School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemNitrogen fixation by Casuarina oligodon agroforestry in the Papua New Guinea central highlands( 2006)Casuarina oligodon L. Johnson is a multipurpose tree species grown in the highlands of Papua New Guinea (PNG). The integration of C. oligodon into agricultural systems is seen by villagers as means of restoring soil fertility, controlling soil erosion, providing shade for crops and producing fuel wood and building materials. Biological nitrogen fixation by C. oligodon through symbiotic relationships with Frankia (micro-organism) under field conditions in short (5-10 years) and long (11-15 years+) fallows in the PNG central highlands was investigated using the 15N natural abundance technique. Results from the study showed that as much as 70% of N in C. oligodon was derived from the atmosphere. The rate of N2 fixation was relatively low in short fallows of casuarina and increased as the trees aged in the long fallows. A rate of N2 fixation up to a maximum of 36 kg N ha -1 year -1 was estimated based on commonly practiced tree stocking rates and field conditions in the PNG highland areas. Although casuarina fallows tend to accumulate higher total N and C compared with equivalent period of grass fallows, the amounts of N and C in the surface soils of all systems under the study showed no significant difference. The amounts of total N and C under long fallows of casuarina (11-15 years+) were generally greater than short fallows of casuarina (5- 10 years). A significant proportion of the total N was stored in the above ground biomass of trees that were more than 10 years of age. Management of the standing biomass, particularly when the fallow is converted back to the cropping phase, is therefore critical in ensuring that the farmers are able to gain maximum benefit from the fixed N. Whilst the removal of stem wood for use as fuel or building material may be an important product of the agroforestry system, retaining the foliage, small branches and bark on the site is vital in sustaining agricultural productivity.
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ItemCardamom cultivation, livelihoods and biodiversity in a H'mong farming system in Northwest Vietnam( 2005)The recovery of the cardamom market in northwest Vietnam since the mid-1980s has seen many new groups of small farmers engage in the cultivation of this crop. A particular type of cardamom (Amomum tsao-ko) has a long history of cultivation by H'mong people in the Hoang Lien Mountains of northwest Vietnam. This thesis examined the implications of cardamom cultivation for H'mong livelihoods and forest biodiversity in those mountain farming systems, and explored options for improving farmer livelihoods through cultivation of this crop. Cardamom is in demand for both its aromatic and medicinal properties. It is providing a key source of income for H'mong ethnic farmers living at higher altitudes, people typically isolated from many other markets. The perennial crop requires partial shade and cool temperatures and for these reasons farmers utilize montane forest for its cultivation. These forests are also important for their biological diversity. Some cardamom cultivation practices (including tree felling to allow light to the crop) have been identified as having potentially negative effects on biodiversity. In this study a (partial) Farming Systems Research approach was adopted, which involved describing the farming systems at three (case study) villages, and identifying implications of cardamom cultivation for livelihoods and biodiversity at each site. Farmers were making transition from upland crops (rice and maize) to wet rice cultivation through the use of terraces to meet subsistence requirements, and had adopted cardamom as a cash crop despite the major labour inputs required in establishment. Extensive areas of forest and/or grassland on steep slopes dominated village sites. Cardamom was found to provide a key source of cash income for almost all farmers in the study area and had raised household income levels above the government-defined poverty level. Growers were committing significant labour resources over the initial five years of cardamom establishment, prior to receiving income. This labour on cardamom production competed with, but did not entirely replace, labour input towards improving subsistence income, i.e. establishing terraced fields for rice. Market uncertainty for cardamom presented some risk to small-scale farmers' livelihoods. If the cardamom market were to become flooded or depressed, the outcome would be a major setback for a large proportion of households, given the modest income from other cash crops and low total current incomes. Future inquiry aimed at better market understanding and ensuring stable income levels is recommended. Cardamom fields contained a higher number of plant species representative of montane forest, and in general much more favourable habitat for forest dwelling fauna than existed in alternative agricultural land-use types such as rice fields, upland fields or grassland. Tree cover was reduced by 25-50 per cent as a result of cardamom field establishment in forest, but there was no selective tree species removal. The lack of knowledge of the effect of forest thinning for cardamom cultivation on fauna habitat and animal movement means the abundance of some fauna species may be decling without our knowledge. However, farmers' involvement in cardamom growing ensured that forest would not be removed for other (less biologically diverse) types of land use. Farmers from certain villages have asserted de facto local use rights over particular areas of montane forest through their establishment of cardamom fields. As a result, some farmers had gained access to montane forest for cardamom cultivation - where they had no access to land previously. Research on cardamom production should focus on providing opportunities for farmers without access to montane forest, to grow cardamom in agroforestry systems on suitable land types near their villages. Farmers could be involved in `adaptation' trials aimed at developing new agroforestry systems using shade from planted tree species - as has been achieved in India and other regions. Such agroforestry systems on existing agricultural land may also make a positive contribution to forest biodiversity by increasing total vegetation.
