PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



131 



rains are probably required to allow new stands 

 of Mitchell grass to develop, although it is not 

 known whether Mitchell grass will reestablish in 

 competition with the vigorous annual commu- 

 nity which replaces it. Another possible excep- 

 tion to the general picture of stability in Mitch- 

 ell grass communities is the increase in less de- 

 sirable bunch grasses, particularly Aristida lati- 

 folia, in some areas in Queensland (29). 



Chenopod Shrublands 



The chenopod shrublands (figure 3) are re- 

 stricted to "southern Australia where, on the 

 average, summer rains account for 50 to 70 per- 

 cent of the annual total, but winter rains are 

 more reliable and effective. The shrublands are 

 dominated by various species of Atriplex and 

 Kochia (2, 12, 13, 32), and are structurally 

 somewhat similar to sagebrush communities in 

 U.S.A. As with Mitchell grass communities, 

 stock graze the annuals produced between the 

 shrubs following rains; but during long dry 

 periods, the less palatable shrubs provide a 

 reserve of forage (15, 16). 



The chenopod shrublands of the Riverine 

 Plain (figure 1) in southern New South Wales 

 are quite different from those of other areas. 

 Here they occur under a mean annual rainfall 

 between 250 and 400 mm., on flat plains of fine- 

 textured clay soils similar to those of the Mitch- 

 ell grass rangelands, and with a similar low 

 erosion hazard. Rainfall is relativelv high and 



reliable, as is the stocking rate (1 sheep to be- 

 tween 1 and 2 hectares). Because of this, the 

 Riverine Plain carries about half the total stock 

 carried on all shrublands, although its area is 

 small compared with the total. On the higher 

 rainfall part of the Plain, grazing in the past 

 has converted the shrublands into a disclimax 

 perennial grassland (dominated by Danthonia 

 caespitosa and Stipa variabilis) , which is as pro- 

 ductive as the original community (36, 37). On 

 these parts, and on other areas of the Plain 

 where it can be demonstrated that a grassland 

 will be produced, the shrubs can be considered 

 as undesirable and management can be aimed 

 at reducing or eliminating them. This is simple, 

 as it has been shown that a single complete de- 

 foliation is sufficient to kill Atriplex vesicaria 

 (17), which dominates most of the nongrass part 

 of the Plain. 



Most of the chenopod shrublands are differ- 

 ent from those of the Riverine Plain. They occur 

 under a mean annual rainfall less than 250 mm., 

 on undulating terrain with mostly texture-con- 

 trast or coarse to medium textured calcareous 

 soils. Stocking rates do not exceed 1 sheep to 4 

 hectares and are as low as 1 sheep to 15 hectares. 

 If the shrub cover is destroyed, a bare landscape 

 with an ephemeral cover following rains is left. 

 Erosion hazard is high, and it is essential to 

 maintain a stand of vigorous shrubs adequate 

 to protect the landscapes and to provide re- 

 serve forage during long droughts. In saltbush 

 communities, the aforementioned ease of killing 



Figuee 3. — Shrubland of Kochia pyrimadata. 



