Cull Estimates 



Allowance for defect in merchantable sawtimber 

 trees was determined by estimating sound and rotten 

 board-foot cull in sample trees. From curves of cull 

 over diameter class, species with similar cull percents 

 were grouped and a weighted cull percent was com- 

 puted for the group. The cull allowance determined 

 by the Forest Survey fell between the cull percent 

 found on timber sales from the Wayne-Hoosier 

 Purchase Units and the results of a grade-yield study 

 made by Purdue University. 



The cubic-foot cull in sawtimber trees was estimated 

 in a similar manner. However, estimates of cubic-foot 

 cull in sawtimber were made for unsound defects only. 



Trees of pole or sawtimber size that did not qualify 

 as merchantable trees were tallied as cull trees. 

 Eighty percent of the gross volume of sound cull trees 

 was estimated to be sound wood, and 40 percent of 

 the gross volume in rotten cull trees was sound wood. 



Growth Estimates 



Cores were taken from 1,861 sample trees, and radial 

 growth for the past 10 years was measured. Growth 

 rates were computed by diameter classes and species, 

 by determining ratios of sample tree volume for the 

 last 10 years to the present. These 10-year ratios 

 were converted to annual compound growth rates and 

 plotted over d. b. h. for each species. All trees that 

 died within 4 years prior to the survey and that were 

 formerly merchantable were tallied, and ratios of 

 mortality to stand volume were computed. Growth 

 and mortality percentages were applied to the cubic- 

 foot volume of total growing stock and to the board- 

 foot volume of sawtimber to get the net volume growth. 



Timber-Cut Estimates 



Estimates of timber cut from Indiana forests in 1949 

 were made by a sampling survey of wood-product 

 producers and wood users, and studies of logging 

 operations to determine the amount of cutting 

 residue. 



The amount of timber cut for sawlogs was deter- 

 mined by supplementing the annual lumber survey of 

 the United States Bureau of the Census. Lumber 

 tally was converted to log volume, International ){- 

 inch scale, and the volume of logging residue added. 

 The timber cut for lumber was distributed by species 

 in proportion to the 100-percent canvass of the 1947 

 census. 



An area sample was used to determine the timber 

 cut for fuelwood, fence posts, and miscellaneous farm 

 timbers. One hundred and fourteen area segments 

 of the Master Sample of Agriculture were canvassed 

 with the aid of personnel from the State Extension 

 Service and the State Division of Forestry. 



Timber cut for veneer, cooperage, handles, pulp, 

 and excelsior was determined by a complete canvass 

 of processors in Indiana and adjacent States. The 

 production reported from Indiana timber by the 

 processors was converted to timber cut by adding the 

 logging residue. 



The timber cut for round mine timbers was based 

 on the production of coal from deep mines. A study 

 of Illinois deep mines showed that 0.118 cubic foot of 

 wood is required for each ton of coal produced. The 

 1949 coal production of Indiana's deep mines was 

 multiplied by this factor. 



The timber cut for hewn crossties was determined 

 by a canvass of the concentration yards. 



Timber cut was also estimated by recording data 

 from stumps found on field plots one-fifth of an acre 

 in size. Analysis of these data gave information on 

 timber cut by tree diameters and by species. 



Accuracy oj Estimates 



Forest area and timber volume. — Statistical anal- 

 ysis of forest area and timber volume data in Indiana 

 shows a sampling error of ±1.2 percent (±48.6 

 thousand acres) for commercial forest area and of 

 ±1.8 percent (±46.3 million cubic feet) for growing 

 stock volume. This means that at one standard error 

 the chances are 2 out of 3 that the estimated area and 

 volume would not differ from the totals that would 

 have been obtained by 100 percent measurement by 

 more than the values shown. 



These estimates of sampling error do not include 

 errors resulting from the development and application 

 of volume tables and cull factors, or from mistakes in 

 measurement or judgment. All phases of field and 

 office work were closely supervised to keep these 

 errors to a minimum. 



Since the percentage error increases with each 

 subdivision of the total, small acreages or volumes 

 may have large errors and may therefore indicate only 

 relative magnitudes. Table 2 may be used as a guide 

 in estimating the probable sampling error of the sub- 

 divisions of forest areas and volumes in the tables. 



Timber cut. — Most of the timber cut was estimated 

 by sampling producers. Possible errors include 



Indiana's Forest Resources and Industries 



31 



