The survey was conducted in the mangrove forest around the Kapa Village in Kadan Island, Myeik Coastal area, in April 2018. Transect lines in shoreline, seaward and landward, and plot based on Point Center Quarter Method (PCQM) P-DATA PRO were used. A total of 18 species of true mangroves were record. Among than 1 species in Near Threaten(NT), 1 species in Critically Endangered(CR), 2 species in Endangered(EN) considered under the IUCN red list. Rhizophora apiculata and R.mucronata are the dominant species in the area. Aegialitis rotumdifolia, Avicennia marina, Excoecaria aglocha, Heritiera littoralis, Sonneratia graffithii, Xylocarpus mucronata and Nypa fruticans are the least species in the area. Among the three study sites of Kapa, Landward zone is the most distributed of species and shoreline zone is the least distributed. The complexity index was found 2.5 to 67.3.The total forest density 0.17 to 0.39m² and mean height 3.2 to 4.7m. The mean important value of Rhizophora apiculata was heights; the Nypa frucan was least. The environmental parameters such as salinity and temperature of seawater, and temperature and pH of soils of each study site were presented.

Keywords: species composition, vegetative structure, environmental parameters, mangrove forest, myeik coastal areas, kadan island, landward, seaward, shoreline, transect lines, zonal pattern

Myanmar has a long coastline, including three coastal regions as Rakhine, the Ayeyarwady Delta and Gulf of Martaban, Tanninthayi coastal regions which is 2832km .Among the three coastal regions, Tanintharyi coastal zone is the longest coast line about 1200km in length and has the richest diversity of coastal habitats and constitutes over 800 Islands. There are estuaries, delta systems, numerous offshore islands and a considerable diversity of coastal habitats including coral reef, mangroves, sandy beaches and mudflats. In these mangroves, 46% are included in Ayeyawady, 37% in Taninthayi and 17% in Rakhine. Mangrove areas of Myanmar stand at about 8^th position in world and 3^th position in South Asia mangroves (Giesen et. al,2007).¹ Kadan Island is situated at the eastern part of Myeik coastal areas. And then, it is the biggest island in Myeik Archipelago. Today, mangrove forests are being degraded and destroyed on a larger scale globally through the natural disturbance and anthropogenic activities such as transforming to agriculture land, aquaculture ponds, salt ponds/ land etc., which are major causes of their degradation and loss of mangroves ecosystem.

The present study was conducted in the mangrove forest near the Kapa village in Kadan Island, Myeik Coastal (lat12.23427ºN, long 98.22497º E) in April 2018, Figure 1. A total of six transects line were laid the at the mangroves community of Kapa, Kadan Island Figure 1. A total of six random transects were set up based on the different forest condition (ie shoreline, seaward, landward) at the Kapa, Myeik coastal Area. The transect lines were measured by using measuring tape in meter. The distances and intervals of each transect were shown in Table 1.Totally, 15 sampling plots were set up in each transect. The measurement of plot is 10m², respectively. Each plot subdivided into four quadrants. Only one of nearest tree was recorded in each quadrant. The data of vegetation was recorded by using Point Center Quarter Method (PCQM) according to Dohdouh and Koedam (2006). Then, the variable parameters such as the stem density (De), basal area (Ba) for each species and for entire mangrove stand, the complexity index (C.I), the relative density (De_r), the relative dominance (Do_r), the relative frequency (F_r) and the importance value (I.V) for each species were calculated by using Microsoft Excel-base Workbook P-DATA-PRO_1000 (Version 5.01) software.

Figure 1 Map showing the location of the sampling area near the kappa village, katan Isand, Myeik Archepelago.

The location of start point and end point were marked by using GPS for each transects line in the study areas. The environmental parameters such as soil temperature, soil salinity, soil pH, water salinity, and water temperature were measured at the field immediately. The species identification was carried out according to the following references, Selvam et al.,^2–5 For all recorded mangrove species: flower, fruit, bud, leave, root and stem were recorded by using digital camera.

In the present study area, total of 18 species belong to 11 genera from 9family in the Kapa, Myeik Coastal Area of true woody mangrove plants was recorded. They are 5 species in Rhizophoraceae, 3 species in Avicenniaceae, 2 species in Sonneratiaceae, Meliaceae, and Sterculiaceae, 1 species in Euphorbiaceae, Myrsinaceae, Plumbaginaceae and Aracaceae at Kapa, Myeik Coastal Area. The Systamatic positions of classification of recorded species were described in Table 2.

