istics of individual stands. Stands more than 160 
years of age were considered as a whole to have no 
present net growth. Although some stands above 
this age are increasing in merchantable volume, 
others are actually losing in merchantable volume; 
thus in these older stands losses due to mortality 
and to decay approximately balance growth. 
Stands not more than 160 years of age were classed 
as growing stands. For all these stands growth 
computations were made. 
Four conceptions of rate of growth were con- 
sidered: Current annual growth, realizable mean 
annual growth, potential annual growth, and 
periodic growth. These terms as used in this 
report are defined as follows: 
Current annual growth is the volume increase 
that took place in 1933. 
Realizable mean annual growth is (1) mean an- 
nual growth from 1933 to 2032 of existing stands, 
or to dates earlier than 2032 for those areas which 
it is assumed will be depleted before that date, plus 
(2) mean annual growth on portions of areas now 
deforested or to be deforested that presumably 
will restock before 1952. These calculations were 
made for each of the three decades from 1933 to 
1962. 
Potential annual growth is the average quantity 
of timber that can be grown annually if all the 
commercial conifer forest land produces 75 percent 
of full capacity. 
Periodic growth is growth within a given period— 
in this study, 10 years. It was estimated for each 
of the three decades from 1933 to 1962. On the 
basis of these estimates and of assumptions as to 
future depletion, future inventories at 10-year 
intervals during that period were estimated. 
The requirements phase of the forest survey 
consisted of a determination of present and prospec- 
tive requirements for wood products of the Douglas- 
fir region. Estimates of the quantities of these 
products needed in the future cannot be made solely 
on the basis of needs within the region. Interchange 
of products between regions necessitates determina- 
tion of future requirements on a national basis. 
Obviously, this region with its enormous forest 
resources and comparatively sparse population can 
supply its requirements for practically all kinds of 
forest products indefinitely. The only wood prod- 
ucts consumed in this region that must be imported 
are small amounts of hardwood material such as 
flooring and interior finish, and articles manufac- 
tured of woods not grown in this region, such as 
certain kinds of furniture and implement handles. 
The principal sources of these items are eastern and 
southern United States, the Philippine Islands, 
South America, and Central America. 
