ADJACENT 

 \ WATER 



Figure 40, A conceptual 

 and processes. 



O DEPOSITS IN 

 DEEP SEDIMENTS 



model of a typical wetland ecosystem, showing major components 



parvula , Cha ra vulgaris and Potomageto n 

 spp. are found. 



Emergent Vascular Plants 



The energent vascular plants are by 

 far the most intensively studied of these 

 four groups. Much plant biomass 



infonnation about delta marsh species has 

 been generated during the past decade. 

 Seven studies of marsh grass productivity 

 covering nine plant species have been 

 performed (Table 13) . 



The most common infonnation related 

 to production is peak end-of-season 

 biomass. In iiore northerly climates where 

 all growth ceases and the plants are 

 killed to the ground during the winter, 

 this is often an excellent estimate of 

 true net production. But in the 



subtropical climate of the gulf coast peak 

 biomass has been shown to underestimate 

 production by a factor of 1.6 to over 4, 

 even in those species that have a single 

 growth cycle each year (Hopkinson et al . 

 1978a). As a result, one must interpret 

 peak bianass data with caution. Table 13 

 shows production estimates vary 



considerably, but most estimates are very 

 high compared to studies in other 

 localities in the temperate zone. This 

 is because production generally increases 

 with decreasing latitude (Turner 1976). 



The seasonal growth of marsh plants 

 in Louisiana shows two patterns (Figure 

 41). One is characteristic of annual 

 plants and many species witii perennial 

 roots that die to the ground every winter. 

 These species have a single, smooth growth 

 curve which builds from near zero in 

 January to a peak sometime between July 

 and September. Each year almost all of 

 the new stems anerge at once when growth 

 commences in the spring. In Figure 41 P_. 

 austral is illustrates this group. For 

 species like this, peak biomass represents 

 about 40 - 60 percent of annual net 

 production. The rest is accounted for by 

 shedding of leaves during the spring and 

 some continued growth into the fall that 

 is masked by mortality after the peak is 

 attained. Sagittaria falcata appears to 

 follow the same growth pattern, but 

 actually the individual leaves of this 

 species have a short lifespan and are 

 replaced constantly throughout the year. 



44 



