LIFE HISTORY OF 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 fnore 
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,: 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. 
- 17he form of lodgepolé pine occurring in the Rocky Mountains, now known as Pinus 
contorta, has also been known as Pinus contorta, var. murrayana, and as Pinus mur- 
rayand, , 
