Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Ecology and spatial modelling of kangaroo populations in mosaic landscapes of Queensland’s semi-arid rangelands

Auteur : McAlpine, Clive A.

Université de soutenance : University of Queensland

Grade : Doctor of Philosophy (PhD) 1997

Résumé partiel
The study utilises landscape ecology concepts and methods to explain the relationship between the structure and productivity of Queensland’s disturbed semi-arid woodland landscapes and the density distribution of eastern grey kangaroos (M. giganteus), red kangaroos (M. rufus) and common wallaroos (M. robustus). The outcomes of the study indicate that human induced landscape disturbance patterns are a major causal factor influencing the density distribution of each species at the property level in the region. Water was not a significant limiting factor, although it may be locally important. Grey kangaroos prefer a fine grained, functional combination of forage and shelter habitat resources. This combination has been created by the partial clearing of Acacia woodlands on fertile soils for improved pastures. Red kangaroos are positively associated with large shrub-regrowth disturbance patches and run-on areas, reflecting their forage preference for herbage and short grasses. Wallaroos have a clumped density distribution influenced by a preference for a spatial heterogeneity of open habitats interspersed with fine grained, often fragmented, forest patches and medium sized shrub-regrowth disturbance patches. These relationships are captured in a suite of spatial habitat models for accurately predicting species densities on rangeland properties.

Derivation of the outcomes depended upon the development of spatially explicit concepts and methods for : (i) conceptualising environmental patterns and ecological processes ; (ii) estimating species spatial and seasonal density patterns ; and (iii) detecting, quantifying and confirming environmental patterns of influence.

Current large macropod research methods, developed largely in the temperate chenopod rangelands of southern Australia, adopt an organism or community approach to examine species­ environment relationships. The semi-arid mosaic of woody and non-woody habitat elements which characterise Queensland’s disturbed woodlands require a different approach. Landscape ecology, supported by spatial technologies, offered a better way to consider the influence of both the ’natural’ and human-altered patterns of these mosaic landscapes on kangaroo population densities in spatially explicit terms. A hierarchical, landscape approach was employed to integrate existing large macropod and range ecology research knowledge into a single conceptual­ empirical structure. This structure was used to explain causal relationships between species density patterns and landscape structure and productivity at different ecological levels of influence.

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