YIELD OF VOLUNTEER SECOND GROWTH 499 



which there was any reasonable doubt, and in calculating their growth 

 for the balance of the rotation five years were allowed for recovery 

 from the condition of partial suppression — a period found in practice 

 to be conservative. A further element of silvicultural judgment was 

 involved in arriving at the number of trees of each species to be ex- 

 pected in the final stand at sixty years. This reduction was made on 

 the ground at the time the plot was measured. Naturally, considerably 

 more trees would be left after the improvement cutting than could sur- 

 vive to maturity, even though all were individually capable of thrifty 

 growth. In the present case the number of trees left standing was arbi- 

 trarily cut down in accordance, first, with the relative crown develop- 

 ment of each group, and, second, with the number of stems to be ex- 

 pected in a fully stocked stand at sixty years, as determined from local 

 yield tables. The irregularity of crowns, inevitable in a volunteer for- 

 est, of course prevents exact uniformity in the density of the stand. 

 The figures here assumed are at least conservative for the growing 

 stock actually on the ground. The rotation was taken as sixty years ; 

 height and diameter growth were derived from model curves, based on 

 stem analyses of normal trees accumulated over several years of field- 

 work on the forest. The volumes were obtained from mill tally volume 

 tables applicable to local usage and tested with reference to actual saw- 

 mill output. The results of the computation of yield, first, for the plot 

 if left to reach maturity without treatment, and. second, after having 

 been given an improvement cutting, are shown in Table 3. 



Table 3. — Plot II — Summary of Final Yields at 60 Years 

 Final volume without improvement cutting Final volume with improvement cutting 



80 3,239 3.10 106 8,080 2.25 



' Kliminatcd a.s certain to die of disease. 



The improvement cutting thus raises the final volume of saw timber 

 on the quarter acre from 3,239 board feet to 8,080 board feet. This 

 increase is almost entirely in pine, since most of the dominant hard- 

 woods would he cut to make way for it. In addition, by removing 

 heavy crowned trees and effecting a better distrilnition of those which 



