School of Agriculture, Food and Ecosystem Sciences - Theses
Permanent URI for this collection
Search Results
1 - 10 of 10
-
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.
-
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.
-
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.
-
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.
-
Item
-
Item
-
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.
-
Item
-
Item
-
ItemAgroforestry : a study of agroforestry extension and a model of light interception in agroforestrry( 1986)This thesis examines two important aspects of agroforestry in Australia: agroforestry as an agricultural innovation and light interception by the tree crop. (1) Agroforestry as an innovation The ideas and opinions of farmers and professionals involved in agroforestry in Australia were studied by mail-return questionnaires. Questionnaires were sent to all farmers and professionals known to be actively involved in agroforestry. - The study is not a statistical survey of a population. The potential of agroforestry as an agricultural innovation is discussed with reference to the response to the survey and the literature. The need for a universally accepted classification of agroforestry practices is demonstrated and a system suitable for agroforestry in Australia and New Zealand developed. The classification is an adaption of agroforestry classifications developed for use in less industrially developed countries. The adopters of agroforestry involved in the study are shown to be more educated, of-higher social status, and more innovative than farmers in general. Most show opinion leader status within their local community and have a positive attitude towards agroforestry, as do the professionals involved in the research and extension of agroforestry. It is argued that agroforestry adoption is following the general trend of innovation adoption and can be expected to be adopted at an increasing rate in the near future. Factors that may limit the extent or rate of adoption are identified and a strategy developed to ensure good two-way communication between researchers and potential adopters so as to encourage successful adoption of agroforestry by interested farmers. (2) Light interception Light is shown to be a major limiting factor affecting agricultural production in agroforestry. Light interception by the tree crop reduces light availability at ground level and therefore growth of agricultural crops. Past models of light interception by discontinuous tree canopies are reviewed and a new computer based model developed. The model, TREE-SHADE, allows estimates to be made of the light interception by a stand of widely spaced trees at any time on any date. Input variables include the nature of the site, the mean size and shape of the tree crop, the spatial arrangement of the trees and the times and dates of interest. The model is tested against field results collected in a seven year old agroforest of Pinus radiata near Canberra. The model was shown to slightly underestimate solar radiation availability at ground level beneath the trees. The difference was partly explained by variability in spacing and was not considered significant enough to detract from the value of the model.