PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



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Effective Rainfall 



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Figure 6. — Fluctuations in leaf fall from mulga trees in Western Australia. 



to dense shrub woodlands with reduced produc- 

 tivity and increased run-off. In some cases, Moore 

 considers this to be due to a reduction in com- 

 petition as species such as palatable Acacia cam- 

 bagei R. T. Baker and perennial grasses are pre- 

 ferentially removed, thereby reducing the compe- 

 tition which would normally obstruct the expan- 

 sion of undesirable species. Overuse of the pal- 

 atable Casuarina cristata and Heterodendron 

 oleifolium Desf. during droughts is thought by 

 Moore to have reduced the vigor of these species 

 and to have allowed Dodonea attenuata to be- 

 come established. 



Summary 



Specific morphological characters emphasized 

 during the life of a woody perennial influence its 

 survival in range land. Two factors affecting the 



use of a species are palatability and accessibility 

 since they modify, in turn, the chances of survival 

 of a species and hence the vegetation structure 

 and then the productivity of a particular range 

 site. Apart from the work on the Riverine Plain, 

 there is little in the Australian literature on 

 woody perennials upon which to make judgments 

 on the value of a species or a community. It is 

 possible to extrapolate a form of management 

 process from some of the particular studies per- 

 formed on special plants in particular growth 

 stages, but none of these procedures has been 

 evaluated in the field where the whole complex of 

 plant-animal interaction is expressed. With rain- 

 fall so variable in amount and incidence, field 

 studies which aim at elucidating management 

 schemes must necessarily be conducted over ex- 

 tended periods which would cover the gamut of 

 rainfall expression. 



