MANGROVE SWAMP CREATION 



Howard J. Teas 



Department of Biology 



University of Miami 



Coral Gables, Florida 33124 



INTRODUCTION 



Mangroves are trees and shrubs that 

 grow at the edge of warm seas of the 

 world. They dominate 75% of the shore- 

 line between 25° North and 25° South 

 latitude (McGill 1959). Mangroves reach 

 their maximum development and diversity 

 in Southeast Asia (Macnae 1968) where 

 Chapman (1970) listed 44 species and 14 

 genera. By contrast, Chapman tabulated 

 only eight species and four genera in 

 the Western Hemisphere. 



The Florida species are the red 

 ( Rhizophora mangle ), black ( Avicennia 

 germinans ), and white ( Laguncularia 

 racemosaT mangroves (Figures 1 through 

 3j! All three species occur in the 

 southern part of Florida. White man- 

 grove is the most cold-sensitive of the 

 three species, red mangrove is interme- 

 diate, and black mangrove (which grows 

 from just south of Jacksonville on the 

 east coast, around the peninsula of 

 Florida, and westward along most of the 

 U.S. Gulf coast to Mexico) is the most 

 cold-resistant. 



Red mangrove fruits germinate on 

 the parent tree to form pencil -shaped 

 propagules (unrooted seedlings). Black 

 and white mangroves form fruits which, 

 like red mangrove propagules, drop from 

 the tree when they are mature. 



A mangrove swamp is a complex eco- 

 system. Although the species of plants 

 are relatively few, the animals are num- 

 erous and diverse (Macnae 1968). The 

 goal of a mangrove planting or replant- 

 ing program should be the development of 

 a functional, diverse ecosystem. 



In this report I will cover factors 

 that are known to be involved in man- 

 grove establishment, review mangrove 

 planting experiments, and evaluate the 

 state of the art of mangrove swamp crea- 

 tion. 



ECOLOGICAL FACTORS IN 

 MANGROVE ESTABLISHMENT 



LIGHT 



Mangroves require open sunlight for 

 optimal growth. The light intensity at 

 ground level under a full canopy of man- 

 grove forest may be only 5% to 10% of 

 the open sun values. Mangrove seedlings 

 ordinarily require more light than this 

 to grow and become trees. Seedlings 

 that fall to the ground under parent 

 trees or are carried by the tides to 

 areas of heavy canopy shade may begin 

 development, but most die. An interest- 

 ing feature of the growth-limiting 

 effects of low light levels can be seen 

 in the portion of a mangrove forest 

 where the canopy has been removed by a 

 lightning strike (Teas 1974). Dense 

 growth of seedlings is found in such 

 lighted openings; however, in nearby 

 shaded areas the low light level sup- 

 pression of seedlings continues (Figure 

 4). 



TIDAL DEPTH AND FLUSHING 



Another factor in mangrove estab- 

 lishment is tidal depth. Many red man- 

 grove seedlings become planted and begin 

 to grow along the shore of Biscayne Bay 

 below mean sea level and even below mean 

 low tide (Figure 5). However, aerial 

 photographs over a decade showed that 

 none of the seedlings at the site shown 

 in Figure 5 developed' into trees at 

 substrate elevations lower than -9 cm 

 (-0.34 ft) below mean sea level (Teas 

 1976). Roots of mature red mangroves 

 often extend 30 cm (12 inches) or more 

 below mean low tide in channels between 

 mangrove islands in south Florida. The 

 difference may be that the roots of the 

 mature trees have well -developed aeren- 

 chyma (air conducting) tissues, whereas 



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