School of Ecosystem and Forest Sciences - Theses
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ItemA study of the land in the Victorian catchment of Lake Hume( 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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ItemRegeneration of river red gum Eucalyptus camuldulensis Dehn( 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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ItemThe mechanical properties and characteristics of the timber of spotted gum (Eucalyptus maculata Hook.) in relation to origin and maturity( 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.
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ItemSalting in Victorian catchments: an investigation of soil salinity problems arising under non-irrigated condititons in Victoria( 1956)Salting, that is, the accumulation of excessive amounts of soluble salts in soils, is found in many parts of the world. In Victoria salting is associated with the presence of a permanently saline water table in irrigation districts, or with local accumulations of salt in catchment areas. The results of an investigation, carried out between April 1952, and December 1955, into this second problem, referred to here as catchment salting", are set out in this thesis. The introductory part of the thesis includes evidence regarding the incidence, and economic importance, of catchment salting in the state. The area affected is estimated as nearer 10,000 than 100,000 acres; it is mainly the better class land of valleys, and flats. Salting is extending, but at present its main importance lies in the severe erosion which it induces. In the second part of the thesis, the ecosystems, under which the accumulation of salt in the soils or a catchment can take place, are examined. The factors contributing to such an ecosystem are listed here, with summaries of the conclusions reached: i) Accessions of salt to the soil. In Victoria these salts are largely chlorides of oceanic origin, their presence in soils inland can best be accounted for by the cyclic salt theory. The evidence for this theory is reviewed, and reasons are put forward to account for variations in cyclic salt accessions at different sites. ii) A low precipitation/evaporation ratio. Such a ratio prevails in many parts of Victoria. iii) Vegetative cover with a high water usage. The catchments, in which salting now occurs, were formerly covered with Eucalypt forest, or woodland, making use of rainfall. iv) Soils having an impermeable horizon. at no great depth. Salting in Victoria is confined to catchments with soils of the solodic or solonetzic, type, characterised by a light textured A horizon overlying a heavy clay B horizon. In an undisturbed catchment of this type the hydrological equation can be expressed by: Precipitation = Evaporation + Transpiration. So that, with annual accessions of salt, some accumulation in soils of the catchment is to be expected. In these catchments, which are found chiefly in the 20” – 30” rainfall areas, drastic changes in the hydrological balance have followed settlement. All too frequently catchments have been overcleared, and overgrazed, and the resulting reduction in transpiration has produced a surplus of groundwater, with accelerated water movement downslope. The sub-surface flow over the clay horizon of solodic type soils carries down any soluble salts from the catchment; should this flow be impeded, and saline water brought to the surface, salt is concentrated by evaporation, and salting occurs. A knowledge of the factors responsible for salting will enable an assessment of salting liability in catchments to be made. Three types or salting, seepage, wetpan, and hardpan, found in Victoria, are described, with the types of vegetation which occur on each. The soils of seepage, and wetpan, areas are described as “saline”, and those of hardpan areas as "salinealkali", following the classification used by the U.S. Salinity Laboratories, Riverside, The compacted surface structure of hardpan soils, despite the high soluble salt content, is attributed to the compacting action of raindrops whilst the surface soil is temporarily washed : free of salt, and is in the “alkali” condition. Hardpan formation accounts for the characteristic shallow, and extensively dissected, pattern of erosion on salted land. In the third part of the thesis, the control of salting, and the reclamation of salted land, are dealt with. Correct catchment management, which ensures sufficient vegetative cover, is the surest control measure. Measures such as drainage, the establishment of trees and shrubs, and of improved pastures, are dealt with in a general way. Detailed results are given of trials with fertilizer, and soil improver, treatments; also of trials with some sixty species, and varieties, of grasses, and legumes, on salted land. In the final chapter the evidence, and conclusions, of previous chapters are reviewed, together with recommendations for the treatment of salted land; it therefore provides a more detailed summary, should that be required. Details of soil sampling, analytical methods, plot layout, statistical methods, and some lists, and photographs, of plants, are given in seven appendices.