Paper No. 6 



MORPHOGENESIS AND MANAGEMENT OF WOODY PERENNIALS IN 



AUSTRALIA 



By D. G. Wilcox 1 



Abstract 



The location and condition of shrub range- 

 lands in Australia are described. The criteria for 

 the germination and the establishment of Atri- 

 plex (saltbush) and Kochia (bluebush) species 

 are reviewed. The significance of these genera to 

 range forage is discussed in relation to grazing 

 pressure and specific characteristics which deter- 

 mine their survival in the pastoral environment. 

 Acacia shrublands are described with particular 

 reference to A. aneura (mulga) and its require- 

 ments for germination, survival and mainte- 

 nance. The productivity of these shrublands is 

 reviewed. 



Additional Key Words: Australian shrub range- 

 lands, management, Atriplex, Kochia, Acacia, 

 productivity 



Introduction 



Pastures in which shrubs are important in 

 Australian . rangelands lie in a region receiving 

 between 150 and 500 mm. of annual rainfall, a 

 large part of which falls in winter but which is 

 always characteristically erratic in incidence. 

 Most of these pastures lie south of an arbitrary 

 winter-summer rainfall dominance line adapted 

 from Perry (2 J/.) and J. McAlpine (private com- 

 munication). An area of shrubby pasture in 

 which Acacia aneura F. Muell. is important lies 

 just to the north of this line, but in this region 

 winter rainfall is still effective and comparatively 

 reliable. Another area of shrubby pasture is 

 found further north on the Barkly Tableland 

 where Chenopodium auricomwn Lindl. (northern 



1 Agricultural Adviser, North West Division, Depart- 

 ment of Agriculture, South Perth, Western Australia. 

 6151. 



60 



bluebush), is determined in its occurence by 

 seasonal flooding and is strongly limited by soil 

 type (30). Shrubland distribution is shown in 

 figure 1. 



Perry (24) and Moore and others (21) de- 

 scribed the shrubland pastures in Australia. 

 Perry discussed the arid zone pastures falling 

 within the categories of shrub steppe, acacia 

 shrublands, and low arid wQodlands (figs. 2 and 

 3). Moore described the semiarid woodlands, com- 

 munities which lie between the arid zone and the 

 mesophytic grazing and farming land where 

 introduced pastures may be sown. Eucatyptus. 

 acacia, and casuarina form an irregular overstory 

 in these communities, above variable stands of low 

 shrubs and grasses which change according to 

 soil type and average annual rainfall. 



Rainfall exerts an overwhelming influence upon 

 the total production available in shrub communi- 

 ties, creating peaks and abysses of production 

 coincident with rainfall variation. Perry (24) re- 

 fers to the bare spaces which occur between shrubs 

 in shrub steppe during frequent long, dry pe- 

 riods, and to the ephemeral nature of much of 

 the ground layer in other communities. In pro- 

 longed dry periods the shrub components provide 

 the only fodder available to grazing animals. The 

 shrubland pastures of the Riverine Plain in New 

 South Wales, described by Leigh and others (15, 

 16, 32, 33) in a number of papers, appear to differ 

 from the remainder of shrubland zone since the 

 associated Danthonia, Stipa and forbs present 

 provide an almost stable alternative diet to shrubs 

 in this 300 to 500 mm. rainfall region. 



Moore (20) suggested that use of the Aus- 

 tralian shrubland pastures has followed a pattern 

 that was not always definable in precise se- 

 quence but which involved quite clear steps. Ini- 

 tially, the most palatable species were heavily 

 grazed and even removed. This was followed by 



