PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



157 



— 35 C 



9 10 11 12 13 14 



Fiqube 7. — Germination of Eremophila gilesii fruits at 

 fixed temperature in the dark. Data presented ± stand- 

 ard error. Fruits had been field weathered, and were 

 estimated to be 3 years old. 



within 1 or 2 days of most summer rains. The 

 expected failure of E. gilesii to germinate during 

 summer was borne out by field observations in 

 this study. However, temperature relationships 

 alone are not sufficient to explain behavior in the 

 field because dormancy and moisture are also in- 

 volved (21). 



Conclusions 



These studies have shown the following : 



E. gilesii is restricted in distribution to those 

 areas receiving both summer and winter rainfall 

 (fig. 1). 



Light stocking rates are resulting in further 

 increase in E. gilesii (table 1). 



Fruit production may only be significant fol- 

 lowing suitable rains (>40 mm.) in the cooler 

 months of the year (fig. 4). 



Frequent flowering in summer is not necessarily 

 followed by abundant fruit production (figs. 3, 



4). 



High germination percentages occur following 

 protracted fruit weathering in the field (fig. 6). 



Germination may be severely inhibited by soil 

 temperatures in excess of 40° C. (fig. 7). 



With the use of this information, a hypotheti- 

 cal management system for E. gilesii may be 

 formulated. It is proposed that from March to 

 September inclusive land on which E. gilesii is a 

 weed should be heavily stocked following falls of 

 rain greater than 40 mm. A stocking rate of at 

 least 2 sheep per hectare is envisaged for a pe- 



riod of 4 weeks commencing about 2 weeks after 

 the rain falls. It is anticipated that this would 

 have the effect of removing both flowers and 

 many of the young seedlings. This practice, re- 

 peated over a number of years, could severely 

 curtail reestablishment and lead eventually to a 

 decline of the stand. Damage to grass would be 

 minimal as growth and seed germination in these 

 communities occurs in response to summer rather 

 than winter rains (45)- Light stocking during the 

 summer months would encourage grasses to fill 

 niches created as E. gilesii gradually declines in 

 density. Everist (personal communication) con- 

 siders individual E. gilesii plants have life spans 

 of little more than 10 years. 



The problems of brush control in semiarid 

 grazing lands is complex. Wilson (46) has point- 

 ed out the lengthy time scale involved in con- 

 verting areas occupied by shrubs and trees to 

 stable grassland. Unpalatable woody species may 

 serve a useful purpose in providing ground cover 

 and erosion protection (20) in areas otherwise 

 denuded of grass and herbage. Removing the 

 shrubs without consideration of what species, if 

 any, will take their place could lead to further 

 deterioration in the grazing value and stability 

 of the ecosystem. Unless this is fully appreciated, 

 the usefulness of any control measure could be 

 negated. 



Literature Cited 



(1) Beadle, N. C W. 



1948. THE VEGETATION AND PASTURES OF WESTERN 

 NEW SOUTH WALES WITH SPECIAL REFERENCES 



to soil erosion. Government Printer, Sydney. 

 279 pp. 



(2) Blaisdell, J. P. 



1965. GROWTH AND YIELD OF SAGEBRUSH GRASS VEGE- 

 TATION IN RELATION TO PRECIPITATION AND TEM- 

 PERATURE. Proc. 9th Internatl. Grassl. Cong. 

 Sao Paulo, Brazil. 1: 465-468. 



(3) Burrows, W. H., and I. F. Beale. 



1969. STRUCTURE AND ASSOCIATION IN THE MULGA 

 (ACACIA ANEURA) LANDS OF SOUTH WESTERN 



Queensland. Austral. J. Bot. 17 : 539-552. 



(4) Chew, R. M., and A. E. Chew. 



1965. THE PRIMARY PRODUCTIVITY OF A DESERT SHRUB 

 (LARREA TRIDENTATA) community. Ecol. 

 Monog. 35: 355-375. 



(5) Chippendale, H. G. 



1949. environment and germination in grass seed. 

 J. Brit. Grassld. Soc. 4: 57-61. 



