588 JOURNAL OF FORESTRY 



This paper is not based upon any special or detailed studies of 

 succession, but rather upon general observation over a number of years 

 in the mountainous territory of Colorado and Wyoming. It is not so 

 much my purpose to describe the important forest successions in this 

 region from the scientific, ecological standpoint as to indicate the prac- 

 tical importance to the forester of having in mind this conception of 

 the systematic development of vegetation by definite stages. This is 

 only one of thousands of examples in which scientific conceptions be- 

 come of practical importance in pointing out the laws of nature, in 

 warning against attempts by man to dodge their operation, and in 

 showing him how they may be controlled. 



In the region of which I speak there may be recognized four climax 

 associations with which the forester is concerned. These are the 

 Jituipcnis-Pinits-hylion, or Pinon-juniper open woodland forest ; the 

 Pinns-hyVwn, or yellow pine forest; the Pseiidotsiiga-hylion, or Doug- 

 las fir forest ; the Picea-Abies-Jiylion, or subalpine spruce forest. These 

 have been named in the order of their zonation. Clements, in his 

 latest work on "Plant Succession," recognizes for this region only 

 three climaxes, combining my second and third units under the name 

 Pinus-Pseudotsugarhylion. It is true that foresters similarly try to 

 simplify the matter, but more often speak of the yellow-pine type and 

 the "transition" or Douglas fir-pine type as separate units. I think it 

 can be quite easily shown that the yellow pine and Douglas fir forests 

 represent two distinct climaxes. It is, further, of practical value to 

 distinguish them, because one frequently occurs in a region without the 

 other; and where they occur in the same general locality it is under 

 such widely difl'erent edaphic conditions that the distinction is more 

 than the distinction between two consociations of the same formation. 



In practical forestry the primary aim is to perpetuate the forest 

 without the expense of planting. We are therefore concerned with 

 secondary successions or subseres much more than with priseres. 

 This is distinctly not the case, however, in artificial forestation work, 

 and I regret to say that many attempts have been made to plant forests 

 where the edaphic conditions, when carefully scrutinized, are found to 

 indicate a stage of development far below that which would naturally 

 bring the climax forest into existence. It is true that forest planting 

 with nursery stock has been a success in the sandhill region of Nebraska. 

 and even on gravel slides in the Pikes Peak region. Both of these 

 habitats are at stages below the climax development. In both of these 



