PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



63 



Figure 3. — Shrub steppe in Australia ; Eochia pyramidata Benth., short grasses, and forbs. 



Hall and others (9) drew attention to the 

 changes which can be expected as a result of the 

 overuse of shrubland pastures, particularly since 

 characteristics such as the capacity to fruit readi- 

 ly, to have a high percentage of hard-seededness, 

 and to have a high germinability are not pos- 

 sessed equally by all 'species. Along with differ- 

 ential palatability, these characteristics combine 

 to produce striking changes in vegetation expres- 

 sion. Alterations in seedbed conditions under 

 grazing also contribute to changes in pasture 

 structure. Carrodus is quoted by Hall (9) as stat- 

 ing that water infiltration rate has a significant 

 effect on the germination and establishment of 

 K. sedifolia, though I. Noble (private communi- 

 cation) attributes a decline in the germination 

 and establishment of this species to a drop in total 

 soil nitrogen in the surface 1 cm. of soil. However, 

 both these features may be symptomatic of a 

 total decline in seedbed conditions brought about 

 by incorrect grazing management. 



Table 1 shows the pattern through time of the 

 contributions made to pasture by different com- 

 ponents in a halophytic community. The data are 

 that from an Atriplex-Kochia community in a 

 200 to 250 mm. rainfall area in Western Aus- 



tralia (Wilcox unpublished). Under conditions 

 of low rainfall, the contribution of the ground 

 flora is inadequate to maintain sheep even at the 

 low stocking rate of one sheep to 10 or 12 hec- 

 tares, common in these areas. Grazing animals 

 must rely upon woody shrubs during these periods 

 of stress. 



Condon (5) and Ratcliffe (25) refer to the 

 disappearance of extensive areas of valuable 

 shrub species such as saltbush (Atriplex) and 

 bluebush (Kochia) in western New South Wales 

 and South Australia. Similar trends have been 

 observed in Western Australia. These genera 

 were considered to form the most important na- 

 tive pasture for sheep grazing, and their dis- 

 appearance was considered to be responsible for 

 a decline in productivity on the range. Osborn 

 and others (23) in South Australia suggested 

 that severe overuse of an A. vesicaria pasture 

 by sheep resulted in complete removal of peren- 

 nial cover in a zone immediately about a water- 

 ing point. They recognized four zones of use 

 extending away from the watering point till, at 

 distances of about V/i miles, dependent upon 

 topography, a zone of little use characterized by 

 moribund and senescent plants was reached. 



