Open Journal of Forestry 2013. Vol.3, No.1, 41-48 Published Online January 2013 in SciRes (http://www.scirp.org/journal/ojf) http://dx.doi.org/10.4236/ojf.2013.31007 The Effective Ecological Factors and Vegetation at Koh Chang Island, Trat Province, Thailand Nathsuda Pumijumnong, Paramate Payomrat Faculty of Environment and Resource Studies, Mahidol University, Nakhon Pathom, Thailand Email: [email protected], [email protected] Received October 3rd, 2012; revised November 7th, 2012; accepted November 20th, 2012 This study aims to characterize the tropical rain forest present in the Chang Island, Trat Province, Thailand, and to analyze the environmental factors to determine its composition and structure. Thirty one plots were sampled, plant cover was measured in 20 × 40 m2 plots, and the importance value index was calculated. A total of 78 spe- cies belonging to 32 families were identified.Twenty soil samples were analyzed, and cluster analysis was em- ployed to classify the vegetation communities. Floristic and environmental data were evaluated and ordered us- ing canonical correspondence analysis. The results showed that the vegetation communities could be divided into 4 types and were significantly (p < 0.05) controlled by a secondary distribution according to elevation and the topographic wetness index (TWI). Mixed plant communities were more likely to distribute in regions with moderate to low levels of TWI, which were divided by levels of elevation into lowland multi-aged stands (Type 1) or a Calophyllum thorelii Pierre community (Type 2). The Dipterocarpus (Hopea pierrei Heim) community (Type 3) was more likely to occur in regions with moderate to high levels of TWI, but the result from cluster analysis showed that some of the plot samples from the Dipterocarpus community were separated by character- istic importance value index (IVI) values. There was also evidence that the area was impacted by an old distur- bance created by a rubber plantation. This impact was referred to as a secondary succession community (Type 4). Keywords: Chang Island; Vegetation Community; Canonical Correspondence Analysis; Ecological Factors Introduction century, tropical rain forest areas around the world and in Thai- land now face loss due to human activities (Royal Forest De- Chang Island is one of only a few islands where a tropical partment, 1997, 2005). Chang Island is also facing the same rain forest is distributed over 70% of the inland area, which has problem as other forest resources and is in danger of losing been preserved in its present form (Environmental Research forest cover by people focused on acquiring forest land for their Institute, 2007). The island covers an area of 212.947 sq km settlements, farms, and plantations. Recently, land use change and is a major island of the Mu Koh Chang National park in the caused by tourism had led to construction on the island, in- Gulf of Thailand, which became Thailand’s 45th National Park cluding business buildings, luxury accommodations, roads, and in 1982. During the Pleistocene epoch (Tougard, 2001; Essel- harbors. This type of land use changes the ecological system of styn et al., 2009), large sea level fluctuations caused the sea Chang Island. Although the Mu Ko Chang National Park was level to fall by 50 - 150 m, creating land bridge connections. established at the end of 1982, negative human impact on the After this period, the sea level rose and the low-lying regions vegetation had already occurred in the more accessible coastal were covered with water forming many islands separated from areas because the settled area of the old communities before the the mainland. Various fossils have confirmed these events dur- establishment of the National Park were not included in the pre- ing this period (Bird et al., 2005). The research of Chamchum- servation. Therefore, some species have become extinct, such roon and Puff provides evidence to support this theory. It is as Ixoradoli chophylla, Lasianthuso ligoneuron and L. schmid- remarkable that although a large proportion of rubiaceous taxa tii, which according to the reports of Schmidt and Kerr (Cham- show disjunction between Koh Chang and peninsular Thailand, chumroon et al., 2003; Schmidt, 1900), come from the Klong 20% of all rubiaceae taxa recorded from Koh Chang have been Nonsi area, a populated area near the Koh Chang District Of- found to be distributed in peninsular Thailand (Chamchum- fice that has no traces of natural vegetation left. None of these roon et al., 2003). This indicates that biological species found species have ever been identified anywhere else in the Island. on the mainland may also be found on the Chang islands with a The effect of climate change is another problem because the greater diversity. The tropical rain forest of Chang island has area, size, and isolation of Chang Island make it less resilient to important roles in storing bioelements and water for local com- such change. munities and acts as a carbon bank that impacts a large global This study aimed to classify the vegetation communities on area. Since 1902, the records of Schmidt (1900) have shown Chang Island and determine environmental factors that influ- that all of the hills of Koh Chang are entirely covered with the ence their composition and structure. Knowledge of these rela- densest jungle. In addition, the Siamese and Chinese popula- tionships may be critically important for planning appropriate tions scattered along the coasts where the river debouches have adaptations to climate changes and disturbances due to human had little influence on the forest cover of the hills. Over the past activities. Copyright © 2013 SciRes. 