ECOLOGY OF, ISLE ROY ALE. 3 



The ecological relations in the north are so different, in some respects, 

 from those farther south, that one may easily form an erroneous con- 

 ception of the conditions under which such a preliminary investigation 

 may be made. A very favorable condition for the work was the fact that 

 practically all the time was devoted to it, instead of only occasional 

 trips being made for the purpose, as is necessary with those busy with 

 other duties. There are also certain advantages in being able to be in 

 the field continuously, as a certain familiarity with conditions is ac- 

 quired in the beginning, especially where the variety of forms is limited, 

 which otherwise would involve time tipon each visit. Although 

 most of the members of our party were upon the island only during July 

 and August, yet at this time those seasonal phenomena were concen- 

 trated which require much more, or several times that amount of time 

 for their development farther south. The seasonal contrast is well il- 

 lustrated when the summer season at the other extreme of the State of 

 Michigan — 500 miles away — is contrasted with that of Isle Eoyale. Such 

 relations are further reinforced by the fact that the species and 

 societies which are dominant in the various northern habitats are 

 very much smaller in number than farther south. This necessarily sim- 

 plifies the j)i'oblem, and to a corresponding degree reduces the chances 

 of error in anticipating biotic changes which are correlated with those 

 of the environment. This is a relation of much importance in the study 

 ■of succession. The writer was especially impressed with the relative 

 simpUeiti/ of the problem of environmental relations and of the biotic 

 succession upon Isle Eoyale, and has received further confirmation of the 

 opinion that a tendency to exaggerate the complexity of the environ- 

 ment is prevalent. 



An important aid in environmental analysis has been received from 

 the effort to distinguish the major or geographic features of the gross 

 environment from the minor habitat unit.S which make up the mosaic 

 or complex, although their mutual and genetic relations were not 

 overlooked. Some of these relations have been well expressed by 

 Montgomery in his comment on distribution ('06, p. 6) as follows: 

 "And, as is always the case Avhen. the method has been consistent and 

 scientific, the factors of distribution and the meaning of it will ulti- 

 mately be stated in ^'ery simple form. These factors appear to us now 

 to be enormously complex, but this is because we have hardly com- 

 menced to analyze them." 



At this point it should be mentioned that there are certain dif- 

 ficulties which tend to confuse the field worker, which, if clearly 

 understood, will often be of aid in ecological studies. In pursuing 

 field studies, in addition to a knowledge of the species, one of the first 

 essentials is a familiarity with the habits and habitat preferences of 

 organisms; and further, there should be the ability to recognize how 

 the dominance of one society is transformed into that of another. 

 The lack of a sufficient power of constructive imagination makes the 

 detection of such transformations very difficult, perhaps even impossible 

 to some. This limitation almost completely restricts such a student 

 to the purely descriptive phases of field ecology, because the explanatory 

 phase lies beyond his grasp, although there remains for him a large 



