THE FORAGE ACRE AND HOW IT IS DERIVED 325 



lands originally listed as incapable of the highest possible utili- 

 zation. 



The Forage Acre and How it is Derived. — " Forage acre " is 

 the term used in designating the grazing value of a given type. 

 A forage acre may be defined as an acre area having a complete 

 (ten-tenths) cover of palatable vegetation or the equivalent 

 thereof in density and palatabiHty.^ Probably the best under- 

 standing of the term may be had by considering briefly how the 

 forage acre is derived from the reconnaissance data. 



In computing the number of forage acres contained in a given 

 range type the total acreage of the land area is multiplied by the 

 surface (expressed in tenths of the whole) which actually sup- 

 ports vegetation. This figure, in turn, is multiplied by the den- 

 sity of the cover and the percentage of palatable vegetation. 

 Thus we have the formula : Total land area X Surface supporting 

 vegetation X Density of cover X Percentage of palatable forage = 

 Forage acre. For example, let us assume that the type consists 

 of 80 acres (total land area) and that the surface or vegetation 

 cover is y\. Let us say that the vegetation of this y\ surface 

 cover has a density of y\, and that 80 per cent of the cover is 

 palatable to stock. By multiplying the factors mentioned above, 

 namely, the total acreage of the type, by the surface acres which 

 support vegetation, then by the density of the vegetation on the 

 area, and finally by the percentage of the vegetation which is 

 palatable to stock, we have a figure, namely, 36, or the number 

 of forage acres in the type. 



With such known factors as the number of forage acres con- 

 tained in each type, their accessibility to stock, the time in the 

 season when the herbage should be cropped, and certain other 

 facts, it is possible to determine with reasonable accuracy the 

 number of stock that the range will safely supply during a normal 

 grazing season or any part thereof. 



1 The vegetation cover refers only to the surface area which is occupied by vege- 

 tation. On an area where the cover is not complete the density of the vegetation 

 is shown by applying the surface-cover factor in tenths, 10/10 being a complete 

 cover. The estimate of density is determined by the comparison of the type under 

 consideration with a similar type having a 10/10 density. 



