CHAPTER XXXI 



METHODS OF MEASURING AND PREDICTING THE 

 CURRENT OR PERIODIC GROWTH OF STANDS 



335. Use of Yield Tables in Prediction of Current Growth. The 

 current growth of stands for short periods can always be predicted 

 with greater accuracy than for long periods. Not only can the present 

 condition of the stand be gaged, as to species, numbers, crown density, 

 form, thrift and rate of growth in immediate past, and this information 

 applied in predicting the rate at which growth will continue, but the 

 inevitable changes, some of them unforeseen, which will occur in the 

 future to modify this rate of growth, take place at a rate which bears 

 a close relation to the length of the period of prediction. 



Only when the net results of all the various factors which produce 

 yields have been measured on stands after they have passed through 

 the period is an approximate degree of accuracy obtained for long periods, 

 hence the use of yield tables based on age. It follows that for the pre- 

 diction of current growth for short periods on existing stands, the net 

 current growth shown by the above yield tables, reduced on the basis 

 of age and relative density to apply to the stand in question, is the 

 best basis of growth prediction even for these short periods. 



336. Method of Prediction Based on Growth of Trees, with Cor- 

 rections for Losses. In endeavoring to use these yield tables for 

 stands which differ greatly from the normal in number of trees per acre, 

 density of crown cover, form or distribution of age classes, and com- 

 position of species, it is often difficult to find or make a table which will 

 apply to the stand even when corrected for density. In such cases, 

 a direct measurement of the stand may be resorted to instead of a com- 

 parison with a standard yield. The growth of any stand of whatever 

 character, for the next decade, will be the sum of the growth in volume 

 of the trees which survive till the end of this period minus the loss of 

 the total volume of the trees which do not survive (§ 252). The elements 

 which give stability to this method are a knowledge of the exact pres- 

 ent number and diameter of the trees in the stand, which may be 

 supplemented by a classification of crowns to indicate those now domi- 

 nant, intermediate or already suppressed, and by a tabulation of past 

 growth in diameter, by diameter classes (§278). The elements of 



