



STAND. 25 
mann spruce, aspen, and occasionally Gambel oak, until with in- 
crease of altitude yellow pine may be altogether replaced by pure 
stands of Engelmann spruce. In pure stands of yellow pine the 
ground cover is usually pine grass, bunch grass, and in openings 
erama of various species. The grasses are distributed in clumps or 
patches, interspersed with layers of pine leaves of various depths, 
according to the density of the sand. Underbrush is rare. Occa- 
sionally buck brush is found at the lower and briers at the higher 
elevations. Varying age classes give pure western yellow pine a 
variety of aspects. In places it is made up of thrifty pole stands 
of blackjack, with an occasional mature yellow pine fast declining in 
vigor. In others there may be an old mature stand of veterans, 
with complete reproduction beneath. On the limestone formations, 
with deep soil, the stand is usually more thrifty than on lava 
(malpais). 
STAND. 
AVERAGE STANDS. 
To determine the number of trees per acre in an average stand of 
western yellow pine, surveys were made in different situations with 
varying conditions, and the results tabulated by 3-inch diameter 
classes. 
Table 12 gives the results of valuation surveys on a portion of the 
Prescott National Forest, upon which a working-plan estimate was 
based, and which are indicative of average conditions in the more 
open yellow-pine stands on dry situations in the Southwest. The 
small number of trees per acre is typical. The largest tree recorded 
was 37 inches in diameter breast high. 
TABLE 12.—Average stand of western yellow pine on 128 strip acres, Prescott 
National Forest. 


Diameter | Trees per || Diameter | Trees per | 
breast high. acre. breast high. acre. 
Inches. Inches. 
4-6 ad 25-27 0.5 
7-9 5.3 28-30 2, 
10-12 4.2 31-33 - 03 
13-15 3.4 34-37 03 
16-18 Divi Over 12 10. 46 
19-21 28 Over 18 4. 36 
22-24 1.3 






The number of trees per acre in average stands on the Coconino 
and Tusayan National Forests is given in Table 13. Here again, 
though under more favorable conditions than on the Prescott, the 
number of trees per acre is small. Since no healthy blackjack are 
marked for cutting in Government timber sales, except in thinnings, 
timber-sale estimates usually differentiate between blackjack and 

