongation, especially in the night.
  • Item
  • Item
  • Item
    Thumbnail Image
    Analysis of growth and yield in uneven-aged, mixed species eucalypts at Mt. Cole State Forest
    Phartnakorn, Jaruchat ( 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.
  • Item
    Thumbnail Image
    An analysis of radiata pine-pasture agroforestry systems
    Kellas, J. D ( 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.
  • Item
    Thumbnail Image
    The effect of fertilizer application on the growth of Eucalyptus globulus
    Kimanzu, Norman N ( 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.
  • Item
    Thumbnail Image
    Effect of later age fertilization with superphosphate at age 24 on tree growth, mechanical properties and wood quality of Pinus radiata D. Don
    Subyakto ( 1993)
    Later-age fertilization with superphosphate of Pinus radiata is one of the silvicultural practices used in Australia and is employed operationally on phosphorus deficient sites found in Victoria. Later-age fertilization of radiata pine has previously been shown to give satisfactory responses in terms of growth, wood production and economic values. However, sudden increases in growth rate can lead to detrimental effects on wood properties. The present study was aimed at examining the effect of later-age fertilization with superphosphate at age 24 on the tree growth, mechanical properties and wood quality of radiata pine grown on a phosphorus deficient site. Three trees from each of three diameter classes were selected randomly from a control plot and an adjacent fertilized plot at Scarsdale, Victoria. The fertilized plot had received 504 kg ha-1 superphosphate at age 24 and all eighteen trees studied were felled at age 38. Ring width, percent latewood and tracheid length were examined using a wood disc removed at breast height. Ring width and latewood were measured for each growth ring from pith to bark along the north and south axes. Tracheid length was measured for selected growth rings along the north axis. Basic specific gravity from pith to bark for the north and south axes was determined using the maximum moisture content method at five heights including 0.3 m, 1.3 m, 3.3 m, 7.3 m and 13.3 m. Mechanical properties which included static bending and compression parallel to the grain were determined for four axes for clear specimens removed from a 1.0 m log taken near breast height. Diameter and height growth of the fertilized trees increased significantly over the fifteen year period following fertilization by 30% and 34% respectively as compared to the controls. Volume of the fertilized trees increased 212% over the same period as compared to 77% for the controls. No significant differences in the strength properties were found for the wood produced after the age of fertilization between the control and fertilized trees. Non significant reductions of 8%, 6% and 4% were found for bending properties modulus of rupture, modulus of elacticity and stress at limit proportionality respectively. Non significant reductions of 6%, 11% and 12% were found for compression properties of maximum crushing strength, modulus of elasticity and stress at limit of proportionality. Mechanical properties of both the control and fertilized trees were generally greater than previously reported values for radiata pine. Ring widths increased substantially within two to three years following fertilization with mean values of the fertilized trees around two times that of the control trees. The enhanced radial growth was maintained through to harvest at age 38 and when combined with the the second thinning at age 35 increased even further relative to the controls. The effect of fertilization on percent lateveood was not consistent but appears to be somewhat dependent on the availability of moisture. The effect of fertilization on tracheid length was not clear as there appeared to be a site effect which resulted in the tracheid lengths of the fertilized trees being greater than the controls prior to fertilization. Basic specific gravity was reduced about 4% to 9 % following fertilization and the effect appeared to last for about six to nine years. It appears that the first thinning which occurred at age 20 prior to the fertilization contributed to this reduction in basic specific gravity. Over approximately the final six years of growth the basic specific gravity of the fertilized trees was 3% to 6% greater than the control trees. In conclusion, the effect of later-age fertilization with superphosphate at age 24 on the mechanical properties and overall wood quality appears to be minimal. The large gains made in tree volume following fertrilization on the phosphorus deficient site at Scarsdale and the fact that the later-age fertilization brings a relatively unproductive site into a productive capacity would appear to far outweigh any minimal reductions in wood properties. It further appears that on the deficient site the phosphorus remains available for tree growth through to rotation age and the additional wood produced at the later-age tends to have the desirable mature wood properties as compared to the less desirable wood properties which normally accompany the juvenile growth period.
  • Item
    Thumbnail Image
    The relative value of tagasaste and lucerne as supplementary feeds for sheep
    Belay, Aregawi ( 1993)
    Chamaecytisus palmensis (Tagasaste) is a leguminous perennial shrub which grows well in a range of climatic zones. Tagasaste was introduced from the Canary Islands to Australia in 1879 and a number of farmers are growing the shrub for fodder production and soil conservation. The most economical means of utilizing tagasaste in Australia appears to be direct grazing by sheep. This thesis reports on a study of tagasaste and lucerne as a supplementary summer feed for sheep in the Strathfieldsaye Research Station, East Gippsland, Victoria. The purpose of the present study was to investigate the relative value of feeding tagasaste and lucerne (Medicago sativa) as a supplementary feed for sheep during summer. Growth performance of sheep, dry matter consumed and the chemical composition of feeds were examined over the four months of the experimental period. The 240 two year old Merino sheep were divided into 12 groups for grazing eight plots of tagasaste and four plots of lucerne as a supplement to summer pasture. Each plot had been fenced into four or six subplots for tagasaste or lucerne respectively, to allow stock to be rotated in four months. The estimation of the dry matter consumed in each subplot was done by selecting 50 sample quadrats before and after grazing for each experimental month. The mean liveweight gain for all sheep in the lucerne plots (11.3 kg/head) was not significantly different from tagasaste (10.6 kg/head) at the end of the experiment. The mean total change in standing dry matter due to grazing in the tagasaste treatment (5360 kg/ha) over the four months was greater than for the lucerne treatment (3384 kg/ha). The overall daily growth efficiency over the daily dry matter (LW (g)/DM (g)) eaten by sheep in tagasaste was 0.20% and 0.34% for lucerne over the experimental period. In both treatments the pattern of pasture dry matter consumption did not resemble the pattern of liveweight gain. The digestibility and total nitrogen content of feed types were not significantly different between trial months. However, the leaf part of tagasaste had significantly greater values than other feed types during the trial although lucerne leaf was not measured. During the trial there was no loss of liveweight in sheep fed tagasaste or lucerne as a supplement. A second experiment indicated that tagasaste regrowth after grazing was significantly better in lightly grazed plots than in heavily grazed plots suggesting that farmers remove stock before all leaf has been eaten. In conclusion, the results of this study suggest that there is scope for the summer grazing tagasaste as a supplement to dry pasture however lucerne remains a better feed than tagasaste on this site. The high quality of tagasaste foliage (leaf) and low rate of liveweight gain of the experimental sheep suggest that further study is necessary to identify the cause of low stock performance.