Accueil du site
Doctorat
Australie
2001
Grazing impacts in rangelands : assessment of two contrasting landscape types in arid Western Australia from different land management perspectives
Titre : Grazing impacts in rangelands : assessment of two contrasting landscape types in arid Western Australia from different land management perspectives
Auteur : Pringle, Hugh John Robert
Université de soutenance : Australian National University
Grade : Doctor of Philosophy (PhD) 2001
Résumé partiel
Regional patterns of land use and systems for assessing the "health" of rangelands have not
changed their focus from production of meat and fibre, despite ecologically sustainable
development becoming the dominant environmental paradigm. In this study I evaluated i)
traditional range condition assessment as practised in Western Australia, and explored its
capacity to predict changes in ii) biodiversity and iii) landscape patterns and processes
along grazing gradients in two contrasting landscape types.
I estimated grazing history using a commercially available model and a model based on
sheep track density. Although distance from water was a more simple proxy for grazing
history, it did not account for as much of the systematic variation in environmental response
as either model.
Range condition declined with increased grazing in both landscape types, and while the
decline was more marked in mulga landscapes, range condition assessments may
overestimate degradation in this landscape.
Approximately one quarter of plant species were "decreasers" that declined in abundance
with increased grazing, compared to 16% that were "increasers". The number of decreaser
species also declined with grazing, more rapidly in mulga landscapes than chenopod
landscapes.
Over a third of ant species (not including singletons) were decreasers in chenopod
landscapes. Increaser species in chenopod landscapes, and both decreasers and increasers in
mulga landscapes, comprised a relatively minor component of the ant fauna. The sensitivity
of the ant fauna to grazing in chenopod landscapes contrasts strongly with conclusions from
previous studies in north American rangelands.
Overall, grazing suppressed the capacity for landscapes to redistribute and conserve
resources in fertile patches. Chenopod landscapes were most profoundly altered : with
increased grazing fertile bush mounds decreased in density and proportional area as open
areas expanded and became more saline.
Page publiée le 25 mars 2006, mise à jour le 17 janvier 2021