NORTH CAROLINA FOREST RESOURCES AND INDUSTRIES 



Forest Increment and Commodity Drain 



4»- 



CLEARLY the forest-prcducts industries constitute 

 a valuable part of the economic structure of North 

 Carolina. The forest resource upon which they 

 depend is extensive, but unless the net increment equals 

 or exceeds the average drain upon the lorest, the industries 

 must eventually decline for lack ol raw material. The 

 following is an attempt to evaluate the net increment 

 and commodity drain as of 1938. 



Forest Increment 



Diameter Growth 



Diameter growth of individual trees is the basis for 

 reckoning all forest increment. To obtain the maximum 

 increment per acre a proper balance must be maintained 

 between quantity of growing stock and rate of growth 

 ol single trees. 



North Carolina has a variety ol rapid-growing trees. 

 Ol the 20 species listed in table 27, northern red oak, 

 eastern white pine, yellow poplar, and loblolly pine 

 increase in diameter at the highest rate. White oak^ 

 desirable lor many purposes, grows relatively so slowly that 

 in some stands it may be more profitable to favor the 

 faster-growing northern red oak. Because of its abundance, 

 high value, merchantability, and rapid growth rate, 

 loblolly pine is the premier species of North Carolina. 

 Under good conditions it grows to minimum saw-timber 

 size in about 35 years and continues to increase in di- 

 ameter an average of 0.25 inch per year until maturity. 

 Virginia and pond pine make rapid diameter growth 

 while young, but slow down after they reach 10 inches 

 in diameter. Shortleaf is the slowest growing of the 

 native pines. 



Net Increment Per Acre 



Table 27. — Average annual diameter growth in 10 years of selected species, 

 by diameter-class groups 



Species 



Loblolly pine 



Shortleaf pine t 



Longleaf pine 



Pond pine 



Virginia pine 



White pine 



Hemlock 



"White-cedar 



C y press 



S weetgum 



Black and water tupelos 



Yellow poplar 



Northern red oak 



Southern red oak __ 



Scarlet oak 



White oak. 



Chestnut oak -- 



Red maple 



Hickory 



Ash 



Diameter class at breast height (inches) 



6-8 10-12 14-18 20-24 20+ 



Inches 

 2.20 

 1.66 

 2.38 

 2.12 

 2.14 

 2.56 

 .80 

 1.12 

 1.00 

 1.76 

 1.08 

 2.38 

 2.20 

 1.48 

 1.60 

 1.50 

 1.44 

 1.52 

 1.16 

 1.36 



Inches 

 2.32 

 1.58 

 2.10 

 1.88 

 1.74 

 2.60 

 .90 

 1.16 

 1.20 

 1.72 

 1.12 

 2.36 

 2.72 

 1.60 

 1.76 

 1.60 

 1.56 

 1.62 

 1.22 

 1.34 



iches 



Inches 



2.48 



2.30 



1.44 



1.24 



1.56 



1.18 



1.78 



1.62 



1.48 



1.60 



3.34 



2.68 



1.04 

 1.26 

 1.58 

 1.16 

 2.48 

 3. .54 

 1.52 

 1.86 

 1.62 

 1.44 

 1.70 

 1.22 

 1.42 



1.02 

 1.30 

 1.18 

 1.66 

 1.18 

 2.32 

 2.08 

 1.64 

 1.78 

 1.34 

 1.26 

 1.62 

 1.22 

 1.64 



Inches 

 1.86 



1.38 



1.68 

 1.00 

 .90 

 .78 

 1.64 

 1.14 

 2.02 

 2.38 

 1.62 

 2.04 

 1.38 

 1.08 

 1.26 

 1.28 

 2.18 



9 Reference should be made to the Growth and Drain section of 

 Definitions of Terms Used in the appendix, p. 70. 



Because of wide variations in stand classification of the 

 forest growing stock, there are marked differences in the 

 average annual net change in volume per acre, ranging 

 from an actual loss to an increase of 344 board feet (table 

 28). 



The loblolly pine type is the most productive, and the 

 net increment ot 206 board feet was the average for 4.6 

 million acres, 26 percent of the forest land. On the 1.5 

 million acres of this type in the second-growth uncut con- 

 dition the net annual increment averaged 344 board feet 

 per acre. In contrast, the upland hardwoods type, which 

 occupies nearly 4 million acres, had an average net incre- 

 ment of only 67 board feet. This is partly a result ol poor 

 sites and slow growth rates, but a more important factor 

 is the small volume of growing stock per acre, averaging 

 less than 1,500 feet for the type area. The white pine type 

 includes hemlock and the loss in volume in the old-growth 

 partly-cut stands was caused by heavy mortality of resid- 

 ual hemlock trees. This indicates that hemlock in mixed 

 stands should be cut along with the other old-growth timber 

 to avoid the losses likely to result from a disturbance in 

 site conditions. 



49 



