PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



173 



Figuee 6. — Aerial view of sheep tracks converging on watering troughs at Caroonboon, 62 km. N.N.W. of Deniliquin. 

 N.S.W. Vehicle wheel tracks also appear in the photograph. The area of the photograph is 141 by 203 m. The 

 vegetation changes from annual barley grass (Hordeum leporinum) within the 63 m. radius of the trough to the 

 right hand side of the fence, through a zone of barley grass and annual saltbush (Atriplex pseudocampanulata 

 Aellen) within the 123 m. radius, with perennial bladder saltbush (Atriplex vesicaria) and annual saltbush 

 (Atriplex lindleyi Moq.) dominating beyond that. 



response in the five poor to average rainfall 

 years preceding the exceptional year. Also, while 

 the most rapid recycling appears to occur by uri- 

 nation, this can contribute to losses in excess of 

 50 percent of nitrogen by volatilization from bare 

 soil surfaces under summer conditions (67). 

 Further, the rate of decomposition of sheep feces, 

 which are strongly water-shedding once dry, is 

 very slow in a semiarid environment (50) , slower 

 than the rate which can be inferred for the litter 

 of many perennial and annual dryland species 

 from its comparative lack of accumulation from 

 year to year. These findings indicate only a lim- 



ited beneficial role for the effect of stock on the 

 recycling of plant nutrients in arid and semiarid 

 rangelands by increased mineralization rates. 



Concentration Of Nutrients 



Concentration of plant nutrients occurs on a 

 small scale with the localized deposition of indi- 

 vidual urine patches and feces, and on a larger 

 scale due to aggregation behavior in camping or 

 in water seeking. Examples are provided by 

 Hilder (26) of the effects of camping behavior 

 on the redistribution of nutrients for sown pas- 

 ture in the summer rainfall, northern Table- 



