8 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. 



of these dead branches will, of course, persist for years, but they will 

 not be large enough to detract from the value of the timber for the 

 purposes to which it is best suited. Even this moderate density would 

 be undesirable, however, if the stand could not be thinned fairly 

 early in its life — when from 40 to 60 years old. Trees which have 

 come up in openings in stands grow more slowly than trees which 

 start in full sunlight, but, on the other hand, develop small side 

 branches on the lower stem and in the end produce better timber. 



In a typical dense stand of merchantable lodgepoles there is usu- 

 ally a large number of suppressed trees from 2 to 6 inches in diam- 

 eter. These are not younger than the larger trees in the stand, as 

 might be supposed, but are generally of about the same age. 



There is a general belief that lodgepole will not recover from 

 suppression when openings are made in the stand. Recent investiga- 

 tions, however, prove that recovery does take place and often to 

 a remarkable degree. The photograph of the cross section of lodge- 

 pole pine (PI. II) shows the effect of a very heavy thinning in 

 which the stand was well opened. This particular cross section was 

 selected for photographing because the rings formed previous to the 

 release are large enough to show, which is not the case in many 

 badly suppressed trees. 



Another tree studied was released from suppression 16 years ago, 

 when 94 years old. Since then its diameter has increased from 

 1.44 inches to 5.06 inches and its height from 15 feet to 25 feet. The 

 rate of growth has increased from 1 inch in diameter in 67 years to 

 an inch in 4 years and from 1 foot in height in 7 years to 1 foot in 

 1.6 years. After its neighbors were removed the rate of diameter 

 growth increased immediately, but for the first 8 years it grew in 

 height only at the rate of 1 foot in 4 years. During the last 8 years, 

 however, it has been growing in height uniformly at the rate of a foot 

 a year. The rate of volume growth has increased 4,680 per cent. 



Another tree which, at the age of 50 years, had a stump diameter - 

 of nine-tenths of an inch and a height of 5 feet, was opened to the 

 light by a cutting made 43 years ago. After 43 years of sunlight 

 the tree had grown to a diameter of 6.6 inches and a height of 27 feet. 

 The volume of wood produced in the period of accelerated growth 

 was about 25,600 per cent more than that produced during the period 

 of suppression. 



Even small seedlings which have been badly suppressed will re- 

 spond vigorously when the stand is well opened. A seedling about 

 30 years old, three-tenths of an inch in diameter at the ground, and 

 2-| feet high, grew to a diameter of seven-tenths of an inch and a 

 height of 6 feet in 5 years after its release. 



Whether or not a tree will recover from suppression depends upon 

 the condition of its crown at the time of release, the amount of light 



