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

Titre : The response of birds to the fire regimes of mulga woodlands in central Australia

Auteur : Leavesley, Adam

Université de soutenance : Australian National University

Grade : Doctor of Philosophy (PhD) 2008

Résumé partiel
The fire mosaic hypotiiesis is intuitively appealing to scientists and land managers due to its perceived potential to deliver favourable outcomes for biodiversity conservation and fire management. However evidence in support of the biodiversity benefits of fine-scaled fire mosaics is scant. In this thesis I investigate the key assumptions of the fire mosaic hypothesis using a model system, the mulga woodland/mulga bird community of central Australia. Mulga woodland is an ideal model system for this question because it is structurally and floristically simple, yet supports a rich avifauna. I tested how avian diversity (variety and number) was influenced by 1) time-since-fire ; 2) patch size ; and 3) the boundary between burnt and unbumt mulga woodland (pyric edge). An investigation of time-since-fire is crucial for testing the fire mosaic hypothesis. If there is no effect of time-since-fire on biodiversity, then the spatial arrangement of different timessince-fire is irrelevant and the definition of habitat patches and habitat edges based on timesince-fire is not valid. Patch size and edge effect are potential mechanisms by which a fine-scale fire mosaic may support greater avian diversity than a coarse-scale fire mosaic. For this to be the case, avian diversity must increase with decreasing patch size ; or be greater at pyric edges than in the interior of habitats. Australian arid-zone landscapes are subject to two strong disturbance regimes, recent rain and fire. The effect of recent rain dominates the distribution of many birds, so much so that the influence of fire has been difficult to detect. To my knowledge, no properly replicated studies have succeeded in demonstrating an effect of fire on Australian arid zone birds. My study site is Uluru-Kata Tjuta National Park and neighbouring Yulara resort in central Australia. The study site is the subject of the longest running, most detailed fire history in the Australian arid zone. I minimized the confounding influence of recent rain by conducting space-for-time experiments. Two time-since-fire experiments were located in landscapes with contrasting geological and hydrological characteristics - a sheetwash landscape and a dune-swale landscape. I also conducted an edge experiment in the sheetwash landscape.

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