THE FORM OF STANDS. EVEN-AGED \^RSUS MANY-AGED 389 



The result of these two factors is that the area of an age class is at first 

 small, its growth retarded and mortality heavy, but with advancing 

 age, the area or per cent of total area occupied by this class increases 

 until it reaches a maximum at a period when the stand is at maturity 

 and before the loss of veterans begins to leave holes in the canopy. 



TABLE LXI 



Average Crown Spread of Loblolly Pine in the Forest, at Vredexburgh, 



Ala. 



This law of expansion is illustrated in Fig. 82. 



4 Acres 



I I Area occupied by Crowoa 

 ^^ Area not occupied by Crowna 



Even-aged 

 stand. 



Single age-class in 

 Many-aged forest. 



Fig. 82. — Possible expansion of area occupied by crowns of trees of a given age 

 class in a many-aged forest, contrasted with limited expansion possible in 

 crown area in an even-aged stand. Loblolly Pine, Ala. Dotted lines show 

 possible expansion of 7 per cent in even-aged stand. Shaded area shows pos- 

 sible expansion of stand of 332 per cent in many-aged forest. 



On the left, in Fig. 82 an even-aged stand occupies a square area of 4 acres, 417 

 feet square. During its growth, cro^^Ti expansion is effected by a reduction in the 

 number of trees from 140 at 40 years, to 59 at 80 years, with much more rapid reduc- 

 tion i^revious to 40 years. The only expansion of area possible for the age cla.ss is 

 around the edges of the square. The trees can extend their crowns an average of 

 14 feet, or 7 feet on one side, in the 50-j'ear period (27-13 feet). This gives a final 

 area in square feet of 43 1^ or an expansion of 7 per cent. 



