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

Noor Hassan Sajib*
Department of Environment, Comilla District Office, Housing Estate, Comilla, Bangladesh

Shaikh Bokhtear Uddin
Department of Botany, University of Chittagong, Chittagong 4331, Bangladesh

M Shafiqul Islam
Institute of Marine Sciences and Fisheries, University of Chittagong, Chittagong 4331, Bangladesh

Abstract/ Executive Summary:

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 planners and policymakers to plan for the better conservation and sustainable management of plant resources of Sandwip Island.

Keywords: Vascular Plant; Diversity; Distribution; Primer (V.6); Sandwip

Location: Sandwip Island, Chittagong, Bangladesh

Start Date: 00-03-2011

End Date: 00-12-2012

Program Area: Conservation and Biodiversity

Commodity: Plant

Objectives:

There is very limited information on the vascular plant diversity and their distribution pattern in the islands of Bangladesh. Species identification, inventories and a better understanding of tropical environments also play an essential role in the exploitation of natural resources and to control the global climate change of a region. But no such work was carried out so far for Sandwip Island. The present investigation has been undertaken for the investigation of vascular plant diversity and their distribution pattern in the study area.

Methodology:

The plant specimens were collected, identified and documented through ten field trips during March 2011 to December 2012. The plant samples were collected from 48 quadrats following random quadrat method. Each of the quadrat was (5m × 5m) in size. For the quantitative analysis the total study area were divided into 48 sites under four blocks through random selection. Each block was further divided into twelve sites. viz. Block-A including Magdhara, Haramia, Maitbhanga area; Block-B including Musapur, Sarikait, Rahmatpur, Azimpur area; Block-C including Gachua, Bauria, Harispur area and Block-D including Kalapania, Amanullah, Santoshpur, Dirghapar, Urirchar area.

Voucher specimens were preserved in the Chittagong University Herbarium (CTGUH). The plant specimens were examined and studied carefully in the taxonomic laboratory of CTGUH by using microscope and hand lens. Collected specimens were confirmed by comparing with herbarium specimens of CTGUH and Bangladesh National Herbarium (BNH), Dhaka. In some cases, standard literatures were consulted for identification purposes. On Alternanthera philoxeroides, Lemna perpusilla, Portulaca olearacea, Chrysopogon aciculatus and Achyranthes aspera respectively. Cluster analysis of twenty highly dominant species was done on the basis of their abundance data recorded from different sites of the study area. From the cluster it was found that the highly abundant species like Centella asiatica and Clinogyne dichotoma grouped together whereas moderately abundant species Chenopodium album and Desmodium triflorum formed another cluster.

The plant species showing significant difference (P<0.05) are Blumea lacera DC., Chenopodium album L., Alternanthera philoxeroides (Mart.) Griseb, Lemna perpusilla Torrey, Achyranthes aspera L. and Bryophyllum calycinum Salisb. Details results of ANOVA were presented in Table 2 is the abundance of highly dominant species found in the study area.

Magnoliophyta represents higher number of species and individuals from Pteridophyta in the present study. Pteridophyta the other hand, world wide website are considered for the recent nomenclature of all specimens.

Abundance (individuals/25 m²) of each species was calculated for each block. Various diversity indices (Shannon-Wiener diversity index, species richness or Margalef’s index and Pielou’s evenness index) were measured from the abundance data by using PRIMER v6 software program. Highly abundant or dominant species observed in different blocks were measured by using SIMPER of PRIMER v6 program. Significant variations in the abundance of highly dominant species were tested by using ANOVA from SPSS program.

Source of Information: Bangladesh. J Biodivers Manage Forestry 5:2. Volume 5 • Issue 2 • 1000159 • Page 2 of 5 • d

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The findings of the current work are most likely the first recorded vascular plant diversity of the Sandwip island. The present study will be helpful for the planners and policymakers of the country for the better conservation and sustainable management plan of plant represents small number of species because older parts of the island is decreasing day by day from the bank erosion and lack of suitable habitat. The total numbers of species and individuals have been unfairly distributed in Block-A, Block-B, Block-C and Block-D. Species richness is highest in Block C because the forest of the area is older than others and only few parts of the area are affected by bank erosion. In other sense, species richness is lowest in Block B of the island because most parts of the area are affected by continuous bank erosion. Block D or North parts of the island shows moderately higher species richness than Block A or southeast parts. The area of Block D is comparatively younger than others. Porteresia coarctata is characteristic plant of the newly arises land. Discriminator species represent the characteristics of the area for growing plants.

The first cluster Block A is closest to the second largest cluster Block B and second cluster is closest to the third largest cluster Block C. Dissimilarities of species have been found in different areas of the island whereas Block B and D show the highest dissimilarities among the blocks. According to the Cluster analysis of twenty highly dominant species, first cluster of Chrysopogon aciculatus, Lemna perpusila and Spirodela polyrhiza is the closest to the second cluster of Bryophylum calycinum, Ottochloa nodosa, Achyranthes aspera and Brassica napus respectively. The plant species showing significant difference (P<0.05) are Blumea lacera DC., Chenopodium album L., Alternanthera philoxeroides (Mart.) Griseb, Lemna perpusilla Torrey, Achyranthes aspera L. and Bryophyllum resources of the Island. Drought, salinity, anthropological activities and continuous bank erosion in the sea are the main threats for the vascular plants of the island. Information on diversity and distribution of plant species (except invasive alien species) of the island will help to conserve or further restoration of the island flora. To maintenance and save the environment, there is need more attention to protect the Island plant diversity.

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