Background
Attempt to compare the phonological pattern of the three mangrove species: Heritiera fomes, Bruguiera sexangula, and Xylocapus mekongensis in the Sundarbans mangrove forest by observing the litterfall data over 3 years.
Results
All these three species showed highest litterfall of leaves and stipules in summer and lowest in winter. In case of B. sexangula, it also showed its second peak of leaves litterfall in the rainy season. Branch litterfall for the three species was occurred all over the year without having a distinct seasonal pattern. Flowering was observed in February – June and March - May for H. fomes and X. mekomgensis, respectively. Fruiting was observed for H. fomes and X. mekongensis in between the month of March – May and April – June respectively. Peak of mature fruit or seed litterfall was observed in July and August for both H. fomes and X. mekongensis respectively. Litterfall of flower buds, flowers and propagule for B. sexangula was observed throughout the year and peak flower buds, flowers, and propagule litterfall was found in the month of January, March, and July respectively. Kendall’s coefficient of concordance showed that all the organs of litterfall were concordant during the study period. Autocorrelation coefficient revealed that all the parts of litterfall followed a clear annual cycle except branches. Mean total litterfall was calculated 1014.6±12.7 g m-2 year-1 for H. fomes, 1047.3±21.3 g m-2 year-1 for X. mekongensis and 1640.2±14.1 g m-2 year-1 for B. sexangula of which leaves litterfall contributed more than 50% of total litterfall for all the three species. H. fomes, B. sexangula and X. mekongensis none of them exhibit any correlation between stipules litterfall and reproductive organs litterfall.
Conclusion
The findings may contribute to an understanding of vegetative and reproductive phenology, litterfall production, and carbon sequestration rate of the major mangrove species in Sundarbans mangrove forests, and also its role in global C budgets.