YIELD TABLES 95 



a given strip, generally one or two chains wide, or on a sample plot. 

 The volume secured from accurately measuring the small sample 

 (generally from 3 to 20% or less) in this way is applied to the entire 

 tract in order to obtain the total volume. For example, if by cruising 

 a tract, the sample plot or strip shows 5000 b.f. per acre and there are 

 10,000 acres, the total volume on the tract will be 50,000,000 b.f. 

 Measurements of growth are made and applied in the same way. If 



FIG. 49. Timber cruising in a pine forest. The compassman on the left sights 

 through the instrument and the tally man on the right measures, counts and 

 tallies the trees to be recorded in his notebook. Thus a sample area is measured, 

 and from it the total number of trees, volume of the stand in board feet, etc., are 



determined. 



the growth rate is 500 b.f. per acre per year, the annual growth on 

 this tract would be 5,000,000 b.f. 



8. YIELD TABLES 



Yield tables are used to predict the contents or volume of a forest 

 at a specified future year. They are tables of the expected contents 

 per acre of a forest growing on a specified site and managed in ac- 

 cordance with the most efficient methods. They may be based on 

 three or more site qualities, and they may be applicable for pure or 

 mixed, virgin or second growth, thinned or unthinned forests. Yield 

 tables should be used only in the region where they have been con- 

 structed. Two kinds of tables are generally recognized, namely, the 

 empirical and the normal tables. The normal table shows the yield 

 for fully stocked stands, whereas empirical tables show the average 



