When marsh plants ^i e , t he dead material begins at once to disintegrate 

 under the force of wind, tides, animal trampling, and other mechanical means. 

 As plant materials drop to the mud surface, they decompose into detritus 

 particles largely because of microbial action (Figure 1). The rate at which 

 detritus is formed from dead plants has been the subject of several studies. 

 The "litter bag" method, which is the most widely used procedure to determine 

 the rate of decomposition, measures the rate at which fragmented pieces and 

 particles of dead plants are lost from nylon mesh bags after one year of 

 exposure in the field. The rate is expressed as percent loss of the original 

 material from the bags. In studies using this method, the decomposition rate 

 was 50 to 96 percent for S^. alterni flora , 35 to 47 percent for J^. roemerianus , 

 and 38 to 53 percent for Distichlis spicata . The decomposition rate of other 

 coastal plants, including mangrove leaves, falls within these ranges (38 to 53 

 percent). The variation in decomposition rate is due to differences in tex- 

 ture and fiber strength of the marsh plant species studied, the methods used 

 (specifically, the mesh size of the nylon bag), time intervals of measurements 

 during the year, geographic latitude, and environmental conditions (e.g., tem- 

 perature and the frequency and duration of inundation). In the studies cited, 

 the rate is a direct function of mesh size, which varied from 1 mm to 10 mm. 

 The environmental conditions to which the litter bags were exposed influenced 

 the breakdown rate of plant tissues; consequently, plant materials continuously 

 submerged decomposed faster than materials kept on the high and dry marsh. 

 The rates also differed greatly with regard to species. In general, the ten- 

 der, more succulent plants such as Sal i corn i a and Scirpus decomposed much 

 faster than other grasses and rushes, such as Spartina and Juncus . 



Although data are not yet available on the decomposition rates of 

 roots and rhizomes, studies on this subject are currently underway. The 

 significance of the various components of a rhizospheric plant lies in 

 the value of these components to the estuarine food web as an energy 

 source, assuming that portions of the underground organic production 

 find their way into the estuarine food web and are not totally decomposed 

 in situ or formed into peat. Some of the below-ground material may also 

 be lost to the system through respiration or in the production of methane 

 by microorganisms. 



Detritus is valuable as a food source because of its high source of 

 energy and chemical constituents. There is very little energy variation 

 in the values determined for different species of marsh plants at dif- 

 ferent phenological stages from living to dead, and through various stages 

 of decay. The caloric content is usually slightly higher for detritus 

 than for mature live plants. The retention of, or slight increase in, 

 caloric content of decaying detritus is due to two factors: (1) an 

 increase in the microflora impregnating the detritus; and (2) the retention 

 of high organic content in the detritus, despite elemental losses. It has 

 long been observed that the protein content of particulate detritus is 



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