in saline effects, and vice versa (via channelization or hurricanes). The 

 timing of these water fluxes (discussed later) may be very important. 



No matter what their source, water inputs into the brackish marsh will 

 follow one of three pathways: (1) they may percolate into the macropore and 

 micropore spaces of the soil; (2) if the soil is saturated, they may add to 

 the storage of standing water; or (3) they may flow out of the system as runoff. 



The storage of standing water is important for several reasons. First, 

 it provides habitat for all the aquatic plants and animals. Second, the reser- 

 voir of standing water is a regulator of gaseous exchange between the air and 

 soil; this is an important factor in the physiological mechanisms of marsh vege- 

 tation. The depth of water and the duration of submergence help determine the 

 species of plants that will dominate an area. Third, the biological and chemical 

 properties of flooded soils are quite different from those of aerated soils. 

 Of primary concern is the rate of decomposition of organic material, the end 

 products of such decomposition, and the chemical state of nutrients in the soil. 

 In saturated soils, decon'position proceeds slowly and results in reduced forms 

 of end products. The reduced (more motile) forms of trace nutrients predominate 

 also (Redman and Patrick, 1965; Tusneem and Patrick, 1971; De Laune et al., 

 1976). Frequent aeration of saturated soils (via lowering of the water level) 

 allows oxidation of organic materials to intermittently proceed at a faster 

 -ate and thus provides a constant high level of available nutrients to the vege- 

 tation. 



Management practices are oriented toward controlling these forcing functions 

 (water depth, duration of submergence, and frequency of sumergence/emergence) 

 with timing as an added variable. Natural succession can be reversed and held 

 at an earlier stage if all of these factors are properly controlled (Rossa and 

 Chabreck, 1972). 



Sediment . Sediment storage in the brackish marsh may be partitioned into 

 two components - bottom sediment and suspended sediment. Flows of material 

 into and out of the system are suspended in water and are proportional to the 

 rate of flow of water. The nutrients complexed with bottom sediment contribute 

 to the pool of nutrients in the system. The accumulation of bottom sediment 

 leads to an increase in elevation. That portion of the peat due to the rough 

 mat of dead marshhay cordgrass/saltgrass may become very significant, especially 

 when one is considering competition and fire. 



The organic matter content of brackish marsh soils (26 to 49 percent) is 

 intermediate to those of saline and fresh marshes (Chabreck, 1972; Brupbacher 

 et al., 1973). Such a range reflects the balance between importation of mineral 

 materials and deposition of endogenous plant remains. 



Suspended sediment may affect the system via two pathways. The most direct 

 pathway involves siltation effects on benthic flora and fauna. Increased turbi- 

 dity due to suspended sediment may decrease primary productivity by decreasing 

 the light energy available to photosynthetic organisms. 



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