School of Ecosystem and Forest Sciences - Theses

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    A study of the land in the Victorian catchment of Lake Hume
    Rowe, R. K ( 1967)
    This report is the result of a broad-scale survey of the environment and land-use of the 3,900-square-mile Victorian catchment to Lake Hume. Because of the mountainous nature of much of the catchment, the climate varies considerably. Average annual precipitation ranges from about 30 inches with rare winter snow in the northern parts where elevations are low, to over 60 inches in the south-western highlands where snow forms the major part of winter precipitation. A strong rain shadow reduces annual rainfall to about 26 inches in the Omeo-Benambra area. The Cudgewa-Corryong area is in a less severe rain shadow with annual rainfall just below 30 inches. It seems probable that the Limestone Creek valley and several other valleys with north-easterly alignments may also be in rain shadows but there are no records to confirm this. Average temperatures for January and February, the hottest months, range from about 72 F. in the north-west down to about 51 F. on the highest peaks. In July, the coldest month, average temperatures range from around 46 F. down to about 29 F. The rocks are mostly poor in ferro-magnesian minerals; igneous, metamorphic and sedimentary rocks are more or less equally represented. The texture of the parent material is an important factor in soil formation in the lower-rainfall areas. Small areas of basalt occur at high elevations in the south-west and near Benambra. Mountains ranging from about 1,200 feet to over 6,500 feet make up most of the catchment. Plateaux varying from a few acres to more than 50 square miles occur over a similar range of elevations. Broad, mature valleys with extensive terraces and fans are a feature of the northern part of the catchment. Except for small areas of soil on calcium-rich alluvium near Benambra, the soils are all acid, and most are phosphorus deficient, but fairly well supplied with potassium. The soils of the high-rainfall areas are well leached. Most of the plant nutrients they contain are concentrated in the surface few inches. However, there has been little or no eluviation of clay or iron. In the soils of the lower-rainfall areas there has been eluviation of clay and iron, and the distribution of plant nutrients usually follows a similar trend, except for some concentration at the surface because of biological recycling. The most important agricultural soils are the red podzolics of the terraces and the alluvial brown earths of the stream flats in the northern valleys. The distribution of the vegetation is strongly influenced by temperature and by soil-moisture availability, which in turn is affected by other factors. As rainfall increases, on well-drained sites, the dominant vegetation ranges from dry sclerophyll forest to wet sclerophyll forest. Above about 4,500 feet elevation, low temperatures are important, and the sub-alpine woodland which occurs above the forest-form vegetation becomes stunted, and finally gives way to alpine shrubs, grassland and herbfield. Sphagnum-moss bogs are an important hygrophilous community in the alpine tract. The vast changes brought about by settlement have not always been beneficial. Clearing of forests without the establishment of vigorous pastures has led to excessive run-off, erosion and flash floods. The higher-rainfall and snow-fall areas are of vital importance because of the high and sustained yield of water from these areas. Lower-rainfall areas probably contribute little useful water to the irrigation storages. Forestry is an important form of land-use. The most productive forests are in high-rainfall areas, so care in forest operations is necessary to prevent deterioration in the hydrologic condition of these areas. The northern valleys are the most intensively farmed areas in the catchment. Dairying is a major industry, and the grazing of sheep for wool and meat, and beef-cattle fattening are also important. Although the terrace country generally carries improved pasture, pasture improvement and grazing management on hill country are problems. In the Omeo-Benambra country where the grazing of sheep for wool, and beef-cattle production are the major primary industries, there is scope for considerable improvement in pastures and in grazing management. The Omeo-Benambra country is the most severely gully-eroded area in the catchment and probably contributes more sediment to Lake Hume than any other area. Sheet erosion in the alpine areas is a serious problem because of the effect on infiltration and run-off, and the difficulty of obtaining revegetation. Erosion of the banks of major streams also contributes to sedimentation of the reservoir and destroys valuable river flats. The widespread use of fire to improve grazing in the higher-rainfall forests in the past has apparently led to development of dense undergrowth. This has reduced the value of this country for grazing and has created a considerable fire hazard. Fire protection is vital to all forms of land-use. For convenience in describing the distribution of the environmental factors, the catchment has been divided into land systems which are units based on recurring patterns of land forms. The environment, land-use, erosion and problems specific to each land system are described. Diagrams are used to illustrate the pattern of land forms and to tabulate the environment and land-use of each land system. From considerations of the interacting effects of all of the factors of the environment, assessments of land-use potential have been made which provide a basis for sound land management.
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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.