Floral diversity of mangrove plants with reference to palaeoenvironment during holocene in Bengal Basin, India

摘要

Fresh sub-surface peat samples were collected and palynologically investigated from two different locations at Rajarhat area, N-24Paraganas, 20 km northeast of Kolkata where work was done in connection with building construction. The pollen analytical investigation of the collected peat samples reflected the existence of a large number of core mangroves and some fresh water elements and ferns from a peat layer located at the depth of about 2.2 m-3.5 m below the surface. The present investigation reveals the age of the peat layers ranging from 2665 to 6530 BP, confirming the Holocene age of the samples. The dominant pollen grains recorded from the samples were Heritiera, Excoecaria, Avicennia, Bruguiera, Barringtonia, Rhizophora, Sonneratia, Suaeda, Phoenix paludosa, Nipa and a large number of fern spores including Acrostichum and grass pollen, reflecting a diversity of mangrove vegetation. The variability of the vegetation in the peat from bottom to top shows the change of monsoon months during the Holocene in the BengalBasin. The swampy halophytic vegetation of the Holocene is to some extent comparable to the present day vegetation of the Sunderbans.