CHAPTER XI 



ANIMAL COMMUNITIES OF SWAMP AND FLOOD-PLAIN FORESTS 



I. Introduction 



Swamp forests are those which arise in the areas formerly occupied 

 by ponds and lakes and which grow in water or very wet soil. About 

 Chicago the many coastal and morainic lakes of earlier periods have been 

 filled by organic detritus and more or less completely occupied by trees. 

 Often the trees have grown upon floating bogs such as sometimes occur 

 about lakes, though sometimes they have sprung up on solid ground and 

 compact organic detritus. 



II. Swamp Forest Formations and Associations 



We shall consider these forests genetically: the marsh which often 

 appears first, the shrub stage which follows, and finally the forest. 



I. THE ELM-ASH SWAMP FOREST COMMUNITIES 



a) The marsh association (Station 52; Table XLI). — One of the best 

 examples of this community is at the north end of Wolf Lake, Ind. The 

 youngest part is occupied by bulrushes and Hibiscus, and covered in the 

 spring by about a foot of water which teems with small crustaceans, 

 mosquito larvae, and red water-mites. Lymnaea reflex, usually about 

 half the size of the specimens (100) of permanent ponds, and the small 

 bivalve (Musculium) are present. As the season advances the water 

 dries up and the eggs of the crustaceans and adult mollusks live through 

 the dry season on the bottom of the pool. Above the water on the 

 Hibiscus are the small Succinea retusa (91, 100), which belong to the 

 forest edge and low prairie. 



b) Shrub association (forest edge sub-formation) (Station 52; Table 

 LXIII). — Surrounding the central pool which we have described is 

 usually a girdle of buttonbush. Here we recognize several strata. The 

 subterranean stratum has few inhabitants. We have recorded none. 



The ground stratum is not inhabited by many animals. The wood- 

 cock and the northern yellowthroat (108, 153) probably occasionally 

 nest here on the ground, possibly also the common shrew (Sorex 

 personatus St. Hil.) (142). There is no distinct field stratum, as the 



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