Resource Management and Geography - Research Publications
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ItemCauses of pattern in plant communities where environmental change is rapid and species longevity is short(Opulus Press, 2006)Questions: To what extent can spatial structure and its causes be determined in a highly disturbed environment? What are the main determinants of pattern and are these species-specific? How much do spatial patterns change over generations? Location: Wimmera region of southern Australia. Methods: Broad-leaved weeds were counted in 225 000 contiguous 20-cm square quadrats. A substantial number of these quadrats were recorded again after two and four years. An hierarchical ‘adaptive analysis’ approach was used to select spatial analytical methods to examine specific aspects of pattern and variation in pattern from year to year. Results: Patterns varied among species and included both dense and sparse patches surrounded by areas of zero density, diffuse gradations of density and clear anisotropy. Patterns in Erodium botrys and Oxalis pes-caprae persisted over years, whereas patterns in Arctotheca calendula were less pronounced and varied over time. Edaphic factors appeared to have only a minor influence over the spatial distribution of the weed community as a whole. In Oxalis pes-caprae, whose patches were hypothesized to have been shaped by cultivation, there was no spread in four years, despite further tillage. Outlying plants of O. pes-caprae failed to establish new patches, even in the year of greatest population increase. Little evidence of localised recruitment events was found. Conclusions: Despite repeated annual disturbances by natural and anthropogenic mechanisms, clear and interpretable spatial structure develops in annual weeds over a range of spatial resolutions. Adaptive analysis is a useful approach to the characterization of such patterns.
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ItemAre the spatial patterns of weeds scale-invariant?( 2004)In previous empirical and modelling studies of rare species and weeds, evidence of fractal behaviour has been found. We propose that weeds in modern agricultural systems may be managed close to critical population dynamic thresholds, below which their rates of increase will be negative and where scale-invariance may be expected as a consequence. We collected detailed spatial data on five contrasting species over a period of three years in a primarily arable field. Counts in 20x20 cm contiguous quadrats, 225,000 in 1998 and 84,375 thereafter, could be re-structured into a wide range of larger quadrat sizes. These were analysed using three methods based on correlation sum, incidence and conditional incidence. We found non-trivial scale invariance for species occurring at low mean densities and where they were strongly aggregated. The fact that the scale-invariance was not found for widespread species occurring at higher densities suggests that the scaling in agricultural weed populations may, indeed, be related to critical phenomena.
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ItemAdapting to climate change in Pacific Island countries: the problem of uncertainty(Elsevier, 2001)This paper investigates the problem of scientific uncertainty and the way it impedes planning for climate change and accelerated sea-level rise (CC & ASLR) in Pacific Island Countries. The paper begins by discussing the problems CC & ASLR poses for Pacific Island Countries, and it explores the limitations of the dominant approach to vulnerability and adaptation. Next, the paper considers the way scientific uncertainty problematises policies aimed at adaptation to CC & ASLR. It argues that the prevailing approach, which requires anticipation of impacts, is unsuccessful, and the paper proposes a complementary strategy aimed to enhance the resilience of whole island social-ecological systems. Recent developments in the theory and practice of resilience are discussed and then applied to formulate goals for adaptation policy in Pacific Island Countries.