12 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. 
(Calemagrostis rubescens), the latter usually not more than 8 or 10 
inches high. Furthermore, in full sunlight even mineral soil may — 
dry out so rapidly that many of the seedlings will be killed by 
drought. For this reason young stands are usually more dense on 
mineral soil lightly shaded by recently fire-killed trees than in the 
open. On the other hand, they are likely to be more open on sandy 
soil than on soils better able to retain moisture. The densest seed- 
ling stands are apt to occur on north slopes where there is a rela- 
tively small amount of direct sunlight and a large amount of 
moisture. | 
Competition with other native vegetation, such as blueberry (Vac- 
cimium) and kinnikinnic (Arctostaphylos), for light and soil mois- 
ture often greatly reduces the amount of lodgepole reproduction; 
and the seedlings which do start have a much slower growth than 
where there is no competition. Aspen also is a hindrance to lodge- 
pole, through its more rapid growth when young, wherever the two 
start on the same area. A light; overhead aspen cover, on the other 
hand, may be beneficial by protecting the soil. 
Rodents reduce the seed supply to a certain extent, but there is 
probably always enough seed left for satisfactory reproduction if 
other conditions are favorable. 
> 
OPTIMUM DENSITY. 
The right density for a stand of lodgepole is that at which the 
lower branches become suppressed and die while still small, but with- 
out overcrowding of the trees and consequent decrease in rate of 
growth. Hodson concluded that an original density of 8,000 seed- 
lings per acre is required to produce clean stems at maturity. Later 
investigations show, however, that while this number of seedlings 
would secure good natural pruning, it would be at a great sacrifice 
in diameter growth. In the reconnaissance work on the Deerlodge 
Forest a “normal” seedling stand is considered one of about 1,000 
trees per acre, fairly well spaced and of fairly even height growth. 
By “normal” is meant that degree and character of stocking which. 
will produce the maximum yield of merchantable timber of the de- 
sired sizes at the end of the rotation. Stands containing too few, or 
too many, unevenly distributed trees, are abnormal to the extent to 
which they will fail to produce this maximum yield. Normality is” 
thus seen to differ materially from “density,” which refers to the 
extent to which the crown space is fully utilized. Stands with a 
density of 1.0 are nearly always too crowded for the most satisfac- 
tory development. 
The number of trees constituting a normal stand naturally de- 
creases with the age of the stand. While 1,000 trees per acre, evenly 
spaced, is a satisfactory stocking when reproduction first starts, this 
