complete and after which seedling estab- 

 lishment can take place. Rabinowitz 

 (1978a) estimates the obligate dispersal 

 period at approximately 8 days for white 

 mangroves, 14 days for black, and 40 days 

 for red. She further estimates the addi- 

 tional time for root establishment at 5, 

 7, and 15 days for white, black, and red 

 mangroves, respectively. Her estimate for 

 viable longevity of the propagules is 35 

 days for white mangroves and 110 days for 

 black. Davis (1940) reports viable propa- 

 gules of red mangroves that had been kept 

 floating for 12 months. 



Rabinowitz (1978a) also concluded 

 that black and white mangroves require a 

 stranding period of 5 days or more above 

 the influence of tides to take hold in the 

 soil. As a result, these two species are 

 usually restricted to the higher portions 

 of the mangrove ecosystem where tidal 

 effects are infrequent. 



The elongated red mangrove propagule, 

 however, has the potential to become 

 established in shallow water with tidal 

 influence. This happens in at least two 

 ways: (1) stranding in a vertical posi- 

 tion (they float vertically) or (2) 

 stranding in a horizontal position, 

 rooting and then vertical erection by the 

 plant itself. Lawrence (1949) and Rabino- 

 witz (1978a) felt that the latter was the 

 more common method. M. Walterding (Calif. 

 Acad. Sci., San Francisco; personal com- 

 munication 1980) favors vertical estab- 

 lishment; based upon his observations, 

 surface water turbulence works the propa- 

 gule into the substrate during falling 

 tides. 



Mortality of established seedlings 

 seems to be related to propagule size. 

 Working in Panama, Rabinowitz (1978b) 

 found that the mortality rate of mangrove 

 seedlings was inversely correlated with 

 initial propagule size. The white man- 

 grove, which has the smallest propagule, 

 has the highest rate of seedling mortal- 

 ity. The black mangrove has an interme- 

 diate mortality rate while the red man- 

 grove, with the largest propagule, has the 

 lowest seedling mortality rate. She 



concluded that species with small 

 propagules establish new cohorts annually 

 but die rapidly, while species such as the 

 red mangroves may have long-lived and 

 often overlapping cohorts. 



Propagule size and seedling mortality 

 rates are particularly important in con- 

 siderations of succession and replacement 

 in established mangrove forests. Light is 

 usually the most serious limiting factor 

 underneath existing mangrove canopies. 

 Rabinowitz (1978b) suggested that species 

 with short-lived propagules must become 

 established in an area which already has 

 adequate light levels either due to tree 

 fall or some other factor. In contrast, 

 red mangrove seedlings can become estab- 

 lished under an existing, dense canopy and 

 then, due to their superior embryonic 

 reserves, are able to wait for months for 

 tree fall to open up the canopy and pre- 

 sent an opportunity for growth. 



2.4 BIOMASS PARTITIONING 



Few investigators have partitioned 

 the total biomass, aboveground and below- 

 ground, contained in a mangrove tree. An 

 analysis of red mangroves in a Puerto 

 Rican forest by Golley et al. (1962) gives 

 some insight into what might be expected 

 in south Florida. Aboveground and below- 

 ground biomass existed in a ratio of 1:1 

 if fine roots and peat are ignored (Figure 

 5). In this case, peat and very fine 

 roots (smaller than 0.5 cm diameter) ex- 

 ceeded remaining biomass by 5:1. Lugo et 

 al. (1976) reported the following values 

 for a south Florida red mangrove overwash 

 forest. All values were reported in dry 

 grams per square meter, plus and minus one 

 standard error, and ignoring belowground 

 biomass. They found 710 - 22 q/m l of 

 leaves, 12. 8„ - 15.3 g/m z of propagules, 



iles, 

 f of 



7043 i 7 g/m z of wood, 4695 ± 711 g/rr 

 prop roots and 1565 - 234.5 g/m z of detri- 

 tus on the forest floor. 



Biomass partitioning between dif- 

 ferent species and locations must be 

 highly variable. The age of the forest 

 will influence the amount of wood biomass; 



15 



