78 MICHIGAN SURVEY, 1908. 



through the tamarack swamp and peat bog; second, through the gravel 

 beach and arbor vitae swamp; third, through the rock beach and 

 Gladonia clearings. Physiographic forces have some direct part in 

 causing the successive changes in ecological factors, but most of them 

 are due to the retroaction of the vegetation upon the habitat. The first 

 stages of the series are marked by a severity of conditions which limit 

 the fauna to a few well adapted species. The intermediate stages have 

 generally a wide variety of conditions, leading to the development of 

 a varied fauna. The most noteworthy in this respect is the fauna of 

 the Gladonia clearings. The ultimate or climax stage is homogeneous 

 because of the dominance of a few species, and the fauna is again lim- 

 ited to a few well adapted species. 



, i^ke. 



}. 



Original 



Inland Lake 



Roek Be ash. 



Hook Clearing 



Jaok Pine 



Birch - Aspen 



^ Beach Pool 



Grovel Beach 



Tamarack-Arbo 

 Vltao Swamp 



Intermediate 



SaiJ.eainfSpruoe 



Climax 



