19 



TABLE IV. NORMAL YIELD IN CUBIC FEET AND 



CORDS OF INFERIOR SECOND GROWTH HARDWOOD 



STANDS IN CENTRAL NEW ENGLAND 



(All trees 2 inches and over in diameter) 



this type, is given. The construction of the table is similar to 

 that of Table II. 



Number of Trees per Acre. The gradual increase in the 

 number of trees per acre between the ages of seventeen and 

 twenty-three years is due to the fact that many trees are 

 growing into the lower diameter limit of the table during this 

 period exactly the same effect as that produced by a high 

 diameter limit in the case of Table III. After thirty years 

 gray birch rapidly deteriorates, the rate of reduction in vol- 

 ume of the stand being dependent upon the percentage of this 

 element in its composition. Cord volume falls off while cubic 

 foot volume maintains a slight increase because more cubic 

 feet of solid wood are required to make a cord as average 

 diameters of trees become greater. The continuance of rise 

 in volume after the culmination of basal area is due to the 



