12 
BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE. 
may neutralize the volume produced h\ thriftier trees, so that no net 
growth appears. For illustration, take the Plumas plot, considering, 
for the sake of brevity, only yellow pine, which formed 86 per cent 
of the original and 74 per cent of the present volume. On the basis 
of the previously discussed tree classes, the remaining merchantable 
trees were divided by field observation into two groups, the first in- 
cluding trees which would be cut under present marking methods, 
the second including trees which would be reserved. The compara- 
tive annual rates of growth of the two groups during the 10 years 
since cutting are shown in Table 8, expressed in basal area per- 
centages. 
Table 8. — Comjyaratire annual rates of grmcth. 
Diameter classes. 
Group. 
12 to 17 
18 to 23 
24 to 29 
30 to 3.5 
36 plus. 
Num- 
ber. 
Per 
cent. 
Num- 
ber. 
Per 
cent. 
Num- 
ber. 
Per 
cent. 
Num- 
ber. 
Per 
cent. 
Num- 
ber. 
Per 
cent. 
Num- 
ber. 
Per 
cent. 
To cut 
32 
104 
0.84 
1.77 
1.30.") 
33 
73 
0.85 
1.34 
1.095 
33 
28 
0.72 
.90 
.81 
27 
18 
0.48 
.59 
. 53«5 
12 
3 
0.35 
.60 
. 47."> 
140 
.226 
0.60 
1. L8 
S.Q 
Percentage deviation of 
trees to cut from the 
-3 
5.6 
—2 
2.4 
-11. 1 
-in. 3 
— 2fi- 3 
—32.6 
* 
Expressed in volume, the trees which would have been cut totaled 
118,200 board feet, which produced 10 board feet per acre annually, 
while the total volume of those which would have been left was 
96,840 board feet, which produced 63 board feet per acre annually ; 
that is, 45 per cent of the total volume produced 61 per cent of the 
total growth. Such a cutting would have reduced the stand left from 
57 to 18 per cent of the original volume, would have added 4,930 
board feet per acre to the cut, and probably would have resulted in 
more rapid growth per cent of the trees left than actually occurred 
on the larger number reserved. 
On one 20-acre plot on the Stanislaus a stand per acre was left of 
24,100 board feet, containing 16.9 trees over 12 inches in diameter. 
which formed 46 per cent of the original volume. There were left 
14 yellow pines and 12 sugar pines over 42 inches in diameter, the 
largest tree being an 82-inch sugar pine 215 feet high. Considering 
the quality of this site, which approached Site I, a rate of growth 
2-J to 3 per cent annually might be expected. The average rate main- 
tained by the surviving trees, however, was only 1.44 per cent in 
basal area, and the net total increment in board feet was only 0.93 per 
cent annually. The reason for this is clearly the presence of over- 
mature, slow-growing trees, as will be seen from Table 9. 
For any given size class, sugar pine maintained, in general, its 
normal position as to rate of growth, but its aggregate rate was 
lower than for any of the other species. The high proportion of 
sugar-pine trees in the larger-size classes gives the explanation. The 
same condition was true to a lesser extent of the other species. 
