428 THE USE OF YIELD TABLES 



under sustained management and thinnings may be roughly approxi- 

 mated by measurements taken on natural stands not under management, 

 by the method just discussed, of computing the number of trees per acre 

 for given diameters. The rate of diameter growth should be that of 

 trees now dominant in the stand. This gives the age of the diameter 

 classes. The approximate amount of material yielded by thinnings in 

 such a forest may also be roughly predicted by noting the number of 

 trees which drop out of the stand at each decade, and computing their 

 average diameter and volume. 



By establishing permanent plots, re-measured at intervals of 5 

 or 10 years, and properly thinned, data will finally become available 

 showing not merely the yield of stands grown under management, at 

 final cutting, but the total yield including thinnings. The absence 

 of such stands precludes the construction of yield tables on this basis 

 at present and justifies efforts to predict such yields by means of crown 

 spread and number of trees per acre in normal stands. The nearest 

 approach to such yield tables is found in tables constructed from second- 

 growth stands, or plantations, but it is seldom that these stands have 

 been repeatedly and properly thinned, hence the yields shown merely 

 indicate a normal possibility for fully stocked, wild stands. 



References 



The Measurement of Increment on All-aged Stands, H. H. Chapman, Proc. Soc. 



Am. Foresters, Vol. IX, 1914, p. 189. 

 Yield Table Methods of Arizona and New Mexico, T. S. Woolsey, Jr., Proc. Soc. Am. 



Foresters, Vol. IX, 1914, p. 207. 

 Yield in Uneven-aged Stands, Barrington Moore, Proc. Soc. Am. Foresters, Vol. 



IX, 1914, p, 216. 



