Southern Basins and Ranges (Environmental Region 6.1)
This region consists of 17 environmental associations. It includes the southern and central parts of the province and is characterized by series of high quartzite hogback ridges with shallow loamy soils and intervening plains and lowlands with red duplex soils. Particularly to the south intermontane plains are extensive, commonly with flat alluviated floors. Although the vegetation of this region is largely natural, the long history of attempts at agriculture, and the disturbance caused by the establishment of a pastoral industry, have resulted in extensive changes in the composition of communities, and in species distribution. The vegetation of the hogback ridges has been the least altered. Native pine (Callitris columellaris), mallee (E. socialis, E. oleosa and E. brachycalyx) and black oak (Casuarina cristata) are the dominant canopy species on the slopes of these ridges, although in the south these communities merge with eucalypt forests dominated by sugar gum (E. cladocalyx), long-leaved box, (E. goniocalyx) and blue gum (E. leucoxylon). The understory of the ridges is generally sparse, with scattered shrubs which include hopbush (e.g. Dodonaea attenuata), wattles (e.g. Acacia rivalis) and porcupine grass (Triodia irritans), giving way near the summits to yacca (Xanthorrhoea semiplana). The lower ridges and hills have a variety of communities, altered in many places by clearing. In the south, mallee occurs on uncleared parts, dominated by red mallee (E. oleosa) and peppermint box (E. odorata). The canopy also includes mallee box (E, porosa), native cherry (Exocarpus aphyllus and Exocarpus sparteus) and scattered specimens of false sandalwood (Myoporum platycarpum). In the understory, wattles (e.g. Acacia pycnantha, A. oswaldii), hopbush (Dononaea attenuata) and needlebush (Hakea leuoptera) are prominent, with a ground flora of grasses, forbs and chenopod shrubs (e.g. Rhagodia parabolica and Enchylaena tomentosa). A number of the understory of species are more common in adjacent cleared fields where they appear to be colonizing disused pasture land. In the west these include needlebush, hopbush, birdseye (Cassia eremophila) and Templetonia sp. In the east, elegant wattle (A. victoriae), native fuchsia (Eremphila spp.) and Templetonia sp. are common. On many of the low ridges and hills in the north of the region, mallee gives way to a woodland of native pine and black oak, a tall shrubland or hopbush, birdseye and elegant wattle, or a chenopod shrubland of bluebush (Maireana spp.) and saltbush (Atriplex spp.). The distribution of these communities is extremely variable apparently depending on clearing and subsequent recolonization, as well as soil depth and water factors. The intervening plains are equally complex. Some crops are still grown in the south, and many areas once cleared for crops show no sigh of recolonization, possibly due to grazing pressure. Other previously cleared areas however, particularly in the east and central north, have dense strands of low shrubs such as elegant wattle and another wattle (A. oswaldii) which may be invading degraded chenopod shrubland. The lower-lying parts of these plains still have communities of salt-tolerant nitrebush (Nitraria schoberi) and bluebush (Maireana pyramidata), and the channels are fringed by river red gum (E. camaldulensis), coolibah box (E. intertexta), occasionally mallee box, and in the north the teatree Melaleuca glomerata. The views consist primarily of foreground to middleground panoramas and perspectives, dominated by abruptly rising ridges, many in the north and west with broken rugged skylines. Watercourses, particularly those which cut through the ridges, provide detailed views, often enclosed by steep rocky walls or dense creek vegetation. The ridges and hills themselves provide panoramic views. A major contributing factor to the visual resources of the region is the strong colourings of the rock outcrops and ephemeral forbs and the variable combinations and contrasts of these occurring in different seasons or at different times of the day. The climate is mild to hot in summer and cool to cold in winter. Rainfall is low and unreliable throughout the year, with the highest monthly falls generally occurring in winter (June to August). Mean annual rainfall increases from 150 mm in the north-east and north-west to over 350 mm in the central areas of more rugged topography. Mean annual evaporation increases from 2200 mm in the south to about 3000 mm in the north. Mean monthly evaporation reaches about 350 mm in January and exceeds the 90th percentile of monthly rainfall for every month. Temperatures show considerable diurnal and seasonal variation.
