similar to that of temperate zone salt marshes and are generally con- 

 sidered their subtropical and tropical equivalents. 



Established mangroves are very effective stabilizers (Carlton, 

 1974). The black mangrove produces extensive accessory root systems 



(pneumatophores) that form dense mats in and above the soil surface. 

 The red mangrove [Rhizophora mangle') 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 mangroves require 5 or more years to develop prop roots. 

 This can be cut in half by growing plants under controlled conditions 



(Howard 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 

 vulnerable to damage or disturbance from wave and tidal action, float- 

 ing 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 im- 

 practical except in small-scale, special purpose plantings. 



Fortunately, a natural sequence along 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 Dunstan, 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 establishing vegetative cover in the intertidal 

 zone. Stabilization can be accomplished rapidly and at low cost by 

 planting smooth cordgrass. This will be followed on most sites by the 

 natural invasion and eventual takeover of mangroves, if there is an 

 adequate seed supply. 



Planting of mangrove seed, seedlings, or plants in the cordgrass 

 stand soon after stabilization would speed the transition, if desired. 



(1) Mangroves . Three mangrove species occur along the Florida 

 coast: the red mangrove (Fig. 13), the black mangrove (Fig. 14), and 

 the white mangrove {LagunoulccP'ta raaemosa) (Fig. 15). Red mangrove 

 tolerates the deepest submersion, white mangrove the driest soil, and 

 black mangrove the highest salinity. Black mangrove is the most cold- 

 hardy but the slowest grower. White mangrove has the least cold 



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