fresh to saline conditions associated with 

 the overriding geomorphic processes. 



Perhaps one exception to this gener- 

 alization is the fresh floating marsh. 

 This marsh is a thick (up to 1 m) mat of 

 interwoven roots binding decaying peat 

 into a platform that floats on the water. 

 It supports a diverse flora of emergent 

 species dominated by Panicum hemitomon. 

 The origins of these mats is 

 Russell (1942) suggested that 

 by growing out into lakes from 

 line. O'Neil (1949) thought 

 began as anchored marshes that 

 from their substrate during 



not known, 

 they arise 

 the shore- 

 that they 

 broke loose 

 a high-water 

 period because of the bouyant force of the 

 mat. The fresh floating marshes are in 

 many respects highly self-controlled. 

 Since they float they are never deeply 

 flooded, but by the same token the water 

 level is always near the marsh surface. 

 The production of organic matter maintains 

 the floating mat. Thus the vagaries of 

 water supply are effectively controlled, 

 and the hydrologic environment of the 

 floating marsh is nearly constant. 



c 

 re 



a 



I 



g 

 III 



> 

 a. 

 o 



Flooded Sediments 



[rrprrirrfi 

 SSSSy Drained Sediment 



k 



^l 



. k 



t* S 



B. 



h 



^ 



h 



L3. 



R C 



P 



S ALTERNI FLORA S CYNOSUROIDES 



R- Roots 

 C- Culms 

 P - Plant 



Figure 39. Effects of substrate drainage 

 conditions on the dry weight accumulation 

 by (A) Spartina alterniflora and (B) S^. 

 cynosuroides (reproduced from Bot. 

 Gazette, 1978 by R.T. Parrando, J.G. 

 Gosselink, and C.S. Hopkinson with per- 

 mission of The University of Chicago). 



42 



