WESTERN YELLOW PINE IN OREGON. 
19 
small group by themselves, the reason being that a group of many 
young trees usually starts in the gap which a large one makes when 
it dies. In the virgin stands throughout the State there seems to be 
a very large proportion of trees whose age is about 225 or 275 years, 
suggesting that after this age their mortality is greater. 
Table 5 shows the uneven age of an average yellow-pine stand. 
It is an enumeration of the trees of each age on a logged-over tract 
near Embody, Lake County, the rings on the stumps of practically 
all the sound merchantable trees being counted. 
Table 5. — Number of trees of each age by decades on a representative 40-acre tract near 
Embody, Oreg., only trees (cut in a clean-cutting logging operation) whose annual 
rings could be counted being taken. 
Num- 
Num- 
Num- 
Num- 
Age. 
ber of 
Age. 
ber of 
Age. 
ber of 
Age. 
ber of 
trees. 
trees. 
trees. 
trees. 
100 
4 
190 
22 
280 
15 
370 
3 
110 
2 
200 
19 
290 
9 
380 
1 
120 
13 
210 
8 
300 
7 
390 
1 
130 
8 
220 
13 
310 
11 
400 
5 
140 
14 
230 
17 
320 
8 
410 
2 
150 
31 
240 
28 
330 
13 
420 
2 
160 
16 
250 
21 
340 
10 
430 
1 
170 
21 
260 
13 
350 
6 
440 
6 
180 
20 
270 
10 
360 
2 
450 
17 
NUMBER OF TREES PER ACRE. 
Table 6 shows the average space in square feet controlled by trees 
of various sizes in a representative stand of pure yellow pine in cen- 
tral Oregon. 1 
Table 6. — Space available to average trees of various sizes in pure yellow-pine forests. 
'?, 45 trees. 
[Data taken near Mill Creek, Crook County.] 
Diam- 
Space 
available 
Diam- 
eter 
class. 
Space 
available 
eter 
class. 
to each 
tree. 
to each 
tree. 
Square 
Square 
Inches. 
feet. 
Inches. 
feet. 
16 
1,031 
26 
1,022 
18 
944 
28 
1,307 
20 
1,122 
30 
1,405 
22 
' 1,225 
32 
1,366 
24 
1,235 
34 
1,947 
By this table it is seen that each tree 16 inches in diameter occupies 
in the virgin forest 1,031 square feet, allowing thereby only a possible 
42 trees per acre; if they averaged 30 inches in diameter and required 
1,405 square feet, there would be space for but 31 trees. But there 
are usually so many gaps in the yellow-pine forest that there are 
considerably less than this possible theoretic number of trees. The 
difference between the yellow-pine and the Douglas-fir forests is 
1 The area controlled by each tree is considered to be the irregular polygon about the tree whose corners 
are at half the distance to each neighboring tree's base. 
