REGENERATION STATUS OF MAJOR MANGROVE SPECIES IN THE SUNDARBAN MANGROVE FOREST OF BANGLADESH (original) (raw)

Natural regeneration can potentially play a major role in large-scale landscape restoration in mangrove areas of Bangladesh Sundarban. Both, biological and physical factors can affect the establishment and early stages along the development of trees. This study examined the response of natural regeneration of major mangroves species in the Sundarban. We recorded appearing of seedlings of different mangrove species in 30 permanent sample plots (PSP) of 400 m 2. The average number of seedlings appearing from 2000 to 2009 were recorded 36,363/year/ha although recruitment densities varied considerably among different parts of the forests. Heritiera fomes, Excoecaria agallocha, Ceriops decandra and other species together constituted 38.45%, 27.81%, 16.98% and 16.78% of the recruits (three months old seedlings) respectively. As well as the average number of seedlings appearing from 2010 to 2016 was found 31,752/year/ha. Heritiera fomes, Excoecaria agallocha, Ceriops decandra and other species together constituted 33.94%, 24.61%, 17.52% and 23.93% of the recruits (three months old seedlings) respectively. There is no statistically significant difference at the 5% level in the seedlings recruitment between the years 2000 to 2009 and 2010 to 2016. If adequate natural regeneration is not established by the end of the fourth growing season, then an alternative regeneration method may be implemented. Chronology of regeneration data revealed that natural regeneration is promising for the Sundarban mangrove forest to ensure a rich stocking in the future if other factors remaining favorable. Introduction The Sundarban, covering about one million ha in the delta of the rivers Ganga, Brahmaputra and Meghna is shared between Bangladesh (60%) and India (40%), and is the world's largest coastal wetlands. The area experiences a tropical monsoonal climate with an annual rainfall of 1,500 – 2,000 mm. Enormous amount of sediments carried by the rivers contribute to its expansion and dynamics. Salinity gradients change over a wide range of spatial and temporal scales. The biodiversity includes about 350 species of vascular plants, 250 fishes and 300 birds, besides numerous species of phytoplankton, fungi, bacteria, zooplankton, benthic invertebrates, mollusks, reptiles, amphibians and mammals. Species composition and community structure vary east to west and north to south, and along the hydrological and salinity gradients. Natural regeneration is the process by which the forest is naturally renewed; it is based on the recruitment of young plants deriving from seeds/propagules. Natural regeneration can successfully occur only if a sufficient amount of " growing space " is available for seed germination and subsequent growth of seedlings. Canopy trees strongly determine the understory light regime and tend to reduce the growing space for the recruitment of young trees into the canopy layer, thus consolidating their dominance. In natural mangroves, the onset of regeneration processes depends on