he et i? 
1905] WHITFORD—FORESTS OF FLATHEAD VALLEY 289 
the others the cones would be absent. If a fire should sweep through 
this young growth, destroy it, and at the same time consume some 
of the original forest around it, thus extending the limits of the 
original burn, what would be the result? The extent of the burned 
area being greater, the seeds of the trees bordering it could not so 
readily be carried to the center of the burn. But this portion of the 
clearing would be restocked with the seeds of young lodgepole pines 
that were destroyed by fire, but whose seeds would be more or less 
protected from the fire by the cones. Some of the cones would be 
cracked open by the heat of the fire and the seeds would be liberated. 
The result would be that the ‘next forest would contain more repre- 
sentatives of lodgepole pine than the former forest, and that they 
would be more numerous in the center. Indeed this center might 
contain a pure growth of lodgepole pines. Another such fire in the 
course of fifteen or twenty years or less would enlarge this area at 
the expense of the other species. Thus almost if not quite pure 
forests of lodgepole pines of considerable extent would be established. 
It is very probable that the mature lodgepole pine forest found in 
Swan River valley was established in this way (fig. 23). The evidence 
for this is as follows: 
I. In no case was astand of this species found in which there were 
not noted dead and charred trunks of western larch and Douglas 
spruce, mostly the former; these because of the thick bark would be 
the last to yield to the fire. In some instances mature live trees of 
Western larch were observed towering above the younger lodgepole 
Pine forest. In these cases there were isolated specimens of young 
"estern larch of about equal age growing with lodgepole pines (fig. 12). 
2. In nearly all cases these forests grade imperceptibly into more 
Mature forests in which the lodgepole pine element is entirely or nearly 
Wanting. The mature forests of western larch, Douglas spruce, 
silver pine, lowland fir, and lodgepole pine are in many instances 
Stowing in soil that is similar in moisture content. Thus it cannot 
be said that the difference in the two stands is due to the character of 
Soil conditions. 
3- In the meso-hydrophytic situations there is often a gradation 
from a spruce forest to a mixture of Engelmann spruce and lodgepole 
Pine, the latter stand being much younger than the former. 
ES ee tO ee ee a ae 
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