School of Botany - Theses

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Start date: 1964 × End date: 1969 ×

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    The ecology of mixed-species forests of Eucalyptus in central Victoria, Australia
    Gill, A. M. (Arthur Malcolm) (University of Melbourne, 1966)
    Mixed-species forests of Eucalyptus are common in Australia and within one area, the two or three species which may form these forests often appear to be equally successful. Two forests, one of E. obliqua and E. cypellocarpa and the other of E. obliqua and E. radiata, were studied in the Great Dividing Range of Central Victoria in order to discover the reasons for the successful cohabitation of the species. The barriers to successful interbreeding which occur between the species were investigated. E. obliqua and E. radiata belong to the same interbreeding group, but few or no hybrids are successful. Flowering times were found to be separated, but only by a short interval. It is suggested that weak interspecific hybrids may be formed, but are eliminated as the forest grows, E. cypellocarpa belongs to a different breeding group to the other species and is incompatible with them. Distributions of the species have been studied in order to discover the nature of interspecific differences. Australia-wide distributions show wide variation, but environmental data are too scarce to permit analysis of any interspecific differences in habitat. In Central Victoria E. cypellocarpa occurs in higher site quality areas than E. radiata, but the critical components of site difference were not established from field data. Experimental work in the glasshouse, using different levels of nutrition and soil water status, produced differences in total plant yield per pot, but showed interspecific differences too slight to assist in explaining the separation of species in the field. Frost may also be important, but no experiments were performed on relative species' frost resistance. Within each forest the relative frequency of tree species changes with tree height. E. cypellocarpa and E. radiata are more tolerant than E. obliqua. Tolerance to shade was tested by placing seedlings beneath shade screens, but the species were found to have similar responses. However, other factors, such as insect and fungal attack, grazing and drought, in combination with shade, may lead to the observed interspecific differences. Regeneration studies suggested that suppression may occur in both saplings and seedlings. Fires are an irregular but important environmental component, and studies of the fire resistance of the trees were initiated. Field studies of bark thickness and moisture content were combined with laboratory studies of fire effects. Seed production of the forests in the study area is cyclic, but E. obliqua and E. radiata have more reliable seed production than E. cypellocarpa. The seed on the tree is that used for forest reproduction: no soil storage of eucalypt seed occurs there. Cohabitation appears to be permitted by the presence of barriers to the success of interbreeding and through compensating interspecific differences.
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    Investigations into decay of standing timber in Victorian forests
    Binns, Audrey ( 1964)
    The Forests’ Commission of Victoria has jurisdiction over the remaining 22,000 sq. miles of native forests in our State. Although soil conditions, temperature, rainfall etc. differ throughout the State areas of 87,884 sq. miles, the dominant members of the various forest associations are all Eucalyptus species. The best development of any forest is attained in areas of high rainfall coupled with moderate temperatures, and consequently, the largest stands of Eucalypts are found in the area classified as ‘temperate, moderate rainfall forests’. Within these forests the most abundant species is Eucalyptus regnans F.v.M., or Mountain Ash which thrives from 600’ – 1500’ on the deep fertile, well drained volcanic soil. The importance of this species can be appreciated when its abundance is considered in association with its versatility. It is eminently suitable for furniture making, building, paper pulp, boxes, cases, etc. Saw milling is the fifth most important industry in Victoria and therefore, the fact that it is rare to log a mature specimen of E. regnans devoid of decay, is cause for concern. As a result of this economic loss, the Forests’ Commission embarked on a programme of laboratory work in an attempt to evaluate the importance and extent of the various types of decay in the field. Up to this date (1940) the laboratory testing of wood blocks in relation to decay had been almost wholly confined to work concerned with timber preservation. The techniques, therefore, had to be adapted for the experiments envisaged within the proposed programme. Parkin initiated the Forests’ Commission’s work. She attempted to produce decay of E. regnans block under controlled conditions using the Bell Telephone Method in vogue at that time. Into each straight sided test jar was placed a small glass jar containing water. Each of two wooden wicks had one end in this water and the other penetrating a hole bored through a supporting slab and then into the test block. The inocula were placed on the blocks after sterilization of the system. She experienced difficulties in maintaining the moisture content of the blocks, in controlling contamination, in the lack of growth of inocula and in the decay of the wooden wicks. After twelve months only four (4) of the sixteen (16) test fungi used, gave significant losses of weight in the test blocks and no typical macroscopic rots were produced in this period. In 1939 another method of producing decay in the test blocks was published. Whilst studying termites, Leutritz found that pieces of wood infested with these organisms, decayed very readily when covered with rich garden soil. Subsequent tests confirmed his belief that soil provided a particularly suitable medium for the growth of wood rotting funghi with a resulting rapid rate of decay. His suggestion for an accelerated rate of decay was to bury test blocks in soil in the test jar and to sterilize the whole system prior to inoculation. As this method of bio-assay had not been standardized when this work was planned (1942), several variations of Leutritz’s method were tested over incubation periods of 6, 12 and 24 months. During the incubation of the test jars attempts were made to identify the test fungi, and although little success was achieved in positive identification, a useful method of distinguishing between brown and white rot fungi was devised. This thesis is concerned with wood decay and for convenience is presented in section, each of which represents a different aspect of the work.