Central Mallee Plains and Dunes (Environmental Region 4.3)
This region consists of 26 environmental associations. It is the largest in the province and extends across Eyre Peninsula from its western extremity to Spencer Gulf. It is distinguished climatically by being more arid than regions to the south, and this is reflected in the vegetation. Mallee, which occurred throughout the region, has been cleared for wheat cultivation. The northern margin is formed by the dune fields of the Great Victoria Desert and the eastern margin of the Gawler Ranges. The region is essentially an undulating plain with an extensive cover of dunes and sand sheets. The dunes are inactive but agricultural use has made them highly susceptible to wind erosion. A red mallee-yorrell association (E. socialis - E. gracilis) occurs on the shallow calcareous earths or deeper duplex soils of the plains, with mallee broombush (E. incrassata - Melaleuca uncinata) on the dune sands. In the east the region includes hilly uplands on metasediments with small intramontane basins. Structurally these uplands are a continuation of the uplands in region 4.1, and have shallow loams with much rock outcrop. Isolated quartzite ranges and granite outcrops form prominent inselbergs such as Darke Peak and Wudina Hill which occur throughout the region. Throughout this region foreground and middleground panoramic views prevail, commonly with hills and inselbergs as local features. In turn, these hills and inselbergs, and also the high dunes, provide background panoramic views over the plains, The inselbergs also have detailed views of rock formations and vegetation communities, varying according to their geology. Large tracts of mallee remain in this region and afford enclosed and detailed views. The hills north of Cleve (associations 4.3.10 and 4.3.11) as well as forming a backdrop to views from the plain, provide foreground enclosed and perspective views from the crests. The coastline, especially in the west, has a varied landscape. High mobile dunes are dominating features where they occur, and salt lakes, lagoons and tidal flats provide enclosed and detailed views. Occasional cliffs afford panoramic views along the coastline and over the ocean with offshore islands as features. The region has a mild to warm climate with a winter rainfall maximum and high summer evaporation. Mean annual rainfall varies from about 425 mm near Cleve to about 250 mm along the north-eastern margin of the region, while mean annual evaporation increases from about 1900 mm to about 2400 mm over the same area. Mean monthly evaporation is very high in summer and exceeds the 90th percentile of monthly rainfall in all months but July. Temperatures are mild to warm in summer and cool to cold in winter.
