Diversity of Plant community in Satun Geopark

Abstract

Background and Objectives: The diversity of species and plant communities varies among the areas. Understanding of species and their habitats is vital on conservation and sustainable natural management under the anthropogenic disturbances. This study aimed to detect the types of plant communities and plant species diversity of each community that existed within the Satun Geopark, Satun province, including the comparison analysis of the similarity between found plant communities, as well as examine the conservation status of plant species that appear in the sample plots. The result provides important information that can be used in considering the conservation of plant resources in the Satun Geopark and others.

Methodology: Plant communities are classified into different types based on the physiognomic of the plant communities following Smitinand (1977). The temporary plot size of 20 m x 50 m, total 17 sample plots, were set up and covered all the classified plant communities. Each plot measured the trees at DBH > 3.5 cm and also tree identified was done. Analyses were made of the importance value index of tree species. The diversity index of each plant community was analyzed, as was the similarity index between communities. All founded tree species were examined using the IUCN Red List Categories and Criteria.

Main Result: The results showed the plant communities in Satun Geopark can be classified into                         9 communities: 1) Moist evergreen forest (MEF) inhabits on deep soil, the dominant species are in the family of Dipteroccarpaceae, Fabaceae, Moraceae, Malvaceae, and Annonaceae. 2) Dry evergreen forest (DEF) inhabits limestone mountains. The structure is a mixture of deciduous and evergreen tree species. The dominant species are in family of Dipteroccarpaceae, Fabaceae, Annonaceae, Ebenaceae, and Melastomaceae. 3) Semi-arid evergreen forest (SEF), the structure of the community is a mixture of moist evergreen forest and some dry evergreen forest trees. The dominant species are in family of Dipteroccarpaceae, Fabaceae, Annonaceae, Ebenaceae, and Myrtaceae. 4) Mixed deciduous forest (MDF) found on limestone mountains. The structure of the community consists mainly of deciduous trees mixed with some evergreen trees. In some areas, bamboo is dominated at understory plant. The prominent plants are Malvaceae, Dipterocarpaceae. Annonaceae, Combretaceae, Lythraceae, and Phyllanthaceae. 5) Mixed deciduous forest with Pentacme siamensis dominant is found in limestone mountain areas with very shallow soil layers. The dominant trees in the canopy layer are Dipterocapaceae (Pentacme siamensis) and some other family such as Moraceae and Combretaceae. 6) Limestone scrub forest (LSF) is found in the limestone mountain areas or limestone cliffs where there is a lack of soil layer. The prominent trees include family of Malvaceae, Combretaceae, Lythraceae, Lamiaceae, and Phyllanthaceae. 7) Beach forest (BF) community is found on sandy beaches and along sand dunes. The dominant plants are the family of Fabaceae, Malvaceae, Myrtaceae, Casuarinaceae, and Baringtoniaceae. 8) Mangrove forest (MF) consists of vegetation structures in zones, starting from the group close to the water's edge to the group close to the terrestrial forest. The dominant plant species include the family of Rhizophoraceae, Malvaceae, Meliaceae, Acanthaceae, and Euphorbiaceae. And, 9) Dwarf mangrove forest (DMF) is found in sinkholes that occur on islands. The plant species that appear are similar to those in general mangrove forests, but it consists of small and stunted trunks. The canopy is only one layer and 5-6 meters high. The diversity index values based on Shannon-Weiner (H^/) in the moist evergreen forest of all study sites (Phu Pha Phet Forest Protection Unit, Ko Tarutao, and Ko Rawi) had higher diversity (H^/=3.28-3.38) than other forest types, MEF in the sinkhole (H^/=2.83), SEF (H^/=2.83), DEF at Ko Khaoyai (H^/=2.99) and Khao To Ngai (H^/=2.64), respectively. The MEF in the sinkhole has a diversity index value close to that of the SEF. While, the diversity index values in the BF of Ko Tarutao and Ko Rawi were low (H^/=2.07 and 2.16, respectively), in addition almost closed to the LSF (H^/=2.24). However, the MF diversity index showed the lowest values for all study sites (Ko Tarutao, Tha Oi, Rawai and MF in sinkhole) which H^/ ranged from 0.86-1.40. The diversity index value in limestone scrub forest is 2.24. Indicating low species and evenness was detected when compared to other forests. Concerning similarity between plant communities, two main category types were divided, deciduous and evergreen forests, and similarity index was analyzed for each group, The similarity index of mixed deciduous forest groups is more than 60%. Therefore, it’s implied that the mixed deciduous forest in Satun Geopark have similar plant species. The similarity index of the evergreen forest group showed all areas are less than 40%, indicating that all plant communities have differences in plant species. The conservation status of plant species that are components of the plant community by IUCN Red list of Threatened species found that only one species is endangered (Endangered: EN), which is Hopea ferrea, and there are 6 species with a vulnerable (Vulnerable: VU) status, which are: Cinnamomum ilicioides, Mitrephora alba, Payena lucida, Parashorea stellata, Garcinia costata, and Monoon cupulare. The other species found in the study areas were mostly of Least Concern (LC), indicating that their populations are still large enough to not be at risk of extinction.

Conclusion: There are 9 plant communities were found that the MEF have the highest diversity index value than the other communities, followed by the MEF in the sinkhole area, SEF, DEF, LSF, BF, and MF had the lowest than the other types. The similarity between forests in the deciduous forests had higher than 60%, while in the evergreen forests were less than 40%, indicating that in the evergreen forest, although the physical characteristics are similar, the plant species that make up the community are still different. As for the conservation status of plant species, it was found that most of them have a status of least concern (LC), and only one species is endangered (Endangered: EN), which shows that the H. ferrea is at risk of extinction from nature in the future if the threatening factors continue. Thus, our findings on species establishment within specific habitats may be useful for conservation and sustainable management planning on species diversity, in particular, other effective area-based conservation measures, OECMs.