FOREST TYPES IN CENTRAL ROCKY MOUNTAINS. 149 



This species, like the other pines discussed, is evidently light-demand- 

 ing; but, unlike the other pines which through long ages have 

 adapted themselves to the surface drying which results from direct 

 insolation, the germination of lodgepole seeds is slow, and the devel- 

 opment of root in the young seedling is feeble. For this reason 

 lodgepole commonly reproduces on fully insolated sites only where 

 there has been complete denudation, as by fire, and where its moisture 

 supply is made as certain as possible by the destruction of its com- 

 petitors. More frequentlv than not, mature lodgepole stands are so 

 open as to give plenty of light for germination; but as the open stand 

 results from limited moisture it follows that the seedlings may 

 develop only very slowly and may be wiped out in drought years. 

 The greater the moisture and the denser the lodgepole stands, the 

 more certain it is that spruce seedlings rather than lodgepole will 

 predominate in the reproduction, and that the ground can be regained 

 for this more valuable tree. On the other hand, on drier ground 

 which probably once belonged to Douglas fir, there may be much less 

 opportunity for the fir to take possession primarily because of its 

 very inferior seeding capacity. For this reason much of the ground in 

 this region which is capable of supporting high-quality fir stands will 

 be very slow in returning to that species. 



That lodgepole pine is almost completely absent from the imme- 

 diate territory of this study appears to be due to a dry atmosphere, 

 a loose, rapid-drying surface soil, and hence less favorable condi- 

 tions for germination than it demands. On sites where the conditions 

 for germination might be favorable, it is possible that soil freezing 

 may be prohibitive. The growth of lodgepole trees planted on yellow- 

 pine sites in the Pikes Peak region has been excellent, but establish- 

 ment by direct seeding has been accomplished only in a few favored, 

 though warm, spots. 



APPLICATIONS. 



The value of a more exact knowledge of the forest trees with which 

 we are dealing in the National Forests of the central Rocky Mountains 

 should be evident to anyone at all familiar with the problems of 

 forestry. To what extent knowledge of any fact may affect human 

 plans and activities can never safely be prognosticated. Yet it is 

 safe to point out some of the benefits that may be had immediately 

 as a result of facts brought out by this study or previously discovered 

 and, perhaps, confirmed by the large amount of data here presented. 

 It is necessary, of course, to refrain from generalizing; yet it must 

 be apparent to foresters in other regions that in each forest region 

 there are counterparts of the species here discussed. It may, there- 

 fore, be helpful to understand the relations between species as they 

 have here been depicted. 



Neither the physiological investigations nor the field data secured 

 in the present study indicate any marked difference between the 

 species in actual drought resistance; and b} r this is meant ability to 

 extract water from the soil when the condition of physiological dry- 

 ness is being approached. If there is any such difference, it is 

 theoretically in iavor of the species which are commonly thought of 

 as demanding moist sites, but which in reality demand cool sites, 

 namely, spruce and iir. On the other hand, a species like spruce 

 which is accustomed to moist, rich soils and develops a compact root 



