PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



155 



100 

 "o 



If 75 

 S* 50 



Z 



25 







"o 



- e 20 

 Xi 



E° 10 

 Z 

 "o 

 !sJ5 100 



P 50 

 Z 



££250 



§-5! 150 

 Z 50 



= 50 



11 25 

 or — 







.11 llllllll, ...ll 



,1 







1 N.ll 







! 



, 



1,1, ll 



li... 





i 



llllllllll 1 



Illlh 





|, 



llllllllll 







, 









iJ. H. .1 1 1 



• 



111 ,. , 





NDJFMAMJ JASON 

 Month 



Figure 3. — Trends in numbers of leaves, flower buds, 

 flowers, and fruits on marked branches of Eremophila 

 gilesil during 1969-70. (>45 cm. height class). 



Walter (39) has stated that the water balance 

 of isolated plants in the desert is not as unfavor- 

 able as is usually believed. In effect, he suggests 

 that the density of vegetational cover is generally 

 proportional to precipitation so that, per unit of 

 transpiring surface, plants in arid areas receive 

 the same quantity of water as those in humid 

 climates. The soil moisture data presented in fig- 

 ure 5 for the E. gilesii community suggests that 

 Walter's conclusion may not be valid for E. gile- 

 sii. For many months of the year, soil moisture 

 to 1 m. depth is below the 15 atmosphere per- 

 centage. Similar results have been noted in other 

 arid communities (13, 32, 36). Nevertheless, Slat- 

 yer (35) cautioned against a too literal inter- 

 pretation of available soil water data. He points 

 out that increased rooting depth in the profile as 

 a whole can compensate for a narrow available 

 water range in each horizon. Also, in many soils, 

 the range of water available for transpiration 

 and survival is substantially greater than that 

 available for growth alone. 



The environmental data being collected in this 



study may eventually facilitate predictions of 

 flowering and fruit set. This is a fundamental 

 requirement in formulating ecological control 

 measures. Blaisdell (2) has shown how growth 

 and yiel'd of sagebrush vegetation can be related 

 to precipitation and temperature. In the present 

 study, the effects of temperature (if any) were 

 masked by the response to precipitation (figure 

 4). Wetherell (34-) suggested that increases in 

 leaf growth of brigalow (Acacia harpophylla) 

 in spring require higher air temperatures than 

 in the autumn because of the influence of soil 

 temperatures. The slower response of E. gilesii 

 to September rainfall may be due partly to lower 

 soil temperatures prevailing at that time in com- 

 parison with those following equivalent rains in 

 March. 



Fruit density on the ground and field germi- 

 nation are shown in table 2. The results suggest 

 that the number of fruits germinating is only a 

 small proportion of the total. Only two germina- 

 tion events (March and September) occurred 

 from November 1969 to November 1970, and seed- 

 ling survival from both was negligible. Fruits 



150 



120 



90 



60 



30 







30 



15 







225 



150 



75 







7 5 



50 



25 







.11 llllllll 



ili.l 



[*****J-Maximum temperature (6 dov mean) 

 ^J iit^fcL Minimum temperature <6 day mean) 



■1.J..I i 



u 



40'- 



<u 



20 2 

 o 



I 



E 



-20 H 



MAM 

 Month 



s o 



Figure 4. — Trends in numbers of buds, flowers, and fruits 

 on marked branches of Eremophila gilesii during 

 1969-70. Data obtained by combining that from height 

 classes of 22.5 to 45 cm. and >45 cm. Rainfall and 

 temperature means for the period of observation are 

 indicated. 