41 N. PUMIJUMNONG, P. PAYOMRAT Materials and Methods able phosphorus, and exchangeable potassium were subse- quently analyzed in these samples (Office of Science for Land Study Area Development, 2005). The study area is located at Chang Island, Trat Province, in the southeastern region of Thailand close to the border with Data Analysis Cambodia. It is located at 132˚51'57"N - 134˚51'57"N and 20˚10' 46"E - 22˚08'89"E. The total area is approximately 212.947 A species list was created to further simply identification of square kilometers. Its length from north to south is 30 kilome- species diversity. We also determined three values for each tree ters and the width is 14 kilometers. Chang Island is the largest species in a given community, including the relative density, island in Trat Province. It is close to the Cambodia border, relative frequency, and relative dominance (dominance was approximately 300 kilometers southeast of Bangkok. Ninety defined as the mean basal area per tree times the number of percent of the total area is comprised of an extrusive and intru- trees of the species) (Curtis, 1959). The diversity within a com- sive igneous rock mountain range interchanged with cliffs, munity was calculated using the Shannon-Wiener index (H) steep hills, and cliffs reaching as high as 743 m above sea level (Hill, 2007). Multivariate analyses were performed on the flo- (ASL), such as the Kao Yai Mountain. The plains along the east ristic data matrices, species, where all species whose impor- coast of the island are rich in sandy clay and the west coast is tance value was less than 5% were eliminated. Classification of rich in a recent beach deposit (Tansuwan, 2007). Small rivers plant communities was achieved using a two-way cluster ana- and streams on Chang Island are found in areas where the sea lysis on the PC-ORD program (Finch, 2005; McCune, 2002). and the creeks meet, flowing through small mangrove forests Thirty-one plots of plant communities were classified based on around the island, with the exception of a fairly large forest lo- the important value of each species in each plot sampled. Ordi- cated in a protected area on the south coast. The mountain nation was performed within PC-ORD using canonical corre- slopes are covered by dense tropical rainforest forest. The prin- sponded analysis (CCA) (McCune, 2002). CCA is a direct gra- ciple tree species include Dipterocarpus alatus, D. turbinatus, dient analysis technique that relates community variation (com- Anisoptera costata, Hopea odorata, Irvingia malayana, Podo- position and abundance) to environmental variation, thereby carpus neriifolius, Diospyros spp., Castanopsis spp., Croton providing a determination of significant relationships between spp., Oncosperma horrida, Caryotamitis., Daemonorops spp., environmental variables and community distribution (terBraak, Korthalsia grandis, Bauhinia bracteata, Freycinetia sumatrana, 1995). CCA axes were evaluated statistically using a Monte Platycerium coronarium, Amomum spp., Boesenbergia pandu- Carlo test. Four topographic variables and 11 soil properties rata, and Kaempferia pulchra (Royal Forest Department, 1997, were used in the CCA. 2005). The climate conditions are influenced by northeast and southwest Asian monsoons; the former bring dry air to Thai- land during November through April separated by short periods of cool (November-February) and hot (March-April) seasons, and the latter bring moisture from May through October and account for 90% of the annual rainfall. The mean annual rain- fall is 4902 mm and total rain fall in some years surpasses 6000 mm (2000 AD, 2006 AD). In addition, the average maximum, minimum, and mean temperatures are 31.8˚C, 23.6˚C, and 27.4˚C, respectively (Thai Meteorological Department, 2010). Field Sampling A quantitative survey of the vegetation was conducted along the entire topographic gradient of the protected area from North to South (Figure 1). A total of 31 plot samples were divided within the 4 survey lines. All samples from the plots were col- lected in year 2011. A temporary sample plot method was used in each sample plot. A quadrat of 20 × 40 m2 was set and used to investigate all tree plants higher than 1.3 m with a diameter at breast height (DBH) ≥ 4.5 cm.