Please use this identifier to cite or link to this item: https://une.intersearch.com.au/unejspui/handle/1959.11/2391
Title: Within- and between-habitat coexistence in mulga ('Acacia aneura') shrubland-spinifex ('Triodia' spp.) hummock grasslands mosaics in central Australia
Contributor(s): Nano, Catherine Elspeth Mary (author); Clarke, Peter John (supervisor); Albrecht, David (supervisor)
Conferred Date: 2006
Copyright Date: 2005
Open Access: Yes
Handle Link: https://hdl.handle.net/1959.11/2391
Abstract: Mulga ('Acacia aneura') and spinifex ('Triodia' spp.) habitats together characterise a large part of arid central Australia. Often very abrupt boundaries form between these two habitats, giving rise to a mosaic pattern of contrasting shrub-grass alterations across the landscape. Reports of a recently-initiated fire-driven conversion of mulga shrubland to spinifex grassland have created concern for the long-term stability of these mosaics. In spite of their prevalence and potential vulnerability, mulga-spinifex mosaics have so far attracted relatively little research attention, and our understanding of pattern and process in these systems is consequently rudimentary. Indeed, evidence for mulga contraction per se is, at present, scant and somewhat contradictory, meaning that there is currently little opportunity to properly resolve the issue of possible boundary shifts. Recognising these limitations, this thesis was primarily concerned with the identification of the processes currently mediating within- and between-habitat coexistence in mulga-spinifex mosaics. This was undertaken with a view to providing quantitative data for the refinement of existing predictive models for mulga-spinifex distribution shifts, and for understanding central Australian arid plant community dynamics more generally. The study commenced with an account of field survey work that was undertaken in central Australian mountain range mosaics. This work was aimed at the further characterisation of mosaic floristic patterns, and at directly relating observed patterns to environmental gradients. The results indicated that shrub-grass alterations in mountain range mosaics primarily reflect local- and regional-scale edaphic gradients. On the strength of this finding, it was argued that both broad- and fine-scale floristic patterns in this setting can be most readily accounted for by invoking the related notions of non-overlapping niche-space and habitat heterogeneity. It was also shown however, that there are certain situations where this edaphic-model cannot adequately account for patterning, and that here, alternative processes need to be considered. Those most apparent from the floristic data were: fluctuating disturbance (i.e. variable firing), competitive exclusion, facilitation by established 'A. aneura' shrubs, and dispersal constraints. Follow-up survey work in central Australian dunefields examined the extent to which the themes identified for range mulga-spinifex boundaries could be applied to mosaic regulation more generally. The results indicated that while dunefield mulga-spinifex mosaics differ in detail from those in the range setting, there is a high level of commonality in terms of the processes regulating boundary formation and maintenance.
Publication Type: Thesis Doctoral
Rights Statement: Copyright 2005 - Catherine Elspeth Mary Nano
HERDC Category Description: T2 Thesis - Doctorate by Research
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