58 BULLETIN" 544, U. S. DEPARTMENT OF AGRICULTURE. 



found in a fully stocked unthinned stand of 95 years. The means 

 this thinning would afford for the enlargement of the crowns of the 

 remaining trees should make it possible to sustain such a rate of 

 growth for the 40-year period as would bring the thinned stand at 

 105 years to a state of development equal to the un thinned 120- 

 year-old stand. This would require a periodic mean annual growth 

 of but 350 board feet, which should be easily possible, since in the 

 un thinned stands it is 500 board feet per annum for the period from 

 the seventieth to the seventy-fifth years and 360 board feet per 

 annum from the eightieth to the eighty-fifth, with a mean for the 

 40-year period of 280 board feet per annum. 



The final thinning in the one hundred and fifth year would be 

 increased in severity so as to take out 1 tree in every 4 in the dominant 

 and intermediate crown classes, thus reducing the number of trees 

 remaining in these classes to 347 and the volume to 23,300 board feet 

 in round numbers. 



The calculation of the final yield is based on the assumption that 

 the volume will increase at the same rate per cent in the final 15 years 

 in the thinned stand as in the unthinned stand. This gives an average 

 volume for the 347 trees of 74 board feet per tree, corresponding to a 

 tree 9.5 inches in diameter at breast height and 65 feet tall, which is 

 well within the limits of reason. 



These calculations, like those on cord yields, leave out of consid- 

 eration entirely all intermediate or final yields to be obtained in 

 cutting suppressed and dead trees, which in the aggregate would be 

 considerable, thus making the predictions amply conservative. 



Doubtless on the rotations after the first one, except in exposed 

 situations, the final removal of the crop might be begun in the ninety- 

 fifth or one hundredth year under the shelter-wood compartment 

 method. This would render the two cutting areas suggested in the 

 original plan independent of one another, so far as seeding was con- 

 cerned; would eliminate the intermediate hardwood crop, and would 

 enable the rotation to be materially shortened. In such a case it 

 might be well to introduce another thinning about the eighty-fifth 

 year. A too-intensive system of management, however, for the pro- 

 duction of first quality spruce sawlogs will not be justified. Com- 

 petition with white pine similarly managed would make such an 

 undertaking entirely unprofitable. 



Figure 3, based on actual measurements in old-field spruce stands, 

 shows graphically the influence the number of trees per acre has upon 

 the development of the stand, particularly on average breast-high 

 diameter and yield. 



Overcrowding in plot 39 is particularly apparent from the under- 

 development of breast-high diameter and of board-foot contents. 

 In contrast with this is the understocking in plot 17, which gave rise 



