THE ART OF THE SECOND GROWTH 



tlie same age, the poorer these factors are. For example — Yellow 

 Pine Forests: 



Number of trees per acre. 



Soil. Boles 75' long. Diameter 12". AgeGOyis. 



I quality . . . 320 240 380 



II quality... 240 215 4G0 



HI quality... 190 . 190 540 



During the pole stage and tree stage, shade bearers exhibit per 

 acre of ground about 50% more trees than light demanders. 



The following curve illustrates the interdependence between age 

 and number of trees 'ler acre: 



10,000 



5,000 



imber 2,500 



1,000 



of 900 



800 



700 



600 



500 ' , . 



400 



300 * » ^ 



200 ***•-.. 



100 " ' 



When the forest is 



10 20 30 40 50 (30 70 80 90 100 120 130 140 150 160 17 

 years old. 



III. Growing space of a tree. 



In their earliest youth all species stand or eve« desire a dense 

 cover overhead. When the food supply stored in the seed shell is 

 consumed, however, the seedling requires light to digest its food. 

 With increasing age, the tree boles getting longer, the crowns rub 

 and beat one another intensely, oscillating in the wind. As a con- 

 sequence each crown is surrounded with an air space, the relative 

 width of which depends largely on the length and the flexibility of 

 the bole. It might be stated that the growing space of a tree is a 

 function of the square of the gradually lengthening bole. 



Trees differ in the ease with which warring neighbors lose their 

 buds and shoots. Oak, for example, loses its May shoots easily, 

 whilst Beech, struggling with Oak. loses but a few leaves along its 



33 



