School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemPhysiological aspects of root growth of Eucalyptus pauciflora, subsp. pauciflora and Eucalyptus nitens( 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.
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ItemAnalysis of growth and yield in uneven-aged, mixed species eucalypts at Mt. Cole State Forest( 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.
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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.
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ItemThe effect of fertilizer application on the growth of Eucalyptus globulus( 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.
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ItemEffect of later age fertilization with superphosphate at age 24 on tree growth, mechanical properties and wood quality of Pinus radiata D. Don( 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.
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ItemThe relative value of tagasaste and lucerne as supplementary feeds for sheep( 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.
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ItemRoot-shoot interactions in the growth of irrigated white clover( 1993)White clover pastures support the dairy industry in the irrigated area of northern Victoria. However, pasture production is low because conditions for root growth are sub-optimal, particularly under flood irrigation. This thesis investigated the possibility that the growth of white clover can be increased by reducing the limitations to root growth. A series of experiments examined the response of white clover plants to various soil-based treatments and quantified relationships between root and shoot growth. Plants were grown in intact soil cores in the greenhouse with shoot and root growth measured by destructive harvest. The cores were collected from a range of field sites that were characterised by their different soil physical properties and the variation in pasture yield they supported. Other cores contained a sand-based potting mix in which the conditions for root growth were superior to the most productive field soil. Despite the large effects of soil treatment on white clover production, the growth of shoots and roots was highly correlated (R2>0.95). A prerequisite of high shoot yield is, therefore, a large root system. In one experiment, soil drying or defoliation perturbed the correlation but this disruption was only temporary. In another,experiment, the repeated cycles of drought stress that accompanied a series of extended irrigation intervals had no effect on the relationships between shoot and root growth. In field soils, the restrictions to root growth could not be overcome by intensive irrigation and fertiliser management. However, plants in the treatments in which the soil physical properties had been modified produced 4.0 - 6.5 times as much shoot DM compared with the least productive treatment. This suggests that the potential to improve pasture yield by amelioration of the soil physical properties is very large. Two further experiments were conducted in which either the soil texture or the frequency of irrigation varied between the upper and lower sections of the soil cores. In both cases the production of shoots was correlated with total root production. However, when `unfavourable' conditions restricted the growth of roots in one layer, extra growth of roots in the `favourable' layer was not sufficient to compensate. As a consequence, both total root and shoot growth were reduced. Taken together, these results suggest that there is a large scope to improve the yield of white clover by removing the restrictions to root growth that currently exist in field soils. This will probably entail both amelioration of the soil physical properties and careful management with respect to water and fertiliser applications. However, if the experiments reported here accurately reflect the field situation, then the growth of white clover pastures can only be maximised if the entire root zone is modified.
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ItemEffects of mulching logging residue on soil water relations, soil temperature and early growth of Pinus radiata on sandy soils in south-west Victoria( 1990)The timber industry in Australia is becoming increasingly dependent on plantations of exotic softwoods, with Pinus radiata D. Don (Monterey pine) the most important species planted in Victoria and South Australia. In general, these plantations have been highly productive in the first rotation. However, in the second rotation there is evidence of a decline in productivity on relatively infertile sandy soils, particularly where the litter and logging residue remaining after clearfelling is burnt. Research has indicated that this decline can be arrested by careful control of cultural inputs, such as chemical weed control, fertiliser and planting of legumes, or by mulching the litter and logging residue. This thesis reports on a study that examined the interacting effects of mulch, weed control and fertiliser on soil and plant water relations, weed biomass, soil temperature, root development, tree growth, and biomass and nutrient accumulation during the first five years following re-establishment of a P. radiata plantation. Mulch, weed control and fertiliser were applied (present, absent) in a 2 x 2 x 2 split-plot factorial