topographic features and using his knowledge of the country 
the field examiner was able to make a sufficiently accurate 
map for an area as large asa county. The site maps were in- 
tended to show not the site class of specific small areas but 
the area of each site class in the county. 
The final field job was “adjustment cruising”’ of contrib- 
uted cruise data. It was impossible to adjust these data to 
survey standards without resorting to field work because (1) 
specifications were often incomplete or lacking and (2) errors 
made by cruisers might have caused considerable inconsist- 
ency in a given cruise. The adjustment cruising consisted 
in cruising well-distributed sample areas according to the 
specifications adopted for the forest survey and comparing 
the results with the original cruise data. The size chosen for 
the individual sample was 160 acres. 
Volume was recorded for quarter-acre circular plots at 
214-chain intervals, or for 16 such plots on each 40-acre 
tract; in other words, a 10-percent cruise was made. The 
circular-plot system was admirably adapted to the purpose, 
and speeded up the work. Locations of all doubtful line 
trees were determined with a tape, all trees apparently more 
than 60 inches d. b. h. were measured for diameter, and a 
considerable percentage of the smaller trees were measured. 
Heights were measured with the Abney level and by taping 
a number of windfalls each day. Deductions for breakage 
and defect were calculated for each 40-acre tract. These 
deductions were carefully checked, for each tract cruised, by 
examining felled and bucked timber on neighboring logging 
operations and by interviewing superintendents, foremen, 
check scalers, and managers of logging operations in the 
vicinity. 
Per-acre volume of the hardwood stands, usually not in- 
cluded in commercial cruises in the region, had been deter- 
mined by the type mappers, but information was lacking as 
to the volume of the hardwood timber occurring as an under- 
story in mature coniferous forests. As a part of the adjust- 
ment-cruising project, therefore, data on this hardwood un- 
derstory were collected. 
Each check cruiser compiled his data currently and made 
frequent comparisons with the original cruise until he was 
satisfied that the results were consistent and that reliable ad- 
justment factors could be computed. Usually 3 to 4 percent 
of the area included in the original cruise was check cruised. 
Compilation of Data 
In many counties a year or more elapsed between the com- 
pletion of the original field work and the beginning of com- 
pilation. In such cases the status of areas logged and burned 
in the intervening period had to be investigated. This in- 
volved a check of cutting and fire records, and in some cases 
additional field mapping. 
Before type acreages could be computed it was necessary 
to determine the exact land area of each township, each 
county, and each national forest. General Land Office plats 
were used for townships for which they were available. 
148 
Areas of unsurveyed townships were determined by plani- 
metering the most accurate maps available. 
Information as to ownership was obtained from county 
records for county-owned and municipal lands, State records 
for State-owned lands, Department of Interior records for 
national-park, Indian, and revested grant lands and for un- 
appropriated public domain, and Forest Service records for 
All land not shown by public records to be 
public property was considered private. 
national forests. 
Acreage for each of the various types and for divisions of 
some types by age class and degree of stocking was deter- 
mined for each section and for each ownership class from the 
field maps. For each national forest this was done by com- 
partment, block, and working circle and also by county. 
Acreage was determined by use of the planimeter or by 
counting squares. 
Site-class acreages were compiled for each county and 
Percent- 
ages of total acreage in each site class represented were 
determined for each township in the same manner, for use 
in computing volume of second-growth stands. 
Volume data for national forest areas were compiled by 
applying to type areas the stand-per-acre values determined 
in the field. Volumes were compiled by compartment and 
were summarized by block and finally by working circle. 
For areas outside national forests, the adjustment factors 
national forest from site maps by planimetering. 
determined by check cruising were applied to the volume 
figures taken from existing cruise records and the corrected 
totals, recorded by section, township, and county. Vol- 
umes for areas of merchantable timber, including hard- 
woods, not covered by previous cruises were compiled by 
applying to each area the figure for stand per acre shown by 
the type map. Commercial cruises had omitted a large 
majority of the second-growth stands in which the average 
breast-height diameter was below a standard ranging, ac- 
For uncruised 
second-growth stands in which the trees averaged 16 inches 
d. b. h. or more, volumes were obtained from tables adapted 
from the Douglas-fir yield tables (72). Volume data for 
second-growth areas were segregated from the others. 
cording to species, from 20 to 24 inches. 
Depletion-Study Methods and Sources 
Cutting Depletion 
The data taken on depletion by cutting covered the mate- 
rial removed not only as sawlogs but also as so-called minor 
timber products. 
material actually taken out of the woods, omitting sound 
The records used included only wood 
material left by operators on the ground as nonutilizable. 
This sound unused material entered the study only when 
future depletion was being estimated. Its quantity had 
been accurately determined in a previous study (7). 
The study of annual log depletion was based on the 9-year 
period 1925-33 because more and better data were ayvail- 
able for this period than for any other. It is true that in this 
period sawlog production reached a peak that it may never 
reach again, but the period included some years of extremely 
