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Although the prim ary role of mangrove vegetations as photosynthetic prim ary
producers, they are the basis of a complex and productive ecosystem. The mangrove forests in
the tropics are threatened due to the immense human pressure especially through infrastructure development and aquaculture. Therefore information on the change of mangrove species
diversity in different climate conditions and in the location of the forest is useful for restoration and identifying the conservation needs. The species diversity of six mangrove forests of
three different climate regions was examined in this study. Species diversity in bottom, hydromorphic fringe, non-hydromorphic fringe and upland segments of each forest was also
studied. There was no clear species difference in different climate regions. The highest diversity was reported in Negombo Lagoon of wet zone followed by Chilaw Lagoon of dry zone.
Avicennia marina, Excoecaria agaliocha, Lumnitzera recemosa and Rhizophora mucronata
were found in all six forests. Aegicereas corniculatum, Bruigera gymnorrhiza and B. sexangula
were found onfy in wet and intermediate zones. The lowest species diversity was identified in
the bottom segments having R. mucronata, R. apiculata, Acanthus ilicifolius and Scyphiphora
hydrophyllacea. The highest diversity was recorded in the non-hydromorphic fringe segment
where 14 out of 15 totally recorded species were found in that region. Several threats to the
mangrove forests, especially due to infrastructure developments and shrimp farming were
also identified.
