International Journal of Environment (ISSN: 2186-0009)  

Vegetative and Reproductive Phenology, and Litterfall Production of Rhizophora stylosa in Okinawa Island, Japan
Sahadev Sharma, Md. Kamruzzaman, A.T.M. Rafiqul Hoque, Kangkuso Analuddin and Akio Hagihara
Mangrove forests in Japan are at their northern limits, and are distributed from the Yaeyama Islands in the subtropical zone to the southern part of Kyushu Island in the warm-temperate zone, and therefore they are poor in species. Mangroves growing in subtropical region have very few knowledge regarding phenology. This species is growing in its northern limit and ambient climatic conditions, so therefore phenology and litterfall studies are needed to know its adaptation strategies and growth. In this study, Phenological traits of a subtropical Rhizophoraceae mangrove, Rhizophora stylosa Griff., are measured during the period of April 2008 to March 2010. The litterfall traps were emptied monthly and the litterfall was sorted into leaves, stipules, branches, flower buds, fruits, fruits expanded and hypocotyls were counted monthly. Litterfalls showed a seasonal pattern: the highest peak occurred during summer and the lowest during winter. Mean annual total litterfalls of the 1st year and 2nd year were respectively estimated as 931.7±16.6 and 1321.9±31.2 (SE) g m-2 yr-1. Leaf litterfall comprised 65.2 (1st year) and 49.7% (2nd year) of the total litterfall. Conversion of fertilized flowers into fruits was greater than half (75 - 90%), though transition of fruits to propagules was less successful (1.3 - 3.3%). Therefore, we can conclude that the survival rate of reproductive units was low, with very few of flowers converted into propagules (1.2 - 2.5%). The reproductive cycle of Rhizophora stylosa was seasonal. In general, the species presented flowering peaks from May to September when temperature was high.
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