Vascular Plant Diversity and their Distribution Pattern in Sandwip Island, Chittagong,Bangladesh

Sandwip is one of the biggest offshore island in Chittagong district of Bangladesh located at 22°22′-22°34′ N and 91°26′- 91°34′ E with an area of 762.42 sq. km. Plant species of the island are at risk because of drought, salinity, anthropological activities and continuous bank erosion in the sea. The main goal of the study is to document the plant diversity of the island before their disappear. Therefore, a study on the vascular plant diversity and their distribution pattern of the island has been conducted during March 2011 to December 2012. Vascular species diversity and distribution pattern are investigated by random quadrat method. A total of 438 vascular plant species under 319 genera and 111 families have been documented from the 48 study sites. Shannon-Wiener diversity index (H`), species richness (d) and Pielou’s evenness index (J`) have been done by using PRIMER v6 program. Plant diversity is higher in the middle part (H` 5.511, J` 0.944 and d 48.49) than the other parts of the island. Highly dominant species of the island are Centella asiatica (L.) Urban., Blumea lacera DC., Cynodon dactylon Pers., Lippia alba (Mill.) Briton et Wilson, Chenopodium album L., Alternanthera philoxeroides (Mart.) Griseb, Lemna perpusilla Torrey, Portulaca olearacea L., Chrysopogon aciculatus (Retz.) Trin and Achyranthes aspera L. respectively. Analysis of variance (ANOVA) revealed that the abundance of highly dominant species like Blumea lacera DC., Chenopodium album L., Alternanthera philoxeroides (Mart.) Griseb, Lemna perpusilla Torrey, Achyranthes aspera L. and Bryophyllum calycinum Salisb. were significantly (P<0.05) varied in different parts of the island. It can be concluded that the present study will be helpful for the planners and policy makers to plan for the better conservation and sustainable management of plant resources of Sandwip Island.