60 LOBLOLLY OR XORTH CAROLINA PIXE. 



Table 14 gives the height of trees in fully stocked stands for differ- 

 ent diameters on different site classes. 



On best sites in pure stands height growth reaches its maximum 

 rate between the seventh and fifteenth years. Dominant trees in such 

 groups during this period will often make a growth of four feet a year 

 for several years, while the average rate of height growth during this 

 period on all sites of the first quality is nearly three and one-half feet 

 a year. During the second decade the growth averages three feet 

 a year. On poorer sites the rate of height growth culminates later. On 

 sites of Quality III, culmination does not take place until between 

 the eighteenth and thirtieth years. 



Single trees and small groups of trees growing among hardwoods on 

 stiff clay soils attain the maximum rate of growth very late, between 

 the thirtieth and fortieth years, and the same is true of some groups 

 growing on the most unfavorable sites (Table 14, columns 1 and 6). 

 The growth on old fields on the uplands is rapid at first but decreases 

 after the fortieth year; such old field stands, therefore, if old, have an 

 average rate of growth characteristic of slow growing stands. This 

 is well illustrated by the growth of loblolly pine on cultivated soil on a 

 very sandy, well drained knoll in the midst of a longleaf pine forest 

 f Table 14, column 4). Thus, the average annual growth in height 

 during the first decade was 2.1 feet, during the second decade 2.7 feet, 

 the third decade 2.4 feet, the fourth decade 1.0 feet, and the fifth decade 

 .3 feet. 



The growth on very wet sites, as may be seen from the growth of the 

 loblolly pine in mixture with cypress and black gum of the same age, 

 is slow. (Table 14, column 6.) The pine, however, had slightly out- 

 grown in height the black gum and the cypress. The soil is a loamy 

 sand, covered with one or two feet of flowing water during most of the 

 winter and spring and often for a few days at a time during the growing 

 season. 



The growth of the pine on the best alluvial soil in even-aged groups 

 where the competition for the light is keen is very rapid (Table 14, 

 column 2). 



The growth given in Table 14 is the average growth of suppressed, in- 

 termediate and dominant trees. Single dominant trees therefore have a 

 much better growth, while intermediate and suppressed trees have a 

 much slower growth than that of the average tree. 



Table 15 gives the relation of diameter to height, the merchantable 

 length of trees of different diameters on different quality sites, and the 

 per cent of merchantable length to total height. Top diameters of mer- 

 chantable length are given in Tables 24 to 31. 



