Pilbara shrublands


The Pilbara shrublands is a deserts and xeric shrublands ecoregion in Western Australia. It is coterminous with the Pilbara IBRA region. For other definitions and uses of "Pilbara region" see Pilbara.

Geography

The Pilbara shrublands is bounded on the north by the Indian Ocean, and on the west, south, and east by other deserts and xeric shrubland ecoregions - the Carnarvon xeric shrublands to the west, the Western Australian mulga shrublands to the south, and the Great Sandy-Tanami desert to the east and northeast.
The Pilbara geographic region covers most of the ecoregion, and extends east into the Great Sandy desert.
The Hamersley Range, a region of mountain ranges and plateaus dissected by gorges, lies in the southern portion of the ecoregion. The Fortescue Plains extend east and west to the north of the Hamersley Range, forming the upper basin of the Fortescue River. The Chichester Plateau lies north of the Fortescue Plains. The Roebourne subregion includes the coastal plain along the Indian Ocean.
The ecoregion lies on the Pilbara craton, a block of ancient Archean rock. The Chichester region is characterized by exposed granite and greenstone basement rocks. The Hamersley region includes iron-rich carbonate sedimentary carbonate rocks over a volcanic substrate which rest on the older craton. The Fortescue basin and coastal plain are alluvial.

Climate

The climate is tropical semi-desert. Rainfall averages 300 mm annually, typically from summer cyclonic storms and thunderstorms.

Flora

In the Hamersley region, mulga woodland occurs on fine-textured valley soils, with Acacia aneura over the grasses Aristida spp. and Enneapogon spp. Snappy gum occurs with the grass Triodia brizoides on the skeletal soils of the ranges.
The Fortescue Plains include the northernmost mulga woodlands, along with short grasslands. Year-round watercourses and springs support stands of red river gum,, Melaleuca. and the palm Livistona alfredii. Sheltered gorges along the edge of the Chichester Plateau provide water and protection from fire, and support relict communities of Terminalia, Erythrina, and Ficus.
The Chichester Plateau is principally scrub steppe, with the shrub Acacia inaequilatera and the bunch grass Triodia wiseana. Scrub steppe also dominates the Roebourne coastal plain, with Acacia translucens and Triodia pungens.

Subregions

Protected areas

Protected areas in the ecoregion include Karijini National Park and Millstream-Chichester National Park.