It was thought that in the decade 1943-52, as a 
result of reduction of timber supplies in other forest 
regions, a greater proportion of the national lumber 
requirements would be supplied by this region. 
Furthermore, increase in the population of the 
West should increase local lumber consumption 
and result in increased markets. Considering these 
and other factors, it was estimated that annual 
cutting depletion for the decade 1943-52 would 
average 8 billion board feet. 
In view of the tendency of national population to 
become stable and the trend toward decreased per 
capita consumption of lumber, it was anticipated 
that by about 1950 national lumber consumption 
would again decline. By this time the eastern and 
southern forest regions, close to the large centers 
of population, should have increased their forest 
productivity so as to be more nearly self-sufficient, 
thus limiting the market in the East for lumber from 
the Pacific coast. An annual depletion by cutting 
of 7 billion feet was assumed for the decade 1953-62. 
Assumptions as to future losses from fire were 
based on past rates of loss adjusted to meet changes 
in inventories. The net area burned annually per 
100,000 acres was computed for each type. After 
analyzing these data, it was decided to combine the 
types into 10 groups and assign a net annual rate of 
loss per 100,000 acres, exclusive of that caused by 
catastrophes, to each group (table 50). Next, on 
the assumption that one such catastrophe as the 
great Tillamook fire of 1933 might be expected 
each 30 years and that it would destroy on the 
average approximately 150 million feet of timber 
on about 4,500 acres annually, catastrophe loss 
rates were computed for the saw-timber types and 
oy) 
added to the rates previously calculated for ordinary 
fire losses. 
A future net loss from wind throw of 75 million 
board feet annually was assumed and was converted 
to an acreage basis by using average-stand-per-acre 
figures for the types in which such loss occurs, 
derived from inventory check-cruise data. The 
result was about 1,400 acres per year. The future 
loss from the hemlock looper was assumed to be 60 
million board feet, or 1,200 acres annually. This 
loss will probably occur exclusively in the hemlock 
saw-timber type (type 14). 
Future depletion from cutting as shown in table 
20 for the entire region was prorated to individual 
survey units on the basis of past cutting and amount 
of saw timber available for future cutting in the 
units. The total future cut assumed for each unit 
was prorated to type groups and the acreage cut of 
each type group calculated for national-forest land 
and other land separately. Average volume per 
acre as determined for each type group from inven- 
tory check-cruise data was used to estimate future 
cutting depletion. In so doing allowance was auto- 
matically made for logging waste. 
Acreage depletion from fire, wind throw, and 
insect losses, computed as previously explained for 
each of the three decades, was converted to board- 
foot volume, by use of stand-per-acre values com- 
puted separately for each unit’s national-forest land 
and other land. ‘These estimates were combined 
with cutting estimates for corresponding decades to 
give the total assumed future depletion from all 
causes (table 50). 
junction with growth data to estimate inventories 
for 1943, 1953, and 1963. 
They were later used in con- 
