Community of Mangrove Category Tree and Sapling in The Sekotong Bay, West Lombok

*Corresponding Author: Lalu Japa, Biology Education Study Program, Faculty of Teacher Training and Education University of Mataram, Mataram Indonesia; Email: ljapa@unram.ac.id Abstract: Community of mangrove in the Bay of Sekotong, West Lombok was studied to know the species composition, individual density of each species, and percentage covering of mangrove canopy. Total 28 plots of 10 m x 10 m were set in 9 transects in 5 stations. Photographs of canopy covering and mangrove community composition were analyzed by using software ImageJ and template spreadsheet 10x10, the new version of March 2018. The community of mangrove of Sekotong bay, West Lombok consists of 8 species, 5 genera, and 4 families. Rhizophora apiculata & Rhizophora stylosa were recorded in seven of nine transects (78% of transect). Ceriops tagal was a species that was also recorded to have the highest density (3700 trees/ha) in transect SKTM02B. The average density of the mangrove sapling category was higher than the mangrove tree category. The three highest covering percentages of canopi mangrove community took place in transects SKTM01A, SKTM01B, and SKTM04T.


Introduction
Mangrove ecosystems mostly are laying down along the coastal lines of tropical and subtropical areas which are dominated by the community of mangrove. Community of mangrove adapted to grow well and normal development in habitats with high salt concentration. Naturally, the potential of Indonesia mangrove ecosystem is much higher than those of Australia and Brazil of mangrove areas (Backmann, 1994, andGiri et al., 2011).
Some mangrove forests in many parts of Indonesia, however are now in uncertain condition, even in threatening condition. One example, mangrove forest of Bintan Island is very susceptible to tantrums and threatened (Saputra et al., 2016). The areas of Sekotong Bay West Lombok has wide enough potency of mangrove forest. However, many forms of the local community activities including traditional gold mining can bring some negative effects for the mangrove community. Some activities including mangrove reclamation can threaten the condition of mangrove forests (Saputra et al., 2016). For this reason therefore, the mangrove ecosystem of Sekotong Bay West Lombok needs to be survey regularly for getting a value of healthy condition and development as some policies on management of coastal areas developed continuously rapidly. Therefore, the mangrove ecosystem with no exception, mangrove ecosystem of Sekotong Bay West Lombok should be managed very well for the existence and conservation objectives.
Results of a research can be used as based of good management for the mangrove community conservation. The results of this research can be used as the basis of materials policies in every decision in relation to management of mangrove ecosystem areas, basically in the areas of Sekotong Bay, West Lombok.

Time and Places
Data collection of mangrove community was conducted during one week period (2 nd -8 th August 2019 at nine transects in five permanen station. All stations were located in the area's two villages namely: Pelangan and Batu Putih, District of Sekotong, West Lombok. Name, coordinates, and locality of station and transects of research are given in Table 1.

Data Collection and Analyzed
Data of mangrove vegetation were obtained by using some important tools, such as: camera, GPS, tailor meter, protractor, and waterproof paper, in plot atau quadrat transect (Syafei, 1990). Total of twenty eight plots (quadrates) of 10m x 10m were laid down at nine transects in five stations. Photography hemispherical photography method was applied for data collection of Percentage covering of mangrove canopy (Dharmawan & Pramudji, 2014. Total of 164 photographs were analyzed for the health condition of the mangrove community. Diameter of the mangrove stem was measured at the position of breast high, except some trees of mangrove Ceriops tagal were measured just below the branching system (at knee high). Stems diameter of mangrove at breast high of 16 cm and above were recorded as tree category. Mangrove with diameter of stem less than 16 cm and minimal height of 1.5 m were recorded as sapling category. Data of canopy height were also determined by measuring the elevation angle from the highest shoot to the distance of 10 m from the base canopy stem using a protractor. Data of mangrove communities in both tree and sapling categories were collected and analyzed based on the method provided by Pramudji, 2014, 2017). Data for canopy covering percentage and diameter of mangrove stem were analyzed as the main parameter, reversed to Dharmawan & Pramudji (2014 using software ImageJ and a newly template spreadsheet. Furthermore, the health of the mangrove community was interpret based on the National Standard of Keputusan Menteri Lingkungan Hidup Nomor 201 tahun 2004 (Anonymous, 2004).

Results and Discussion
Total eight species from five genera, and four families of the mangrove community were fully identified ( Table 2). Distribution of mangrove species on each station and transect is given in Table  3. The important values index of each mangrove species for tree, sapling, and all categories can be seen in Figure 1. For all categories, the dominance species in each transect were Ceriops tagal in SKTM02B, Rhizophora stylosa in SKTM03B, Rhizophora mucronata in SKTM04, and Rhizophora apiculata in SKTM04T.
Species composition of the mangrove community for the tree category in the Sekotong bay was less and/or more than mangrove communities in other areas of Indonesia.   The highest and lowest density for mangrove tree category was recorded in trnasex SKTM02B and SKTM01B, 4467 ind./ha and 2400 ind./ha, respectively. Mangrove for sapling category, the highest density (9933 ind./ha) was recorded in transex SKTM03A, and the lowest density (1050 ind./ha) occurred in transex SKTM01B. Density comperation of mangrove tree and sapling category are provided in Figure 2. The average density of the mangrove sapling category is much higher than the density of the mangrove tree category. Density of sapling was much higher than the tree in transects SKTM03A, SKTM03B, and SKTM05. However, in transects SKTM01A, SKTM01B, SKTM04. density of sapling was lower than tree, and similar in transex SKTM04T.

Figure 2. Density proportion of Mangrove Tree and Sapling Categories
Distribution and authority of transects numbers for each species of eight species of mangrove identified were various enough, in the range of one to seven (11-78%) (Figure 3). Rhizophora apiculata was the only one species which has the highest percentage of area authority (78%). The other seven species have the percentage of area authority less than 60%, and two species with the lowest percentage of area authority (11%) were Lumnitzera ceramosa and Sonneratia alba.  The highest average high of mangrove tree category (8,20±0,11 m) occurred in transect SKTM04, and the lowest average high (3,43±0,17 m) was recorded in transect SKTM02B. The dominant of Ceriops tagal in SKTM02B can be the main reason for the lowest average high of mangrove tree category in this transect. The biggest stem diameter of mangrove tree category was 10,57 cm recorded at transect SKTM04, and the smallest tree diameter (6,10 cm) recorded at transect k SKTM03A. The biggest diameter (10,57 cm) of mangrove tree in the Sekotong Bay is much smaller compared the diameter of naturally mangrove tree of the District of Wondama-Papua (Dharmawan & Widyastuti, 2017). The high and diameter comparison of mangrove tree among transects are given in Figure 4.

Conclusion
Community of mangrove forest in Sekotong Bay, West Lombok consists of eight species from five genera and four families. Based on the average density and percentage coverage of mangrove canopy, the community of mangrove was in good to very good categories. Rhizophora apiculata and Rhizophora stylosa were the two species of mangrove with the highest distribution reached 78% station and transects of research. Density of mangrove tree category almost always higher than sapling in all transects, except in transect SKTM01B. Three station with highest species diversity index were SKTM02, SKTM04, & SKTM05.

Acknowledgement
Thanks to COREMAP-CTI-P2OLIPI for supporting funding. Thanks also goes to Dr. H. Imam Bachtiar, M.Sc., as a team coordinator for preparing and providing all logistics, accommodation, transportation, consumption, and kindness giving all information always in early time. Supporting and friendly coordination and communication among the team members during preparation and in the field activities were also appreciated. Thanks so much also goes to all members of the mangrove team for hard work and funny communication during the field activity.