dominate higher, drier locations above 

 mean high water where the red mangrove 

 does not appear to have a competitive 

 advantage. She suggested that competition 

 is not so important during the early 

 stages of succession but becomes critical 

 as individual trees reach maturity and 

 require more space and other resources. 



Inherent in Ball's concept of zona- 

 tion is the differential influence of 

 physical factors (e.g., soil salinity, 

 depth to water table) on the competitive 

 abilities of the different mangrove 

 species. She concluded that succession 

 proceeds independently within each zone, 

 although breaks in the forest canopy from 

 lightning strikes or high winds may pro- 

 duce a mosaic of different successional 

 stages within a zone. These openings 

 allow species whose seedlings do not com- 

 pete well in shade, such as the white 

 mangrove, to become established, at least 

 temporarily, within solid zones of red 

 mangroves. 



Zonation of mangrove species does not 

 appear to be controlled by physical and 

 chemical factors directly, but by the 

 interplay of these factors with interspe- 

 cific competition and, possibly, through 

 tidal sorting of propagules. Once succes- 

 sion in a mangrove zone reaches an equili- 

 brium state, change is unlikely unless an 

 external perturbation occurs. These per- 

 turbations range from small-scale distur- 

 bance (lightning strikes) to large-scale 

 perturbations (sea level change, hurricane 

 damage) and may cause succession within 

 zones to regress to an earlier stage. 

 There is some evidence in south Florida 

 that hurricane perturbations occur on a 

 fairly regular basis, creating a pattern 

 of cyclical succession. 



Except for Ball (1980) and Taylor 

 (1980), the importance of fires as an 

 influence on mangrove succession has been 

 generally ignored. Most fires in the 

 Florida mangrove zone are initiated by 

 lightning and consist of small circular 

 openings in the mangrove canopy (Taylor 

 1980). These openings present an opportu- 

 nity for secondary succession within an 

 established zone. For example, we have 



frequently observed white mangroves 

 flourishing in small lightning-created 

 openings in the center of red mangrove 

 forests. Fire may also play a role in 

 limiting the inland spread of mangroves. 

 Taylor (1981) pointed out that Everglades 

 fires appear to prevent the encroachment 

 of red and white mangroves into adjacent 

 herbaceous communities. 



Finally, Lugo and Snedaker (1974), 

 Cintron et al. (1978) and Lugo (1980) 

 suggested that mangrove ecosystems 

 function as classical successional systems 

 in areas of rapid sediment deposition or 

 upon recently colonized sites such as 

 offshore islands. They concluded that in 

 most areas mangrove forests are an example 

 of steady-state cyclical systems. Concep- 

 tually, this is synonymous to E. P. Odum's 

 (1971) cyclic or catastrophic climax. 

 Chapman (1976a, b) suggested the idea of 

 cyclic succession for a variety of coastal 

 ecosystems. 



If Florida mangrove ecosystems are 

 cyclic systems, then there should be an 

 identifiable perturbation capable of set- 

 ting succession back to an early stage. 

 Lugo and Snedaker (1974) suggested that 

 hurricanes may play this role. They 

 pointed out (without substantiating data) 

 that major hurricanes occur about every 

 20-25 years in south Florida. Coinci- 

 dently, mangrove ecosystems appear to 

 reach their maximum levels of productivity 

 in about the same period of time (Lugo and 

 Snedaker 1974). This hypothesis suggests 

 that succession within many mangrove eco- 

 systems may proceed on a cyclical basis 

 rather than in the classical fashion. 

 Possibly other physical perturbations may 

 influence mangrove succession including 

 incursions of freezing temperatures into 

 central Florida, periodic droughts causing 

 unusually high soil salinities (Cintron et 

 al. 1978), and fire spreading into the 

 upper zones of mangrove forests from ter- 

 restrial sources. 



Although understanding of zonation 

 and succession in mangrove ecosystems 

 remains incomplete, a clearer picture is 

 emerging, at least for south Florida. 

 Contrary to early suggestions, mangrove 



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