NATURAL REGENERATION OF DOUGLAS FIR. AD 
TABLE 21.—Hjfect of density of stand on height and diameter growth of young 
stands of Douglas fir in south central Washington.’ 
Stands ofless | Standsofmore | Stands of less Stands of more 
| than 2,000 trees | than 10,000 trees than 2,000 trees | than 10,000 trees 
| per acre. | per acre. per acre. per acre. 
ee | || Age in years. | as 
y : | Paes | : Diameter | Diameter ere 
= at lfoot Height. at 1 foot ; at 1 foot ae at 1 foot 
| Height. above | | above Height. above Height. above 
| ground. ground. ground. ground. 
= | bins 
j | Aes | Inches. Tree. Inches. : | Heck: inches HEEL Inches. ‘ 
He oae See dee OB 28 eeeasee ce (OPA oll pee a One| 50) : : 6 
& ces ME ses Roe a a ALT AA Ae SPN oo DEY Las Se pg de Wi Ue EG, 4,2 3 
B Pee eas sc OH Gea Bes ae AAC) es Raho SN Ui Yo ae 9.4 1.9 | 4.8 ; 
ASL REL SIS 1.4 0. 2- 133 ONQI PASS Cee ees 11.8 2:2 5.5 1.0 
2 odo beabesa a 1.9 qo L.5 ee Me Ce ee earn ee Se 14.2 2.3 a3 a 
Breen clayiiense ores 2.5 Ain) 1.8 | BRC AY 3 My eects eligi tla, ©) 2.9 | 2 : 
TR Rh eS. 3.2 ay Dee eal ols Mel eae es 19.4 27 | 8.9 1.3 
RARE ome 4.0 1.0 2.6 OUI aeiyeen eee 22.1 2.819) 105s 1.4 
OE ReR Seed Ve | 5.0 1 320 sibel Size ZA, 7 3.0) |e 2 4 1.5 
1 Read from curves based on measurements of 16.75 acres. 
Young Douglas fir in dense stands is definitely retarded in growth, 
but it does not stagnate. There are always a number of dominant 
trees, and the natural thinning is rapid during the first two or three 
decades. During the period before the stand reaches merchantable 
size, too great density can be remedied only by artificial thinning, 
and this involves considerable expense. Stands may start as dense 
as 50,000 or 60,000 seedlings to the acre, but at the age of 20 years 
they would be reduced to probably not over 20,000. The average 
stands, however, are not so dense. They may contain from 2,000 
to 10,000 seedlings to the acre during the first 15 years, and at 25 
years of age they may not contain more than 2,000 trees. After the 
age of 20 years the thinning continues rapidly. At 35 years of age 
the average acre of Douglas fir forest contains only about 500 trees. 
This number is reduced to about 250 at the age of 50 to 60 years, 
and 75 to 100 trees to the acre at the age of 100 years. Many over- 
mature forests that are now being logged contain from 20 to. 50 trees 
to the acre. 
Growth in a scattered stand would be more rapid during the early 
stages, but the lateral branches would grow to larger size and be 
persistent on the trees. These branches cause the knots that are often 
found in large Douglas-fir trees that have apparently clear boles. 
In the dense stands of young growth the lateral branches are small. 
They die in a few years, and after they fall the trunk remains 
clean throughout the life of the tree and produces clear lumber. It 
is important, therefore, that the stand be started with at least suf- 
ficient density to insure clearing of the trunk in the early life of the 
tree. For this reason it is desirable that there be at least 800 trees 
to the acre, and even a much greater density is not a serious hin- 
drance to the development of the young trees. 
The process of natural thinning results in the loss of a large 
amount of the material grown on an area. If artificial thinning 
were employed, this material could be utilized at different stages 
throughout the life of the forest. The thinnings would improve the 
quality of the remaining trees and increase the rapidity of growth. 
The dense young stands that spring up naturally after logging could 