design, resulting in eight treatment combinations. Mulch was applied prior to planting; weed control prior to planting and at regular intervals thereafter to age two years; fertiliser at 1.5, 10 and 14 months after planting, a total of 58.1 kg ha-1 of nitrogen and 19.1 kg ha-1 of phosphorus (as part of a complete mineral mix, including zinc). During the first two years after planting, soil and plant moisture levels, soil temperature and tree growth were monitored at four-weekly intervals, and weed biomass three-monthly. Annual growth was also monitored to age five years. Root development, tree biomass and nutrient accumulation were examined in detail at age two years. In the absence of mulch and weed control, soil moisture was significantly reduced during the first two summers after planting due to evapotranspiration losses, with a consequent reduction in tree growth. Both mulch alone and weed control alone were similarly effective in conserving soil moisture in the surface 10 cm of soil, through a reduction in evaporation and transpiration losses respectively. There was evidence that transpiration losses from weeds in mulch had a greater impact than evaporation losses from bare soils at depths from 10 to 40 cm. Maximum soil moisture levels during the summer months occurred where the mulch and weed control treatments were applied together. Mulch reduced weed biomass on average by half for the first two years after planting compared to that on bare soils with no weed control, though weed biomass by mid- to late- summer was similar for both treatments. Weeds which establish in the mulch treatment benefit from improved soil moisture availability as do the P. radiata trees. Mulch significantly reduced soil temperatures compared to those under bare soils during the spring and summer months, particularly in the surface 10 cm of soil. This is likely to have led to less favourable conditions for root growth and mineralisation of soil nitrogen under mulch during spring, when soil moisture availability is not limited by any of the treatments. During summer however, conditions were more favourable under mulch due to higher soil moisture availability. Where mulch and weed control were both applied, root length at age two years was almost twice compared to that for weed control alone. This difference occurred in the surface 10 cm of soil, and is attributed to the combined effect of higher soil moisture availability and stable temperatures within the optimum range for root growth under mulch during the summer months. Roots were also found in the mulch, which indicates that P. radiata roots can either extract nutrients, water or both from the mulch itself. All growth parameters show that in the absence of fertiliser, the responses to mulch alone and weed control alone were similar up to age five years, and that growth was significantly increased when both treatments were applied. These responses were however confounded, as severe zinc deficiency was induced on the weed control alone treatment. In the presence of fertiliser, the responses to mulch alone, weed control alone and both treatments combined were similar by age four years. The largest response to fertiliser was for the weed control alone treatment, probably due to the correction of zinc deficiency. A fertiliser response was initially found where both the mulch and weed control treatments were applied, but by age four years this response was no longer detectable. Growth at age five years was a maximum on, and not significantly different between, the mulch and weed control, mulch and fertiliser, weed control and fertiliser, and mulch, weed control and fertiliser treatment combinations. The nitrogen concentration in needles less than one year-old was at or below the critical level of 14 g kg-1 for all treatment combinations at age two years, except for the weed control alone treatment which was affected by severe zinc deficiency. Despite this, foliage on the treatments associated with good growth did not show obvious nitrogen deficiency symptoms. It is likely that there was net immobilisation of nitrogen under the mulch treatment during the first two years, but subsequent to this it is considered that the mulch would have been a source of nitrogen to the P. radiata trees. Foliar concentrations of both phosphorus and potassium were adequate for all treatment combinations. Foliar concentrations of zinc were at or below the critical level of 10-11 mg kg-1 for those treatments showing maximum growth, which indicates that demands were just being met. They were well below the critical level for the weed control alone treatment. There is clear evidence that the mulched litter and logging residue is a source of zinc to the replanted P. radiata. Relationships between concentration of nutrients in biomass components and tree diameter were generally weak and not significant, and thus nutrient accumulation closely mirrored the pattern of biomass production. The results show that mulching of the litter and logging residue in situ has the beneficial effects of conserving soil moisture, which in combination with more favourable soil temperature conditions during summer, resulted in satisfactory early growth. The results also indicate that mulch is a source of nutrients to the re-established crop. Although care must be taken in extrapolating these results, forest managers should consider mulching as an alternative site preparation technique to burning, particularly on infertile sandy soils.