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ItemSpontaneous agroforestry : regreening barren hills in Vietnam( 2003)This research concerns deforestation and the persistence of shifting cultivation in the uplands of Vietnam. Continuous cultivation of annual crops has resulted in large areas of hillside land becoming degraded grassland. Policies designed to support reforestation have been effective in stimulating spontaneous agroforestry development by farming households in certain parts of the country while in other areas deforestation continues. This research set out to explain the necessary conditions under which farmers in upland areas may spontaneously develop agroforestry systems in place of annual cultivation of agricultural crops and hence contribute to restoration of forest cover. The newly postulated 'keys to small-holder forestry' model formed the basis for the research. The case study method was selected because it was the most appropriate for testing the keys to smallholder forestry model and because insufficient resources were available for undertaking a questionnaire survey based method. The model was tested in a case study village in which farmers were spontaneously substituting shifting cultivation on hillsides with a form of agroforestry based on cultivation of bamboo. Data on the reasons why farmers chose to change their use of hillside land were collected using individual household semi-structured interviews, direct observation and focus group interviews. A visioning process was also used to assist in understanding the aspirations of the farmers. Methods used to analyse policy and the impact of particular programs on farmer decision-making included the use of secondary sources and interviews with government officials. This study is thought to be one of the first village level studies in Vietnam that seeks to explain farmer decision-making on agroforestry within the context of the entire household production system and incorporating the influences of policy, macroeconomic forces and village history. Understanding farmer decision-making is considered to be an important prerequisite to the development of strategies and programs that will support the development of environmentally sustainable and economically viable production systems on sloping land. Understanding farmer decision-making within a dynamic context necessitated the use of a systems approach, focused on livelihood security at the household level. The major conclusion to emerge was that the 'keys to small-holder forestry' model successfully predicted the conditions under which farmers adopted agroforestry in the case study village. As predicted, farmers expanded their agroforestry plots when this provided greater economic benefit to the household than alternative enterprises. In the case study, agroforestry was an attractive alternative to agriculture because of the high returns to labour, low capital investment and the high social security value. Agroforestry species were also better adapted to the degraded soil conditions than agricultural crops. Supporting factors, also predicted by the model, included favourable markets, a favourable institutional and policy environment, especially secure land tenure, knowledge of a suitable production technology and acceptable control over risk. Market forces were found to be a particularly strong incentive for spontaneous agroforestry development by smallholder farmers. This points to the possibility of using market based policy instruments that have been little utilised in the past for promoting agroforestry. The 'keys to smallholder forestry' model potentially provides significant new directions for policy making and for the design of agroforestry extension programs in Vietnam and South East Asia. In particular it provides a framework for integrating two of the major imperatives in upland development. The first is the need for environmentally sustainable production systems that are within the management capacity of farmers and the second is the need for economic benefit for individual smallholder households in order to alleviate poverty. The research demonstrates that, under the appropriate conditions, farmers' goals for sustainable production and government objectives to regreen barren hills may be compatible.
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ItemIssues for enhancing farmer participation in farm forestry research in Australia( 2002)For many years, the scientific and professional community have determined the priorities for agriculture research with little input from farmers. Farm forestry may be a new industry but it already faces the dilemma that other agricultural enterprises have experienced, where farmer research needs are not being met, adoption of new technologies is slow, and as a result further development is inhibited. For other agricultural industries these issues have lead to the adoption of collaborative or participatory approaches of securing farmer input into the priorities for research, from defining the research needs to carrying out the work and disseminating the information. Through a series of focus group discussions, farm foresters who have been involved in the Australian Master TreeGrowers Program and members of the farm forestry research community were asked to provide their attitudes and opinions towards farmer participation in farm forestry research. The objective was that these comments and perceptions might provide insight into the potential and constraints facing farmer participation and highlight opportunities for establishing a more participatory approach to farm forestry research. A qualitative methodology and analysis of results highlighted many issues that impact on farmer and scientists attitudes towards participatory research. It also highlighted that farmers and scientists see a role for farmer participation in defining research needs, but that involvement in other stages of the research would depend on a number of factors. In terms of encouraging a participatory approach to farm forestry research, the scientists believe in the use of `leader' farmers, whereas the farmers supported the use of grower groups and coordinators to facilitate the process. The outcomes also highlighted the need to develop methods for getting farm forestry information to farmers, that research organisations need to become unified in their approach to farm forestry research, and that the scientific community needs a culture change to accept participatory research as a legitimate means of investigation.
