320 



ECOLOGICAL FACTORS: 



open 



gallery woodland 



floating-leaved 



— r:;::^-— -""submerged 



Figure 17.13 Developmental stages in an eutrophic lake. The successional sequence is from left 

 to right. 



leaves are usually neither thin, dissected, nor linear. 

 Common plants include certain pondweeds {Potamoge- 

 ton), water lilies (Nymphaea) , and water buttercup 

 {Ranunculus aqualilis). 



Emergent Stage. This stage features emergent 

 anchored hydrophytes. Because of its vegetation, the 

 stage also is called a tule, reed, or cattail marsh. 

 Characteristic species are bullrush or tule {Scirpus), 

 reed (Phragmites), and cattail (Typha). 



Saturated Soil Stages. The area from within the edge 

 of a body of water out to the end of the land zone of 

 soil saturation might have three communities; how- 

 ever, only one or two of these stages may be present 

 in a given area. Only two are always associated with 

 saturated soil. They are presented in their usual or- 

 der of succession. 



Sedge-meadow stage: The herbaceous vegetation of 

 this area also makes it a marsh. Predominant plants 

 include sedges (C'arex), rushes (Junciis), spike rushes 

 (Eleocharis), and smart weeds (Polygonum). The roots 

 and rhizomes of these plants form a dense, tough, 

 sodlike mat. Within this mat are many organisms 



found nowhere else in the area. Also, this stage fre- 

 quently has an understory herb and perhaps other 

 layers of plants and animals. 



Thicket stage: Saturated to moist soils in rela- 

 tively drier surroundings often have shrub vegetation 

 along the margin of the body of water. The shrubs 

 are variable from place to place. However, willows 

 (Salix) are present in most localities having this 

 swamp community. 



Atotst Soil Stages. The moist soil stages are dis- 

 tinct shore situations. Although brushland and 

 fringing woodland stages are included, the brushland 

 is of quite restricted occurrence. 



Brushland stage: Bushes, low shrubs, and stunted 

 trees forming more or less closed communities on the 

 borders of arctic and alpine vegetation or along cold 

 streams or lakes are called brushlands. Water 

 usually is abundant; however, low absorption and 

 high water loss present conditions unfavorable to 

 forest development, yet more favorable than in colder 

 areas where excessive dryness or snow fields prevent 

 growth of trees. The stage could just as well be 



