RATE OF INCREASE IN TIMBER. 163 



pushed rapidly upward until about its fiftieth year. It 

 was then set free by fire, which checked its upward growth 

 for about twenty-five years, when, owing to the crowding 

 of surrounding trees, it began to again increase rapidly 

 in height. When eighty-four years old fire killed the 

 surrounding trees and set this one entirely free, in which 

 condition it remained until it was cut eighteen years 

 later. When cut it measured fifty-five feet high, thirteen 

 inches through at the base, and contained 29.95 cubic 

 feet of timber. During the last ten years it had made 

 an average annual increase of 1.5 cubic feet. 



This study brought out the following facts: 1. While 

 rapid upward growth is being made the lateral accretions 

 are slight. 2. Large accretions accompany full leafage. 

 3. After the surrounding growth is killed, the troe be- 

 gins to strengthen the portion which receives the greatest 

 strain by wind, that is, the lower part of the trunk. 4. In 

 approaching the top of the tree the accretions are found 

 to diminish as each live branch is passed. 



Fig. 59 shows a section of a White Pine that was entirely 

 open grown. This tree was cut when fifty-six years old, 

 and measured eighteen inches in diameter on the stump, 

 eight inches at twenty-five feet above the stump, and 

 forty-eight feet in height. The volume of the stem when 

 cut was 28.85 cubic feet; the accretion during the last 

 ten years was 12.52 feet, which is equivalent to mean 

 annual increment of 1.25 feet. 



As the live branches of this tree occupied the whole 

 trunk, the timber was very knotty. A proper crowding 

 would have kept it from forming large branches on the 

 lower trunk, stimulated its upward growth, and pre- 

 vented so large an increment during the early life of the 

 tree. But if, as with the former tree, it had been first 

 crowded and then set free, the best timber in the least 

 time would have been secured. 



