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MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



Atriplex vesicaria makes it difficult to maintain 

 stands. On the other hand, it has been shown 

 that moderately heavy grazing improves the 

 vigor and health of Atriplex vesicaria stands 

 (23). As seedlings of saltbush establish follow- 

 ing autumn rains (4), it is likely that rest per- 

 iods at such times will result in better stands. 

 However in Western Australia, Wilcox (private 

 communication) has observed that winter use 

 and summer rest has resulted in better stands 

 of Atriplex paludosa, A. rhagodioides, and Ko- 

 chia pyramidata than yearlong grazing at similar 

 intensities. He has no observations on summer 

 use and winter rest, which may be even better. 



With some of the other shrub species, the 

 original shrub cover was so dense that herba- 

 ceous production between the shrubs was in- 

 hibited. In such cases, some reduction in shrub 

 density is warranted (12). Thus the various 

 shrubland communities provide good examples 

 of managing for a balance between species; the 

 aim being to maintain stands of vigorous shrubs, 

 open enough to get as much herbaceous produc- 

 tion as possible. A means of assessing this bal- 

 ance, in terms of the physical protection afforded 

 by the shrubs, has been proposed by Marshall 

 (19). 



The management problem is to maintain a 

 balance between enough low trees and bushes to 

 provide landscape protection and reserve forage 

 for long dry periods, and an open enough stand 

 to allow a good ground cover to develop after 

 rains. Because of the many different species in- 

 volved, the wide range of climate and land en- 

 vironments, and the large variation in present 

 condition, the actual management strategies re- 

 quired differ greatly from place to place. This 

 can be illustrated by reference to mulga (Acacia 

 aneura), which is the most widespread and best 

 known of the dominant low trees. In the south, 

 most areas of mulga country are in poor or 

 very poor condition; the tree cover has greatly 

 decreased to a few scattered old trees or none 

 at all, ground cover has also decreased, and 

 some areas have been reduced to bare scalds or 

 surface sand drifts. The reduction in trees is 

 generally attributed to lack of recruitment of 

 young trees into the population (6), probably 

 because young seedlings are consumed by sheep 

 or rabbits. From our knowledge of the biologv 



of mulga (Acacia aneura), it appears that estab- 

 lishment requires a long sequence- of events to 

 ensure flowering, seed set, breaking of dormancy, 

 and germination (10). In the south, the condi- 

 tions apparently occur infrequently. Rest fol- 

 lowing such occurrences may allow regeneration, 

 although rabbits probably would need to be 

 controlled also. These southern areas of mulga 

 country clearly require management practices 

 for stabilizing the soil surface, increasing the 

 tree cover to an adequate level, and increasing 

 the ground cover; in many cases mechanical 

 treatments will be required to aid regeneration. 

 Large areas of the chenopod shrublands have 

 been reduced to poor or very poor condition, and 

 some areas are severely eroded. Because of this, 

 the main direction of management should be 

 towards regeneration, and in many cases this 

 will not be achieved by grazing management 

 alone ; mechanical treatments, with or without 

 reseeding. will be required. 



Low Woodlands 



Low woodlands (figure 4) are widespread 

 throughout all the rangelands, except the far 

 north, and cover nearly a third of the total area 

 (2, 3, 12. 13, 24, 32). Mean annual rainfall ranges 

 from 125 to 500 mm. Relief varies from flat to 

 undulating, and soils from coarse to medium 

 textures. Sensitivity to erosion varies from high 

 on undulating country to very slight on flat 

 areas on old Tertiary land surfaces. Many dif- 

 ferent communities, dominated by various spe- 

 cies of Acacia and other trees of similar stature 

 (for example, Heterodendrum oleifoVmm and 

 Casuarina cristata), are included. The trees 

 range from about 2 to 10 meters in height. 

 There is commonly a scattering of shrubs and 

 a ground cover of mostly annual grasses and 

 forbs, with a perennial grass component in some 

 areas. It is possible that perennial grasses were 

 originally more widespread and that the low 

 tree/annual communities are a degenerate stage. 

 Structurally, many of the communities super- 

 ficially resemble mesquite rangelands in the 

 United States. 



Following rains, stock graze the ground cover 

 but, in long dry periods, are maintained by 

 browsing the bushes and low trees, which ma} - 



