26 Forest Club Annual 



The above keys do not include all the species of conifers 

 which may be found in Colorado, for instance, I have omitted 

 the unimportant tree, Sabina utahensis. With some workers 

 there is a tendency to " split up" certain of the species as above 

 treated making a greater number of species of the remnants. 

 Some botanists attempt to make Juniperus siberica from a form 

 of Juniperus communis, but such an attempt defeats the purpose 

 of classification for the beginner, because J. siberica is not dis- 

 tinct from J. communis At any rate for the present purpose 

 it is best to recognize a single species. So Pinus edulis has been 

 called Caryopitys edulis, and Pinus flexilis has been called 

 Apinus flexilis. I prefer to use the older nomenclature. 



It must not be expected that all of the above species are 

 found in all parts of the state. The pinon pine is essentially 

 southern and southwestern, while the lodgepole pine is essen- 

 tially central and northern. Considerable variation in the 

 altitudinal range of the species will be noticed by the student. 

 Some of the more prominent characteristics of this altitudinal 

 range will be considered in the following pages. 



The extremely wide range of habitat variation, or variation 

 in the site, to be found in the Rocky Mountains cannot be 

 equalled in any other part of the United States. The fact is due 

 primarily to the rugged topography of this particular mountain 

 system. Nowhere else within our borders is vegetation sub- 

 jected to such extreme and such varied conditions. Starting 

 from an altitude of about 6,000 feet in the desert plains we pass 

 very rapidly up through the foothill region, into the subalpine 

 and finally into the Alpine grasslands and bleak Alpine summits 

 at altitudes varying from 13,000 feet to above 14,000 feet. And 

 all this may occur within a very few miles. Indeed by ascending 

 from the plains to 14,000 feet one may travel not more than fifteen 

 miles in many instances, but nevertheless he may in that distance 

 experience the same climatic conditions, the same types of vege- 

 tation, and in fact meet many of the identical species which he 

 would meet in traveling many days and many hundreds^ of 

 miles from the same starting place to within the Arctic Circle. 

 Certainly in the shorter distance the changes in vegetation are 

 much more striking because they have been brought within 

 such a few miles. We shall presently inquire with more de- 

 tail into some of these changes. 



The factors which are potent in the initiation of and in the 

 development of the forest or of vegetation in general may be 

 classified under three heads according to their nature as follows: 

 1. Climatic, 2. Edaphic, and 3. Biotic. 