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ItemTree growth modelling of Eucalyptus delegatensis (R. T. Bak.) and other eucalyptus species utilising early-aged stand measurements( 1999)Growth modelling methods for Eucalyptus species that can make use of minimal measurement information are scarce but necessary for those involved in small-scale forestry to make informed decisions about investment and management options. A computer program, FARMTREE, is available for evaluating the costs and benefits of trees on farms, however its growth modelling functions could be improved. This thesis achieves this for Eucalyptus delegatensis (R. T. Bak.) and provides a series of stand basal area, survival, diameter distribution and individual tree diameter increment models that could be incorporated into a FARMTREE-like program. While not a major farm forestry species, the models have been related to other Eucalyptus species and when more later-age data become available, the methods used here could be fully applied to more suitable species. A systematic series of growth predictions were made, with estimates from the earlier processes being used in the next. Initially, the Gompertz function was selected as the best of five non-linear equations and used to model stand basal area based on two, early-age measurements, while keeping the asymptotic parameter constant. Survival was modelled using a modified logistic function with basal area and age as the predictor variables. The results from the above procedures were then used to model diameter distributions using a percentile-based parameter recovery procedure. The predicted distributions were assessed by comparing them to the actual cumulative density functions. Comparing the predicted estimates of basal area, mortality and diameter distributions to those produced by FARMTREE showed that the new estimates were better, both for the stands for which the models were developed, and for an independent data set. Individual tree diameter increment models based on distance-independent competition indices were also studied. Overall, the predictions for two-year diameter increment were not as good as for the previously studied areas of growth. This was especially noticeable when observing the results for the verification data set. These poorer results for diameter increment may be because of the less flexible methods used or perhaps partially due to the accumulation of previous prediction errors. The research approaches and functions used are easy to apply, efficient, accurate and require minimal actual growth measurement information. They could be applied to other species in greater detail when more information becomes available and could be incorporated into FARMTREE or a similar package for use by owners and managers of small farm forests with the expectation of providing improved growth predictions.
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ItemNutritional physiology of eucalyptus grandis and pinus radiata irrigated with municipal effluent( 1998)The aim of this study is to compare the processes of accumulation and use of N, P, K, Mg and Ca between two and four years of age in plantations of Eucalyptus grandis and Pinus radiata irrigated at several rates with municipal effluent, and with bore water. A series of five harvests over two years was used to estimate above-ground biomass and nutrient content. Growth rate was greater in E. grandis than in P. radiata. Total biomass at 34 months ranged from 34 to 45 t ha-1 in E. grandis and from 21 to 26 t ha-1 in P. radiata, with a trend towards higher rates of growth with increased irrigation rate. Foliage mass and leaf area index (LM) were initially greater in E. grandis than P. radiata. However, the rate of increment in foliage mass and LAI in E. grandis decreased after canopy closure (at about 20 months). At 34 months foliage mass averaged 5.9 t ha-1 in E. grandis and 7.4 t ha-1 in P. radiata. Nutrient accumulation was primarily a function of growth rate, in particular the rate of canopy development. Rate of nutrient accumulation in E. grandis was greatest prior to canopy closure, decreasing thereafter, and in P. radiata it was greatest in the last year. As a result, mean annual increment of nutrient accumulation was maximum in E. grandis at 28 months, and in P. radiata at the end of the study. Implications for management of effluent-irrigated plantations are discussed. The mass of each nutrient accumulated varied greatly and decreased in the order Ca
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ItemAgroforestry strategies for catchments in the humid tropics( 1995)Catchments in the humid tropics play an important role in the ecosystems and the economies of countries they are in. They are slowly deteriorating because of inappropriate land-use systems being practised by people in them. Agroforestry is seen as a potential land-use system which could help rehabilitate degraded catchments and prevent others from deteriorating. However, selection of appropriate agroforestry strategies to be used for a particular catchment is a problem. The aim of this study was to develop a method that would be able to determine the best combination of agroforestry strategies for a catchment in the humid tropics, that is the one that would yield the maximum net social benefit subject to the constraints of maintaining agricultural yield and net income, keeping erosion within acceptable limits, enhancing soil nutrition, and providing a source of firewood for the catchment users. To achieve this aim, Mt. Masaraga catchment in the