^forest or non-forest, great care being exercised to assign 

 house lots, rivers, highways, power lines, residential areas, 

 and fields to the non-forest category. Approximately 1200 

 plots were read from the photographs for each county. 

 Forest acreage was then determined on a percentage basis 

 from the total land area of the county. It is believed that 

 forest area figures, as determined by the above method, are 

 more accurate than other existing figures for the same 

 counties, although time did not permit the making of new 

 forest determinations for all counties having aerial photo- 

 graphs. 



Method of Obtaining Timber Volume. When interpreting 

 the aerial photographs for forest acreage, all forest plots 

 were classified according to condition class, in order to im- 

 prove the accuracy of stand data derived from compara- 

 tively few field plots. Condition classes segregated the 

 more or less similar forest stands, but were not standard- 

 ized for the state. Examination of the photographs would 

 show what conditions could be reliably distinguished. One 

 set of condition classes, ' good for summer and fall photo- 

 graphy, was as follows: 1. Large trees — good density; 2. 

 Large trees — poor density; 3. Advanced reproduction or 

 sapling stands showing no individual tree crowns ; 4. Repro- 

 duction. Field plots were also separated by condition 

 classes. Average volumes and other forest data were first 

 ■compiled for each condition class; county totals were then 

 obtained through properly weighing each class by its 

 percentage of total forest area. 



Ten to fourteen aerial photographs were selected for 

 ■each sample county, the photographs being selected so as 

 to grid the county on an equally distributed pattern and 

 given representative coverage conditions found in the sam- 

 ple county. These photographs were then accurately lo- 

 cated on the county highway map. (Figure 2). At least 

 six quarter-acre sample plots were mechanically located 

 at speedometer intervals of one-half mile on each photo- 

 graph. Plot location was at five, ten or twenty-chain inter- 

 vals from the road. Plots were exactly located on the pho- 

 tograph which was frequently carried to each plot. A 

 •check could thus be kept on condition class as found on the 

 ground, as compared with office reading of the photograph. 

 Condition class, volumes, stocking, reproduction, fire oc- 

 currence, and other data were recorded while on the plot. 



Volume was determined for sawlog size and under-saw- 

 log-size material. Sawlog material may be defined as a 

 tree 9.0", or larger, d.b.h (Diameter Breast Height, i.e. 

 4% feet from average ground level) for pine, 13.0" or 

 larger d.b.h. for hardwood. The tree must be 50 per cent 

 sound or contain one sound 12' butt log. The merchantable 

 sawlog top is 5.5". The volume is expressed in board feet. 

 In some cases sawlogs are being cut from pines under 9" 

 and from hardwoods under 13", but it is not felt that the 

 standard should be lowered. 



Under-sawlog-size material is 5.0" to 8.9" d.b.h., and a 

 4.0" top for pine, 5.0 to 12.9" d.b.h. and 4.0" top for hard- 

 wood. The tree must be 75 per cent sound and reasonably 

 straight. The volume is expressed in standard cords. 



North Carolina has more than its share of cull trees — 

 trees of sawlog or under-sawlog size which fail to meet 

 specifications for those classes. Unfortunately, industries 

 are not making use of them, so there is little demand for 

 information as to their volumes, location, and other fea- 

 tures. There was not time, considering their minor im- 



portance, to sound out cull trees and determine accurately 

 the sound wood in them. The better culls, that is, those 

 considered to have enough usable wood to justify the cost 

 of cutting, were counted, and these were designated as 

 "usable" culls. 



The following information was also recorded for each 

 plot; the number and size of poles, reproduction, stocking, 

 burning in five years, cutting and product cut in five years, 

 and any other pertinent facts. 



Volume Tables. The International X A Inch Rule was used 

 for sawtimber. Form class volume tables were employed to 

 account for variation in lumber yields caused by tree taper. 



All volume estimates are net, defective material having 

 been deducted at the time of making ground measure- 

 ments. Defect is estimated to run about 5 to 8 per cent of 

 gross volume for pine, and 25 per cent of gross volume for 

 hardwood. 



To make a more reliable comparison with Forest Sur- 

 vey estimates, and thereby show trends in timber supplies, 

 volume tables for under-sawlog-size were developed from 

 existing Forest Survey tables. These tables are given as 

 follows : 



ESTIMATED VOLUME IN UNDER-SAWLOG-SIZE 

 TREES 







PINE 



HARDWOOD 





d.b.h. 

 inches 



No. 

 cords 



d.b.h. 

 inches 



No. 

 cords 



North Coastal Plain . . 



... 6" 



.04 



6" 



.04 



and 











South Coastal Plain 



8" 



.09 



8" 

 10" 

 12" 



.09 



.149 



.225 



Piedmont 



... 6" 



.037 



6" 



.036 





8" 



.089 



8" 

 10" 

 12" 



.087 

 .149 

 .226 



Mountains 



... 6" 



.038 



6" 



.036 





8" 



.089 



8" 

 10" 

 12" 



.070 

 .099 

 .203 



LAND USE IN NORTH CAROLINA 



County Statistics : total land, forest, and non-forest area. 

 The information assembled in Table 1 appears to be as 

 reliable as any available at present. Total land areas for 

 counties are from careful re-measurements made by the 

 1940 U. S. Census. They differ considerably, in some cases, 

 from total county areas listed by the Census in previous 

 decades, but are assumed to be correct as aerial photogra- 

 phy has provided an improved basis for accuracy. 



The acreages of land in each county devoted to forest 

 and non-forest purposes are not accurately known. As in- 

 dicated by foot notes, forest acreage figures were obtained 

 from three sources and it is believed the great majority 

 will be within 10 per cent of the correct acreage. The 

 sample counties in which land use determinations were 

 made from aerial photographs, are believed to be accurate, 

 although slight changes will have occurred since the time 

 the aerial photographs were made. Generally speaking, 



(3) 



