sample of plots. A total of 4,391 sample trees 3.0 inches 
and larger in diameter were bored. Radial growth rates 
of these trees were then compared with the radial 
growth rates of 22,311 sample trees obtained on the 
original survey. It was found that growth rates, for 
species of comparable size in similar stands, were the 
same; therefore, all 26,702 sample trees were used. In 
general, computational procedures consisted of adding 
the volume of small trees that grew to merchantable 
size or grew into a higher diameter class group during 
the period to the growth of the trees that remained in 
a particular diameter class. Sample tree diameters were 
increased by using the measured diameter growth of 
trees of the same diameter class. For instance, the 
average diameter growth of 8-inch trees was based 
upon the growth of trees which were 8 inches in 
diameter at the start of the growth period, not the 
last 10 years’ growth of an 8-inch tree. Bark growth 
was allowed for. The differences between present and 
projected volume of the sample tree was then expressed 
as an annual percentage increase through the use of 
compound-interest tables and these percents were applied 
directly to the inventory volume. Mortality was obtained 
by special studies on the ground plots, and the total 
annual loss was deducted from total growth. 
Drain Estimates 
Estimates of commodity drain were made by obtaining 
the amount of wood produced as primary forest products 
from all the primary wood-using industries. Sawlog 
production was obtained from a 100-percent field canvass 
of the sawmills by the Bureau of the Census. Produc- 
tion of pulpwood, veneer logs, poles, piling, and other 
products was obtained by a field survey of the plants 
using these products. A special survey based upon area 
segments of the Master Sample of the Bureau of 
Agricultural Economics and the Bureau of the Census 
was used to obtain fuel-wood and fence-post production. 
All production figures were converted to drain in terms 
of inventory volume, using over- and under-utilization 
factors developed from a stratified sample of woods 
utilization practices. Drain estimates were prepared for 
each county. Detailed statistics by counties are given in 
Forest Survey Release 26 (5). 
The principal sources of error in drain estimates, 
aside from mistakes in computing, are (1) reporting 
errors, (2) canvassing errors, and (3) sampling errors. 
Reporting errors stem from the failure of small manu- 
facturers or wood producers to keep accurate records, 
and no measure of the extent of error introduced from 
this cause is available. Canvassing errors are failures to 
obtain reports from all the wood producers. These were 
held at a minimum through the use of trained enumer- 
ators and check surveys. Sampling errors are the only 
measurable errors involved. They ranged from + 1.8 
percent for sawlogs to + 11.4 percent for fence posts. 
The sampling error for total cubic-foot drain in the 
State was + 1.9 percent. 
Public Landownershi Pp 
Information on the forest area and timber volume in 
Federal, State, county, and municipal ownership was 
obtained in the following manner. The area under 
Federal jurisdiction was obtained from supervising 
agencies. The South Carolina State Commission of 
Forestry provided the figures for State forests and parks. 
County and municipal ownerships were obtained at each 
county courthouse from appropriate officials. The bound- 
aries of all of these tracts, except the Sumter National 
Forest, were outlined on the aerial contact prints, and 
dot counts were made to determine the acreage of forest 
and nonforest land. Because of the scattered holdings 
in the Sumter National Forest, the boundary line drawn 
represented only a close approximation of the outside 
boundary. Dot counts made within this generalized area 
were then applied to the total area of the Forest. Forest 
plots were classified by forest type and stand class in 
each publicly owned area, thus giving the area by these 
classifications. Average volumes per acre by type and 
stand-size class, derived from survey unit summaries, 
were then applied to obtain volumes. 
DEFINITIONS OF TERMS USED 
Land Use Classes 
Forest — Land bearing forest growth, land from 
which the forest has been removed and which shows no 
evidence of any other recent land use, or former agri- 
cultural land which now has a 5-percent stocking of 
trees. Subdivided into the following classes: 
Commercial — Land bearing, or capable of bearing, 
timber of commercial character and available now or 
prospectively for commercial use. 
Withdrawn — Forest land in public ownership 
upon which commercial timber cutting is prohibited. 
Nonproductive — Forest land of such low produc- 
tivity or so inaccessible that commercial timber will 
not be produced. 
Nonrorest — Land less than 5 percent stocked with 
trees and showing evidence of nonforest use: 
60 Forest Resource Report No. 3, U. S. Department of Agriculture 
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