TIMBEE GKOWIXG AXD LOGGIXG PRACTICE IX C.AXIFORXIA 45 
operations, however, are already cutting- all species to a diameter 
of 12 to 16 inches indicates an unfortunate trend. 
In mixed stands, current practice tends to eliminate the pines as 
a factor in the next forest, so that except for the chance occur- 
rence and survival of advance reproduction the new stands will 
consist largely of the less valuable firs and cedar. 
THE NUMBER OF SEED TREES OBTAINABLE WITH DIAMETER-LIMIT CUTTING 
The representation and distribution of diameter classes are of 
first imj^ortance in determining the efficiency of the diameter-limit 
method of obtaining sufficient seed trees. Obviously, if the 20-inch 
diameter limit is to be adopted, there must be enough trees already 
on the ground to leave for the purpose intended. In studying this 
question, no method is superior to that of using stand tables, based 
on timber survey tally sheets. 
5 
A 
'f''':^^ 
3 8%-v^ 
/ 
' / 
y 
y^ 
36" 
TREES LEFT UNDER 
20MNCH DIAMETER LIMIT 
TOTAL CUT FROM STAND 
Fig. 17. — Percentage distribution of trees and volume of stand, by diameters. While 
38 per cent of the total number of trees on this area are left standing by an applica- 
tion of a 20-inch cutting limit, the curve for total volume of stand shows that this 
considerable number of trees amounts to only 7.5 per cent in volume. The whole rela- 
tion of number of trees to volume in a typical stand is well shown in this analysis of 
their distribution by diameters 
EAST SIDE YELLOW PIXE 
In two stands of 410 and 640 actual measured acres in east side 
yellow pine, the representation of diameter classes and the corre- 
sponding volumes of each were determined. In the pure yellow pine 
area there is a dearth of trees 10 to 16 inches in diameter, and 18 
and 20 inch trees average four per acre: whereas in the yellow pine 
with a slight admixture of white fir there are decidedly more small 
trees. In either of these stands the average number of seed trees 
per acre would be -ample for restocking with cutting to a 20-inch 
limit. Figure IT indicates that of the total number of trees, 38 
per cent are 20 inches in diameter or smaller, but that these trees 
make up only about T.o per cent of the total volume of the stand, or 
in this case about 1,000 board feet per acre. For the extensive 
stands of which this is a fair sample, such an investment in seed 
trees does not appear excessive. 
