Sustainability responds to crises of ecology and human development and the relationships between them. Sustainability cannot be adequately described using disciplinary categories arising from the modern dichotomy between nature and culture. Sustainability research requires a methodology that reflects the reality of its subject. This thesis presents material semiotics as a methodology for sustainability research. Material semiotics refers to the work of actor-network theorists and latter developments of alternate spatial metaphors for material relationality. Actor-network theory is a methodology that describes human and non-human actors in the same terms. It follows actor through networks of material relationships that they constitute and are constituted by, depicting heterogeneous objects without recourse to prior categories of nature or culture. The description of material relationships in fluid and regional, as well as network, spaces expands the descriptive power of material semiotics to include Others and to better represent complexity. The Oil Mallee Project is a case study of sustainability in the Western Australian wheatbelt. Indigenous eucalypts, oil mallees, are planted on land that was cleared for agriculture. The above ground biomass can be processed for eucalyptus oil, electricity and activated carbon, and the rights to carbon stored in the extensive mallee roots, or in unharvested trees, can be sold. The Project responds to a number of sustainability issues, including ozone depletion, land degradation, climate change and rural decline. This thesis follows the actors that comprise the Oil Mallee Project to describe its complexity, multiplicity and sustainability. Qualitative interviews with actors in the Project and the wheatbelt provided the primary data, which is supported by documentary material. Three contingent phases can be identified in the history of the Oil Mallee Project – eucalyptus oil industry, dryland salinity management, and greenhouse response. The Project has persisted because it is simultaneously a regional, network and fluid object. Mallees grow well in the tough conditions of the wheatbelt. Mallees can be integrated with existing networks of industrial agriculture. The Project has achieved contingent stability in policy documents and the networks of scientific research. The fluidity of the Project has enabled it to change shape and identity in response to threats and opportunities, and as relationships break and form, without complete disruption. Specific humans have been central heroes in different phases of the Project. The mallees themselves are the only actors that have been consistently central to the identity of the Project. Sustainability requires knowledge of the relationships between humans and non-humans that constitute the multiple crises of ecology and human development. Sustainability is the re-ordering of those relationships in ways that make possible ecological integrity and human fulfilment. Material semiotics is a methodology for knowing sustainability in ways that reveal the possibilities for such re-orderings.

Thesis (Ph.D.)--Murdoch University, 2003. / Thesis submitted to the Division of Arts. Bibliography: p. 273-289.

[Truncated abstract] Insufficient water use by annual crop and pasture species leading to costly rises in saline watertables has prompted research into potentially profitable deep-rooted perennial species in the Western Australian wheatbelt. Native mallee eucalypts are currently being developed as a short-rotation coppice crop for production of leaf oils, activated carbon and bio-electricity for low rainfall areas (300—450 mm) too dry for many of the traditional timber and forage species. The research in this study was aimed at developing a knowledge base necessary to grow and manage coppiced mallee eucalypts for both high productivity and salinity control. This firstly necessitated identification of suitable species, climatic and site requirements favourable to rapid growth, and understanding of factors likely to affect yield of the desirable leaf oil constituent, 1,8-cineole. This was undertaken using nine mallee taxa at twelve sites with two harvest regimes. E. kochii subsp. plenissima emerged as showing promise in the central and northern wheatbelt, particularly at a deep acid sand site (Gn 2.61; Northcote, 1979), so further studies focussed on physiology of its resprouting, water use and water-use efficiency at a similar site near Kalannie. Young E. kochii trees were well equipped with large numbers of meristematic foci and adequate root starch reserves to endure repeated shoot removal. The cutting season and interval between cuts were then demonstrated to have a strong influence on productivity, since first-year coppice growth was slow and root systems appeared to cease in secondary growth during the first 1.5—2.5 years after cutting. After decapitation, trees altered their physiology to promote rapid replacement of shoots. Compared to uncut trees, leaves of coppices were formed with a low carbon content per unit area, and showed high stomatal conductance accompanied by high leaf photosynthetic rates. Whole-plant water use efficiency of coppiced trees was unusually high due to their fast relative growth rates associated with preferential investments of photosynthates into regenerating canopies rather than roots. Despite relatively small leaf areas on coppice shoots over the two years following decapitation, high leaf transpiration rates resulted in coppices using water at rates far in excess of that falling as rain on the tree belt area. Water budgets showed that 20 % of the study paddock would have been needed as 0—2 year coppices in 5 m wide twin-row belts in order to maintain hydrological balance over the study period. Maximum water use occurred where uncut trees were accessing a fresh perched aquifer, but where this was not present water budgets still showed transpiration of uncut trees occurring at rates equivalent to 3—4 times rainfall incident on the tree belt canopy. In this scenario, only 10 % of the paddock surface would have been required under 5 m wide tree belts to restore hydrological balance, but competition losses in adjacent pasture would have been greater