LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 9 
admitted to the stand, and probably to some degree upon the tree’s 
height. Tall trees with very poor crowns are often killed outright 
when exposed to full sunlight. The more thrifty and vigorous the 
crown and the shorter the tree, the surer the recovery. Trees which 
stand full light immediately show the greatest increase in growth. 
Observations made so far do not tend to show that the quality of the 
site has any effect upon recovery from suppression. 
REPRODUCTION. 
CONE AND SEED PRODUCTION.1 
Lodgepole pine usually produces a fair crop of seed each year. 
Particularly abundant seed production may occur at two or three 
year intervals, but it is not yet possible to say whether there is any 
uniform periodicity in such years, as is often the case with yellow 
pine and Engelmann spruce. Open-grown trees produce seed at 
an earlier age and in larger quantities throughout life than do trees 
in dense stands. Seedlings in the open have been known to mature 
cones at the very early age of 5 years, while crowded trees in the 
forest may reach an age of 50 years without doing so. In somewhat 
open stands moderate seed production usually begins when the trees 
are from 15 to 20 years old. Careful tests show that seed from trees 
less than 10 years old have as high a germination per cent as seed 
from mature trees. 
Typical lodgepole cones vary in diameter from 1 to 2.5 inches. 
_ The cones are generally larger on open-grown than on close-grown 
trees, and tend to increase in size with the age of the tree up to its 
maturity. They are nearly always flattened on the side oppressed 
- to the parent branch. The extreme basal scales of the cone and from 
3 to 6 scales at the tip do not bear any seeds, but the remainder of 
the scales, between base and tip, nearly always do. Seed-collecting 
_ operations on nine National Forests in Colorado and Wyoming show 
an average of about 26 seeds per cone. The number of cones per 
tree, and consequently the total seed production, varies greatly. 
Clements has estimated the average annual production of seed per 
tree in certain cases at from 21,000 to 50,000. Hence the total seed 
production of a stand may be enormous. Lodgepole is unquestion- 
ably a more prolific and regular seed producer than any of the species 
commonly associated with it. 
SEED DISSEMINATION. 
Lodgepole cones ripen in late August or September of their second 
year. It is a notable characteristic of the species, however, that the 
cones often fail to open and discharge the seed as soon as mature. 
1 Detailed results of an investigation on this subject made by F. E. Clements in Colo- 
_ rado are given in Forest Service Bulletin 79. 
62799°—Bull. 154-152 
, 
