SOUTH CAROLINA FOREST RESOURCES AND INDUSTRIES 



Forest Growth And Commodity Drain 



THE forest products industries are an important 

 part of the economic structure of South Caro- 

 lina. The timber resources on which they de- 

 pend have been estimated in the section on timber 

 volume. These resources may be considered as 

 quantities immediately available for utilization or as 

 growing, interest-bearing capital that without de- 

 struction can yield a constant annual profit. How- 

 ever, unless the net growth exceeds the average drain 

 on the forest, the wood-using industries of the State 

 must inevitably decline for lack of ^aw material. 

 The following sections are an attempt to evaluate 

 the net forest growth and drain upon the timber 

 stands of South Carolina, as of 1936 and during the 

 5-year period 1936-40. 



Forest Growth 



Growth was calculated in two ways — for sawlog 

 material in board feet and for all sound material in 

 trees 5 inches d. b. h. and over, in cubic feet. Board- 

 foot growth includes the increment in all saw-timber 

 trees and the volume in sound trees reaching the 

 minimum saw-timber diameters (9 inches d. b. h. 

 for pines and 13 inches d. b. h. for hardwoods) during 

 the year. Cubic-foot growth includes the incre- 

 ment in all sound trees 5 inches d. b. h. and larger, 

 and those reaching 5 inches d. b. h. during the year. 

 Cull trees and the tops of hardwoods and cypress 

 were excluded from the calculations. 



Forest growth may be expressed as gross and net, 

 the difference being the loss incurred through mor- 

 tality of sound trees. Mortality, as defined here, 

 includes death from any cause except cutting for in- 

 dustrial use or to improve the stand. Fire, insects, 

 disease, wind, old age, and tree competition are the 

 principal causes of mortality. Fire is the chief man- 

 made and avoidable cause of forest mortality (fig. 

 42), particularly in the reproduction and under-saw- 

 log-size classes. Among the larger trees, insects and 



Figure 42. — Effects of fire on cypress and pine. Fire is the most 

 destructive of all the agencies that cause mortality and reduce the 

 growth rate of South Carolina forests. 



disease destroy much timber, though these losses 

 are usually inconspicuous because they are dispersed 

 among healthy stands. 



Growth and mortality in the South Carolina for- 

 ests in 1936 are estimated in figure 43, and for the 

 5-year period 1936-40 in table 23. Net growth for 

 the State in 1936, by condition classes, is indicated 

 in table 24, and for the three survey units in Appen- 

 dix table 35. 



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