Philippines was selected as a case study from which some implications could be drawn that would relate to other similar catchments. Potential agroforestry strategies were presented to the upland farmers in the catchment for acceptability. The selected agroforestry strategies were then evaluated for their capability to prevent soil erosion, to supply firewood, and to provide organic fertiliser for three slope classes. A fuel study was also conducted to determine the fuel consumption of the catchment users. Financial and economic analyses of each selected agroforestry strategy for the three slope classes were then conducted. Linear programming models for the catchment were constructed using average value of the rainfall erosivity index value for the computation of soil erosion. A chance-constrained model which takes into account the probability of rainfall erosivity index value exceeding the average was also constructed. Four agroforestry strategies were found to be acceptable to the upland farmers: contour hedgerow; hedgerow with contour canal; live fences; and combination of contour hedgerow and hedgerow with contour canal. Two models were formulated, a model which assumed that the whole catchment would be converted to agroforestry immediately, and one that incorporated the time of adoption of the agroforestry technologies as a further constraint. It was established that in the Mt. Masaraga catchment, it would be profitable to farmers to adopt agroforestry strategies, but the benefit to society was far greater than to the farmers. The cumulative NPV of the incremental net benefits for the optimum combination of agroforestry strategies for the Mt. Masaraga was P72.4 million greater than if the catchment remained under conventional farming. The chance-constrained model indicated that savings would be even higher if the rainfall erosivity index value in individual years exceeded the average rainfall erosivity index value used in the deterministic model. It was established that the land with steepest slopes should be converted to agroforestry first, because of its ability to reduce the high level of erosion expected on these slopes with conventional farming. More rapid adoption of the strategies resulted in greater savings, indicating that it would be worth spending money on education programs to speed up the rate of adoption. Although these results were specific to the Mt. Masaraga catchment, there is nothing to prevent construction of similar models for similar catchments in the humid tropics, and similar results could be expected.
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ItemPotential impact of a farm forestry industry on the Goulburn regional economy( 1996)Transactions for a hypothetical farm forestry industry in the Goulburn region were constructed from the output of the FARMTREE model. Eleven different regimes were simulated, including hardwood and softwood, woodlots, timberbelts and wide-spaced agroforestry. This output included estimates of annual cash flows of costs and revenues per hectare. These were transformed to regional aggregated cash flows projected forward over one hundred years. A regional input-output table without farm forestry was constructed using the national input-output table and GRIT and adjusted for future growth. For certain years or 'snapshots' the farm forestry industry transactions were inserted into the future projected input-output table for the Goulburn regional economy. The new balanced input-output table summarizes the inter-sectoral flows and describes the regional structure with the new farm forestry industry inserted. Three snapshots were taken representing different stages of the development of the farm forestry industry: i 2004, the establishment phase: when the cost of plantation formation is greater than the predicted returns from wood sales. ii 2019, the transition phase: when the returns from wood sales have begun to swell whilst new sites are still being planted. iii the steady state phase: when harvesting is equal to replanting, no new sites are being planted, a full range of plantations exist at different stages of formulation and returns from wood sales have trebled since the previous transition year. Two methods were used to analyse the input-output tables constructed and the associated impacts. The first method was the analysis of the difference between the input-output table with farm forestry inserted compared to the input-output table without farm forestry inserted. This method allowed the estimation of the effects of farm forestry industry and the value-added processing of farm forestry products on the other sectors in the regional economy and hence the economy as a whole. The second was with conventional multiplier analysis used to estimate the changes in a given year resulting from an increase in demand for the farm forestry industry, wood manufacturing and other sectors. In the year 2034, the introduction and integration of a farm forestry industry in the Goulburn regional economy potentially generates, using multiplier analysis: $53 million worth of output; $13 million worth of income; and provides for up to 234 jobs. The farm forestry industry, using the difference method of analysis, produced a change in the economy of: $1,268 million in total output, a change of 6 per cent; $302 million in total income, a change of 5 per cent; and 5,750 jobs, a change of 4 per cent. The industry that experiences the single largest increase was the wood manufacturing industry through its value adding of the product purchased from the farm forestry industry.