The temperate to arid transition of the Irwin – Carnarvon phytogeographic boundary, Western Australia

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – The southern boundary of the Carnarvon phytogeographic district separates the arid Acacia shrublands from the species rich heaths and woodlands of the Irwin region. This boundary has previously been mapped at a scale of 1 : 250000 using the structure, density and composition of the dominant perennial plant species. One hundred quadrats were established across this boundary to determine if floristic composition correlated with the mapped position of this boundary. Our results suggest that the boundary of the Southwestern Botanical Province should move west and south to exclude the Acacia - Casuarina thicket on red sandplain and the tree heaths south of Shark Bay. In terms of species and family composition the vegetation of these areas is more similar to typical Carnarvon vegetation than to the scrub heaths of the yellow sandplains of the Irwin. Major edaphic patterns are strongly correlated with the position of the revised boundary.