School of Ecosystem and Forest Sciences - Theses

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    Regeneration of river red gum Eucalyptus camuldulensis Dehn
    Dexter, Barrie Donald ( 1970)
    The aims of this study were to investigate the main factors influencing the regeneration of river red gum Eucalyptus camaldulensis Dehn., in Barmah forest and to use the results to develop procedures for establishing regeneration primarily for wood production. Factors influencing germination and survival of seedlings were examined. These included seed supply, seasonal conditions, seed beds, availability of soil moisture, the influence of over-topping trees, flooding and grazing. Natural seed supply is variable because the intensity of flowering varies widely and unpredictably from year to year and about 45 per cent of flowers fail to mature. Seasonal conditions are a major factor affecting germination of seed and survival of seedlings especially in the absence of flooding. On unflooded areas germination is confined to the wetter, cooler months and survival is highest if there are good summer rains. Germination and survival following flood recession are often high. When flood recession occurs late in summer, however, hot conditions may kill most seeds or young germinates. The combination of winter-spring flooding and above average summer rains favours germination and survival. In very dry years few seedlings develop and these are restricted to the most receptive sites. Ash bed and cultivated seed beds are the most receptive sites for seedling establishment and grassed and hard bare earth sites are the least receptive. Seedling establishment is also severely restricted where weeds or over-topping trees compete with seedlings for moisture. Prolonged flooding kills large numbers of young seedlings especially if they are completely immersed for some months. Flooding is uncontrollable so it is advantageous to promote rapid seedling growth and so minimize deaths or severe flood injury. During drought periods red gum seedlings may be destroyed by rabbits, kangaroos, wild horses and cattle. When feed is abundant, however, the adverse effect of all these animals is slight. Extensive grazing of cattle on regeneration areas keeps weeds that are competing with seedlings for moisture in check, and seedling mortality due to soil drought is much less than on ungrazed areas. Several techniques for regenerating river red gum were developed from the fundamental studies and were tested on an operational scale. Of the procedures based on direct seeding clear felling followed by aerial seeding is the cheapest and most flexible, and is recommended as the technique to be used generally. The major costs involved are in seed bed preparation, poisoning non-merchantable trees, collecting seed and in aerial seeding. None of these operations is expensive. Sowing rates and time of sowing are determined on the bases of expected flooding and seed bed quality. Seed beds are made receptive by removing grass and other vegetation and preparing the ground surface by slash burning and cultivation. Procedures based on natural seed supply involve preparation of seed beds and inducement of seed fall during summer and autumn, followed by utilization of merchantable and poisoning of non-merchantable trees. Because careful timing of each phase is required to suit such factors as seed maturation, seed fall and germination, the induction of seed fall can be costly and difficult to organize. Various factors that may influence the choice of the regenerative procedure are discussed. Finally, it is concluded that the provisional stocking standards are compatible with other forest values.
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    The mechanical properties and characteristics of the timber of spotted gum (Eucalyptus maculata Hook.) in relation to origin and maturity
    Bolza, Eleanor ( 1978)
    Natural forests are of primary interest to foresters and other scientists since these types of forests are the main source of genetic and plantation materials. Nevertheless only few studies on variability in natural forests seem to have been undertaken so far, owing to problems occurring in the measuring of numerous variables. For instance juvenile and mature stages of trees and their timbers often differ in such characteristics as growth habit and density and mechanical properties of wood. The external factors of environment including climatic factors, just as much as geographic variations and. genetic characteristics exert their influence on natural populations. There seems to be considerable disagreement as to how environmental factors such as position of the tree within a stand, silvicultural practices and site conditions influence various properties. It is not possible within the scope of this thesis to cover all these aspects. The study on which this paper is based has three primary objectives: 1. To give a description of the characteristics of the standing Eucalyptus maculata Hook. tree together with the properties and uses of its timber. 2. To study the extent of variation between the strength properties and density of the timber of mature and immature trees from the same area. 3. To investigate the effect of geographical origin (latitude) and provenance variation of the species.