The distribution trends of recorded species along the transects in study site was presented in Table 3 and the forest of vegetation assemblage in study site shown in Table 4. Rhizophora apiculata , R.mucronata and Sonneratia alba are most dominant species in the study sites and Aegialitis rotumdifolia ,Excoecaria aggallocha, sonneratia graffithii and Xylocarpus moluccensis are least in the study sites. And then Rhizophora apiculata and R.mucronata were distributed the near all study sites, Aegiceras corniculatum, Avcenia alba and Avicennia marina were distributed the shoreline, Aegiceras corniculatum, Avcenia alba and Bruguiera parviffora were distributed the seaward and then Avicennia officianalis, Cerops dencandra, C.tagal, Heritiera forms, H.littoralis, Sonneratia alba , S.graffithii, Xylocarpus granatum and X.moluccensis were distributed the landward.

The physiochemical studies were also conducted in the study site and the data were presented in the Table 5-6. According to the table, the average water salinity was highest 30.5‰ in shore line but the lowest water salinity 28 ‰ is the landward. The average soil salinity was highest 30.5‰ in landward but shoreline is least 28.8‰. The water temperatures range is the 27.4ºC-31.0ºC while soil temperatures range is the 26.4ºC-29.7ºC in the study sites. And then the average Soil pH is the highest in shoreline and least in seaward (Figure 2-7).

Figure 2 Species composition of mangrove in Kapa at Myeik Archipelago ,Taninthayi Coastal Area.

Figure 3 Mean basal area of mangrove species at study site.

Figure 4 Mean important value of mangrove species at study site.

Figure 5 Mean Relative Dominant of mangrove species at study site.

Figure 6 Mean Relative density of mangrove species at study site.

Figure 7 Mean Relative frequency of mangrove species at study site.

According to latitudinal different, the vegetative structure and types of mangrove formation are unique in each region. The mangrove ecosystem in the tropical regions, along coastal shorelines and associated is important for many flora and fauna. The present study was conducted at six stations which represented different mangrove types in Shoreline, Seaward and landward. The present study deals with the occurrence, composition and vegetative structure of true mangrove in Kapa, Myeik Coastal Area .

There are many previous studies in Myeik and Mawdin Coastal Area. Among them, a total of about 50 species of mangrove,⁶ the zonation of true and associate mangrove species distribution,⁷ botanical study of importance of mangrove ecosystem for conservation and Management purpose,⁸ 44 species of mangrove including true and associate species of mangroves⁹ and 30 species including true mangrove and mangrove associates¹⁰ were recorded in Myeik Coastal area. Moreover, the zonation pattern of mangrove in Magyi Tidal Creek by using transect lines method,¹¹ species composition and zonation pattern of mangrove of Kandon-kani, Amherst and Setse areas,¹² the mangrove reforestation from the Ayeyarwady Delta,¹³ The socioeconomic study of Ayeyarwady mangroves and the species composition, zonation and succession of mangrove community along the Magyi coastal area.¹⁴

In the present study, only true mangrove was recorded by using Point Center Quarter Method (PCQM). A total of 18 species of true mangrove were observed in the present study in Kapa area, Kadan Island. A total of 18 species were distributed in Kapa. Rhizophora apiculata was common in all transects. Six species of Aegiceras corniculatum, Avicennia alba, A. Marina, R. apiculata, R. mucronata and Sonneratia abal were distributed in shoreline areas whereas ten species of Aegialitis rotumdifolia, Aegiceras. corniculatum, A. officinalis, A. alba, Bruguiera parviflora, Rhizophora. apiculata, R. mucronata, Sonneria. alba, Xylocarpus granatumand Nypa fruticans were distributed in the seaward areas and then, twelve species of A . officinalis, Ceriops decandra, C. tagal, Excoecaria agallocha, Heritiera formes, H. littoralis, R. apiculata, R. mucronata, S. alba, S. graffithii, Xylocarpus granatum and X. moluccensis were found to be distributed at the landward area. So landward area was most species and shoreline area was least species.

