SILVICULTURAL NOTES. 



31 



increase begins to fall off. The merchantable contents of Shortleaf 

 Pine under 80 years of age is somewhat uncertain, as the diameters 

 become too small for accurate calculations. Between the ages of 60 

 and 100 years the average yearly increase in merchantable contents 

 amounts to 6.25 board feet, and between 60 and 200 years to 7.71 

 board feet. (See fig. 7.) 



Relation between diameter, total height, merchantable length,* crown 

 length, and clear length* (See fig. 8.) — The principal point of inter- 

 est connected with this diagram is the rapid increase in the length of 

 merchantable timber obtained from trees of 15 to 24 or 25 inches in 

 diameter, and the small additional length obtained from trees of greater 



'0 10 B0 30 40 50 



Fig. 6.— Diagram showing the height growth of Shortleaf and Loblolly Pine on the basis of age. 



60 70 80 SO 100 110 ISO 130 140 150 

 AGE- YEARS 



diameters. The merchantable length is greatest in proportion to the 

 total height when the tree has a diameter of 20 inches. In this case 

 a little more than one-half of the total height is merchantable. 



By comparing the curves for clear length and for merchantable 

 length it will be seen that for trees below L9 inches in diameter the 

 merchantable length is less than the clear length, while above that 

 diameter the reverse is true. In other words, in trees over 1!> inches 

 in diameter breasthigh (21 inches on the stump) the logs are cut up 

 into the crowns, the distance to which the cut extends into the crown 

 increasing as the diameter of the tree increases. 



Merchantable length is the total length « > l" merchantal>l<' liml >«-r; in other words, 

 the sum of the log lengths. 



'"Clear length is the' distance from the ground to the point where the branches of 

 the crown begin. 



