732 Forestry Quarterly 



4. To measure as accurately as possible the carrying capacity of 

 a known representative area. 



The results of the first three of the above studies have already 

 appeared in Bulletins 67, 117 and 177 of the Bureau of Plant 

 Industry, and this publication, therefore, deals only with the last 

 query, although the results of the other three studies are sum- 

 marized in this volimie. 



The method followed in the capacity study was : 



1. To cut everything growing on small areas (quadrats), and 

 from the weights of the dry material collected to calculate the total 

 productivity in terms of pounds of forage per acre. These were 

 collected for a period of 9 years, from which a figure of 1160 pounds 

 per acre was obtained as the approximate value of the average 

 total annual productivity. 



This method was supplemented by data from hay cuttings on 

 an area of 4923^^ acres, which gave an average amount of hay per 

 acre of 640 pounds. 



The results are summarized as follows: 



A map was prepared showing the approximate distribution of 

 the different forage plant associations of the area. Four main 

 plant associations are found, the six- weeks grass, the black grama, 

 the crowfoot grama, and the needlegrass associations. "From the 

 quadrat measurements the approximate productivity of each 

 association is obtained. From these figures and the areas of each 

 association, a weighted average expression representing the average 

 productivity of the whole Reserve is derived. This number, 1100 

 pounds per acre, is closely comparable with that obtained as the 

 average of the quadrat measurements alone (1160 pounds). 

 Assuming the value of 1100 pounds per acre as an average total 

 productivity and 50 per cent of that amount as maintenance 

 capacity for the range, then, if the average animal eats the equiva- 

 lent of 30 pounds of dry feed per day he will need 11,000 pounds 

 in a year, and it will take 10 acres of land to furnish that amoimt 

 at full productivity, and will take 20 acres of land at maintenance 

 capacity. Thus we have an average value for carrying capacity 

 equal to 20 acres per head per year, or 32 head per section" 

 (640 acres). 



The above figures are of interest, since they show a much higher 

 carrying capacity for this fenced area of semi-desert range than is 

 figured on the average unfenced National Forest range having 