In measuring the forest parameters, 3 types of transect were laid and recorded the nearest species, the distance of tree from the plot’s center and the circumference of selected species at all study sites. The vegetative structure of forests such as numbers of empty quadrant, number of species, proportion of multiple stem trees, mean number of stems in multiple stemmed, mean height, total forest density, total basal area, total frequency and complexity index for each transects were mentioned in Tables 4. Mean density, mean basal area, mean frequency, mean relative density, mean relative dominance, mean relative frequency, and mean importance value were shown in Table 5.

In measuring the mean relative density, Rhizophora apiculata was the highest group of plants, Nypa fruticans was least during the study period in Kapa,. Sonneria alba was the most influenced of mean relative basal area but Aegialitis rotumdifolia was the least in the study site. Mean relative frequency of Rhizophora apiculata is most influenced but Xylocarpus moluccensis and Nypa fruticans were least respectively in Kapa. And then Rhizophora apiculata was the most important species but Nypa fruticans is the least in the study sites.

In some cases, zonation may be very irregular or restricted to a particular part of the tidal gradient.¹⁵ Similarly, the zone of study sites termed as Shoreline, Seaward and landward zone. According to the zonation pattern, Rhizophoraapiculata, R. mucronata and S. alba were distributed at all zones. Aegiceras corniculatum,Aegialitis rotumdifolia, Avicennia alba, A.officinalis, Xylocarpus granatum,Bruguiera parviflora and Nypa fruticans were distributed only at the seaward and then, Avicennia officinalis, Excoecaria agallocha, Heritiera formes, H.littoralis Cerop. tagal, C. decandra, Xylocarpus moluccensis X.granatum and Nypa fruticans were at the landward from the Kapa station, Myeik Coastal Area. The structure and composition, called mangrove vegetation structure dynamics, are rarely studied worldwide. The result of present study recognized the various types of dynamics. As the calculated result, mean basal area were variable ranging (0.0 to 1.9), mean relative density ranging (1.7to 37.2), mean relative dominance ranging (1.4 to 51.8), mean relative frequency ranging (2.9 to 35.4 and mean important value ranging (8.7 to 177.6) respectively at Kapa mangrove.

The present study has been carried out in the Kapa mangrove area in Kadan Island. The study site was selected and measured the vegetative structure and recorded the species composition so as to estimate the forest value. The forest type is inner mangrove formation which based on the tidal creeks. A total of 18 true mangrove species were recorded in the study area and some general zonation pattern among the species was recognized within the study period. According to the zonation pattern, the average soil salinity of landward side is the highest but the lowest the average soil salinity is the shore line in the study area. It is note that the soil salinity and water salinity are influencing the distribution of mangrove species along transects. Evidently, landward side is showed the most distributed mangrove species along transects. According to the data, the estimation of mangrove forest can be implemented. In the study areas, most of forest is in good condition but some of the areas are not because of several human impacts and activities. Today, mangrove forests are being degraded and destroyed on a larger scale globally through the natural disturbance and anthropogenic activities such as transforming to agriculture land, aquaculture ponds, salt ponds/ land etc., which are major causes of their degradation and loss of mangroves ecosystem. Thus, it is necessary to conserve the Kapa mangrove areas in proper ways for the sustainable uses in the future.^16–18

The present study has been carried out in the Kapa mangrove area in Kanda Island . The study site was selected and measured the vegetative structure and recorded the species composition so as to estimate the forest value. The forest type is inner mangrove formation which based on the tidal creeks. A total of 18 true mangrove species were recorded in the study area and some general zonation pattern among the species was recognized within the study period. According to the zonation pattern, the average soil salinity of landward side is the highest but the lowest the average soil salinity is the shore line in the study area. It is note that the soil salinity and water salinity are influencing the distribution of mangrove species along transects. Evidently, landward side is showed the most distributed mangrove species along transects. In the study areas, most of forest is in good condition but some of the areas are not because of several human impacts and activities. Thus, it is necessary to conserve the Kapa mangrove areas in proper ways for the sustainable uses in the future.

We are greatly indebted to Dr San Tha Tun, Professor and Head, Department of Marine Science, Mawlamyine University, for his encouragement throughout the study period. We would like to acknowledge to Dr Myo Min Tun (Lecturer) for reading and preparing this manuscript. We sincerely thank Ko Aung Nge and with his local villagers for their helpful assistance in field work. The first author, Soe Win, would like to thank he beloved family for their physical, moral and financial supports throughout this study.

The author declares that there is no conflicts of interest.

None.

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