LIFE HISTORY OF LODGEPOLE PINE IN EOCKY 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 P. B. Clements in Colo- 

 rado are given in Forest Service Bulletin 79. 



62799°— Bull. 154—15 2 



