LOBLOLLY OR NORTH CAROLINA PINE. 63 



GROWTH IN DIAMETER. 



Table 16 shows the average growth in diameter at breast height of all 

 trees (0 inches and over), the diameter growth of dominant trees in 

 fully stocked unthinned stands, the diameter growth of dominant trees 

 in open .-lands, and the number of years required to grow one inch in 

 diameter. 



All the diameter measurements of standing trees, unless otherwise 

 stated, were taken at a uniform height of 4 feet 6 inches from the 

 ground called "breastheight." Breasthigh measurements made outside 

 cf the bark are a better guide for determining the growth in diameter 

 than stump measurements, as in this way the variations due to the 

 height of the stump and butt swellings are eliminated. 



It is often desirable to convert diameter at stump height inside of 

 bark to diameter at breastheight outside of bark. This relation is 

 shown in Table 17. It can be used in obtaining the breasthigh diameter 

 from stumps on cut-over land. (Also, see Table 8.) 



The culmination of the diameter growth often takes place as early 

 as during the first decade and seldom later than in the fourth decade. 



Table 18 shows the diameter growth on stumps by decades for typical 

 groups on different sites. Column 1 shows the diameter growth of a 

 crowded group of loblolly pines mixed with hardwoods on moist stiff 

 clay soil. The growth in diameter does not culminate until between 

 the thirtieth and fortieth years; the growth is so persistent that at the 

 age of 130 years it amounts to nearly 1.5 inches for the decade. The 

 rate of diameter growth, however, is much less than that -of the open 

 stand given in column 2, which shows a group of trees on loose loamy 

 soil on the edge of a pond, near Howard, Bertie County. It is an 

 excellent example of persistent and rapid diameter growth, the increase 

 between the eightieth and ninetieth years amounting to nearly 1.8 

 inches on the stump. Similar, if not better, results can probably be 

 obtained from all stands of Quality I, provided they are properly 

 thinned. (Plate IX, B.) 



