LOBLOLLY OK NORTH CAROLINA PINE. 43 



shade is acquired after the pole stage, and the most crowded trees in 

 the intermediate crown class die rapidly after the thirty-fifth year. 

 Young suppressed trees left in lumbering recover very slowly on me- 

 dium sites, if the trees have passed the pole stage, and the crowding 

 was of long duration. In fifty-two measurements made on 50-year-old 

 suppressed trees which were growing on well-drained upland clay soils 

 in the Piedmont, and which were left after lumbering seven years before, 

 only nine showed any marked increase in the width of the last seven 

 rings, as compared with the width of the preceding seven rings. They 

 were selected as being typical suppressed trees, which were too small 

 for saw logs at the time of the first cutting. The height growth of 

 these same trees during the last seven years was only 22 inches, while 

 that of the other trees which showed no signs of suppression was 39 

 inches during the same period. The revival of large overshaded trees, 

 even if only moderately suppressed and growing on the drier soils, is 

 slow or does not take place at all. The stem analyses fail to show that 

 any large number of trees on such sites ever passed through any period 

 of great or prolonged suppression, but rather that large old trees which 

 were growing on drier quality sites invariably made good growth in 

 their youth or that the period of suppression was short. On the other 

 hand, the diameter growth of trees, which have not been subject to exces- 

 sive overshading, is greatly accelerated when given growing space. This 

 makes thinning by removing the smaller and crowded trees desirable, 

 whenever it can be done without extra cost. Beneath a crown cover 

 where about one-half of the light is excluded, young trees on the best 

 sites will grow healthily till the high pole stage, though both the 

 diameter and height growth are lessened, the diameter growth to a 

 larger extent than the height growth ; on the removal of the shade both 

 make rapid response to the increased light. (Plate XIV.) 



The trees exhibit with age a progressive increase in their demands 

 upon light. About the period when the rate of height growth becomes 

 lessened, the crown spreads rapidly, tending to become round and flat- 

 topped, and the branches nearly horizontal. At the beginning of this 

 stage there is a rapid decrease in the number of trees to the acre, from 

 the dying off of the weaker crowded trees. The decrease in number of 

 trees may be as great as 35 to 40 per cent in 10 years. (Table 42.) 

 Eventually, except on the very best sites, each tree stands isolated with a 

 band of light between it and its nearest neighbors. (Plate XXV.) On 

 the poorer sites, especially on the drier soils, this isolation takes place at 

 an earlier age than on good sites. Table 2 shows the small number of 

 trees in the suppressed and intermediate crown classes. On the very 

 best sites groups 120 to 130 years old can be found with almost unbroken 

 cover. As the crowns become isolated under these conditions, young 

 pines appear, while gallberry and similar shrubs always form an abund- 

 ant ground cover. In the old-field groves on good sites, the period of 

 isolation begins rather late, after the fiftieth year ; while on poor sites it 

 begins at the thirtieth or fortieth year. On the slow-draining savanna 

 land it also begins early and young trees less than 40 years old are very 

 intolerant of shade. 



