Periodic Saw- Timber Growth 
In order to estimate board-foot timber inventories for the 
Douglas-fir region as of the years 1943, 1953, and 1963, 
periedic annual board-foot growth was computed for each 
of the three decades following 1932. Advance in age and 
differences in type areas because of depletion were the 
only changes taken into account; no changes from the 1933 
conditions were assumed in either species composition of 
stands or stand density. 
TasLe 42.—Periodic conifer saw-timber growth in the Douglas- 
fir region 
Periodic growth of trees 15.1+ inches 
d.b. h 
District and unit 
1933-42 | 1943-52 1953-62 
Million | Million | Million 
Puget Sound: board feet | board feet board feet 
North Puget Sound_-___- 1, 146 | 1, 294 1, 499 
Central Puget Sound_-- 1, 288 | 1,615 1, 906 
South Puget Sound____------- 2,491 | 2, 289 1,731 
TRotaletes aes aes ea 4,925 | 5, 198 5, 136 
| 
Grays/Harbor=2- = 2ess-ss5eoes 1,905 | 1,779 1, 462 
Columbia River: 
Columbia River Washington _ 2, 270 2, 433 2, 283 
Columbia River Oregon__-_-_- 1, 568 | 2,081 2, 482 
Total: oe 34 oes See eee 3, 838 4, 514 4, 765 
Willamette River____..----------- 4, 216 4, 540 4,799 
| 
Oregon coast: 
North Oregon coast 3________- 2, 805 | 2, 698 2, 303 
South Oregon coast 4_-_----__- 2, 946 3, 256 3, 435 
Total seese soe eee a 5, 751 5, 954 5, 738 
South Oregon: 
UmpquadRivers2 23 222s 2, 414 2, 396 2, 286 
Rogue: River-2222s22s--- 22-6 192 296 462 
Totalsseses oes cee ee 2, 606 2, 692 2, 748 
Region totals ees ae | 23, 241 24, 677 24, 648 
Summary by districts: Percent | Percent Percent 
Puget,Sound=-a.0).28 252!) 22 21. 2 | 21.1 20.9 
Grays Harbors}. == 8.2 7.2 5.9 
Columbia River____ 16.5 18.3 19.3 
Willamette River__.___.__--__ 18.1 18.4 19.5 
Orezonicosst. === ~ ee 24.8 24.1 23.3 
South! Oregousss22 2 ee eee 1b) 10.9 11.1 
Totals = es ceee eee ne 100.0 100.0 | 100.0 
1 Data are shown only for stands 160 years or less in age, on commercial 
conifer forest land. 
2 Estimated in 32-foot logs to 12-inch top, Scribner rule. 
3 Data exclude growth on 182,060 acres of potential conifer forest land 
temporarily occupied by hardwoods. 
4 Data exclude growth on 14,520 acres of potential conifer forest land 
temporarily occupied by hardwoocs. 
150 
This process resulted in the periodic net conifer growth 
figures shown in table 42. Because relatively little incre- 
ment is contributed by hardwoods, periodic growth was 
computed only for the conifer types. 
It is estimated that those of the existing conifer stands 
that survive to 1943 will put on a net growth of 23.2 billion 
board feet during the decade 1933-42, those that survive 
to 1953 will grow 24.7 billion board feet during the decade 
1943-52, and those that survive to 1963 will grow 24.6 
billion board feet during the decade 1953-62. According 
to the estimates of decadal volume increment and those of 
depletion (shown in table 20), the 1933 net volume inven- 
tory of 546 billion board feet, log scale, for the region will 
be reduced to 492 billion board feet by 1943, to 431 billion 
by 1953, and to 381 billion by 1963. 
Method of Computing Realizable 
Mean Annual Growth 
For those who are interested in the detail of the technique 
employed in computing realizable mean annual growth, a 
sample computation is given in table 43. Calculations for 
type 6 (Douglas-fir old growth more than 40 inches d. b. h.) 
appear in the first three lines. Type 6 is assumed to be 
nongrowing, and accordingly no stocking value is shown 
for it. ‘The value in line 2, column 13, was calculated on the 
assumption that 80 percent of the area depleted in 1933-42 
will restock by 1948. The assumed average stocking of this 
area is indicated in line 2, column 5, and the estimated 
average age attained by the second-growth stands is shown 
in line 2, column 15. The entry in line 2, column 19, is 
55 percent of normal mean annual growth per acre for 
Douglas-fir stands to age 85 years. The entry in line 2, 
column 24, is the product of those in line 2, columns 13 
and 19. Since growth is calculated only from the middle 
of the period 1933-42, half this amount is entered in line 2, 
column 26. Since it is assumed that the second-growth 
stands will continue to grow during the whole of the period 
1953-62, the total value is given in line 2, column 27. 
The entries in line 3 were calculated in the same way as 
those in line 2. 
Calculations for type 8 (Douglas-fir second growth, 22 to 
40 inches d. b. h.) appear in lines 4, 5, and 6. The growth 
rate applied for the first decade (Jine 4, column 16) is the 
periodic annual growth rate for ages 90 to 94 years, inclu- 
sive, of normal Douglas-fir stands on sites of a quality mid- 
way between II and III multiplied by 0.60, the estimated 
average stocking for type 8. Growth is assumed only to 
the middle of the decade 1933-42. The growth rate ap- 
plied to the type 8 area assumed to be depleted during the 
decade 1943-52 is the periodic annual rate for ages 90 to 
104 years, similarly adjusted for stocking. Growth is as- 
sumed only during three-fourths of the 20-year period 
1933-52. In calculating growth on the area assumed to 
be depleted during the decade 1953-62, the equivalent of 
0.833 of the 49,000 acres was assumed to be growing during 
the entire 30-year period 1933-62 and the normal periodic 
