invade new areas and has been considered the chief agent for shoreline stabi- 

 lization in Florida (Davis, 1940). The isopod parasite (Spaevomz terebrans) 

 causes serious damage to red mangrove roots on some sites (Teas, 1977). 



Savage (1972) points out that black mangrove may be preferable for shore 

 stabilization. It is more cold-hardy, more tolerant of artificial substrates 

 and high-energy conditions, and provides earlier and more complete protection 

 through the development of an accessory root system (pneumatophores) than the 

 other two species. White mangroves appear to have the lowest value for stabi- 

 lization because the seedlings have more fragile root systems and are very 

 slow to develop accessoi^r roots. It invades and coexists with the other two 

 and contributes to stability in this way. 



The red mangrove usually fringes the shoreline. Apparently, this species 

 is able to establish at slightly lower water levels than the other two. Where 

 both mangroves and salt marsh occur together, the mangroves extend seaward of 

 the salt marsh. Mangroves, once established, can tolerate deeper water than 

 salt marsh plants. Mangroves easily form hedges along developed waterfront 

 property. Savage (1972) found that all three species respond well to selec- 

 tive pruning. Thus, they can be used to replace or protect bulkheads and 

 still fit landscaping plans, and can be pruned to avoid visual obstruction. 

 Mangroves play a role in stabilization and primary production similar to that 

 of temperate zone salt marshes and are generally considered their subtropical 

 and tropical equivalents. 



Established mangroves are very effective stabilizers (Carlton, 1974). The 

 black mangrove produces extensive accessory root systems that form dense mats 

 in and above the soil surface. The red mangrove develops a system of prop 

 roots which provides substantial trapping capacity. However, these tree 

 species require considerably more time for complete establishment and are more 

 difficult to establish on bare sites than are the grasses in the intertidal 

 zone. Savage (1972) found that a minimum of 3 or 4 years is required for 

 black mangrove seedlings to develop stabilizing roots; red mangrove seedlings 

 require 5 or more years to develop prop roots. This can be cut in half by 

 growing plants under controlled conditions (H. Teas, Botanist, University of 

 Miami, Coral Gables, Florida, personal communication, 1978). Even so, this 

 means a period of at least 2 to 3 years from planting of mangrove seeds or 

 seedlings to stabilization, compared with 9 to 14 months for smooth cordgrass. 

 Also, the slow development of mangrove seedlings makes them much more vulner- 

 able to damage or disturbance from wave and tidal action, floating debris, 

 traffic and browsing by animals and insects than most salt marsh species 

 (Savage 1972; Teas, Jergens, and Kimball, 1975). The alternative of planting 

 4- to 8- year-old plants, which have a better chance of survival, would be 

 expensive and appears to be impractical except in small-scale, special purpose 

 plantings. 



Fortunately, a natural sequence along many of these shores is the initial 

 stabilization of newly exposed intertidal sites by smooth cordgrass, followed 

 by the invasion of mangrove seedlings. The smooth cordgrass is gradually 

 overcome and eliminated through shading as the mangroves develop into trees 

 (Lewis and Eunstan, 1975, 1976). Evidently, the mangrove seedlings establish 

 more easily after the substrate has been stabilized by the grass. The natural 

 sequence of grass, followed by mangroves, offers a practical method of 



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