LIFE HISTORY OP LODGEPOLE PINE IN ROCKY MOUNTAINS. 27 



would doubtless long since have given way to the more tolerant fir 

 had it not been for recurrent fires. On south slopes and on dry, 

 rocky knolls and ridge tops the fir may extend almost to the upper 

 limits of the -lodgepole belt. At the upper limit of the zone the 

 chief associates of lodgepole are Engelmann spruce and Alpine fir, 

 which come in on the moister sites. Spruce sometimes follows 

 stream courses far down into the lodgepole type, where it takes pos- 

 session of the moist bottomlands. Both the fir and spruce are much 

 more tolerant than lodgepole, and reproduce under dense shade. At 

 the higher elevations Alpine fir is apt to be more abundant in repro- 

 duction than spruce, but the latter is a longer-lived tree and of much 

 greater importance in mature stands. Both species when growing 

 with lodgepole assist to a large extent in pruning the latter of its 

 side branches. 



In Colorado and Wyoming limber pine and aspen also grow with 

 lodgepole, though to a rather limited extent. In Montana white- 

 bark pine is usually mixed with lodgepole toward the latter's upper 

 limit. 



PERMANENCY OF LODGEPOLE TYPE. 



Many of the present stands of lodgepole undoubtedly occupy areas 

 previously covered with other species which have been driven out by 

 repeated fires. If fire were kept entirely out of the forests, therefore, 

 the lodgepole would in many situations be replaced by the original 

 species — at the lower altitudes by Douglas fir, at the upper ones by 

 Engelmann spruce and Alpine fir. All of these species are more 

 tolerant than lodgepole, and for this reason are able to crowd it out 

 on sites adapted to all of them. It is likely, however, that there is 

 a middle belt considerably narrower than the present lodgepole zone 

 where conditions of soil and climate are more favorable to it than to 

 competing species, and where it would probably be able to form a 

 permanent type. 



In connection with the ability of lodgepole to maintain itself in 

 competition with other species, it is interesting to know that Knowl- 

 ton, in his studies of the paleobotany of Yellowstone Park, found in 

 Tertiary deposits a serotinous cone of a tree species which he named 

 Pinus premurrayana, 1 because he considered it the immediate an- 

 cestor of the lodgepole of to-day. A fossil cone, perfectly preserved, 

 is slightly longer and narrower than typical lodgepole cones of the 

 present. In Yellowstone Park Knowlton also found the fossil re- 

 mains of species of Sequoia, Juglans, Hicoria, Fagus, Castanea, 

 Ficus, Magnolia, etc. Of all the species now present in the park 

 lodgepole is the sole survivor from the Tertiary age. 



1 The form of lodgepole pine occurring in the Rocky Mountains, now known as Pinus 

 contorta, has also been known as Pinus contorta, var. murrayana, and as Pinus mur- 

 rayana. 



